United States Air and Radiation EPA420-D-01-004
Environmental Protection September 2001
Agency
&EPA Draft Regulatory
Support Document:
Control of Emissions from
Unregulated Nonroad
Engines
y&o Printed on Recycled
Paper
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EPA420-D-01-004
September 2001
of
Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
This technical report does not necessarily represent final EPA decisions or positions.
It is intended to present technical analysis of issues using data that are currently available.
The purpose in the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical developments which
may form the basis for a final EPA decision, position, or regulatory action.
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Table of Contents
Executive Summary
CHAPTER 1: Health and Welfare Concerns
1.1 Ozone 1-1
1.1.1 General Background 1-1
1.1.2 Health and Welfare Effects of Ozone and Its Precursors 1-2
1.1.3 Additional Health and Welfare Effects of NOx Emissions 1-3
1.1.4 Ozone Nonattainment 1-4
1.1.5 Public Health and Welfare Concerns from Prolonged and Repeated
Exposures to Ozone 1-7
1.2 Carbon Monoxide 1-8
1.2.1 General Background 1-8
1.2.2 Health Effects of CO 1-9
1.2.3 CO Nonattaiment 1-9
1.3 Paniculate Matter 1-11
1.3.1 General Background 1-11
1.3.2 Health and Welfare Effects of PM 1-13
1.3.3 PM Nonattainment 1-14
1.4 Gaseous Air Toxics 1-17
1.4.1 Benzene 1-18
1.4.2 1,3-Butadiene 1-19
1.4.3 Formaldehyde 1-19
1.4.4 Acetaldehyde 1-20
1.4.5 Acrolein 1-21
1.5 Inventory Contributions 1-21
1.5.1 Inventory Contribution 1-21
1.5.2 Inventory Impacts on a Per Vehicle Basis 1-24
1.6 Other Adverse Public Health and Welfare Effects Associated with Nonroad
Engines and Vehicles 1-25
1.6.1 Snowmobiles 1-25
1.6.2 Large SI Engines 1-33
1.6.3 Acid Deposition 1-34
1.6.4 Eutrophication and Nitrification 1-35
CHAPTER 2: Industry Characterization
2.1 Marine 2-1
2.1.1 Marine Diesel Engine Manufacturers 2-1
2.1.2 Recreational Boat Builders 2-3
2.2 Large Industrial SI Equipment 2-4
2.2.1 Manufacturers 2-4
2.2.2 Applications 2-5
2.2.3 Engine Design and Operation 2-8
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2.2.4 Customer Concerns 2-9
2.3 Snowmobiles 2-10
2.3.1 Manufacturers 2-10
2.3.2 Sales and Fleet Size 2-10
2.3.3 Usage 2-11
2.3.4 Customer Concerns 2-12
2.4 All-Terrain Vehicles 2-12
2.4.1 Manufacturers 2-13
2.4.2 Applications 2-15
2.4.3 Engine Design and Operation 2-15
2.5 Off-Highway Motorcycles 2-16
2.5.1 Manufacturers 2-17
2.5.2 Applications 2-20
2.5.3 Engine Design and Operation 2-21
CHAPTERS: Technology
3.1 Introduction to Spark-Ignition Engine Technology 3-1
3.1.1 Four-Stroke Engines 3-1
3.1.2 Two-Stroke Engines 3-2
3.1.3 Engine Calibration 3-3
3.2 Exhaust Emissions and Control Technologies 3-6
3.2.1 Current Two-Stroke Engines 3-6
3.2.2 Clean Two-Stroke Technologies 3-10
3.2.3 Current Four-Stroke Engines 3-15
3.2.4 Clean Four-Stroke Technologies 3-16
3.2.5 Advanced Emission Controls 3-19
3.3 Evaporative Emissions 3-22
3.3.1 Sources of Evaporative Emissions 3-22
3.3.2 Evaporative Emission Controls 3-24
3.4 CI Recreational Marine Engines 3-27
3.4.1 Background on Emissions Formation from Diesel Engines 3-27
3.4.2 Marinization Process 3-28
3.4.3 General Description of Technology for Recreational Marine Diesel Engines
3-30
CHAPTER 4: Feasibility of Proposed Standards
4.1 CI Recreational Marine 4-1
4.1.1 Baseline Technology for CI Recreational Marine Engines 4-1
4.1.2 Anticipated Technology for CI Recreational Marine Engines 4-3
4.1.3 Emission Measurement Procedures for CI Recreational Marine Engines 4-4
4.1.4 Impacts on Noise, Energy, and Safely 4-12
4.2 Large Industrial SI Engines 4-14
4.2.1 Proposed 2004 Standards 4-14
4.2.2 Proposed 2007 Standards 4-14
4.2.3 Impacts on Noise, Energy, and Safely 4-37
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4.3 Snowmobiles 4-38
4.3.1 Baseline Technology and Emissions 4-38
4.3.2 Potentially Available Snowmobile Technologies 4-38
4.3.3 Test Procedure 4-41
4.3.4 Impacts on Noise, Energy, and Safely 4-42
4.3.5 Conclusion 4-42
4.4 All-Terrain Vehicles 4-45
4.4.1 Baseline Technology and Emissions 4-45
4.4.2 Potentially Available ATV Technologies 4-47
4.4.3 Test Procedure 4-54
4.4.4 Impacts on Noise, Energy, and Safety 4-55
4.4.5 Conclusion 4-56
4.7 Off-Highway Motorcycles 4-57
4.7.1 Baseline Technology and Emissions 4-57
4.7.2 Potentially Available Off-Highway Motorcycle Technologies 4-59
4.7.3 Test Procedure 4-61
4.7.4 Impacts on Noise, Energy, and Safely 4-62
4.7.5 Conclusion 4-63
CHAPTER 5: Estimated Costs
5.1 Methodology 5-1
5.2 Cost of Emission Controls by Engine/Vehicle Type 5-3
5.2.1 Recreational Marine Diesel Engines 5-3
5.2.2 Large Industrial Spark-Ignition Engines 5-8
5.2.3 Recreational Vehicles 5-19
CHAPTER 6: Emissions Inventory
6.1 Methodology 6-1
6.1.1 Off-highway Exhaust Emissions 6-1
6.1.2 Off-highway Evaporative Emissions 6-3
6.2 Effect of Emission Controls by Engine/Vehicle Type 6-5
6.2.1 Compression-Ignition Recreational Marine 6-5
6.2.2 Large Spark-Ignition Equipment 6-11
6.2.3 Snowmobiles 6-24
6.2.4 All-Terrain Vehicles 6-28
6.2.5 Off-highway Motorcycles 6-35
CHAPTER 7 Cost Per Ton
7.1 Cost Per Ton by Engine Type 7-1
7.1.1 Introduction 7-1
7.1.2 Compression-Ignition Recreational Marine 7-1
7.1.3 Large Industrial SI Equipment 7-3
7.1.4 Recreational Vehicles 7-7
7.2 Cost Per Ton for Other Mobile Source Control Programs 7-11
7.3 20-Year Cost and Benefit Analysis 7-12
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CHAPTER 8: Initial Regulatory Flexibility Analysis
8.1 Requirements of the Regulatory Flexibility Act 8-1
8.2 Description of Affected Entities 8-2
8.2.1 Recreational Vehicles (off-highway motorcycles, ATVs, and snowmobildŁ)2
8.2.2 Marine Vessels 8-3
8.2.3 Large Spark Ignition Engines 8-3
8.3 Projected Costs of the Proposed Program 8-4
8.4 Projected Reporting, Recordkeeping, and Other Compliance Requirements of the
Proposed Rule 8-4
8.5 Other Related Federal Rules 8-4
8.6 Regulatory Alternatives 8-4
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Executive Summary
Executive Summary
EPA is proposing new standards for emissions of oxides of nitrogen, hydrocarbons, and
carbon monoxide from several categories of engines. This Draft Regulatory Support Document
provides technical, economic, and environmental analyses of the proposed emission standards for
the affected engines. The anticipated emission reductions would translate into significant, long-
term improvements in air quality in many areas of the U.S. Overall, the proposed requirements
would dramatically reduce individual exposure to dangerous pollutants and provide much needed
assistance to states and regions facing ozone and particulate air quality problems that are causing
a range of adverse health effects, especially in terms of respiratory impairment and related
illnesses.
Chapter 1 reviews information related to the health and welfare effects of the pollutants
of concern. Chapter 2 contains an overview of the affected manufacturers, including some
description of the range of engines involved and their place in the market. Chapter 3 covers a
broad description of engine technologies, including a wide variety of approaches to reducing
emissions. Chapter 4 summarizes the available information supporting the specific standards we
are proposing, providing a technical justification for the feasibility of the standards. Chapter 5
applies cost estimates to the projected technologies. Chapter 6 presents the calculated
contribution of these engines to the nationwide emission inventory with and without the
proposed standards. Chapter 7 compares the costs and the emission reductions for an estimate of
the cost-effectiveness of the rulemaking.
There are five sets of engines and vehicles that would be covered by the proposed
standards. The following paragraphs describe the different types of engines and vehicles and the
standards that apply.
Proposed Emission Standards
Large industrial spark-ignition engines
These are spark-ignition nonroad engines rated over 19 kW used in commercial
applications. These include engines used in forklifts, electric generators, airport ground service
equipment, and a variety of other construction, farm, and industrial equipment. Many Large SI
engines, such as those used in farm and construction equipment, are operated outdoors,
predominantly during warmer weather and often in or near heavily populated urban areas where
they contribute to ozone formation and ambient CO and PM levels. These engines are also often
operated in factories, warehouses, and large retail outlets throughout the year, where they
contribute to high exposure levels to personnel who work with or near this equipment as well as
to ozone formation and ambient CO and PM levels. For the purpose of this proposal, we are
calling these "Large SI engines." Table 1 shows the proposed emission standards for Large SI
engines. This includes alternate emission standards for lower NOx emissions and higher CO
emissions for engines that don't operate in enclosed areas. The table also distinguishes between
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Draft Regulatory Support Document
standards for duty-cycle testing and for field-testing.
Table 1
Proposed Emission Standards for Large SI Engines (g/kW-hr)
Model Year
Testing Type
Emission
standards
Alternate emission
standards
HC+NOx
CO
HC+NOx
CO
2004 - 2006
2007 and
later
Duty-cycle testing
Duty-cycle testing
Field-testing
4.0
3.4
4.7
37.0 —
3.4 1.3
5.0 1.8
—
27
41
Nonroad recreational engines and vehicles
These are spark-ignition nonroad engines used primarily in recreational applications.
These include off-highway motorcycles, all-terrain-vehicles (ATVs), and snowmobiles. Some of
these engines, particularly those used on ATVs, are increasingly used for commercial purposes
within urban areas, especially for hauling loads and other utility purposes. These vehicles are
typically used in suburban and rural areas, where they can contribute to ozone formation and
ambient CO and PM levels. They can also contribute to regional haze problems in our national
and state parks. Table 2 shows the proposed emission standards that apply to recreational
vehicles.
11
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Executive Summary
Table 2
Recreational Vehicle Exhaust Emission Standards
Vehicle
Model Year
Snowmobile
2006
2010
Off-highway
Motorcycle
ATV
2006
2007 and later
2006
2007 and 2008
2009
20 10 and later
Emission standards
HC
g/kW-hr
100
75
CO
g/kW-hr
275
200
HC+NOx
g/km
2.0
2.0
2.0
2.0
1.0
1.0
CO
g/km
25.0
25.0
25.0
25.0
25.0
25.0
Phase-in
100%
100%
50%
100%
50%
100%
50%
100%
Recreational marine diesel engines
These are marine diesel engines used on recreational vessels such as yachts, cruisers, and
other types of pleasure craft. Recreational marine engines are primarily used in warm weather
and therefore contribute to ozone formation PM levels, especially in marinas, which are often
located in nonattainment areas.
in
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Draft Regulatory Support Document
Table 3
Proposed Recreational Marine Diesel Emission Limits and Implementation Dates
Sub category
power > 37 kW
0.5 < disp<0.9
0.9 < disp< 1.2
1.2 < disp<2.5
2.5 < disp
Implementation
Date
2007
2006
2006
2009
HC+NOx
g/kW-hr
7.5
7.2
7.2
7.2
PM
g/kW-hr
0.40
0.30
0.20
0.20
CO
g/kW-hr
5.0
5.0
5.0
5.0
Projected Impacts
The following paragraphs and tables summarize the projected emission reductions and
costs associated with the proposed emission standards. See the detailed analysis later in this
document for further discussion of these estimates.
Table 6 contains the projected emissions from the engines subject to this proposal.
Projected figures compare the estimated emission levels with and without the proposed emission
standards for 2020.
Table 6
2020 Projected Emissions Inventories (thousand short tons)
Category
Industrial SI
>19kW
Snowmobiles
ATVs
Off-highway
motorcycles
Recreational
Marine diesel*
Total
Exhaust CO
base
case
2,991
609
4,589
208
6
8,404
with
proposed
standards
231
227
3,041
154
6
3,658
percent
reduction
92
63
34
26
0
56
Exhaust NOx
base
case
486
2
25
1
39
552
with
proposed
standards
77
2
25
1
32
137
percent
reduction
84
0
0
0
17
75
Exhaust HC**
base
case
346
229
1,301
154
1.3
2,032
with
proposed
standards
50
85
205
77
1.0
418
percent
reduction
86
63
84
50
25
79
* We also anticipate a 6 percent reduction in direct PM from a baseline of inventory of 1,470 tons in 2020 to a control
inventory of 1,390 tons.
** The Industrial SI >19 kW estimate includes both exhaust and evaporative emissions.
IV
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Executive Summary
Table 7 summarizes the projected costs to meet the proposed emission standards. This is
our best estimate of the cost associated with adopting new technologies to meet the proposed
emission standards. The analysis also considers total operating costs, including maintenance and
fuel consumption. In many cases, the fuel savings from new technology are greater than the cost
to upgrade the engines. All costs are presented in 2001 dollars.
Table 7
Estimated Average Cost Impacts of Proposed Emission Standards
Engine Type
Large SI
Large SI
Snowmobiles
Snowmobiles
ATVs
ATVs
Off -highway motorcycles
Marine diesel
Standard
2004
2007
2006
2010
2006
2009
2006
2006
Increased Production
Cost per Engine*
$600
$45
$55
$216
$60
$52
$151
$443
Lifetime Operating
Costs per Engine (NPV)
$-3,985
—
—
$-509
$-102
—
$-98
—
*The estimated long-term costs decrease by about 35 percent. Costs presented for
second-phase standards for Large SI, and ATVs are incremental to the first-phase
standards.
We also calculated the cost per ton of emission reductions for the proposed standards.
For snowmobiles, this calculation is on the basis of CO emissions. For all other engines, we
attributed the entire cost of the proposed program to the control of ozone precursor emissions
(HC or NOx or both). A separate calculation could apply to reduced CO or PM emissions in
some cases. Assigning the full compliance costs to a narrow emissions basis leads to cost-per-
ton values that underestimate of the value of the proposed program.
Table 8 presents the discounted cost-per-ton estimates for the various engines (factoring
in the effect of reduced operating costs). Reduced operating costs more than offset the increased
cost of producing the cleaner engines for Large SI and ATV engines. The overall fuel savings
associated with the proposal are greater than the total projected costs to comply with the
proposed emission standards.
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Draft Regulatory Support Document
Table 8
Estimated Cost-per-Ton of the Proposed Emission Standards
Engine Type
Large SI
(Composite of all fuels)
Large SI
(Composite of all fuels)
Snowmobiles
Snowmobiles
ATVs
ATVs
Off-highway motorcycles
Marine diesel
Aggregate
Standard
2004
2007
2006
2010
2006
2009
2006
2006
—
Discounted
Reductions
per Engine
(short tons)*
3.14
0.56
1.18
0.32
0.88
0.09
0.37
0.68
—
Discounted Cost per Ton
ofHC+NOx
Without
Fuel Savings
$220
$80
—
—
$70
$550
$310
$580
$140
With
Fuel Savings
$0
$80
—
—
$0
$550
$110
$580
$0
Discounted Cost per Ton
of CO
Without
Fuel Savings
—
—
$50
$670
—
—
—
—
$100
With
Fuel Savings
—
—
$50
$0
—
—
—
—
$0
* HC+NOx reductions, except snowmobiles which are CO reductions.
VI
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Executive Summary
Vll
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Chapter 1: Health and Welfare Concerns
CHAPTER 1: Health and Welfare Concerns
The engines and vehicles that would be subject to the proposed standards generate
emissions of HC, CO, PM and air toxics that contribute to ozone and CO nonattainment as well
as adverse health effects associated with ambient concentrations of PM and air toxics. Elevated
emissions from those recreational vehicles that operate in national parks (e.g., snowmobiles)
contribute to visibility impairment. This section summarizes the general health effects of these
substances. In it, we present information about these health and environmental effects, air
quality modeling results, and inventory estimates pre- and post-control.
1.1 Ozone
1.1.1 General Background
Ground-level ozone, the main ingredient in smog, is formed by complex chemical
reactions of volatile organic compounds (VOC) and NOx in the presence of heat and sunlight.
Ozone forms readily in the lower atmosphere, usually during hot summer weather. Volatile
organic compounds are emitted from a variety of sources, including motor vehicles, chemical
plants, refineries, factories, consumer and commercial products, and other industrial sources.
Volatile organic compounds also are emitted by natural sources such as vegetation. Oxides of
nitrogen are emitted largely from motor vehicles, off-highway equipment, power plants, and
other sources of combustion. Hydrocarbons (HC) are a large subset of VOC, and to reduce
mobile source VOC levels we set maximum emissions limits for hydrocarbon as well as
particulate matter emissions.
The science of ozone formation, transport, and accumulation is complex. Ground-level
ozone is produced and destroyed in a cyclical set of chemical reactions involving NOx, VOC,
heat, and sunlight.1 As a result, differences in weather patterns, as well as NOx and VOC levels,
contribute to daily, seasonal, and yearly differences in ozone concentrations and differences from
city to city. Many of the chemical reactions that are part of the ozone-forming cycle are sensitive
to temperature and sunlight. When ambient temperatures and sunlight levels remain high for
several days and the air is relatively stagnant, ozone and its precursors can build up, resulting in
higher ambient ozone levels than typically would occur on a single high temperature day.
Further complicating matters, ozone also can be transported into an area from pollution sources
found hundreds of miles upwind, resulting in elevated ozone levels even in areas with low local
VOC or NOx emissions.
On the chemical level, NOx and VOC are the principal precursors to ozone formation.
The highest levels of ozone are produced when both VOC and NOx emissions are present in
significant quantities on clear summer days. Relatively small amounts of NOx enable ozone to
form rapidly when VOC levels are relatively high, but ozone production is quickly limited by
removal of the NOx. Under these conditions, NOx reductions are highly effective in reducing
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Draft Regulatory Support Document
ozone while VOC reductions have little effect. Such conditions are called "NOx limited."
Because the contribution of VOC emissions from biogenic (natural) sources to local ambient
ozone concentrations can be significant, even some areas where man-made VOC emissions are
relatively low can be NOx limited.
When NOx levels are relatively high and VOC levels relatively low, NOx forms
inorganic nitrates but relatively little ozone. Such conditions are called "VOC limited." Under
these conditions, VOC reductions are effective in reducing ozone, but NOx reductions can
actually increase local ozone under certain circumstances. Even in VOC limited urban areas,
NOx reductions are not expected to increase ozone levels if the NOx reductions are sufficiently
large.
Rural areas are almost always NOx limited, due to the relatively large amounts of
biogenic VOC emissions in such areas. Urban areas can be either VOC or NOx limited, or a
mixture of both.
Ozone concentrations in an area also can be lowered by the reaction of nitric oxide with
ozone, forming nitrogen dioxide (NO2); as the air moves downwind and the cycle continues, the
NO2 forms additional ozone. The importance of this reaction depends, in part, on the relative
concentrations of NOx, VOC, and ozone, all of which change with time and location.
1.1.2 Health and Welfare Effects of Ozone and Its Precursors
Based on a large number of recent studies, EPA has identified several key health effects
caused when people are exposed to levels of ozone found today in many areas of the country.2'3
Short-term exposures (1-3 hours) to high ambient ozone concentrations have been linked to
increased hospital admissions and emergency room visits for respiratory problems. For example,
studies conducted in the northeastern U.S. and Canada show that ozone air pollution is associated
with 10-20 percent of all of the summertime respiratory-related hospital admissions. Repeated
exposure to ozone can make people more susceptible to respiratory infection and lung
inflammation and can aggravate preexisting respiratory diseases, such as asthma. Prolonged (6
to 8 hours), repeated exposure to ozone can cause inflammation of the lung, impairment of lung
defense mechanisms, and possibly irreversible changes in lung structure, which over time could
lead to premature aging of the lungs and/or chronic respiratory illnesses such as emphysema and
chronic bronchitis.
Children and outdoor workers are most at risk from ozone exposure because they
typically are active outside during the summer when ozone levels are highest. For example,
summer camp studies in the eastern U.S. and southeastern Canada have reported significant
reductions in lung function in children who are active outdoors. Further, children are more at
risk than adults from ozone exposure because their respiratory systems are still developing.
Adults who are outdoors and are moderately active during the summer months, such as
construction workers and other outdoor workers, also are among those most at risk. These
individuals, as well as people with respiratory illnesses such as asthma, especially asthmatic
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Chapter 1: Health and Welfare Concerns
children, can experience reduced lung function and increased respiratory symptoms, such as
chest pain and cough, when exposed to relatively low ozone levels during prolonged periods of
moderate exertion.
Evidence also exists of a possible relationship between daily increases in ozone levels
and increases in daily mortality levels. While the magnitude of this relationship is too uncertain
to allow for direct quantification, the full body of evidence indicates the possibility of a positive
relationship between ozone exposure and premature mortality.
In addition to human health effects, ozone adversely affects crop yield, vegetation and
forest growth, and the durability of materials. Because ground-level ozone interferes with the
ability of a plant to produce and store food, plants become more susceptible to disease, insect
attack, harsh weather and other environmental stresses. Ozone causes noticeable foliage damage
in many crops, trees, and ornamental plants (i.e., grass, flowers, shrubs) and causes reduced
growth in plants. Studies indicate that current ambient levels of ozone are responsible for
damage to forests and ecosystems (including habitat for native animal species). Ozone
chemically attacks elastomers (natural rubber and certain synthetic polymers), textile fibers and
dyes, and, to a lesser extent, paints. For example, elastomers become brittle and crack, and dyes
fade after exposure to ozone.
Volatile organic compounds emissions are detrimental not only for their role in forming
ozone, but also for their role as air toxics. Some VOCs emitted from motor vehicles are toxic
compounds. At elevated concentrations and exposures, human health effects from air toxics can
range from respiratory effects to cancer. Other health impacts include neurological
developmental and reproductive effects. The lexicologically significant VOCs emitted in
substantial quantities from the engines that are the subject of this proposal are discussed in more
detail in Section 1.4, below.
1.1.3 Additional Health and Welfare Effects of NOx Emissions
In addition to their role as an ozone precursor, NOx emissions are associated with a wide
variety of other health and welfare effects.4 5 Nitrogen dioxide can irritate the lungs and lower
resistance to respiratory infection (such as influenza). NOx emissions are an important precursor
to acid rain that may affect both terrestrial and aquatic ecosystems. Atmospheric deposition of
nitrogen leads to excess nutrient enrichment problems ("eutrophication") in the Chesapeake Bay
and several nationally important estuaries along the East and Gulf Coasts. Eutrophication can
produce multiple adverse effects on water quality and the aquatic environment, including
increased algal blooms, excessive phytoplankton growth, and low or no dissolved oxygen in
bottom waters. Eutrophication also reduces sunlight, causing losses in submerged aquatic
vegetation critical for healthy estuarine ecosystems. Deposition of nitrogen-containing
compounds also affects terrestrial ecosystems. Nitrogen fertilization can alter growth patterns
and change the balance of species in an ecosystem. In extreme cases, this process can result in
nitrogen saturation when additions of nitrogen to soil over time exceed the capacity of plants and
microorganisms to utilize and retain the nitrogen. These environmental impacts are discussed
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Draft Regulatory Support Document
further in Sections 1.6.4 and 1.6.5, below.
Elevated levels of nitrates in drinking water pose significant health risks, especially to
infants. Studies have shown that a substantial rise in nitrogen levels in surface waters are highly
correlated with human-generated inputs of nitrogen in those watersheds.6 These nitrogen inputs
are dominated by fertilizers and atmospheric deposition. Nitrogen dioxide and airborne nitrate
also contribute to pollutant haze, which impairs visibility and can reduce residential property
values and the value placed on scenic views.
1.1.4 Ozone Nonattainment
The current primary and secondary ozone National Ambient Air Quality Standard
(NAAQS) is 0.12 ppm daily maximum 1-hour concentration, not to be exceeded more than once
per year on average. The determination that an area is at risk of exceeding the ozone standard in
the future was made for all areas with current design values grater than or equal to 0.125 ppm (or
within a 10 percent margin) and with modeling evidence that exceedances will persist into the
future.
Ground level ozone today remains a pervasive pollution problem in the United States. In
1999, 90.8 million people (1990 census) lived in 31 areas designated nonattainment under the 1-
hour ozone NAAQS.7 This sharp decline from the 101 nonattainment areas originally identified
under the Clean Air Act Amendments of 1990 demonstrates the effectiveness of the last decade's
worth of emission-control programs. However, elevated ozone concentrations remain a serious
public health concern throughout the nation.
Over the last decade, declines in ozone levels were found mostly in urban areas, where
emissions are heavily influenced by controls on mobile sources and their fuels. Twenty-three
metropolitan areas have realized a decline in ozone levels since 1989, but at the same time ozone
levels in 11 metropolitan areas with 7 million people have increased.8 Regionally, California and
the Northeast have recorded significant reductions in peak ozone levels, while four other regions
(the Mid-Atlantic, the Southeast, the Central and Pacific Northwest) have seen ozone levels
increase.
The highest ambient concentrations are currently found in suburban areas, consistent with
downwind transport of emissions from urban centers. Concentrations in rural areas have risen to
the levels previously found only in cities. Particularly relevant to this proposal, ozone levels at
17 of our National Parks have increased, and in 1998, ozone levels in two parks, Shenandoah
National Park and the Great Smoky Mountains National Park, were 30 to 40 percent higher than
the ozone NAAQS over the last decade.9
To estimate future ozone levels, we refer to the modeling performed in conjunction with
the final rule for our most recent heavy-duty highway engine and fuel standards.10 We performed
a series of ozone air quality modeling simulations for nearly the entire Eastern U.S. covering
metropolitan areas from Texas to the Northeast.11 This ozone air quality model was based upon
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Chapter 1: Health and Welfare Concerns
the same modeling system as was used in the Tier 2 air quality analysis, with the addition of
updated inventory estimates for 2007 and 2030. The model simulations were performed for
several emission scenarios, and the model outputs were combined with current air quality data to
identify areas expected to exceed the ozone NAAQS in 2007, 2020, and 2030.12 The results of
this modeling are contained in Table 1.1-1. Areas presented in Table 1.1-1 have 1997-99 air
quality data indicating violations of the 1-hour ozone NAAQS, or are within 10 percent of the
standard, are predicted to have exceedance in 2007, 2020, or 2030. An area was considered
likely to have future exceedances if exceedances were predicted by the model, and the area is
currently violating the 1-hour standard, or is within 10 percent of violating the 1-hour standard.
Table 1.1-1 shows that 37 areas with a 1999 population of 91 million people are at risk of
exceeding the 1-hour ozone standard in 2007.
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Draft Regulatory Support Document
Table 1.1-1: Eastern Metropolitan Areas with Modeled Exceedances of the 1-Hour Ozone
Standard in 2007, 2020, or 2030 (Includes all emission controls through HD07 standards)
VISA or CMSA/ State
\tlanta, GA MSA
Barnstable-Yarmouth, MA MSA *
Baton Rouge, LA MSA
Beaumont-Port Arthur, TX MSA
Benton Harbor, MI MSA *
Biloxi-Gulfport-Pascagoula, MS MSA *
Birmingham, AL MSA
Boston-Worcester-Lawrence, MA CMSA
Charleston, WV MSA *
Charlotte-Gastonia-Rock Hill, NC MSA
Chicago-Gary-Kenosha, IL CMSA
Cincinnati-Hamilton, OH-KY-IN CMSA *
Cleveland-Akron, OH CMSA *
Detroit- Ann Arbor-Flint, MI CMSA
Grand Rapids-Muskegon-Holland, MI MSA*
lartford, CT MSA
rlourna, LA MSA *
rlouston-Galveston-Brazoria, TX CMSA
luntington-Ashland, WV-KY-OH MSA
.ake Charles, LA MSA *
.ouisville, KY-IN MSA
Vlacon, GA MSA
Memphis, TN-AR-MS MSA
Milwaukee-Racine, WI CMSA
Nashville, TN MSA
sfew London-Norwich, CT-RI MSA
sfew Orleans, LA MSA *
s[ew York-Northern NJ-Long Island, NY-NJ-CT-PA
CMSA
Norfolk- Virginia Beach-Newport News, VA-NC MSA *
3rlando, FL MSA *
Densacola, FL MSA
Philadelphia- Wilmington-Atlantic City, PA-NJ-DE-MD
CMSA
Drovidence-FallRiver-Warwick,RI-MAMSA*
Richmond-Petersburg, VA MSA
5t. Louis, MO-IL MSA
Tampa-St. Petersburg, FL MSA *
Washington-Baltimore
Total number of areas
Copulation
2007
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
37
91.2
2020
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
32
88.5
2030
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
32
87.8
pop (1999)
3.9
0.2
0.6
0.4
0.2
0.3
0.9
5.7
0.3
1.4
8.9
1.9
2.9
5.4
1.1
1.1
0.2
4.5
0.3
0.2
1
0.3
1.1
1.7
1.2
0.3
1.3
20.2
1.6
1.5
0.4
6
1.1
1
2.6
2.3
7.4
91.4
* These areas have registered 1997-1999 ozone concentrations within 10 percent of standard.
1-6
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Chapter 1: Health and Welfare Concerns
With regard to future ozone levels, our photochemical ozone modeling for 2020 predicts
exceedances of the 1-hour ozone standard in 32 areas with a total of 89 million people (1999
census; see Table 1.1-1). We expect that the control strategies contained in this proposal for
nonroad engines will further assist state efforts already underway to attain and maintain the 1-
hour ozone standard.
The inventories that underlie this predictive modeling for 2020 and 2030 include
reductions from all current and committed to federal, state and local control programs, including
the recently promulgated NOx and PM standards for heavy-duty vehicles and low sulfur diesel
fuel. The geographic scope of these areas at risk of future exceedances underscores the need for
additional, nationwide controls of ozone precursors.
It should be noted that this modeling did not attempt to examine the prospect of areas
attaining or maintaining the ozone standard with possible future controls (i.e., controls beyond
current or committed federal, State and local controls). Therefore, this information should be
interpreted as indicating what areas are at risk of ozone violations in 2007, 2020 or 2030 without
federal or state measures that may be adopted and implemented in the future. We expect many of
these areas to adopt additional emission reduction programs, but we are unable to quantify or rely
upon future reductions from additional State programs since they have not yet been adopted.
1.1.5 Public Health and Welfare Concerns from Prolonged and Repeated Exposures to
Ozone
In addition to the health effects described above, there exists a large body of scientific
literature that shows that harmful effects can occur from sustained levels of ozone exposure
much lower than 0.125 ppm. Studies of prolonged exposures, those lasting about 7 hours,
showed health effects from exposures to ozone concentrations as low as 0.08 ppm. Prolonged
and repeated exposures to ozone at these levels are common in areas that do not attain the 1-hour
NAAQS, and also occur in areas where ambient concentrations of ozone are in compliance with
the 1-hour NAAQS.
Prolonged exposure to levels of ozone below the NAAQS have been reported to cause or
be statistically associated with transient pulmonary function responses, transient respiratory
symptoms, effects on exercise performance, increased airway responsiveness, increased
susceptibility to respiratory infection, increased hospital and emergency room visits, and transient
pulmonary respiratory inflamation. Such acute health effects have been observed following
prolonged exposures at moderate levels of exertion at concentrations of ozone as low as 0.08
ppm, the lowest concentration tested. The effects are more pronounced as concentrations
increase, affecting more subjects or having a greater effect on a given subject in terms of
functional changes or symptoms. A detailed summary and discussion of the large body of ozone
health effects research may be found in Chapters 6 through 9 (Volume 3) of the 1996 Criteria
Document for ozone.13 Monitoring data indicates that 333 counties in 33 states exceed these
levels in 1997-99.14
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Draft Regulatory Support Document
To provide a quantitative estimate of the projected number of people anticipated to reside
in areas in which ozone concentrations are predicted to exceed the 8-hour level of 0.08 to 0.12
ppm or higher for multiple days, we performed regional modeling using the variable-grid Urban
Airshed Model (UAM-V).15 UAM-V is a photochemical grid model that numerically simulates
the effects of emissions, advection, diffusion, chemistry, and surface removal processes on
pollutant concentrations within a 3-dimensional grid. As with the previous modeling analysis,
the inventories that underlie this predictive modeling include reductions from all current and
committed to federal, state and local control programs, including the recently promulgated NOx
and PM standards for heavy-duty vehicles and low sulfur diesel fuel. This modeling forecast that
111 million people are predicted to live in areas that areas at risk of exceeding these moderate
ozone levels for prolonged periods of time in 2020 after accounting for expected inventory
reductions due to controls on light- and heavy-duty on-highway vehicles; that number is expected
to increase to 125 million in 2030.16 Prolonged and repeated ozone concentrations at these levels
are common in areas throughout the country, and are found both in areas that are exceeding, and
areas that are not exceeding, the 1-hour ozone standard. Areas with these high concentrations are
more widespread than those in nonattainment for that 1-hour ozone standard.
Ozone at these levels can have other welfare effects, with damage to plants being of most
concern. Plant damage affects crop yields, forestry production, and ornamentals. The adverse
effect of ozone on forests and other natural vegetation can in turn cause damage to associated
ecosystems, with additional resulting economic losses. Prolonged ozone concentrations of 0.10
ppm can be phytotoxic to a large number of plant species, and can produce acute injury and
reduced crop yield and biomass production. Ozone concentrations within the range of 0.05 to
0.10 ppm have the potential over a longer duration of creating chronic stress on vegetation that
can result in reduced plant growth and yield, shifts in competitive advantages in mixed
populations, decreased vigor, and injury. Ozone effects on vegetation are presented in more
detail in Chapter 5, Volume II of the 1996 Criteria Document.
1.2 Carbon Monoxide
1.2.1 General Background
Unlike many gases, CO is odorless, colorless, tasteless, and nonirritating. Carbon
monoxide results from incomplete combustion of fuel and is emitted directly from vehicle
tailpipes. Incomplete combustion is most likely to occur at low air-to-fuel ratios in the engine.
These conditions are common during vehicle starting when air supply is restricted ("choked"),
when cars are not tuned properly, and at high altitude, where "thin" air effectively reduces the
amount of oxygen available for combustion (except in cars that are designed or adjusted to
compensate for altitude). Carbon monoxide emissions increase dramatically in cold weather.
This is because engines need more fuel to start at cold temperatures and because some emission
control devices (such as oxygen sensors and catalytic converters) operate less efficiently when
they are cold. Also, nighttime inversion conditions are more frequent in the colder months of the
year. This is due to the enhanced stability in the atmospheric boundary layer, which inhibits
vertical mixing of emissions from the surface.
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Chapter 1: Health and Welfare Concerns
1.2.2 Health Effects of CO
Carbon monoxide enters the bloodstream through the lungs and forms
carboxyhemoglobin, a compound that inhibits the blood's capacity to carry oxygen to organs and
tissues. Carbon monoxide has long been known to have substantial adverse effects on human
health, including toxic effects on blood and tissues, and effects on organ functions. Carbon
monoxide has been linked to increased risk for people with heart disease, reduced visual
perception, cognitive functions and aerobic capacity, and possible fetal effects. Persons with
heart disease are especially sensitive to carbon monoxide poisoning and may experience chest
pain if they breathe the gas while exercising. Infants, elderly persons, and individuals with
respiratory diseases are also particularly sensitive. Carbon monoxide can affect healthy
individuals, impairing exercise capacity, visual perception, manual dexterity, learning functions,
and ability to perform complex tasks. More importantly to many individuals is the frequent
exposure of individuals to exhaust emissions from engines operating indoors. The Occupational
Safety and Health Administration sets standards regulating the concentration of indoor
pollutants, but high local CO levels are still commonplace.
Several recent epidemiological studies have shown a link between CO and premature
morbidity (including angina, congestive heart failure, and other cardiovascular diseases). Several
studies in the United States and Canada have also reported an association of ambient CO
exposures with frequency of cardiovascular hospital admissions, especially for congestive heart
failure (CHF). An association of ambient CO exposure with mortality has also been reported in
epidemiological studies, though not as consistently or specifically as with CHF admissions. EPA
reviewed these studies as part of the Criteria Document review process. The CO Criteria
Document (EPA 600/P-99/001F) contains additional information about the health effects of CO,
human exposure, and air quality. It was published as a final document and made available to the
public in August 2000 (www.epa.gov/ncea/co/).
1.2.3 CO Nonattaiment
The current primary NAAQS for CO are 35 parts per million for the one-hour average
and 9 parts per million for the eight-hour average. These values are not to be exceeded more
than once per year. Air quality carbon monoxide value is estimated using EPA guidance for
calculating design values. In 1999, 30.5 million people (1990 census) lived in 17 areas
designated nonattainment under the CO NAAQS.17
Snowmobiles, which have relatively high per engine CO emissions, can be a significant
source of ambient CO levels in CO nonattainment areas. Several states that contain CO
nonattainment areas also have large populations of registered snowmobiles. This is shown in
Table 1.2-1. A review of snowmobile trail maps indicates that snowmobiles are used in these
CO nonattainment areas or in adjoining counties.18 These include the Mt. Spokane and Riverside
trails near the Spokane Washington CO nonattainment area; the Larimer trails near the Fort
Collins, Colorado CO nonattainment area; and the Hyatt Lake, Lake of the Woods, and Cold
Springs trails near the Klamath Falls and Medford, Oregon CO nonattainment area. There are
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Draft Regulatory Support Document
also trails in Missoula County, Montana that demonstrate snowmobile use in the Missoula,
Montana CO nonattainment area. While Colorado has a large snowmobile population, the
snowmobile trails are fairly distant from the Colorado Springs CO nonattainment area.19
Table 1.2-1
Snowmobile Use in Selected CO Nonattainment Areas
City and State
Fairbanks, AK
Spokane, WA
Colorado Springs, CO
Fort Collins, CO
Klamath Falls, OR
Medford, OR
Missoula, MT
CO Nonattainment
Classification
Serious
Serious
Moderate
Moderate
Moderate
Moderate
Moderate
1998 State snowmobile
population"
12,997
32,274
28,000
13,426
14,361
aSource: Letter from International Snowmobile Manufacturers Association to US-EPA, July 8, 1999,
Docket A-2000-01, Document No. II-G-136
Exceedances of the 8-hour CO standard were recorded in three of these seven CO
nonattainment areas located in the northern portion of the country over the five year period from
1994 to 1999: Fairbanks, AK; Medford, OR; and Spokane, WA.20 Given the variability in CO
ambient concentrations due to weather patterns such as inversions, the absence of recent
exceedances for some of these nonattainment areas should not be viewed as eliminating the need
for further reductions to consistently attain and maintain the standard. A review of CO monitor
data in Fairbanks from 1986 to 1995 shows that while median concentrations have declined
steadily, unusual combinations of weather and emissions have resulted in elevated ambient CO
concentrations well above the 8-hour standard of 9 ppm. Specifically, a Fairbanks monitor
recorded average 8-hour ambient concentrations at 16 ppm in 1988, around 9 ppm from 1990 to
1992, and then a steady increase in CO ambient concentrations at 12, 14 and 16 ppm during some
extreme cases in 1993, 1994 and 1995, respectively.21
Nationally, significant progress has been made over the last decade to reduce CO
emissions and ambient CO concentrations. Total CO emissions from all sources have decreased
16 percent from 1989 to 1998, and ambient CO concentrations decreased by 39 percent. During
that time, while the mobile source CO contribution of the inventory remained steady at about 77
percent, the highway portion decreased from 62 percent of total CO emissions to 56 percent
while the nonroad portion increased from 17 percent to 22 percent.22 Over the next decade, we
would expect there to be a minor decreasing trend from the highway segment due primarily to the
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Chapter 1: Health and Welfare Concerns
more stringent standards for certain light-duty trucks (LDT2s).23 CO standards for passenger cars
and other light-duty trucks and heavy-duty vehicles did not change as a result of other recent
rulemakings. As described in Section 1.5, below, the engines subject to this rule currently
account for about 7 percent of the mobile source CO inventory; this is expected to increase to 10
percent by 2020 without the emission controls proposed in this action.
The state of Alaska recently submitted draft CO attainment SIPs to the Agency for the
Fairbanks CO nonattainment area. Fairbanks is located in a mountain valley with a much higher
potential for air stagnation than cities within the contiguous United States. Nocturnal inversions
that give rise to elevated CO concentrations can persist 24-hours a day due to the low solar
elevation, particularly in December and January. These inversions typically last from 2 to 4 days
(Bradley et al., 1992), and thus inversions may continue during hours of maximum CO emissions
from mobile sources. Despite the fact that snowmobiles are largely banned in CO nonattainment
areas by the state, the state estimated that snowmobiles contributed 0.3 tons/day in 1995 to
Fairbanks' CO nonattainment area or 1.2 percent of a total inventory of 23.3 tons per day in
2001.24 While Fairbanks has made significant progress in reducing ambient CO concentrations,
existing climate conditions make achieving and maintaining attainment challenging. Fairbanks
failed to attain the CO NAAQS by the applicable deadline of December 21, 2000, and EPA
approved a one-year extension in May of 2001.25
In addition to the health effects that can result from exposure to carbon monoxide, this
pollutant also can contribute to ground level ozone formation.26 Recent studies in atmospheric
chemistry in urban environments suggest CO can react with hydrogen-containing radicals,
leaving fewer of these to combine with non-methane hydrocarbons and thus leading to increased
levels of ozone. Few analyses have been performed that estimate these effects, but a study of an
ozone episode in Atlanta, GA in 1988 found that CO accounted for about 17.5 percent of the
ozone formed (compared to 82.5 percent for volatile organic compounds). While different cities
may have different results, the effects of CO emissions on ground level ozone are not
insignificant. The engines that are the subject of the proposed standards are contributors to these
effects in urban areas, particularly because their per engine emissions are so high. For example,
CO emissions from a off-highway motorcycle are high relative to a passenger car, (32 g/mi
compared to 4.2 g/mi).
1.3 Particulate Matter
1.3.1 General Background
Particulate pollution is a problem affecting urban and non-urban localities in all regions
of the United States. Nonroad engines and vehicles that would be subject to the proposed
standards contribute to ambient particulate matter (PM) levels in two ways. First, they contribute
through direct emissions of particulate matter. Second, they contribute to indirect formation of
PM through their emissions of organic carbon, especially HC. Organic carbon accounts for
between 27 and 36 percent of fine particle mass depending on the area of the country.
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Parti culate matter represents a broad class of chemically and physically diverse
substances. It can be principally characterized as discrete particles that exist in the condensed
(liquid or solid) phase spanning several orders of magnitude in size. All particles equal to and
less than 10 microns are called PM10. Fine particles can be generally defined as those particles
with an aerodynamic diameter of 2.5 microns or less (also known as PM25), and coarse fraction
particles are those particles with an aerodynamic diameter greater than 2.5 microns, but equal to
or less than a nominal 10 microns.
Manmade emissions that contribute to airborne particulate matter result principally from
combustion sources (stationary and mobile sources) and fugitive emissions from industrial
processes and non-industrial processes (such as roadway dust from paved and unpaved roads,
wind erosion from cropland, construction, etc.). Human-generated sources of particles include a
variety of stationary sources (including power generating plants, industrial operations,
manufacturing plants, waste disposal) and mobile sources (light- and heavy-duty on-road
vehicles, and off-highway vehicles such as construction, farming, industrial, locomotives, marine
vessels and other sources). Natural sources also contribute to particulate matter in the
atmosphere and include sources such as wind erosion of geological material, sea spray, volcanic
emissions, biogenic emanation (e.g., pollen from plants, fungal spores), and wild fires.
The chemical and physical properties of PM vary greatly with time, region, meteorology,
and source category. Particles may be emitted directly to the atmosphere (primary particles) or
may be formed by transformations of gaseous emissions of sulfur dioxide, nitrogen oxides or
volatile organic compounds (secondary particles). Secondary PM is dominated by sulfate in the
eastern U.S. and nitrate in the western U.S.27 The vast majority (>90 percent) of the direct
mobile source PM emissions and their secondary formation products are in the fine PM size
range. Mobile sources can reasonably be estimated to contribute to ambient secondary nitrate
and sulfate PM in proportion to their contribution to total NOx and SOx emissions.
Table 1.3-1: Percent Contribution to PM2, by Component, 1998
Sulfate
Elemental Carbon
Organic Carbon
Nitrate
Crustal Material
East
56
5
27
5
7
West
33
6
36
8
17
Source: National Air Quality and Emissions Trends Report, 1998, March, 2000, at 28. This document is
available at ht<33://ww^ejajMv/^^ Relevant pages of this report can be found in Memorandum
to Air Docket A-2000-01 from Jean Marie Revelt, September 5, 2001, Document No. II-A-63.
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Chapter 1: Health and Welfare Concerns
1.3.2 Health and Welfare Effects of PM
Particulate matter can adversely affect human health and welfare. Discussions of the
health and welfare effects associated with ambient PM can be found in the Air Quality Criteria
for Paniculate Matter.28
Key EPA findings regarding the health risks posed by ambient PM are summarized as
follows:
a. Health risks posed by inhaled particles are affected both by the penetration and deposition
of particles in the various regions of the respiratory tract, and by the biological responses
to these deposited materials.
b. The risks of adverse effects associated with deposition of ambient particles in the thorax
(tracheobronchial and alveolar regions of the respiratory tract) are markedly greater than
for deposition in the extrathoracic (head) region. Maximum particle penetration to the
thoracic regions occurs during oronasal or mouth breathing.
c. Published studies have found statistical associations between PM and several key health
effects, including premature death; aggravation of respiratory and cardiovascular disease,
as indicated by increased hospital admissions and emergency room visits, school
absences, work loss days, and restricted activity days; changes in lung function and
increased respiratory symptoms; changes to lung tissues and structure; and altered
respiratory defense mechanisms. Most of these effects have been consistently associated
with ambient PM concentrations, which have been used as a measure of population
exposure, in a large number of community epidemiological studies. Additional
information and insights on these effects are provided by studies of animal toxicology and
controlled human exposures to various constituents of PM conducted at higher than
ambient concentrations. Although mechanisms by which particles cause effects are not
well known, there is general agreement that the cardio-respiratory system is the major
target of PM effects.
d. Based on a qualitative assessment of the epidemiological evidence of effects associated
with PM for populations that appear to be at greatest risk with respect to particular health
endpoints, we have concluded the following with respect to sensitive populations:
1. Individuals with respiratory disease (e.g., chronic obstructive pulmonary disease,
acute bronchitis) and cardiovascular disease (e.g., ischemic heart disease) are at
greater risk of premature mortality and hospitalization due to exposure to ambient
PM.
2. Individuals with infectious respiratory disease (e.g., pneumonia) are at greater risk
of premature mortality and morbidity (e.g., hospitalization, aggravation of
respiratory symptoms) due to exposure to ambient PM. Also, exposure to PM
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Draft Regulatory Support Document
may increase individuals' susceptibility to respiratory infections.
3. Elderly individuals are also at greater risk of premature mortality and
hospitalization for cardiopulmonary problems due to exposure to ambient PM.
4. Children are at greater risk of increased respiratory symptoms and decreased lung
function due to exposure to ambient PM.
5. Asthmatic individuals are at risk of exacerbation of symptoms associated with
asthma, and increased need for medical attention, due to exposure to PM.
e. There are fundamental physical and chemical differences between fine and coarse fraction
particles. The fine fraction contains acid aerosols, sulfates, nitrates, transition metals,
diesel exhaust particles, and ultra fine particles; the coarse fraction typically contains high
mineral concentrations, silica and resuspended dust. It is reasonable to expect that
differences may exist in both the nature of potential effects elicited by coarse and fine PM
and the relative concentrations required to produce such effects. Both fine and coarse
particles can accumulate in the respiratory system. Exposure to coarse fraction particles
is primarily associated with the aggravation of respiratory conditions such as asthma.
Fine particles are closely associated with health effects such as premature death or
hospital admissions, and for cardiopulmonary diseases.
With respect to welfare or secondary effects, fine particles have been clearly associated
with the impairment of visibility over urban areas and large multi-State regions. Particles also
contribute to soiling and materials damage. Components of particulate matter (e.g., sulfuric or
nitric acid) also contribute to acid deposition, nitrification of surface soils and water
eutrophication of surface water.
1.3.3 PM Nonattainment
The NAAQS for PM10 was established in 1987. According to these standards, the short
term (24-hour) standard of 150 //g/m3 is not to be exceeded more than once per year on average
over three years. The long-term standard specifies an expected annual arithmetic mean not to
exceed 50 //g/m3 over three years.
The most recent PM10 monitoring data indicate that 14 designated PM10 nonattainment
areas with a projected population of 23 million violated the PM10 NAAQS in the period 1997-
1999. Table 1.3-2 lists the 14 areas, and also indicates the PM10 nonattainment classification,
and 1999 projected population for each PM10 nonattainment area. The projected population in
1999 was based on 1990 population figures which were then increased by the amount of
population growth in the county from 1990 to 1999.
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Chapter 1: Health and Welfare Concerns
Table 1.3-2: PM,,, Nonattainment Areas Violating the PM,,, NAAQS in 1997- 1999
Nonattainment Area or County
Anthony, NM (Moderate)8
Clark Co [Las Vegas], NV (Serious)
Coachella Valley, CA (Serious)
El Paso Co, TX (Moderate) A
Hay den/Mi ami, AZ (Moderate)
Imperial Valley, CA (Moderate)
Los Angeles South Coast Air Basin, CA (Serious)
Nogales, AZ (Moderate)
Owens Valley, CA (Serious)
Phoenix, AZ (Serious)
San Joaquin Valley, CA (Serious)
Searles Valley, CA (Moderate)
Wallula, WA (Moderate)8
Washoe Co [Reno], NV (Moderate)
Total Areas: 14
1999 Population
(projected, in millions)
0.003
1.200
0.239
0.611
0.004
0.122
14.352
0.025
0.018
2.977
3.214
0.029
0.052
0.320
23.167
A EPA has determined that continuing PM10 nonattainment in El Paso, TX is attributable to transport under
section 179(B).
B The violation in this area has been determined to be attributable to natural events under section 188(f) of
the Act.
In addition to the 14 PM10 nonattainment areas that are currently violating the PM10
NAAQS listed in Table 1.3-2, there are 25 unclassifiable areas that have recently recorded
ambient concentrations of PM10 above the PM10 NAAQS. EPA adopted a policy in 1996 that
allows areas with PM10 exceedances that are attributable to natural events to retain their
designation as unclassifiable if the State is taking all reasonable measures to safeguard public
health regardless of the sources of PM10 emissions. Areas that remain unclassifiable areas are not
required under the Clean Air Act to submit attainment plans, but we work with each of these
areas to understand the nature of the PM10 problem and to determine what best can be done to
reduce it. With respect to the monitored violations reported in 1997-99 in the 25 areas
designated as unclassifiable, we have not yet excluded the possibility that factors such as a one-
time monitoring upset or natural events, which ordinarily would not result in an area being
designated as nonattainment for PM10, may be responsible for the problem. Emission reductions
from today's action will assist these currently unclassifiable areas to achieve ambient PM10
concentrations below the current PM10 NAAQS.
Current 1999 PM25 monitored values, which cover about a third of the nation's counties,
indicate that at least 40 million people live in areas where long-term ambient fine particulate
matter levels are at or above 16 //g/m3 (37 percent of the population in the areas with monitors).29
This 16 //g/m3 threshold is the low end of the range of long term average PM2 5 concentrations in
cities where statistically significant associations were found with serious health effects, including
premature mortality.30 To estimate the number of people who live in areas where long-term
ambient fine particulate matter levels are at or above 16 //g/m3 but for which there are no
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Draft Regulatory Support Document
monitors, we can use modeling. According to our national modeled predictions, there were a
total of 76 million people (1996 population) living in areas with modeled annual average PM25
concentrations at or above 16 //g/m3 (29 percent of the population).31
To estimate future PM2 5 levels, we refer to the modeling performed in conjunction with
the final rule for our most recent heavy-duty highway engine and fuel standards using EPA's
Regulatory Model System for Aerosols and Deposition (REMSAD).32 The most appropriate
method of making these projections relies on the model to predict changes between current and
future states. Thus, we have estimated future conditions only for the areas with current PM2 5
monitored data (which covers about a third of the nation's counties). For these counties,
REMSAD predicts the current level of 37 percent of the population living in areas where fine PM
levels are at or above 16 //g/m3 to increase to 49 percent in 2030.33
Emissions of HCs from snowmobiles contribute to secondary formation of fine
particulate matter which can cause a variety of adverse health and welfare effects, including
regional haze discussed in Section 1.6 below. For 20 counties across nine states, snowmobile
trails are found within or near counties that registered ambient PM 2.5 concentrations at or above
15 //g/m3, the level of the revised national ambient air quality standard for fine particles.34
These counties are listed in Table 1.3.-3. To obtain the information about snowmobile trails
contained in Table 1.3.-3, we consulted snowmobile trail maps that were supplied by various
states.35
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Chapter 1: Health and Welfare Concerns
Table 1.3-3
Counties with Annual PM2 5 Levels Above 16 //g/m3 and Snowmobile Trails
State
Ohio
Montana
California
Minnesota
Wisconsin
Oregon
Pennsylvania
Illinois
Iowa
PM2 5 Exceedance
County
Mahoning
Trumbull
Summit
Montgomery
Portage
Franklin
Marshall/Ohio (WV)
Lincoln
Tulane
Butte
Fresno
Kern
Washington
Wright
Waukesha
Milwaukee
Jackson
Klamath
Washington
Rock Island
Rock Island (IL)
County with
Snowmobile Trails
Mahoning
Trumbull
Summit
Montgomery
Portage
Delaware
Belmont
Lincoln
Tulane
Butte
Fresno
Kern
Washington
Wright
Waukesha
Milwaukee
Douglas
Douglas
Layette
Somerset
Rock Island
Henry
Dubuque
Proximity to PM2 5
Exceedance County
—
—
—
—
—
Borders North
Borders West
—
—
—
—
—
—
—
—
—
Borders NNE
Borders North
Borders East
—
—
Borders East
Borders West
1.4 Gaseous Air Toxics
In addition to the human health and welfare impacts described above, emissions from the
engines covered by this proposal also contain several other substances that are known or
suspected human or animal carcinogens, or have serious noncancer health effects. These include
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benzene, 1,3-butadiene, formaldehyde, acetaldehyde, and acrolein. The health effects of these air
toxics are described in more detail in Chapter 1 of the Draft Regulatory Support Document for
this rule. Additional information can also be found in the Technical Support Document four our
final Mobile Source Air Toxics rule.36
1.4.1 Benzene
Benzene is an aromatic hydrocarbon which is present as a gas in both exhaust and
evaporative emissions from motor vehicles. Benzene in the exhaust, expressed as a percentage
of total organic gases (TOG), varies depending on control technology (e.g., type of catalyst) and
the levels of benzene and other aromatics in the fuel, but is generally about three to five percent.
The benzene fraction of evaporative emissions depends on control technology and fuel
composition and characteristics (e.g., benzene level and the evaporation rate), and is generally
about one percent.37
EPA has recently reconfirmed that benzene is a known human carcinogen by all routes of
exposure.38 Respiration is the major source of human exposure. Long-term respiratory exposure
to high levels of ambient benzene concentrations has been shown to cause cancer of the tissues
that form white blood cells. Among these are acute nonlymphocytic leukemia,39 chronic
lymphocytic leukemia and possibly multiple myeloma (primary malignant tumors in the bone
marrow), although the evidence for the latter has decreased with more recent studies.40'41
Leukemias, lymphomas, and other tumor types have been observed in experimental animals
exposed to benzene by inhalation or oral administration. Exposure to benzene and/or its
metabolites has also been linked with genetic changes in humans and animals42 and increased
proliferation of mouse bone marrow cells.43 The occurrence of certain chromosomal changes in
individuals with known exposure to benzene may serve as a marker for those at risk for
contracting leukemia.44
A number of adverse noncancer health effects, blood disorders such as preleukemia and
aplastic anemia, have also been associated with low-dose, long-term exposure to benzene.45
People with long-term exposure to benzene may experience harmful effects on the blood-forming
tissues, especially the bone marrow. These effects can disrupt normal blood production and
cause a decrease in important blood components, such as red blood cells and blood platelets,
leading to anemia (a reduction in the number of red blood cells), leukopenia (a reduction in the
number of white blood cells), or thrombocytopenia (a reduction in the number of blood platelets,
thus reducing the ability for blood to clot). Chronic inhalation exposure to benzene in humans
and animals results in pancytopenia,46 a condition characterized by decreased numbers of
circulating erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes
(blood platelets).47'48 Individuals that develop pancytopenia and have continued exposure to
benzene may develop aplastic anemia,49 whereas others exhibit both pancytopenia and bone
marrow hyperplasia (excessive cell formation), a condition that may indicate a preleukemic
state.50 51 The most sensitive noncancer effect observed in humans is the depression of absolute
lymphocyte counts in the circulating blood.52
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Chapter 1: Health and Welfare Concerns
1.4.2 1,3-Butadiene
1,3-Butadiene is formed in vehicle exhaust by the incomplete combustion of fuel. It is
not present in vehicle evaporative emissions, because it is not present in any appreciable amount
in fuel. 1,3-Butadiene accounts for 0.4 to 1.0 percent of total organic gas exhaust, depending on
control technology and fuel composition.53
1,3-Butadiene was classified by EPA as a Group B2 (probable human) carcinogen in
1985.54 This classification was based on evidence from two species of rodents and epidemiologic
data. In the EPA1998 draft Health Risk Assessment of 1,3-Butadiene, that was reviewed by the
Science Advisory Board (SAB), the EPA proposed that 1,3-butadiene is a known human
carcinogen based on human epidemiologic, laboratory animal data, and supporting data such as
the genotoxicity of 1,3-butadiene metabolites.55 The Environmental Health Committee of EPA's
Scientific Advisory Board (SAB) reviewed the draft document in August 1998 and recommended
that 1,3-butadiene be classified as a probable human carcinogen, stating that designation of 1,3-
butadiene as a known human carcinogen should be based on observational studies in humans,
without regard to mechanistic or other information.56 In applying the 1996 proposed Guidelines
for Carcinogen Risk Assessment, the Agency relies on both observational studies in humans as
well as experimental evidence demonstrating causality, and therefore the designation of 1,3-
butadiene as a known human carcinogen remains applicable.57 The Agency has revised the draft
Health Risk Assessment of 1,3-Butadiene based on the SAB and public comments. The draft
Health Risk Assessment of 1,3-Butadiene will undergo the Agency consensus review, during
which time additional changes may be made prior to its public release and placement on the
Integrated Risk Information System (IRIS).
1,3-Butadiene also causes a variety of noncancer reproductive and developmental effects
in mice and rats (no human data) when exposed to long-term, low doses of butadiene.58 The
most sensitive effect was reduced litter size at birth and at weaning. These effects were observed
in studies in which male mice exposed to 1,3-butadiene were mated with unexposed females. In
humans, such an effect might manifest itself as an increased risk of spontaneous abortions,
miscarriages, still births, or very early deaths. Long-term exposures to 1,3-butadiene should be
kept below its reference concentration of 4.0 microgram/m3 to avoid appreciable risks of these
reproductive and developmental effects.59 EPA has developed a draft chronic, subchronic, and
acute RfC values for 1,3-butadiene exposure as part of the draft risk characterization mentioned
above. The RfC values will be reported on IRIS.
1.4.3 Formaldehyde
Formaldehyde is the most prevalent aldehyde in vehicle exhaust. It is formed from
incomplete combustion of both gasoline and diesel fuel and accounts for one to four percent of
total organic gaseous emissions, depending on control technology and fuel composition. It is not
found in evaporative emissions.
Formaldehyde exhibits extremely complex atmospheric behavior.60 It is formed by the
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atmospheric oxidation of virtually all organic species, including biogenic (produced by a living
organism) hydrocarbons. Mobile sources contribute both primary formaldehyde (emitted directly
from motor vehicles) and secondary formaldehyde (formed from photooxidation of other VOCs
emitted from vehicles).
EPA has classified formaldehyde as a probable human carcinogen based on limited
evidence for carcinogenicity in humans and sufficient evidence of carcinogenicity in animal
studies, rats, mice, hamsters, and monkeys.61 Epidemiological studies in occupationally exposed
workers suggest that long-term inhalation of formaldehyde may be associated with tumors of the
nasopharyngeal cavity (generally the area at the back of the mouth near the nose), nasal cavity,
and sinus. Studies in experimental animals provide sufficient evidence that long-term inhalation
exposure to formaldehyde causes an increase in the incidence of squamous (epithelial) cell
carcinomas (tumors) of the nasal cavity. The distribution of nasal tumors in rats suggests that not
only regional exposure but also local tissue susceptibility may be important for the distribution of
formaldehyde-induced tumors.62 Research has demonstrated that formaldehyde produces
mutagenic activity in cell cultures.63
Formaldehyde exposure also causes a range of noncancer health effects. At low
concentrations (0.05-2.0 ppm), irritation of the eyes (tearing of the eyes and increased blinking)
and mucous membranes is the principal effect observed in humans. At exposure to 1-11 ppm,
other human upper respiratory effects associated with acute formaldehyde exposure include a dry
or sore throat, and a tingling sensation of the nose. Sensitive individuals may experience these
effects at lower concentrations. Forty percent of formaldehyde-producing factory workers
reported nasal symptoms such as rhinitis (inflammation of the nasal membrane), nasal
obstruction, and nasal discharge following chronic exposure.64 In persons with bronchial asthma,
the upper respiratory irritation caused by formaldehyde can precipitate an acute asthmatic attack,
sometimes at concentrations below 5 ppm.65 Formaldehyde exposure may also cause bronchial
asthma-like symptoms in non-asthmatics.66 67
Immune stimulation may occur following formaldehyde exposure, although conclusive
evidence is not available. Also, little is known about formaldehyde's effect on the central
nervous system. Several animal inhalation studies have been conducted to assess the
developmental toxicity of formaldehyde. The only exposure-related effect noted in these studies
was decreased maternal body weight gain at the high-exposure level. No adverse effects on
reproductive outcome of the fetuses that could be attributed to treatment were noted. An
inhalation reference concentration (RfC), below which long-term exposures would not pose
appreciable noncancer health risks, is not available for formaldehyde at this time.
1.4.4 Acetaldehyde
Acetaldehyde is a saturated aldehyde that is found in vehicle exhaust and is formed as a
result of incomplete combustion of both gasoline and diesel fuel. It is not a component of
evaporative emissions. Acetaldehyde comprises 0.4 to 1.0 percent of total organic gas exhaust,
depending on control technology and fuel composition.68
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Chapter 1: Health and Welfare Concerns
The atmospheric chemistry of acetaldehyde is similar in many respects to that of
formaldehyde.69 Like formaldehyde, it is produced and destroyed by atmospheric chemical
transformation. Mobile sources contribute to ambient acetaldehyde levels both by their primary
emissions and by secondary formation resulting from their VOC emissions. Acetaldehyde
emissions are classified as a probable human carcinogen. Studies in experimental animals
provide sufficient evidence that long-term inhalation exposure to acetaldehyde causes an increase
in the incidence of nasal squamous cell carcinomas (epithelial tissue) and adenocarcinomas
(glandular tissue).70 71
Noncancer effects in studies with rats and mice showed acetaldehyde to be moderately
toxic by the inhalation, oral, and intravenous routes.72 73 74 The primary acute effect of exposure
to acetaldehyde vapors is irritation of the eyes, skin, and respiratory tract. At high
concentrations, irritation and pulmonary effects can occur, which could facilitate the uptake of
other contaminants. Little research exists that addresses the effects of inhalation of acetaldehyde
on reproductive and developmental effects. The in vitro and in vivo studies provide evidence to
suggest that acetaldehyde may be the causative factor in birth defects observed in fetal alcohol
syndrome, though evidence is very limited linking these effects to inhalation exposure. Long-
term exposures should be kept below the reference concentration of 9 |ig/m3 to avoid appreciable
risk of these noncancer health effects.75
1.4.5 Acrolein
Acrolein is extremely toxic to humans from the inhalation route of exposure, with acute
exposure resulting in upper respiratory tract irritation and congestion. Although no information
is available on its carcinogenic effects in humans, based on laboratory animal data, EPA
considers acrolein a possible human carcinogen.76
1.5 Inventory Contributions
1.5.1 Inventory Contribution
The contribution of emissions from the nonroad engines and vehicles that would be
subject to the proposed standards to the national inventories of pollutants that are associated with
the health and public welfare effects described in this chapter are considerable. To estimate
nonroad engine and vehicle emission contributions, we used the latest version of our NONROAD
emissions model. This model computes nationwide, state, and county emission levels for a wide
variety of nonroad engines, and uses information on emission rates, operating data, and
population to determine annual emission levels of various pollutants. A more detailed
description of the model and our estimation methodology can be found in the Chapter 6 of this
document.
Baseline emission inventory estimates for the year 2000 for the categories of engines and
vehicles covered by this proposal are summarized in Table 1.5-1. This table show the relative
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contributions of the different mobile-source categories to the overall national mobile-source
inventory. Of the total emissions from mobile sources, the categories of engines and vehicles
covered by this proposal contribute about 13 percent, 3 percent, 6 percent, and 1 percent of HC,
NOx, CO, and PM emissions, respectively, in the year 2000. The results for large SI engines
indicate they contribute approximately 3 percent to HC, NOx, and CO emissions from mobile
sources. The results for land-based recreational engines reflect the impact of the significantly
different emissions characteristics of two-stroke engines. These engines are estimated to
contribute 10 percent of HC emissions and 3 percent of CO from mobile sources. Recreational
CI marine contribute less than 1 percent to NOx mobile source inventories. When only nonroad
emissions are considered, the engines and vehicles that would be subject to the proposed
standards would account for a larger share.
Our draft emission projections for 2020 for the nonroad engines and vehicles subject to
this proposal show that emissions from these categories are expected to increase over time if left
uncontrolled. The projections for 2020 are summarized in Table 1.5-2 and indicate that the
categories of engines and vehicles covered by this proposal are expected to contribute 33 percent,
9 percent, 9 percent, and 2 percent of HC, NOx, CO, and PM emissions in the year 2020.
Population growth and the effects of other regulatory control programs are factored into these
projections. The relative importance of uncontrolled nonroad engines is higher than the
projections for 2000 because there are already emission control programs in place for the other
categories of mobile sources which are expected to reduce their emission levels. The
effectiveness of all control programs is offset by the anticipated growth in engine populations.
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Chapter 1: Health and Welfare Concerns
Table 1.5-1
Modeled Annual Emission Levels for
Mobile-Source Categories in 2000 (thousand short tons)
Category
Total for engines subject to
proposed standards
Nonroad Large SI > 19 kW
Recreational SI
Recreation Marine CI
Highway Motorcycles
Marine SI Evap
Marine SI Exhaust
Nonroad SI< 19 kW
Nonroad CI
Commercial Marine CI
Locomotive
Total Nonroad
Total Highway
Aircraft
Total Mobile Sources
Total Man-Made Sources
Mobile Source percent of Total
Man-Made Sources
NOx
tons
343
306
13.0
24
8
0
32
106
2,625
977
1,192
5,275
7,981
178
13,434
24,538
55%
percent
of
mobile
source
3%
2%
0.10%
0.2%
0%
0.0%
0.2%
0.8%
20%
7%
9%
39%
59%
1%
100%
-
-
HC
tons
985
247
737
1
84
89
708
1,460
316
30
47
3,635
3,811
183
7,629
18,575
41%
percent of
mobile
source
13%
3%
10%
0%
1%
1%
9%
19%
4%
0%
1%
48%
50%
2%
100%
-
-
CO
tons
4,870
2,294
2,572
4
329
0
2,144
18,359
1,217
129
119
26,838
49,811
1,017
77,666
99,745
78%
percent of
mobile
source
6%
3%
3%
0%
0%
0%
3%
24%
2%
0.2%
0.2%
35%
64%
1%
100%
-
-
PM
tons
8.3
1.6
5.7
1
0.4
0
38
50
253
41
30
420
240
39
660
3,095
23%
percent
of
mobile
source
1.2%
0.2%
0.9%
0%
0.1%
0%
5%
7%
36%
6%
4%
60%
36%
6%
100%
-
-
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Table 1.5-2
Modeled Annual Emission Levels for
Mobile-Source Categories in 2020 (thousand short tons)
Category
Total for engines subject to
proposed standards
Nonroad Large SI >19 kW
Recreational SI
Recreation Marine CI
Highway Motorcycles
Marine SI Evap
Marine SI Exhaust
Nonroad SI< 19 kW
Nonroad CI
Commercial Marine CI
Locomotive
Total Nonroad
Total Highway
Aircraft
Total Mobile Sources
Total Man-Made Sources
Mobile Source percent of Total
Man-Made Sources
NOx
tons
552
486
27.0
39
14
0
58
106
1,791
819
611
3,937
2,050
232
6,219
16,195
38%
percent
of
mobile
source
9%
8%
0.40%
0.6%
0%
0.0%
0.9%
1.7%
29%
13%
10%
63%
33%
4%
100%
-
—
HC
tons
2,055
348
1,706
1
144
102
284
986
142
35
35
3,639
2,278
238
6,155
16,215
38%
percent of
mobile
source
33%
6%
28%
0%
2%
1%
5%
16%
2%
1%
1%
59%
37%
4%
100%
-
—
CO
tons
8,404
2,991
5,407
6
569
0
1,985
27,352
1,462
160
119
39,482
48,903
1,387
89,772
113,440
79%
percent of
mobile
source
9%
3%
3%
0%
1%
0%
2%
31%
2%
0.2%
0.1%
44%
54%
2%
100%
-
—
PM
tons
11.9
2.4
7.5
2
0.8
0
28
77
261
46
21
444
145
43
632
3,016
21%
percent
of
mobile
source
1.9%
0.4%
1.2%
0%
0.1%
0%
4%
12%
41%
7%
3%
70%
23%
7%
100%
-
-
1.5.2 Inventory Impacts on a Per Vehicle Basis
In addition to the general inventory contributions described above, the engines that would
be subject to the proposed standards are more potent polluters than their highway counterparts in
that they have much higher emissions on a per vehicle basis. This is illustrated in Table 1.5-3,
which equates the emissions produced in one hour of operation from the different categories of
equipment covered by the proposal to the equivalent miles of operation it would take for a car
produced today to emit the same amount of emissions.
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Chapter 1: Health and Welfare Concerns
Table 1.5-3: Per-Vehicle Emissions Comparison
Equipment Category
Recreational Marine CI
Large SI
Snowmobiles
Snowmobiles
2-Stroke ATVs & off-road motorcycles
4-Stroke ATVs & off-road motorcycles
Emission Comparison
HC+NOx
HC+NOx
HC
CO
HC
HC
Miles a Current Passenger Car Would Need
to Drive to Emit the Same Amount of
Pollution as the Equipment Category Emits
in One Hour of Operation
2,400
1,470
24,300
1,520
14,850
590
The per engine emissions are important because they mean that operators of these engines
and vehicles, as well as those who work in their vicinity, are exposed to high levels of emissions,
many of which are air toxics. These effects are of particular concern for people who operate
forklifts in enclosed areas and for snowmobile riders. These effects are described in more detail
in the next section.
1.6 Other Adverse Public Health and Welfare Effects Associated with
Nonroad Engines and Vehicles
The previous section describes national-scale adverse public health effects associated
with the nonroad engines and vehicles covered by this proposal. This section describes
significant adverse health and welfare effects arising from the usage patterns of snowmobiles,
large SI engines, and gasoline marine engines on the regional and local scale. Studies suggest
that emissions from these engines can be concentrated in specific areas, leading to elevated
ambient concentrations of particular pollutants and associated elevated personal exposures to
operators and by-standers. Recreational vehicles, and particularly snowmobiles, are typically
operating in rural areas such as national parks and wilderness areas, and emissions from these
vehicles contribute to ambient particulate matter which is a leading component of visibility
impairment. This section describes these effects. We end this section by describing two other
environmental effects of nonroad emissions: acid deposition and water eutrophication and
nitrification
1.6.1 Snowmobiles
In this section, we describe more localized human health and welfare effects associated
with snowmobile emissions: visibility impairment and personal exposure to air toxics and CO.
We describe the contribution of snowmobile HC emissions to secondary formation of fine
particles, which are the leading component of visibility impairment and adverse health effects
related to ambient PM2.5 concentrations greater than 16 //g/m3. We also discuss personal
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Draft Regulatory Support Document
exposure to CO emissions and air toxics. Gaseous air toxics are components of hydrocarbons,
and CO personal exposure measurements suggest that snowmobile riders and bystanders are
exposed to unhealthy levels of gaseous air toxics (e.g., benzene) and CO.
1.6.1.1 Nonroad Engines and Regional Haze
The Clean Air Act established special goals for improving visibility in many national
parks, wilderness areas, and international parks. In the 1977 amendments to the Clean Air Act,
Congress set as a national goal for visibility the "prevention of any future, and the remedying of
any existing, impairment of visibility in mandatory class I Federal areas which impairment
results from manmade air pollution" (CAA section 169A(a)(l)). The Amendments called for
EPA to issue regulations requiring States to develop implementation plans that assure
"reasonable progress" toward meeting the national goal (CAA Section 169A(a)(4)). EPA issued
regulations in 1980 to address visibility problems that are "reasonably attributable" to a single
source or small group of sources, but deferred action on regulations related to regional haze, a
type of visibility impairment that is caused by the emission of air pollutants by numerous
emission sources located across a broad geographic region. At that time, EPA acknowledged that
the regulations were only the first phase for addressing visibility impairment. Regulations
dealing with regional haze were deferred until improved techniques were developed for
monitoring, for air quality modeling, and for understanding the specific pollutants contributing to
regional haze.
In the 1990 Clean Air Act amendments, Congress provided additional emphasis on
regional haze issues (see CAA section 169B). In 1999 EPA finalized a rule that calls for States
to establish goals and emission reduction strategies for improving visibility in all 156 mandatory
Class I national parks and wilderness areas. In that rule, EPA also encouraged the States to work
together in developing and implementing their air quality plans. The regional haze program is
designed to improve visibility and air quality in our most treasured natural areas. At the same
time, control strategies designed to improve visibility in the national parks and wilderness areas
will improve visibility over broad geographic areas.
Regional haze is caused by the emission from numerous sources located over a wide
geographic area. Such sources include, but are not limited to, major and minor stationary
sources, mobile sources, and area sources. Visibility impairment is caused by pollutants (mostly
fine particles and precursor gases) directly emitted to the atmosphere by a number of activities
(such as electric power generation, various industry and manufacturing processes, truck and auto
emissions, construction activities, etc.). These gases and particles scatter and absorb light,
removing it from the sight path and creating a hazy condition.
Some fine particles are formed when gases emitted to the air form particles as they are
carried downwind (examples include sulfates, formed from sulfur dioxide, and nitrates, formed
from nitrogen oxides). These activities generally span broad geographic areas and fine particles
can be transported great distances, sometimes hundreds or thousands of miles. Consequently,
visibility impairment is a national problem. Without the effects of pollution a natural visual
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Chapter 1: Health and Welfare Concerns
range is approximately 140 miles in the West and 90 miles in the East. However, fine particles
have significantly reduced the range that people can see and in the West the current range is 33-
90 miles and in the East it is only 14-24 miles.
Because of evidence that fine particles are frequently transported hundreds of miles, all
50 states, including those that do not have Class I areas, will have to participate in planning,
analysis and, in many cases, emission control programs under the regional haze regulations.
Even though a given State may not have any Class I areas, pollution that occurs in that State may
contribute to impairment in Class I areas elsewhere. The rule encourages states to work together
to determine whether or how much emissions from sources in a given state affect visibility in a
downwind Class I area.
The regional haze program calls for states to establish goals for improving visibility in
national parks and wilderness areas to improve visibility on the haziest 20 percent of days and to
ensure that no degradation occurs on the clearest 20 percent of days. The rule requires states to
develop long-term strategies including enforceable measures designed to meet reasonable
progress goals. Under the regional haze program, States can take credit for improvements in air
quality achieved as a result of other Clean Air Act programs, including national mobile-source
programs.
Nonroad engines (including construction equipment, farm tractors, boats, planes,
locomotives, recreational vehicles, and marine engines) contribute significantly to regional haze.
This is because there are nonroad engines in all of the states, and their emissions contain
precursors of fine PM and organic carbon that are transported and contribute to the formation of
regional haze throughout the country and in Class I areas specifically. As illustrated in Table
1.6-1, nonroad engines are expected to contribute 15 percent of national VOC emissions, 23
percent of national NOx emissions, 6 percent of national SOx emissions, and 14 percent of
national PM10 emissions. Snowmobiles alone are estimated to emit 208,926 tons of total
hydrocarbons (THC), 1,461 tons of NOx, 2,145 tons of SOx, and 5,082 tons of PM in 2007.
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Draft Regulatory Support Document
Table 1.6-1
National Emissions of Various Pollutants - 2007
(Thousands Short Tons)
Source
Heavy-Duty
Highway
Light-Duty
Highway
Nonroad
Electric Gen.
Point
Area
TOTAL
VOC
Tons
413
2,596
2,115
35
1,639
7,466
14,265
Percent
3%
18%
15%
0
11%
52%
NOx
Tons
2,969
2,948
4,710
4,254
3,147
2,487
20,516
Percent
14%
14%
23%
21%
15%
12%
SOx
Tons
24
24
1,027
10,780
3,796
1,368
17,019
Percent
0
0
6%
63%
22%
8%
PM10
Tons
115
82
407
328
1,007
874
2,814
Percent
4%
3%
14%
12%
36%
31%
1.6.1.2 Snowmobiles and Visibility Impairment
As noted above, EPA issued regulations in 1980 to address Class I area visibility
impairment that is "reasonably attributable" to a single source or small group of sources. In 40
CFR Part 51.301 of the visibility regulations, visibility impairment is defined as "any humanly
perceptible change in visibility (light extinction, visual range, contrast, coloration) from that
which would have existed under natural conditions." States are required to develop
implementation plans that include long-term strategies for improving visibility in each class I
area. The long-term strategies under the 1980 regulations should consist of measures to reduce
impacts from local sources and groups of sources that contribute to poor air quality days in the
class I area. Types of impairment covered by these regulations includes layered hazes and visible
plumes. While these kinds of visibility impairment can be caused by the same pollutants and
processes as those that cause regional haze, they generally are attributed to a smaller number of
sources located across a smaller area. The Clean Air Act and associated regulations call for
protection of visibility impairment in class I areas from localized impacts as well as broader
impacts associated with regional haze.
Visibility and particle monitoring data are available for 8 Class I areas where
snowmobiles are commonly used. These are: Acadia, Boundary Waters, Denali, Mount Rainier,
Rocky Mountain, Sequoia and Kings Canyon, Voyageurs, and Yellowstone.77 Visibility and fine
particle data for these parks are set out in Table 1.6-2. This table shows the number of monitored
days in the winter that fell within the 20-percent haziest days for each of these eight parks.
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Chapter 1: Health and Welfare Concerns
Monitors collect data two days a week for a total of about 104 days of monitored values. Thus,
for a particular site, a maximum of 21 worst possible days of these 104 days with monitored
values constitute the set of 20-percent haziest days during a year which are tracked as the primary
focus of regulatory efforts.78 With the exception of Denali in Alaska, we defined the snowmobile
season as January 1 through March 15 and December 15 through December 31 of the same
calendar year, consistent with the methodology used in the Regional Haze Rule, which is
calendar-year based. For Denali in Alaska, the snowmobile season is October 1 to April 30.
Table 1.6-2
Winter Days That Fall Within the 20 Percent Haziest Days
At National Parks Used by Snowmobiles
NFS Unit
Acadia NP
Denali NP and Preserve
Mount Rainier NP
Rocky Mountain NP
Sequoia and Kings Canyon NP
Voyageurs NP
(1989-1992)
- Boundary Waters USFS
Wilderness Area (close to
Voyaguers with recent data)
Yellowstone NP
State(s)
ME
AK
WA
CO
CA
MN
MN
ID, MT, WY
Number of Sampled Wintertime Days
Within 20 Percent Haziest Days
(maximum of 21 sampled days)
1996
4
10
1
2
4
1989
o
6
2
0
1997
4
10
3
1
9
1990
4
5
2
1998
2
12
1
2
1
1991
6
1
0
1999
1
9
1
1
8
1992
8
5
0
Source: Letter from Debra C. Miller, Data Analyst, National Park Service, to Drew Kodjak, August 22,
2001. Docket No. A-2000-01, Document Number. II-B-28.
The information presented in Table 1.6-2 shows that visibility data supports a conclusion
that there are at least eight Class I Areas (7 in National Parks and one in a Wilderness Area)
frequented by snowmobiles with one or more wintertime days within the 20-percent haziest days
of the year. For example, Rocky Mountain National Park in Colorado was frequented by about
27,000 snowmobiles during the 1998-1999 winter. Of the monitored days characterized as
within the 20-percent haziest monitored days, two (2) of those days occurred during the
wintertime when snowmobile emissions such as hydrocarbons contributed to visibility
impairment. According to the National Park Service, "[significant differences in haziness occur
at all eight sites between the averages of the clearest and haziest days. Differences in mean
standard visual range on the clearest and haziest days fall in the approximate range of 115-170
km."79
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Ambient concentrations of fine particles are the primary pollutant responsible for
visibility impairment. Five pollutants are largely responsible for the chemical composition of
fine particles: sulfates, nitrates, organic carbon particles, elemental carbon, and crustal material.
Hydrocarbon emissions from automobiles, trucks, snowmobiles, and other industrial processes
are common sources of organic carbon. The organic carbon fraction of fine particles ranges from
47 percent in Western areas such as Denali National Park, to 28 percent in Rocky Mountain
National Park, to 13 percent in Acadia National Park.80
The contribution of snowmobiles to elemental carbon and nitrates is small. Their
contribution to sulfates is a function of fuel sulfur and is small and will decrease even more as
the sulfur content of their fuel decreases due to our recently finalized fuel sulfur requirements. In
the winter months, however, hydrocarbon emissions from snowmobiles can be significant, as
indicated in Table 1.6-3, and these HC emissions can contribute significantly to the organic
carbon fraction of fine particles which are largely responsible for visibility impairment. This is
because they are typically powered by two-stroke engines that emit large amounts of
hydrocarbons. In Yellowstone, a park with high snowmobile usage during the winter months,
snowmobile hydrocarbon emissions can exceed 500 tons per year, as much as several large
stationary sources. Other parks with less snowmobile traffic are less impacted by these
hydrocarbon emissions.81
Table 1.6-3 shows modeled tons of four pollutants during the winter season in five Class I
national parks for which we have estimates of snowmobile use. The national park areas outside
of Denali in Alaska are open to snowmobile operation in accordance with special regulations (36
CFR Part 7). Denali National Park permits snowmobile operation by local rural residents
engaged in subsistence uses (36 CFR Part 13). Emission calculations are based on an assumed 2
hours of use per snowmobile visit at 16 hp with the exception of Yellowstone where 4 hours of
use at 16 hp was assumed. The emission factors used to estimate these emissions are identical to
those used by the NONROAD model. Two-stroke snowmobile emission factors are: 111 g/hp-hr
HC, 296 g/hp-hr CO, 0.86 g/hp-hr NOx, and 2.7 g/hp-hr PM. These emission factors are based
on a number of engine tests performed by the International Snowmobile Manufacturers
Association (ISMA) and the Southwest Research Institute (SwRI). These emission factors are
still under review, and the emissions estimates may change pending the outcome of that review.
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Table 1.6-3
Winter Season Snowmobile Emissions (tons; 1999 Winter Season)
NFS Unit
Denali NP and Preserve
Grand Teton NP
Rocky Mountain NP
Voyageurs NP
Yellowstone NP
HC
>9.8
13.7
106.7
138.5
492.0
CO
>26.1
36.6
284.7
369.4
1,311.9
NOx
>0.08
0.1
0.8
1.1
3.8
PM
>0.24
0.3
2.6
3.4
12.0
Source: Letter from Aaron J. Worstell, Environmental Engineer, National Park Service, Air Resources
Division, to Drew Kodjak, August 21, 2001, particularly Table 1. Docket No. A-2000-01, Document No. II-G-178.
Inventory analysis performed by the National Park Service for Yellowstone National Park
suggests that snowmobile emissions can be a significant source of total annual mobile source
emissions for the park year round. Table 1.6-4 shows that in the 1998 winter season
snowmobiles contributed 64 percent, 39 percent, and 30 percent of HC, CO, and PM emissions.82
It should be noted that the snowmobile emission factors used to estimate these contributions are
currently under review, and the snowmobile emissions may be revised down. However, when
the emission factors used by EPA in its NONROAD model are used, the contribution of
snowmobiles to total emissions in Yellowstone is still high: 59 percent, 33 percent, and 45
percent of HC, CO and PM emissions. The University of Denver used remote-sensing
equipment to estimate snowmobile HC emissions at Yellowstone during the winter of 1998-
1999, and estimated that snowmobiles contribute 77% of annual hydrocarbon emissions at the
park.83 The portion of wintertime emissions attributable to snowmobiles is even higher, since all
snowmobile emissions occur during the winter months.
Table 1.6-4
1998 Annual HC Emissions (tpy), Yellowstone National Park
Source
Coaches
Autos
RVs
Snowmobiles
Buses
TOTAL
HC
2.69
307.17
15.37
596.22
4.96
926.4
0%
33%
2%
64%
1%
CO
24.29
2,242.12
269.61
1,636.44
18.00
4190.46
1%
54%
6%
39%
0%
NOx
0.42
285.51
24.33
1.79
13.03
325.08
0%
88%
7%
1%
4%
PM
0.01
12.20
0.90
6.07
1.07
20.25
0%
60%
4%
30%
5%
Source: National Park Service, February 2000. Air Quality Concerns Related to Snowmobile Usage in
National Parks. Air Docket A-2000-01, Document No. II-A-44.
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The information presented in this discussion indicates that snowmobiles are significant
emitters of pollutants that are known to contribute to visibility impairment in some Class I areas.
Annual and particularly wintertime hydrocarbon emissions from snowmobiles are high in the five
parks considered in Table 1.6-4, with two parks having HC emissions nearly as high as
Yellowstone (Rocky Mountain and Voyageurs). The proportion of snowmobile emissions to
emissions from other sources affecting air quality in these parks is likely to be similar to that in
Yellowstone.
1.6.1.3 Individual Air Toxics and CO Exposure
In addition to their contribution to ozone formation and CO concentrations generally,
snowmobile emissions are of concern because of their potential impacts on riders and on park
attendants, as well as other groups of people who are in contact with these vehicles for extended
periods of time.
Snowmobile users can be exposed to high air toxic and CO emissions, both because they
sit very close to the vehicle's exhaust port and because it is common for them to ride their
vehicles on groomed trails where they travel fairly close behind other snowmobiles. Because of
these riding patterns, snowmobilers breathe exhaust emissions from their own vehicle, the
vehicle directly in front as well as those farther up the trail. This can lead to relatively high
personal exposure levels of harmful pollutants. A study of snowmobile rider CO exposure
conducted at Grand Teton National Park showed that a snowmobiler riding at distances of 25 to
125 feet behind another snowmobiler and traveling at speeds from 10 to 40 mph can be exposed
to average CO levels ranging from 0.5 to 23 ppm, depending on speed and distance. The highest
CO level measured in this study was 45 ppm, as compared to the current 1-hour NAAQS for CO
of 35 ppm.84 While exposure levels can be less if a snowmobile drives 15 feet off the centerline
of the lead snowmobile, the exposure levels are still of concern. This study led to the
development of an empirical model for predicting CO exposures from riding behind
snowmobiles.
Hydrocarbon speciation for snowmobile emissions was performed for the State of
Montana in a 1997 report.85 Using the empirical model for CO from the Grand Teton exposure
study with benzene emission rates from the State of Montana's emission study, benzene
exposures for riders driving behind a single snowmobile were predicted to range from 1.2E+02 to
1.4E+03 //g/m3. Using the same model to predict exposures when riding at the end of a line of
six snowmobiles spaced 25 feet apart yielded exposure predictions of 3.5E+03, 1.9E+03,
1.3E+03, and 1.2E+03 //g/m3 benzene, at 10, 20, 30, and 40 mph, respectively.
The cancer risk posed to those exposed to benzene emissions from snowmobiles must be
viewed within the broader context of expected lifetime benzene exposure. Observed monitoring
data and predicted modeled values demonstrate that a significant cancer risk already exists from
ambient concentrations of benzene for a large portion of the US population. The Agency's 1996
National-Scale Air Toxics Assessment of personal exposure to ambient concentrations of air
toxic compounds emitted by outside sources (e.g. cars and trucks, power plants) found that
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benzene was among the five air toxics appear to pose the greatest risk to people nationwide. This
national assessment found that for approximately 50% of the US population in 1996, the
inhalation cancer risks associated with benzene exceeded 10 in one million. Modeled predictions
for ambient benzene from this assessment correlated well with observed monitored
concentrations of benzene ambient concentrations.
Specifically, the draft National-Scale Assessment predicted nationwide annual average
benzene exposures from outdoor sources to be 1.4 //g/m3.86 In comparison, snowmobile riders
and those directly exposed to snowmobile exhaust emissions had predicted benzene levels two to
three orders of magnitude greater than the 1996 national average benzene concentrations.87
These elevated levels are also known as air toxic "hot spots," which are of particular concern to
the Agency. Thus, total annual average exposures to typical ambient benzene concentrations
combined with elevated short-term exposures to benzene from snowmobiles may pose a
significant risk of adverse public health effects to snowmobile riders and those exposed to
exhaust benzene emissions from snowmobiles.
Since snowmobile riders often travel in large groups, the riders towards the back of the
group are exposed to the accumulated exhaust of those riding ahead. These exposure levels can
continue for hours at a time. An additional consideration is that the risk to health from CO
exposure increases with altitude, especially for unacclimated individuals. Therefore, a park
visitor who lives at sea level and then rides his or her snowmobile on trails at high-altitude is
more susceptible to the effects of CO than local residents.
In addition to snowmobilers themselves, people who are active in proximity to the areas
where snowmobilers congregate may also be exposed to high CO levels. An OSHA industrial
hygiene survey reported a peak CO exposure of 268 ppm for a Yellowstone employee working at
an entrance kiosk where snowmobiles enter the park. This level is greater than the NIOSH peak
recommended exposure limit of 200 ppm. OSHA's survey also measured employees' exposures
to several air toxics. Benzene exposures in Yellowstone employees ranged from 67-600 //g/m3,
with the same individual experiencing highest CO and benzene exposures. The highest benzene
exposure concentrations exceeded the NIOSH Recommended Exposure Limit of 0.1 ppm for 8-
hour exposures.88
1.6.2 Large SI Engines
Exhaust emissions from applications with significant indoor use can expose individual
operators or bystanders to dangerous levels of pollution. Forklifts, ice-surfacing machines,
sweepers, and carpet cleaning equipment are examples of large industrial spark-ignition engines
that often operate indoors or in other confined spaces. Forklifts alone account for over half of the
engines in this category. Indoor use may include extensive operation in a temperature-controlled
environment where ventilation is kept to a minimum (for example, for storing, processing, and
shipping produce).
The principal concern for human exposure relates to CO emissions. One study showed
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Draft Regulatory Support Document
several forklifts with measured CO emissions ranging from 10,000 to 90,000 ppm (1 to 9
percent).89 The threshold limit value for a time-weighted average 8-hour workplace exposure set
by the American Conference of Governmental Industrial Hygienists is 25 ppm.
One example of a facility that addressed exposure problems with new technology is in the
apple-processing field.90 Trout Apples in Washington added three-way catalysts to about 60
LPG-fueled forklifts to address multiple reports of employee health complaints related to CO
exposure. The emission standards proposed in this document are based on the same technologies
installed on these in-use engines.
Additional exposure concerns occur at ice rinks. Numerous papers have identified ice-
surfacing machines with spark-ignition engines as the source of dangerous levels of CO and NO2,
both for skaters and for spectators.91 This is especially problematic for skaters, who breathe air in
the area where pollutant concentration is highest, with higher respiration rates resulting from
their high level of physical activity. This problem has received significant attention from the
medical community.
In addition to CO emissions, HC emissions from these engines can also lead to increased
exposure to harmful pollutants, particularly air toxics. Since many gasoline or dual-fuel engines
are in forklifts that operate indoors, reducing evaporative emissions could have direct health
benefits to operators and other personnel. Fuel vapors can also cause odor problems.
1.6.3 Acid Deposition
Acid deposition, or acid rain as it is commonly known, occurs when SO2 and NOx react
in the atmosphere with water, oxygen, and oxidants to form various acidic compounds that later
fall to earth in the form of precipitation or dry deposition of acidic particles.92 It contributes to
damage of trees at high elevations and in extreme cases may cause lakes and streams to become
so acidic that they cannot support aquatic life. In addition, acid deposition accelerates the decay
of building materials and paints, including irreplaceable buildings, statues, and sculptures that are
part of our nation's cultural heritage. To reduce damage to automotive paint caused by acid rain
and acidic dry deposition, some manufacturers use acid-resistant paints, at an average cost of $5
per vehicle—a total of $61 million per year if applied to all new cars and trucks sold in the U.S.
Acid deposition primarily affects bodies of water that rest atop soil with a limited ability
to neutralize acidic compounds. The National Surface Water Survey (NSWS) investigated the
effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of
streams. It found that acid deposition was the primary cause of acidity in 75 percent of the acidic
lakes and about 50 percent of the acidic streams, and that the areas most sensitive to acid rain
were the Adirondacks, the mid-Appalachian highlands, the upper Midwest and the high elevation
West. The NSWS found that approximately 580 streams in the Mid-Atlantic Coastal Plain are
acidic primarily due to acidic deposition. Hundreds of the lakes in the Adirondacks surveyed in
the NSWS have acidity levels incompatible with the survival of sensitive fish species. Many of
the over 1,350 acidic streams in the Mid-Atlantic Highlands (mid-Appalachia) region have
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Chapter 1: Health and Welfare Concerns
already experienced trout losses due to increased stream acidity. Emissions from U.S. sources
contribute to acidic deposition in eastern Canada, where the Canadian government has estimated
that 14,000 lakes are acidic. Acid deposition also has been implicated in contributing to
degradation of high-elevation spruce forests that populate the ridges of the Appalachian
Mountains from Maine to Georgia. This area includes national parks such as the Shenandoah
and Great Smoky Mountain National Parks.
1.6.4 Eutrophication and Nitrification
Nitrogen deposition into bodies of water can cause problems beyond those associated
with acid rain. The Ecological Society of America has included discussion of the contribution of
air emissions to increasing nitrogen levels in surface waters in a recent major review of causes
and consequences of human alteration of the global nitrogen cycle in its Issues in Ecology
series.93 Long-term monitoring in the United States, Europe, and other developed regions of the
world shows a substantial rise of nitrogen levels in surface waters, which are highly correlated
with human-generated inputs of nitrogen to their watersheds. These nitrogen inputs are
dominated by fertilizers and atmospheric deposition.
Human activity can increase the flow of nutrients into those waters and result in excess
algae and plant growth. This increased growth can cause numerous adverse ecological effects
and economic impacts, including nuisance algal blooms, dieback of underwater plants due to
reduced light penetration, and toxic plankton blooms. Algal and plankton blooms can also
reduce the level of dissolved oxygen, which can also adversely affect fish and shellfish
populations. This problem is of particular concern in coastal areas with poor or stratified
circulation patterns, such as the Chesapeake Bay, Long Island Sound, or the Gulf of Mexico. In
such areas, the "overproduced" algae tends to sink to the bottom and decay, using all or most of
the available oxygen and thereby reducing or eliminating populations of bottom-feeder fish and
shellfish, distorting the normal population balance between different aquatic organisms, and in
extreme cases causing dramatic fish kills.
Collectively, these effects are referred to as eutrophication, which the National Research
Council recently identified as the most serious pollution problem facing the estuarine waters of
the United States (NRC, 1993). Nitrogen is the primary cause of eutrophi cation in most coastal
waters and estuaries.94 On the New England coast, for example, the number of red and
browntides and shellfish problems from nuisance and toxic plankton blooms have increased over
the past two decades, a development thought to be linked to increased nitrogen loadings in
coastal waters. We believe that airborne NOx contributes from 12 to 44 percent of the total
nitrogen loadings to United States coastal water bodies. For example, some estimates assert that
approximately one-quarter of the nitrogen in the Chesapeake Bay comes from atmospheric
deposition.
Excessive fertilization with nitrogen-containing compounds can also affect terrestrial
ecosystems.95 Research suggests that nitrogen fertilization can alter growth patterns and change
the balance of species in an ecosystem, providing beneficial nutrients to plant growth in areas
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Draft Regulatory Support Document
that do not suffer from nitrogen over-saturation. In extreme cases, this process can result in
nitrogen saturation when additions of nitrogen to soil over time exceed the capacity of the plants
and microorganisms to utilize and retain the nitrogen. This phenomenon has already occurred in
some areas of the U.S.
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Chapter 1: Health and Welfare Concerns
Notes to Chapter 1
1.Carbon monoxide also participates in the production of ozone, albeit at a much slower rate than
most VOC and NOx compounds.
2.U.S. EPA, 1996, Review of National Ambient Air Quality Standards for Ozone, Assessment of
Scientific and Technical Information, OAQPS Staff Paper, EPA-452/R-96-007. A copy of this
document can be obtained from Air Docket A-99-06, Document No. II-A-22.
3.U.S. EPA, 1996, Air Quality Criteria for Ozone and Related Photochemical Oxidants,
EPA/600/P-93/004aF. The document is available on the internet at
httpi//wiĄwjii^^ A copy can also be obtained from Air Docket No. A-99-
06, Documents Nos. II-A-15, II-A-16, U-A-17.
4.U.S. EPA, 1995, Review of National Ambient Air Quality Standards for Nitrogen
Dioxide, Assessment of Scientific and Technical Information, OAQPS Staff Paper,
EPA-452/R-95-005.
5.U.S.EPA, 1993, Air Quality Criteria for Oxides of Nitrogen, EP A/600/8-9 l/049aF.
6.Vitousek, Pert M., John Aber, Robert W. Howarth, Gene E. Likens, et al. 1997. Human
Alteration of the Global Nitrogen Cycle: Causes and Consequences. Issues in Ecology.
Published by Ecological Society of America, Number 1, Spring 1997.
7.National Air Quality and Emissions Trends Report, 1999, EPA, 2001, at Table A-19. This
document is available at httg^/w^^epa^goy/oar/agtrndQgA The data from the Trends report are
the most recent EPA air quality data that has been quality assured. A copy of this table can also
be found in Docket No. A-2000-01, Document No. II-A-64.
S.National Air Quality and Emissions Trends Report, 1998, March, 2000, at 28. This document
is available at http://www.epa.gov/oar/aqtrnd98/. Relevant pages of this report can be found in
Memorandum to Air Docket A-2000-01 from Jean Marie Revelt, September 5, 2001, Document
No. II-A-63.
9.National Air Quality and Emissions Trends Report, 1998, March, 2000, at 32. This document
is available at http://www.epa.gov/oar/aqtrnd98/. Relevant pages of this report can be found in
Memorandum to Air Docket A-2000-01 from Jean Marie Revelt, September 5, 2001, Document
No. II-A-63.
10. Additional information about this modeling can be found in our Regulatory Impact Analysis:
Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control
Requirements, document EPA420-R-00-026, December 2000. Docket No. 1-2000-01,
Document No. U-A-13. This document is also available at
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Draft Regulatory Support Document
11 .We also performed ozone air quality modeling for the western United States but, as described
further in the air quality technical support document, model predictions were well below
corresponding ambient concentrations for out heavy-duty engine standards and fuel sulfur control
rulemaking. Because of poor model performance for this region of the country, the results of the
Western ozone modeling were not relied on for that rule.
12. Additional information about these studies can be found in Chapter 2 of "Regulatory Impact
Analysis: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control
Requirements," December 2000, EPA420-R-00-026. Docket No. A-2000-01, Document
Number II-A-13. This document is also available at
http://www.epa.gov/otaq/diesel.htmtfdocoments.
13. Air Quality Criteria Document for Ozone and Related Photochemical Oxidants, EPA National
Center for Environmental Assessment, July 1996, Report No. EPA/600/P-93/004cF. The
document is available on the internet at hjt^7/wjvw1ega^goy^icea/ozone.htoL A copy can also be
obtained from Air Docket No. A-99-06, Documents Nos. II-A-15, II-A-16, II-A-17.
14. A copy of this data can be found in Air Docket A-2000-01, Document No.U-A-80.
15.Memorandum to Docket A-99-06 from Eric Ginsburg, EPA, "Summary of Model-Adjusted
Ambient Concentrations for Certain Levels of Ground-Level Ozone over Prolonged Periods,"
November 22, 2000. Docket A-2000-01, Document Number II-B-13.
16.Memorandum to Docket A-99-06 from Eric Ginsburg, EPA, "Summary of Model-Adjusted
Ambient Concentrations for Certain Levels of Ground-Level Ozone over Prolonged Periods,"
November 22, 2000, at Table C, Control Scenario - 2020 Populations in Eastern Metropolitan
Counties with Predicted Daily 8-Hour Ozone greater than or equal to 0.080 ppm. Docket A-
2000-01, Document Number II-B-13.
IT.National Air Quality and Emissions Trends Report, 1999, EPA, 2001, at Table A-19. This
document is available at http://www.epa.gov/oar/aqtrnd99/. The data from the Trends report are
the most recent EPA air quality data that has been quality assured. A copy of this table can also
be found in Docket No. A-2000-01, Document No. II-A-64.
18.St. Paul, Minnesota was recently reclassified as being in attainment but is still considered a
maintenance area. There is also a significant population of snowmobiles in Minnesota, with
snowmobile trails in Washington County.
19.The trail maps consulted for this proposal can be found in Docket No. A-2000-01, Document
No. II-A-65.
20. Technical Memorandum to Docket A-2000-01 from Drew Kodjak, Attorney-Advisor, Office
of Transportation and Air Quality, "Air Quality Information for Selected CO Nonattainment
Areas," July 27, 2001, Docket Number A-2000-01, Document Number U-B-18.
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Chapter 1: Health and Welfare Concerns
21. Air Quality Criteria for Carbon Monoxide, US EPA, EPA 600/P-99/001F, June 2000, at 3-
38, Figure 3-32 (Federal Bldg, AIRS Site 020900002). Air Docket A-2000-01, Document
Number II-A-29. This document is also available at http://www.epa.gov/ncea/coabstract.htm.
22. National Air Quality and Emissions Trends Report, 1998, March, 2000; this document is
available at http://www.epa.gov/oar/aqtrnd98/. National Air Pollutant Emission Trends, 1900-
1998 (EPA-454/R-00-002), March, 2000. These documents are available at Docket No. A-2000-
01, Document No. U-A-72. See also Air Quality Criteria for Carbon Monoxide, US EPA, EPA
600/P-99/001F, June 2000, at 3-10. Air Docket A-2000-01, Document Number II-A-29. This
document is also available at Mt]3://ww^^
23. LDTs are light-duty trucks greater than 3750 Ibs. loaded vehicle weight, up through 6000
gross vehicle weight rating.
24. Draft Anchorage Carbon Monoxide Emission Inventory and Year 2000 Attainment
Projections, Air Quality Program, May 2001, Docket Number A-2000-01, Document II-A-40;
Draft Fairbanks 1995-2001 Carbon Monoxide Emissions Inventory, June 1, 2001, Docket
Number A-2000-01, Document U-A-39.
25.66 FR 28836, May 25, 2001. Clean Air Act Promulgation of Attainment Date Extension for
the Fairbanks North Star Borough Carbon Monoxide Nonattainment Area, AK, Direct Final
Rule.
26.U.S. EPA, Air Quality Criteria for Carbon Monoxide, EPA 600/P-99.001F, June 2000,
Section 3.2.3. Air Docket A-2000-01, Document Number II-A-29. This document is also
available at http://www.epa.gov/ncea/coabstract.htm.
27. Air Quality and Emissions Trends Report, 1998, March, 2000. This document is available at
http://www.epa.gov/oar/aqtrnd98/. Relevant pages of this report can be found in Memorandum
to Air Docket A-2000-01 from Jean Marie Revelt, September 5, 2001, Document No. II-A-63.
28. EPA (1996) Review of the National Ambient Air Quality Standards for Parti culate Matter:
Policy Assessment of Scientific and Technical Information OAQPS Staff Paper. EPA-452/R-96-
013. Docket Number A-99-06, Documents Nos. H- A- 18, 19, 20, and 23. The parti culate matter
air quality criteria documents are also available at http ://www. gov/ncea/partmatt.htm .
29. Memorandum to Docket A-99-06 from Eric O. Ginsburg, Senior Program Advisor,
"Summary of 1999 Ambient Concentrations of Fine Particulate Matter," November 15, 2000.
This memo is also available in the docket for this rule. Docket A-2000-01, Document Number
II-B-12.
30. EPA (1996) Review of the National Ambient Air Quality Standards for Particulate Matter:
Policy Assessment of Scientific and Technical Information OAQPS Staff Paper. EPA-452/R-96-
013. Docket Number A-99-06, Documents Nos. H- A- 18, 19, 20, and 23. The parti culate matter
air quality criteria documents are also available at
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Draft Regulatory Support Document
3 1 .Memorandum to Docket A-99-06 from Eric O. Ginsburg, Senior Program Advisor,
"Summary of Absolute Modeled and Model-Adjusted Estimates of Fine Particulate Matter for
Selected Years," December 6, 2000. This memo is also available in the docket for this rule.
Docket A-2000-01, Document Number II-B-14.
32. Additional information about the Regulatory Model System for Aerosols and Deposition
(REMSAD) and our modeling protocols can be found in our Regulatory Impact Analysis: Heavy-
Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements,
document EPA420-R-00-026, December 2000. Docket No. A-2000-01, Document No. A-II-13.
This document is also available at ktt]3://www^^
33. Technical Memorandum, EPA Air Docket A-99-06, Eric O. Ginsburg, Senior Program
Advisor, Emissions Monitoring and Analysis Division, OAQPS, Summary of Absolute Modeled
and Model-Adjusted Estimates of Fine Particulate Matter for Selected Years, December 6, 2000,
Table P-2. Docket Number 2000-01, Document Number H-B-14.
34. Memo to file from Terence Fitz-Simons, OAQPS, Scott Mathias, OAQPS, Mike Rizzo,
Region 5, "Analyses of 1999 PM Data for the PM NAAQS Review," November 17, 2000, with
attachment B, 1999 PM2.5 Annual Mean and 98th Percentile 24-Hour Average Concentrations.
Docket No. A-2000-01, Document No. II-B-17.
35. The trail maps consulted for this proposal can be found in Docket No. A-2000-01, Document
No. II-A-65.
36. See our Mobile Source Air Toxics final rulemaking, 66 FR 17230, March 29, 2001, and the
Technical Support Document for that rulemaking. Docket No. A-2000-01, Documents Nos. II-
A-42 and H-A-30.
37. U.S. EPA. (1999) Analysis of the Impacts of Control Programs on Motor Vehicle Toxic
Emissions and Exposure in Urban Areas and Nationwide: Volume I. Prepared for EPA by Sierra
Research, Inc. and Radian International Corporation/Eastern Research Group, November 30,
1999. Report No. EPA420-R-99-029. http://www.epa.gov/otaq/toxics.htm.
38. U.S. EPA (1998) Environmental Protection Agency, Carcinogenic Effects of Benzene: An
Update, National Center for Environmental Assessment, Washington, DC. 1998. EPA/600/P-
97/00 1 F . http ://www. epa.gov/ncepihom/Catalog/EPA600P9700 1 F . html .
39. Leukemia is a blood disease in which the white blood cells are abnormal in type or number.
Leukemia may be divided into nonlymphocytic (granulocytic) leukemias and lymphocytic
leukemias. Nonlymphocytic leukemia generally involves the types of white blood cells
(leukocytes) that are involved in engulfing, killing, and digesting bacteria and other parasites
(phagocytosis) as well as releasing chemicals involved in allergic and immune responses. This
type of leukemia may also involve erythroblastic cell types (immature red blood cells).
Lymphocytic leukemia involves the lymphocyte type of white bloods cell that are responsible for
the immune responses. Both nonlymphocytic and lymphocytic leukemia may, in turn, be
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Chapter 1: Health and Welfare Concerns
separated into acute (rapid and fatal) and chronic (lingering, lasting) forms. For example; in
acute myeloid leukemia (AML) there is diminished production of normal red blood cells
(erythrocytes), granulocytes, and platelets (control clotting) which leads to death by anemia,
infection, or hemorrhage. These events can be rapid. In chronic myeloid leukemia (CML) the
leukemic cells retain the ability to differentiate (i.e., be responsive to stimulatory factors) and
perform function; later there is a loss of the ability to respond.
40.U.S. EPA (1985) Environmental Protection Agency, Interim quantitative cancer unit risk
estimates due to inhalation of benzene, prepared by the Office of Health and Environmental
Assessment, Carcinogen Assessment Group, Washington, DC. for the Office of Air Quality
Planning and Standards, Washington, DC., 1985. Air Docket A-2000-01, Document No. II-A-
74.
41.Clement Associates, Inc. (1991) Motor vehicle air toxics health information, for U.S. EPA
Office of Mobile Sources, Ann Arbor, MI, September 1991. Air Docket A-2000-01, Document
No. II-A-49.
42.International Agency for Research on Cancer (IARC) (1982) IARC monographs on the
evaluation of carcinogenic risk of chemicals to humans, Volume 29, Some industrial chemicals
and dyestuffs, International Agency for Research on Cancer, World Health Organization, Lyon,
France, p. 345-389.
43.Irons, R.D., W.S. Stillman, D.B. Colagiovanni, and V.A. Henry (1992) Synergistic action of
the benzene metabolite hydroquinone on myelopoietic stimulating activity of
granulocyte/macrophage colony-stimulating factor in vitro, Proc. Natl. Acad. Sci. 89:3691-3695.
44.Lumley, M., H. Barker, and J.A. Murray (1990) Benzene in petrol, Lancet 336:1318-1319.
45.U.S. EPA (1993) Motor Vehicle-Related Air Toxics Study, U.S. Environmental Protection
Agency, Office of Mobile Sources, Ann Arbor, MI, EPA Report No. EPA 420-R-93-005, April
1993.
46.Pancytopenia is the reduction in the number of all three major types of blood cells
(erythrocytes, or red blood cells, thrombocytes, or platelets, and leukocytes, or white blood cells).
In adults, all three major types of blood cells are produced in the bone marrow of the vertebra,
sternum, ribs, and pelvis. The bone marrow contains immature cells, known as multipotent
myeloid stem cells, that later differentiate into the various mature blood cells. Pancytopenia
results from a reduction in the ability of the red bone marrow to produce adequate numbers of
these mature blood cells.
47.Aksoy, M (1991) Hematotoxicity, leukemogenicity and carcinogenicity of chronic exposure
to benzene. In: Arinc, E.; Schenkman, J.B.; Hodgson, E., Eds. Molecular Aspects of
Monooxygenases and Bioactivation of Toxic Compounds. New York: Plenum Press, pp. 415-
434.
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Draft Regulatory Support Document
48.Goldstein, B.D. (1988) Benzene toxicity. Occupational medicine. State of the Art Reviews.
3: 541-554.
49. Aplastic anemia is a more severe blood disease and occurs when the bone marrow ceases to
function, i.e.,these stem cells never reach maturity. The depression in bone marrow function
occurs in two stages - hyperplasia, or increased synthesis of blood cell elements, followed by
hypoplasia, or decreased synthesis. As the disease progresses, the bone marrow decreases
functioning. This myeloplastic dysplasia (formation of abnormal tissue) without acute
leukemiais known as preleukemia. The aplastic anemia can progress to AML (acute mylogenous
leukemia).
SO.Aksoy, M., S. Erdem, and G. Dincol. (1974) Leukemia in shoe-workers exposed chronically
to benzene. Blood 44:837.
Sl.Aksoy, M. and K. Erdem. (1978) A follow-up study on the mortality and the development of
leukemia in 44 pancytopenic patients associated with long-term exposure to benzene. Blood 52:
285-292.
52.Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E. Marti, Y.Z. Wang, M. Linet, L.Q.
Xi, W. Lu, M.T. Smith, N. Titenko-Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes
(1996) Hematotoxicity among Chinese workers heavily exposed to benzene. Am. J. Ind. Med.
29: 236-246.
53.U.S. EPA. (1999) Analysis of the Impacts of Control Programs on Motor Vehicle Toxic
Emissions and Exposure in Urban Areas and Nationwide: Volume I. Prepared for EPA by Sierra
Research, Inc. and Radian International Corporation/Eastern Research Group, November 30,
1999. Report No. EPA420-R-99-029. http://www.epa.gov/otaq/toxics.htm.
54.U.S. EPA (1985) Mutagenicity and Carcinogenicity Assessment of 1,3-Butadiene.
EPA/600/8-85/004F. U.S. Environmental Protection Agency, Office of Health and
Environmental Assessment. Washington, DC.
55.U.S. EPA (1998) Draft Health Risk Assessment of 1,3-Butadiene, National Center for
Environmental Assessment, Office of Research and Development, U.S. EPA, EPA/600/P-
98/001 A, February 1998.
56. Scientific Advisory Board. 1998. An SAB Report: Review of the Health Risk Assessment of
1,3-Butadiene. EPA-SAB-EHC-98, August, 1998.
57.EPA 1996. Proposed guidelines for carcinogen risk assessment. Federal Register
61(79):17960-18011.
58.U.S. EPA (1985) Mutagenicity and carcinogenicity assessment of 1,3-butadiene. EPA/600/8-
85/004F. U.S. Environmental Protection Agency, Office of Health and Environmental
Assessment. Washington, DC. http://www.epa.gov/ngispgm3/iris/subst/0139.htm.
1-42
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Chapter 1: Health and Welfare Concerns
59.U.S. EPA (1985) Mutagenicity and carcinogenicity assessment of 1,3-butadiene. EPA/600/8-
85/004F. U.S. Environmental Protection Agency, Office of Health and Environmental
Assessment. Washington, DC. http://www.epa.gov/ngispgm3/iris/subst/0139.htm.
60.Ligocki, M.P., G.Z. Whitten, R.R. Schulhof, M.C. Causley, and G.M. Smylie (1991)
Atmospheric transformation of air toxics: benzene, 1,3-butadiene, and formaldehyde, Systems
Applications International, San Rafael, CA (SYSAPP-91/106).
61.U.S. EPA (1987) Environmental Protection Agency, Assessment of health risks to garment
workers and certain home residents from exposure to formaldehyde, Office of Pesticides and
Toxic Substances, April 1987. Air Docket A-2000-01, Document No. II-A-48.
62.Clement Associates, Inc. (1991) Motor vehicle air toxics health information, for U.S. EPA
Office of Mobile Sources, Ann Arbor, MI, September 1991. Air Docket A-2000-01, Document
No. II-A-49.
63.U.S. EPA (1993) Motor Vehicle-Related Air Toxics Study, U.S. Environmental Protection
Agency, Office of Mobile Sources, Ann Arbor, MI, EPA Report No. EPA 420-R-93-005, April
1993. http://www.epa.gov/otaq/toxics.htm.
64.Wilhelmsson, B. and M. Holmstrom. (1987) Positive formaldehyde PAST after prolonged
formaldehyde exposure by inhalation. The Lancet:l64.
65.Burge, P.S., M.G. Harries, W.K. Lam, I.M. O'Brien, and P.A. Patchett. (1985) Occupational
asthma due to formaldehyde. Thorax 40:225-260.
66.Hendrick, D.J., RJ. Rando, DJ. Lane, and MJ. Morris (1982) Formaldehyde asthma:
Challenge exposure levels and fate after five years. J. Occup. Med. 893-897.
67.Nordman, H., H. Keskinen, and M. Tuppurainen. (1985) Formaldehyde asthma - rare or
overlooked? J. Allergy din. Immunol. 75:91-99.
68.U.S. EPA. (1999) Analysis of the Impacts of Control Programs on Motor Vehicle Toxic
Emissions and Exposure in Urban Areas and Nationwide: Volume I. Prepared for EPA by Sierra
Research, Inc. and Radian International Corporation/Eastern Research Group, November 30,
1999. Report No. EPA420-R-99-029. http://www.epa.gov/otaq/toxics.htm
69.Ligocki, M.P., G.Z. Whitten (1991) Atmospheric transformation of air toxics: acetaldehyde
and polycyclic organic matter, Systems Applications International, San Rafael, CA, (SYSAPP-
91/113).
70. Environmental Protection Agency, Health assessment document for acetaldehyde, Office of
Health and Environmental Assessment, Environmental Criteria and Assessment Office, Research
Triangle Park, NC, EPA-600/8-86/015A (External Review Draft), 1987. Air Docket A-2000-01,
Document No. II-A-33.
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Draft Regulatory Support Document
71. Environmental Protection Agency, Integrated Risk Information System (IRIS), Office of
Health and Environmental Assessment, Environmental Criteria and Assessment Office,
Cincinnati, OH, 1992. Acetaldehyde. http ://www. gov/iri st/0290
72. U.S. EPA (1987) Health Assessment Document for Acetaldehyde — External Review Draft.
Office of Health and Environmental Assessment, Research Triangle Park, NC. Report No. EPA
600/8-86/0 15 A.
73. California Air Resources Board (CARB) (1992) Preliminary Draft: Proposed identification of
acetaldehyde as a toxic air contaminant, Part B Health assessment, California Air Resources
Board, Stationary Source Division, August, 1992. Air Docket A-2000-01, Document No. II-A-
34.
74. U.S. EPA (1997) Environmental Protection Agency, Integrated Risk Information System
(IRIS), Office of Health and Environmental Assessment, Environmental Criteria and Assessment
Office, Cincinnati, OH, 1997. Acetaldehyde. jrtt]3i//wwwj;p^^
75. U.S. EPA (1999) Environmental Protection Agency, Integrated Risk Information System
(IRIS), Office of Health and Environmental Assessment, Environmental Criteria and Assessment
Office, Cincinnati, OH. 1,3 -Butadiene, http://www.epa.gov/iris/subst/0139.htm .
76. U.S. EPA (1993) Environmental Protection Agency, Integrated Risk Information System
(IRIS), Office of Health and Environmental Assessment, Environmental Criteria and Assessment
Office, Cincinnati, OH. Acrolein
77. No data was available at five additional parks where snowmobiles are also commonly used:
Black Canyon of the Gunnison, CO, Grand Teton, WY, Northern Cascades, WA, Theodore
Roosevelt, ND, and Zion, UT.
78.Letter from Debra C. Miller, Data Analyst, National Park, to Drew Kodjak, August 22, 2001.
Docket No. A-2000-01, Document Number. II-B-28.
79. Letter from Debra C. Miller, Data Analyst, National Park Service, to Drew Kodjak, August
22, 2001. Docket No. A-2000-01, Document. Number. H-B-28.
80. Letter from Debra C. Miller, Data Analyst, National Park Service, to Drew Kodjak, August
22, 2001. Docket No. A-2000-01, Document Number. II-B-28.
81. Technical Memorandum, Aaron Worstell, Environmental Engineer, National Park Service,
Air Resources Division, Denver, Colorado, particularly Table 1. Docket No. A-2000-01,
Document Number D-G-178.
82.National Park Service, February 2000. Air Quality Concerns Related to Snowmobile Usage
in National Parks. Air Docket A-2000-01, Document No. H-A-44.
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Chapter 1: Health and Welfare Concerns
83.G. Bishop, et al., Snowmobile Contributions to Mobile Source Emissions in Yellowstone
National Park, Environmental Science and Technology, Vol. 35, No. 14, at 2873. Docket No. A-
2000-01, Document No. II-A-47.
84. Snook and Davis, 1997, "An Investigation of Driver Exposure to Carbon Monoxide While
Traveling Behind Another Snowmobile." Docket No. A-2000-01, Document Number II-A-35.
85. Emissions from Snowmobile Engines Using Bio-based Fuels and Lubricants, Southwest
Research Institute, August, 1997, at 22. Docket No. A-2000-01, Document Number II-A-50.
86. National-Scale Air Toxics Assessment for 1996, EPA-453/R-01-003, Draft, January 2001.
87. Technical Memorandum, Chad Bailey, Predicted benzene exposures and ambient
concentrations on and near snowmobile trails, August 17, 2001. Air Docket A-2000-01,
Document No. U-B-27.
88.U.S. Department of Labor, OSHA, Billings Area Office, "Industrial Hygiene Survey of Park
Employee Exposures During Winter Use at Yellowstone National Park, February 19 through
February 24, 2000. Docket No. A-2000-01, Document Number II-A-37; see also Industrial
Hygiene Consultation Report prepared for Yellowstone National Park by Tim Radtke, CUT,
Industrial Hygienist, June 1997. Docket A-2000-01, Document No. A-II-41.
89."Warehouse Workers' Headache, Carbon Monoxide Poisoning from Propane-Fueled
Forklifts," Thomas A. Fawcett, et al, Journal of Occupational Medicine., January 1992, p. 12.
Docket A-2000-01, Document No. II-A-36.
90."Terminox System Reduces Emissions from LPG Lift Trucks," Material Handling Product
News. Docket A-2000-01, Document No. II-A-14.
91. Summary of Medical Papers Related to Exhaust Emission Exposure at Ice Rinks," EPA
Memorandum from Alan Stout to Docket A-2000-01. Docket A-2000-01, Document No. II-A-
38.
92.Much of the information in this subsection was excerpted from the EPA document, Human
Health Benefits from Sulfate Reduction, written under Title IV of the 1990 Clean Air Act
Amendments, U.S. EPA, Office of Air and Radiation, Acid Rain Division, Washington, DC
20460, November 1995. Air Docket A-2000-01, Document No. U-A-32.
93.Vitousek, Peter M., John Aber, Robert W. Howarth, Gene E. Likens, et al. 1997. Human
Alteration of the Global Nitrogen Cycle: Causes and Consequences. Issues in Ecology. Published
by Ecological Society of America, Number 1, Spring 1997.
94.Much of this information was taken from the following EPA document: Deposition of Air
Pollutants to the Great Waters-Second Report to Congress, Office of Air Quality Planning and
Standards, June 1997, EPA-453/R-97-011.
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Draft Regulatory Support Document
95.Terrestrial nitrogen deposition can act as a fertilizer. In some agricultural areas, this effect can
be beneficial.
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Chapter 1: Health and Welfare Concerns
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Chapter 2: Industry Characterization
CHAPTER 2: Industry Characterization
To accurately assess the potential impact of this emission control program, it is important
to understand the nature of the affected industries. This chapter describes relevant background
information related to each of the categories of engines subject to this proposal.
2.1 Marine
This section gives a general characterization of the segments of the marine industry that
may be impacted by the proposed regulations. For this discussion, we divide the recreational
marine industry into twi segments: compression-ignition (CI) diesel engine manufacturers and
boat builders. This industry characterization was developed in part under contract with ICF
Consulting1 as well as independent analyses conducted by EPA through interaction with the
industry and other sources.2'3'4
2.1.1 Marine Diesel Engine Manufacturers
2.1.1.1 Identification of Diesel Engine Manufacturers
We have determined that there are at least 16 companies that manufacture CI marine
engines for recreational vessels. Nearly 75 percent of diesel engines sales for recreational vessels
in 2000 can be attributed to three large companies. Six of the identified companies are
considered small businesses as defined by the Small Business Administration SIC code 3519
(less than 1000 employees). Based on sales estimates for 2000, these six companies represent
approximately 4 percent of recreational marine diesel engine sales. The remaining companies
each comprise between two and seven percent of sales for 2000. Table 2.1-1 provides a list of
the diesel engine manufacturers identified to date by EPA.
Table 2.1-1 List of CI Marine Engine Manufacturers Identified by EPA
Greater than 1000 employees
Less than 1000 employees
Caterpillar
Cummins
Detroit Diesel
Isotta Fraschini
John Deere
Marine Corporation of America
Mercruiser
MTU
Volvo Penta
Yanmar
Alaska Diesel/Lugger
American Diesel
Daytona Marine
Marine Power
Peninsular Diesel
Westerbeke
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Draft Regulatory Support Document
2.1.1.2 Use of Diesel Engines
Diesel engines are primarily available in inboard marine configurations, but may also be
available in sterndrive and outboard marine configurations. Inboard diesel engines are the
primary choice for many larger recreational boats.
Larger boats are powered exclusively by diesel inboard engines. These boats are
generally 40 feet or greater in length. Recreational boats in ports with access to the ocean (e.g.
Seattle) can be 80 to 100 feet or longer. The larger boats typically require twin inboard diesel
engines with 2,000 total horsepower or more. Recreational diesel marine engines are generally
produced by domestic companies that have been long-standing players in the marine diesel
engine market. The three companies that tend to dominate the market are Caterpillar, Cummins,
and Detroit Diesel. As mentioned above, nearly 75 percent of diesel engines sales for recreational
vessels in 2000 can be attributed to these three companies.
Sterndrive diesel engines account for less than 1 or 2 percent of the market. A minority
of mid-sized boat owners insist on diesel powered sterndrive engines for their boats. Diesel
marine sterndrive systems generally power the same types of boats as their gasoline counterparts,
which tend to be 15 to 30 feet in length. Customers that choose a diesel sterndrive marine
engine are generally seeking three main advantages over gasoline sterndrive marine engines.
First, diesel fumes are much less ignitable and explosive that gasoline fumes. Second, diesel
powered craft have a greater range than gasoline powered craft with similar fuel capacity. Lastly,
diesel engines tend to be more reliable and tend to run more hours between major overhauls than
gasoline engines. This last point is particularly important to boat owners who operate their boats
higher than the average.
One major disadvantage of diesel sterndrive engines is their cost relative to comparably
powered gasoline sterndrive engines. For example, a 40 foot twin cabin cruiser with twin
gasoline sterndrive engines costs $238,000. For twin diesel sterndrive engines, the price
increases approximately $50,000. The fact that the diesel engine is more expensive, coupled
with the fact that diesel fuel is often less available than gasoline in the U.S., has resulted in
limited domestic demand for recreational diesel sterndrive marine engines.
2.1.1.3 Current Trends
The strong economy of the mid-1990's, the rapid growth of the stock market, and the
gains in personal disposable personal income have combined to accelerate big ticket purchases,
including the purchases of large boats. For example, from 1995 to 1997, inboard cruiser diesel
marine sales have increased by 15 percent according to data collected by ICF. In addition to
positive economic conditions, favorable financing, low fuel costs, product advancement and
recent model design changes have also lead to increased sales of larger boats.
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Chapter 2: Industry Characterization
2.1.2 Recreational Boat Builders
2.1.2.1 Identification of Boat Builders
We have less precise information about recreational boat builders than is available about
engine manufacturers. We used several sources, including trade associations and Internet sites
when identifying entities that build and/or sell recreational boats. We have also worked with an
independent contractor to assist in the characterization of this segment of the industry. Finally,
we have obtained a list of nearly 1,700 boat builders known to the U.S. Coast Guard to produce
boats using recreational gasoline and diesel engines. At least 1,200 of these companies install
gasoline-fueled engines and would therefore be subject to the proposed evaporative emission
standards. More that 90 percent of the companies identified so far would be considered small
businesses as defined by SBA SIC code 3732.
Based on information supplied by a variety of recreational boat builders, fuel tanks for
recreational boats are usually purchased from fuel tank manufacturers. However, some boat
builders construct their own fuel tanks. The boat builder provides the specifications to the fuel
tank manufacturer who helps match the fuel tank for a particular application. It is the boat
builder's responsibility to install the fuel tank and connections into their vessel design. For
vessels designed to be used with small outboard engines, the boat builder may not install a fuel
tank; therefore, the end user would use a portable fuel tank with a connection to the engine.
2.1.2.2 Current Trends
Additional information provided by NMMA indicate that an estimated 72 million people
participated in recreational boating in 2000, which is down slightly from 77 million in 1995. In
2000, nearly 17 million boats were in use in the United States.
2.1.2.3 Production Practices
Based on information supplied by a variety of recreational boat builders, the following
discussion provides a description of the general production practices used in this sector of the
marine industry.
Engines are usually purchased from factory authorized distribution centers. The boat
builder provides the specifications to the distributor who helps match an engine for a particular
application. It is the boat builders responsibility to fit the engine into their vessel design. The
reason for this is that sales directly to boat builders are a very small part of engine manufacturers'
total engine sales. These engines are not generally interchangeable from one design to the next.
Each recreational boat builder has their own designs. In general, a boat builder will design one
or two molds that are intended to last 5-8 years. Very few changes are tolerated in the molds
because of the costs of building and retooling these molds.
Recreational vessels are designed for speed and therefore typically operate in a planing
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Draft Regulatory Support Document
mode. To enable the vessel to be pushed onto the surface of the water where it will subsequently
operate, recreational vessels are constructed of lighter materials and use engines with high power
density (power/weight). The tradeoff on the engine side is less durability, and these engines are
typically warranted for fewer hours of operation. Fortunately, this limitation typically
corresponds with actual recreational vessel use. With regard to design, these vessels are more
likely to be serially produced. They are generally made out of light-weight fiberglass. This
material, however, minimizes the ability to incorporate purchaser preferences, not only because
many features are designed into the fiberglass molds, but also because these vessels are very
sensitive to any changes in their vertical or horizontal centers of gravity. Consequently, optional
features are generally confined to details in the living quarters, and engine choice is very limited
or is not offered at all.
2.2 Large Industrial SI Equipment
Large SI engines are those spark-ignition nonroad engines that have rated power higher
than 25 horsepower, that are not recreational engines or marine engines. They are typically
derivatives of automotive engines, but use less advanced technology. The most common
application of these engines is in forklifts. Other applications include generators, pumps,
compressors, and a wide variety of other applications.
2.2.1 Manufacturers
There are seven principal manufacturers of Large SI engines. Table 2.2-1 shows that
sales volumes are relatively evenly distributed among these seven manufacturers. This sales
information is based on average annual volumes for the period from 1994 through 1996. Where
marketing data from individual companies did not agree with the published figures, the analysis
adjusts the estimated figures to improve the accuracy of historical sales volumes. The figures for
"other" manufacturers presents aggregated data from four additional companies—Volkswagen,
Westerbeke, Hercules, and Chrysler. While these and other numbers in this chapter may be
changing somewhat over the recent and coming years, they provide a good indication of the
nature of this industry segment.
The degree to which engine manufacturers offer integrated engine and equipment models
is an important factor in determining how companies address the need to redesign their products.
Companies that use their own engine models to produce equipment have the advantage of
coordinating the engine design changes with the appropriate changes in their equipment models.
The principal integrated manufacturers (Nissan, Mitsubishi, and Toyota) all produce forklifts.
About 30 percent of Large SI equipment sales are from integrated manufacturers.
Other forklift manufacturers have also been responsible for varying degrees of engine
design. Engine design expertise among these companies is so prevalent that some forklift
manufacturers may assume responsibility for certifying their engines, even though they buy the
engines mostly assembled from other manufacturers.
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Chapter 2: Industry Characterization
Table 2.2.-1
Engine Sales by Manufacturer
Manufacturer
General Motors
Mitsubishi Motors
Ford Power Products
Nissan Industrial Engines
Wis-Con Total Power
Toyota
Mazda
Other
Total
Average
Annual Sales
19,500
15,600
14,000
13,800
12,100
11,800
8,200
7,200
102,300
Distribution
19%
15%
14%
13%
12%
12%
8%
6%
100%
2.2.2 Applications
We have also estimated populations of engine and equipment models using historical
sales information adjusted according to survival and scrappage rates. Table 2-2 presents the
estimated U.S. population of the various Large SI equipment applications. A recent, commercial
study of the forklift market showed the need to adjust forklift population estimates.5 That study
identified a 1996 population of 491,321 engine-powered forklifts (Classes 4, 5, and 6),
estimating that 80 percent of all forklifts operate on liquefied petroleum gas (LPG), with the rest
running on either gasoline or diesel fuel.a With an estimated even split between gasoline and
diesel for these remaining forklifts, we estimate a total population of spark-ignition forklifts of
442,000. This spark-ignition population includes all units operating on gasoline and LPG; a
small number of spark-ignition forklifts are fueled by natural gas.
For other applications, the split between LPG and gasoline also warrants further attention.
Large SI engines today are typically sold without fuel systems, which makes it difficult to assess
the distribution of engine sales by fuel type. Also, engines are often retrofitted for a different fuel
after the initial sale, making it still more difficult to estimate the prevalence of the different fuels.
The high percentage of propane systems for forklifts can be largely attributed to expenses related
to maintaining fuel supplies. LPG cylinders can be readily exchanged with minimal infrastruc-
ture cost. Installing and maintaining underground tanks for storing gasoline has always been a
significant expense, which has become increasingly costly due to the new requirements for
replacing underground tanks.
aMolecular propane (C3H8) is the most common constituent in LPG. LPG is therefore
commonly referred to as propane.
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Draft Regulatory Support Document
Natural gas is a third fuel option. While natural gas and LPG fuel systems are very
similar, natural gas installations are much less common in Large SI engines. Natural gas supply
systems typically offer the advantage of pipeline service, but the cost of installing high-pressure
refueling equipment is an obstacle to increased use of natural gas.
Some applications of nonroad SI equipment face much different refueling situations.
Lawn and garden equipment is usually not centrally fueled and therefore operates almost
exclusively on gasoline, which is more readily available. Agriculture equipment is predomi-
nantly powered by diesel engines. Most agriculture operators have storage tanks for diesel fuel.
Those who use spark-ignition engines in addition to, or instead of, the diesel models, would
likely invest in gasoline storage tanks as well, resulting in little or no use of LPG or natural gas
for those applications. For construction, general industrial, and other nonroad equipment, there
may be a mix of central and noncentral fueling, and motive and portable equipment; we therefore
believe that estimating an even mix of LPG and gasoline for these engines is most appropriate.
The estimated distribution of fuel types for the individual applications are listed in Table 2-2.
An additional issue related to population figures is the level of growth factored into
emission estimates for the future. EPA's Nonroad Emission Model incorporates application-
specific growth figures. The projected growth is reflected in the population estimates included in
Table 2.2-2.
Table 2.2-2
Operating Parameters and Population Estimates for
Various Applications of Engines Rated above 19 kW
Application*
Forklift
Generator
Welder
Commercial turf
Pump
Air compressor
Baler
Irrigation set
Aerial lift
Scrubber/sweeper
Chipper/grinder
Leaf blower/vacuum
Load Factor
0.30
0.68
0.51
0.60
0.69
0.56
0.62
0.60
0.46
0.71
0.78
0.75
Usage Rate
(hours/yr)
1500
115
208
733
221
484
68
716
361
516
488
56
1996
Population
442,000
205,990
55,495
41,440
41,104
24,182
21,937
17,800
15,734
14,154
12,218
10,823
Projected 20 10
Population
547,063
202,177
67,872
55,074
44,830
28,633
27,597
9,724
15,555
13,955
16,262
14,384
Percent
LPG/CNG
95
50
50
0
50
50
0
50
50
50
50
0
2-6
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Chapter 2: Industry Characterization
Application*
Oil field equipment
Sprayer
Trencher
Specialty vehicle/cart
Skid/steer loader
Other general industrial
Rubber-tired loader
Gas compressor
Paving equipment
Terminal tractor
Bore/drill rig
Ag. tractor
Concrete/industrial saw
Rough terrain forklift
Roller
Crane
Other material handling
Paver
Other agriculture equipment
Other construction
Pressure washer
Aircraft support
Crushing/processing equip
Surfacing equipment
Tractor/loader/backhoe
Hydraulic power unit
Other lawn & garden
Refrigeration/AC
Load Factor
0.90
0.65
0.66
0.58
0.58
0.54
0.71
0.60
0.59
0.78
0.79
0.62
0.78
0.63
0.62
0.47
0.53
0.66
0.55
0.48
0.85
0.56
0.85
0.49
0.48
0.56
0.58
0.46
Usage Rate
(hours/yr)
1104
80
402
65
310
713
512
8500
175
827
107
550
610
413
621
415
386
392
124
371
115
681
241
488
870
450
61
605
1996
Population
8,792
8,635
8,168
7,833
7,795
3,987
3,476
3,023
2,996
2,905
2,618
2,152
2,133
1,933
1,596
1,584
1,535
1,337
1,234
1,222
1,207
840
532
481
416
339
333
163
Projected 20 10
Population
8,924
10,863
9,604
8,726
9,164
3,942
4,088
1,620
3,524
2,872
3,080
2,707
2,509
2,273
1,878
1,864
1,518
1,573
1,552
1,436
2,271
1,238
628
567
489
384
443
226
Percent
LPG/CNG
100
0
50
50
50
50
50
100
50
50
50
0
50
50
50
50
50
50
0
50
50
50
50
50
50
50
0
100
*The list of applications and the associated load factors and usage rates are from PSR. The population figures and the
distribution of fuel types are from the EPA's Nonroad Model.
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2.2.3 Engine Design and Operation
Most engines operate at a wide variety of speeds and loads, such that operation at rated
power (full-speed and full-load) is rare. To take into account the effect of operating at idle and
partial load conditions, a load factor indicates the degree to which average engine operation is
scaled back from full power. For example, at a 0.3 (or 30 percent) load factor, an engine rated at
100 hp would be producing an average of 30 hp over the course of normal operation. For many
nonroad applications, this can vary widely (and quickly) between 0 and 100 percent of full
power. Table 2-2 shows the load factors that apply to each nonroad equipment application.
Table 2-2 also shows annual operating hours that apply to the various applications. These
figures represent the operating levels that apply through the median lifetime of equipment.
2.2.3.1 Automotive-Derived Engines
The majority of Large SI engines are industrial versions of automotive engines.
Tables 2.2-3 and 2.2-4 show that four-cylinder engines rated under 100 horsepower dominate the
market. There are also substantial niche markets available for smaller and larger engines. In the
absence of emission standards, there has been limited transfer of emission-control technology
from automotive to industrial engines.
Producing an industrial version of an automotive engine typically involves fitting a
common engine block with less expensive systems and components appropriate for nonroad use.
Manufacturers remove most of the sophisticated systems in place for the high-performance, low-
emission automotive engines to be able to produce the industrial engine at a lower cost. For
example, while cars have used electronic fuel systems for many years, almost all industrial
engines still rely on mechanical fuel systems. Chapter 3 describes the baseline and projected
engine technologies in greater detail.
Table 2.2-3
Power Distribution
Power Rating
25 < HP < 49
50 < HP < 99
100 < HP < 174
HP > 174
Total
Average
Annual Sales
34,400
47,300
19,000
1,600
102,300
Distribution
34%
46%
19%
2%
100%
2-8
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Chapter 2: Industry Characterization
Table 2.2-4
Engine Sizes
Number of
Cylinders
1
2
3
4
6
8
Total
Average
Annual Sales
100
500
7,000
78,100
10,700
6,000
102,300
Distribution
0.1%
0.4%
7%
76%
11%
6%
100%
2.2.3.2 Air-Cooled Engines
Some manufacturers produce engines exclusively for industrial use, most of which are
air-cooled models. Air-cooled engines with less than one liter total displacement are typically
very similar to the engines used in lawn and garden applications. Total sales of air-cooled
engines over one liter are about 9,200 per year, 85 percent of which are rated under 50 hp. While
these engines can use the same emission-control technologies as water-cooled engines, they have
unique constraints on how well they control emissions. Air-cooling doesn't cool the engine
block as uniformly as water-cooling. This uneven heating can lead to cylinder-to-cylinder
variations that make it difficult to optimize fuel and air intake variables consistently. Uneven
heating can also distort cylinders to the point that piston rings don't consistently seal the
combustion chamber. Finally, the limited cooling capacity requires that air-cooled engines stay
at fuel-rich conditions when operating near full power.
While air-cooled engines account for about 9 percent of Large SI engine sales, their use is
concentrated in a few specialized applications. Almost all of these are portable (non-motive)
applications with engine operation at constant speeds (the speed setting may be adjustable, but
operation at any given time is at a single speed). Many applications, such as concrete saws and
chippers, expose the engine to high concentrations of ambient particles that may reduce an
engine's lifetime. These particles would also form deposits on radiators, making water-cooling
less effective. Because lower-emitting water-cooled engines may not be suitable alternatives in
these severe-duty applications, the proposed emission standards take into account the technology
constraints of air-cooled engines.
2.2.4 Customer Concerns
Most Large SI engines are used in industrial applications. These industrial customers
have historically been most concerned about the cost of the engine and equipment, and about
reliability. In many cases, the customer values consistent and familiar technology as a means of
2-9
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Draft Regulatory Support Document
simplifying engine maintenance. As described in Chapter 5, equipment users have largely
ignored the potential for improving fuel economy in making purchasing decisions. As a result
most Large SI engines being sold today have relatively simple carburetor technology that is
similar to automotive technology of the early 1980s.
There is a large subset of these engines that are operated indoors or in other areas with
restricted airflow much of the time. For these indoor engines, customers have generally wanted
engines with lower CO emissions. Thus most indoor engines are fueled with LPG or CNG. In
some cases, where the customer wants even lower emissions, they will purchase engines
equipped with exhaust catalysts.
2.3 Snowmobiles
Snowmobiles are normally one or two passenger vehicles that are used to traverse over
snow-covered terrain. They have a track in the rear similar to that of a bulldozer, and runners
(similar to skis) in the front for steering. Snowmobiles are used primarily for recreational
purposes. However, a small number of them are produced and used for utility purposes, such as
search and rescue operations. Annual snowmobile sales in the U.S. have varied dramatically
over the years, but sales between 1996 and 2000 have averaged about 157,000 units per year.
2.3.1 Manufacturers
Manufacturers of snowmobiles are classified under the North American Industrial
Classification Code System (NAICS) as code 336999, Other Transportation Equipment
Manufacturing. These codes are used by the Small Business Administration (SBA) in classifying
businesses as large or small, depending on the number of employees. Snowmobile
manufacturers have the NAICS subclassification 3369993414, and must have fewer than 500
employees to be considered a small business.
There are four major manufacturers of snowmobiles which account for almost the entire
U.S. snowmobile market. These manufacturers are Arctic Cat, Bombardier (Ski-Doo), Polaris
and Yamaha. Polaris is the largest snowmobile manufacturer, by sales volume, followed by
Arctic Cat, Bombardier and Yamaha. There are less than five small snowmobile manufacturers
that combined make up significantly less than one percent of the U.S. snowmobile market.
These small manufacturers specialize in high performance snowmobiles and other unique designs
(such as stand-up snowmobiles).
2.3.2 Sales and Fleet Size
Snowmobile sales tend to vary both with the state of the U.S. economy (being a
discretionary recreational purchase) and snowfall. Thus, annual sales have varied, sometimes
dramatically, over the years. Table 2.3.-1 shows annual U.S. snowmobile sales from 1992
through 2000, as reported by the International Snowmobile Manufacturers Association. The
current snowmobile fleet in the U.S. is roughly 1.5 million units.
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Chapter 2: Industry Characterization
Table 2.3.-1
U.S. Snowmobile Sales
Year
2000
1999
1998
1997
1996
1995
1994
1993
1992
Unit Sales
136,601
147,867
162,826
170,325
168,509
148,207
114,057
87,809
81,946
2.3.3 Usage
There are a variety of snowmobile types currently produced and tailored to a variety of
riding styles. The majority of the snowmobile market is made up of high performance machines.
These snowmobiles have fairly high powered engines and are very light, giving them good
acceleration, speed and handling. The performance sleds come in several styles. Cross country
sleds are designed for aggressive trail and cross country riding. Mountain sleds have longer
tracks and a wider runner stance for optimum performance in mountainous terrain. Finally,
muscle sleds are designed for high top speeds (in excess of 120 miles per hour) over flat terrain
such as frozen lakes. Performance snowmobiles are generally designed for a single rider.
The second major style of snowmobile is designed for casual riding over groomed trails.
These touring sleds are designed for one or two riders, and tend to have lower powered engines
than performance snowmobiles. The emphasis in this market segment is more on comfort and
convenience. As such, these sleds feature a more comfortable ride than the performance
machines and tend to have features such as electric start, reverse, and electric warming hand
grips.
The last, and smallest, segment of the snowmobile market is the utility sled segment.
Utility snowmobiles are designed for pulling loads and for use in heavy snow. Thus, the engines
are designed more for producing torque at low engine speeds, which typically corresponds to a
reduced maximum speed of the snowmobile. Utility snowmobiles are common in search and
rescue operations.
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Draft Regulatory Support Document
A typical snowmobile lasts seven to nine years and travels over 5,000 miles during its
lifetime, with annual mileage dropping with age. The average snowmobile is used 57 hours per
year.
2.3.4 Customer Concerns
2.3.4.1 Performance
Good snowmobile performance is very important to snowmobilers. This is especially
true for the performance segment of the market, where high power and low weight are crucial for
the enjoyment of the performance snowmobile enthusiast. The performance snowmobile
segment is driven by a constant demand for more power and lower weight. In the touring
segment of the market performance in terms of power and weight is somewhat less important,
but still significant. In this segment comfort features and fuel economy play a bigger role in
customer satisfaction than in the performance segment. In all snowmobile market segments
durability and reliability are very important to the customer.
2.3.4.2 Cost
The price of snowmobiles produced by the four major manufacturers currently ranges
from about $3,700 for some entry level models to around $12,000 for some high performance
and luxury touring machines. The average cost of snowmobiles sold in the U.S. is in the $6,000
to $7,000 range. Some of the high performance snowmobiles produced by the small
manufacturers can approach $20,000, but this is an extremely small niche market.
Snowmobiles are for the most part a recreational product and are thus a discretionary
purchase. Cost is an important factor for snowmobilers, and significant cost increases could
cause people to spend their discretionary income on other recreational opportunities. This is
especially significant in the low cost, entry level snowmobile segment (the point of entry into the
sport of snowmobiling) where significant cost increases could discourage people from taking up
snowmobiling.
2.4 All-Terrain Vehicles
All Terrain Vehicles (ATVs) are normally one-passenger open vehicles that are used for
recreational and other purposes requiring the ability to traverse over most types of terrain. Most
modern ATVs have four-wheels, and have evolved from three-wheeled designs that were first
introduced in the 1970s. According to data provided by an EPA contractor, production for ATVs
sold in the U.S. has averaged about 390,000 units between 1996 and 2000. However, ATV sales
have increased during that time to more than 550,000 units in 2000. Thus, ATVs constitute the
largest single category of non-highway recreational vehicles, although it is difficult to calculate
the total vehicle population at any given point in time because of the fact that many states do not
require registration of ATVs.
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Chapter 2: Industry Characterization
2.4.1 Manufacturers
Manufacturers of ATVs are classified under the North American Industrial Classification
System (NAICS) as code 336999, Other Transportation Equipment Manufacturing. These codes
are used by the Small Business Administration (SBA) in classifying businesses as large or small,
depending on the number of employees. ATV manufacturers have the NAICS sub-classification
3369993101, and must have fewer than 500 employees to be considered a small business. In ad-
dition to manufacturers, there are a number of importers of ATVs, which fall under NAICS code
42111, which also includes importers of automobiles, trucks, motorcycles and motor homes. To
be classified as a small business by SBA, an importer must have fewer than 100 employees.
We contracted with ICF Consulting to help us characterize the off-highway recreational
vehicle market.6 Using data which included the Power Systems Research (PSR) Database, Dun &
Bradstreet (D&B) Market Identifiers Online Database, and information from the Motorcycle In-
dustry Council (MIC), our contractor identified 16 manufacturers of ATVs. These can be found
in Table 2.4.1. Six large manufacturers, Honda, Polaris, Kawasaki, Yamaha, Suzuki, and Arctic
Cat accounted for approximately 98 percent of all U.S. ATV production in calendar year 2000.
The 10 other manufacturers accounted for the remaining two percent of U.S. production
in 2000. Only three of these are non-U.S.-owned. Available D&B data on numbers of employees
for five of the companies show that they are small businesses according to the SBA definition.
There are also some 17 firms that import ATVs. Thirteen of these are U.S.-owned. Dun
and Bradstreet data on numbers of employees are available for four of these companies, and
indicate that these are small businesses according to the SBA definition. Since none of these had
more than 40 employees and two had less than 20 employees, it seems safe to assume that the
others are also small businesses according to the SBA definition.
Table 2.4.-1
ATV Manufacturers/Importers
Firm Name
ATK
COSMOPOLITAN MOTORS
D.R.R. INC.
E-TON DISTRIBUTION LP
HOFFMAN GROUP INC.
J & J SALES
JEHM POWERSPORTS
KASEA MOTORSPORTS
MANGO PRODUCTS
Type
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
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Draft Regulatory Support Document
MOTORRAD OF NORTH AMERICA
PANDA MOTORSPORTS
POWERGROUP INTERNATIONAL ALPHASPORTS
REINMECH MOTOR COMPANY, LTD
TRANSNATIONAL OUTDOOR POWER LLC
TWS-USA, INC
ULTIMAX LCC
UNITED MOTORS OF AMERICA, INC
AMERICAN SUNDIRO
ARCTIC CAT, INC.
BOMBARDIER
CANNONDALE CORP - BEDFORD
HONDA AMERICAN MANUFACTURING
HYOSUNG MOTORS AND MACHINERY
INTERNATIONAL POWERCRAFT
KAWASAKI MOTORS CORPORATION
KEEN PERCEPTION INDUSTRIES
MOSS
PANDA MOTORSPORTS
POLARIS INDUSTRIES
ROADMASTER /FLEXIBLE FLYER
SUZUKI
TAI LING MOTOR COMPANY
YAMAHA MOTOR MANUFACTURING CORP.
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
2.4.1.1 Engine Manufacturers
Four of the major ATV producers, Honda, Kawasaki, Yamaha and Suzuki, are both
engine and equipment manufacturers. In addition, Suzuki produces engines for Arctic Cat, and in
fact owns a significant amount of Arctic Cat common stock. Hyosung Motors and Machinery
and the Tai Ling Motor company also use Suzuki engines in ATVs that are sold in the U.S.
Although Polaris produces some of its own engines, a substantial number are supplied by Fuji
Heavy Industries, primarily an auto and truck manufacturer, and its U.S. subsidiary, Robin
Industries. Polaris owns a substantial amount of Robin common stock.
Other engine manufacturers include Rotax, which is a subsidiary of Bombardier Inc., a
large Canadian company. Bombardier is primarily a snowmobile manufacturer, but has recently
2-14
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Chapter 2: Industry Characterization
entered the ATV market. Bombardier/Rotax also produces engines for a wide variety of other
applications, including snowmobiles, motorcycles, ATVs, personal water craft (PWC), utility
vehicles and aircraft. A few small ATV manufacturers use Briggs or Kohler utility engines, but
these are covered by EPA's Small Spark Ignition (SI) Engine regulations and are not included in
this analysis 7
2.4.1.2 Equipment Manufacturers
Four of the six major ATV manufacturers, Honda, Kawasaki, Yamaha and Suzuki, are
primarily automobile and/or on-highway motorcycle manufacturers who also produce ATVs, off-
highway motorcycles, snowmobiles, PWC and other non-highway vehicles. Polaris and Arctic
Cat are major snowmobile manufacturers, in addition to producing ATVs. Polaris also produces
on-highway motorcycles and Arctic Cat produces PWC.
Of the remaining 10 producers, 5 are classified as large businesses, and 5 are classified as
small businesses. As noted above, Bombardier is a large Canadian snowmobile manufacturer that
has recently entered the ATV market. Cannondale is a large American bicycle manufacturer that
has also recently entered the ATV market. Hyosung and Tai Ling are large Far Eastern manu-
facturers, who also manufacture motorcycles and motorscooters (in the case of Hyosung). Road-
master/Flexible Flyer is primarily a large bicycle and toy manufacturer which also produces
youth ATVs that are sold in large discount stores. The 17 importers and 5 small manufacturers
either import completed ATVs or assemble them in this country from imported parts.
2.4.2 Applications
As noted above, ATVs are used for recreational and other purposes. Examples of non-
recreational uses are for hauling and towing on farms, ranches or in commercial applications.
Some ATVs are sold with attachments that allow them to take on some of the functions of a
garden tractor or snow blower. ATVs are also used for competitive purposes, although not to the
same extent as off-highway motorcycles.
2.4.3 Engine Design and Operation
The majority of ATVs sold in the U.S. are powered by single-cylinder, four-stroke cycle
engines of less than 40 horsepower, operating under a wide variety of operating conditions and
load factors. Engine displacements range from 50cc for an entry-level youth model to 660cc for a
high-performance adult model, but more than three-fourths of them fall in the 200-500cc range.
2.4.3.1 Two-Stroke vs Four-Stroke Cycle Engine Usage
According to statistics compiled by our contractor, more than 92 percent of all ATVs
produced for US consumption use four-stroke cycle engines. However, estimates provided by
MIC reduce this percentage to 88 percent. Of the six major manufacturers, only Polaris, Suzuki
and Yamaha used two-stroke cycle engines at all. The remainder of the two-stroke engines in
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Draft Regulatory Support Document
ATVs sold in U.S. are found in entry-level or youth models, which are imported from the Far
East, or assembled in this country from imported parts. In general two-stroke engines are less
expensive to produce than four-stroke engines, thus providing a marketing advantage in the youth
and entry-level categories. We estimate that two-strokes make up roughly twenty percent of the
market when the imported youth models are included.
2.4.3.2 Use of Engines in Other Applications
Although a few ATV engine lines have been used in other applications, such as some
smaller on- and off-highway motorcycles, manufacturers have stated that ATV engines are
normally designed only for use in ATVs. ATV engines may share certain components with
motorcycles, snowmobiles and PWC, but many major components such as pistons, cylinders and
crankcases differ within given engine displacement categories.
2.4.3.3 Customer Concerns
Except for the competitive segment of the market, performance seems to be somewhat
less important to ATV purchasers than it is to purchasers of snowmobiles or off-highway
motorcycles. Most youth models, which form a significant portion of the market, are normally
equipped with governors or other speed-limiting devices. Performance can be important for some
of the higher-end adult models, but handling is also an important consideration, particularly when
riding in dense wooded areas. Durability and reliability are also important to the customer, but
perhaps not as important as price.
The price of an ATV can ranges from about $1,200 for an entry-level youth model to
around $7,000 or more for a large, high performance machine. ATVs, like other recreational
vehicles, are basically discretionary purchases, although utility may enter into the equation more
often than in the case of off-highway motorcycles or snowmobiles.. Cost is an important factor,
particularly in the youth or entry-level segments of the market, and significant cost increases
could cause people to spend their discretionary funds in other areas.
2.5 Off-Highway Motorcycles
Off-highway motorcycles, commonly referred to as "dirt bikes," are designed specifically
for use on unpaved surfaces. As such, they have certain characteristics in common, such as a
large amount of clearance between the fenders and the wheels, tires with aggressive knobby tread
designs, and they lack some of the equipment typically found on highway motorcycles, e.g.,
lights, horns, turn signals, and often mufflers. They are thus not normally able to be licensed for
on-highway use. There are a limited number of motorcycles, known as dual-purpose motorcycles,
that can be used for both on- and off-highway purposes. These can be licensed for highway use,
and so fall under the current highway motorcycle regulations, assuming that they are powered by
engines of 50cc or larger displacement. Off-highway motorcycles are used for recreational riding,
but substantial numbers are also used for competition purposes. Some in fact can be used for
little else, e.g., machines that are designed for observed trials competition, which have no seats in
2-16
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Chapter 2: Industry Characterization
the conventional sense of the term, and engine characteristics that are totally unlike those of most
other motorcycles. Only a few thousand observed trials bikes are produced each year.
Our contractor found that production of off-highway motorcycles produced for sale in the
U.S. has averaged about 110,000 units between 1995 and 1999. As is the case with ATVs, off-
highway motorcycle production has increased considerably in later years, to more than 150,000
units in 1999, and assumed to be the same or higher for 2000, although the exact numbers were
not available at the time of preparation of this analysis. Since many states do not require registra-
tion of off-highway motorcycles, it is difficult to estimate a total population at any given time.
2.5.1 Manufacturers
Motorcycle manufacturers are classified under the NAICS system as code 336991, Mo-
torcycle, Bicycle and Parts Manufacturers. Motorcycle manufacturers have the subcode 3369913,
which includes manufacturers of scooters, mopeds and sidecars. To be classified as a small busi-
ness, the manufacturer must have fewer than 500 employees. Motorcycle Importers are classified
as subcode 4211101, which also includes automobile importers, and has an SBA cutoff of 100
employees to be considered a small business.
Our contractor has identified 24
manufacturers of off-highway
motorcycles. These can be found in Table
2.5.1. Five large manufacturers, Honda,
Kawasaki, Yamaha, Suzuki, and KTM.
accounted for approximately 85 percent of
all production for sale in the U.S. in
calendar year 2000. These are all
companies that manufacture automobiles
and/or on-highway motorcycles,
motorscooters, ATVs, and PWC as well
as off-highway motorcycles. Honda is by
far the largest producer of off-highway
motorcycles, with over 45 percent of the
total production for sale in the U.S. Figure
2.5.1 shows the market shares for the top
five and the other producers
OFF-HIGHWAY MOTORCYCLES
PRODUCTION BY MFR
PERCENT OF TOTAL
15.2%
10.8%
9.8%
45.1%
D HONDA
D KAWASAKI
• KTM
D SUZUKI
HI YAMAHA
D OTHERS
9.6%
9.5%
Figure 2.5.1
The 19 other manufacturers accounted for the remaining 15 percent of production for
U.S. sale. Six of these firms, accounting for approximately 3 percent of total production for the
U.S. market, are located in this country. Dun and Bradstreet employee data are available for four
of the six U.S. manufacturers, indicating that these are small businesses according to the SBA
definition.
Our contractor has also identified 16 off-highway motorcycle importers. Eight of these
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Draft Regulatory Support Document
are U.S.-owned. Dun and Bradstreet data are available for five of the eight U.S. importers, indi-
cating that they are small businesses. Again, it seems likely that all eight are small businesses.
2-18
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Chapter 2: Industry Characterization
Table 2
U.S. Off-Highway Motorcycle
5.-1
Manufacturers/Importers
Firm Name
ACTION POLINI
BETA USA
CODY RACING PRODUCTS
COSMOPOLITAN MOTORS INC.
CRE IMPORTS/E-LINE ACCESSORIES
GAS GAS NORTH AMERICA
HUSQVARNA USA
KASEA MOTORSPORTS
KTM SPORTMOTORCYCLE USA, INC.
MIDWEST MOTOR VEHICLES, INC.
TRANSNATIONAL OUTDOOR POWER, LLC
TRYALS SHOP
TWS-USA INC.
U.S. MONTESA
UNITED MOTORS OF AMERICA
VOR MOTORCYCLES USA
AMERICAN DIRT BIKE INC. (U.S.)
ATK MOTORCYCLES (U.S.)
BETAMOTOR SPA (ITALY)
CAGIVA MOTORCYCLE SPA (ITALY)
CANNONDALE CORP - BEDFORD (U.S.)
CCM MOTORCYCLES LTD (U.K.)
COBRA MOTORCYCLE MFG. (U.S.)
GAS GAS MOTOS SPA (SPAIN)
HM MOTORCYCLES (U.S.)
HONDA MOTORCYCLES (JAPAN)
HUSABERG MOTOR AB (SWEDEN)
HYOSUNG MOTORS AND MACHINERY (KOREA)
KAWASAKI HEAVY INDUSTRIES (JAPAN)
KTM SPORT MOTORCYCLE AG (AUSTRIA)
LEM MOTOR SAS (ITALY)
MADFAST MOTORCYCLES (IRELAND)
MINSK MOTOVELOZAVOD (BELARUS)
MONTESA-HONDA ESPANA, SA (SPAIN)
PIAGGIO GROUP (ITALY)
POLINI (ITALY)
REV! MOTORCYCLES (U.S.)
SUZUKI (JAPAN)
TAI LING MOTOR COMPANY LTD. (TAIWAN)
VOR MOTOR 1 (ITALY)
Type
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
IMPORTER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
MANUFACTURER
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Draft Regulatory Support Document
HYAMAHA MOTOR COMPANY LTD. (JAPAN) I MANUFACTURER II
2.5.1.1 Engine Manufacturers
For the majority of off-highway motorcycles, the vehicle manufacturer is also the engine
manufacturer. However, a few motorcycle manufacturers use engines produced by other firms.
ATK Motorcycles and CCM Motorcycles Ltd. use Bombardier/Rotax engines, while the Tai Ling
Motor Company uses Suzuki engines. A Spanish manufacturer, Gas Gas Motos, SA, noted
primarily for its observed trials machines, produces some of its own engines and buys others
from Cagiva, a large Italian manufacturer. One U.S. manufacturer, Rokon, markets a low-
production trail motorcycle resembling a large motorscooter, which is intended for hunters and
fishermen. Rokon uses industrial-type engines made by Honda and other manufacturers which
again would fall under the EPA Small SI regulations. Rokon is therefore not included here.
2.5.1.2 Equipment Manufacturers
Our contractor has identified some 24 firms that manufacture off-highway motorcycles
for the U.S. market. Six of these are U.S. manufacturers. With the exception of Connondale,
which is primarily a bicycle manufacturer, all of them produce only motorcycles. Italy has five
manufacturers. One of these, Cagiva, is mainly a producer of on-highway motorcycles. Piaggio
is primarily a motorscooter manufacturer; Betamotor makes motorscooters and trials bikes. Lem
and Polini manufacturer youth motorcycles. Spanish manufacturers of off-highway motorcycles
that are imported to the U.S. include Gas Gas, primarily an observed trials bike manufacturer,
and Montesa, which is owned by Honda. Other manufacturing companies whose products are
imported into the U.S. market are also found in Austria, Belarus, Ireland, Korea, Sweden,
Taiwan, and the United Kingdom. KTM, an Austrian company with a U.S. branch, is one of the
five major producers for the U.S. market.
2.5.2 Applications
As noted above, off-highway motorcycles can be used for recreational purposes or for
competition. EPA defines vehicles that are "used solely for competition" as those with features
(not easily removable from the vehicle) that would make the vehicle's use in other recreational
activities unsafe, impractical, or highly unlikely. EPA's noise regulations also exempt any off-
highway motorcycle that is designed and marketed solely for use in closed-course competition.
Certain types of off-highway motorcycles are designed and marketed for closed-course
competition. These are commonly known as "motocross bikes." We have information from our
contractor indicating that some 12-14 percent of off-highway motorcycles produced from 1996 to
2000 were motocross bikes. Other sources have estimated motocross to be closer to 30 percent of
off-highway sales.8 Other types of competition motorcycles are the observed trials machines
mentioned above, which emphasize handling ability rather than speed, and the so-called "enduro
bikes." Enduro bikes are designed for cross-country type racing, rather than closed-course
competition. As such, they do have need for some of the equipment normally found on non-
2-20
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Chapter 2: Industry Characterization
racing machines, such as spark arresters (required by U.S. Forest Service regulations) and at least
minimal lighting packages, but are exempt from the muffler requirement contained in the EPA
noise regulations.
Whether for competition or recreational use, off-highway motorcycles are operated under
transient conditions that include a wide variety of speeds and load factors.
2.5.3 Engine Design and Operation
Off-highway motorcycle engines have traditionally been about two-thirds smaller and less
powerful than those used in on-highway cycles. For 2000, about 68 percent of the models
produced were less than 300cc displacement, and half of these were lOOcc or less. Percentages
for the top five producers were approximately the same as for the industry as a whole. The dis-
tribution of engine sizes tends to be somewhat bimodal, with another 14 percent of the total
falling into the 500-700cc range. (See Figure 2.5.2) This is likely because of the increase in the
number of four-stroke engines in recent years, most of which tend to fall in the larger (500-
700cc) displacement ranges. Unlike on-highway motorcycles, our contractor found no off-
highway engines larger than 700cc.
OFF-HIGHWAY MOTORCYCLE PRODUCTION
TOP 5 MANUFACTURERS
O CO
O ro
Z> w
§1
Q_
ou
25
20
15
10
5
n
-f
=
=
-,
n n
M^Uki Jl_ 1 [Tl
HONDA
KAWASAKI
KTM
SUZUKI
YAMAHA
<100 200-300 400-500 600-700
100-200 300-400 500-600
DISPLACEMENT - CC
Figure 2.5.2
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Draft Regulatory Support Document
2.5.3.1 Two-Stroke vs Four-Stroke Cycle Engine Usage
Data from our contractor, using the PSR database, indicate that slightly more than half of
the off-highway motorcycles produced for sale in the United States are powered by four-stroke
cycle engines. However, estimates from MIC place the percentage of two-stroke sales at more
than 60 percent. The percentage of two-strokes varies considerably by manufacturer. Honda,
which accounts for more than 45 percent of this production, is predominantly a four-stroke
manufacturer. Four-strokes comprise about two-thirds of its production. For Yamaha, the
percentage is about 57 percent. The remainder of the foreign and domestic producers make more
two-stroke engines than four-strokes. For the other top-five producers, KTM, Kawasaki and
Suzuki, the percentage of two-stroke engines varies from 58 to 72 percent, and can be even
higher (up to 100 percent) for some of the remaining manufacturers on the list.
Two-stroke engines are normally used in two primary applications: (1) racing machines,
because they tend to have a higher power-to-weight ratio than four-stroke engines (this is impor-
tant for competition, especially in the smaller displacement classes), and (2) youth model or
entry-level motorcycles, because two-strokes are cheaper to produce than four-strokes. Since
youth or entry-level motorcycles also tend to have smaller displacement engines, the higher
power-to-weight ratio of the two-stroke tends to provide a little better performance. However,
there has been a growing tendency in recent years for manufacturers to bring out more new four-
stroke engines, particularly in the higher displacement ranges. This is also true in their
competition lines.
2.5.3.2 Use of Engines in Other Applications
Only a few engine lines, primarily among the top five producers, are used in both off-
highway and on-highway motorcycles. Part of the reason for this is because over half of the off-
highway bikes use two-stroke engines, whereas there are almost no two-stroke engines to be
found in on-highway motorcycles. Also, as noted above, off-highway motorcycles generally have
much smaller displacement engines than their on-highway counterparts. Off-highway motorcycle
engines are closer in terms of engine size to ATV engines. However, ATVs also use predomi-
nantly four-stroke engines and these are not as likely to be highly-tuned for performance as are
many off-highway motorcycle engines.
2.5.3.3 Customer Concerns
Performance is highly important to motocross and other racers. The competitive segment
is consistent in its demand for machines with higher power-to-weight ratios that will make them
more competitive in racing circles. Light weight is an important aspect of this equation, since it
allows easier handling in difficult situations, in addition to increasing performance. Performance
is also important in other portions of the market as well. There seems to be a certain amount of
status involved in owning a really high-performance machine, and this may outweigh some of the
disadvantages of ownership. Durability and reliability may be of less importance to this type of
consumer, although they are important to professional racers.
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Chapter 2: Industry Characterization
Except for a few dual-purpose machines, off-highway motorcycles are purely recreational
in nature, and not suitable for day-to-day personal transportation. Unless the purchaser is an all-
out competition model customer, price can therefore be an important consideration to an off-
highway motorcycle purchaser. The price of a dirt bike can range from about $1,500 for a 50cc
entry-level model to $8,000 for a larger high performance machine. Along with other recrea-
tional machines, off-highway motorcycles are discretionary purchases. Significant cost increases
could therefore result in decreased sales of these motorcycles, as potential customers turned to
other recreational opportunities for spending their discretionary income. Again, this is most likely
in the youth/entry level segment of the market. At the other end of the spectrum, cost is relatively
unimportant to the high-end motocross or other competitors.
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Chapter 2 References
1. "Recreational Boating Industry Characterization," ICF Consulting, Contract No. 68-C-98-170,
WAN 0-5, August, 1999, Docket A-2000-01, Document U-A-9.
2. Boating Industry Magazine, "1997 Annual Industry Reviews: The Boating Business", January
1998
3. Dunn & Bradstreet.
4. National Marine Manufacturers Association -http:/www.nmma.org
5."The Role of Propane in the Fork Lift/Industrial Truck Market: A Study of its Status, Threats,
and Opportunities," Robert E. Myers for the National Propane Gas Association, December 1996,
Docket A-98-01, Document II-D-2.
6. "Industry Characterization of Non-Road Recreational Vehicles," ICF Consulting, September,
2001.
7. See 40CFR Part 90, Subpart B.
8. "Year 2000 Facts & Figures," Dirt Bike Magazine, September, 2000.
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Chapter 2: Industry Characterization
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Chapter 3: Technology
CHAPTER 3: Technology
This chapter describes the current state of spark-ignition technology for engines,
evaporative emission technology, and compression-ignition technology for marine engines, as
well as the emission control technologies expected to be available for manufacturers. Chapter 4
presents the technical analysis of the feasibility of the proposed standards.
3.1 Introduction to Spark-Ignition Engine Technology
The two most common types of engines are gasoline-fueled engines and diesel-fueled
engines. These engines have very different combustion mechanisms. Gasoline-fueled engines
initiate combustion using spark plugs, while diesel fueled engines initiate combustion by
compressing the fuel and air to high pressures. Thus these two types of engines are often more
generally referred to as "spark-ignition" and "compression-ignition" (or SI and CI) engines, and
include similar engines that used other fuels. SI engines include engines fueled with LPG and
CNG.
3.1.1 Four-Stroke Engines
Four-stroke engines are used in many different applications. Virtually all automobiles
and many trucks are powered by four-stroke SI engines. Four-stroke engines are also very
common in motorcycles, all-terrain vehicles (ATVs), boats, airplanes, and numerous nonroad
applications such as lawn mowers, lawn and garden tractors, and generators, to name just a few.
A "four-stroke" engine gets it's name from the fact that the piston makes four passes or
strokes in the cylinder to complete an entire cycle. The strokes are intake, compression, power,
and exhaust. Two of the strokes are downward (intake & power) and two of the strokes are
upward (compression & exhaust). Valves in the combustion chamber open and close to route
gases into and out of the combustion chamber or create compression.
The first step of the cycle is for an intake valve in the combustion chamber to open during
the "intake" stroke allowing a mixture of air and fuel to be drawn into the cylinder while an
exhaust valve is closed and the piston moves down the cylinder. The piston moves from top
dead center (TDC) or the highest piston position to bottom dead center (BDC) or lowest piston
position. This creates a vacuum or suction in the cylinder, which draws air and fuel past the open
intake valve into the combustion chamber.
The intake valve then closes and the momentum of the crankshaft causes the piston to
move back up the cylinder from BDC to TDC, compressing the air and fuel mixture. This is the
"compression" stroke. As the piston nears TDC, at the very end of the compression stroke, the
air and fuel mixture is ignited by a spark from a spark plug and begins to burn. As the air and
fuel mixture burns, increasing temperature and pressure cause the piston to move back down the
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Draft Regulatory Support Document
cylinder, transmitting power to the crankshaft. This is referred to as the "power" stroke. The last
stroke in the four-stroke cycle is the "exhaust" stroke. At the bottom of the power stroke, an
exhaust valve opens in the combustion chamber and as the piston moves back up the cylinder,
the burnt gases are pushed out through the exhaust valve to the exhaust manifold, and the cycle is
complete.
3.1.2 Two-Stroke Engines
Two-stroke SI engines are widely used in nonroad applications, especially for recreational
vehicles, such as snowmobiles, off-highway motorcycles and ATVs. The basic operating
principle of the charge scavenged two-stroke engine (traditional two-stroke) is well understood;
in two-strokes the engine performs the operations of intake, compression, expansion and exhaust,
which the four-stroke engine requires four strokes to accomplish. Two-stroke engines have
several advantages over traditional four-stroke engines for use in recreational vehicles: high
power-to-weight ratios; simplicity; ease of starting; and lower manufacturing costs. However,
they also have much higher emission rates.
Another difference between two- and four-stroke engines is how the engines are
lubricated. Four-stroke engines use the crankcase as a sump for lubricating oil. Oil is distributed
throughout the engine by a pump through a series of small channels. Because the crankcase in a
two-stroke engine serves as the pump for the scavenging process, it is not possible to use it as an
oil sump as is the case for four-stroke engines. Otherwise, gasoline would mix with the oil and
dilute it. Instead, lubrication for two-stroke engines is provided by mixing specially-formulated
two-stroke oil with the incoming charge of air and fuel mixture. The oil is either mixed with the
gasoline in the fuel tank, or metered into the gasoline as it is consumed, using a small metering
pump. As the gasoline/oil mixture passes through the carburetor, it is atomized into fine droplets
and mixed with air. The gasoline quickly vaporizes, while the less volatile oil forms a fine mist
of fine droplets. Some of these droplets contact the crankshaft, piston pin, and cylinder walls,
providing lubrication. Most of the oil droplets, however, pass out of the crankcase and into the
cylinder with the rest of the incoming charge.
In a two-stroke engine, combustion occurs in every revolution of the crankshaft. Two-
stroke engines eliminate the intake and exhaust strokes, leaving only compression and power
strokes. This is due to the fact that two-stroke engines do not use intake and exhaust valves.
Instead, they have openings, referred to as "ports," in the sides of the cylinder walls. There are
typically three ports in the cylinder; an intake port that brings the air-fuel mixture into the
crankcase; a transfer port that channels the air and fuel mixture from the crankcase to the
combustion chamber; and an exhaust port that allows burned gases to leave the cylinder and flow
into the exhaust manifold. Two-stroke engines route incoming air and fuel mixture first into the
crankcase, then into the cylinder via the transfer port. This is fundamentally different from a
four-stroke engine which delivers the air and fuel mixture directly to the combustion chamber.
With a two-stroke engine, as the piston approaches the bottom of the power stroke, it
uncovers exhaust ports in the wall of the cylinder. The high pressure burned combustion gases
3-2
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Chapter 3: Technology
blow into the exhaust manifold. At the same time, downward piston movement compresses the
fresh air and fuel mixture charge in the crankcase. As the piston gets closer to the bottom of the
power stroke, the transfer ports are uncovered, and fresh mixture of air and fuel are forced into
the cylinder while the exhaust ports are still open. Exhaust gas is "scavenged" or forced into the
exhaust by the pressure of the incoming charge of fresh air and fuel. In the process, however,
some mixing between the exhaust gas and the fresh charge of air and fuel takes place, so that
some of the fresh charge is also emitted in the exhaust. Losing part of the fuel out of the exhaust
during scavenging causes the very high hydrocarbon emission characteristics of two-stroke
engines.
At this point, the power, exhaust, and transfer events have been completed. When the
piston begins to move up, its bottom edge uncovers the intake port. Vacuum draws fresh air and
fuel into the crankcase. As the piston continues upward, the transfer port and exhaust ports are
closed. Compression begins as soon as the exhaust port is blocked. When the piston nears TDC,
the spark plug fires and the cycle begins again.
3.1.3 Engine Calibration
For most current SI engines, the two primary variables that manufacturers can control to
reduce emissions are the air and fuel mixture (henceforth referred to as air-fuel ratio) and the
spark timing. For highway motorcycles, these two variables are the most common methods for
controlling exhaust emissions. However, for many nonroad engines and vehicles, the absence of
emission standards have resulted in air-fuel ratio and spark timing calibrations optimized for
engine performance and durability rather than for low emissions.
3.1.3.1 Air-fuel ratio
The calibration of the air-fuel mixture affects power, fuel consumption (referred to as
Brake Specific Fuel Consumption (BSFC)), and emissions for SI engines. The effects of
changing the air-fuel mixture are shown in Figure 3-1.l Traditionally, in most nonroad SI
applications, manufacturers have calibrated their fuel systems for rich operation for two main
advantages. First, by running the engine rich, manufacturers can reduce the risk of lean misfire
due to imperfect mixing of the fuel and air and variations in the air-fuel mixture from cylinder to
cylinder. Second, by making extra fuel available for combustion, it is possible to get more power
from the engine. At the same time, since a rich mixture lacks sufficient oxygen for full
combustion, it results in increased fuel consumption rates and higher HC and CO emissions. As
can be seen from the figure, the best fuel consumption rates occur when the engine is running
lean.
With the use of more advanced fuel systems, manufacturers would be able to improve
control of the air-fuel mixture in the cylinder. This improved control allows for leaner operation
without increasing the risk of lean misfire. This reduces HC and CO emissions and fuel
consumption. Leaner air-fuel mixtures, however, increase NOx emissions due to the higher
temperatures and increased supply of oxygen.
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Draft Regulatory Support Document
Figure 3-1: Effects of Air-fuel Ratio on Power, Fuel Consumption, and Emissions
I
CL
O
LL
OT
CQ
Lean
Stoichiometric
Rich
Power
I
I
BSFC
I
I
ro
o
ta
E
LU
"3
O
Lean
Stoichiometric
Rich
NOx
; co
I
I
I
0.7 0.8 0.9 1.0 1.1 1.2
Fuel/Air Equivalence Ratio
3.1.3.2 Spark-timing:
1.3
0.7 0.8 0.9 1.0 1.1
Fuel/Air Equivalence Ratio
1.2
1.3
For each engine speed and air-fuel mixture, there is an optimum spark-timing that results
in peak torque. If the spark is advanced to an earlier point in the cycle, more combustion occurs
during the compression stroke. If the spark is retarded to a later point in the cycle, peak cylinder
pressure is decreased because too much combustion occurs later in the expansion stroke when it
generates little torque on the crankshaft. Timing retard may be used as a strategy for reducing
NOx emissions, because it suppresses peak cylinder temperatures that lead to high NOx levels.
Timing retard also results in higher exhaust gas temperatures, because less mechanical work is
extracted from the available energy. This may have the benefit of warming catalyst material to
more quickly reach the temperatures needed to operate effectively during light-load operation.2
Some automotive engine designs rely on timing retard at start-up to reduce cold-start emissions.
Advancing the spark-timing at higher speeds gives the fuel more time to burn. Retarding
the spark timing at lower speeds and loads avoids misfire. With a mechanically controlled
engine, a fly-weight or manifold vacuum system adjusts the timing. Mechanical controls,
however, limit the manufacturer to a single timing curve when calibrating the engine. This
means that the timing is not completely optimized for most modes of operation.
3.1.3.3 Fuel Metering
Fuel injection has proven to be an effective and durable strategy for controlling emissions
and reducing fuel consumption from highway gasoline engines. Comparable upgrades are also
available for gaseous fuels. This section describes a variety of technologies available to improve
fuel metering.
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Chapter 3: Technology
Throttle-body gasoline injection: A throttle-body system uses the same intake manifold
as a carbureted engine. However, the throttle body replaces the carburetor. By injecting the fuel
into the intake air stream, the fuel is better atomized than if it were drawn through with a venturi.
This results in better mixing and more efficient combustion. In addition, the fuel can be more
precisely metered to achieve benefits for fuel economy, performance, and emission control.
Throttle-body designs have the drawback of potentially large cylinder-to-cylinder
variations. Like a carburetor, TBI injects the fuel into the intake air at a single location upstream
of all the cylinders. Because the air-fuel mixture travels different routes to each cylinder, the
amount of fuel that reaches each cylinder will vary. Manufacturers account for this variation in
their design and may make compromises such as injecting extra fuel to ensure that the cylinder
with the leanest mixture will not misfire. These compromises affect emissions and fuel
consumption.
Multi-port gasoline injection: As the name suggests, multi-port fuel injection means that
a fuel injector is placed at each of the intake ports. A quantity of fuel is injected each time the
intake valve opens for each cylinder. This allows manufacturers to more precisely control the
amount of fuel injected for each combustion event. This control increases the manufacturer's
ability to optimize the air-fuel ratio for emissions, performance, and fuel consumption. Because
of these benefits, multi-port injection is has been widely used in automotive applications for over
15 years.
Sequential injection has further improved these systems by more carefully timing the
injection event with the intake valve opening. This improves fuel atomization and air-fuel
mixing, which further improves performance and control of emissions.
A newer development to improve injector performance is air-assisted fuel injection. By
injecting high pressure air along with the fuel spray, greater atomization of the fuel droplets can
occur. Air-assisted fuel injection is especially helpful in improving engine performance and
reducing emissions at low engine speeds. In addition, industry studies have shown that the short
burst of additional fuel needed for responsive, smooth transient maneuvers can be reduced
significantly with air-assisted fuel injection due to a decrease in wall wetting in the intake
manifold. On a highway 3.8-liter engine with sequential fuel injection, the air assist was shown
to reduce HC emissions by 27 percent during cold-start operating conditions. At wide-open-
throttle with an air-fuel ratio of 17, the HC reduction was 43 percent when compared with a
standard injector.3
3.1.4 Alternate Fuels
2. Gaseous-fuel engines
Engines operating on LPG or natural gas carry compressed fuel that is gaseous at
atmospheric pressure. The technical challenges for gasoline related to an extended time to
vaporize the fuel don't apply to gaseous-fuel engines. Typically, a mixer introduces the fuel into
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Draft Regulatory Support Document
the intake system. Manufacturers are pursuing new designs to inject the fuel directly into the
intake manifold. This improves control of the air-fuel ratio and the combustion event, similar to
the improvements in gasoline injection technology.
3.2 Exhaust Emissions and Control Technologies
3.2.1 Current Two-Stroke Engines
As discussed above, two-stroke engines are typically found in applications where light
weight, low cost, simplistic design, easy starting, and high power-to-weight ratio are desirable
attributes. Of the engines and vehicles and covered by this proposal, the engines found in
recreational vehicles tend to have a high percentage of two-stroke engines. For example, all
snowmobiles use two-stroke engines, while 40 percent of off-highway motorcycles are equipped
with two-strokes. Approximately 15 percent of all ATVs use two-stroke engines.
California ARB has had exhaust emission standards for off-highway motorcycles and
ATVs since 1996. However, the regulations allow the sales and use of non-certified vehicles
within the state. Thus, recreational vehicles equipped with two-stroke engines have essentially
been unregulated. As a result, two-stroke engines used in recreational vehicles are typically
designed for optimized performance and durability rather than low emissions. Current two-
stroke engines emit extremely high levels of HC and CO emissions. The scavenging of unburned
fuel into the exhaust contributes to the bulk of the HC emissions. Up to 30 percent13 of the air
and fuel mixture (along with lubricating oil) can pass unburned from the combustion chamber to
the exhaust, resulting not only in high levels of HC, but also in high levels of particulate matter
(PM). As discussed above, two-stroke engines lubricate the engine by mixing specially-
formulated two-stroke oil with gasoline. As the gasoline/oil mixture passes through the
carburetor, it is atomized into fine droplets and mixed with air. The gasoline quickly vaporizes,
while the less volatile oil forms a fine mist of fine droplets. Some of these droplets contact the
crankshaft, piston pin, and cylinder walls, providing lubrication. Most of the oil droplets,
however, pass out of the crankcase and into the cylinder with the rest of the incoming charge.
Much of this oil mist will be trapped in the cylinder and burned along with the gasoline vapor.
Since lubricating oil is less combustible than gasoline, some of the oil will survive the
combustion process in the cylinder and be passed into the exhaust. In the hot exhaust, the oil
may vaporize, however, as the exhaust cools and through mixing with air after it is emitted, the
oil vapor recondenses into very fine droplets or particles and enter the atmosphere as PM.
Another major source of unburned HC emissions from two-stroke engines is due to
misfire or partial combustion at light loads. Under light load conditions such as idle, the flow of
fresh air and fuel into the cylinder is reduced, and substantial amounts of exhaust gas are retained
in the cylinder. This high fraction of residual gas leads to incomplete combustion or misfire,
b Hare et al, 1974; Batoni, 1978; Nuti and Martorano, 1985
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Chapter 3: Technology
which is the source of the "popping" sound produced by two-stroke engines at idle and light
loads. These unstable combustion events are major sources of unburned HC at idle and light
load conditions.0
High CO levels from two-stroke engines are a result of operating the engine at rich air and
fuel mixture levels to promote engine cooling and enhance performance. Two-stroke engines
typically have very low levels of NOx emissions due to relatively cool combustion temperatures.
Two-stroke engines have cooler combustion temperatures as a result of two phenomenon: rich air
and fuel mixture operation and internal exhaust gas recirculation. Two-stroke engines tend to
operate with a rich air and fuel mixture to increase power and to help cool the engine. Because
many two-stroke engines are air-cooled, the extra cooling provided by operating rich is a
desirable engine control strategy. Combustion with a rich air and fuel mixture results in some
incomplete combustion which means less efficient combustion and a lower combustion
temperature. High combustion temperature is the main variable in producing NOx emissions.
Two-stroke engines also tend to have a high levels of naturally occurring exhaust gas
recirculation due to the scavenging process where some of the burned gases are drawn back into
the cylinder rather than being emitted out into the exhaust. The addition of burned exhaust gas
into the fresh charge of air and fuel mixture in the combustion chamber also results in less
complete or efficient combustion, which lowers combustion temperatures and reduces NOx
emissions.
HC emissions for recreational vehicle two-stroke engines are approximately 25 times
higher than for recreational vehicle four-stroke emissions. CO levels are roughly the same for
both types of engines, while NOx levels are 1.5 times lower than four-stroke engine levels.
Table 3.2-1 shows two-stroke emission results for several off-highway motorcycles and ATVs
tested by and for EPA in grams per kilometer (g/km). Table 3.2-2 shows two-stroke emission
results from snowmobiles in grams per horsepower-hour (g/hp-hr).
c Tsuchiya et al, 1983; Abraham and Prakash, 1992; Aoyama et al, 1977
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Draft Regulatory Support Document
Table 3.2-1
Baseline Two-Stroke Emissions From Off-Highway Motorcycles & ATVs (g/km)
MCor
ATV
ATV
ATV
MC
MC
MC
MC
MC
MC
MC
MC
MC
MC
MC
Manufacturer
Suzuki
Polaris
KTM
KTM
KTM
Honda
Honda
Honda
Honda
Honda
KTM
KTM
KTM
Model
LT80
Scrambler 80
125SX
125SX
200EXC
n/a
n/a
n/a
CR250R
n/a
250SX
250EXC
300EXC
Model
Year
1998
2001
2001
2001
2001
1993
1993
1995
1997
1998
2001
2001
2001
Eng. Displ.
80 cc
90 cc
125 cc
125 cc
200 cc
200 cc
200 cc
249 cc
249 cc
249 cc
249 cc
249 cc
298 cc
Average
HC
7.66
38.12
33.71
61.41
53.09
8.00
26.00
12.00
17.47
23.00
62.89
59.13
47.39
34.61
CO
24.23
25.08
31.01
32.43
39.89
16.00
28.00
21.00
36.62
36.00
49.29
40.54
45.29
32.72
NOx
0.047
0.057
0.008
0.011
0.025
0.010
1.010
0.010
0.004
0.010
0.011
0.016
0.0124
0.095
3-8
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Chapter 3: Technology
Table 3.2-2
Baseline Two-Stroke Emissions From Snowmobiles (g/hp-hr)
Source
Carroll 1999
(SwRI) YNP
White et al.
1997
White et al.
1997
Hare&
Springer 1974
Hare&
Springer 1974
Hare&
Springer 1974
Wright & White
1998
Wright & White
1998
ISMA #1
ISMA #2
ISMA #3
ISMA #4
ISMA #5
ISMA #6
ISMA #7
ISMA #8
ISMA #9
ISMA #10
ISMA #11
ISMA #12
ISMA #13
ISMA #14
Eng. Displ.
480 cc
488 cc
440 cc
436 cc
335 cc
247 cc
440 cc
503 cc
600 cc
440 cc
600 cc
900 cc
698 cc
597 cc
695 cc
485 cc
340 cc
440 cc
600 cc
700 cc
593 cc
494 cc
HC
115
150
160
89
120
200
130
105
110
95
106
95
92
100
88
148
104
95
94
102
67
105
CO
375
420
370
142
235
63
380
400
218
312
196
215
298
328
345
385
297
294
262
355
288
400
NOx
0.69
0.42
0.50
1.40
1.80
3.40
0.42
0.73
0.86
1.62
1.30
0.84
0.34
0.30
0.24
0.56
0.84
0.56
0.81
0.69
0.57
0.43
PM
0.7
1.1
3.4
6.1
2.5
2.6
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
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Draft Regulatory Support Document
ISMA#15
699 cc
Average
92
111
276
298
0.50
0.86
n/a
2.7
3.2.2 Clean Two-Stroke Technologies
Technologies available for reducing two-stroke emissions can be grouped into several
categories: calibration improvements; combustion chamber modifications; improved scavenging
characteristics; advanced fuel metering systems; and exhaust aftertreatment technologies.
3.2.2.1 Calibration Improvements
The vast majority of two-stroke engines used in recreational vehicles use a carburetor as
the means of metering the air and fuel that is supplied to the engine. The carburetion system
supplies a controlled mixture of air and fuel to the engine, taking into consideration engine
temperature and load and speed, while trying to optimize engine performance and fuel economy.
A carburetor is a mechanical fuel atomizing device. It uses the venturi or Bernoulli's principle,
which is based on pressure differences, to draw fuel into the air stream from a small reservoir
(known as the "bowl"). A venturi is a restriction formed in the carburetor throat. As air passes
through the venturi, it causes an increase in air velocity and creates a vacuum or low pressure.
The fuel in the bowl is under atmospheric pressure. The higher pressure fuel will flow to the
lower pressure (vacuum) created in the airstream by the venturi. The fuel is atomized (broken
into small droplets) as it enters the airstream.
As discussed above in section 3.1.3.1, the calibration of the air-fuel mixture affects
power, fuel consumption, and emissions. Traditionally, in most recreational vehicles using two-
stroke engines, manufacturers have calibrated their fuel systems for rich operation for two main
advantages. First, by running the engine rich, manufacturers can reduce the risk of lean misfire
due to imperfect mixing of the fuel and air and variations in the air-fuel mixture from cylinder to
cylinder. Second, by making extra fuel available for combustion, it is possible to get more power
from the engine. At the same time, since a rich mixture lacks sufficient oxygen for full
combustion, it results in increased fuel consumption rates and higher HC and CO emissions.
One means of reducing HC and CO emissions from two-stroke engines is to calibrate the
air-fuel ratio for lower emissions. This means leaning the air-fuel mixture, so that there is more
oxygen available to oxidize HC and CO. This strategy appears simplistic, but the manufacturer
has to not only optimize the air-fuel ratio for emissions, but also allow acceptable performance
and engine cooling. This means that the air-fuel ratio must not be leaned to the point of causing
lean misfire or substantially reduced power. However, since it is common for manufacturers to
set-up their carburetors to operate overly rich, there is opportunity for better optimization of
carburetor air-fuel settings to account for performance, engine cooling and lower emissions.
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3.2.2.2 Combustion Chamber Modifications
For two-stroke engines, if modifications are made to air-fuel calibrations that result in
leaner operation, one of the main concerns is that the combustion temperature will increase and
result in engine damage. It is fairly common for two-stroke engines to seize the piston in the
cylinder if they operate at too high of combustion temperatures. Piston seizure results when
combustion chamber temperatures become excessive and the piston heats-up and expands until it
becomes lodged or seizes in the cylinder. Depending on the level of enleanment used to control
HC and CO emissions, it may be necessary to also incorporate modifications to the combustion
chamber. Combustion chamber and piston configuration can be improved to induce more swirl
and squish or turbulent motions during the compression stroke, as well as control the flow
direction of the air and fuel mixture as it enters the combustion chamber to minimize short-
circuiting (unburned fuel leaving thru the exhaust port). Increasing turbulence in the combustion
chamber improves thermal efficiency by increasing the rate of burning in the chamber, which
results in lower combustion temperatures. Improved combustion chamber and piston
configurations can also minimize the formation of pocket or dead zones in the cylinder volume
where unburned gases can become trapped. Many engine designs induce turbulence into the
combustion chamber by increasing the velocity of the incoming air-fuel mixture and having it
enter the chamber in a swirling motion (known as "swirl").
3.2.2.3 Improved Scavenging Characteristics
As discussed above, the exhaust and intake events for two-stroke engines overlap
extensively, resulting in considerable amounts of unburned gasoline and lubricating oil passing
through the engine and out the exhaust into the atmosphere. As the piston moves downward
uncovering the exhaust port, a fresh charge of air and fuel enters the combustion chamber under
pressure from the transfer port and pushes the burned gases from the previous combustion event
out into the exhaust. Since the burned gases are pushed out of the chamber by the intake
mixture, some of the fresh air and fuel mixture being introduced into the chamber are also lost
through the exhaust port. The ideal situation would be to retain all of the fresh charge in the
cylinder while exhausting all of the burned gases from the last cycle. This is difficult in most
current two-stroke engine designs, since the cylinder ports and piston timing are generally
designed for high scavenging efficiency, in order to achieve maximum power and a smoother
idle, which results in higher scavenging losses and emissions. It is possible to reconfigure the
cylinder ports to fine tune the scavenging characteristics for lower emissions, but this involves
significant trade-offs with engine performance. There are, however, several techniques that can
be employed to improve scavenging losses.
Exhaust charge control technology modifies the exhaust flow by introducing one-way
control valves in the exhaust, or by making use of the exhaust pressure pulse wave. In order to
get increased power out of a two-stroke engine, it is imperative that the engine combust as much
air and fuel as possible. Scavenging losses from two-stroke engines (called "short-circuiting")
allow a large percentage of the air and fuel to leave the combustion chamber before they can be
combusted. Two-stroke engines used in recreational vehicles all tend to use an exhaust system
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equipped with an "expansion chamber." An expansion chamber is typically made of two cones,
one diverging and the other converging, with a short straight section of pipe between the two
cones. As the exhaust pulse leaves the exhaust port and enters the exhaust pipe, it travels
through the diverging cone and expands. The expanded pulse travels through the straight section
of pipe and then meets the converging cone. Upon hitting the converging cone, the exhaust pulse
wave becomes a sonic wave and travels back into the combustion chamber, pushing some of the
burnt exhaust gases and fresh charge of air and fuel that escaped originally.
As part of the Society of Automotive Engineers (SAE) Clean Snowmobile Challenge
2001, a college competition which encourages the development clean snowmobile technologies,
Colorado State University (CSU) developed a two-stroke snowmobile engine using a
supercharged "reverse uniflow" design. The reverse uniflow design incorporates an exhaust port
and a crankcase pressure activated intake valve. After the ignition of the charge occurs at TDC,
the high combustion pressures and expanding gases force the piston downward. As the bottom
of the piston covers the exhaust port, the pressure in the crankcase increases due to a decreasing
volume. The increasing pressure is transmitted to the check-valve diaphragm. As the piston
fully uncovers the exhaust port, the exhaust gases are expelled out of the port, and the cylinder
pressure goes to approximately atmospheric pressure. Due to the larger pressure in the crankcase
(and thus on the diaphragm) as compared to the cylinder, the check-valve opens and the
supercharged intake begins to runs into the cylinder. As the intake air is entering the cylinder,
expelling the exhaust gases out of the bottom ports, a fuel injector or carburetor provides fuel
into the intake air stream. After the piston reaches BDC, and begins to move back upwards, the
crankcase pressure decreases. Once the piston moves past the exhaust port, the crankcase
pressure returns to approximately atmospheric pressure, and the check-valve completely closes.
The piston continues up, compressing the air-fuel mixture until the point that ignition can once
again occur, completing the cycle.
3.2.2.4 Advanced Fuel Metering Systems
The most promising technology for reducing emissions from two-stroke engines are
advanced fuel metering systems, otherwise known as fuel injection systems. For two-stroke
engines, there are two types of fuel injection systems available. The first system is electronic fuel
injection (EFI), similar to what exists on automobiles. This system consists of an electronic fuel
injector, an electronic fuel pump, pressurized fuel lines and an electronic control unit (ECU) or
computer. EFI also requires the use of various sensors to provide information to the ECU so
that precise fuel control can be delivered. These sensors typically monitor temperature, throttle
position and atmospheric pressure. The use of EFI can provide better atomization of the fuel and
more precise fuel delivery than found with carburetors, which can reduce emissions. EFI systems
also have the advantage of providing improved power and fuel economy, when compared to a
carburetor. However, EFI does not address the high emission resulting from short-circuiting or
scavenging losses.
The second type of fuel injection system, known as Direct Injection (DI), does address
scavenging losses. DI systems are very similar to EFI systems, since both are electronically
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controlled systems. The main difference is that DI systems more fully atomize (i.e., break-down
into very small droplets) the fuel, which can greatly improve combustion efficiency resulting in
improved power and reduced emissions. DI engines pump only air into the cylinder, rather than
air and fuel. Finely atomized fuel is then injected into the combustion chamber once all of the
ports are closed. This eliminates the short-circuiting of fresh air and fuel into the exhaust port.
The biggest problem with DI is that there is very little time for air to be pumped into the cylinder
and fuel then injected after all of the ports have closed. This is overcome by the use of numerous
engines sensors, a high-speed electronic control module, and software which uses sophisticated
control algorithms.
DI systems have been in use for the past several years in some small motorcycle, scooter
and marine applications, primarily for personal watercraft (PWC) and outboard engines. There
are numerous variations of DI systems, but two primary approaches that are commercially
available today: high pressure injection and air-assisted injection. There are a number of
companies who have developed high pressure DI systems, but the most successful systems
currently belong to FICHT and Yamaha. The FICHT system uses a special fuel injector that is
able to inject fuel at very high pressure (e.g., over 250 psi). The fuel injector itself is essentially a
piston that is operated by an electromagnet. Fuel enters the injector at low pressure from an
electric fuel pump and is forced out of the injector nozzle at high pressure when the piston
hammers down on the fuel. The Yamaha system uses a high pressure fuel pump to generate the
high fuel pressure. The other DI approach that is most common in various engine applications is
the air-assisted injection system which has been developed by Orbital. The Orbital system uses
pressurized air to help inject the fuel into the combustion chamber. The system uses a small
single cylinder reciprocating air compressor to assist in the injection of the fuel. All three
systems are currently used in some marine applications by companies such as Kawasaki, Polaris,
Sea-Doo, and Yamaha. The Orbital system is also currently used on some small motorcycle and
scooter applications by Aprilla. Certification data from various engines certified with DI have
shown HC and CO emission reductions of 60 to 75 percent from baseline emission levels.
There is at least one other injection technology that has had success in small two-stroke
SI engines used in lawn and garden applications, such as trimmers and chainsaws. Compression
Wave technology, referred to as Low Emission (LE) technology, developed by John Deere, uses
a compressed air assisted fuel injection system, similar to the Orbital system, to reduce the
unburned fuel charge during the scavenging process of the exhaust portion of the two-stroke
cycle. The system has shown the ability to reduce HC and CO emissions by up to 75 percent
from baseline levels. Although this technology has not yet been applied to any recreational
vehicle engines, it appears to have significant potential, especially because of its simplistic
design and low cost. For a detailed description of the LE technology, refer to the Nonroad Small
SI regulatory support document.
3.2.2.5 Exhaust Aftertreatment Technologies
There are two exhaust aftertreatment technologies that can provide additional emission
reductions from two-stroke engines: thermal oxidation (e.g., secondary air) and oxidation
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catalyst. Thermal oxidation reduces HC and CO by promoting further oxidation of these species
in the exhaust. The oxidation usually takes place in the exhaust port or pipe, and may require the
injection of additional air to supply the needed oxygen. If the exhaust temperature can be
maintained at a high enough temperature (e.g., 600 to 700°C) for a long enough period,
substantial reductions in HC and CO can occur. Air injection at low rates into the exhaust
system has been shown to reduce emissions by as much as 77 percent for HC and 64 percent for
CO.d However, this was effective only under high-power operating conditions, and the high
exhaust temperatures required to achieve this oxidation substantially increased the skin
temperature of the exhaust pipe, which can be a concern for off-highway motorcycle applications
where the operators legs could come in contact with the pipe.
Like thermal oxidation, the oxidation catalyst is used to promote further oxidation of HC
and CO emissions in the exhaust stream, and it also requires sufficient oxygen for the reaction to
take place. Some of the requirements for a catalytic converter to be used in two-stroke engines
include high HC conversion efficiency, resistance to thermal damage, resistance to poisoning
from sulfur and phosphorus compounds in lubricating oil, and low light-off temperature.
Additional requirements for catalysts to be used in recreational vehicle two-stroke engines
include extreme vibration resistance, compactness, and light weight.
Application of catalytic converters to two-stroke engines presents a problem, because of
the high concentrations of HC and CO in their exhaust. If combined with sufficient air, these
high pollutant concentrations result in catalyst temperatures that can easily exceed the
temperature limits of the catalyst. Therefore, the application of oxidation catalysts to two-stroke
engines may first require engine modifications to reduce HC and CO and may also require
secondary air be supplied to the exhaust in front of the catalyst.
Researchers of Graz University of Technology and the Industrial Technology Research
Institute (ITRI) in Taiwan have published data on the application of catalytic converters in small
two-stroke moped and motorcycle engines using catalytic converters. The Graz researchers
focused on reducing emissions using catalysts, as well as by improving the thermodynamic
characteristics of the engines, such as gas exchange and fuel handling systems, cylinder and
piston geometry and configurations, and exhaust cooling systems. For HC and CO emissions,
they found that an oxidation catalyst could reduce emissions by 88 to 96 percent. Researchers at
ITRI successfully retrofitted a catalytic converter to a 125 cc two-stroke motorcycle engine, and
demonstrated both effective emissions control and durability.6 The Manufacturers of Emission
Controls Association (MECA)in their publication titled "Emission Control of Two-and Three-
d White, J.J., Carroll,J.N., Hare, C.T., andLourenco, J.G. (1991), "Emission Control
Strategies for Small Utility Engines," SAE Paper No. 911807, Society of Automotive Engineers,
Warrendale, PA, 1991.
e Hsien, P.H., Hwang, L.K., and Wang, H.W> (1992), "Emission Reduction by
Retrofitting a 125 cc Two-Stroke Motorcycle with Catalytic Converter," SAE Paper No. 922175,
Society of Automotive Engineers, Warrendale, PA, 1992.
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wheel Vehicles," published May 7, 1999, state that catalyst technology has clearly demonstrated
the ability to achieve significant emissions reductions from two-stroke engines. MECA points to
the success of two-stroke moped and motorcycle engines equipped with catalysts that have been
operating for several years in Taiwan, Thailand, Austria, and Switzerland.
3.2.3 Current Four-Stroke Engines
Four-stroke engines are the most common engine today. Large nonroad SI engines are
exclusively four-stroke. Recreational vehicles are also predominantly four-stroke. Four-stroke
engines have considerably lower HC emissions than two-stroke engines, due to the fact that four-
stroke engines do not experience short circuiting of raw fuel. CO emissions from four-stroke
engines is very similar to two-stroke engines, since CO emissions are the result of inefficient
combustion of the air-fuel mixture within the cylinder, typically resulting from rich operation.
Since the combustion of fuel within the cylinder of a four-stroke engine is more efficient than
that of a two-stroke engine, combustion temperatures are higher, which results in higher NOx
emission levels.
The four-stroke engines covered under this proposal are typically either automotive
engines (large nonroad SI) or motorcycle-like engines (including ATVs). Large nonroad SI
engines, off-highway motorcycles, ATVs, and snowmobiles are unregulated federally.
Therefore, while they have relatively low HC emissions compared to two-stroke engines, they
can still have high levels of CO (due to rich air-fuel calibration) and NOx. Table 3.2-3 shows
baseline emission levels for four-stroke equipped off-highway motorcycles and ATVs.
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Table 3.2-3
Baseline Four-Stroke Emissions From Off-Highway Motorcycles & ATVs (g/km)
MCor
ATV
MC
MC
MC
MC
ATV
ATV
ATV
ATV
ATV
Manufacturer
Yamaha
Yamaha
KTM
Husaberg
Kawasaki
Honda
Polaris
Yamaha
Polaris
Model
WR250F
WR400
400EXC
FE501
Bayou
300EX
Trail Boss
Banshee
Sportsman
Model
Year
20001
1999
2001
2001
1989
1997
1998
1998
2001
Eng. Displ.
249 cc
399 cc
398 cc
499 cc
280 cc
298 cc
325 cc
349 cc
499 cc
Average
HC
1.46
1.07
1.17
1.30
1.17
1.14
1.56
0.98
2.68
1.39
CO
26.74
20.95
28.61
25.81
14.09
34.60
43.41
19.44
56.50
30.01
NOx
0.110
0.112
0.050
0.163
0.640
0.155
0.195
0.190
0.295
0.212
3.2.4 Clean Four-Stroke Technologies
The emission control technologies for four-stroke engines are very similar to those used
for two-stroke engines. HC and CO emissions from four-stroke engines are primarily the result
of poor in-cylinder combustion. Higher levels of NOx emissions are the result of leaner air-fuel
ratios and the resulting higher combustion temperatures. Combustion chamber modifications can
help reduce HC emission levels, while using improved air-fuel ratio and spark timing
calibrations, as discussed in sections 3.1.3.1 and 3.1.3.2, can further reduce HC emissions and
lower CO emissions. The conversion from carburetor to EFI will also help reduce HC and CO
emissions. The use of exhaust gas recirculation on large SI engines can reduce NOx emissions,
but is not necessarily needed for recreational vehicles, due to their relatively low NOx emission
levels. The addition of secondary air into the exhaust can significantly reduce HC and CO
emissions. Finally, the use catalytic converters can further reduce all three emissions.
3.2.4.1 Combustion chamber design
Unburned fuel can be trapped momentarily in crevice volumes (especially the space
between the piston and cylinder wall) before being released into the exhaust. Reducing crevice
volumes decreases this amount of unburned fuel, which reduces HC emissions. One way to
reduce crevice volumes is to design pistons with piston rings closer to the top of the piston. HC
may be reduced by 3 to 10 percent by reducing crevice volumes, with negligible effects on NOx
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Chapter 3: Technology
emissions.4
HC emissions also come from lubricating oil that leaks into the combustion chamber.
The heavier hydrocarbons in the oil generally don't burn completely. Oil in the combustion
chamber can also trap gaseous HC from the fuel and prevent it from burning. For engines using
catalytic control, some components in lubricating oil can poison the catalyst and reduce its
effectiveness, which would further increase emissions over time. To reduce oil consumption,
manufacturers can tighten tolerances and improve surface finishes for cylinders and pistons,
improve piston ring design and material, and improve exhaust valve stem seals to prevent
excessive leakage of lubricating oil into the combustion chamber.
3.2.4.2 Exhaust gas recirculation
Exhaust gas recirculation (EGR) has been in use in cars and trucks for many years. The
recirculated gas acts as a diluent in the air-fuel mixture, slowing reaction rates and absorbing heat
to reduce combustion temperatures. These lower temperatures can reduce the engine-out NOx
formation rate by as much as 50 percent.5 HC is increased slightly due to lower temperatures for
HC burn-up during the late expansion and exhaust strokes.
Depending on the burn rate of the engine and the amount of recirculated gases, EGR can
improve fuel consumption. Although EGR slows the burn rate, it can offset this effect with some
benefits for engine efficiency. EGR reduces pumping work since the addition of recirculated gas
increases intake pressure. Because the burned gas temperature is decreased, there is less heat
loss to the exhaust and cylinder walls. In effect, EGR allows more of the chemical energy in the
fuel to be converted to useable work.6
For catalyst systems with high conversion efficiencies, the benefit of using EGR becomes
proportionally smaller. Also, including EGR as a design variable for optimizing the engine adds
significantly to the development time needed to fully calibrate engine models.
3.2.4.3 Secondary air
Secondary injection of air into exhaust ports or pipes after cold start (e.g., the first 40-60
seconds) when the engine is operating rich, coupled with spark retard, can promote combustion
of unburned HC and CO in the exhaust manifold and increase the warm-up rate of the catalyst.
By means of an electrical or mechanical pump, secondary air is injected into the exhaust system,
preferably in close proximity of the exhaust valve. Together with the oxygen of the secondary air
and the hot exhaust components of HC and CO, oxidation ahead of the catalyst can bring about
an efficient increase in the exhaust temperature which helps the catalyst to heat up quicker. The
exothermic reaction that occurs is dependent on several parameters (secondary air mass, location
of secondary air injection, engine A/F ratio, engine air mass, ignition timing, manifold and
headpipe construction, etc.), and ensuring reproducibility demands detailed individual
application for each vehicle or engine design.
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Secondary air injection was first used as an emission control technique in itself without a
catalyst, and still is used for this purpose in many highway motorcycles and some off-highway
motorcycles to meet federal and California emission standards. For motorcycles, air is usually
provided or injected by a system of check valves which uses the normal pressure pulsations in the
exhaust manifold to draw in air from outside, rather than by a pump.
3.2.4.4 Catalytic Aftertreatment
Over the last several years, there have been tremendous advances in exhaust
aftertreatment systems. Catalyst manufacturers are progressively moving to palladium (Pd) as
the main precious metal in automotive catalyst applications. Improvements to catalyst thermal
stability and washcoat technologies, the design of higher cell densities, and the use of two-layer
washcoat applications are just some of the advances made in catalyst technology. There are two
types of catalytic converters commonly used: oxidation and three-way. Oxidation catalysts use
platinum and/or palladium to increase the rate of reaction between oxygen in the exhaust and
unburned HC and CO. Ordinarily, this reaction would proceed very slowly at temperatures
typical of engine exhaust. The effectiveness of the catalyst depends on its temperature, on the
air-fuel ratio of the mixture, and on the mix of HC present. Highly reactive species such as
formaldehyde and olefms are oxidized more effectively than less-reactive species. Short-chain
paraffins such as methane, ethane, and propane are among the least reactive HC species, and are
difficult to oxidize.
Three-way catalysts use a combination of platinum and/or pallabium and rhodium. In
addition to promoting oxidation of HC and CO, these metals also promote the reduction of NO to
nitrogen and oxygen. In order for the NO reduction to occur efficiently, an overall rich or
stoichiometric air-fuel ratio is requires. The NOx efficiency drops rapidly as the ai-fuel ratio
becomes leaner than stoichiometric. If the air-fuel ratio can be maintained precisely at or just
rich of stoichiometic, a three-way catalyst can simultaneously oxidize HC and CO and reduce
NOx. The window of air-fuel ratios within which this is possible is very narrow and there is a
trade-off between NOx and HC/CO control even within this window.
There are several issues involved in designing catalytic control systems for the four-
stroke engines covered by this proposal. The primary issues are the cost of the system, packaging
constraints, and the durability of the catalyst. This section addresses these issues.
3.2.4.4.1. System cost
Sales volumes of industrial and recreational equipment are small compared to automotive
sales. Manufacturers therefore have a limited ability to recoup large R&D expenditures for Large
SI and recreational engines. For this reason, we believe it is not appropriate to consider highly
refined catalyst systems that are tailored specifically to nonroad applications. For large SI
engines, we have based the feasibility of the emission standards on the kind of catalysts that
manufacturers have already begun to offer for these engines. These systems are currently
produced in very low volumes, but the technology has been successfully adapted to Large SI
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Chapter 3: Technology
engines. The cost of these systems will decrease substantially when catalysts become
commonplace. This approach is also true for phase 2 ATV standards that may require catalysts
for some models. Chapter 4 describes the estimated costs for a nonroad catalyst system.
3.2.4.4.2 Packaging constraints
Large SI engines power a wide range of nonroad equipment. Some of these have no
significant space constraints for adding a catalyst. In contrast, equipment designs such as
forklifts have been fine-tuned over many years with a very compact fit. The same is even more
true for recreational vehicles, such as ATVs and motorcycles.
Automotive catalyst designs typically have one or two catalyst units upstream of the
muffler. This is a viable option for most nonroad equipment. However, if there is no available
space to add a separate catalyst, it is possible to build a full catalyst/muffler combination that fits
in the same space as the conventional muffler. With this packaging option, even compact
applications should have little or no trouble integrating a catalyst into the equipment design. The
hundreds of catalysts currently operating on forklifts and highway motorcycles clearly
demonstrate this.
3.2.5 Advanced Emission Controls
On February 10, 2000, EPA published new "Tier 2" emissions standards for all passenger
vehicles, including sport utility vehicles (SUVs), minivans, vans and pick-up trucks. The new
standards will ensure that exhaust VOC emissions be reduced to less than 0.1 g/mi on average
over the fleet, and that evaporative emissions be reduced by at least 50 percent. Onboard
refueling vapor recovery requirements were also extended to medium-duty passenger vehicles.
By 2020, these standards will reduce VOC emissions from light-duty vehicles by more than 25
percent of the projected baseline inventory. (See Chapter 4 for a more detailed discussion of the
impact of the Tier 2 FRM on VOC inventories.) To achieve these reductions, manufacturers will
need to incorporate advanced emission controls, including: larger and improved close-coupled
catalysts, optimized spark timing and fuel control, improved exhaust systems.
To reduce emissions gasoline-fueled vehicle manufacturers have designed their engines to
achieve virtually complete combustion and have installed catalytic converters in the exhaust
system. In order for these controls to work well for gasoline-fueled vehicles, it is necessary to
maintain the mixture of air and fuel at a nearly stoichiometric ratio (that is, just enough air to
completely burn the fuel). Poor air-fuel mixture can result in significantly higher emissions of
incompletely combusted fuel. Current generation highway vehicles are able to maintain
stoichiometry by using closed-loop electronic feedback control of the fuel systems. As part of
these systems, technologies have been developed to closely meter the amount of fuel entering the
combustion chamber to promote complete combustion. Sequential multi-point fuel injection
delivers a more precise amount of fuel to each cylinder independently and at the appropriate time
increasing engine efficiency and fuel economy. Electronic throttle control offers a faster
response to engine operational changes than mechanical throttle control can achieve, but it is
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currently considered expensive and only used on some higher-price vehicles. The greatest gains
in fuel control can be made through engine calibrations — the algorithms contained in the
powertrain control module (PCM) software that control the operation of various engine and
emission control components/systems. As microprocessor speed becomes faster, it is possible to
perform quicker calculations and to increase response times for controlling engine parameters
such as fuel rate and spark timing. Other advances in engine design have also been used to
reduce engine-out emissions, including: the reduction of crevice volumes in the combustion
chamber to prevent trapping of unburned fuel; "fast burn" combustion chamber designs that
promote swirl and flame propagation; and multiple valves with variable-valve timing to reduce
pumping losses and improve efficiency. These technologies are discussed in more detail in the
RIA for the Tier 2 FRM.f
As noted above, manufacturers are also using aftertreatment control devices to control
emissions. New three-way catalysts for highway vehicles are so effective that once a TWC
reaches its operating temperature, emissions are virtually undetectable.g Manufacturers are now
working to improve the durability of the TWC and to reduce light-off time (that is, the amount of
time necessary after starting the engine before the catalyst reaches its operating temperature and
is effectively controlling VOCs and other pollutants). EPA expects that manufacturers will be
able to design their catalyst systems so that they light off within less than thirty seconds of engine
starting. Other potential exhaust aftertreatment systems that could further reduce cold-start
emissions are thermally insulated catalysts, electrically heated catalysts, and HC adsorbers (or
traps). Each of these technologies, which are discussed below, offer the potential for VOC
reductions in the future. There are technological, implementation, and cost issues that still need
to be addressed, and at this time, it appears that these technologies would not be a cost-effective
means of reducing nonroad emissions on a nationwide basis.
Thermally insulated catalysts maintain sufficiently high catalyst temperatures by
surrounding the catalyst with an insulating vacuum. Prototypes of this technology have
demonstrated the ability to store heat for more than 12 hours.11 Since ordinary catalysts typically
cool down below their light-off temperature in less than one hour, this technology could reduce
in-use emissions for vehicles that have multiple cold-starts in a single day. However, this
technology would have less impact on emissions from vehicles that have only one or two cold-
starts per day.
Electrically-heated catalysts reduce cold-start emissions by applying an electric current to
the catalyst before the engine is started to get the catalyst up to its operating temperature more
f http://www.epa.gov/otaq/tr2home.htmtfDocuments. EPA 420-R-99-023
8 McDonald, J., L. Jones, Demonstration of Tier 2 Emission Levels for Heavy Light-Duty Trucks, SAE
2000-01-1957.
h Burch, S.D., and J.P. Biel, SULEV and "Off-Cycle" Emissions Benefits of a Vacuum-Insulated Catalytic
Convert, SAE 1999-01-0461.
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Chapter 3: Technology
quickly.1 These systems require a modified catalyst, as well as an upgraded battery and charging
system. These can greatly reduce cold-start emissions, but could require the driver to wait until
the catalyst is heated before the engine would start to achieve optimum performance.
Hydrocarbon adsorbers are designed to trap VOCs while the catalyst is cold and unable to
sufficiently convert them. They accomplish this by utilizing an adsorbing material which holds
onto the VOC molecules. Once the catalyst is warmed up, the trapped VOCs are automatically
released from the adsorption material and are converted by the fully functioning downstream
three-way catalyst. There are three principal methods for incorporating an adsorber into the
exhaust system. The first is to coat the adsorber directly on the catalyst substrate. The advantage
is that there are no changes to the exhaust system required, but the desorption process cannot be
easily controlled and usually occurs before the catalyst has reached light-off temperature. The
second method locates the adsorber in another exhaust pipe parallel with the main exhaust pipe,
but in front of the catalyst and includes a series of valves that route the exhaust through the
adsorber in the first few seconds after cold start, switching exhaust flow through the catalyst
thereafter. Under this system, mechanisms to purge the adsorber are also required. The third
method places the trap at the end of the exhaust system, in another exhaust pipe parallel to the
muffler, because of the low thermal tolerance of adsorber material. Again a purging mechanism
is required to purge the adsorbed VOCs back into the catalyst, but adsorber overheating is
avoided. One manufacturer who incorporates a zeolite hydrocarbon adsorber in its California
SULEV vehicle found that an electrically heated catalyst was necessary after the adsorber
because the zeolite acts as a heat sink and nearly negates the cold start advantage of the adsorber.
This approach has been demonstrated to effectively reduce cold start emissions.
3.2.5.1 Multiple valves and variable valve timing
Four-stroke engines generally have two valves for each cylinder, one for intake of the air-
fuel mixture and the other for exhaust of the combusted mixture. The duration and lift (distance
the valve head is pushed away from its seat) of valve openings is constant regardless of engine
speed. As engine speed increases, the aerodynamic resistance to pumping air in and out of the
cylinder for intake and exhaust also increases. Automotive engines have started to use two
intake and two exhaust valves to reduce pumping losses and improve their volumetric efficiency
and useful power output. Some highway motorcycles have used multiple valves for years,
especially the high-performance sport motorcycles.
In addition to gains in breathing, 4-valve designs allow the spark plug to be positioned
closer to the center of the combustion chamber, which decreases the distance the flame must
travel inside the chamber. This decreases the likelihood of flame-out conditions in the areas of
the combustion chamber farthest from the spark plug. In addition, the two streams of incoming
gas can be used to achieve greater mixing of air and fuel, further increasing combustion
efficiency and lowering engine-out emissions.
1 Laing, P.M., Development of an Alternator-Powered Electrically-Heated Catalyst System, SAE 941042.
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Control of valve timing and lift take full advantage of the 4-valve configuration for even
greater improvement in combustion efficiency. Engines normally use fixed-valve timing and lift
across all engine speeds. If the valve timing is optimized for low-speed torque, it may offer
compromised performance under higher-speed operation. At light engine loads, for example, it
is desirable to close the intake valve early to reduce pumping losses. Variable-valve timing can
enhance both low-speed and high-speed performance with compromise. Variable-valve timing
can allow for increased swirl and intake charge velocity, especially during low-load operating
conditions where this is most problematic. By providing a strong swirl formation in the
combustion chamber, the air-fuel mixture can mix sufficiently, resulting in a faster, more
complete combustion, even under lean air-fuel conditions, thereby reducing emissions.
Variable-valve technology by itself may have somewhat limited effect on reducing
emissions, but combining it with optimized spark plug location and exhaust gas recirculation can
lead to substantial emission reductions.
3.3 Evaporative Emissions
3.3.1 Sources of Evaporative Emissions
Evaporative emissions from nonroad SI equipment represents a small but significant part
of their NMHC emissions. The significance of the emissions varies widely depending on the
engine design and application. LPG-fueled equipment generally has very low evaporative
emissions because of the tightly sealed fuel system. At the other extreme, carbureted
gasoline-fueled equipment with open vented tanks can have very high evaporative emissions.
Evaporative emissions can be grouped into five categories:
DIURNAL: Gasoline evaporation increases as the temperature rises during the day,
heating the fuel tank and venting gasoline vapors.
RUNNING LOSSES: The hot engine and exhaust system can vaporize gasoline when the
engine is running.
HOT SOAK: The engine remains hot for a period of time after the engine is turned off
and gasoline evaporation continues.
REFUELING: Gasoline vapors are always present in typical fuel tanks. These vapors are
forced out when the tank is filled with liquid fuel.
PERMEATION: Gasoline molecules can saturate plastic fuel tanks and rubber hoses,
resulting in a relatively constant rate of emissions as the fuel continues to permeate through these
components.
Among the factors that affect emission rates are: (1) fuel metering (fuel injection or
carburetor); (2) the degree to which fuel permeates fuel lines and fuel tanks; (3) the proximity of
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the fuel tank to the exhaust system or other heat sources; (4) whether the fuel system is sealed
and the pressure at which fuel vapors are vented; and (5) fuel tank volume.
3.3.1.1 Diurnal and Running Loss Emissions
In an open fuel tank, the vapor space is at atmospheric pressure (typically about 14.7 psi),
and contains a mixture of fuel vapor and air. At all temperatures below the fuel's boiling point,
the vapor pressure of the fuel is less than atmospheric pressure. This is also called the partial
pressure of the fuel vapor. The partial pressure of the air is equal to the difference between
atmospheric pressure and the fuel vapor pressure. For example, in an open-vented fuel tank at
60°F, the vapor pressure of typical gasoline would be about 4.5 psi. In this example, the partial
pressure of the air would be about 10.2 psi. Assuming that the vapor mixture behaves as an ideal
gas, then the mole fractions (or volumetric fractions) of fuel vapor and air would be equal to their
respective partial pressures divided by the total pressure; thus, the fuel would be 31 percent of the
mixture (4.5/14.7) and the air would be 69 percent of the mixture (10.2/14.7).
Diurnal emissions occur when the fuel temperature increases, which increases the
equilibrium vapor pressure of the fuel. For example, assume that the fuel in the previous
example was heated to 90°F, where the vapor pressure that same typical fuel would be about 8.0
psi. To maintain the vapor space at atmospheric pressure, the partial pressure of the air would
need to decrease to 6.7 psi, which means that the vapor mixture must expand in volume. This
forces some of the fuel-air mixture to be vented out of the tank. When the fuel later cools, the
vapor pressure of the fuel decreases, contracting the mixture, and drawing fresh air in through the
vent. When the fuel is heated again, another cycle of diurnal emissions occurs. It is important to
note that this is generally not a rate-limited process. Although the evaporation of the fuel can be
slow, it is generally fast enough to maintain the fuel tank in an essentially equilibrium state.
Consider a typical fuel use cycle beginning with a full tank. As fuel is used by the engine,
and the liquid fuel volume decreases, air is drawn into the tank to replace the volume of the fuel.
(Note: the decrease in liquid fuel could be offset to some degree by increasing fuel vapor
pressure caused by increasing fuel temperature.) This would continue while the engine was
running. If the engine was shut off and the tank was left overnight, the vapor pressure of the fuel
would drop as the temperature of the fuel dropped. This would cause a small negative pressure
within the tank that would cause it to fill with more air until the pressure equilibrated. The next
day, the vapor pressure of the fuel would increase as the temperature of the fuel increased. This
would cause a small positive pressure within the tank that would force a mixture of fuel vapor
and air out. In poorly designed gasoline systems, where the exhaust is very close to the fuel tank,
the fuel can actually begin to boil. When this happens, large amounts of gasoline vapor can be
vented directly to the atmosphere. Southwest Research Institute measured emissions from
several large nonroad gasoline engines and found them to vary from about 12 g/day up to almost
100 g/day. They also estimated that a typical large nonroad gasoline engine in the South Coast
Air Basin (the area involved in their study) would have an evaporative emission rate of about 0.4
g/kW-hr.
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3.3.1.2 Hot Soak Emissions
Hot soak emissions occur after the engine is turned off, especially during the resulting
temperature rise. For nonroad engines, the primary source of hot soak emissions is the
evaporation of the fuel left in the carburetor bowl. Other sources can include increased
permeation and evaporation of fuel from plastic or rubber fuel lines in the engine compartment.
3.3.1.3 Refueling Emissions
Refueling emissions occur when the fuel vapors are forced out when the tank is filled
with liquid fuel. At a given temperature, refueling emissions are proportional to the volume of
the fuel dispensed into the tank. Every gallon of fuel put into the tank forces out one-gallon of
the mixture of air and fuel vapors. Thus, refueling emissions are highest when the tank is near
empty. Refueling emissions are also affected by the temperature of the fuel vapors. At low
temperatures, the fuel vapor content of the vapor space that is replaced is lower than it is at
higher temperatures.
3.3.1.4 Permeation
The polymeric material (plastic or rubber) of which many gasoline fuel tanks and fuel
hoses generally have a chemical composition much like that of gasoline. As a result, constant
exposure of gasoline to these surfaces allows the material to continually absorb fuel. The outer
surfaces of these materials are exposed to ambient air, so the gasoline molecules permeate
through these fuel-system components and are emitted directly into the air. Permeation rates are
relatively low, but emissions continue at a nearly constant rate, regardless of how much the
vehicle or equipment is used. Permeation-related emissions can therefore
3.3.2 Evaporative Emission Controls
Several emission-control technologies can be used to reduce evaporative emissions. The
advantages and disadvantages of the various possible emission-control strategies are discussed
below. Chapter 4 presents more detail on how we expect manufacturers to use these
technologies to meet proposed emission standards for the individual applications.
3.3.2.1 Sealed System with Pressure Relief
Evaporative emissions are formed when the fuel heats up, evaporates, and passes through
a vent into the atmosphere. By closing that vent, evaporative emissions are prevented from
escaping. However, as vapor is generated, pressure builds up in fuel tank. Once the fuel cools
back down, the pressure subsides.
For forklifts, the primary application of Large SI engines, Underwriters Laboratories
specifies that units operating in certain areas where fire risk is most significant must use
pressurized fuel tanks. Underwriters Laboratories requires that trucks use self-closing fuel caps
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Chapter 3: Technology
with tanks that stay sealed to prevent evaporative losses; venting is allowed for positive pressures
above 3.5 psi or for vacuum pressures of at least 1.5 psi.j These existing requirements are
designed to prevent evaporative losses for safety reasons. This same approach for other types of
engines would similarly reduce emissions for air-quality reasons.
An alternative to using a pressure relief valve to hold vapors in the fuel tank would be to
use a limited flow orifice. However, the orifice size may be so small that there would be a risk of
fouling. In addition, an orifice designed for a maximum of 2 psi under worst case conditions
may not be very effective at lower temperatures. One application where a limited flow orifice
may be useful is if it is combined with an insulated fuel tank as discussed below.
3.3.2.2 Insulated Fuel Tank
Another option for reducing diurnal emissions is insulating the fuel tank. Rather than
capturing the vapors in the fuel tank, this strategy would minimize the fuel heating which
therefore minimizes the vapor generation. However, significant evaporative emissions would
still occur through the vent line due to diffusion even without temperature gradients. A limited-
flow orifice could be used to minimize the to loss of vapor through the vent line due to diffusion.
In this case, the orifice could be sized to prevent diffusion losses without causing pressure build-
up in the tank. Additional control could be achieved with the use of a pressure relief valve or a
smaller limited flow orifice. Note that an insulated tank could maintain the same emission
control with a lower pressure valve than a tank that was not insulated.
3.3.2.3 Volume Compensating Air Bag
Another concept for minimizing pressure in a sealed fuel tank is through the use of a
volume compensating air bag. The purpose of the bag is to fill up the vapor space in the fuel
tank above the fuel itself. By minimizing the vapor space, less air is available to mix with the
heated fuel and less fuel evaporates. As vapor is generated in the small vapor space, air is forced
out of the air bag, which is vented to atmosphere. Because the bag collapses as vapor is
generated, the volume of the vapor space grows and no pressure is generated. Once the fuel tank
cools as ambient temperature goes down, the resulting vacuum in the fuel tank will open the bag
back up. Depending on the size of the bag, pressure in the tank could be minimized; therefore,
the use of a volume compensating air bag could allow a manufacturer to reduce the pressure limit
on its relief valve.
We are still investigating materials that would be the most appropriate for the
construction of these bags. The bags would have to hold up in a fuel tank for years and resist
permeation while at the same time be light and flexible. One such material that we are
considering is fluoro-silicon fiber. Also, the bag would have to be positioned so that it did not
interfere with other fuel system components such as the fuel pick-up or catch on any sharp edges
JUL558, paragraphs 26.1 through 26.4
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Draft Regulatory Support Document
in the fuel tank.
3.3.2.4 Collapsible Bladder Fuel Tank
Probably the most effective technology for reducing evaporative emissions from fuel
tanks is through the use of a collapsible fuel bladder. In this concept, a non-permeable bladder
would be installed in the fuel tank to hold the fuel. As fuel is drawn from the bladder, the
vacuum created collapses the bladder. Therefore, there is no vapor space and no pressure build
up. Because the bladder would be sealed, there would be no vapors vented to the atmosphere.
We have received comments that this would be cost prohibitive because it could double costs for
smaller fuel tanks. However, bladder fuel tanks are sold today by at least one manufacturer in
limited volumes.
3.3.2.5 Charcoal Canister
The primary evaporative emission control device used in automotive applications is a
charcoal canister. With this technology, vapor generated in the tank is vented through a charcoal
canister. The activated charcoal collects and stores the hydrocarbons. Once the engine is
running, purge air is drawn through the canister and the hydrocarbons are burned in the engine.
These charcoal canisters generally are about a liter in size and have the capacity to store three
days of vapor over the test procedure conditions.
For industrial applications, engines are typically used frequently which would limit the
size of canister needed; however, introducing an evaporative canister is a complex undertaking,
requiring extensive efforts to integrate evaporative and exhaust emission-control strategies.
Large SI engine manufacturers also often sell loose engines to equipment manufacturers, who
would also need to integrate the new technology into equipment designs.
3.3.2.6 Floating Fuel and Vapor Separator
Another concept used in some stationary engine applications is a floating fuel and vapor
separator. Generally small, impermeable plastic balls are floated in the fuel tank. The purpose of
these balls is to provide a barrier between the surface of the fuel and the vapor space. However,
this strategy does not appear to be viable for industrial fuel tanks. Because of the motion of the
equipment, the fuel sloshes and the barrier would be continuously broken. Even small
movements in the fuel could cause the balls to rotate and transfer fuel to the vapor space.
3.3.2.7 Non-permeable Materials
Another source of evaporative emissions is permeation through the walls of plastic fuel
tanks and rubber hoses. In highway applications, non-permeable plastic fuel tanks are typically
produced by blow molding a layer of ethylene vinyl alcohol between two layers of polyethylene.
However, blow molding is expensive and requires high production volumes to be cost effective.
Manufacturers of rotationally molded plastic fuel tanks generally have low production volumes
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Chapter 3: Technology
and have commented that there is no low permeability material available for their production
processes.
Another type of barrier technology for fuel tanks would be to treat the inside of a plastic
fuel tanks with sulfur trioxide. This sulfonation process causes a reaction between the sulfur and
polyethylene which creates a barrier that reduces gasoline permeation. One study shows
reductions in gasoline permeation of 90% through the sulfonation process.7
By replacing rubber hoses with non-permeable lines, the evaporative emissions through
the fuel and vent hoses can be prevented. An added benefit is that these non-permeable lines are
non-conductive and can prevent the buildup of static charges. These non-permeable lines are
used in automotive applications.
3.4 CI Recreational Marine Engines
In this section, we discuss how emissions can be reduced from compression-ignition (CI)
recreational marine engines. We believe recreational marine diesel engines can use the same
technology for reducing emissions that will be used to meet the standards for commercial marine
diesel engines.8 Because of the similarities between recreational and commercial diesel engines,
this chapter builds off the technological analysis in the Regulatory Impact Analysis (RIA) for the
commercial diesel marine engine rule.9 This section discusses emissions formation, baseline
technology, control strategies for CI recreational marine engines.
3.4.1 Background on Emissions Formation from Diesel Engines
Most, if not all, of compression-ignition recreational marine engines use diesel fuel. For
this reason, we focus on recreational marine diesel engines in this section. In a diesel engine, the
liquid fuel is injected into the combustion chamber after the air has been heated by compression
(direct injection), or the fuel is injected into a prechamber, where combustion initiates before
spreading to the rest of the combustion chamber (indirect injection). The fuel is injected in the
form of a mist of fine droplets or vapor that mix with the air. Power output is controlled by
regulating the amount of fuel injected into the combustion chamber, without throttling (limiting)
the amount of air entering the engine. The compressed air heats the injected fuel droplets,
causing the fuel to evaporate and mix with the available oxygen. At several sites where the fuel
mixes with the oxygen, the fuel auto-ignites and the multiple flame fronts spread through the
combustion chamber.
NOx and PM are the emission components of most concern from diesel engines.
Incomplete evaporation and burning of the fine fuel droplets or vapor result in emissions of the
very small particles of PM. Small amounts of lubricating oil that escape into the combustion
chamber can also contribute to PM. Although the fuel-air ratio in a diesel cylinder is very lean,
the air and fuel are not a homogeneous charge as in a gasoline engine. As the fuel is injected, the
combustion takes place at the flame-front where the fuel-air ratio is near stoichiometry
(chemically correct for combustion). At localized areas, or in cases where light-ends have
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vaporized and burned, molecules of carbon remain when temperatures and pressures in the
cylinder become too low to sustain combustion as the piston reaches bottom dead center.
Therefore, these heavy products of incomplete combustion are exhausted as PM.
NOx formation requires high temperatures and excess oxygen which are found in a diesel
engine. Therefore, the diesel combustion process can cause the nitrogen in the air to combine
with available oxygen to form NOx. High peak temperatures can be seen in typical unregulated
diesel engine designs. This is because the fuel is injected early to help lead to more complete
combustion, therefore, higher fuel efficiency. If fuel is injected too early, significantly more fuel
will mix with air prior to combustion. Once combustion begins, the premixed fuel will burn at
once leading to a very high temperature spike. This high temperature spike, in turn, leads to a
high rate of NOx formation. Once combustion begins, diffusion burning occurs while the fuel is
being injected which leads to a more constant, lower temperature, combustion process.
Because of the presence of excess oxygen, hydrocarbons evaporating in the combustion
chamber tend to be completely burned and HC and CO are not emitted at high levels.
Evaporative emissions from diesel engines are insignificant due to the low evaporation rate of
diesel fuel.
Controlling both NOx and PM emissions requires different, sometimes opposing
strategies. The key to controlling NOx emissions is reducing peak combustion temperatures
since NOx forms at high temperatures. In contrast, the key to controlling PM is higher
temperatures in the combustion chamber or faster burning. This reduces PM by decreasing the
formation of particulates and by oxidizing those particulates that have formed. To control both
NOx and PM, manufacturers need to combine approaches using many different design variables
to achieve optimum performance. These design variables are discussed in more detail below.
3.4.2 Marinization Process
Like commercial marine engines, recreational marine engines are not generally built from
the ground up as marine engines. Instead, they are often marinized land-based engines. The
main difference between recreational and commercial marine engines is the application for which
they are designed. Commercial engines are designed for high hours of use. Recreational engines
are generally designed for higher power, but less hours of use. The following is a brief
discussion of the marinization process, as it is performed by either engine manufacturers or post-
manufacture marinizers (PMM).
3.4.2.1 Process common to all marine diesel engines
The most obvious changes made to a land-based engine as part of the marinization
process concern the engine's cooling system. Marine engines generally operate in closed
compartments without much air flow for cooling. This restriction can lead to engine
performance and safety problems. To address engine performance problems, these engines make
use of the ambient water to draw the heat out of the engine coolant. To address safety problems,
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Chapter 3: Technology
marine engines are designed to minimize hot surfaces. One method of ensuring this, used mostly
on smaller marine engines, is to run cooling water through a jacket around the exhaust system
and the turbocharger. Larger engines generally use a thick insulation around the exhaust pipes.
Hardware changes associated with these cooling system changes often include water
jacketed turbochargers, water cooled exhaust manifolds, heat exchangers, sea water pumps with
connections and filters, and marine gear oil coolers. In addition, because of the greater cooling
involved, it is often necessary to change to a single-chamber turbocharger, to avoid the cracking
that can result from a cool outer wall and a hot chamber divider.
Marinization may also involve replacing engine components with similar components
that are made of materials that are more carefully adapted to the marine environment. Material
changes include more use of chrome and brass including changes to electronic fittings to resist
water induced corrosion. Zinc anodes are often used to prevent engine components, such as raw-
water heat exchangers, from being damaged by electrolysis.
3.4.2.2 Process unique to recreational marine diesel engines
Other important design changes are related to engine performance. Especially for planing
hull vessels used in recreational and light duty commercial marine applications, manufacturers
strive to maximize the power-to-weight ratio of their marine engines, typically by increasing the
power from a given cylinder displacement. The most significant tool to accomplish this is the
fuel injection system: the most direct way to increase power is to inject more fuel. This can
require changes to the camshaft, cylinder head, and the injection timing and pressure.
Design limits for increased fuel to the cylinder are smoke and durability. Modifications
made to the cooling system also help enhance performance. By cooling the charge, more air can
be forced into the cylinder. As a result, more fuel can be injected and burned efficiently due to
the increase in available oxygen. In addition, changes are often made to the pistons, cylinder
head components, and the lubrication system. For instance, aluminum piston skirts may be used
to reduce the weight of the pistons. Cylinder head changes include changing valve timing to
optimize engine breathing characteristics. Increased oil quantity and flow may be used to
enhance the durability of the engine.
Depending on the stage of production and the types of changes made, the marinization
process can have an impact on the base engine's emission characteristics. In other words, a land-
based engine that meets a particular set of emission limits may no longer meet these limits after it
is marinized. This can be the case, for example, if the fuel system is changed to enhance engine
power or if the cooling system no longer achieves the same degree of engine cooling as that of
the base engine. Because marine diesel engines are currently unregulated, engine manufacturers
have been able to design their marine engines to maximize performance. Especially for
recreational marine engines, manufacturers often obtain power/weight ratios much higher than
for land-based applications.
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Recreational engine manufacturers strive for higher power/weight ratios than are
necessary for commercial marine engines. Because of this, recreational marine engines use
technology we projected to be used by commercial marine engines to meet the Tier 2 emissions
standards such as raw-water aftercooling and electronic control. However, this technology is
used to gain more power rather than to reduce emissions. The challenge presented by the
proposed emission control program will be to achieve the emission limits while maintaining
favorable performance characteristics.
3.4.3 General Description of Technology for Recreational Marine Diesel Engines
We believe that the proposed standards can be met using technology that has been
developed for and used on land-based nonroad and highway engines. The Regulatory Impact
Analysis for the commercial marine rule includes a lengthy description of emission control
technology for diesel marine engines. Table 3.4-1 outlines this description. By combining the
strategies shown below, manufacturers can optimize the emissions and performance of their
engines. A more detailed analysis of the application of several of these technologies to
recreational marine engines is discussed in Chapter 4. The costs associated with applying these
systems are considered in Chapter 5.
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Chapter 3: Technology
Table 3.4-1: Emission Control Strategies for Marine Diesel Engines
Technology
Combustion
optimization:
Advanced fuel
injection
controls
Improving
charge air
characteristics
Electronic
control
Exhaust gas
recirculation
Exhaust
aftertreatment
devices
(would require
"dry" exhaust)
Water
emulsification
Description
timing retard-reduce peak cylinder temperatures by shortening
the premixed burning phase
reduced crevice volume-such as raising the top piston ring
geometry-match piston crown geometry to injector spray
increased compression ratio-raises cylinder pressures
increased swirl-control of air motion for better mixing
increased injection pressure-better atomization of fuel
nozzle geometry-optimize spray pattern
valve-closed orifice-minimize leakage after iniection
rate shaping-inject small amount of fuel early to begin
combustion to reduce premixed burning
common rail-high pressure rail to injectors, excellent control of
fuel rate, pressure, and timing
turbocharging-increases available oxygen in the cylinder but
heats intake air
jacket-water aftercooling-uses engine coolant to cool charged
air which increases available oxygen in cylinder
raw-water aftercooling-uses ambient water to cool charge air;
more effective than jacket-water aftercooling; may result in
additional maintenance such as changing anodes
better control of fuel system including rate, pressure, and timing
especially under transients; can use feedback loop
hot EGR-recirculated exhaust gas reduces combustion
temperatures by absorbing heat and slowing reaction rates
cooled EGR-reduces volume of recirculated gases so to allow
more oxygen in the cylinder
soot removal-soot in recirculated gases may cause durability
problems at high EGR rates; gas filter or trap; oil filter
oxidation catalyst-oxidizes hydrocarbons and soluble organic
fraction of PM; will be poisoned by high levels of sulfur
paniculate trap-collect PM: regenerate at high temperature
selective catalytic reduction-uses a catalyst and a reducing
agent such as ammonia
water is mixed with fuel or injected into the cylinder; water has
a high heat capacity and will lower in-cylinder temperatures
HC
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Draft Regulatory Support Document
Chapter 3 References
1. Heywood, J., "Internal Combustion Engine Fundamentals," McGraw-Hill, Inc., New York,
1988, pp.829-836.
2. Heywood, pp.827-829.
3. Saikalis, G., Byers, R., Nogi., T., "Study on Air Assist Fuel Injector Atomization and Effects
on Exhaust Emission Reduction," SAE Paper 930323, 1993, Docket A-2000-01, Document II-A-
55.
4. Energy and Environmental Analysis, "Benefits and Cost of Potential Tier 2 Emission
Reduction Technologies", Final Report, November 1997, Docket A-2000-01, Document n-A-01.
5. Southwest Research Institute, "Three-Way Catalyst Technology for Off-Road Equipment
Powered by Gasoline and LPG Engines," prepared for CARB, CEP A, and SCAQMD, (SwRI
8778), April 1999, Docket A-2000-01, Document H-A-08.
6. Heywood, pp. 836-839.
7. Kathios, D., Ziff, R., Petrulis, A., Bonczyk, J., "Permeation of Gasoline and Gasoline-alcohol
Fuel Blends Through High-Density Polyethylene Fuel Tanks with Different Barrier
Technologies," SAE Paper 920164, 1992, Docket A-2000-01, Document II-A-60.
8. "Control of Emissions of Air Pollution from New Marine Compression-Ignition Engines at or
Above 37 kW; Final Rule," 64 FR 73318, December 29, 1999.
9. Final Regulatory Impact Analysis for "Control of Emissions of Air Pollution from New
Marine Compression-Ignition Engines at or Above 37 kW; Final Rule," November 1999.
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Chapter 4: Feasibility of Proposed Standards
CHAPTER 4: Feasibility of Proposed Standards
Section 213(a)(3) of the Clean Air Act presents statutory criteria that EPA must evaluate
in determining standards for nonroad engines and vehicles. The standards must "achieve the
greatest degree of emission reduction achievable through the application of technology which the
Administrator determines will be available for the engines or vehicles to which such standards
apply, giving appropriate consideration to the cost of applying such technology within the period
of time available to manufacturers and to noise, energy, and safety factors associated with the
application of such technology." This chapter presents the technical analyses and information
that form the basis of EPA's belief that the proposed emission standards are technically
achievable accounting for all the above factors.
4.1 CI Recreational Marine
The proposed emission standards CI recreational marine engines are summarized in the
Executive Summary. We believe that manufacturers will be able to meet these standards using
technology similar to that required for the commercial marine engine standards. This section
discusses technology currently used on CI recreational marine engines and anticipated technology
to meet the proposed standards. In addition, this section discusses the emission test procedures
and not-to-exceed requirements.
4.1.1 Baseline Technology for CI Recreational Marine Engines
We developed estimates of the current mix of technology for CI recreational marine
engines based on data from the 1999 Power Systems Research (PSR) database and from
conversations with marine manufacturers. Based on this information, we estimate that 97
percent of new marine engines are turbocharged, and 80% of these turbocharged engines use
aftercooling. The majority of these engines are four-strokes, but about 14% of new engines are
two-strokes. Electronic controls have only recently been introduced into the marketplace;
however, we anticipate that their use will increase as customers realize the performance benefits
associated with electronic controls and as the natural migration of technology from on-highway
to nonroad to marine occurs.
Table 4.1-1 presents data1'2'3'4'5'6 from 25 recreational marine diesel engines based on the
ISO E5 duty cycle. This data shows to what extent emissions need to be reduced from today's CI
recreational marine engines to meet the proposed standards.1" On average, we are requiring
significant reductions in HC+NOx and PM. However, this data seems to show that the diesel
engine designs will either have to be focused on NOx or PM due to the trade-off between
calibrating to minimize these pollutants. The proposed CO standards will just act as a cap.
k For most of the engines in Table 4.1-1, the proposed standards are of 7.2 g/kW-hr
HC+NOx, 5 g/kW-hr CO, and 0.2 g/kW-hr PM
4-1
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Draft Regulatory Support Document
Table 4.1-1: Emissions Data from CI Recreational Marine Engines
Rated
Power (kW)
120
132
142
162
164
170
186
209
230
235
265
276
287
321
324
336
336
447
447
474
537
820
1040
1080
1340
Control Management
electronic
mechanical
mechanical
mechanical
electronic
mechanical
mechanical
mechanical
electronic
mechanical
mechanical
mechanical
electronic
mechanical
mechanical
electronic
electronic
electronic
mechanical
electronic
electronic
electronic
electronic
electronic
electronic
Aftercooling
raw-water
raw-water
separate circuit
raw-water
raw-water
raw-water
raw-water
raw-water
raw-water
raw-water
jacket-water
raw-water
raw-water
raw-water
jacket-water
jacket-water
jacket-water
raw-water
jacket-water
raw-water
jacket-water
separate circuit
jacket-water
separate circuit
separate circuit
Emissions Data g/kW-hr
HC NOx CO PM
0.09 5.8 0.9
0.07 4.2 0.2
0.79 8.6 1.1
0.11 4.0 0.2
0.28 5.1 1.6
0.36 8.1 0.6 0.20
0.30 10.2 1.2 0.12
0.42 10.8 2.3 0.22
0.28 5.5 1.8 0.39
0.45 9.8 1.8 0.20
0.58 10.8 1.4
0.60 10.7 1.9 0.24
0.28 7.9 - 0.12
0.37 7.7 0.9 0.23
0.30 7.9 2.9 0.95
0.18 11.0 0.5 0.10
0.09 11.9 - 0.16
0.12 9.3 - 0.17
0.60 12.0 1.5 0.18
0.34 7.7 0.5 0.07
0.08 10.7 - 0.19
0.33 9.5 0.8 0.13
0.09 9.3 - 0.21
0.18 7.6 1.2 0.15
0.27 7.2 0.9 0.15
4-2
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Chapter 4: Feasibility of Proposed Standards
4.1.2 Anticipated Technology for CI Recreational Marine Engines
Marine engines are generally derived from land-based nonroad, locomotive, and to some
extent highway engines. In addition, recreational marine engines will be able to use technology
developed for commercial marine engines. This allows recreational marine engines, which
generally have lower sales volumes than other nonroad engines, to be produced more cost-
effectively. Because the marine designs are derived from land-based engines, we believe that
many of the emission-control technologies which are likely to be applied to nonroad engines to
meet their Tier 2 and 3 emission standards will be applicable to marine engines. We also believe
that the technologies listed below will be sufficient for meeting both the new emission standards
and the Not to Exceed requirements discussed later in this chapter.
We anticipate that timing retard will likely be used in most CI recreational marine
applications, especially at cruising speeds, to gain NOx reductions. The negative impacts of
timing retard on HC, PM and fuel consumption can be offset with advanced fuel injection
systems with higher fuel injection pressures, optimized nozzle geometry, and potentially through
rate shaping. We do not expect marine engine manufacturers to convert from direct injection to
indirect injection due to these standards.
Regardless of environmental regulations, we believe that recreational marine engine
manufacturers would make more use of electronic engine management controls in the future to
satisfy customer demands of increased power and fuel economy. Through the use of electronic
controls, additional reductions in HC, CO, NOx, and PM can be achieved. Electronics may be
used to optimize engine calibrations under a wider range of operation. Most of the significant
research and development for the improved fuel injection and engine management systems
should be accomplished for land-based nonroad diesel engines which are being designed to meet
Tier 2 and Tier 3 standards. Common rail should prove to be a useful technology for meeting
even lower emission levels in the future, especially for smaller engines. Thus, the challenge for
this control program will be transferring land-based techniques to marine engines.
We project that all CI recreational marine engines will be turbocharged and most will be
aftercooled to meet proposed emission standards. Aftercooling strategies will likely be mostly
jacket-water charge air cooling, and in some cases, we believe that separate cooling circuits for
the aftercooling will be used. We do not expect a significant increase in the use of raw-water
charge air cooling for marine engines as a result of this proposed rule. We recognize that raw-
water aftercooling systems are currently in use in many applications. Chapter 4 presents one
possible scenario of how these technologies could be used on Category 1 marine diesel engines
to meet the proposed standards.
By proposing standards that will not go into effect until 2006, we are providing engine
manufacturers with substantial lead time for developing, testing, and implementing emission
control technologies. This lead time and the coordination of standards with those for commercial
marine engines allows for a comprehensive program to integrate the most effective emission
control approaches into the manufacturers' overall design goals related to performance,
4-3
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Draft Regulatory Support Document
durability, reliability, and fuel consumption.
4.1.3 Emission Measurement Procedures for CI Recreational Marine Engines
In any program we design to achieve emissions reductions from internal combustion
engines, the test procedures we use to measure emissions are as important as the standards we put
into place. These test procedure issues include duty cycle for certification, in-use verification
testing, emission sampling methods, and test fuels.
4.1.3.1 Certification Duty Cycles
In choosing duty cycles for certification, we turned to the International Standards
Organization (ISO).7 For CI recreational marine engines, we based our standards on the ISO E5
duty cycle. This duty cycle is intended for "diesel engines for craft less than 24m length
(propeller law)."
We are proposing to use the E5 duty cycle to measure emissions from diesel recreational
marine engines. This cycle is similar to the E3 duty cycle which is used for commercial marine
in that both cycles have four steady-state test points on an assumed cubic propeller curve.
However, the E5 includes an extra mode at idle and has an average weighted power of 34%
compared to the 69% for the E3. This duty cycle is presented in Table 4.1-2.
Table 4.1-2: ISO E5 Marine Duty Cycle
Mode
I
2
3
4
5
% of Rated Speed
100
91
80
63
idle
% of Power at Rated Speed
100
75
50
25
0
Weighting Factor
0.08
0.13
0.17
0.32
0.30
4.1.3.2 Emission Control of Typical In-Use Operation
We are concerned that if a marine engine is designed for low emissions on average over a
low number of discrete test points, it may not necessarily operate with low emissions in-use.
This is due to a range of speed and load combinations that can occur on a boat which do not
necessarily lie on the test duty cycles. For instance, the test modes for the E5 duty cycle lie on
average propeller curves. However, a propulsion marine engine may never be fitted with an
"average propeller." In addition, a given engine on a boat may operate at higher torques than
average if the boat is heavily loaded. We are also aware that, before a boat comes to plane, the
4-4
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Chapter 4: Feasibility of Proposed Standards
engine operates closer to its full torque map than to the propeller curve.
We propose to apply the "not-to-exceed" (NTE) limit concept to recreational marine
engines similar to commercial marine engines. This concept basically picks a zone of operation
under which a marine engine must not exceed the standard by a fixed percentage and is discussed
in more detail in the commercial marine FRM. Of course, the shape of the zone must be adjusted
to reflect recreational engine use.
Under this proposal, we would have the authority to use test data from new or in-use
engines to confirm emissions compliance. The engines tested would have to be within their
regulatory useful lives.
4.1.3.2.1 Engine operation included for NTE
The shape of the NTE zones are based on our understanding of how recreational marine
engines are used. Operation at low power is omitted from the NTE zone even though marine
engines operate here in use. This omission is because, by definition, brake-specific emissions
become very large at low power due to dividing by power values approaching zero.
We believe that the majority of marine engine operation is steady-state. This is why we
are proposing that only steady-state operation be considered in the NTE requirements. Also, this
is a technology forcing proposal and we would expect to see reductions even under transient
operation. If we were to find that the effectiveness of this program is hurt due to high emissions
under transient operation, we would revisit this issue in the future.
It should be noted that the emissions caps for operation in the NTE zone would be based
on the weighted emissions over the E5 duty cycle. Because idle emissions are part of these
weighted values but not included in the NTE zone, it is likely that emissions in the NTE zone
will be less than the weighted average. This alone reduces the stringency of a "not-to-exceed"
approach for recreational when compared to commercial marine engines.
For compression-ignition engines, the NTE zone is defined by the maximum power
curve, actual propeller curves, and speed and load limits. The E5 duty cycle itself is based on a
cubic power curve through the peak power point. For the NTE zone, we propose to define the
upper boundary using a speed squared propeller curve passing through the 115% load point at
rated speed and the lower boundary using on a speed to the fourth power curve passing through
the 85% load point at rated speed. We believe these propeller curves represent the range of
propeller curves seen in use.8 To prevent imposing an unrealistic cap on a brake-specific basis,
we are proposing to limit this region to power at or above 25% of rated power and speeds at or
above 63% of rated speed. These limits are consistent with mode 4 of the E5 duty cycle. Figure
4.1-1 presents the proposed NTE zone for CI recreational marine engines.
4-5
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Draft Regulatory Support Document
Figure 4.1-1: Proposed NTE Zone for Recreational CI Marine Engines
100%
90%
,_ 80%
0)
I 70%
0 60%
'I 50% H
" 40%
30% -
20%
10%
1.5xFEL
1.2xFEL
45% power.
25% power
50% 60%
70% 80% 90%
engine speed
100%
We understand that an engine tested onboard a boat in use may not be operating as the
manufacturer intended. Specifically, the owner may not be using a propeller that is properly
matched to the engine and boat. Or, the owner may have a boat that is overloaded and too heavy
for the engine. The boundaries in Figure 4.1-1 are intended to contain typical operation of
recreational diesel engines and exclude engines which are not used properly. Although the E5
uses a cubic power curve engines generally see some variation in use. These boundaries are
consistent with operational data we collected.9
We are proposing emissions caps for the NTE zone which represent a multiplier times the
weighted test result used for certification. Although ideally the engine should meet the
certification level throughout the NTE zone, we understand that a cap of 1.0 times the standard is
not reasonable, because there is inevitably some variation in emissions over the range of engine
operation. This is consistent with the concept of a weighted modal emission test such as the
steady-state tests included in this rule.
Consistent with the commercial requirements, we propose that recreational CI marine
engines must meet a cap of 1.5 times the certified level for HC+NOx, PM, and CO for the speed
and power subzone below 45% of rated power and a cap of 1.2 times the certified levels at or
4-6
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Chapter 4: Feasibility of Proposed Standards
above 45% of rated power. However, we are proposing an additional subzone, when compared
to the commercial NTE zone, at speeds greater than 95% of rated. We are proposing a cap of 1.5
times the certified levels for this subzone. Our purpose for this additional subzone is to address
the typical recreational design for higher rated power. This power is needed to ensure that the
engine can bring the boat to plane.
We based the proposed caps both on emissions data collected on the assumed propeller
curve and on data collected from a recreational marine diesel engine over a wide range of steady-
state operation. All of this data is cited earlier in this chapter. The data in Figure 4.1-2 shows
that, within the range of in-use testing points, HC+NOx and PM are generally well below the E5
weighted averages. This is likely due to the effects of emissions at idle. For all of these engines,
modal CO results were well below the proposed standard. None of these engines are calibrated
for emissions control.
4-7
-------
Draft
odai Emissions to E5 Cycle Weighted Emissions for Marine Diesel Engines
1.5
X
O
modal to E5 average HC+h
o
01 -&
o
o
ro
0
HC+NOx: Modal/E5 Average
r-.
I
1
1
E
1
1
-
=
i
i
E
1
1
63% spd 80% spd 91% spd 100% spd
HC+NOx: Modal/E5 Average
recreational marine diesel engine
i_
0
1
Q.
T3
0
2
1
0
Q.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
50
1.45
0.71
•ZU0.63 ^
*• 0.49
u-4b°^° 0.75
,, or 1 .p4^ *
X 0.58
0.59
X ff'85
1.49
1.26 1.23>
1.
0.65 0.68/
n cc- ^
S 0.66
BT61
1.02
90%
80%
of rated speed
^a .p i
09/
1.88
21
.24
100%
PM: Modal/E5 Average
63% spd
80% spd
91% spd
100% spd
4-8
PM: Modal/E5 Average
recreational marine diesel engine
0
I
Q.
T3
0
0
y
0
Q.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0.34
O.b7
~€
i
"
1 30j,*03i.f^
Q640.93 I.JU r
. - 0.82/
V 0.65 0.77' 1.04
0-64xa66000 . '-"5
:::'_, . .. X 1.65
: 1.65 1.21?T30 1-36
0.79 ^-900.93
, 0.:67 0.80
50%
70%
90%
60% 80% 100%
percent of rated speed
-------
Chapter 4: Feasibility of Proposed Standards
4.1.3.2.2 Ambient conditions during testing
Variations in ambient conditions can affect emissions from a marine engine. Such
conditions include air temperature, humidity, and (especially for diesels) water temperature. We
are proposing to apply the commercial marine engine ranges for these variables. Within the
ranges, no corrections can be made for emissions. Outside of the ranges, emissions can be
corrected back to the nearest edge of the range. The proposed ambient variable ranges are:
intake air temperature 13-35 °C (55-95 °F)
intake air humidity 7.1-10.7 g water/kg dry air (50-75 grains/lb. dry air)
ambient water temperature 5-27°C (41-80°F)
The proposed air temperature and humidity ranges are consistent with those developed for
NTE testing of highway heavy-duty diesel engines. The air temperature ranges were based on
temperatures seen during ozone exceedences.10 For NTE testing in which the air temperature or
humidity is outside of the range, we propose that the emissions be corrected back to the air
temperature or humidity range. These corrections would have to be consistent with the equations
in Title 40 of the Code of Federal Regulations except that these equations correct to 25 °C and
10.7 grams per kilogram of dry air while corrections associated with the NTE testing shall be to
the nearest outside edge of the specified ranges. For instance, if the temperature were higher than
35°C, a temperature correction factor may be applied to the emissions results to determine what
the emissions would be at 35°C.
For marine engines using aftercooling, we believe the charge air temperature is
insensitive to ambient air temperature compared to the cooling effect of the aftercooler. SwRI
tested this theory and found that when the ambient air temperature was increased from 21.9 to
32.2°C, the cooling water to the aftercooler of a diesel marine engine only had to be reduced by
0.5°C to maintain a constant charge air temperature.11 According to the CFR correction factor,
there is only a ±3% variation in NOx in the proposed NTE humidity range.
Some CI recreational marine engines, are naturally aspirated. Naturally aspirated engines
should be more sensitive to intake air temperature because the temperature affects the density of
the air into the engine. Therefore, high temperatures can limit the amount of air drawn into the
cylinder. However, our understanding is that many engines operate in and draw air from small
engine compartments. This suggests that most recreational engines are already designed to
operate with high intake air temperatures.
Ambient water temperature also may affect emissions due to its impact on engine and
charge air cooling. We believe that this effect is small for naturally aspirated engines. We based
the proposed water temperature range on temperatures that marine engines experience in the U.S.
in use. Although marine engines experience water temperatures near freezing, we don't believe
that additional emission control will be gained by lowering the minimum water temperature
below 5 °C. At this time, we aren't aware of an established correction factor for ambient water
temperature. For this reason, we propose that NTE zone testing must be within the specified
4-9
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Draft Regulatory Support Document
ambient water temperature range.
We don't think that the range of ambient water temperatures discussed above will have a
significant effect on the stringency of the NTE requirements, even for aftercooled engines.
Following the normal engine test practice recommended by SAE12 for aftercooled engines, the
cooling water temperature would be set to 25±5 °C. This upper portion of the NTE temperature
range is within the range suggested by SAE for engine testing. For lower temperatures,
manufacturers would be able to use a thermostat or other temperature regulating device to ensure
that the charge air is not overcooled. In addition, the SAE practice presents data from four
aftercooled diesel engines on the effects of cooling medium temperature on emissions. For every
5°C increase in temperature, HC decreases 1.8%, NOx increases 0.6%, and PM increases 0.1%.
We are aware that many marine engines are designed for operation in a given climate.
For instance, recreational vessels operated in Seattle don't need to be designed for 27°C water
temperatures. For situations such as this, we propose that manufacturers be allowed to petition
for the appropriate temperature ranges associated with the NTE zone for a specific engine design.
In addition, we understand there are times when emission control needs to be compromised for
startability or safety. Manufacturers would not be responsible for the NTE requirements under
start up conditions. In addition, we propose that manufacturers would be able to petition to be
exempt from emission control under specified extreme conditions such as engine overheating
where emissions may increase under the engine protection strategy.
4.1.3.3 Emissions Sampling
Aside from the duty cycle, the test procedures for marine engines are similar to those for
land-based nonroad engines. However, there are a few other aspects of marine engine testing
that need to be considered. Most recreational marine engines mix cooling water into the exhaust.
This exhaust cooling is generally done to keep surface temperatures low for safety reasons and to
tune the exhaust for performance and noise. Because the exhaust must be dry for dilute emission
sampling, the cooling water must be routed away from the exhaust in a test engine.
Even though many marine engines exhaust their emissions directly into the water, we
base our proposed test procedures and associated standards on the emissions levels in the "dry"
exhaust. Relatively little is known about water scrubbing of emissions. We must therefore
consider all pollutants out of the engine to be a risk to public health. Additionally, we are not
aware of a repeatable laboratory test procedure for measuring "wet" emissions. This sort of
testing is nearly impossible from a vessel in-use. Finally, a large share of the emissions from this
category come from large engines which emit their exhaust directly to the atmosphere.
The established method for sampling emissions is through the use of full dilution
sampling. However, for larger engines the exhaust flows become so large that conventional
dilute testing requires a very large and costly dilution tunnel. One option for these engines is to
use a partial dilute sampling method in which only a portion of the exhaust is sampled. It is
important that the partial sample be representative of the total exhaust flow. The total flow of
4-10
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Chapter 4: Feasibility of Proposed Standards
exhaust can be determined by measuring fuel flow and balancing the carbon atoms in and out of
the engine. For guidance on shipboard testing, the MARPOL NOx Technical Code specifies
analytical instruments, test procedures, and data reduction techniques for performing test-bed and
in-use emission measurements.13 Partial dilution sampling methods can provide accurate steady-
state measurements and show great promise for measuring transient emissions in the near future.
We intend to pursue development of this method and put it in place prior to the date that the
standards in this final rule become enforceable.
Pulling a marine engine from a boat and bringing it to a laboratory for testing could be
burdensome. For this reason, we propose to be able to perform in-use confirmatory testing
onboard a boat. Our goal would be to perform the same sort of testing as proposed for the
laboratory. However, engines tested in a boat are not likely to operate exactly on the assumed
propeller curve. For this reason, we propose that emissions measured within the NTE zone must
meet the subzone caps based on the certified level during onboard testing. To facilitate onboard
testing, our proposal requires that manufacturers provide a location with a threaded tap where a
sampling probe may be inserted. This location would have to be upstream of where the water
and exhaust mix at a location where the exhaust gases could be expected to be the most
homogeneous.
There are several portable sampling systems on the market that, if used carefully, can give
fairly accurate results for onboard testing. Engine speed can be monitored directly, but load may
have to be determined indirectly. For engines operating at a constant speed, it should be
relatively easy to set the engine to the points specified in the duty cycles.
4.1.3.4 Test Fuel Specifications
We propose to apply the recently finalized test fuel specifications for commercial marine
engines to recreational marine diesel engines. These fuel specifications are similar to land-based
nonroad fuel with a change in the sulfur content upper limit from 0.4 to 0.8 weight-percent
(wt%). We believe that this will simplify development and certification burdens for marine
engines that are developed from land-based counterparts. This test fuel has a sulfur specification
range of 0.03 to 0.80 wt%, which covers the range of sulfur levels observed for most in-use fuels.
Manufacturers will be able to test using any fuel within this range for the purposes of
certification. Thus, they will be able to harmonize their marine test fuel with U.S. highway
(<0.05 wt%) and nonroad (0.03 to 0.40 wt%), and European testing (0.1 to 0.2 wt%).
The intent of these proposed test fuel specifications is to ensure that engine manufacturers
design their engines for the full range of typical fuels used by Category 1 marine engines in use.
Because the technological feasibility of the new emission standards is based on fuel with up to
0.4 wt% sulfur, any testing done using fuel with a sulfur content above 0.4 wt% would be done
with an allowance to adjust the measured PM emissions to the level they would be if the fuel
used were 0.4 wt% sulfur. The full range of test fuel specifications are presented in Table 4.1-3.
Because testing conducted by us is limited to the test fuel specifications, it is important that the
test fuel be representative of in-use fuels.
4-11
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Draft Regulatory Support Document
Table 4.1-3: Recreational Marine Diesel Test Fuel Specifications
Item
Cetane
Initial Boiling Point, °C
10% point, °C
50% point, °C
90% point, °C
End Point, °C
Gravity, API
Total Sulfur, % mass
Aromatics, % volume
Parafins, Napthenes, Olefins
Flashpoint, °C
Viscosity @ 38 °C, centistokes
Procedure (ASTM)
D613-86
D86-90
D86-90
D86-90
D86-90
D86-90
D287-92
D 129-21 orD2622-92
D1319-89orD5186-91
D1319-89
D93-90
D445-88
Value (Type 2-D)
40-48
171-204
204-238
243-282
293-332
321-366
32-37
0.03-0.80
10 minimum
remainder
54 minimum
2.0-3.2
4.1.4 Impacts on Noise, Energy, and Safety
The Clean Air Act requires EPA to consider potential impacts on noise, energy, and
safety when establishing the feasibility of emission standards for CI recreational marine engines.
One important source of noise in diesel combustion is the sound associated with the
combustion event itself. When a premixed charge of fuel and air ignites, the very rapid
combustion leads to a sharp increase in pressure, which is easily heard and recognized as the
characteristic sound of a diesel engine. The conditions that lead to high noise levels also cause
high levels of NOx formation. Fuel injection changes and other NOx control strategies therefore
typically reduce engine noise, sometimes dramatically.
The impact of the new emission standards on energy is measured by the effect on fuel
consumption from complying engines. Many of the marine engine manufacturers are expected to
retard engine timing which increases fuel consumption somewhat. Most of the technology
changes anticipated in response to the new standards, however, have the potential to reduce fuel
consumption as well as emissions. Redesigning combustion chambers, incorporating improved
fuel injection systems, and introducing electronic controls provide the engine designer with
powerful tools for improving fuel efficiency while simultaneously controlling emission
formation. To the extent that manufacturers add aftercooling to non aftercooled engines and shift
4-12
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Chapter 4: Feasibility of Proposed Standards
from jacket-water aftercooling to raw-water aftercooling, there will be a marked improvement in
fuel-efficiency. Manufacturers of highway diesel engines have been able to steadily improve fuel
efficiency even as new emission standards required significantly reduced emissions.
There are no apparent safety issues associated with the new emission standards. Marine
engine manufacturers will likely use only proven technology that is currently used in other
engines such as nonroad land-based diesel applications, locomotives, and diesel trucks.
4-13
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Draft Regulatory Support Document
4.2 Large Industrial SI Engines
This category of engines generally includes all nonrecreational land-based spark-ignition
engines rated above 19 kW that are not installed in motor vehicles or stationary applications. In
an earlier memorandum, we described the rationale for developing emission measurement
procedures for transient and off-cycle engine operation.14 Information from that memorandum is
not repeated here, except to the extent that it supports decisions about the selecting the proposed
numerical emission standards.
The proposed emission standards for Large SI engines are listed in the Executive
Summary. The following paragraphs summarize the data and rationale supporting the proposed
standards.
4.2.1 Proposed 2004 Standards
Engine manufacturers are currently developing technologies and calibrations to meet the
2004 standards that apply in California. We expect manufacturers to rely on electronically
controlled, closed-loop fuel systems and three-way catalysts to meet those emission standards.
As described below, emission data show that water-cooled engines can readily meet the
California ARE standards (3 g/hp-hr NMHC+NOx; 37 g/hp-hr CO).
Our projected date for a final rule—September 2002—allows manufacturers just over one
year to prepare engines for nationwide sales starting in 2004. Implementing new standards with
such a short lead time is only possible because manufacturers have been aware of their need to
comply with the California ARB standards. With no need to further modify engine designs,
manufacturers should have time before 2004 to plan for increasing production volume for
nationwide sale of engines that can meet the 2004 California ARB standards.
Adopting standards starting in 2004 allows us to align near-term requirements with those
adopted by California ARB. This also provides early emission reductions and gives
manufacturers the opportunity to amortize their costs over a broader sales volume before
investing in the changes needed to address the long-term standards described below.
4.2.2 Proposed 2007 Standards
The proposed 2004 standards described above would be effective in reducing emissions
from Large SI engines, but we believe these levels don't fulfill our obligation to adopt standards
achieving the "greatest degree of reduction achievable" from these engines in the long term.
With additional time to optimize designs to better control emissions, manufacturers can optimize
their designs to reduce emissions below the levels required by the proposed 2004 standards. We
are also proposing new procedures for measuring emissions starting in 2007, which would
require further efforts to more carefully design and calibrate emission-control systems to achieve
in-use emission reductions. The following discussion explains why we believe the proposed
2007 emission standards are feasible.
4-14
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Chapter 4: Feasibility of Proposed Standards
The biggest uncertainty in adopting emission standards for Large SI engines has been the
degree to which emission-control systems deteriorate with age. While three-way catalysts and
closed-loop fueling systems have been in place in highway applications for almost 20 years, there
is very little information showing how these systems hold up under nonroad use. To address this,
we participated in an investigative effort with Southwest Research Institute (SwRI), California
ARE, and South Coast Air Quality Management District, as described in the memorandum
referenced above. The engines selected for testing had been retrofitted with emission-control
systems in Spring 1997 after having already run for 5,000 and 12,000 hours. Both engines are in-
line four-cylinder models operating on liquefied petroleum gas (LPG)—a 2-liter Mazda engine
rated at 32 hp and a 3-liter GM engine rated at 45 hp. The retrofit consisted of a new,
conventional three-way catalyst, electronic controls to work with the existing fuel system, and the
associated sensors, wiring, and other hardware. The electronic controller allowed only a single
adjustment for controlling air-fuel ratios across the range of speed-load combinations.
Laboratory testing consisted of measuring steady-state and transient emission levels, both
before and after taking steps to optimize the system for low emissions. While the engines'
emission-control systems originally focused on controlling CO emissions, the testing effort
focused on simultaneously reducing HC, NOx, and CO emissions. This testing provides a good
indication of the capability of these systems to control emissions over an engine's full useful life.
The testing also shows the degree to which transient emissions are higher than steady-state
emission levels for Large SI engine operation. Finally, the testing shows how emission levels
vary for different engine operating modes. Emission testing included engine operation at a wide
range of steady-state operating points and further engine operation over several different transient
duty cycles. Much of the emissions variability at different speeds and loads can be attributed to
the basic design of the controller, which has a single, global calibration setting. This data
showing the variability of emissions is necessary to support the proposed field-testing emission
standards, as described further below.
4.2.2.1. Steady-state testing results
Testing results from the aged engines at SwRI showed very good emission control
capability over the full useful life. Test results with new hardware on the aged engines lead to
the conclusion that the systems operated with relatively stable emission levels over the several
thousand hours. As shown in Table 4.2-1, the emission levels measured by SwRI are consistent
with results from a wide variety of measurements on other engines. The data listed in the table
includes only LPG-fueled engines. See Section 4.2.2.6 a discussion of gasoline-fueled engines.
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Table 4.2-1
Steady-State Emission Results from LPG-fueled Engines
Test engine
Mazda 2L15
GM3L
Engine B
GFI16
Toyota/ECS 2L17
GM/Impco 3L18
HC+NOx*
g/hp-hr
0.51
0.87
0.22
0.52
NMHC+NOx
1.14
0.26
CO
g/hp-hr
3.25
1.84
2.79
2.23
0.78
0.21
Notes**
4,000 hours, add-on retrofit
5,600 hours, add-on retrofit
250 hours
5,000 hours
zero-hour; ISO Cl duty cycle
for nonroad diesel engines
zero-hour
*Measurements are THC+NOx, unless otherwise noted.
"Emissions were measured on the ISO C2 duty cycle, unless otherwise noted.
This data set supports emission standards significantly more stringent than the proposed
2004 standards. However, considering the need to focus on transient emission measurements, we
believe it is not appropriate to adopt more stringent emission standards based on the steady-state
duty cycles. Stringent emission standards based on certain discrete modes of operation may
unnecessarily constrain manufacturers from controlling emissions across the whole range of
engine speeds and loads. We therefore intend to rely more heavily on the transient testing to
determine the stringency of the emission-control program.
4.2.2.2 Transient testing results
The SwRI testing is currently the only source of information available for evaluating the
transient emission levels from Large SI engines equipped with emission-control systems.
Table 4.2-2 shows the results of this testing. The transient emission levels, though considerably
lower than the 2004 standards, are higher than those measured on the steady-state duty cycles. A
combination of factors contribute to this. First, engines are unlikely to maintain precise control
of air-fuel ratios during rapid changes in speed or load, resulting in decreased catalyst-conversion
efficiency. Also, the transient duty cycle includes operation at engine speeds and loads that have
higher steady-state emission levels than the seven modes constituting the C2 duty cycle. Both of
these factors would also cause uncontrolled emission levels to be higher, so the measured
emission levels with the catalyst system still show a substantial reduction in emissions.
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Chapter 4: Feasibility of Proposed Standards
Table 4.2-2
Transient Test Results from SwRI Testing
Engine*
Mazda
GM
Duty Cycle
Variable-speed, variable-load
Constant-speed, variable-load
Variable-speed, variable-load
THC+NOx
g/hp-hr
1.1
1.5
1.2
CO
g/hp-hr
9.9
8.4
7.0
*Based on the best calibration on the engine operating with an aged catalyst.
4.2.2.3 Off-cycle testing results
Engines operate in the field under both steady-state and transient operation. Although
these emission levels are related to some degree, they are measured separately. This section
therefore first considers steady-state operation.
Figures 4.2-1 through 4.2-6 show plots of emission levels from the test engines at several
different steady-state operating modes. This includes the seven speed-load points in the ISO C2
duty cycle, with many additional test points spread across the engine map to show how emissions
vary with engine operation. The plotted emission level shows the emissions at each normalized
speed and normalized load point. The 100-percent load points at varying engine speeds form the
engine's lug curve, which appears as a straight line because of the normalizing step.
Figure 4.2-1 shows the THC+NOx emissions from the Mazda engine when tested with
the aged catalyst. While several points are higher than the 0.51 g/hp-hr level measured on the C2
duty cycle, the highest levels observed from the Mazda engine are around 2.3 g/hp-hr. The
highest emissions are generally found at low engine speeds. Emission testing on the Mazda
engine with a new catalyst showed very similar results, so they are not shown here.
CO emissions from the same engine had a similar mix of very low emission points and
several higher measurements. The CO levels along the engine's lug curve (100 percent load)
range 12 to 22 g/hp-hr, well above the other points, most of which are under 4 g/hp-hr. The
corner of the map with high-speed and low-load operation also has a high level of 9 g/hp-hr.
These high-emission modes point to the need to address control of air-fuel ratios at these
extremes of engine operation.
If CO emissions at these points would be an inherent problem associated with these
engines, we could take that into account in setting the standard. Figure 4.2-4 shows, however,
that the GM engine with the same kind of aged emission-control system had emission levels at
most of these points ranging from 0.7 to 4.7 g/hp-hr. The one remaining high point on the GM
engine was 11.6 g/hp-hr at full load and low speed. A new high-emission point was 28 g/hp-hr at
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Draft Regulatory Support Document
the lowest measured speed and load. Both of these points are much lower on the same engine
with the new catalyst installed (see Figure 4.2-6). These data reinforce the conclusion that
adequate development effort will enable manufacturers to achieve broad control of emissions
across the engine map.
Figure 4.2-3 shows the THC+NOx emissions from the GM engine when tested with the
aged catalyst. Emission trends across the engine map are similar to those from the Mazda
engine, with somewhat higher low-speed emission levels between 2.3 and 4.4 g/hp-hr at various
points. Operation on the new catalyst shows a significant shifting of high and low emission
levels at low-speed operation, but the general observation is that the highest emission levels
disappear, with 2.3 g/hp-hr being again the highest observed emission level over the engine map
(see Figure 4.2-5).
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Chapter 4: Feasibility of Proposed Standards
Figure 4.2-1
Mazda/old cat.--NOx+HC
100 189
80 1'19
1.61
1 6° 1.92
_l
40 2.08
20 2'28
1.43
10 20
C2 = 0.51 g/hp-hr
0.6
0.46
0.95
0.87
1.11
1.67
2.26
30 40
g/hp-hr
0.77
0.53
0.41
0.35
0.33
0.14
1.24
50 60 70
Speed
0.57
0.31
0.31
0.5
0.62
0.72
0.28
80 90
0.25
0.27
0.25
0.43
0.63
0.81
0.54
100 110
Figure 4.2-2
Mazda/old cat--CO
100 2224
80 1'07
0.23
03 60 „ QQ
O 0.33
_l
40 0.64
20 °'51
1.3
10 20
C2=3.25 g/hp-hr
11.52
2.28
1.27
0.88
0.56
0.04
0.19
30 40
g/hp-hr
15.24
8.07
4.06
2.44
0.91
0.79
0
50 60 70
Speed
18.98
4.17
3.01
3.87
3.61
2.89
1.61
80 90
2.49
3.87
3.88
3.9
4.47
7.6
9.08
100 110
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Draft Regulatory Support Document
Figure 4.2-3
GM/old cat.--NOx+HC
100 3.5
80 16
1.6
as 60 , c
O 1.D
_l
40 2.3
20 23
4.4
10 20
C2=0.87 ghp-hr
1.3
1.2
1.1
1.2
0.9
0.6
1.6
30 40
g/hp-hr
0.8
0.7
1.2
0.9
0.7
0.5
1.1
50 60 70
Speed
0.8
0.7
0.6
0.6
0.7
0.5
0.7
80
0.9
0.9
0.6
0.5
0.4
0.7
0.4
90 100 110
Figure 4.2-4
GM/old cat.--CO
100 11.6 0.7
39 21
80
4.3 2.4
ro 60 . , „ ,
o 4.1 3.5
40 6.0 3.6
20 3.5 3.9
28.0 5.1
10 20 30 40
C2=1. 84 ghp-hr
g/hp-hr
4.7
0.6
1.7
1.6
2.1
1.1
1.4
50 60 70
Speed
4.5
0.7
0.6
0.8
0.3
2.8
10.3
80
0.7
0.7
1.3
1.8
1.4
6.2
4.3
90 100 110
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Chapter 4: Feasibility of Proposed Standards
Figure 4.2-5
GM/new cat.-NOx+HC
100 0.57 0.92
80 2'25 °'75
2.25 0.82
1 6° 1.93 0.79
_l
40 1.61 0.83
2Q 1.33 0.66
1.47 1.17
10 20 30 40
C2=0.35 ghp-hr
g/hp-hr
0.32
0.28
0.19
0.25
0.30
0.13
0.25
50 60 70
Speed
0.26 0.14
0.18 0.11
0.19 0.08
0.20 0.05
0.06 0.04
0.13 0.08
0.65 0.16
80 90 100 110
Figure 4.2-6
GM/new cat.
100 4.08
80 °'55
0.33
03 60 „ QQ
o 0.33
_i
40 0.24
20 °'11
0.45
10 20
C2=0.28 ghp-hr
0.16
1.03
0.92
0.70
0.72
1.04
0.44
30 40
g/hp-hr
2.65
0.81
0.37
0.00
0.93
0.29
0.73
--CO
1.78
0.23
0.47
0.65
0.10
0.23
6.70
50 60 70 80
Speed
0.06
1.15
0.44
0.21
0.12
0.28
0.26
90 100 110
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Draft Regulatory Support Document
Field testing will typically also include transient emission measurement. We are
proposing that a field-testing measurement may include any segment of normal operation with a
two-minute minimum sampling period. This would not include engine starting, extended idling,
or other cold-engine operation. Table 4.2-3 shows a wide variety of transient emission levels
from the two test engines. While the engines were tested in the laboratory, the results show
emissions would vary under normal operation when installed in nonroad equipment. These
segments could be considered as valid field-testing measurements to show that an engine meets
emission standards in the field when tested in nonroad equipment in which the engines are
installed. Several segments included in the table were run with a hot start, which could
significantly increase emission levels, depending on how long the engine runs in open loop after
starting. This is especially important for CO emissions. Even with varied strategies for soaking
and warming up engines, emission levels are generally between 1 and 2 g/hp-hr THC+NOx and
between 4 and 13 g/hp-hr CO. Emission levels don't seem to vary dramatically between cycle
segments, even where engine operation is significantly different.
Table 4.2-3
Transient Emission Measurements from SwRI Testing
Engine
Mazda
GM
Test Segment
"typical" forklift (5 min.)
"high-transient" forklift (5 min.)
highway certification test
backhoe/loader cycle
"typical" forklift (5 min.)
"high-transient" forklift (5 min.)
highway certification test
backhoe/loader cycle
THC+NOx
g/hp-hr
2.0
1.3
1.2
1.3
1.3
2.0
1.0
1.0
CO,
g/hp-hr
5.7
4.3
4.6
9.1
9.5
12.6
4.4
3.8
Notes
hot start
hot start
hot start
20-minute soak before test
hot start
hot start
3-minute warm-up; 2-minute soak
3-minute warm-up; 2-minute soak
4.2.2.4 Ambient conditions
While certification testing involves engine operation in a controlled environment, engines
operate in conditions of widely varying temperature, pressure, and humidity. To take this into
account, we are proposing to broaden the range of acceptable ambient conditions for field-testing
measurements. We are proposing to limit field-testing emission measurements to ambient
temperatures from 13° to 35° C (55° to 95° F), and to ambient pressures from 600 to 775
millimeters of mercury (which should cover almost all normal pressures from sea level to 7,000
feet above sea level). Tests would be considered valid regardless of humidity levels. This allows
testing under a wider range of conditions in addition to helping ensure that engines are able to
control emissions under the whole range of conditions under which they operate.
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Chapter 4: Feasibility of Proposed Standards
The SwRI test data published here are based on testing under laboratory conditions
typical for the test location. Ambient temperatures ranged from 70 to 86° F. Barometric
pressures were in a narrow range around 730 mm Hg. Humidity levels ranged from about 4 to 14
g of water per kg dry air, but all emission levels were corrected to a reference condition of
10.7 g/kg. Most testing occurred at humidity levels above 10.7, in which case actual NOx
emission levels were up to 7 percent lower than reported by SwRI. In the driest conditions,
measured NOx emission levels were up to 10 percent higher than reported. The proposed field-
testing standards take into account the possibility of a humidity effect of increasing NOx
emissions. We are not aware of any reasons that varying ambient temperatures or pressures
would have an inherent effect on emission levels from spark-ignition engines.
4.2.2.5 Durability of Emission-Control Systems
SwRI tested engines that had already operated for the full proposed useful life period with
functioning emission-control systems. Before being retrofitted with catalysts and electronic fuel
systems, these engines had already operated for 5,000 and 12,000 hours, respectively. The tested
systems therefore provide very helpful information to show the capability of the anticipated
emission-control technologies to function over a lifetime of normal in-use operation.
The testing effort required selection, testing, and re-calibration of installed emission-
control systems that were not designed specifically to meet emission standards. These systems
were therefore not necessarily designed for simultaneously controlling NOx, HC, and CO
emissions, for lasting 5,000 hours or longer, or for performing effectively under all conditions
and all types of operation that may occur. The testing effort therefore included a variety of
judgments, and adjustments to evaluate the emission-control capability of the installed hardware.
This effort highlighted several lessons that should help manufacturers design and produce
durable systems.
Selecting engines from the field provided the first insights into the functionality of these
systems. Tailpipe ppm measurements showed that several engines had catalysts that were
inactive (or nearly inactive). These units were found to have loose catalyst material inside the
housing, which led to a significant loss of the working volume of the catalyst and exhaust flow
bypassing the catalyst material. Dimensional measurements showed that this resulted from a
straightforward production error of improperly assembling the catalyst inside the shell.19 This is
not an inherent problem with catalyst production and is easily addressed with automated or more
careful manual production processes. The catalyst from the GM engine selected for testing had
also lost some of its structural integrity. Almost 20 percent of the working volume of the catalyst
had disappeared. This catalyst was properly re-assembled with its reduced volume for further
testing. This experience underscores the need for effective quality-control procedures in
assembling catalysts.
Substituting a new catalyst on the aged system allowed emission measurements that help
us estimate how much the catalysts degraded over time. This assessment is rather approximate,
since we have no information about the zero-hour emissions performance of that exact catalyst.
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The new catalysts, which were produced about three years later under the same part numbers and
nominal characteristics, generally performed in a way that was consistent with the aged catalysts.
Not surprisingly, the catalyst with the reduced working volume showed a higher rate of
deterioration than the intact catalyst. Both units, however, showed very stable control of NOx
and HC emissions. CO deterioration rates were generally higher, but the degree of observed
deterioration was very dependent on the particular duty cycle and calibration for a given set of
emission measurements.
Measured emission levels from the aged catalysts shows what degree of conversion
efficiency is possible for each pollutant after several thousand hours of operation. The emission
data from the new catalysts suggest that manufacturers would probably need to target low enough
zero-hour CO emission levels to account for significant deterioration. The data also show that
catalyst size is an important factor in addressing full-life emission control. The nominal sizes of
the catalysts on the test engines were between 50 and 55 percent of total engine displacement.
The cost analysis in Chapter 5 is based on initial compliance with a catalyst sized at 60 percent of
total engine displacement. We would expect manufacturers to reduce catalyst size as much as
possible to reduce costs without risking the possibility of high in-use emissions.
Another important issue relates to degradation associated with fuel impurities, potential
lack of maintenance, and wear of oxygen sensors. Fuel system components in LPG systems are
prone to fuel deposits, primarily from condensation of heavy hydrocarbon constituents in the
fuel. The vaporizer and mixer on the test engines showed a typical degree of fuel deposits from
LPG operation. The vaporizer remained in the as-received condition for all emission
measurements throughout the test program. Emission tests before and after cleaning the mixer
give an indication of how much the deposits affect the ability of the closed-loop fueling system to
keep the engine at stoichiometry. For the GM engine operating with the aged catalyst, the
combined steps of cleaning the mixer and replacing the oxygen sensor improved overall catalyst
efficiency on the C2 duty cycle from 55 to 61 percent for NOx. CO conversion efficiency
improved only slightly. For the Mazda engine, the single step of cleaning the mixer slightly
decreased average catalyst efficiency on the C2 duty cycle for NOx emissions; HC and CO
conversion efficiency improved a small amount (see Table 4.2-4). Engines operating with new
catalysts showed the same general patterns. These data show that closed-loop fueling systems
can be relatively tolerant of problems related to fuel impurities.
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Chapter 4: Feasibility of Proposed Standards
Table 4.2-4
Average C2 Catalyst Conversion Efficiencies Before and After Maintenance
Engine
GM
Mazda
Pollutant
NOx
CO
HC
NOx
CO
HC
OLD CATALYST
before
maintenance
54.7%
96.3%
93.8%
62.3%
96.9%
86.9%
after
maintenance
61.1%
98.1%
93.6%
61.5%
98.9%
93.2%
NEW CATALYST
before
maintenance
45.6%
99.3%
93.6%
60.3%
99.6%
86.2%
after
maintenance
56.1%
99.5%
93.7%
60.1%
99.6%
94.3%
Manufacturers may nevertheless be concerned that some in-use operation can cause fuel
deposits that exceed the fuel system's compensating ability to maintain correct air-fuel ratios.
Two technologies are available to address this concern. First, the diagnostic system we are
proposing would inform the operator if fuel-quality problems are severe enough to prevent the
engine from operating at stoichiometry. A straightforward cleaning step would restore the fuel
system to normal operation. Manufacturers may also be able to monitor mixer performance
directly to detect problems with fuel deposits, rather than depending on air-fuel ratios as a
secondary indicator. In any case, by informing the operator of the need for maintenance, the
diagnostic system reduces the chance that the manufacturer will find high in-use emissions that
result from fuel deposits.
The second technology to consider is designed to prevent fuel deposits from forming. A
commercially available thermostat regulates fuel temperatures to avoid high-temperature and
low-temperature effects.
Maintaining the integrity of the exhaust pipe is another basic but essential element of
keeping control of air-fuel ratios. Any leaks in the exhaust pipe between the exhaust valves and
the oxygen sensor would allow dilution air into the exhaust stream. The extra oxygen from the
dilution air would cause the oxygen sensor to signal a need to run at a air-fuel ratio that is richer
than optimal. If an exhaust leak occurs between the oxygen sensor and the catalyst, the engine
will run at the right air-fuel ratio, but the extra oxygen would affect catalyst conversion
efficiencies. As evidenced by the test engines, manufacturers can select materials with sufficient
quality to prevent exhaust leaks over the useful life of the engine.
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Draft Regulatory Support Document
4.2.2.6 Gasoline-fueled engines
Most of the available emission data for Large SI engines is from LPG-fueled engines.
Gasoline-fueled engines, while less common, represent an important element of the market.
Emission-control technologies for automotive engines and heavy-duty highway engines have
advanced to the point of reducing emissions well below the standards we are proposing for Large
SI engines. The experience with these highway applications makes clear that gasoline-fueled
engines can achieve very low emissions.
Part of the concern expressed by manufacturers has been that gasoline-fueled engines
sometimes need to operate at rich air-fuel ratios for short periods to protect engines from
overheating. This generally causes higher CO emissions, while NOx emissions either decrease
or stay the same. Concern related to the feasibility of meeting emission standard with gasoline-
fueled engines are therefore mostly focused on achievable CO emission levels. Most people
understand that gasoline-fueled industrial engines have high CO emissions, so they generally
don't operate in indoor applications or in other enclosed areas. Controlling NOx emissions from
these engines therefore becomes relatively more important than controlling CO emissions.
To address this concern, we are proposing alternate emission standards that provide
flexibility in balancing the tradeoff between controlling NOx and CO emissions. We believe this
flexibility will allow manufacturers to achieve the greatest degree of emission reduction at the
lowest cost for their particular engines. See Section 4.2.2.7.3 for a discussion of the alternate
emission standards.
4.2.2.7 Proposed emission standards
4.2.2.7.1 Technology Basis
Three-way catalyst systems with electronic, closed-loop fuel systems have a great
potential to reduce emissions from Large SI engines. We believe these technologies are capable
of the greatest degree of emission reduction achievable from these engines in the projected time
frame, considering the various statutory factors. This reflects a concern for the cost sensitivity of
Large SI engines. In particular, we are not basing the proposed emission standards on the
emission-control capability from any of the following technologies.
- Spark timing
- Combustion-chamber redesign
- Gaseous fuel injection
Exhaust gas recirculation
Incorporating these technologies with new engines could further reduce emissions;
however, Large SI engine manufacturers typically produce 10,000 to 15,000 units annually,
which limits the resources available for an extensive development program. Considering the
limited development budgets for improving these engines, we believe it is more important to
make a robust design with basic emission-control hardware than to achieve very low emission
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Chapter 4: Feasibility of Proposed Standards
levels with complex hardware at a small number of steady-state test modes. Even without these
additional technologies, we anticipate that manufacturers will be able to reduce emissions by 90
percent or more from uncontrolled levels. Further optimizing an engine with a full set of
emission-control hardware while meeting transient and field-testing emission standards is more
of a cost burden than Large SI manufacturers can bear in the projected time frame.
Manufacturers producing new engines may find it best to use some of these supplemental
technologies to achieve the desired level of emission control and performance at an acceptable
cost.
4.2.2.7.2 Duty-cycle emission standards
The SwRI testing program was based on aged engines and involved no effort to fine-tune
air-fuel ratios or emission levels across the engine map. We expect that manufacturers will be
able to take steps to control emission levels more broadly across the range of engine speeds and
loads, which will correspondingly reduce transient emission levels. The data presented above
show that Large SI engines can meet the proposed 2007 emission standards for both steady-state
and transient duty cycles.
We project that the proposed emission standards will reduce NOx, HC, and CO emissions
by about 90 percent from uncontrolled levels. Further reductions may be possible with a very
extensive development effort to adapt advanced highway engine technologies to nonroad
applications. We have, for example, adopted emission standards for gasoline-fueled engines for
highway trucks that will require manufacturers to reduce emissions by 80 or 90 percent beyond
the levels we are proposing for Large SI engines. Due to the relatively low sales volumes of
Large SI engines, we believe it is not appropriate to propose standards at these more stringent
levels. With smaller R&D budgets, Large SI engine manufacturers will need to apply a focused
effort to meet the standards we are proposing.
On the other hand, the proposed emission standards for Large SI engines are significantly
more stringent than those we are proposing for recreational vehicles and those we have adopted
for lawn & garden engines. We believe this is appropriate, for several reasons. First, the
similarity to automotive engines makes it possible to use basic automotive technology that has
already been adapted to industrial use. Second the cost of Large SI equipment is typically much
higher than the recreational or other light-duty products, so there is more capability for
manufacturers to pass along cost increases in the marketplace. Third, the proposed Large SI
emission standards correspond with a substantial fuel savings, which offset the cost of regulation
and provide a great value to the many commercial customers.
The SwRI testing program involved about eight weeks of development effort to
characterize and modify two engines to for optimized emissions on the steady-state and transient
duty cycles, and for all kinds of off-cycle operation. Both of the test engines had logged several
thousand hours of operation using off-the-shelf technologies that have been available for nonroad
engines for many years. Several hardware and software adjustments were made to maintain
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Draft Regulatory Support Document
optimal air-fuel ratios for effective control of all pollutants under all operating modes. Some
further development effort will be necessary to address the few isolated modes with high
emission levels, as described below. Manufacturers may save development time by upgrading to
the modestly more expensive controller with independent air-fuel control capability in different
speed-load zones. We believe that the several years until 2007 allow enough lead time for
manufacturers to carry out this development effort for all their engines.
We expect the SwRI testing program to provide extensive, basic information on
optimizing the subject engines for low emissions, so manufacturers will need significantly less
time and testing resources to modify additional engine models. For example, the SwRI testing
shows how emissions change over varying speeds and loads; as a result, future testing can focus
on far fewer test points to characterize a calibration. The test results also show how
manufacturers will need to balance calibrations for controlling emissions of different pollutants
across the range of engine speeds and loads.
Given the control technology, as described above, there is a need to select emission
standards that balance the tradeoff between NOx and CO emissions. Both NOx and CO vary
with changing air-fuel ratios, but in an inverse relationship. This is especially important
considering the degree to which these engines are used on enclosed areas. Table 4.2-5 shows the
range of measured emission values from the engines with optimized emission controls. These
values are plotted in Figure 4.2-7, showing the NOx-CO tradeoff. The measured emission levels
include a variety of duty cycles, but this doesn't seem to affect the observed trends. Also,
Table 4.2-5 notes the length of time the engine was turned off before starting the transient duty
cycle. All the data points shown are from measurements with the aged catalysts. Several
measurements with the new catalyst showed that engines were able to achieve very low levels of
both NOx and CO emissions.
Figures 4.2-8 and 4.2-9 show two attempts to apply a curve-fit to the data points. Using a
log-log relationship as shown yielded an R-square value of 0.93, indicating a relatively good fit
to the data. Similarly, the best curve-fit with the I/CO relationship has an R-square value of
0.83. Table 4.2-6 shows a range of values relating CO and HC+NOx emission levels. This
involves starting with a set of CO emission levels, then selecting the HC+NOx emission level
corresponding with the higher of the two values predicted by the two curve-fitting equations.
Finally, both CO and HC+NOx emission levels are increased by 10 percent to account for a
compliance margin around the measured data points. This collection of points, shown in
Figure 4.2-10, serve as a range of possible combinations of CO and HC+NOx emission
standards.
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Chapter 4: Feasibility of Proposed Standards
Table 4.2-5
Range of Measured Emission Levels (g/hp-hr)
Engine*
GM
GM
GM
GM
GM
GM
Mazda
Mazda
Mazda
Mazda
Mazda
Mazda
HC
0.30
0.27
0.41
0.29
0.27
0.28
0.34
0.58
0.61
0.66
0.6
0.51
NOx
3.82
4.14
5.91
5.89
4.42
5.33
0.88
0.15
0.19
0.14
0.35
0.7
HC+NOx
4.12
4.41
6.32
6.18
4.69
5.61
1.22
0.73
0.8
0.8
0.95
1.21
CO
0.66
0.68
0.83
0.86
0.87
0.89
4.61
6.66
6.97
7.5
7.61
776
Cycle
Backhoe-loader
Backhoe-loader
Backhoe-loader
Large SI Composite
Highway FTP
Highway FTP
Highway FTP
Large SI Composite
Large SI Composite
Large SI Composite
Large SI Composite
Welder
soak, min.
4
2
20
6
3
3
5
5
5
5
7
4
*Both engines operated on LPG for all tests.
Figure 4.2-7
HC+NOx vs. CO
7 .
I
fi
o
-C «
1 **
Q.
.C "
m A
X~
9s
^? &
+ _
^2
x ^
•i_
i
0-
*
0
0
0
0
0
0
o <;
0
ov
123456789
CO, g/hp-hr
-------
Draft Regulatory Support Document
4-30
-------
Chapter 4: Feasibility of Proposed Standards
Figure 4.2-8
1.
0 8 -
006
~z.
+
o n 4
:-i u.i
O)
o n 9
_j u-^
0 9
Log HC+NOx vs Log CO
UV
o
°
Log (HC+NOx) = -0.78 Log CO + 0.63
R-square = 0.93
o o
o
o°°
u-i I , ^ , ^ , ^ , ^ , ! , ! , !
-0.4 -0.2 0 0.2 0.4 0.6 0.8
Log CO
1
Figure 4.2-9
HC+NOx vs. 1/CO
81
•^ 6
Q.
•gj
X A.
o 4
O
I 2
0
HC+NOx = 3.5/CO + 0.59
R-square = 0.83
0 °
o
o
o
0
o
<^>
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
1/CO
-------
Draft Regulatory Support Document
Table 4.2-6
Range of Feasible Emission Standards
CO
Emission Level
1.0
1.5
1.75
2.0
2.3
2.5
3.0
4.0
5.0
6.0
7.0
8.0
9.0
100
Predicted
HC+NOx
Emission Level
(Los. basis")
4.27
3.11
2.76
2.48
2.27
2.09
1.81
1.45
1.22
1.05
0.94
0.84
0.77
071
Predicted
HC+NOx
Emission Level
(I/CO basis")
4.09
2.92
2.59
2.34
2.15
1.99
1.76
1.47
1.29
1.17
1.09
1.03
0.98
094
Higher Predicted
HC+NOx
Emission Level
4.27
3.11
2.76
2.48
2.27
2.09
1.81
1.47
1.29
1.17
1.09
1.03
0.98
094
HC+NOx
standard*
4.7
3.4
3.0
2.7
2.5
2.3
2.0
1.6
1.4
1.3
1.2
1.1
1.1
1.0
CO
standard*
1.1
1.7
1.9
2.2
2.5
2.8
3.3
4.4
5.5
6.6
7.7
8.8
9.9
110
Incorporates 10-percent compliance margin.
4-32
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Chapter 4: Feasibility of Proposed Standards
We generally set standards by focusing on attaining ambient air quality in broad outdoor
areas. Any of the emission standards under consideration would provide large reductions to
address this concern. More careful balancing of CO and HC+NOx emission standards would
allow us to simultaneously address concerns for individual exposure to elevated levels of CO,
NO, and NO2.
Modeling a scenario of indoor engine operation allows us to evaluate the relative
exposure of different pollutants under varying engine calibrations. Since the analysis relates
primarily to the relative concentrations of the different pollutants, the conclusions drawn here are
relatively insensitive to the simplifying assumptions in the calculations. Calculations are based
on a forklift operating for eight hours at 20 hp (on average) in a 40' by 60' room with a 20'
ceiling. With a dilution rate of one full air exchange per hour, the effective volume is
432,000 ft3. This volume of air has a mass of about 14,000 kg (or 500,000 moles). Hydrocarbon
emissions are estimated to be 20 percent of the total HC+NOx emissions rate, which is typical
for Large SI engines. Similarly, the analysis estimates that 90 percent of NOx emissions are NO,
with the remainder being NO2. Plugging in several values from the candidate combinations of
emission standards in Figure 4.2-10 results in a shifting balance of HC+NOx and CO emissions.
Table 4.2-7 shows the calculated resulting ambient ppm levels for three different
scenarios and compares these values to the threshold limit value published by the American
Conference of Governmental Industrial Hygienists. The scenario with emission standards of
3.0 g/hp-hr HC+NOx and 1.9 g/hp-hr CO shows equal relative protection from NO and CO
exposures, with both values somewhat lower than the threshold limit values. The second
scenario with emission standards of 2.5 g/hp-hr HC+NOx and 2.5 g/hp-hr CO shows the
expected shift to lower ambient NO levels, with CO levels slightly over the threshold limit value.
The third scenario with emission standards of 2.0 g/hp-hr HC+NOx and 3.3 g/hp-hr CO shows
ambient NO levels decreasing to 14 ppm, with ambient CO up to 34 ppm. We are proposing
emission standards of 2.5 g/hp-hr for both HC+NOx and for CO as the most appropriate balance
in setting emission standards for these pollutants.
4-33
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Draft Regulatory Support Document
Figure 4.2-10
51
1
Q.
.C
o) 3
+
o -
1 1
0
Range of Feasible Emission Standards
\. Incorporates 10 percent compliance margin.
V^
^ o
0123456
CO, g/hp-hr
Table 4.2-7
Exposure Scenario for Indoor Operation*
Emission standards,
g/hp-hr
HC+NOx
3.0
2.5
2.0
CO
0.9
2.5
3.3
Pollutant
NO
NO2
CO
NO
NO2
CO
NO
NO2
CO
Emission factor
(g/hp-hr)
2.2
0.2
1.9
1.8
0.2
2.5
1.4
0.2
3.3
Emission
rate, g
311
35
274
259
29
360
207
23
475
Emission
rate, mol
10.4
0.8
9.8
8.6
0.6
12.9
6.9
0.5
17
Ambient
ppm
21
1.5
20
17
1.3
26
14
1.0
34
Threshold Limit
Value
25
3
25
25
3
25
25
3
25
*Based on emission standards of 3.0 g/hp-hr for HC+NOx and 1.9 g/hp-hr for CO.
4-34
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Chapter 4: Feasibility of Proposed Standards
4.2.2.7.3 Alternate emission standards
As described in Section 4.2.2.7, we believe that gasoline-fueled engines are most likely to
utilize the proposed alternate emission standards, which allow for more stringent NOx+HC
emission standards with less stringent CO emission standards. As engines increase their CO
emission levels, they are generally capable of achieving lower NOx emission levels. Preliminary
data suggest that Large SI engines can meet a 1.0 g/hp-hr HC+NOx emission level when CO
emission levels are allowed to increase up to 20 g/hp-hr.
Ongoing testing efforts at SwRI are focused on achieving effective emission control from
a gasoline-fueled industrial engine. As we continue this testing, we intend to place emission
testing results in the docket as soon as they become available.
4.2.2.7.4 Field-testing emission standards
We are proposing to allow manufacturers to do testing under the in-use testing program
using field-testing procedures. This has the potential to substantially reduce the cost of testing.
Setting an emission standard for testing engines in the field requires that we take into account all
the variability inherent in testing outside the laboratory. As discussed further below, this
includes varying engine operation, and a wider range of ambient conditions, and the potential for
less accurate or less precise emission measurements and calculations. Also, while the proposed
field-testing standards and procedures are designed for testing engines installed in equipment,
engines can also be tested on a dynamometer to simulate what would happen in the field. In this
case, extra precautionary steps would be necessary to ensure that the dynamometer testing could
be characterized as "normal operation." Also, the less stringent field-testing standards would
apply to any simulated field-testing on a dynamometer to take emission-measurement variability
into account, as described below.
The SwRI test engines also show that Large SI engines are capable of controlling
emissions under the wide range of operation covered by the proposed field-testing provisions. A
modest amount of additional development would be necessary to address isolated high-emission
points uncovered by the testing, but the above discussion makes clear that it would be feasible to
resolve these issues well before 2007. Field testing may also include operation at a wider range
of ambient conditions than for certification testing. Selecting emission standards for field testing
that correspond with the duty-cycle standards requires consideration of the following factors:
The data presented above show that emissions vary for different modes of engine
operation. Manufacturers will need to spend time addressing high-emission
points to ensure that engines are not overly sensitive to operation at certain speeds
or loads. The data suggest that spark-ignition engines can be calibrated to
improve control at the points with the highest emission rates.
Established correction factors allow for adjustment to account for varying ambient
conditions. Allowing adjustment of up to 10 percent would adequately cover any
potential increase in emissions resulting from extreme conditions.
4-35
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Draft Regulatory Support Document
While emission measurements with field-testing equipment allow more flexibility
in testing, they are not as precise or as accurate as in the laboratory; the proposed
regulations define specifications to limit the error in emission measurements. For
most mass-flow and gas analyzer hardware, these tolerance remain quite small.
Measurements and calculations for torque values introduce a greater potential for
error in determining brake-specific emission levels. The proposed tolerance for
onboard torque readings allows for a 15-percent error in understating torque
values, which would translate into a 15-percent error in overstating brake-specific
emissions.
Taking all these factors into account, we believe it is appropriate to allow for a 40-percent
increase in HC+NOx emissions relative to the SwRI measured values to account for the factors
listed above. CO emissions are generally somewhat more sensitive to varying engine operation,
so a 50-percent adjustment is appropriate for CO. We are therefore proposing field-testing
emission standards of 3.5 g/hp-hr THC+NOx and 3.8 g/hp-hr CO.
These same numerical field-testing standards would apply to natural gas engines. Much
like for certification, we are proposing to exclude methane measurements from natural gas
engines. Since there are currently no portable devices to measure methane (and therefore
nonmethane hydrocarbons), we are proposing that the 3.5 g/hp-hr field-testing standard apply
only to NOx emissions for natural gas engines.
We would expect to apply the same adjustments to the alternate emission standards to
select the appropriate field-testing standard for these engines. As a result, we are proposing
alternate field-testing standards of 1.4 g/hp-hr HC+NOx and 31 g/hp-hr CO.
4.2.2.7.5 Evaporative emissions
Several manufacturers are currently producing products with pressurized fuel tanks to
comply with Underwriters Laboratories specifications. Most fuel tanks in industrial applications
are made of a thick-grade sheet metal or structural steel, so increasing fuel pressures within the
anticipated limits poses no risk of bursting or collapsing tanks. For those few applications that
use plastic fuel tanks or thinner sheet steel, straightforward technologies such as insulation or a
volume-compensating bag would allow for adequate suppression of fuel vapors.
4.2.2.7.6 Conclusions
Manufacturers have been developing emission-control technologies to meet the proposed
2004 emission standards since October 1998, when California ARB adopted the same standards.
We expect that manufacturers will add three-way catalysts to their engines and use electronic
closed-loop fueling systems. These technologies have been available for industrial engines for
many years.
As described above, technology development has shown that these technologies can be
4-36
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Chapter 4: Feasibility of Proposed Standards
optimized to achieve the more stringent emission standards proposed for 2007 and later engines.
The testing effort on aged engines with off-the-shelf hardware showed that engines can meet not
only the proposed steady-state emission standards, but also the standards that would apply to
testing with the proposed transient duty cycles. Similarly, testing over a wide range of engine
operation has shown that engines with the these established emission-control technologies can
meet the field-testing standards under any normal operation.
4.2.3 Impacts on Noise, Energy, and Safety
The Clean Air Act directs us to consider potential impacts on noise, energy, and safety
when establishing the feasibility of emission standards for nonroad engines.
As automotive technology demonstrates, achieving low emissions from spark-ignition
engines can correspond with greatly reduced noise levels. Electronically controlled fuel systems
are able to improve management the combustion event, and catalysts can be incorporated into
existing equipment designs without compromising the muffling capabilities in the exhaust.
Adopting new technologies for controlling fuel metering and air-fuel mixing will lead to
substantial improvements in fuel consumption rates. We project fuel consumption improvements
that will reduce total nationwide fuel consumption by about 300 million gallons annually once
the program is fully phased in. While a small number of engines already have these
technologies, it seems that the industrial engine marketplace has generally not valued fuel
economy highly enough to create sufficient demand for these technologies.
We believe the technology discussed here would have no negative impacts on safety.
Electronic fuel injection is almost universally used in cars and trucks in the United States with
very reliable performance. In addition, we expect cases of CO poisoning from these engines to
decrease as a result of the reduced emission levels.
4-37
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Draft Regulatory Support Document
4.3 Snowmobiles
The following paragraphs summarize the data and rationale supporting the proposed
emission standards for snowmobiles, which are listed in the Executive Summary.
4.3.1 Baseline Technology and Emissions
Snowmobiles are equipped with relatively small high-performance two-stroke two and
three cylinder engines that are either air- or liquid-cooled. The main emphasis of engine design
is on performance, durability, and cost and, because these engines are currently unregulated, they
have no emission controls. The fuel system used on these engines are almost exclusively
carburetors, although a small number have electronic fuel injection. Two-stroke engines
lubricate the piston and crankshaft by mixing oil with the air and fuel mixture. This is
accomplished by most contemporary 2-stroke engines with a pump that sends two-cycle oil from
a separate oil reserve to the carburetor where it is mixed with the air and fuel mixture. Some less
expensive two-stroke engines require that the oil be mixed with the gasoline in the fuel tank. In
fact, because performance and durability are such important qualities for snowmobile engines,
they all operate with a "rich" air and fuel mixture. That is, they operate with excess fuel, which
enhances performance and allows engine cooling which promotes longer lasting engine life.
However, rich operation results in high levels of HC, CO, and PM emissions. Also, two-stroke
engines tend to have high scavenging losses, where up to a third of the unburned air and fuel
mixture goes out of the exhaust resulting in high levels of raw HC.
We developed average baseline emission rates for snowmobiles based on the results of
emissions testing of 23 snowmobiles.20 Current average snowmobile emissions rates are 397
g/kW-hr (296 g/hp-hr) CO and 149 g/kW-hr (111 g/hp-hr) HC.
4.3.2 Potentially Available Snowmobile Technologies
A variety of technologies are currently available or in stages of development to be
available for use on 2-stroke snowmobiles. These include engine modifications, improvements
to carburetion (improved fuel control and atomization, as well as improved production
tolerances), enleanment strategies for both carbureted and fuel injected engines, pulse air, and
semi-direct and direct fuel injection. In addition to these 2-stroke technologies, converting to 4-
stroke engines may be feasible for some snowmobile types. Each of these is discussed in the
following sections.
4.3.2.1 Engine Modifications
There are a variety of engine modifications that could reduce emissions from two-stroke
engines. The modifications generally either increase trapping efficiency (i.e., reduce fuel short-
circuiting) or improve combustion efficiency. Those modifications that increase trapping
efficiency include optimizing the intake, scavenge and exhaust port shape and size, and port
placement, as well as optimizing port exhaust tuning and bore/stroke ratios. Optimized
4-38
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Chapter 4: Feasibility of Proposed Standards
combustion charge swirl, squish and tumble would serve to improve the combustion of the intake
charge. These modifications have the potential to reduce emissions by up to 40 percent,
depending on how well the unmodified engine is optimized for these things.
4.3.2.2 Carburetion Improvements
There are several things that can be done to improve carburetion in snowmobile engines.
First, strategies to improve fuel atomization would promote more complete combustion of the
fuel/air mixture. Additionally, production tolerances could be improved for more consistent fuel
metering. Both of these things would allow for more accurate control of the air/fuel ratio. In
conjunction with these improvements in carburetion, the air/fuel ration could be leaned out some.
Snowmobile engines are currently calibrated with rich air/fuel ratios for durability reasons.
Leaner calibrations would serve to reduce CO and HC emissions by up to 20 percent, depending
on how lean the unmodified engine is prior to recalibration. Small improvements in fuel
economy could also be expected with recalibration.
The calibration changes just discussed (as well as some of the engine modifications
previously discussed) would also reduce snowmobile engine durability. There are many engine
improvements that could be made to regain lost durability that occurs with leaner calibration.
These include changes to the cylinder head, pistons, ports and pipes to reduce knock. In addition
critical engine components could be made more robust to improve durability.
The same calibration changes to the air/fuel ratio just discussed for carbureted engines
could also be employed, possibly with more accuracy, with the use of fuel injection. At least one
major snowmobile manufacturer currently employs electronic fuel injection on several of its
snowmobile models.
4.3.2.3 Pulse Air
Pulse air injection into the exhaust stream mixes oxygen with the high temperature HC
and CO in the exhaust. The added oxygen allows the further combustion of these exhaust
constituents between the combustion chamber and tailpipe exhaust. Pulse air can achieve 10 to
40 percent reductions in four-stroke applications, and we expect some modest reductions in two-
stroke applications as well.
4.3.2.4 Direct and Semi-direct Fuel Injection
In addition to rich air/fuel ratios, one of the main reasons that emissions from two-stroke
engines are high is scavenging losses, as described above. One way to reduce or eliminate such
losses is to inject the fuel into the cylinder after the exhaust port has closed. This can be done by
injecting the fuel into the cylinder through the transfer port (semi-direct injection) or directly into
the cylinder (direct injection). Both of these approaches are currently being used successfully in
two-stroke personal watercraft engines. Manufacturers have indicated to us that two-stroke
engines equipped with direct fuel injection systems could reduce HC emissions by 70 to 75
4-39
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Draft Regulatory Support Document
percent and reduce CO emissions by 50 to 60 percent. Certification results for 1999 and 2000
model year outboard engines and PWC support the manufacturers projections, as shown in Table
4.3-1. This table shows the paired certification data from some PWC engines in both
uncontrolled and direct injection configurations. The percent difference in FEL column refers to
the HC + NOx FEL. This is a pretty good surrogate for HC since most of the HC + NOx level is
made up of HC, as can be seen from the table.
Table 4.3-1
Certification Levels of Direct Injection vs. Uncontrolled Engines
Mfr
Kawasaki
Arctic Cat
Bombardier
Polaris
%
difference
in FEL
50%
55%
60%
70%
size
(liter)
1.074
1.073
1.104
1.103
0.9514
0.9513
1.16
1.16
power
(kw)
95.6
88.3
84.31
88
88.85
89.5
85.26
93.25
FEL
(HC +
NOx)
70.0
140.0
75
167
54.06
136.8
46.0
149.4
HCcert
level
58.4
136.76
69.09
not
reported
45.98
136.20
37.46
not
reported
CO cert
level
148.6
241.8
148.56
not
reported
143.0
361.30
100.4
not
reported
Technology
Direct injection,
electronic control
none
Direct injection
none
Direct injection,
electronic control
none
Direct injection
none
Substantial improvements in fuel economy could also be expected with these
technologies. We believe these technologies hold promise for application to snowmobiles.
Manufacturers must address a variety of technical design issues for adapting the technology to
snowmobile operation, such as operating in colder ambient temperatures and at variable altitude.
The several years of lead time give manufacturers time to incorporate these development efforts
into their overall research plan as they apply these technologies to snowmobiles.
4.3.2.5 Four-stroke Engines
In addition to the two-stroke technologies just discussed, the use of four-stroke engines in
snowmobiles is feasible. One manufacturer has already introduced a four-stroke snowmobile on
a limited basis, with wider availability planned, and another is preparing for the introduction of a
four-stroke model. Since four-stroke engines do not rely on scavenging of the exhaust gases with
the incoming air/fuel mixture, they have inherently lower HC emissions compared to two-strokes
4-40
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Chapter 4: Feasibility of Proposed Standards
(up to 90 percent lower). Somewhat lesser reductions in CO could also be expected. Four-stroke
engines have a lower power to weight ratio than two-stroke engines. Thus, they are more likely
to be used in snowmobile models where extreme power and acceleration are not the primary
selling points. Such models include touring and sport trail sleds, as opposed to high performance
sleds such as those used for aggressive trail, cross country, mountain and lake riding.
4.3.3 Test Procedure
We are proposing to largely adopt the snowmobile test procedure developed by
Southwest Research Institute in cooperation with the International Snowmobile Manufacturers
Association for all snowmobile emissions testing.21 This test procedure consists of two main
parts; the duty cycle that the snowmobile engine would operate over during testing and other
testing protocols surrounding the measurement of emissions (sampling and analytical equipment,
specification of test fuel, atmospheric conditions for testing, etc.). While the duty cycle we are
proposing was developed specifically to reflect snowmobile operation, many of the testing
protocols are well established in other EPA emissions programs and have been simply adapted
where appropriate for snowmobiles.
The snowmobile duty cycle was developed by instrumenting several snowmobiles and
operating them in the field in a variety of typical riding styles, including aggressive (trail),
moderate (trail), double (trail with operator and one passenger), freestyle (off-trail), and lake
driving. A statistical analysis of the collected data produced the five mode steady-state test cycle
shown in Table 4.3-2.
Table 4.3-2
Proposed Snowmobile Engine Test Cycle
Mode
Normalized
Speed
Normalized
Torque
Relative
Weighting
(%)
1
1
1
12
2
0.85
0.51
27
3
0.75
0.33
25
4
0.65
0.19
31
5
Idle
0
5
We believe this duty cycle is representative of typical snowmobile operation, and is
therefore appropriate for use in demonstrating compliance with the proposed snowmobile
emission standards.
The other testing protocols we are proposing are largely derived from our regulations for
marine outboard and personal watercraft engines.22 The testing equipment and procedures from
that regulation are largely appropriate for snowmobiles. However, unlike snowmobiles, outboard
4-41
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Draft Regulatory Support Document
and personal watercraft engines tend to operate in fairly warm ambient temperatures. Thus, some
provision needs to be made in the snowmobile test procedure to account for the colder ambient
temperatures typical of snowmobile operation. Since snowmobile carburetors are jetted for
specific ambient temperatures and pressures, we could take one of two general approaches. The
first is to require testing at ambient temperatures typical of snowmobile operation, with
appropriate jetting. A variation of this option is to simply require that the engine inlet air
temperature be representative of typical snowmobile operation, without requiring that the entire
test cell be at that temperature. The second is to allow testing at higher temperatures than
typically experienced during snowmobile operation, with jetting appropriate to the warmer
ambient temperatures.
We are proposing that snowmobile engine inlet air temperature be between -15°C and -
5 °C (5 °F and 23 °F), but that the ambient temperature in the test cell not be required to be
refrigerated. We believe that this approach strikes an appropriate balance between the need to
test at conditions that are representative of actual use, and the fact that simply cooling the inlet
air would be significantly less costly than requiring a complete cold test cell.
4.3.4 Impacts on Noise, Energy, and Safety
The Clean Air Act directs us to consider potential impacts on noise, energy, and safety
when establishing the feasibility of emission standards for nonroad engines.
As automotive technology demonstrates, achieving low emissions from spark-ignition
engines can correspond with greatly reduced noise levels. Four-stroke engines can have
considerably lower sound levels than two-stroke engines. Electronically controlled fuel systems
are able to improve management of the combustion event which can help lower noise levels.
Adopting new technologies for controlling fuel metering and air-fuel mixing will lead to
substantial improvements in fuel consumption rates for two-stroke engines as well as for four-
stroke engines. Four-stroke engines have far less fuel consumption than two-stroke engines.
Average mileage for a baseline two-stroke snowmobile is 12 miles per gallon (mpg). Average
mileage for a four-stroke snowmobile is 18 mpg and up to 20 mpg for a two-stroke with direct
injection. We project that these fuel consumption benefits will reduce total nationwide fuel
consumption by more than 50 million gallons annually once the program is fully phased in.
We believe the technology discussed here would have no negative impacts on safety.
Electronic fuel injection is almost universally used in cars, trucks and highway motorcycles in the
United States with very reliable performance.
4.3.5 Conclusion
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Chapter 4: Feasibility of Proposed Standards
4.3.6.1 2006 Standards
We expect that the proposed 2006 model year snowmobile emission standards will
largely be met through a combination of engine modifications and carburetion improvements.
However, the other technologies discussed have the potential to reduce emissions beyond what
could be expected from engine modifications and carburetion improvements. These other
technologies also have potential benefits beyond emission reductions (e.g., improved fuel
economy, reliability and performance, reduced noise). We expect that as snowmobile
manufacturers develop and refine these other technologies they will find their way into the
marketplace in certain applications where their non-emissions benefits would outweigh their
cost.
4.3.6.2 2010 Standards
There are a number of different technology mixes which could be used to meet the
proposed 50 percent average reductions in HC and CO. The Table 4.3-3 provided below presents
the approach we used for purposes of further analysis. The average reduction level at the bottom
of the table represents average reductions for a manufacturer's entire fleet which already
incorporates compliance margin consideration, since each engine family FEL will have a unique
compliance margin. The percent reduction presented in the table are based on CO, since it is
likely to be the pollutant most difficult to control. Larger HC reductions would be achieved with
these technologies. Obviously, a manufacturer could change the technology mix based on cost
and performance considerations. For example, the percent of direct injection two-stroke engine
could be increased thus allowing fewer four-stroke or more modified two-stroke engines (e.g.,
calibration & engine modifications). We expect the manufacturers to select the most technically
attractive and cost-effective approach which meet their perceived customer needs. Clearly there
are options available to accomplish this goal.
Table 4.3-3
Potential Snowmobile Technology Mix for 2010
Technology
Carburetor/EFI
Recalibration + Engine
Modifications + Pulse
Air Injection
Direct Injection
Four- Stroke
Average Reduction
Percent Reduction
35%
70%
50%
Percent Use to Meet
Standard
50%
40%
10%
Total Percent
Reduction
0.175
0.280
0.050
0.505
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Draft Regulatory Support Document
4-44
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Chapter 4: Feasibility of Proposed Standards
4.4 All-Terrain Vehicles
The following paragraphs summarize the data and rationale supporting the proposed
emission standards for ATVs, which are listed in the Executive Summary.
4.4.1 Baseline Technology and Emissions
ATVs have been in existence for many years, but have only become popular over the last
25 years. Some of the earliest and most popular ATVs were three-wheeled off-highway
motorcycles with large balloon tires. Due to safety concerns, the three-wheeled ATVs were
phased-out in the mid-1980s and replaced by the current and more popular vehicle known as
"quad runners" or simply "quads." Quads resemble the earlier three-wheeled ATVs except the
single front wheel was replaced with two wheels that are controlled by a steering system. The
ATV steering system uses motorcycle handlebars, but otherwise looks and operates like an
automotive design. The operator sits on and rides the quad much like a motorcycle. The engines
used in quads tend to be very similar to those used in off-highway motorcycles - relatively small
single cylinder two- or four-stroke engines that are either air- or liquid-cooled. Recently, some
manufacturers have introduced ATVs equipped with larger four-stroke two-cylinder V-twin
engines. Quads are typically divided into two types: utility and sport. The utility quads are
designed for recreational use but have the ability to perform many utility functions such as
plowing snow, tilling gardens, and mowing lawns to name a few. They are typically heavier and
equipped with relatively large four-stroke engines and automatic transmissions with reverse gear.
Sport quads are smaller and designed primarily for recreational purposes. They are equipped
with two- or four-stroke engines and manual transmissions.
There are two other types of ATVs, although they are not nearly as common as quad
runners. Both types of vehicles are equipped with six wheels. The first type looks similar to a
large golf cart, with a bed for hauling cargo much like a pick-up truck. These ATVs are typically
manufactured by the same companies that make quad runners and use similar engines. The other
type of six-wheeled ATV is an amphibious unit that can operate in water as well as on land.
These ATVs are typically equipped with small spark-ignition gasoline-powered engines similar
to those found in lawn and garden tractors, rather than the motorcycle engines used in quads,
although some also use large SI engines as well.
Although ATVs are not currently regulated federally, they are regulated in California.
The California ATV standards are based on the FTP cycle just like highway motorcycles,
however, they allow manufacturers to optionally certify to a steady-state engine cycle (SAE
J1088) and meet the California non-handheld small SI utility engine standards. Manufacturers
have felt that these standards are unattainable with two-stroke engine technology. Therefore, all
of the ATVs certified in California are equipped with four-stroke engines. California ultimately
allowed manufacturers to sell uncertified engines as long as those ATVs and motorcycles
equipped with these engines were operated exclusively on restricted public lands and at specified
times of the year. This allowed manufacturers to continue to manufacture and sell two-stroke
ATVs in California. Thus, the main emphasis of ATV engine design federally, and for two-
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stroke powered ATVs in California, is on performance, durability, and cost. Although some
manufacturers offer some of their California models nationwide, most ATVs sold federally have
no emission controls.
ATVs predominantly use four-stroke engines (e.g., 80 percent of all sales are four-stroke).
The smaller percentage of two-stroke engines are found primarily in the small engine
displacement "youth" models. Of the seven major ATV manufacturers, only two make two-
stroke ATVs for adults. These models are either inexpensive entry models or high-performance
sport models. The fuel system used on ATVs, whether two- or four-stroke, are almost
exclusively carburetors, although at least one manufacturer has introduced a four-stroke ATV
with electronic fuel injection. Although ATVs are mostly four-stroke equipped, they still can
have relatively high levels of HC and extremely high levels of CO, because many of them
operate with a "rich" air and fuel mixture, which enhances performance and allows engine
cooling which promotes longer lasting engine life. This is also true for two-stroke equipped
ATVs. Rich operation results in high levels of HC, CO, and PM emissions. In addition, two-
stroke engines lubricate the piston and crankshaft by mixing oil with the air and fuel mixture.
This is accomplished by most contemporary 2-stroke engines with a pump that sends two-cycle
oil from a separate oil reserve to the carburetor where it is mixed with the air and fuel mixture.
Some less expensive two-stroke engines require that the oil be mixed with the gasoline in the
fuel tank. Because two-stroke engines tend to have high scavenging losses, where up to a third
of the unburned air and fuel mixture goes out of the exhaust, lubricating oil particles are also
released into the atmosphere, becoming HC particles or particulate matter (PM). The scavenging
losses also result in high levels of raw HC. This is in contrast to four-stroke engines that use the
crankcase as an oil sump and a pump to distribute oil throughout the engine, resulting in virtually
noPM..
We tested five adult four-stroke and two youth two-stroke ATVs over the FTP. Tables
4.4-1 and 4.4-2 shows that the HC emissions for the four-stroke ATVs is significantly lower than
for the two-stroke ATVs, whereas the NOx emissions from the two-strokes were considerably
lower. Although the two-stroke ATVs tested were youth models, it can be argued that the
emissions from these two models are lower than what could be expected from larger engines,
since smaller displacement engines typically generate less emissions. The CO emissions were
also lower for the two-stroke ATVs. The four-stroke ATVs that we tested that had high levels of
CO happened to be 50-state certified vehicles, meaning they are California vehicles sold
nationwide. Because there are California standards for HC+NOx, manufacturers have tended to
calibrate the ATVs even richer then normal to meet the NOx standard. Since the CO standard in
California is relatively high, these ATVs can run rich and still meet the CO standards.
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Table 4.4-1
Four-Stroke ATV Emissions (g/km)
Make
Kawasaki
Honda
Polaris
Yamaha
Polaris
Model
Bayou
300EX
Trail Boss
Banshee
Sportsman
Model
Year
1989
1997
1998
1998
2001
Eng. Displ.
280 cc
298 cc
324 cc
349 cc
499 cc
Average
HC
1.17
1.14
1.56
0.98
2.68
1.51
CO
14.09
34.60
43.41
19.44
56.50
33.61
NOx
0.640
0.155
0.195
0.190
0.295
0.295
Table 4.4-2
Two-Stroke ATV Emissions (g/km)
Make
Suzuki
Polaris
Model
LT80
Scrambler
Model
Year
1998
2001
Eng. Displ.
79 cc
89 cc
Average
HC
7.66
38.12
22.89
CO
24.23
25.08
24.66
NOx
0.047
0.057
0.052
4.4.2 Potentially Available ATV Technologies
A variety of technologies are currently available or in stages of development to be
available for use on two-stroke ATVs, such as engine modifications, improvements to
carburetion (improved fuel control and atomization, as well as improved production tolerances),
enleanment strategies for both carbureted and fuel injected engines, and semi-direct and direct
fuel injection. However, it is our belief that manufacturers will choose to convert their two-
stroke engines to four-stroke applications, because of the cost and complexity of the above
mentioned technologies necessary to make a two-stroke engine meet our proposed standards. For
our proposed phase 1 standards, we believe that a four-stroke engine with minor improvements
to carburetion and enleanment strategies will be all that is required. For our proposed phase 2
standards, we believe the use of a four-stroke engine with improved carburetion or possible use
of electronic fuel injection, enleanment strategies, possible engine modifications, secondary air
and/or possibly the use of a oxidation catalyst will be necessary. Each of these is discussed in
the following sections.
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4.4.2.1 Engine Modifications
There are a variety of engine modifications that could reduce emissions from two-stroke
and four-stroke engines. The modifications generally either increase trapping efficiency (i.e.,
reduce fuel short-circuiting) or improve combustion efficiency. Those modifications for two-
stroke engines that increase trapping efficiency include optimizing the intake, scavenge and
exhaust port shape and size, and port placement, as well as optimizing port exhaust tuning and
bore/stroke ratios. Optimized combustion charge swirl, squish and tumble would serve to
improve the combustion of the intake charge for both two- and four-stroke engines. These
modifications for two-stroke engines have the potential to reduce emissions by up to 40 percent,
depending on how well the unmodified engine is optimized for these things, but would be
insufficient alone to meet our proposed phase 1 standards.
4.4.2.2 Carburetion Improvements
There are several things that can be done to improve carburetion in ATV engines. First,
strategies to improve fuel atomization would promote more complete combustion of the fuel/air
mixture. Additionally, production tolerances could be improved for more consistent fuel
metering. Both of these things would allow for more accurate control of the air/fuel ratio. In
conjunction with these improvements in carburetion, the air/fuel ratio could be leaned out some.
ATV engines are currently calibrated with rich air/fuel ratios for durability and performance
reasons. Leaner calibrations would serve to reduce CO and HC emissions by up to 20 percent,
depending on how lean the unmodified engine is prior to recalibration. Small improvements in
fuel economy could also be expected with recalibration.
The calibration changes just discussed (as well as some of the engine modifications
previously discussed) would also reduce ATV engine durability. There are many engine
improvements that could be made to regain lost durability that occurs with leaner calibration.
These include changes to the cylinder head, pistons, pipes and ports for two-stroke and valves for
four-stroke, to reduce knock. In addition critical engine components could be made more robust
to improve durability.
The same calibration changes to the air/fuel ratio just discussed for carbureted engines
could also be employed, possibly with more accuracy, with the use of fuel injection. At least one
ATV manufacturer currently employs electronic fuel injection on one of its ATV models.
4.4.2.3 Direct and Semi-Direct Fuel Injection
In addition to rich air/fuel ratios, one of the main reasons that two-stroke engines have
such high levels of HC emissions is scavenging losses, as described above. One way to reduce or
eliminate such losses is to inject the fuel into the cylinder after the exhaust port has closed. This
can be done by injecting the fuel into the cylinder through the transfer port (semi-direct injection)
or directly into the cylinder (direct injection). Both of these approaches are currently being used
successfully in two-stroke personal watercraft engines and some are showing upwards of 70
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Chapter 4: Feasibility of Proposed Standards
percent reductions in emissions. Direct injection is also being used by some motorcycle
manufacturers (e.g., Aprilla) on small mopeds, scooters, and motorcycles to meet emission
standards for two-strokes in Europe and Asia. Substantial improvements in fuel economy could
also be expected with these technologies. However, there are some issues with ATV operation
(larger displacement engines that experience more transient operation than watercraft and small
mopeds) that make the application of the direct injection technologies somewhat more
challenging for ATVs than for personal watercraft and small displacement scooters. The biggest
obstacle for this technology is that the many of the two-stroke equipped ATVs are youth models
which emphasize low price. Direct injection is relatively expensive and is currently not
considered to be cost effective for these engines.
4.4.2.4 Four-Stroke Engines
Since 80 percent of all ATVs sold each year are four-stroke, there is no question about the
feasibility of using four-stroke technology for ATVs. The ATV models that are currently
equipped with two-stroke engines tend to be small-displacement youth models, entry-level adult
ATVs and high-performance adult sport ATVs. While most youth ATVs are equipped with two-
stroke engines, there are several manufactures who offer four-stroke models. Youth ATVs are
regulated by the Consumer Product Safety Commission (CPSC). Although the regulations are
voluntary, manufactures take them very seriously, and one of the their requirements is that youth
ATV speeds be governed. For "Y6" ATVs (i.e., age 6 and up) the maximum speed is 15 miles
per hour (mph) and for "Y12" ATVs (i.e., age 12 and up), the maximum speed is 30 mph. Some
manufacturers have argued that because of these speed constraints, they need to use light-weight
two-stroke engines, which have higher power-to-weight ratios than four-stroke engines, in order
to have sufficient power to operate the ATV. As mentioned earlier, some manufacturers already
use four-stroke engines in these applications without any problem. The power required to meet
the maximum speed limits for these little ATVs is low enough that a four-stroke engine is more
than adequate. The real issue appears to be cost. Manufacturers argue that youth ATVs are price
sensitive and that minor increases in cost would be undesirable. Four-stroke engines are more
expensive than similarly powered two-stroke engines. This appears to be the issue with entry-
level adult ATVs as well. Those manufacturers that offer two-stroke entry-level ATVs, also
offer similar entry-level machines with four-stroke engines. The argument is that consumers of
their product like having the ability to choose between engine types.
Adult sport ATVs equipped with two-stroke engines were at one time considered the only
ATVs that were capable of providing true high-performance. However, advancements in four-
stroke engine technology for ATVs and off-highway motorcycles have now made it possible for
larger displacement high-powered four-stroke engines to equal, and in some cases surpass, the
performance of the high-powered two-stroke engines. Again, the argument for two-stroke
engines appears to be a matter of choice for consumers. However, since only two manufacturers
produce two-stroke adult ATVs, we believe that the relatively low sales volumes for these
models will make it cost prohibitive to reduce two-stroke emissions to the levels necessary to
meet our proposed phase I standards.
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Conversion from two-stroke to four-stroke engine technology will also result in
improvements to fuel consumption and engine durability. These benefits could be especially
valuable to
consumers who
purchase utility
ATVs.
4.4.2.5
Air
Injectio
n
A TV HC Emissions
2001 Polaris Sportsman 500
505 Chassis Test Procedure
No Air 20 40 60 80
Air Injection Flow Rate (SCFH)
100
Secondary pulse
air injection
involves the
introduction of fresh air into the exhaust pipe immediately after the gases exit the engine. The
extra air causes further combustion to occur as the gases pass through the exhaust pipe, thereby
controlling more of the hydrocarbons that escape the combustion chamber. This type of system
is relatively inexpensive and uncomplicated because it does not require an air pump; air is drawn
into the exhaust through a one-way reed valve due to the pulses of negative pressure inside the
exhaust pipe. Secondary pulse-air injection is one of the most effective non-catalytic, emissions
control technologies; compared to engines without the system, reductions of 10-40% for HC are
possible with pulse-air injection.
This technology is fairly common on highway motorcycles and is used on some off-
highway motorcycle models in California to meet the California off-highway motorcycle and
ATV emission standards. We believe that secondary air injection will not be necessary to meet
our proposed phase 1 standards, but will be a viable technology for meeting our proposed phase 2
emission standards. Secondary air injection can also be used in conjunction with an oxidation
catalyst to achieve even further reductions. We are planning to test several four-stroke ATVs
with secondary air injection. Initial test results for a 2001 Polaris Sportsman 500 four-stroke
ATV indicate that secondary air injection could result in up to a 70 percent reduction in HC
emissions and a 50 percent reduction in CO emissions from baseline four-stroke ATV emission
levels.
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Chapter 4: Feasibility of Proposed Standards
Figure 4.4-1
ATV HC Emissions
2001 Polaris Sportsman 500
505 Chassis Test Procedure
No Air 20 40 60 80
Air Injection Flow Rate (SCFH)
100
Figure 4.4-2
AW CO Emissions
2001 Polaris Sportsman 500
505 Chassis Test Procedure
/in -,
to
Oon
-— . ""
'53 c
•- •* 20
S(5 20
LU ~
M~\
O 10"
o
1
33.34 i
30.36 I
">fi ->1 l
_ MAb 2163 !
== == 17.95 i
No Air 20 40 60 80 100
Air Injection Flow Rate (SFCH)
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Draft Regulatory Support Document
4.4.2.6 Catalyst Technology
Catalyst technology may be necessary for some ATV models to meet our proposed phase-
2 emission standards. Depending on the model, the respective engine and it's unique
characteristics and the manufacturers preference, manufacturers may choose to use a two-way or
oxidation catalyst or a three-way catalyst. If NOx emissions are inherently low for a given
engine, a manufacturer may decide to use an oxidation catalyst. If high NOx levels are a
concern, the manufacturer may choose to use a three-way catalyst instead. Oxidation catalysts
typically use platinum and/or palladium to oxidize HC and CO emissions. Because some ATV
engines operate so rich, it may be necessary to also use secondary air injection in conjunction
with an oxidation catalyst in order to provide adequate oxygen for oxidation to occur.
Three-way catalytic converters traditionally utilize rhodium and platinum/palladium as
the catalytic material to control the emissions of all three major pollutants (HC, CO, and NOx).
Although this type of catalyst is very effective at converting exhaust pollutants, rhodium, which
is primarily used to reduce NOx to nitrogen and oxygen, tends to thermally deteriorate at
temperatures significantly lower than platinum. Recent advances in palladium and tri-metal (i.e.,
palladium-platinum-rhodium) catalyst technology, however, have improved both the light-off
performance and high temperature durability over previous catalysts. In addition, other
refinements to catalyst technology, such as higher cell density substrates and adding a second
layer of catalyst washcoat to the substrate (dual-layered washcoats), have further improved
catalyst performance from just a few years ago.
Typical cell densities for conventional catalysts used in motorcycles are less than 300
cells per square inch (cpsi). To meet our proposed phase 2 standards, we expect manufacturers
to use catalysts with cell densities of 100 to 200 cpsi. If catalyst volume is maintained at the
same level (we assume volumes of up to 50% of engine displacement), using a higher density
catalyst effectively increases the amount of surface area available for reacting with pollutants.
Catalyst manufacturers have been able to increase cell density by using thinner walls between
each cell without increasing thermal mass (and detrimentally affecting catalyst light-off) or
sacrificing durability and performance.
We have tested a 2001 model year Polaris Sportsman 500 ATV. It is a large utility ATV
equipped with a 500 cc four-stroke engine and is one of the largest ATV models currently offered
in the market. We chose this model to demonstrate catalyst viability because it had the highest
baseline emissions of any of the ATVs we tested, and it is a California certified vehicle that is
sold nationwide. We tested the Polaris with three different catalysts. Two of the catalysts were
three-way catalysts with metal substrates and cell densities of 200 cpsi. One of the catalyst's had
a Pt/Rh washcoat, while the other used a Pd-only washcoat. The third catalyst was an oxidation
catalyst with a ceramic substrate and a cell density of 400 cpsi. Table 4.4-3 shows that the use of
either an oxidation or three-way catalyst can significantly reduce emissions from an ATV. This
particular ATV had baseline HC and CO emissions that were 77% higher for HC and 68% higher
for CO than the average of the baseline levels of all of the ATVs we tested (see above in Table
4.4-1). We measured air/fuel ratio during testing and found this vehicle to operate extremely
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Chapter 4: Feasibility of Proposed Standards
rich. We plan to test the ATV with a leaner carburetor setting and with secondary air injection.
We anticipate that either one or perhaps both of these strategies would result in even further
emission reductions. We also measured exhaust backpressure and found that none of the
catalysts tested resulted in a significant increase in backpressure, which could correspond to
reduced engine performance.
Although the test results for the Polaris did not meet our proposed phase 2 standards, we
are confident that the data illustrate that the use of a catalytic converter can achieve these levels,
since the percent reductions from baseline levels with the catalysts were approximately 52% for
HC and 38% for CO. These levels of reduction when applied to the average baseline emissions
from our test fleet would result in emission levels at or below our proposed phase 2 standards.
Table 4.4-3
Polaris Sportsman 500 Emissions with Various Catalysts
Catalyst
Baseline
TWC (Pd-only)
TWC (Pt/Rh)
Oxidation
HC
2.68
1.27
1.29
1.38
CO
56.50
35.27
32.60
28.87
NOx
0.30
0.05
0.04
0.02
HC+NOx
2.98
1.32
1.33
1.40
Increased precious metal loading (up to a certain point) will reduce exhaust emissions
because it increases the opportunities for pollutants to be converted to harmless constituents.
The extent to which precious metal loading is increased will be dependent upon the precious
metals used and other catalyst design parameters. We believe recent developments in
palladium/rhodium catalysts are very promising since rhodium is very efficient at converting
NOx, and catalyst suppliers have been investigating methods to increase the amount of rhodium
in catalysts for improved NOx conversion.
Double layer technologies allow optimization of each individual precious metal used in
the washcoat. This technology can provide reduction of undesired metal-metal or metal-base
oxide interactions while allowing desirable interactions. Industry studies have shown that
durability and pollutant conversion efficiencies are enhanced with double layer washcoats. These
recent improvements in catalysts can help manufacturers meet the proposed phase 2 standards at
reduced cost relative to older three-way catalysts.
New washcoat formulations are now thermally stable up to 1050 ° C. This is a significant
improvement from conventional washcoats, which are stable only up to about 900 °C. With the
improvements in light-off capability, catalysts may not need to be placed as close to the engine as
previously thought. However, if placement closer to the engine is required for better emission
performance, improved catalysts based on the enhancements described above would be more
capable of surviving the higher temperature environment without deteriorating. The improved
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Draft Regulatory Support Document
resistance to thermal degradation will allow closer placement to the engines where feasible,
thereby providing more heat to the catalyst and allowing them to become effective quickly.
It is well established that a warmed-up catalyst is very effective at converting exhaust
pollutants. Recent tests on advanced catalyst systems in automobiles have shown that over 90%
of emissions during the Federal Test Procedure (FTP) are now emitted during the first two
minutes of testing after engine start up. Similarly, the highest emissions from a motorcycle occur
shortly after start up. Although improvements in catalyst technology have helped reduce catalyst
light-off times, there are several methods to provide additional heat to the catalyst. Retarding the
ignition spark timing and computer-controlled, secondary air injection have been shown to
increase the heat provided to the catalyst, thereby improving its cold-start effectiveness.
Improving insulation of the exhaust system is another method of furnishing heat to the
catalyst. Similar to close-coupled catalysts, the principle behind insulating the exhaust system is
to conserve the heat generated in the engine for aiding catalyst warm-up. Through the use of
laminated thin-wall exhaust pipes, less heat will be lost in the exhaust system, enabling quicker
catalyst light-off. As an added benefit, the use of insulated exhaust pipes will also reduce
exhaust noise. Increasing numbers of manufacturers are expected to utilize air-gap exhaust
manifolds (i.e., manifolds with metal inner and outer walls and an insulating layer of air
sandwiched between them) for further heat conservation for highway motorcycles, although this
may prove to be overkill for ATV applications.
4.4.3 Test Procedure
For ATVs, we propose that the current highway motorcycle test procedure be used for
measuring emissions. The highway motorcycle test procedure is the same test procedure as used
for light-duty vehicles (i.e., passenger cars and trucks) and is referred to as the Federal Test
Procedure (FTP). The FTP for a particular class of engine or equipment is actually the aggregate
of all of the emissions tests that the engine or equipment must meet to be certified. However, the
term FTP has also been used traditionally to refer to the exhaust emission test based on the Urban
Dynamometer Driving Schedule (UDDS), also referred to as the LA4 (Los Angeles Driving
Cycle #4). The UDDS is a chassis dynamometer driving cycle that consists of numerous "hills"
which represent a driving event. Each hill includes accelerations, steady-state operation, and
decelerations. There is an idle between each hill. The FTP consists of a cold start UDDS, a 10
minute soak, and a hot start. The emissions from these three separate events are collected into
three unique bags. Each bag represents one of the events. Bag 1 represents cold transient
operation, bag 2 represents cold stabilized operation, and bag 3 represents hot transient operation.
Highway motorcycles are divided into three classes based on engine displacement, with
class I (50 to 169 cc) being the smallest and class 3 (280 cc and over) being the largest. The
highway motorcycle regulations allow class I motorcycles to be tested on a less severe UDDS
cycle than the class n and HI motorcycles. This is accomplished by reducing the acceleration and
deceleration rates on some the more aggressive "hills." We propose that this same class/cycle
distinction be allowed for ATVs. In other words, ATVs with an engine displacement between 50
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Chapter 4: Feasibility of Proposed Standards
and 279 cc (class I and n) would be tested over the class I highway motorcycle FTP test cycle.
ATVs with engine displacements greater than 280 cc would be tested over the class in highway
motorcycle FTP test cycle. Some manufacturers have noted that they do not currently have
chassis-based test facilities capable of testing ATVs. Manufacturers have noted that requiring
chassis-based testing for ATVs would require them to invest in additional testing facilities which
can handle ATVs, since ATVs do not fit on the same roller(s) as motorcycles used in chassis
testing. Some manufacturers also have stated that low pressure tires on ATVs would not stand
up to the rigors of a chassis dynamometer test. California provides manufacturers with the
option of certifying ATVs using the engine-based, utility engine test procedure (SAE J1088), and
most manufacturers use this option for certifying their ATVs. Manufacturers have facilities to
chassis test motorcycles and therefore California does not provide an engine testing certification
option for motorcycles.
We have tested numerous ATVs over the FTP and have found that several methods can
be used to test ATVs on chassis dynamometers. The most practical method for testing an ATV
on a motorcycle dynamometer is to disconnect one of the drive wheels and test with only one
drive wheel in contact with the dynamometer. For chassis dynamometers set-up to test light-duty
vehicles, wheel spacers or a wide axle can be utilized to make sure the drive wheels fit the width
of the dynamometer. We have found that the low pressure tires have withstood dynamometer
testing without any problems.
We acknowledge that a chassis dynamometer could be very costly to purchase and
difficult to put in place in the short run, especially for some smaller manufacturers. Therefore,
we are proposing that for the model years 2006 thru 2009, ATV manufacturers would be allowed
the option to certify using the J1088 engine test cycle per the California off-highway motorcycle
and ATV program. After 2009, this option would end and the FTP would be the required test
cycle. If manufacturers can develop an alternate transient test cycle (engine or chassis) that
shows correlation with the FTP or demonstrates representativeness of actual ATV operation
greater than the FTP, then we would consider allowing the option of an alternative test cycle in
place of the FTP.
4.4.4 Impacts on Noise, Energy, and Safety
The Clean Air Act directs us to consider potential impacts on noise, energy, and safety
when establishing the feasibility of emission standards for nonroad engines.
As automotive technology demonstrates, achieving low emissions from spark-ignition
engines can correspond with greatly reduced noise levels. Virtually all ATVs are equipped sound
suppression systems or mufflers. The four-stroke engines used in ATVs are considerably more
quiet than two-stroke engines. Electronically controlled fuel systems are able to improve
management of the combustion event which can further help lower noise levels.
Adopting new technologies for controlling fuel metering and air-fuel mixing will lead to
substantial improvements in fuel consumption rates for four-stroke engines. Four-stroke engines
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Draft Regulatory Support Document
have far less fuel consumption than two-stroke engines. Average mileage for a baseline two-
stroke ATV is 20-25 mpg, while the average four-stroke ATV gets 45-50 mpg.
We believe the technology discussed here would have no negative impacts on safety.
Four-stroke engine technology has been utilized on ATVs for numerous years without any
incident. Secondary air and catalysts have been utilized in highway motorcycles and lawn and
garden equipment without any safety concerns.
4.4.5 Conclusion
We expect that the proposed phase 1 ATV emission standards will largely be met through
the conversion of two-stroke engines to four-stroke engines with some minor carburetor
calibration modifications and air-fuel ratio enleanment. Certification data from California's off-
highway motorcycle and ATV program, as well as data from our own testing suggest that four-
stroke engines with some minor fuel system calibration modifications will be capable of meeting
our proposed emission standards. For our proposed phase 2 ATV emission standards, we expect
manufacturers to use four-stroke engine technology with a possible combination of engine
modifications, carburetion improvements, secondary air injection and/or catalyst aftertreatment.
These technologies have been utilized in a number of different applications, such as highway
motorcycles, personal watercraft, lawn and garden equipment, and small scooters. Preliminary
testing performed by us and other research firms have also shown that these are viable
technologies capable of meeting our proposed phase 2 standards. However, the other
technologies discussed have the potential to reduce emissions beyond what could be expected
from engine modifications and carburetion improvements. These other technologies also have
potential benefits beyond emission reductions (e.g., improved fuel economy, reliability and
performance, and reduced noise). We expect that as ATV manufacturers develop and refine
these other technologies, they will find their way into the marketplace in certain applications
where their non-emission benefits would outweigh their cost.
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Chapter 4: Feasibility of Proposed Standards
4.7 Off-Highway Motorcycles
The following paragraphs summarize the data and rationale supporting the proposed
emission standards for off-highway motorcycles, which are listed in the Executive Summary.
4.7.1 Baseline Technology and Emissions
Off-highway motorcycles are similar in appearance to highway motorcycles (which are
discussed in section 4.8.), but there are several important distinctions between the two types of
machines. Off-highway motorcycles are not street-legal and are primarily operated on public and
private lands over trails and open land. Off-highway motorcycles tend to be much smaller,
lighter and more maneuverable than their larger highway counterparts. They are equipped with
relatively small-displacement single- cylinder two- or four-stroke engines ranging from 50 to 650
cubic centimeters (cc). The exhaust systems for off-highway motorcycles are distinctively
routed high on the frame to prevent damage from brush, rocks, and water. Off-highway
motorcycles are designed to be operated over varying surfaces, such as dirt, sand, and mud, and
are equipped with knobby tires which provide better traction in off-road conditions. Unlike
highway motorcycles, off-highway motorcycles have fenders mounted far from the wheels and
closer to the rider to keep dirt and mud from spraying the rider and clogging between the fender
and tire. Off-highway motorcycles are also equipped with a more advanced suspension system
than those for highway motorcycles. This allows the operator to ride over obstacles and make
jumps safely.
Thirty percent of off-highway motorcycle sales are competition motorcycles. The vast
majority of competition off-highway motorcycles are two-strokes. The CAA requires us to
exempt from our regulations vehicles used for competition purposes. The off-highway
motorcycles that remain once competition bikes are excluded are recreational trail bikes and
small-displacement youth bikes. The majority of recreational trail bikes are equipped with four-
stroke engines. Youth off-highway motorcycles are almost evenly divided between four-stroke
and two-stroke engines.
The fuel system used on off-highway motorcycles, whether two- or four-stroke, are
almost exclusively carburetors, although at least one manufacturer has introduced a four-stroke
off-highway motorcycle with electronic fuel injection. Although many off-highway motorcycles
are four-stroke equipped, they still can have relatively high levels of HC and extremely high
levels of CO, because many of them operate with a "rich" air and fuel mixture, which enhances
performance and allows engine cooling which promotes longer lasting engine life. This is also
true for two-stroke equipped off-highway motorcycles. Rich operation results in high levels of
HC, CO, and PM emissions. In addition, two-stroke engines lubricate the piston and crankshaft
by mixing oil with the air and fuel mixture. This is accomplished by most contemporary two-
stroke engines with a pump that sends two-cycle oil from a separate oil reserve to the carburetor
where it is mixed with the air and fuel mixture. Some less expensive two-stroke engines require
that the oil be mixed with the gasoline in the fuel tank. Because two-stroke engines tend to have
high scavenging losses, where up to a third of the unburned air and fuel mixture goes out of the
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exhaust, lubricating oil particles are also released into the atmosphere, becoming HC particles or
particulate matter (PM). The scavenging losses also result in high levels of raw HC. This is in
contrast to four-stroke engines that use the crankcase as an oil sump and a pump to distribute oil
throughout the engine, resulting in virtually no PM.
We tested six high-performance two-stroke motorcycles and four high-performance four-
stroke motorcycles over the FTP. Tables 4.7-1 and 4.7-2 shows that the HC emissions for the
four-stroke bikes is significantly lower than for the two-stroke bikes, whereas the NOx emissions
from the two-strokes were considerably lower. The CO levels were also considerably lower for
the four-stroke bikes.
Table 4.7-1
Four-Stroke Off-Highway Motorcycles Emissions (g/km)
Make
Yamaha
Yamah
KTM
Husaberg
Model
WR250F
WR400F
400EXC
FE501
Model
Year
2001
1999
2001
2001
Eng. Displ.
249 cc
398 cc
398 cc
498 cc
Average
HC
1.46
1.07
1.17
1.30
1.25
CO
26.74
20.95
28.61
25.81
25.52
NOx
0.110
0.155
0.050
0..163
0.109
Table 4.7-2
Two-Stroke Off-Highway Motorcycles Emissions (g/km)
Make
KTM
KTM
KTM
KTM
KTM
KTM
Model
125SX
125SX
200EXC
250SX
250EXC
300EXC
Model
Year
2001
2001
2001
2001
2001
2001
Eng. Displ.
124 cc
124 cc
198 cc
249 cc
249 cc
398 cc
Average
HC
33.77
61.41
53.09
62.89
59.13
47.39
52.95
CO
31.00
32.43
39.89
49.29
40.54
45.29
39.74
NOx
0.008
0.011
0.025
0.011
0.016
0.012
0.060
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Chapter 4: Feasibility of Proposed Standards
4.7.2 Potentially Available Off-Highway Motorcycle Technologies
A variety of technologies are currently available or in stages of development to be
available for use on two-stroke off-highway motorcycles, such as engine modifications,
improvements to carburetion (improved fuel control and atomization, as well as improved
production tolerances), enleanment strategies for both carbureted and fuel injected engines, and
semi-direct and direct fuel injection. However, it is our belief that manufacturers will choose to
convert their two-stroke engines to four-stroke applications, because of the cost and complexity
of the above mentioned technologies necessary to make a two-stroke engine meet our proposed
standards. For our proposed standards, we believe that a four-stroke engine with minor
improvements to carburetion and enleanment strategies will be all that is required. Each of these
is discussed in the following sections.
4.7.2.1 Engine Modifications
There are a variety of engine modifications that could reduce emissions from two-stroke
and four-stroke engines. The modifications generally either increase trapping efficiency (i.e.,
reduce fuel short-circuiting) or improve combustion efficiency. Those modifications for two-
stroke engines that increase trapping efficiency include optimizing the intake, scavenge and
exhaust port shape and size, and port placement, as well as optimizing port exhaust tuning and
bore/stroke ratios. Optimized combustion charge swirl, squish and tumble would serve to
improve the combustion of the intake charge for both two- and four-stroke engines. These
modifications for two-stroke engines have the potential to reduce emissions by up to 40 percent,
depending on how well the unmodified engine is optimized for these things, but would be
insufficient alone to meet our proposed standards.
4.7.2.2 Carburetion Improvements
There are several things that can be done to improve carburetion in off-highway
motorcycle engines. First, strategies to improve fuel atomization would promote more complete
combustion of the fuel/air mixture. Additionally, production tolerances could be improved for
more consistent fuel metering. Both of these things would allow for more accurate control of the
air/fuel ratio. In conjunction with these improvements in carburetion, the air/fuel ratio could be
leaned out some. Off-highway motorcycle engines are currently calibrated with rich air/fuel
ratios for durability and performance reasons. Leaner calibrations would serve to reduce CO and
HC emissions by up to 20 percent, depending on how lean the unmodified engine is prior to
recalibration. Small improvements in fuel economy could also be expected with recalibration.
The calibration changes just discussed (as well as some of the engine modifications
previously discussed) would also reduce off-highway motorcycle engine durability. There are
many engine improvements that could be made to regain lost durability that occurs with leaner
calibration. These include changes to the cylinder head, pistons, pipes and ports for two-stroke
and valves for four-stroke, to reduce knock. In addition critical engine components could be
made more robust to improve durability.
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Carburetion improvements alone will not allow manufacturers to meet our proposed
standards, especially for two-stroke engines. Carburetion improvements with four-stroke engines
may be necessary.
The same calibration changes to the air/fuel ratio just discussed for carbureted engines
could also be employed, possibly with more accuracy, with the use of fuel injection. At least one
off-highway motorcycle manufacturer currently employs electronic fuel injection on one of its
models.
4.7.2.3 Direct and Semi-Direct Fuel Injection
In addition to rich air/fuel ratios, one of the main reasons that two-stroke engines have
such high levels of HC emissions is scavenging losses, as described above. One way to reduce or
eliminate such losses is to inject the fuel into the cylinder after the exhaust port has closed. This
can be done by injecting the fuel into the cylinder through the transfer port (semi-direct injection)
or directly into the cylinder (direct injection). Both of these approaches are currently being used
successfully in two-stroke personal watercraft engines and some are showing upwards of 70
percent reductions in emissions. Direct injection is also being used by some motorcycle
manufacturers (e.g., Aprilla) on small mopeds, scooters, and motorcycles to meet emission
standards for two-strokes in Europe and Asia. Substantial improvements in fuel economy could
also be expected with these technologies. However, there are some issues with off-highway
motorcycle operation (larger displacement engines that experience more transient operation than
watercraft and small mopeds) that make the application of the direct injection technologies
somewhat more challenging for motorcycles than for personal watercraft and small displacement
scooters. The biggest obstacle for this technology is that the many of the two-stroke equipped
off-highway motorcycles are youth models which emphasize low price. Direct injection is
relatively expensive and is currently not considered to be cost effective for these engines.
4.7.2.4 Four-Stroke Engines
We expect that the conversion of off-highway motorcycle models utilizing two-stroke
engines to four-stroke engines will be the main method of achieving our proposed off-highway
motorcycle standards. As with ATVs, the question of feasibility for four-stroke engines in off-
highway motorcycles is moot, since more than half of the existing off-highway models are
already four-stroke and, in some cases, have been for a long time. Honda has used four-stroke
engines in all of their off-highway motorcycles (except for their competition motocross bikes) for
over thirty years. In fact, over the last 5 to 10 years, the trend has been to slowly replace two-
stroke models with four-stroke engines. Although the California emission standards have had
some impact on this, it has been minor. Four-stroke engines are more durable, reliable, quieter
and get far better fuel economy than two-stroke engines. But probably the single most important
factor in the spread of the four-stroke engine has been major advances in weight reduction and
performance.
Four-stroke engines typically weigh more than two-stroke engines because they need a
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Chapter 4: Feasibility of Proposed Standards
valve-train system, consisting of intake and exhaust valves, camshafts, valve springs, valve
timing chains and other components, as well as storing lubricating oil in the crankcase. Since a
four-stroke engine produces a power-stroke once every four revolutions of the crankshaft,
compared to a two-stroke which produces one once every two revolutions, a four-stroke engine
of equal displacement to a two-stroke engine produces less power, on the average of 30 percent
less. So in the past, off-highway motorcycles that used four-stroke engines tended to use very
heavy, large displacement engines, but yet had average power and performance. However, recent
breakthroughs in technologies have allowed manufacturers to design off-highway motorcycles
that use lighter and stronger materials for the engine and the motorcycle frame. The advanced
four-stroke technologies, such as multiple valves, used in some of the high-performance four-
stroke highway motorcycles, have found their way onto off-highway motorcycles, resulting in
vastly improved performance. The newer four-stroke bikes also tend to have an engine power
band or range that is milder of more forgiving than a typical two-stroke bike. Two-stroke bikes
tend to run poorly at idle and during low load situations. They also typically generate low levels
of torque at low to medium speeds, whereas four-stroke bikes traditionally generate a great deal
of low-end and mid-range torque. This is important to off-highway motorcycle riders because it
is common when riding off-highway motorcycles on trails or other surfaces to come across
obstacles that require slower maneuverability. A two-stroke engine that idles poorly and has
poor low-end torque can easily stall during these maneuvers, whereas a four-stroke bike excels
under these conditions. Current sales figures, as well as articles in off-highway motorcycle trade
magazines, indicate that four-stroke off-highway motorcycles are more popular than ever, and the
public is buying them as fast as they can build them.
4.7.2.5 Air Injection
Secondary pulse air injection involves the introduction of fresh air into the exhaust pipe
immediately after the gases exit the engine. The extra air causes further combustion to occur as
the gases pass through the exhaust pipe, thereby controlling more of the hydrocarbons that escape
the combustion chamber. This type of system is relatively inexpensive and uncomplicated
because it does not require an air pump; air is drawn into the exhaust through a one-way reed
valve due to the pulses of negative pressure inside the exhaust pipe. Secondary pulse-air
injection is one of the most effective non-catalytic, emissions control technologies; compared to
engines without the system, reductions of 10-40% for HC are possible with pulse-air injection.
This technology is fairly common on highway motorcycles and is used on some off-
highway motorcycle models in California to meet the California off-highway motorcycle and
ATV emission standards. We believe that secondary air injection should not be necessary to
meet our proposed standards, however, some manufacturers may choose to use it on some four-
stroke engine models.
4.7.3 Test Procedure
For off-highway motorcycles, we propose that the current highway motorcycle test
procedure be used for measuring emissions. The highway motorcycle test procedure is the same
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test procedure as used for light-duty vehicles (i.e., passenger cars and trucks) and is referred to as
the Federal Test Procedure (FTP). The FTP for a particular class of engine or equipment is
actually the aggregate of all of the emissions tests that the engine or equipment must meet to be
certified. However, the term FTP has also been used traditionally to refer to the exhaust
emission test based on the Urban Dynamometer Driving Schedule (UDDS), also referred to as
the LA4 (Los Angeles Driving Cycle #4). The UDDS is a chassis dynamometer driving cycle
that consists of numerous "hills" which represent a driving event. Each hill includes
accelerations, steady-state operation, and decelerations. There is an idle between each hill. The
FTP consists of a cold start UDDS, a 10 minute soak, and a hot start. The emissions from these
three separate events are collected into three unique bags. Each bag represents one of the events.
Bag 1 represents cold transient operation, bag 2 represents cold stabilized operation, and bag 3
represents hot transient operation.
Highway motorcycles are divided into three classes based on engine displacement, with
class I (50 to 169 cc) being the smallest and class 3 (280 cc and over) being the largest. The
highway motorcycle regulations allow class I motorcycles to be tested on a less severe UDDS
cycle than the class n and HI motorcycles. This is accomplished by reducing the acceleration and
deceleration rates on some the more aggressive "hills." We propose that this same class/cycle
distinction be allowed for off-highway motorcycles. In other words, off-highway motorcycles
with an engine displacement between 50 and 279 cc (class I and II) would be tested over the class
I highway motorcycle FTP test cycle. Off-highway motorcycles with engine displacements
greater than 280 cc would be tested over the class HI highway motorcycle FTP test cycle.
4.7.4 Impacts on Noise, Energy, and Safety
The Clean Air Act directs us to consider potential impacts on noise, energy, and safety
when establishing the feasibility of emission standards for nonroad engines.
As automotive technology demonstrates, achieving low emissions from spark-ignition
engines can correspond with greatly reduced noise levels. Virtually all recreational off-highway
motorcycles are equipped with sound suppression systems or mufflers. The four-stroke engines
used in off-highway motorcycles are considerably more quiet than the two-stroke engines used.
Adopting new technologies for controlling fuel metering and air-fuel mixing will lead to
substantial improvements in fuel consumption rates for four-stroke engines. Four-stroke engines
have far less fuel consumption than two-stroke engines. Average mileage for a baseline two-
stroke off-highway motorcycle is 20-25 mpg, while the average four-stroke off-highway
motorcycle gets 45-50 mpg.
We believe the technology discussed here would have no negative impacts on safety.
Four-stroke engine technology has been utilized on off-highway motocycles for numerous years
without any incident. Secondary air and catalysts have been utilized in highway motorcycles and
lawn and garden equipment without any safety concerns.
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Chapter 4: Feasibility of Proposed Standards
4.7.5 Conclusion
We expect that the proposed off-highway motorcycle emission standards will largely be
met through the conversion of two-stroke engines to four-stroke engines with some minor
carburetor calibration modifications and air-fuel ratio enleanment. Four-stroke engines are
common in many off-highway motorcycles and have been used for many years. Certification
data from California's off-highway program, as well as data from our own testing suggest that
four-stroke engines with some minor fuel system calibration modifications will be capable of
meeting our proposed emission standards. We believe the current sales volumes of two-stroke
off-highway motorcycles, combined with the cost to modify two-stroke engines for significant
emission reductions, will discourage the use of two-stroke engine technology.
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Chapter 4 References
1. "Emission Testing of Nonroad Compression Ignition Engines," prepared by Southwest
Research Institute for the U.S. EPA, SwRI 6886-802, September 1995, Docket A-2000-01,
Document U-A-20.
2. Memorandum from Mike Brand, Cummins, to Bill Charmley, U.S. EPA, "Draft Report on
Emission Testing of Nonroad Compression Ignition Engines" November 13, 1995, Docket A-
2000-01, Document II-A-22.
3. Letter from Jeff Carmody, Santa Barbara County Air Pollution Control District, to Mike
Samulski, U.S. EPA, "Marine Engine Replacement Programs," July 21, 1997, Docket A-2000-
01, Document U-A-21.
4. Facsimile from Eric Peterson, Santa Barbara County Air Pollution Control District, to Mike
Samulski, U.S. EPA, "Data on Mercury 4.2 and 2.8 Liter Engines," April 1, 1998, Docket A-
2000-01, Document II-A-24.
5. Smith, M., "Marine Diesel Engine Testing," Prepared by Southwest Research Institute for the
U.S. EPA, Contract # 68-C-98-169, WA 0-7, September 1999, Docket A-2000-01, Document II-
A-26.
6. Data Submission by the Engine Manufacturers Association, July 19, 2000, Docket A-2000-
01, Document H-B-11.
7. International Organization for Standardization, 8178-4, "Reciprocating internal combustion
engines—Exhaust emission measurement—Part 4: Test cycles for different engine applications,"
Docket A-2000-01, Document II-A-19.
8. Wilbur, C., "Marine Diesel Engines," Butterworth & Heinemann Ltd, 1984.
9. "Data Collection and Analysis of Real-World Marine Diesel Transient Duty-Cycles," EPA
memo from Matt Spears to Mike Samulski, October 15, 1999, Docket A-2000-01, Document U-
B-09.
10. Memorandum from Mark Wolcott to Charles Gray, "Ambient Temperatures Associated with
High Ozone Concentrations," U.S. Environmental Protection Agency, September 6, 1984,
Docket A-2000-01, Document U-B-06.
11. Smith, M., "Marine Diesel Engine Testing," Prepared by Southwest Research Institute for
the U.S. EPA, Contract # 68-C-98-169, WA 0-7, September 1999, Docket A-2000-01,
Document U-A-26.
12. SAE J1937 (reaffirmed JAN1995), "Engine Testing with Low-Temperature Charge Air-
Cooler Systems in a Dynamometer Test Cell," SAE Recommended Practice, Docket A-2000-01,
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Chapter 4: Feasibility of Proposed Standards
Document II-A-62.
13. Annex VI of MARPOL 73/78, "Technical code of control of Emissions of Nitrogen Oxides
for Marine Diesel Engines," October 22, 1997, Docket A-2000-01, Document U-A-25.
14. "Emission Data and Procedures for Large SI Engines," EPA memorandum from Alan Stout
and Chuck Moulis to Docket A-2000-01, January 2, 2001, EPA420-F-00-050, Document H-B-
05.
15. The Mazda and GM engines are from SwRI 2000; Engine B and Engine E are from SwRI
1999.
16."Durability Experience with Electronic Controlled CNG and LPG Engines," A. Lawson et al.,
February 2, 2000, Docket A-2000-01, Document U-D-2.
17."Exhaust Controls Available to Reduce Emissions from Nonroad Heavy-Duty Engines," by
Kevin Brown, Engine Control Systems, in Clean Air Technology News., Winter 1997, Docket A-
2000-01, Document II-A-2.
18. "Case Study: The Results of EVIPCO's GM 3.0 liter Certified Engine Program," presented by
Josh Pietak, February 2, 2000, A-2000-01, Document II-D-11.
19. See SwRI report for a further description of the catalyst damage observed.
20."Emission Modeling for Recreational Vehicles," EPA memorandum from Line Wehrly to
Docket A-98-01, November 13, 2000, Document IV-B-06.
21. "Development and Validation of a Snowmobile Engine Emission Test Procedure," Jeff J.
White, Southwest Research Institute and Christopher W. Wright, Arctic Cat, Inc., SAE paper
982017, September, 1998, Docket A-2000-01, Document U-A-66.
22. 61 FR 52088, October 4, 1996.
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Chapter 5: Estimated Costs
CHAPTER 5: Estimated Costs
This chapter describes our approach to estimating the cost of complying with emission
standards. We start with a general description of the approach to estimating costs, then describe
the technology changes we expect and assign costs to them. We also present an analysis of the
estimated aggregate cost to society.
5.1 Methodology
We developed the costs for individual technologies using information provided by ICF,
Incorporated and Arthur D. Little, as cited below. The technology characterization and cost
figures reflect our current best judgment based on engineering analysis, information from
manufacturers, and the published literature. The analysis combines cost figures including
markups to the retail level.
Costs of control include variable costs (for incremental hardware costs, assembly costs,
and associated markups) and fixed costs (for tooling, R&D, and certification). Variable costs are
marked up at a rate of 29 percent to account for the engine manufacturers' overhead and profit.1
For technologies sold by a supplier to the engine manufacturers, an additional 29 percent markup
is included for the supplier's overhead and profit. All costs are in 2001 dollars.
The analysis presents an estimate of costs that would apply in the first year of new
emission standards and the corresponding long-term costs. Long-term costs decrease due to two
principal factors. First, fixed costs are assessed for five years, after which they are fully
amortized and are therefore no longer part of the cost calculation. Second, manufacturers are
expected to learn over time to produce the engines with the new technologies at a lower cost.
Because of relatively low sales volumes, manufacturers are less likely to put in the extra R&D
effort for low-cost manufacturing. As production starts, assemblers and production engineers
will then be expected to find significant improvements in fine-tuning the designs and production
processes. Consistent with analyses from other programs, we reduce estimated variable costs by
20 percent beginning with the third year of production and an additional 20 percent beginning
with the sixth year of production.2 We believe it is appropriate to apply this factor here, given
that the industries are facing emission regulations for the first time and it is reasonable to expect
learning to occur with the experience of producing and improving emission-control technologies.
Many of the engine technologies available to manufacturers to control emissions also
have the potential to significantly improve engine performance. This is clear from the
improvements in automotive technologies. As cars have continually improved emission controls,
they have also greatly improved fuel economy, reliability, power, and a reduced reliance on
regular maintenance. Similarly, the fuel economy improvements associated with converting from
two-stroke to four-stroke engines is well understood. We attempt to quantify these expected
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Draft Regulatory Support Document
improvements, as we describe for each type of engine below.
Even though the analysis does not reflect all the possible technology variations and
options that are available to manufacturers, we believe the projections presented here provide a
cost estimate representative of the different approaches manufacturers may ultimately take. We
expect manufacturers in many cases to find and develop approaches to achieve the emission
standards at a lower cost than we describe in this analysis.
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Chapter 5: Estimated Costs
5.2 Cost of Emission Controls by Engine/Vehicle Type
5.2.1 Recreational Marine Diesel Engines
We have developed cost estimates for diesel engine technologies for several different
applications in a series of reports.3'4'5 This analysis adapts these existing cost estimates for
recreational marine diesel engines with separate estimates for three different sizes of engines.
Recreational marine diesel engines invariably have counterpart engine models used for
commercial application. Manufacturers will design, certify, and manufacture these commercial
models to meet emission standards. The analysis projects that manufacturers will comply with
the new emission standards generally by applying the same technologies for both commercial and
recreational engines. The remaining effort to meet emission standards with the recreational
models would be limited to applying new or improved hardware and conducting sufficient R&D
to integrate the new technologies into marketable products. The analysis therefore does not
consider fixed costs to develop the individual technologies separately.
One area where recreational engine designs differ is in turbocharging and aftercooling.
To reach peak performance, recreational engines typically already use optimized turbochargers
and seawater aftercooling, which offer the greatest potential for controlling NOx emissions.
We estimate the total cost impact of new emission standards by considering the cost of
each of the anticipated technologies. The following paragraphs describe these technologies and
their application to recreational marine engines. The analysis then combines these itemized costs
into a composite estimate for the range of marine engines affected by the rulemaking.
Table 5.2.1-1 also includes information on product offerings and sales volumes, which is
needed to calculate amortized fixed costs for individual engines. Estimated sales and product
offerings were compiled from the PSR database based on historical 1997 information.
Table 5.2.1-1
Recreational Marine Diesel Engine Categories for Estimating Costs
Engine
Power
Ranges (kW)
37 - 225
225 - 560
560 +
Nominal
Engine Power
(kW)
100
400
750
Annual
Sales
3,700
6,700
1,000
Models
17
15
6
Average Sales
per Model
216
448
173
Manufacturers are expected to develop engine technologies not only to reduce emissions,
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Draft Regulatory Support Document
but also to improve engine performance. While it is difficult to take into account the effect of
ongoing technology development, EPA is concerned that assessing the full cost of the anticipated
technologies as an impact of new emission standards would inappropriately exclude from
consideration the expected benefits for engine performance, fuel consumption, and durability.1
Short of having sufficient data to predict the future with a reasonable degree of confidence, we
face the need to devise an alternate approach to quantifying the true impact of the new emission
standards. As an attempt to take this into account, we present the full cost of the control
technologies in this chapter, then apply a discount to some of these costs for calculating the cost-
per-ton of the proposed emission standards, as described in Chapter 7.
5.2.1.1 Fuel Injection Improvements
All engines are expected to see significant improvements in their fuel injection systems.
The smaller engines will likely undergo incremental improvements to existing unit injector
designs. The analysis projects that engines rated over 600 kW will use common rail injection
technology, which greatly increases the flexibility of tailoring the injection timing and profile to
varying modes of operation. Better control of injection timing and increased injection pressure
contribute to reduced emissions. Table 5.2.1-2 shows the estimated costs for these fuel injection
improvements.
Table 5.2.1-2
Fuel Injection Improvements
Component costs
Assembly, markup, and warranty
Composite Unit Cost
lOOkW
$63
$32
$95
400 kW
$98
$46
$144
750 kW
$205
$59
$264
5.2.1.2 Engine Modifications
Manufacturers will be optimizing basic engine parameters to control emissions while
maintaining performance. Such variables include routing of the intake air, piston crown
geometry, and placement and orientation of injectors and valves. Most of these variables affect
the mixing of air and fuel in the combustion chamber. Small changes in injection timing are also
considered in this set of modifications. We expect, however, that manufacturers will complete
this work for commercial marine diesel engines, so that the remaining effort will be focused on
fine-tuning designs for turbocharger matching and other calibration-related changes. Fixed costs
are amortized over a five-year period, using the sales volumes developed in Table 5.2.1-1, with
'While EPA does not anticipate widespread, marked improvements in fuel consumption,
small improvements on some engines may occur.
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Chapter 5: Estimated Costs
forward discounting incorporated to account for manufacturers incurring these costs before the
emission standards begin to apply. Table 5.2.1-3 shows the estimated per-engine costs for these
modifications. These costs include the consideration manufacturers must give to offsetting any
crankcase emissions routed to the exhaust. There is no estimated long-term cost to the engine
modifications because manufacturers can fully recover the fixed costs, and we don't expect any
increase in variable costs as a result of these improvements.
Table 5.2.1-3
Engine Modifications
Total fixed costs
Fixed cost per engine
Composite Unit Cost
100 kW
$200,000
$244
$244
400 kW
$200,000
$122
$122
750 kW
$200,000
$244
$244
5.2.1.3 Certification and Compliance
We have significantly reduced certification requirements in recent years, but
manufacturers are nevertheless responsible for generating a minimum amount of test data and
other information to demonstrate compliance with emission standards. Table 5.2.1-4 lists the
expected costs for different sizes of engines, including the amortization of those costs over five
years of engine sales. Estimated certification costs are based on two engine tests and $10,000
worth of engineering and clerical effort to prepare and submit the required information.
Until engine designs are significantly changed, engine families can be recertified each
year using carryover of the original test data. Since these engines are currently not subject to any
emission requirements, the analysis includes a cost to recertify an upgraded engine model every
five years.
Costs for production line testing are summarized in Table 5.2.1-5. These costs are based
on testing 1 percent of total estimated sales, then distributing costs over the fleet. Listed costs for
engine testing presume no need to build new test facilities, since we are proposing to waive
production-line testing requirements for small-volume production. Few manufacturers, if any,
will therefore need to build new test facilities.
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Table 5.2.1-4
Certification
Total fixed costs
Fixed cost per engine
Composite Unit Cost
100 kW
$30,000
$77
$37
400 kW
$30,000
$93
$18
750 kW
$40,000
$859
$49
Table 5.2.1-5
Costs for Production Line Testing
Cost per test
Testing rate
Cost per engine
100 kW
$10,000
1%
$100
400 kW
$10,000
1%
$100
750 kW
$15,000
1%
$150
5.2.1.4 Total Engine Costs
These individual cost elements can be combined into a calculated total for new emission
standards by assessing the degree to which the different technologies will be deployed. As
shown in Table 5.2.1-6, estimated costs for complying with the proposed emission standards
increase with increasing power ratings. We expect each of the listed technologies to apply to all
the engines that need to meet the new emission standards. Estimated price impacts range from
$400 to $700 for the different engine sizes.
Characterizing these estimated costs in the context of their fraction of the total purchase
price and life-cycle operating costs is helpful in gauging the economic impact of the new
standards. The estimated first-year cost increases for all engines are at most 2 percent of
estimated engine prices, with even lower long-term effects, as described above.
Table 5.2.1-6
Diesel Engine Costs
Fuel injection upgrade
Engine modifications
Certification + PLT
Total Engine Cost
100 kW
$95
$244
$137
$475
400 kW
$144
$122
$118
$384
750 kW
$264
$244
$199
$707
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Chapter 5: Estimated Costs
5.2.1.5 CI Marine Aggregate Costs
The above analyses developed incremental per-vessel cost recreational marine diesel
engines. Using these per-engine costs and projections of future annual sales, we have estimated
total aggregate annual costs for proposed emission standards. The aggregate costs are presented
on a cash-flow basis, with hardware and fixed costs incurred in the year the vehicle is sold.
Table 5.2.1-7 presents a summary of this analysis. As shown in the table, aggregate net costs
stay between $2 million and $4 million.
Table 5.2.1.-7
Summary of Annual Aggregate Costs for Marine CI Engines (millions of dollars)
Total Costs
2006
$3.0
2010
$3.7
2015
$2.2
2020
$2.5
2025
$2.7
To project annual sales, we started with the 1998 population estimates presented in
Chapter 6. We then used the engine turnover rates and growth estimates to calculate annual
sales. Table 5.2.1.-8 provides a summary of the sales estimates used in the aggregate cost
analysis.
Table 5.2.1.-8
Estimated Annual Sales of Recreational Marine Diesel Engines
Engine Power Range (kW)
37 - 225
225 - 560
560 +
1999
5,160
1,580
180
2006
6,330
1,900
220
2010
7,000
2,140
240
2020
8,700
2,660
300
To calculated annual aggregate costs, the sales estimates have been multiplied by the per-
unit costs discussed above. These calculations take into consideration vehicle sales and
scrappage rates. The year-by-year results of the analysis are provided in Chapter 7.
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5.2.2 Large Industrial Spark-Ignition Engines
We estimated the cost of upgrading LPG-fueled and gasoline-fueled and gasoline-fueled
Large SI engines. We developed the costs for individual technologies in cooperation with ICF,
Incorporated and Arthur D. Little.6 The analysis combines these individual figures into a total
estimated cost for each type of engine, including markups to the retail level. A composite cost
based on the mix of engine types provides an estimated industry-wide estimate of the per-engine
cost impact.
Gasoline-fueled Large SI engines continue to rely on traditional carburetor designs rather
than incorporating the automotive technology innovations introduced to address emission
controls. Since natural gas- and LPG-fueled engines use comparable technologies, the analysis
presents a single set of costs for both fuels.
The anticipated technology development is generally an outgrowth of automotive
technologies. Over the last thirty years, engineers in the automotive industry have made great
strides in developing new and improved approaches to achieve dramatic emission reductions
with high-performing engines. In more recent years, companies have started to offer these same
technologies for industrial applications. Fundamental to this technology development is the
electronically controlled fuel system and catalytic converters.
Electronically controlled fuel systems allow manufacturers to more carefully meter fuel
into the combustion chambers. This gives the design engineer an important tool to better control
power and emission characteristics over the whole range of engine operation. Careful control of
air-fuel ratio is also essential for effective catalyst conversion. The catalyst converts the
pollutants in the exhaust stream to harmless gases. We also consider development time to
redesign the combustion chamber and intake air routing, as well as to combine the new control
technologies and optimize engine calibrations. We include these efforts under the total R&D
costs for each engine.
Gasoline engines can use either throttle-body or port-fuel injection. Manufacturers can
likely reach the targeted emission levels using simpler throttle-body systems. However, the
performance advantages and the extra assurance for full-life emission control from the more
advanced port-fuel injection systems offer a compelling advantage. The analysis therefore
projects that all gasoline engines will use port-fuel injection. The analysis does not take into
account the performance advantages of port-fuel injection and therefore somewhat overestimates
the cost impact of adopting new emission standards.
Gaseous-fuel engines have very different fuel metering systems due to the fact that LPG
and natural gas evaporate readily at typical ambient temperatures and pressures. Manufacturers
of these engines face a choice between continuing with conventional mixer technology and
upgrading to injection systems. We are aware that manufacturers are researching gaseous
injection systems, but we believe mixer technology will be sufficient to meet the proposed
standards. All the data supporting the feasibility of emission standards for LPG engines is based
5-8
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Chapter 5: Estimated Costs
on engines using mixer technology.
5.2.2.1 Engine Technology
Tables 5.2.2-1 and 5.2.2-2 show the estimated costs of upgrading each of the engine
types. The cost figures are in the form of retail-price equivalent for an individual engine. The
tables include individual cost estimates of the various components involved in converting a
baseline engine to comply with emission standards. The cost of the catalyst is based on a
precious metal loading of 2.8 g/liter (primarily palladium, with small amounts of platinum and
rhodium) and a catalyst volume 60 percent of total engine displacement.
The analysis incorporates a cost for potential warranty claims related to the new
technologies by adding 5 percent of the increase in hardware costs. The industry has gained
enough experience with electronic fuel systems that we expect a relatively low rate of warranty
claims for them. Catalysts have been used for many years, but not in Large SI applications, so
these technologies may cause a somewhat higher rate of warranty claims.
Even without EPA emission standards, manufacturers will conduct the research and
development needed to meet the 2004 emission standards in California. The R&D impact of new
EPA standards is therefore limited to the additional burden of complying with the proposed 2007
requirements. Estimated costs for research and development are $175,000 for each engine
family. This is based on about six months of time for an engineer and a technician on each fuel
type for each engine family. We would expect initial efforts to require greater efforts, but
cumulative learning would reduce per-family development costs for subsequent models. These
fixed costs are increased by 7 percent to account for forward discounting, since manufacturers
incur these costs before the new standards apply. Redesigning the first engine model will likely
require significantly more time than this, but we expect the estimated level of R&D to be
appropriate as an average level for the range of models in a manufacturer's product line.
While there is no separate item in the following cost tables for positive-crankcase
ventilation, the analysis takes these costs into account indirectly through the increased cost for
the intake manifold and the overall development cost per engine family.
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Table 5.2.2-1
Estimated Costs for an LPG-fueled Large SI Engine
Hardware Cost to Manufacturer
Regulator/throttle body
Intake manifold
Fuel filter w/ lock-off system
LPG vaporizor
Governor
Converter temperature control valve
Oxygen sensor
ECM
Wiring/related hardware
?uel system total
Catalyst/muffler
Vluffler
Total Hardware Cost
Vlarkup @ 29%
\Varranty markup @5%
Total component costs
?ixed Cost to Manufacturer
l&D costs
Jnits/yr.
\mortization period (7 % discounting)
?ixed cost/unit
Total Costs
Baseline
$50
$37
$15
$75
$40
$217
$45
$262
$76
$338
$0
2,000
5
$0
$338
ncremental Total Cost
Controlled
$65
$37
$15
$75
$60
$15
$19
$100
$45
$431
$229
$0
$660
$191
$20
$871
$175,000
2,000
5
$26
$897
$559
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Chapter 5: Estimated Costs
Table 5.2.2-2
Estimated Per-Engine Costs for Gasoline-Fueled Large SI Engines
hardware Cost to Manufacturer
Carburetor
Injectors (each)
Number of injectors
Pressure Regulator
Fuel filter
Intake manifold
Fuel rail
Throttle body /position sensor
Fuel pump
Oxygen sensor
ECM
Governor
Air intake temperature sensor
Manifold air pressure sensor
Injection timing sensor
Wiring/related hardware
7uel system total
Catalyst/muffler
Vtuffler
Total Hardware Cost
Vlarkup @ 29%
Warranty markup @5%
Total Component Costs
?ixed Cost to Manufacturer
l&D Costs
Jnits/yr.
\mortization period (1 % discounting)
7ixed cost/unit
Total Costs
ncremental Total Cost
Baseline
$51
$3
$35
$15
$40
$144
$45
$189
$55
$244
$0
$0
$244
Controlled
$0
$17
4
$11
$4
$50
$13
$60
$30
$19
$150
$60
$5
$11
$12
$45
$538
$229
$767
$222
$29
$1,018
$175,000
1,750
5
$30
$1,048
$805
In addition to these estimated costs for addressing exhaust emissions, we have analyzed
the costs associated with reducing evaporative emissions from gasoline-fueled engines and
vehicles. This effort consists of three primary areas—permeation, diurnal, and boiling.
To reduce permeation losses, we expect manufacturers to upgrade plastic or rubber fuel
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Draft Regulatory Support Document
lines to use automotive-grade materials. These fuel lines are readily available at a cost premium
of about $0.25 per linear foot. If an installed engine has an average of four feet of fuel line, this
translates into an increased cost of $1 per engine.
The standard related to diurnal emissions can be met with a fuel cap that seals the fuel
tank, relieving pressure as needed to prevent the tank from bursting or collapsing. The estimated
cost of upgrading to such a fuel cap is $8, based on the aftermarket cost of comparable
automotive fuel caps.
Many Large SI engines are installed in equipment in a way that poses little or no risk of
fuel boiling during engine operation. A few models are configured in a way that causes this to be
a possibility, at least under extreme conditions. Preventing fuel boiling is primarily a matter of
isolating the fuel tank from heat sources, such as the engine compartment and the exhaust pipe.
Some additional material may be needed to reduce heat exposure, such as a simple metal shield
or a fiberglass panel. Given several years to redesign engines and equipment, we believe that
manufacturers can readily incorporate such changes into their ongoing R&D programs. To
account for several hours of engineering effort and a small amount of material, we estimate that
these costs averaged over the whole set of gasoline-fueled engines will come to about $1 per
engine.
5.2.2.2 Operating Cost Savings
Introducing electronic closed-loop fuel control will significantly improve engine
operation, with corresponding cost savings, in three areas— reduced fuel consumption, less
frequent oil changes and tuneups, and delayed time until rebuild.
It may also be appropriate to quantify the benefit of longer total engine lifetimes. For
example, passenger cars with low-emission engine technologies last significantly longer than
they did before manufacturers developed and applied these technologies. In addition, engine
performance (responsiveness, reliability, engine warm-up, etc.) will also improve with the new
technologies. However, these benefits are more difficult to quantify and the analysis therefore
does not take them into account.
Fuel consumption rates will improve as manufacturers no longer design engines for
operation in fuel-rich conditions. Some current systems already operate at somewhat leaner air-
fuel ratios than in previous years, but even in these cases, engines generally revert to richer
mixtures when accelerating. Closed-loop fuel systems generally operate close to stoichiometry,
which improves the engine's efficiency of converting the fuel energy into mechanical work.
Information in the docket, including development testing, engineering projections, and user
testimony, leads to an estimated 20-percent reduction in fuel consumption rates.7'8'9 Table 5.2.2-3
shows the value of the estimated fuel savings. These values and calculations are based on our
NONROAD emissions model.
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Chapter 5: Estimated Costs
Table 5.2.2-3
Estimated Fuel Savings from Large SI Engines
Horsepower
Load factor
Annual operating hours, hr/yr
Lifetime, yr
Baseline bsfc, Ib/hp-hr
Improved bsfc, Ib./hp-hr
Fuel density
Fuel cost
Annual fuel saved (gal/yr)
Annual fuel savings ($/yr)
^ifetime Fuel Savings (NPV)
LPG
66
0.39
1,365
12
0.507
0.406
4.2 Ib./gal
$0.60/gal
845
$507
$4,333
Gasoline
52
0.58
537
12
0.605
0.484
6.1 Ib./gal
$1.10/gal
321
$353
$3,038
Natural gas
65
0.49
1,161
13
0.507
0.406
0.05 .g./ft3
$2. 17/1000 ft3
—
$160
$1,427
In addition to the fuel savings, we expect Large SI engines to see significant
improvements in reliability and durability. Open-loop fueling systems in uncontrolled engines
are prone to drifting calibrations as a result of varying fuel quality, wear in engine components,
changing ambient conditions, and other factors. Emission-control systems that operate with a
feedback loop to compensate for changing conditions for a near-constant air-fuel ratio
significantly reduces the following problems.
-incomplete (and eventually unstable) combustion
-absorption of fuel in lubricating oil
-deposits on valves, spark plugs, pistons, and other engine surfaces
-increased exhaust temperatures
Automotive engines clearly demonstrate that modern fuel systems reduce engine wear and the
need for repairs.
This analysis incorporates multiple steps to take these anticipated improvements into
account. First, oil change intervals are estimated to increase by 15 percent. Reduced fuel loading
in the oil (and other improvements such as piston ring design) can significantly extend its
working life. Similarly, tune-up intervals are estimated to increase by 15 percent. This results
largely from avoiding an accumulation of deposits on key components, which allows for longer
operation between regularly scheduled maintenance. Third, we estimate that engines will last 15
percent longer before needing overhaul. The reduced operating temperatures and generally
reduced engine wear associated with closed-loop fuel systems account for this extended lifetime
to rebuild. These quantitative estimates of maintenance-related savings are derived from
observed changes in automotive performance when upgrading from carburetion to fuel injection.
Table 5.2.2-4 summarizes the details of the methodology for converting these maintenance
improvements into estimated cost savings over the lifetime of the engines.
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Draft Regulatory Support Document
Table 5.2.2-4
Maintenance
Baseline oil change interval (hrs)
Improved oil change interval (hrs)
Cost per oil change ($)
Baseline tune-up interval (hrs)
Improved tune-up interval (hrs)
Cost per tune -up ($)
Baseline rebuild interval (hrs)
Improved rebuild interval (hrs)
Rebuild cost ($)
3aseline lifetime maintenance cost
improved lifetime maintenance cost
^ifetime maintenance savings (NPV)
LPG/
natural gas
200
230
$30
400
460
$75
7,000
8,050
$800
$2,902
$2,681
$221
Gasoline
150
172.5
$30
400
460
$75
5,000
5,750
$800
$2,573
$2,354
$219
These large estimated fuel and maintenance savings relative to the estimated incremental
cost of producing low-emitting engines raise the question of why normal market forces have
failed to induce manufacturers to design and sell engines with emission-control technologies on
the basis of the expected performance improvements. Since forklifts are the strongly dominant
application using Large SI engines, this question effectively applies specifically to forklifts. We
have observed that forklift users generally see their purchase as an expense that doesn't add value
to a companies product, whether that applies to manufacturing, warehouse, or retail facilities.
While operating expenses require no internal justification or decision-making process,
purchasing new equipment involves extensive review and oversight by managers who are very
sensitive to capital expenditures. This is reinforced by an April 2000 article in a trade
publication, which quotes an engineering estimate of 20- to 40-percent improvement in fuel
economy while stating that it is unclear whether purchasers will tolerate any increase in the cost
of the product.10 Market theory would predict that purchasers would select products with
technologies that result in the lowest net cost (with some appropriate discount for costs incurred
over time). It seems that companies have historically focused on initial costs to the exclusion of
potential cost savings over time, which would account for the lack of emission-control
technologies on current sales of Large SI engines.
This priority given to initial cost therefore affects the competitive decisions of engine
manufacturers, who will be less willing to provide a more costly product than its competitors,
even if the product would eventually provide substantial savings to the purchaser. Also, the
initial costs of changing designs and using new technologies can serve as a deterrent to including
newer cost-efficient technologies in established engine types.
In addition to the engine improvements described above, the costs associated with
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Chapter 5: Estimated Costs
controlling evaporative emissions would be offset by savings from retaining more fuel that can
be used to power the engine.
5.2.2.3 Compliance Costs
We estimate that certification costs come to $70,000 per engine family. We expect
manufacturers to combine similar engines using different fuels in the same family. This expands
the size of engine families, but calls for several tests to complete the certification process for
each family. This includes six engine tests and $10,000 worth of engineering and clerical effort
to prepare and submit the required information. Until engine designs are significantly changed,
engine families can be recertified each year using carryover of the original test data. This cost is
therefore amortized over five years of engine sales, with an assumed volume of 3,000 engines per
year from each engine family. This engine-family sales volume is larger than those presented for
amortizing fixed costs above, because engine families will include multiple fuel types. The
resulting cost for certification is $6 per engine. Since these engines are currently not subject to
any EPA emission requirements, the analysis includes a cost to recertify an upgraded engine
model every five years. Since manufacturers already need to submit data for California
certification, they will incur most of these costs independent of EPA requirements.
The proposal includes a requirement to do production-line testing on a quarterly basis.
Manufacturers with sustained, good test results can greatly reduce testing rates. Manufacturers
must generate and submit this test data to comply with the requirements adopted by California
ARB. The EPA requirement for production-line testing therefore adds no test burden to
manufacturers. Even with a transient duty cycle for certification, we are proposing to allow
manufacturers to use only steady-state test procedures a the production line. We therefore fully
expect that manufacturers will only need to send the "California" test data to EPA to satisfy
requirements for production-line testing. The analysis therefore includes no cost for additional
routine testing of production engines. In fact, the proposal includes a provision that would allow
manufacturers to pursue alternate methods to show that production engines comply with
emission standards, which may lead to lower testing costs.
The proposal allows us to select up to 25 percent of a manufacturers' s engine families for
in-use testing. This means that a manufacturer would need to have eight engine families for us to
be able to select two engine families in a given year. Since this is likely to be a rare scenario, we
project an annual testing rate of one engine family per year for each manufacturer to assess the
cost of the in-use testing program. The analysis includes the cost of testing in-use engines on a
dynamometer, which requires:
engine removal and replacement ($4,000)
transport ($1,000)
steady-state and transient testing ($ 15,000)
Testing six engines and adding costs for administration and reporting of the testing program
leads to a total cost of about $125,000 for an engine family. These costs can be spread over a
manufacturer's total annual sales, which averages about 15,000 units for most companies. The
resulting cost per engine is about $8.
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As with production-line testing, we would expect in-use emission testing to
simultaneously satisfy California ARB and EPA requirements. In certain circumstances,
however, we may use our discretion to direct a manufacturer to do in-use testing on an engine
family separately from California ARB. Since we expect this to be the exception, this analysis
likely overestimates the cost impact of adopting federal requirements to do in-use testing. In
fact, manufacturers may reduce their compliance burden with the optional field-testing
procedures we are proposing. Table 5.2.2-5 shows the estimated costs from the various
compliance programs.
Table 5.2.2-5
Cost of Compliance Programs
Compliance Program
Element
Certification
In-use testing
Total
Estimated Per-
Engine Costs
$6
$8
$14
5.2.2.4 Total Costs
Table 5.2.2-6 presents the combined cost figures for the different engine types and
calculates a composite cost based on their estimated distribution. The estimated 2004 costs are
based on the adding component costs and compliance costs. No R&D cost is estimated for
manufacturers to do additional development work beyond what is necessary to comply with
California ARB standards. Conversely, the estimated 2007 costs are based on R&D (and
ongoing compliance costs), with no anticipated increase in component costs, except those related
to reducing evaporative emissions. The estimated cost of complying with the proposed emission
standards is sizable, but the lifetime savings from reduced operating costs nevertheless more than
compensate for the increased costs
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Chapter 5: Estimated Costs
Table 5.2.2-6
Estimated First-Year Cost Impacts of New Emission Standards
Standards
2004
Engine Type
LPG
natural gas
gasoline
Composite
Sales Mix of
Engine Types
68%
9%
23%
—
Increased Production
Cost per Engine*
$550
$550
$790
$600
Lifetime Operating Costs
per Engine (NPV)
$-4,550
$-1,650
$-3,260
$-3,985
2007
LPG
natural gas
gasoline
Composite
68%
9%
23%
—
$40
$40
$55
$45
—
—
**
—
*The estimated long-term costs decrease by about 35 percent.
**Gasoline-fueled engines would experience fuel savings due to evaporative emission control, but these are not
quantified here.
5.2.2.5 Large SI Aggregate Costs
The above analyses developed incremental per-vessel cost estimates for Large SI engines.
Using these per-engine costs and projections of future annual sales, we have estimated total
aggregate annual costs for proposed emission standards. The aggregate costs are presented on a
cash-flow basis, with hardware and fixed costs incurred in the year the vehicle is sold and fuel
savings occurring as the engines are operated over their lifetimes. Table 5.2.2-7 presents a
summary of this analysis. As shown in the table, aggregate net costs generally range from $75
million to $90 million. Net costs decline as fuel savings continue to ramp-up as more vehicles
meeting the standards are sold and used. Fuel savings are projected to more than offset the costs
of the program starting by the second year of the program.
Table S.2.2.-7
Summary of Annual Aggregate Costs and Fuel Savings for Large SI Engines
(millions of dollars)
Total Costs
Fuel Savings
Net Costs
2004
$88
($49)
$38
2005
$90
($96)
($7)
2010
$73
($313)
($240)
2015
$76
($431)
($355)
2020
$84
($490)
($406)
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Draft Regulatory Support Document
To project annual sales, we started with the number of model year 2000 engines estimated
by the NONROAD model for the 2000 calendar year. We then applied a growth rate of 3 percent
of year 2000 sales (increasing by 3,900 units annually) to estimate future sales. Table 5.2.2.-8
provides a summary of the sales estimates used in the aggregate cost analysis.
Table 5.2.2.-S
Estimated Annual Sales of Large SI Engines
2000
130,000
2004
145,600
2010
169,000
2020
208,000
To calculated annual aggregate costs, the sales estimates have been multiplied by the per-
unit costs. Annual fuel savings have been calculated based on the reduction in fuel consumption
expected from the proposed standards (as described in section 5.2.2.2 of this chapter) as
calculated by the NONROAD model. The model takes into consideration vehicle sales and
scrappage rates. The year-by-year results of the analysis are provided in Chapter 7.
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Chapter 5: Estimated Costs
5.2.3 Recreational Vehicles
5.2.3.1 Technologies and Estimated Costs
We estimated costs separately for snowmobiles, ATVs, and off-highway motorcycles.
Individual technology costs were developed in cooperation with EPA by ICF Incorporated and
Arthur D. Little - Acurex Environmental.11 Costs were prepared for a typical engine that falls
within the displacement ranges noted below. Costing out multiple engine sizes allowed us to
estimate any differences in costs for smaller vs. larger engines. The costs include a mark-up to
the retail level. This Chapter also provides a brief overview of the technologies, with more
information provided in Chapter 4. Costs are provided for both the baseline technology and the
new technology (e.g., a two-stroke engine and a four-stroke engine), with the cost of the change
in technology being the increment between the two costs.
The R&D costs shown are average costs. The first engine line R&D cost is expected to
be significantly higher but the costs would be distributed across the manufacturer's entire product
line.12 To account for any additional warranty cost associated with a change in technology, we
have added 5 percent of the incremental hardware cost.13
As noted in section 5.1, fixed costs are spread over the first five years of sales for
purposed of the cost analysis, with the exception of new facility costs for ATV testing which are
spread over 10 years. We have used 10 years for amortization rather than 5 years because we
believe it is more representative for a capital investment that will be used at least that long. We
estimated that R&D and facility costs would be incurred three years prior to production on
average and tooling and certification costs would be incurred one year prior to production. These
fixed costs were then increased seven percent for each year prior to the start of production to
reflect the time value on money.
To approximate average annual sales per engine line, we divided the total annual unit
sales by estimated total number of engines lines industry-wide."1 Based on limited sales data
from individual manufacturers provided to EPA on a confidential basis, there appears to be a
large distinction in sales volume between small engine and large engine displacements for ATVs.
The cost analysis accounts for this difference by using a larger annual sales rate per engine line
for large ATVs, as shown below.
As noted below, the fuel savings over the life of the vehicle due to some of the projected
technology changes can be substantial and in some cases are projected to offset the cost of the
emissions controls. As discussed below, these fuel savings would occur because 2-stroke
powerplants are inefficient and the changes needed to reduce hydrocarbons also improve fuel
m Based on publicly available product information for the large manufacturers, we
estimated 32 engine lines for snowmobiles, 43 lines for ATVs, and 42 lines for off-highway
motorcycles.
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Draft Regulatory Support Document
consumption. Because the fuel savings can outweigh up front costs, one might question why
manufacturers continue to use 2-stroke engines. Manufacturers have not made these changes in
the absence of emissions standards for several likely reasons. Many customers generally do not
place a high value on fuel economy compared to initial cost and engine simplicity.
Manufacturers have built a customer base over many years using 2-stroke technology. The
engines are relatively simple and the production costs are relatively low because the
manufacturers have been building the engines for many years. To capture the fuel economy
benefits, manufacturers would have to invest substantially in R&D and more complex
powerplants in the face of uncertainty with regard to market acceptance of the new product.
Such a move could also lower profits per vehicle. Considering all these factors, manufacturers
choose to focus improvements in other areas such as increasing horsepower and overall vehicle
design.
Snowmobiles
Snowmobiles are currently almost exclusively powered by carbureted 2-stroke engines.
We are basing the cost analysis for Phase 1 standards on the use of engine modifications,
carburetor improvements, and recalibration. Manufacturers are likely to be able to meet
standards by leaning out the air/fuel mixture, improving carburetors for better fuel control and
less production variation, and modifying the engine to withstand higher temperatures and
potential misfire episodes attributed to enleanment. Engine modifications are also likely to be
made to improve air/fuel mixing and combustion. A small number of models are equipped with
electronic fuel injection and these models would not have carburetor improvement costs
associated with them. Tables 5.2.3.-1 and 5.2.3.-2 provide estimates of variable and fixed costs
associated with the technologies that form the basis of our cost analysis for Phase 1.
Recalibration work is included as part of the R&D for the technologies. The incremental cost per
unit for engine modifications is estimated to be $17 to $24, with modifications to the carburetor
estimated to cost an additional $18 to $24 per engine.
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Chapter 5: Estimated Costs
Table 5.2.3.-1. Snowmobile Engine Modification Costs for Two-Stroke Engines
< 500 cc
Baseline
Modified
> 500 cc
Baseline
Modified
Hardware Costs
Improved Pistons
Number Required
Hardware Cost to Manufacturer
Labor @ $28 per hour
Labor Overhead @ 40%
Manufacturer Mark-up @ 29%
$10
2
$20
$6
$2
$6
Warranty Mark-up @ 5%
Total Component Costs
$34
$12
2
$24
$6
$2
$7
$0
$39
$12
o
J
$36
$8
$3
$10
$57
$15
3
$45
$8
$3
$13
$0
$69
Fixed Cost to Manufacturer
R&D Costs per line
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$0
4600
5
$0
$34
$178,500
$25,000
4600
5
$12
$51
$17
$0
$0
4,600
5
$0
$57
$178,500
$25,000
4600
5
$12
$81
$24
5-21
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Draft Regulatory Support Document
Table 5.2.3-2. Modified Carburetor Costs for Snowmobiles
< 500 cc
Baseline
Modified
> 500 cc
Baseline
Modified
Hardware Costs
Carburetor
Number Required
Hardware Cost to Manufacturer
Labor @ $28 per hour
Labor Overhead @ 40%
Manufacturer Mark-up @ 29%
Warranty Mark-up @ 5%
Total Component Costs
$60
2
$120
$1
$1
$35
$157
$65
2
$130
$1
$1
$o o
38
$1
$171
$60
o
5
$180
$2
$1
$53
$236
$65
3
$195
$2
$1
$57
$1
$256
Fixed Cost to Manufacturer
R&D Costs per line
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$0
4,600
5
$0
$157
$61,875
$5,000
4,600
5
$4
$175
$18
$0
$0
4,600
5
$0
$236
$61,875
$5,000
4,600
5
$4
$260
$24
Manufacturers may use an expanded mix of technologies to meet Phase 1 standards. If
manufacturers are successful in developing and deploying advanced technologies for
snowmobiles such as 4-stroke engines and 2-stroke direct injection in the Phase 1 time frame, the
mix of technologies for Phase 1 would be somewhat different. These technologies paths would
provide much lower CO and HC emissions, as discussed in Chapter 4. Although these
technologies would increase the cost of the engines, they would also potentially provide the
consumer with greatly improved fuel economy, reliability, and in the case of direct injection,
performance. For these reasons, we would expect manufacturers to continue to develop these
advanced technologies and implement them when they are ready.
The cost analysis for the Phase 2 standards is based primarily on the use of direct fuel
injection 2-stroke engines and 4-stroke engines for a portion of the fleet. We would expect that
by the 2010 time frame these two technologies will be developed and able to be used on a
significant fraction of the fleet. For cost purposes, we are projecting that 4-stroke engines are
likely to be equipped with electronic fuel injection systems to optimize emissions and overall
performance of these engines. Therefore we are including electronic fuel injection costs for 4-
strokes. Tables 5.2.3.-3 through 5.2.3.-6 provide costs for direct injection systems (both air
assisted direct injection and pump assisted direct injection) and for converting from a 2-stroke to
4-stroke engine.
5-22
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Chapter 5: Estimated Costs
Table 5.2.3-3. Air Assisted Direct Injection System Costs for Snowmobiles
< 500 cc > 500cc
Baseline
Modified
Baseline
Modified
Hardware Costs
Carburetor
Number Required
Fuel Metering Solenoid (each)
Number Required
Air Pump
Air Pump Gear
Air Pressure Regulator
Throttle Body/Position Sensor
Intake Manifold
Electric Fuel Pump
Fuel Pressure Regulator
ECM
Air Intake Temperature Sensor
Manifold Air Pressure Sensor
Injection Timing Sensor/Timing Wheel
Wiring/Related Hardware
Hardware Cost to Manufacturer
Labor @ $28 per hour
Labor overhead @ 40%
OEM mark-up @ 29%
Royalty @ 3%
Warranty Mark-up @ 5%
Total Component Costs
$60
2
$5
$125
$1
$1
$37
$164
$15
2
$25
$5
$5
$35
$30
$5
$3
$140
$5
$11
$10
$20
$324
$14
$6
$100
$10
$10
$464
$60
o
5
$5
$185
$2
$1
$55
$243
$15
3
$25
$5
$5
$35
$30
$5
$3
$140
$5
$11
$10
$20
$339
$21
$8
$107
$10
$8
$493
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$0
4,600
5
$0
$164
$178,500
$25,000
4,600
5
$12
$476
$312
$0
$0
4,600
5
$0
$243
$178,500
$25,000
4,600
5
$12
$505
$262
5-23
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Draft Regulatory Support Document
Table 5.2.3-4. Pump-Assisted Direct Fuel Injection System Costs for Snowmobiles
< SOOcc
Baseline
Modified
> SOOcc
Baseline
Modified
Hardware Costs
Carburetor
Number Required
Nozzle/ Accumulator (each)
Number Required
High-Pressure Cam Fuel Pump
Cam Pump Gear
Throttle Body/Position Sensor
Intake Manifold
Fuel Transfer Pump
ECM
Air Intake Temperature Sensor
Manifold Air Pressure Sensor
Injection Timing Sensor/Timing Wheel
Wiring/Related Hardware
Hardware Cost to Manufacturer
Labor @ $28 per hour
Labor overhead @ 40%
OEM mark-up @ 29%
Royalty @ 3%
Warranty Mark-up @ 5%
Total Component Costs
$60
2
$5
$125
$1
$1
$37
$164
$33
2
$20
$5
$35
$30
$5
$140
$5
$11
$10
$20
$347
$14
$6
$106
$10
$11
$494
$60
o
3
$5
$185
$2
$1
$55
$243
$33
3
$25
$5
$35
$30
$5
$140
$5
$11
$10
$20
$385
$21
$8
$120
$12
$10
$556
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$0
4,600
5
$0
$164
$178,500
$25,000
4,600
5
$12
$506
$342
$0
$0
4,600
5
$0
$243
$178,500
$25,000
4600
5
$12
$568
$325
5-24
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Chapter 5: Estimated Costs
Table 5.2.3-5. Two-Stroke to Four Stroke Conversion Costs for Snowmobiles
< 500 cc
2-Stroke
4-Stroke
> 500 cc
2-Stroke
4-Stroke
Engine
Clutch
Labor @ $28 per hour
Labor overhead @ 40%
Markup @ 29%
Warranty Mark up @ 5%
Total Component Costs
$400
$50
$14
$6
$136
$606
$700
$75
$21
$8
$233
$16
$1,053
$650
$80
$14
$6
$217
$967
$1,170
$120
$21
$8
$OOO
JoJ
$28
$1,730
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$0
4,600
5
$0
$606
$94,416
$20,000
4,600
5
$7
$1,060
$454
$0
$0
4,600
5
$0
$967
$94,416
$20,000
4600
5
$7
$1,737
$770
5-25
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Draft Regulatory Support Document
Table 5.2.3-6. Electronic Fuel Injection Costs for Snowmobiles
Fuel Injection Costs
400cc
Baseline
Modified
700cc
Baseline
Modified
Hardware Costs
Carburetor
Number Required
Injectors (each)
Number Required
Pressure Regulator
Intake Manifold
Throttle Body/Position Sensor
Fuel Pump
ECM
Air Intake Temperature Sensor
Manifold Air Pressure Sensor
Injection Timing Sensor
Wiring/Related Hardware
Hardware Cost to Manufacturer
Labor @ $28 per hour
Labor Overhead @ 40%
Manufacturer Mark-up @ 29%
Warranty Mark-up" @ 5%
Total Component Costs
$60
2
$5
$125
$1
$1
$37
$164
$12
2
$10
$30
$35
$20
$100
$5
$10
$5
$10
$249
$4
$2
$72
$6
$333
$60
o
3
$5
$185
$2
$1
$54
$242
$12
3
$10
$35
$35
$20
$100
$5
$10
$5
$10
$266
$6
$3
$77
$4
$356
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs ($)
Incremental Total Cost ($)
$0
$0
4,600
5
$0
$164
$69,417
$10,000
4,600
5
$5
$338
$174
$0
$0
4,600
5
$0
$242
$69,417
$10,000
4,600
5
$5
$361
$119
We have estimated the incremental cost of going from carbureted 2-stroke to direct
injection to range from $262 to $342 per engine and conversion to 4-stroke to be about $454 to
$770. Electronic fuel injection for snowmobiles is estimated to incrementally cost $174 to $119.
It should be noted that the overall consumer costs for these advanced technologies would be
substantially lower after the fuel economy improvements are taken into account. Estimates of the
fuel savings are provided below.
5-26
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Chapter 5: Estimated Costs
Manufacturers are likely to concentrate the use of the above technologies on the more
expensive or performance oriented models. We are projecting that 50 percent of models will be
equipped with either direct injection or 4-stroke engines. We anticipate that remaining models
would consist of Phase 1 technologies with some further optimization. We are projecting the use
of pulse air systems with recalibration on the portion of snowmobile engines that are not
equipped with advanced technology systems. Pulse air would provide a small incremental
emission reduction for these engines and help manufacturers meet the Phase 2 average HC and
CO standards. As shown in Table 5.2.3.-7, we have estimated pulse air to cost about $16.
Catalysts are also a potential option for snowmobiles. However, we believe manufacturers are
more likely to focus on developing the advanced technologies noted above, which provide the
consumer with substantial benefits in addition to lower emissions. Therefore, have we not
included catalyst costs in our cost estimates.
Table S.2.3.-7. Calibration/Pulse-Air Costs for Snowmobiles
Baseline
Modified
Hardware Costs
Pulse Air Valve
Labor @ $28 per hour
Labor overhead @ 40%
Markup @ 29%
Warranty Mark up @ 5%
Total Component Costs
$0
$8
$1
$0
$3
$0
$12
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$54,750
$10,000
4,600
5
$4
$16
$16
All-terrain Vehicles (A TVs)
ATVs are primarily equipped with carbureted 4-strokes, with 2-stroke engines used
primarily in small displacement and sport models. For the first phase of standards, we expect
manufacturers to phase out the use of 2-stroke engines. In addition, we are also projecting that
recalibration and pulse air systems would be used on about 25 percent of the models for Phase 1
to ensure that the fleet meets the standards on average. Pulse air systems are currently used on a
few ATV and off-highway motorcycles models to meet California standards. We do not believe
that the level of the standards would require the use of pulse air beyond 25 percent, given that
5-27
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Draft Regulatory Support Document
only a few models in California are currently equipped with the technology. Using these
technologies may give the manufacturer more flexibility in calibrating for performance on some
models.
We are basing our technology projection on what manufacturers have done to meet the
California emissions standards. We believe this to be the most likely technology path for
manufacturers because 4-strokes are accepted in the market and provide consumers with fuel
economy and reliability benefits. Substantial new R&D and major changes in technology would
be needed to allow 2-stroke engines to meet the proposed Phase 1 standards. Because
manufacturers would be able to carry over certification from the California emissions control
program, manufacturers would already have many models equipped with 4-strokes that would
meet the proposed Phase 1 standards.
For Phase 2, we are projecting that manufacturers would significantly increase the use of
pulse air systems, from 25 percent for Phase 1 to 75 percent for phase 2. We would expect that
the remaining emissions reductions would be achieved through recalibration and the use of
oxidation catalysts on a fraction of ATVs models.
Catalysts have not been used to date on ATVs, but we would expect that their use on
some ATV models would be attractive for manufacturers in complying with Phase 2 standards.
Using a catalyst to control emissions would allow manufacturers to calibrate more for
performance. Catalysts are typically sized at about half the engine displacement and typically
achieve at least about a 50 percent reduction in emissions.
For purposes of the cost analysis, we are projecting catalyst use for 50 percent of ATV
models. We believe that this is conservatively high because manufacturers have substantial lead-
time to optimize engine emissions performance and may be able to achieve Phase 2 standards
using catalysts on fewer models.
Tables 5.2.3.-8 through 5.2.3-10 provide cost estimates for the ATV technologies
discussed above. Table 5.2.3.-11 provides a breakdown of the estimated costs of the catalyst.
We estimate the incremental cost per unit of replacing a 2-stroke engine with a 4-stroke engine to
be about $220 to $350, depending on engine size. Costs for a mechanical pulse air system and
recalibration is estimated to be about $13 to $16 per unit. The cost of a catalyst system is
estimated to be about $60. As shown in the tables below, fixed costs for larger displacement
models are spread over a significantly larger annual unit sales volume to account for the
relatively high average number of unit sales per engine line for these products.
5-28
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Chapter 5: Estimated Costs
Table 5.2.3.-S Two-Stroke to Four Stroke Conversion Costs for ATVs
< 200 cc
2-Stroke
4-Stroke
> 200 cc
2-Stroke
4 Stroke
Hardware Costs
Engine
Labor @ $28 per hour
Labor overhead @ 40%
Markup @ 29%
Warranty Mark up @ 5%
Total Component Costs
$400
$14
$6
$122
$542
$550
$21
$8
$168
$8
$755
$500
$14
$6
$151
$671
$750
$21
$8
$226
$13
$1,018
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$0
4,200
5
$0
$542
$94,416
$15,000
4,200
5
$7
$762
$220
$0
$0
15,000
5
$0
$671
$94,416
$18,000
15000
5
$2
$1,020
$349
5-29
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Draft Regulatory Support Document
Table 5.2.S.-9. Four-stroke Calibration/Pulse-Air Costs for Four-Stroke ATVs
< 200 cc
Baseline
Modified
> 200 cc
Baseline
Modified
Hardware Costs
Pulse Air Valve
Labor @ $28 per hour
Labor overhead @ 40%
Markup @ 29%
Warranty Mark up @ 5%
Total Component Costs
$0
$8
$1
$0
$3
$0
$12
$0
$8
$1
$0
$3
$0
$12
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$54,750
$8,000
4,200
5
$4
$16
$16
$0
$54,750
$10,000
15000
5
$1
$13
$13
Table 5.2.3.-10. Oxidation Catalyst Costs for 4-Stroke ATV
< 200 cc
Baseline
Modified
> 200 cc
Baseline
Modified
Hardware Costs
Oxidation Catalyst
Labor @ $28 per hour
Labor overhead @ 40%
OEM markup @ 29%
Warranty Mark up @ 5%
Total Component Costs
$0
$39
$1
$1
$12
$2
$55
$0
$44
$1
$1
$13
$2
$61
Fixed Cost to Manufacturer
R&D Costs
Tooling Costs
Units/yr.
Years to recover
Fixed cost/unit
Total Costs
Incremental Total Cost
$0
$59,500
$10,000
4,200
5
$5
$60
$60
$0
$59,500
$12,000
15,000
5
$1
$62
$62
5-30
-------
Chapter 5: Estimated Costs
Table 5.2.3-11. Oxidation Catalyst Cost Breakdown
Catalyst Characteristic
Washcoat Loading
% ceria
% alumina
Precious Metal Loading
% Platinum
% Palladium
% Rhodium
Labor Cost
Unit
g/L
bywt.
bywt.
g/L
bywt.
bywt.
bywt.
$/hr
Value
160
50
50
1.8
83. 3
0.0
16.7
$28.00
Material
Alumina
Ceria
Platinum
Palladium
Rhodium
Stainless Steel
$/troy
oz
$412
$390
$868
$/lb
$5.00
$5.28
$1.12
$/g
$0.011
$0.012
$13.25
$12.54
$27.91
$0.002
Density
(e/cc)
3.9
7.132
7.817
5-31
-------
Draft Regulatory Support Document
Catalyst Volume (cc)
Substrate Diameter (cm)
Substrate
Ceria/ Alumina
Pt/Pd/Rd
Can (18 gauge 304 SS)
Substrate Diameter (cm)
Substrate Length (cm)
Working Length (cm)
Thick, of Steel (cm)
Shell Volume (cc)
Steel End Cap Volume (cc)
Vol. of Steel (cc) w/ 20% scrap
Wt. of Steel (g)
TOTAL MATERIAL COST
LABOR
Labor Overhead @ 40%
Supplier Markup @ 29%
Manufacturer Price
100
4
$6.93
$0.18
$2.83
$0.43
4.00
8.0
10.8
0.121
12
4
19
150
$10.37
$14.00
$5.60
$8.69
$38.66
200
6
$7.87
$0.36
$3.97
$0.64
6.00
7.1
9.9
0.121
16
8
29
227
$12.85
$14.00
$5.60
$9.90
$44.02
350
8
$9.27
$0.63
$6.95
$0.93
8.00
7.0
9.8
0.121
21
14
42
328
$17.78
$14.00
$5.60
$11.69
$52.01
Off-highway Motorcycles
Currently, off-highway motorcycles are about 65 percent 2-stroke, with many of the 2-
stroke engines used in competition and youth models. We are projecting essentially the same
mix of technologies for off-highway motorcycle as for ATVs (Phase 1), discussed above. As
with ATVs, we would expect that standards would be met primarily through the use of 4-stroke
engines. Manufacturers may also use pulse air systems and recalibration on a fraction of their
models to ensure their overall fleet meets the standards. We have estimated their use for off-
highway motorcycles at about 25 percent. We do not believe that the level of the standards
would require the use of pulse air beyond 25 percent, given the only a few models in California
are currently equipped with the technology. As discussed in 5.2.3.4 below, vehicles used solely
for competition are exempt from standards and we would expect some 2-stroke competition
models to remain in the market.
Tables 5.2.3.-12 and 5.2.3.-13 provide cost estimates for off-highway motorcycles
technologies for three engine displacement ranges. We estimate the incremental cost per unit of
replacing a 2-stroke engine with a 4-stroke engine to be about $220 to $360, depending on engine
size. Costs for a mechanical pulse air valve system and recalibration is estimated to be about $17
per unit.
5-32
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Chapter 5: Estimated Costs
5.2.3.2 Operating Cost Savings
Snowmobiles
Both direct injection and conversion from two-stroke to 4-stroke yield substantial fuel
economy benefits. Typical 2-stroke engines have relatively poor fuel economy performance
because a portion of the combustion mixture passes through the engines unburned. Because 4-
stroke and direct injection 2-stroke engine designs essentially do not allow this to occur, they
provide better fuel economy as well as substantially lower HC emissions. We have estimated
fuel savings based on a 25 percent reduction in fuel consumption, based on typical performance
of these technologies. Lifetime fuel costs are provided in Table 5.2.3.-14.14'15
Table 5.2.3.-14. Fuel Cost for Snowmobiles
Engine
Engine power
Load Factor
Annual Operating Hours, hr/yr
Lifetime, yr
BSFC, Ib/bhp-hr
Fuel Density (Ibs/gal)
Fuel Cost ($/gal)*
Yearly Fuel Consumption (gal/yr)
Yearly Fuel Cost ($/yr)
Lifetime Fuel Cost (NPV)
Baseline 2-Stroke
small
75
0.34
57
9
1.66
6.1
$1.10
396
$435
$2,835
large
125
0.34
57
9
1.25
6.1
$1.10
659
$725
$4,725
Advanced Technology
Engines (25% savings)
small
75
0.34
57
9
1.66
6.1
$1.10
297
$326
$2,126
large
125
0.34
57
9
1.25
6.1
$1.10
494
$544
$3,543
* Excluding taxes
A TVs and Off-highway Motorcycles
Conversion from 2-stroke to 4-stroke engines would yield a fuel economy improvement
for ATVs and off-highway motorcycles. Tables 5.2.3.-15 and 5.2.3.-16 provide estimates of fuel
consumption for both 2-stroke and 4-stroke engines. We have estimated that switching from a 2-
stroke to a 4-stroke engine would reduce fuel consumption by about 25 percent. Lifetime fuel
savings for ATVs resulting from switching from a 2-stroke to a 4-stroke engine is estimated to be
$234 for a small displacement engine and $1,166 for a large displacement engine. For off-
highway motorcycles, the projected lifetime fuel savings range from $63 to $311.
5-35
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Draft Regulatory Support Document
Table 5.2.3.-15. Fuel Cost for ATVs
Engine
Engine power
Load Factor
Annual Operating Hours, hr/yr
Lifetime, yr
BSFC, Ib/bhp-hr
Fuel Density (Ibs/gal)
Fuel Cost ($/gal)*
Yearly Fuel Consumption (gal/yr)
Yearly Fuel Cost ($/yr)
Lifetime Fuel Cost (NPV)
2-Stroke
small
5
0.34
350
13
1.05
6.1
$1.10
102
$113
$942
large
25
0.34
350
13
1.05
6.1
$1.10
512
$563
$4,708
4-Stroke
small
5
0.34
350
13
0.79
6.1
$1.10
77
$85
$708
large
25
0.34
350
13
0.79
6.1
$1.10
385
$424
$3,542
* Excluding taxes
Table 5.2.3.-16. Fuel Cost Savings for Off-highway Motorcycles
Engine
Engine power
Load Factor
Annual Operating Hours, hr/yr
Lifetime, yr
BSFC, Ib/bhp-hr
Fuel Density (Ibs/gal)
Fuel Cost ($/gal)*
Yearly Fuel Consumption (gal/yr)
Yearly Fuel Cost ($/yr)
Lifetime Fuel Cost (NPV)
2-stroke
small
5
0.34
120
9
1.05
6.1
$1.10
35
$39
$252
med.
12
0.34
120
9
1.05
6.1
$1.10
84
$93
$604
large
25
0.34
120
9
1.05
6.1
$1.10
176
$193
$1,258
4-stroke
small
5
0.34
120
9
0.79
6.1
$1.10
26
$29
$189
med.
12
0.34
120
9
0.79
6.1
$1.10
63
$70
$454
large
25
0.34
120
9
0.79
6.1
$1.10
132
$145
$947
* Excluding taxes
It should be noted that conversion to 4-stroke engines would also result in savings in oil
consumption and improvements in durability. In a 2-stroke engine, oil is added to the gasoline in
order to lubricate the engine, resulting in a faster oil use rate than in a 4-stroke engine. Also, 4-
stroke engines have increased durability compared to 2-strokes, resulting in less frequent major
engine repairs. We have not attempted to quantify the resulting cost savings, but the savings
would provide a benefit for the consumer.
5-36
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Chapter 5: Estimated Costs
5.2.3.3 Compliance Costs
We estimate ATV and off-highway motorcycle chassis-based certification to cost about
$25,000 per engine line, including $10,000 for engineering and clerical work and $15,000 for
durability and certification testing. For snowmobile engine-based certification, we estimate costs
to be about $30,000, recognizing that engine testing is somewhat more expensive than vehicle
testing due to the time needed to set up the engine on the test stand. As with other fixed costs,
we amortized the cost over 5 years of engine sales to calculate per unit certification costs shown
in Table 5.2.3.-17. The actual certification costs for ATVs and off-highway motorcycles are
likely to be lower than those shown in the table above because manufacturers are likely to use
certification data generated for the California program.
Table 5.2.3.-17 Estimated Per Unit Certification Costs
units/year
certification costs
Snowmobiles
4,600
$1.70
ATVs
4,200
$1.55
15,000
$0.42
Off-highway
Motorcycles
3,500
$1.86
We have estimated that manufacturers would be required to test about 0.2% of production
to meet production line testing requirements. Using per test costs of $2,500 for vehicle testing
and $5,000 per test for engine testing, we estimate a per unit cost for production line testing of
$5 for off-road motorcycles and ATVs and $10 for snowmobiles.
In general, we expect manufacturers would be able to use existing test facilities. For
manufacturers that do not have sufficient chassis testing capabilities for ATVs, we would expect
them to carry over engine-based certifications from the California program during Phase 1 of the
ATV standards. Because the option of carrying over California engine test data would not be
available for Phase 2 standards, manufacturer could be required to conduct chassis testing of
ATVs. Therefore, we have estimated the cost of new chassis testing facilities to be included in
the cost of the Phase 2 standards. The costs are based on an estimate provided by one
manufacturer that a full test cell would cost $2 million to build. We have estimated that on
average manufacturers would need two such facilities to conduct testing. The costs will vary
somewhat among manufacturers depending on the state of their existing facilities and the number
of vehicle families that must be certified. However, we believe that this is a generous estimate
because some manufacturers would likely be able to upgrade existing test facilities instead of
building new facilities.
By estimating $4 million per manufacturer, with 7 manufacturers, and amortizing the
costs over 10 years (10 years x 546,000 units), we estimate an average per unit cost of $8.94. We
have used 10 years for amortization rather than 5 years because we believe it is more
representative for a capital investment that will be used at least that long. It should be noted that
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these costs would be avoided if an adequate engine-based test procedure can eventually be
developed and adopted for ATVs for Phase 2.
5.2.3.4 Recreational Vehicle Total Costs
The analysis below combines the costs estimated above into a total composite or average
cost for each vehicle type. The composite analysis weights the costs by projecting the percentage
of their use, both in the baseline and control scenario, to project industry-wide average per
vehicle costs.
A summary of the estimated near-term and long-term per unit average incremental costs
and fuel savings for recreational vehicles is provided in Table 5.2.3.-18. Long-term costs do not
include fixed costs, which are retired, and include cost reductions due to the learning curve.
Table 5.2.3.-18 Total Average Per Unit Costs and Fuel Savings
near-term costs
long-term costs
fuel savings
(NPV)
Snowmobile
Phase 1
$55
$27
$0
Snowmobile
Phase 2
$216
$125
($509)
ATV
Phase 1
$60
$38
($102)
ATV
Phase 2
$52
$28
$0
Off-
highway
Motorcycle
$151
$94
($98)
Tables 5.2.3.-19 through 5.2.3.-23 provide the detailed average, or composite, per unit
costs for snowmobiles (Phase 1 and Phase 2), ATVs (Phase 1 and Phase 2), and off-highway
motorcycles. The composite costs are based on the estimated distribution of the different engine
displacement ranges. We estimated an approximate distribution of sales among the displacement
ranges using limited sales data provided by some manufacturers on a confidential basis and
production data from Power Systems Research. Incremental costs are shown both for the near-
term and long-term. Long term costs reflect the retirement of fixed costs and the affect of the
learning curve, described in section 5.1.
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Chapter 5: Estimated Costs
Table 5.2.3.-19 Estimated Average Costs For Snowmobiles (Phase 1)
< 500 cc (30%)
> 500 cc (70%)
engine modifications
modified carburetor
compliance
total
engine modifications
modified carburetor
compliance
total
Near Term Composite Incremental Cost
Long Term Composite Incremental Cost
Cost
$17
$18
$12
--
$24
$24
$12
--
--
--
Lifetime Fuel
Savings
$0
$0
-
--
$0
$0
$0
--
--
--
Baseline
0%
0%
0%
--
0%
0%
0%
--
--
--
Control
100%
95%
100%
--
100%
95%
100%
--
--
--
Incremental Cost
$17
$17
$12
$46
$24
$23
$12
$59
$55
$27
Incremental Fuel
Savings
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
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Table 5.2.3.-20 Estimated Average Costs For Snowmobiles (Phase 2)
< 500 cc (30%)
< 500 cc (70%)
pulse air/recalibration
direct injection*
electronic fuel injection
4-stroke engine
compliance
total
pulse air/recalibration
direct injection*
electronic fuel injection
4-stroke engine
compliance
total
Near Term Composite Incremental Cost
Long Term Composite Incremental Cost
Cost
$16
$327
$174
$455
$12
-
$16
$294
$119
$770
$12
--
--
--
Lifetime Fuel
Savings
$0
($709)
$0
($709)
--
-
$0
($1,181)
$0
($1,181)
-
--
--
--
Baseline
0%
0%
5%
1%
0%
-
0%
0%
5%
1%
0%
--
--
--
Control
50%
40%
15%
10%
100%
-
50%
40%
15%
10%
100%
--
--
--
Incremental Cost
$8
$131
$17
$41
$12
$209
$8
$118
$12
$69
$12
$219
$216
$125
Incremental Fuel
Savings
$0
($284)
$0
($64)
$0
($348)
$0
($472)
$0
($106)
$0
($578)
($509)
$0
* Direct injection costs are an average of the air-assisted and pump assisted system costs.
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Chapter 5: Estimated Costs
Table 5.2.3.-21 Estimated Average Costs For ATVs (Phase 1)
<200cc(15%)
> 200 cc (85%)
4-stroke engine
pulse air/recalibration
compliance
total
4-stroke engine
pulse air/recalibration
compliance
total
Near Term Composite Incremental Cost
Long Term Composite Incremental Cost
Cost
$220
$16
$7
--
$349
$13
$6
--
--
--
Lifetime Fuel
Savings
(NPV)
$234
$0
-
--
$1,166
$0
-
--
--
--
Baseline
8%
0%
0%
--
93%
0%
0%
--
--
--
Control
100%
25%
100%
--
100%
25%
100%
--
--
--
Incremental Cost
$202
$4
$7
$213
$24
$3
$6
$33
$60
$38
Incremental Fuel
Savings (NPV)
($215)
$0
-
($215)
$82
$0
-
($82)
($102)
($102)
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Table 5.2.S.-22 Estimated Average Costs For ATVs (Phase 2)
<200cc(15%)
> 200 cc (85%)
4-stroke engine
pulse air/recalibration
oxidation catalyst
compliance
total
4-stroke engine
pulse air/recalibration
oxidation catalyst
compliance
total
Near Term Composite Incremental Cost
Long Term Composite Incremental Cost
Cost
$220
$16
$60
$16
--
$349
$13
$62
$14
--
--
--
Lifetime Fuel
Savings
(NPV)
$234
$0
$0
-
--
$1,166
$0
$0
-
--
--
--
Baseline
100%
25%
0%
0%
--
100%
25%
0%
0%
--
--
--
Control
100%
75%
50%
100%
--
100%
75%
50%
100%
--
--
--
Incremental Cost
$0
$8
$30
$16
$54
$0
$7
$31
$14
$52
$52
$28
Incremental Fuel
Savings (NPV)
$0
$0
$0
-
$0
$0
$0
$0
-
$0
$0
$0
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Chapter 5: Estimated Costs
Table 5.2.3.-2S Estimated Average Costs For Off-highway Motorcycles (Non-competition models only)
< 125 cc (37%)
125<250cc(21%)
> 250 cc (42%)
4-stroke engine
pulse air/recalibration
compliance
total
4-stroke engine
pulse air/recalibration
compliance
total
4-stroke engine
pulse air/recalibration
compliance
total
Near Term Composite Incremental Cost
Long Term Composite Incremental Cost
Cost
$222
$17
$7
-
$289
$17
$7
-
$357
$17
$7
-
-
Lifetime Fuel
Savings
(NPV)
$63
$0
-
-
$150
$0
-
-
$311
$0
-
-
-
Baseline
82%
0%
0%
-
30%
0%
0%
-
45%
0%
0%
-
-
Control
100%
25%
100%
-
100%
25%
100%
-
100%
25%
100%
-
-
Incremental Cost
$40
$4
$7
$51
$202
$4
$7
$213
$196
$4
$7
$207
$151
$94
Incremental Fuel
Savings (NPV)
($11)
$0
-
($11)
($105)
$0
-
($105)
($171)
$0
-
($171)
($98)
($98)
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Currently, off-highway motorcycles are about 63 percent 2-stroke with many of the 2-
stroke engines used in competition and youth models. In recent years, more high performance
and competition models have been successfully introduced with 4-stroke engines and there
appears to be a trend toward increased use of 4-stroke engines. Models used solely for
competition are exempt from CAA requirements and we expect some 2-stroke competition
models would continue to be sold under this exemption. For purposes of the cost analysis, we
have estimated that 29 percent of all off-highway motorcycles would be exempt as competition
models and that these models would be equipped with 2-stroke engines. We have based the
estimate of exempt models on the our estimate of the current use of 2-strokes in the motocross
market. We believe the emissions standards would be reasonably achievable for 4-stroke
engines, especially with averaging, and that manufacturers would elect to certify all 4-stroke
models in order to market them to the widest possible consumer base.
To account for the competition model exemption in the calculation of average costs, we
have adjusted the percentage of 2-stroke engines from the overall baseline percentage of off-
highway motorcycle sales using the 29 percent estimate noted above. This adjustment is
necessary in order to determine the average costs for only those off-highway motorcycles that
would be covered by the program. Table 5.2.3.-24 provides our estimate of the baseline
percentage of 2-strokes in overall sales and the percentage of the non-competition model sales.
Table 5.2.S.-24 Estimated Off-highway Motorcycle Percent 2-stroke Engine Usage
Displacement
< 125 cc
125 to 249 cc
> 250 cc
Overall Baseline
2-stroke percentage
42%
79%
68%
Baseline 2-stroke
percentage Excluding
Competition Models
18%
70%
55%
5.2.3.5 Recreational Vehicle Aggregate Costs
The above analyses developed incremental per vehicle cost estimates for snowmobiles,
ATVs, and off-highway motorcycles. Using these per vehicle costs and projections of future
annual sales, we have estimated total aggregate annual costs for the recreational vehicles
standards. The aggregate costs are presented on a cash flow basis, with hardware and fixed costs
incurred in the year the vehicle is sold and fuel savings occurring as the vehicle is operated over
its life. Table 5.2.3.-25 presents a summary o f the results of this analysis. As shown in the
table, aggregate net costs increase from about $40 million in 2006 to about $70 million in 2010
when the program is fully phased in. Net costs are projected then to decline as fuel savings
continue to ramp-up as more vehicles meeting the standards are sold and used. Fuel savings are
projected to more than offset the costs of the program starting in 2013.
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Chapter 5: Estimated Costs
Table 5.2.3.-2S Summary of Annual Aggregate Costs and Fuel Savings
(millions of dollars)
Snowmobiles
ATVs
Off-highway
Motorcycles
Total
Fuel Savings
Net Costs
2006
$8.49
$27.16
$8.81
$44.46
($4.98)
$39.47
2010
$39.50
$78.46
$13.12
$131.08
($60.55)
$70.53
2015
$25.00
$56.81
$11.63
$93.45
($153.06)
($59.62)
2020
$26.28
$51.93
$12.22
$90.43
($211.20)
($120.77)
2025
$27.62
$51.93
$12.85
$92.40
($227.22)
($134.83)
To project annual sales, we started with 1999 sales estimates provided by industry
organizations. We then adjusted the numbers and applied sales growth estimates consistent with
the modeling performed to estimate total emissions (see Section 6.2.4.1.1). For ATVs, we added
70,000 units to account for sales from companies not included in the industry organization
estimates. Sales growth for snowmobiles and off-highway motorcycle sales is projected to be
about one percent per year. The off-road motorcycle sales were reduced by 29 percent to account
for the exemption of competition models. ATVs are modeled differently because recent sales
growth rates have been significantly higher than one percent but are at rates not likely to be
sustained indefinitely. We project that ATV sales will continue to grow at a higher rate over the
next few years but will level off by 2006. Table 5.2.3.-26 provides a summary of the sales
estimates used in the aggregate cost analysis.
Table 5.2.S.-26 Estimated Annual Recreational Vehicle Sales
Snowmobiles
ATVs
Off-highway
motorcycles*
1999
148,000
616,000
105,790
2006
158,676
838,102
113,421
2010
166,235
838,102
118,027
2020
182,394
838,102
130,375
* Non-competition only
To calculated annual aggregate costs, the sales estimates have been multiplied by the per
unit costs. Fuel savings have been calculated using the NONROAD model to calculate the shift
in use from 2-stroke to 4-stroke vehicles, and also direct injection 2-strokes for snowmobiles,
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over time. The model takes into consideration vehicle sales and scrappage rates. The standards
phase-in schedule for off-highway motorcycles (50/100% in 2006/2007) and ATVs (Phase 1:
50/100% in 2006/2007, Phase 2: 50/100% in 2009/2010) has also been taken into account. The
detailed year-by-year analysis is provided in Chapter 7.
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Chapter 5: Estimated Costs
Chapter 5 References
1. "Update of EPA's Motor Vehicle Emission Control Equipment Retail Price Equivalent (RPE)
Calculation Formula," Jack Faucett Associates, Report No. JACKFAU-85-322-3, September
1985 (Docket A-2000-01, document II-A-54).
2.For further information on learning curves, see Chapter 5 of the Economic Impact, from
Regulatory Impact Analysis - Control if Air Pollution from New Motor Vehicles: Tier 2 Motor
Vehicle Emissions Standards and Gasoline Sulfur Control Requirements, EPA420-R-99-023,
December 1999. A copy of this document is included in Air Docket A-2000-01, at Document
No. U-A-83. The interested reader should also refer to previous final rules for Tier 2 highway
vehicles (65 FR 6698, February 10, 2000), marine diesel engines (64 FR 73300, December 29,
1999), nonroad diesel engines (63 FR 56968, October 23, 1998), and highway diesel engines (62
FR 54694, October 21, 1997).
3."Estimated Economic Impact of New Emission Standards for Heavy-Duty Highway Engines,"
Acurex Environmental Corporation Final Report (FR 97-103), March 31, 1997. The Acurex
Environmental Corporation has since changed its name to Arcadis Geraghty & Miller (Docket A-
2000-01, document II-A-51).
4."Incremental Costs for Nonroad Engines: Mechanical to Electronic," Memorandum from Lou
Browning, Acurex Environmental, to Alan Stout, EPA, April 1, 1997 (Docket A-2000-01,
document U-A-52).
5."Incremental Cost Estimates for Marine Diesel Engine Technology Improvements,"
Memorandum from Louis Browning and Kassandra Genovesi, Arcadis Geraghty & Miller, to
Alan Stout, EPA, September 30, 1998 (Docket A-2000-01, document II-A-53).
6."Large SI Engine Technologies and Costs," Arthur D. Little - Acurex Environmental, Final
Report, September 2000.
7. "Exhaust Controls Available to Reduce Emissions from Nonroad Heavy-Duty Engines," in
Clean Air Technology News, Winter 1997, p. 1 (Docket A-98-01; item II-A-02).
8. "It's Not Easy Being Green," Modern Materials Handling, April 2000 (Docket A-2000-01;
item II-A-06).
9. Letter from William Platz, Western Propane Gas Association, January 24, 2001 (Docket
A-2000-01; item II-D-40).
10. "It's Not Easy Being Green," Modern Materials Handling, April 2000 (Docket A-2000-01;
item II-A-06).
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11. "Nonroad Recreational Vehicle Technologies and Costs", Arthur D. Little - Acurex
Environmental, Draft Final Report, July 2001 (Docket A-2000-01, document H-A-31)..
12. "Nonroad Recreational Vehicle Technologies and Costs", Arthur D. Little - Acurex
Environmental, Draft Final Report, July 2001 (Docket A-2000-01, document H-A-31).
13. "Nonroad Recreational Vehicle Technologies and Costs", Arthur D. Little - Acurex
Environmental, Draft Final Report, July 2001 (Docket A-2000-01, document H-A-31).
14. Brake-specific fuel consumption (BSFC) based on 4-stroke BSFC estimates provided by
Power Systems Research.
15. "Monthly Energy Review", Calendar year 2000 average Refiner Prices of Pertroleum
Products to End Users (Cents per gallon, excluding taxes), Energy Information Administration.
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Chapter 5: Estimated Costs
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Chapter 6: Emissions Inventory
CHAPTER 6: Emissions Inventory
6.1 Methodology
The following chapter presents our analysis of the emission impact of the proposed
standards for recreational marine, large spark-ignition equipment, snowmobiles, all-terrain
vehicles, and off-highway motorcycles. We first present an overview of the methodology used to
generate the emissions inventories, followed by a discussion of the specific information used in
generating the inventories for each of the regulated categories of engines as well as the emission
inventories. Emissions from a typical piece of equipment are also presented.
6.1.1 Off-highway Exhaust Emissions
We are in the process of developing an emission model that will calculate emissions
inventories for most off-highway vehicle categories, including those in this rule. This draft
model is called NONROAD. For this effort we use the most recent version of the draft
NONROAD model publicly available with some updates that we anticipate will be included in
the next draft release. This section gives a brief overview of the calculation methodology used in
NONROAD for calculating exhaust emission inventories. Inputs and results specific to each of
the off-highway categories in this rule are discussed in more detail later in this chapter. For more
detailed information on the draft NONROAD model, see our website at
www. epa.gov/otaq/nonrdmdl . htm .
For the inventory calculations in this rule, each class of off-highway engines was divided
into power ranges to distinguish between technology or usage differences in each category. Each
of the engine applications and power ranges were modeled with distinct annual hours of
operation, load factors, and average engine lives. The basic equation for determining the exhaust
emissions inventory, for a single year, from off-highway engines is shown below:
Emissions = ^ (population x now erx load 'x annual use x emission factor] (Eq.6-l}
ranges^ ^ r j > \ i >
This equation sums the total emissions for each of the power ranges for a given calendar
year. "Population" refers to the number of engines estimated to be in the U.S. in a given year.
"Power" refers to the population-weighted average rated power for a given power range. Two
usage factors are included; "load" is the ratio between the average operational power output and
the rated power, and "annual use" is the average hours of operation per year. Emission factors
are applied on a brake-specific basis (g/kW-hr) and represent the weighted value between levels
from baseline and controlled engines operating in a given calendar year. Exhaust emission
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Draft Regulatory Support Document
inventories were calculated for HC, CO, and NOx from all engines and additionally for PM from
compression-ignition engines. Although some of the proposed emission standards combine HC
and NOx, it is useful to consider the HC and NOx emission impacts separately. (As described
throughout this document, the proposed standards for all-terrain vehicles (ATVs) and off-
highway motorcycles are based on a chassis test, with the standards proposed in grams per
kilometer. For these two categories of equipment, the equation used by the NONROAD model
for calculating emissions is similar to Equation 6-1 except that the "load factor" and "power"
terms are not included in the calculation, the "annual use" is input on a miles/year basis, and the
"emission factors" are entered on a gram per mile basis.)
To be able to determine the mix between baseline and controlled engines, we need to
determine the turnover of the fleet. Through the combination of historical population and
scrappage rates, historical sales and retirement of engines can be estimated. We use a normalized
scrappage rate and fit it to the data for each engine type on average operating life. Figure 6.1.1-1
presents the normalized scrappage curve used in the draft NONROAD model. For further
discussion of this scrappage curve, see our report titled "Calculation of Age Distributions —
Growth and Scrappage," (NR-007).
Figure 6.1.1-1: Normalized Scrappage Curve
0 0.5 1 1.5 2
Engine Age Normalized by Average Useful Life
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Chapter 6: Emissions Inventory
6.1.2 Off-highway Evaporative Emissions
Evaporative emissions refer to hydrocarbons released into the atmosphere when gasoline,
or other volatile fuels, evaporate from a vehicle. For this analysis, we model three types of
evaporative emissions:
- diurnal: These emissions are due to temperature changes throughout the day. As the
day gets warmer, the fuel heats up and begins to evaporate.
- refueling: These emissions are the vapors displaced from the fuel tank when fuel is
dispensed into the tank.
- permeation: These emissions are due to fuel that works its way through the material
used in the fuel system. Permeation is most common through plastic fuel tanks and
rubber hoses.
We are currently in the process of revising the inputs to the calculations for evaporative
emissions in the draft NONROAD model. The analysis for this rule includes the inputs that we
anticipate will be used in the draft NONROAD model. Because diurnal and refueling emissions
are dependent on ambient temperatures and fuel properties which vary through the nation and
through the year, we divided the nation into six regions and modeled each region individually for
each day of the year. The daily temperatures by region are based on a report which summarizes a
survey of dispensed fuel and ambient temperatures in the United States.1
For diurnal emission estimates, we used the Wade-Reddy equations2'3'4 to calculate grams
of hydrocarbons emitted per day per volume of fuel tank capacity. The Wade-Reddy equations
are well established and are used in both the MOBILE and draft NONROAD models with an
adjustment based on empirical data. These calculations are a function of vapor space, fuel vapor
pressure, and daily temperature variation and are as follows:
Vapor space (ft3) = ((1 - tank fill) x tank size + 3) / 7.841 (Eq. 6-2)
where:
tank fill = fuel in tank/fuel tank capacity
tank size = fuel tank capacity in gallons
T! (°F) = (Tmax - Tmin) x 0.922 + Tmin (Eq. 6-3)
where:
Tmax = maximum diurnal temperature (°F)
Tmin = minimum diurnal temperature (°F)
V100 (psi) = 1.0223 x RVP + [(0.0357 X RVP)/(1-0.0368 x RVP)] (Eq. 6-4)
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where:
V100 = vapor pressure at 100°F
RVP = Reid Vapor Pressure of the fuel
E100 (%) = 66.401-12.718 x V100 +1.3067 x V1002 - 0.077934 x V1003
+ 0.0018407 x V1004 (Eq. 6-5)
D^ (%) = E100 + [(262 / (0.1667 * E100 + 560) - 0.113] x (100 - Tmin) (Eq. 6-6a)
Dmax (%) = E100 + [(262 / (0.1667 * E100 + 560) - 0.113] x (100 - T\) (Eq. 6-6b)
where:
Dmin/max = distillation percent at the max/min temperatures in the fuel tank
E100 = percent of fuel evaporated at 100°F from equation 6-5
P! (psi) = 14.697 - 0.53089 x D^H- 0.0077215 x Dmin2 - 0.000055631 x Dmin3
+ 0.0000001769 x Dmin4 (Eq. 6-1 a)
PF (psi) = 14.697 - 0.53089 x Dmax + 0.0077215 x Dmax2 - 0.000055631 x Dmax3
+ 0.0000001769 x Dmax4 (Eq. 6-1 a)
Density (Ib/gal) = 6.386 - 0.0186 x RVP (Eq. 6-8)
MW (Mb mole) = (73.23 - 1.274 x RVP) + [0.5 x( Tmin + Tx) - 60] x 0.059 (Eq. 6-9)
Diurnal emissions (grams) = vapor space x 454 x density x [520 / (690 - 4 x MW)]
x 0.5 x [Pj / (14.7 - PT) + PF / (14.7 - PF)]
x [(14.7 - Pj) / (Tmin + 460) - (14.7 - PF) / (Tx + 460)] (Eq. 6-10)
where:
MW = molecular weight of hydrocarbons from equation 6-9
PI/F = initial and final pressures from equation 6-7
Because these calculations were developed and verified using automotive sized fuel
tanks, we ran the above equations for a 20 gallon fuel tank and then divided by 20 gallons to get
emission factors on a gram per gallon basis. This ensures that the vapor space calculation gives a
reasonable result.
We used the draft NONROAD model to determine the amount of fuel consumed by
spark-ignition marine engines. To calculate refueling emissions, we used an empirical equation
to calculate grams of vapor displaced during refueling events. This equation was developed
based on testing of 22 highway vehicles under various refueling scenarios and in the benefits
calculations for our onboard refueling vapor recovery rulemaking for cars and trucks.5 These
calculations are a function of fuel vapor pressure, ambient temperature, and dispensed fuel
6-4
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Chapter 6: Emissions Inventory
temperature. The refueling vapor generation equation is as follows:
Refueling vapor (g/gal) = EXP(-1.2798 - 0.0049 x (Td - Ta) + 0.0203 x Td + 0.1315 x RVP)
(Eq. 6-11)
where:
Td = dispensed fuel temperature (°F)
Ta = ambient fuel temperature (°F)
RVP = Reid Vapor Pressure of the fuel
Title 40, Section 80.27 of the Code of Federal Regulations specifies the maximum
allowable fuel vapor pressure allowed for each state in the U.S. for each month of the year. We
used these limits as an estimate of fuel vapor pressure in our calculations.
We are not aware of a model that will allow us to calculate fuel permeation from nonroad
equipment. However we have limited data on the permeability of plastic fuel tanks and rubber
hoses. Based on this data, and a distribution of fuel tank sizes, materials, and assumed hose
lengths, we were able to estimate evaporative emissions due to permeation.
6.2 Effect of Emission Controls by Engine/Vehicle Type
The remainder of this chapter discusses the inventory results for each of the classes of
engines/vehicles included in this document. These inventory projections include both exhaust
and evaporative emissions. Also, this section describes inputs and methodologies used for the
inventory calculations that are specific to each engine/vehicle class.
6.2.1 Compression-Ignition Recreational Marine
We projected the annual tons of exhaust HC, CO, NOx, and PM from CI recreational
marine engines using the draft NONROAD model discussed above. This section describes
inputs to the calculations that are specific to CI recreational marine engines then presents the
results. These results are for the nation as a whole and include baseline and control inventory
projections.
6.2.1.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the calculations for CI recreational marine exhaust
emissions. These inputs are load factor, annual use, average operating life, and population.
Based on data collected in developing the draft NONROAD model, we use a load factor of 35
percent and an annual usage factor of 200 hours. We use an average operating life of 20 years for
engines below 225 kW and 30 years for larger engines. The draft NONROAD model includes
current and projected engine populations. Table 6.2.1-1 presents these population estimates for
selected years.
6-5
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Draft Regulatory Support Document
Table 6.2.1-1
Projected CI Recreational Marine Population by Year
Year
population
2000
167,000
2005
193,000
2010
219,000
2020
272,000
2030
326,000
We used the data presented in Chapter 4 to develop the baseline emission factors. For the
control emission factors, we assumed that the manufacturers would design their engines to meet
the proposed standard at regulatory useful life with a small compliance margin. (The regulatory
useful life is the period of time for which a manufacturer must demonstrate compliance with the
emission standards.) To determine the HC and NOx split for the proposed standards, we used
the HC and NOx data presented in Chapter 4 from CI recreational marine engines near the
proposed standards. Consistent with our modeling of heavy-duty highway emissions, we
assumed a compliance margin of 8 percent. This compliance margin is based on historical
practices for highway and nonroad engines with similar technology. Engine manufacturers give
themselves some cushion below the certification level on average so that engine-to-engine
variability will not cause a significant number of engines to exceed the standard. Also, we used
the deterioration factors in the draft NONROAD model. Table 6.2.1-2 presents the emission
factors used in this analysis for new engines and for engines deteriorated to the regulatory useful
life (10 years).
Table 6.2.1-2
Emission Factors for CI Recreational Marine Engines
Engine
Technology
baseline
controlled:
< 0.9 liters/cylinder
0.9-1. 2 liters/cylinder
> 1.2 liters/cylinder
HC[g/kW-hr]
new lOyrs
0.295 0.304
0.183 0.184
0.183 0.184
0.183 0.184
NOx [g/kW-hr]
new lOyrs
8.94 9.06
6.72 6.76
6.40 6.44
6.40 6.44
CO [g/kW-hr]
new lOyrs
1.27 1.39
1.27 1.39
1.27 1.39
1.27 1.39
PM[g/kW-hr]
new lOyrs
0.219 0.225
0.219 0.225
0.219 0.225
0.181 0.184
In our analysis of the CI recreational marine engine emissions inventory, we may
underestimate emissions, especially PM, due to engine deterioration in-use. We believe that
current modeling only represents properly maintained engines, but may not be representative of
in-use tampering or malmaintenance. However, we have not fully evaluated the limited data
currently available and we are in the process of collecting more data on in-use emission
deterioration. Once this has been completed we will decide whether or not we need to update our
deterioration rates both in this analysis and in the Draft NONROAD model.
6-6
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Chapter 6: Emissions Inventory
6.2.1.2 Reductions Due to the Proposed Standard
We anticipate that the proposed standards will result in a 41 percent reduction in
HC+NOx and a 22 percent reduction in PM from new engines. Because of the long lives of these
engines, even in 2030 the only about half of the fleet will be turned over to the new engines. For
this reason the reductions in 2030 are only about 26 percent HC+NOx and 9 percent PM. We are
not claiming any benefits from the proposed cap on CO emissions. The following charts and
tables present our projected exhaust emission inventories for CI recreational marine engines and
the anticipated emission reductions.
Figure 6.2.1-1: Projected National HC from CI Recreational Marine Engines
1,800
1,600
1,400
a 1,200
o
+-
r
o
O
X
1,000
800
600
400
200
• Baseline
Controlled
2000 2005 2010 2015 2020
calendar year
2025
2030
Table 6.2.1-3
Projected HC Reductions for CI Recreational Marine Engines [short tons]
Calendar Year
2000
2005
2010
2020
2030
Baseline
800
920
1,040
1,300
1,550
Control
800
920
940
970
970
Reduction
0
0
100
330
580
% Reduction
0%
0%
10%
25%
38%
6-7
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Draft Regulatory Support Document
Figure 6.2.1-2: Projected National NOx from CI Recreational Marine Engines
50 000
AC. nnn
40 000
T oc nnn
0)
"S ^0 000
*- oc nno
o
•c ?n ooo -
(/)
>< -15 000
z
10 000
5 000 -
n
Jk-*-^
^^r^^
^^•^^^
^^r^-^^ } c,; H !-! - - i • ^ ^ ' • } '- ; • "
r _^ }1, -^r^' '' " " '"
2000
-—t— Baseline
: Controlled
2005 2010
•i
2015 2020 2025 2030
calendar year
Table 6.2.1-4
Projected NOx Reductions for CI Recreational Marine Engines [short tons]
Calendar Year
2000
2005
2010
2020
2030
Baseline
23,700
27,400
31,200
38,800
46,300
Control
23,700
27,400
29,000
32,000
34,500
Reduction
0
0
2,110
6,760
11,800
% Reduction
0%
0%
7%
17%
26%
6-8
-------
Chapter 6: Emissions Inventory
Figure 6.2.1-4: Projected National PM from CI Recreational Marine Engines
2 000
1 800
1 ROO
r-i -1 400
<0
<]>
> 1 ono
-35 1 ,^UU -
c
O -i nnn
t
2 800 ^]
iHL
^T 600
0.
400
900
n
_^^-rf^-< - J" ! ^" '"
, ! - «*"< r"* i"
J = = • : !
2000
» Baseline
; Controlled
2005 2010
;
2015 2020 2025 2030
calendar year
Table 6.2.1-6
Projected PM Reductions for CI Recreational Marine Engines [short tons]
Calendar Year
2000
2005
2010
2020
2030
Baseline
900
1,040
1,180
1,470
1,760
Control
900
1,040
1,160
1,390
1,600
Reduction
0
0
20
80
160
% Reduction
0%
0%
2%
6%
9%
6.2.1.3 Per Vessel Emissions from CI Recreational Marine Engines
This section describes the development of the HC plus NOx emission estimates on a per
engine basis over the average lifetime of typical CI recreational marine engines. As in the cost
analysis in Chapter 5, we look at three engine sizes for this analysis (100, 400, and 750 kW) as
well as a composite of all engine sizes. The emission estimates were developed to estimate the
cost per ton of the proposed standards as presented in Chapter 7.
The new and deteriorated emission factors used to calculate the HC and NOx emissions
from typical CI recreational marine engines were presented in Table 6.2.1-2. A brand new
engine emits at the zero-mile level presented in the table. As the engine ages, the emission levels
6-9
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Draft Regulatory Support Document
increase based on the pollutant-specific deterioration factor. The load factor for these engines is
estimated to be 0.35, the annual usage rate is estimated to be 200 hours per year, and the average
lifetime is estimated to be 20 years for engines less than 225 kW and 30 years for larger engines.
Using the information described above and the equation used for calculating emissions
from nonroad engines (see Equation 6-1), we calculated the lifetime HC+NOx emissions from
typical marine engines both baseline and controlled engines. Table 6.2.1-7 presents these results
with and without the consideration of a 7 percent per year discount on the value of emission
reductions.
Table 6.2.1-7
Lifetime HC+NOx Emissions from Typical CI Recreational Marine Engines (tons)
Engine
Size
lOOkW
400 kW
750 kW
Composite
Baseline
Undiscounted
1.44
8.65
16.2
5.64
Discounted
0.82
3.82
7.16
2.58
Control
Undiscounted
1.01
6.08
11.4
3.96
Discounted
0.57
2.69
5.04
1.81
Reduction
Undiscounted
0.43
2.57
4.84
1.68
Discounted
0.24
1.13
2.12
0.76
6.2.1.4 Crankcase Emissions from CI Recreational Marine Engines
We anticipate some benefits in HC, NOx, and PM from the closed crankcase
requirements for CI recreational marine engines. Based on limited engine testing, we estimate
that crankcase emissions of HC and PM diesel engines are each about 0.013 g/kW-hr.6 NOx data
varies, but crankcase NOx emissions may be as high as HC and PM. Therefore, we use the same
crankcase emission factor of 0.01 g/bhp-hr for each of the three constituents.
For this analysis, we assume that manufacturers will use the low cost option of routing
crankcase emissions to the exhaust and including them in the total exhaust emissions when the
engine is designed to the standards. Because exhaust emissions would have to be reduced
slightly to offset any crankcase emissions, the crankcase emission control is functionally
equivalent to a 100 percent reduction in crankcase emissions.
The engine data we use to determine crankcase emission levels is based on new heavy-
duty engines. We do not have data on the effect of in-use deterioration of crankcase emissions.
However, we expect that these emissions would increase as the engine wears. Therefore, this
analysis may underestimate the benefits that would result from our crankcase emission
requirements. Table 6.2.1-8 presents our estimates of the reductions crankcase emissions from
CI recreational marine engines.
6-10
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Chapter 6: Emissions Inventory
Table 6.2.1-8
Crankcase Emissions Reductions from CI Recreational Marine Engines
Calendar Year
2000
2005
2010
2020
2030
HC+NOx
0
0
17
63
113
PM
0
0
8
32
56
6.2.2 Large Spark-Ignition Equipment
6.2.2.1 Exhaust Emissions from Large SI Equipment
We projected the annual tons of exhaust HC, CO, and NOx from large industrial spark-
ignition (SI) engines using the draft NONROAD model described above. This section describes
inputs to the calculations that are specific to these engines then presents the results of the
modeling.
6.2.2.1.1 Inputs for Exhaust Inventory Calculations
Several usage inputs are specific to the calculations for Large SI engines. These inputs
are load factor, annual use, average operating life, and population. Because the Large SI category
is made up of many applications, the NONROAD model contains application-specific
information for each of the applications making up the Large SI category. Table 6.2.2-1 presents
the inputs used in the NONROAD model for each of the Large SI applications. (The average
operating life for a given application can vary within an application by power category. In such
cases, the average operating life value presented in Table 6.2.2-1 is based on the average
operating life estimate for the engine with the average horsepower listed in the table.)
The NONROAD model generally uses population data based on information from Power
Systems Research, which is based on historical sales information adjusted according to survival
and scrappage rates. We are, however, using different population estimates for forklifts based on
a recent market study.7 That study identified a 1996 population of 491,321 for Class 4 through 6
forklifts, which includes all forklifts powered by internal combustion engines. Approximately 80
percent of those were estimated to be fueled by propane, with the rest running on either gasoline
or diesel fuel. Assuming an even split between gasoline and diesel for these remaining forklifts
leads to a total population of spark-ignition forklifts of 442,000. The NONROAD model
therefore uses this estimate for the forklift population, which is significantly higher than that
estimated by Power Systems Research. Table 6.2.2-1 shows the estimated population figures
used in the NONROAD model for each application, adjusted for the year 2000.
The split between LPG and gasoline in various applications warrants further attention.
6-11
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Draft Regulatory Support Document
Engines are typically sold without fuel systems, which makes it difficult to assess the distribution
of engines sales by fuel type. Also, engines are often retrofitted for a different fuel after a period
of operation, making it still more difficult to estimate the prevalence of the different fuels. The
high percentage of propane systems for forklifts, compared with about 60 percent estimated by
Power Systems Research, can be largely attributed to expenses related to maintaining fuel
supplies. LPG cylinders can be readily exchanged with minimal infrastructure cost as compared
to gasoline storage. Natural gas systems typically offer the advantage of pipeline service, but the
cost of installing high-pressure refueling equipment is an obstacle to increased use of natural gas
systems.
Some applications of nonroad SI equipment face much different refueling situations.
Lawn and garden equipment is usually not centrally fueled and therefore operates almost
exclusively on gasoline, which is more readily available. Agriculture equipment is
predominantly powered by diesel engines. Most of these operators likely have storage tanks for
diesel fuel. For those who use spark-ignition engines in addition to, or instead of, the diesel
models, we would expect them in many cases to be ready to invest in gasoline storage tanks as
well, resulting in little or no use of LPG or natural gas for those applications. For construction,
general industrial, and other equipment, there may be a mix of central and noncentral fueling, and
motive and portable equipment. We therefore believe that estimating an even mix of LPG and
gasoline for these engines is most appropriate. The approximate distribution of fuel types for the
individual applications used in the NONROAD model are listed in Table 6.2.2-1.
Table 6.2.2-1
Operating Parameters and Population Estimates for Various Large SI Applications
Application
Forklift
Generator
Commercial turf
Aerial lift
Pump
Welder
Baler
Air compressor
Scrubber/sweeper
Chipper/grinder
Swathers
Leaf blower/vacuum
Avg. Rated
HP
69
59
28
52
45
67
44
65
49
66
95
79
Load
Factor
0.30
0.68
0.60
0.46
0.69
0.58
0.62
0.56
0.71
0.78
0.52
0.94
Hours
per Year
1800
115
682
361
221
408
68
484
516
488
95
282
Average
Operating
Life (yrs)
8.3
25.0
3.7
18.1
9.8
12.7
25.0
11.1
4.1
7.9
25.0
11.3
2000
Population
504,696
146,246
55,433
38,901
35,981
19,246
18,659
17,472
13,363
13,015
12,060
11,797
Percent
LPG/CNG
95
100
0
50
50
50
0
50
50
50
0
0
6-12
-------
Chapter 6: Emissions Inventory
Application
Sprayers
Specialty vehicle/cart
Oil field equipment
Skid/steer loader
Other agriculture equipment
Irrigation set
Trencher
Rubber-tired loader
Other general industrial
Terminal tractor
Bore/drill rig
Concrete/industrial saw
Rough terrain forklift
Other material handling
Ag. tractor
Paver
Roller
Other construction
Crane
Pressure washer
Paving equipment
Aircraft support
Gas compressor
Front mowers
Other lawn & garden
Tractor/loader/backhoe
Hydraulic power unit
Surfacing equipment
Crushing/processing equip
Avg. Rated
HP
66
66
44
47
162
97
54
71
82
93
78
46
66
67
82
48
55
126
75
39
39
99
110
32
61
58
50
40
63
Load
Factor
0.65
0.58
0.90
0.58
0.55
0.60
0.66
0.71
0.54
0.78
0.79
0.78
0.63
0.53
0.62
0.66
0.62
0.48
0.47
0.85
0.59
0.56
0.60
0.65
0.58
0.48
0.56
0.49
0.85
Hours
per Year
80
65
1104
310
124
716
402
512
713
827
107
610
413
386
550
392
621
371
415
115
175
681
6000
86
61
870
450
488
241
Average
Operating
Life (yrs)
25.0
25.0
1.5
8.3
25.0
7.0
11.3
8.8
7.8
4.7
25.0
3.2
11.5
7.3
8.8
5.8
7.8
16.8
15.4
15.3
14.5
7.9
0.8
25.0
25.0
7.2
6.0
6.3
14.6
2000
Population
9,441
9,145
7,855
7,436
5,501
5,367
3,627
3,177
2,942
2,716
2,607
2,266
1,925
1,605
1,599
1,367
1,362
1,276
1,240
1,227
1,109
910
788
658
402
360
330
314
235
Percent
LPG/CNG
0
50
100
50
0
50
50
50
50
50
50
50
50
50
0
50
50
50
50
50
50
50
100
0
0
50
50
50
50
6-13
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Draft Regulatory Support Document
Application
Refrigeration/AC
Avg. Rated
HP
55
Load
Factor
0.46
Hours
per Year
605
Average
Operating
Life (yrs)
10.8
2000
Population
169
Percent
LPG/CNG
100
An additional issue related to population figures is the level of growth factored into
emission estimates for the future. The NONROAD model incorporates application-specific
growth figures based on projections from Power Systems Research. The model projects growth
rates separately for the different fuels for each application. Table 6.2.2-2 presents the population
estimates of Large SI engines (rounded to the nearest 1,000 units) by fuel type for selected years.
Table 6.2.2-2
Projected Large SI Population by Year
Category
Gasoline LSI
LPGLSI
CNGLSI
Total LSI
2000
225,000
653,000
89,000
967,000
2005
234,000
789,000
99,000
1,122,000
2010
244,000
927,000
110,000
1,281,000
2020
269,000
1,195,000
134,000
1,598,000
2030
298,000
1,440,000
158,000
1,896,000
Southwest Research Institute recently compiled a listing of test data from past and current
testing projects.8 These tests were all conducted on new or nearly new engines and are used in
the NONROAD model as zero-mile levels (ZML). Table 6.2.2-3 summarizes this test data. All
engines were operated on the steady-state ISO C2 duty cycle, except for two engines that were
tested on the steady-state D2 cycle. The results from the different duty cycles were comparable.
Lacking adequate test data for engines fueled by natural gas, we model those engines to have the
same emission levels as those fueled by liquefied petroleum gas (LPG), based on the similarity
between engines using the two fuels (in the case of hydrocarbon emissions, the equivalence is
based on non-methane hydrocarbons).
Emission levels often change as an engine ages. In most cases, emission levels increase
with time, especially for engines equipped with technologies for controlling emissions. We
developed deterioration factors for uncontrolled Large SI engines based on measurements with
comparable highway engines.9 Table 6.2.2-3 also shows the deterioration factors that apply at
the median lifetime estimated for each type of equipment. For example, a deterioration factor of
1.26 for hydrocarbons multiplied by the emission factor of 6.2 g/hp-hr for new gasoline engines
indicates that modeled emission levels increase to 7.8 g/hp-hr when the engine reaches its median
lifetime. The deterioration factors are linear multipliers, so the modeled deterioration at different
points can be calculated by simple interpolation.
6-14
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Chapter 6: Emissions Inventory
Emissions during transient operation can be significantly higher than during steady-state
operation. Based on emission measurements from highway engines comparable to uncontrolled
Large SI engines, we have measured transient emission levels that are 30 percent higher for HC
and 45 percent higher for CO relative to steady-state measurements.10 The NONROAD model
therefore multiplies steady-state emission factors by a transient adjustment factor (TAP) of 1.3
for HC and 1.45 for CO to estimate emission levels during normal, transient operation. Test data
do not support adjusting NOx emission levels for transient operation and so a TAP of 1.0 is used
for NOx emissions. Also, the model applies no transient adjustment factor for generators,
pumps, or compressors, since engines in these applications are less likely to experience transient
operation.
Table 6.2.2-3
Zero-Mile Level Emission Factors (g/hp-hr), Deterioration Factors (at Median Life)
and Transient Adjustment Factors for Pre-Control Large SI Engines
Fuel Category
Gasoline
LPG
CNG
THC
ZML
6.2
1.7
24.6
DF
1.26
1.26
1.26
TAP
1.3
1.3
1.3
CO
ZML
203.4
28.2
28.2
DF
1.35
1.35
1.35
TAP
1.45
1.45
1.45
NOx
ZML
7.1
12.0
12.0
DF
1.03
1.03
1.03
TAP
1.0
1.0
1.0
As manufacturers comply with the proposed Phase 1 emission standards for Large SI
engines, we expect the emission factors, deterioration factors and transient adjustment factors
will be affected. To estimate the Phase 1 deterioration factors, we relied upon deterioration
information for current Class lib heavy-duty gasoline engines developed for the MOBILE6
emission model. Class lib engines are the smallest heavy-duty engines and are comparable in
size to many Large SI engines. They also employ catalyst/fuel system technology similar to the
technologies we expect to be used on Large SI engines. To estimate the Phase 1 emission factors
at zero miles, we back-calculated the emission levels based on the proposed standards and the
estimated deterioration factors, assuming manufacturers will design to meet a level 10 percent
below the proposed standard to account for variability. Given that these engines will employ a
catalyst to meet the proposed standards, we believe a 10 percent compliance margin is
appropriate. (Including a margin of compliance below the standards is a practice that
manufacturers have followed historically to provide greater assurance that their engines would
comply in the event of a compliance audit.) Because the proposed standards include an
HC+NOx standard, we assumed the HC/NOx split would stay the same as pre-control engines (at
the end of the regulated useful life). Table 6.2.2-4 presents the zero-mile levels, deterioration
factors used in the analysis of today's proposed Phase 1 standards for Large SI engines. The
Phase 1 standards are proposed to take effect in 2004 for all engines.
The transient adjustment factors for Phase 1 engines were based on testing performed at
Southwest Research Institute on engines that are similar to those expected to be certified under
6-15
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Draft Regulatory Support Document
the proposed Phase 1 standards. The testing was performed on one gasoline fueled engine and
two LPG-fueled engines. A complete description of the testing performed and the results of the
testing is summarized in the docket for the rulemaking.11 Because we did not have any test
results for CNG-fueled engines, the same transient adjustment factors for LPG-fueled engines
were used.
Table 6.2.2-4
Zero-Mile Level Emission Factors (g/hp-hr), Deterioration Factors (at Median Life)
and Transient Adjustment Factors for Phase 1 Large SI Engines
Fuel Category
Gasoline
LPG
CNG
THC
ZML
0.85
0.25
3.7
DF
1.64
1.64
1.64
TAF
1.7
2.9
2.9
CO
ZML
24.5
24.5
24.5
DF
1.36
1.36
1.36
TAF
1.7
1.45
1.45
NOx
ZML
1.1
2.1
2.1
DF
1.15
1.15
1.15
TAF
1.4
1.5
1.5
In a similar manner, as manufacturers comply with the proposed Phase 2 emission
standards for Large SI engines, we expect the emission factors, deterioration factors and transient
adjustment factors will be affected. To estimate the Phase 2 deterioration factors, we relied upon
the same information noted above for Phase 1 engines. The technologies used to comply with
the proposed Phase 2 standards are expected to be further refinements of the technologies we
expect to be used on Phase 1 Large SI engines. For that reason, we are applying the Phase 1
deterioration factors to the Phase 2 engines. To estimate the Phase 2 emission factors at zero
miles, we back-calculated the emission levels based on the proposed standards and the estimated
deterioration factors, assuming manufacturers will design to meet a level 10 percent below the
proposed standard to account for variability. Given that these engines will employ a catalyst to
meet the proposed standards, we believe a 10 percent compliance margin is appropriate.
(Including a margin of compliance below the standards is a practice that manufacturers have
followed historically to provide greater assurance that their engines would comply in the event of
a compliance audit.) Again, because the proposed standards include an HC+NOx standard, we
assumed the HC/NOx split would stay the same as pre-control engines (at the end of the
regulated useful life). Table 6.2.2-5 present the zero-mile levels, deterioration factors used in the
analysis of today's proposed Phase 2 standards for Large SI engines. The Phase 2 standards are
proposed to take effect in 2004 for all engines.
Under the proposed Phase 2 program for Large SI engines, the test procedure will be
switched from a steady-state test to a transient test. Therefore, the in-use emission performance
of Phase 2 engines should be similar to the emissions performance over the test cycle. For this
reason, the transient adjustment factors for Phase 2 engines is set at 1.0 for all pollutants.
6-16
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Chapter 6: Emissions Inventory
Table 6.2.2-5
Zero-Mile Level Emission Factors (g/hp-hr), Deterioration Factors (at Median Life)
and Transient Adjustment Factors for Phase 2 Large SI Engines
Fuel Category
Gasoline
LPG
CNG
THC
ZML
0.3
3.1
0.2
DF
1.64
1.64
1.64
TAF
1.0
1.0
1.0
CO
ZML
13.2
1.7
1.7
DF
1.36
1.36
1.36
TAF
1.0
1.0
1.0
NOx
ZML
0.4
1.7
1.8
DF
1.15
1.15
1.15
TAF
1.0
1.0
1.0
6.2.2.1.2 Exhaust Emission Reductions Due to the Proposed Standards
Tables 6.2.2-6 through 6.2.2-8 present the projected HC, CO, and NOx exhaust emissions
inventories respectively, assuming engines remain uncontrolled and assuming we adopt the
proposed Phase 1 and Phase 2 standards. The tables also contain estimated emission reductions
for each of the pollutants. We anticipate that the proposed standards will result in a 87%
reduction in exhaust HC, 84% reduction in NOx, and a 92% reduction in CO.
Table 6.2.2-6
Projected HC Inventories and Reductions for Large SI Engines (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
177,000
193,000
212,000
252,000
291,000
Control
177,000
149,000
77,000
32,000
32,000
Reduction
0
44,000
135,000
220,000
259,000
% Reduction
0
23
64
87
89
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Table 6.2.2-7
Projected CO Inventories and Reductions for Large SI Engines (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
2,294,000
2,454,000
2,615,000
2,991,000
3,364,000
Control
2,294,000
2,155,000
1,152,000
231,000
168,000
Reduction
0
299,000
1,463,000
2,760,000
3,196,000
% Reduction
0
12
56
92
95
Table 6.2.2-8
Projected NOx Inventories and Reductions for Large SI Engines (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
306,000
351,000
397,000
486,000
565,000
Control
306,000
282,000
152,000
77,000
83,000
Reduction
0
69,000
245,000
409,000
483,000
% Reduction
0
20
62
84
85
6.2.2.2 Evaporative and Crankcase Emission Control from Large SI Equipment
We projected the annual tons of hydrocarbons evaporated into the atmosphere from Large
SI gasoline engines using the methodology discussed above in Section 6.1.2. These evaporative
emissions include diurnal and refueling emissions. Although the proposed standards do not
specifically require the control of refueling emissions, we have included them in the modeling for
completeness. We have also calculated estimates of hot-soak and running losses for Large SI
gasoline engines using separate information on those emissions. Finally, we present crankcase
emissions for all Large SI engines based on the NONROAD model. This section describes
inputs to the calculations that are specific to Large SI engines and presents our baseline and
controlled national inventory projections for evaporative and crankcase emissions.
6.2.2.2.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the evaporative emission calculations for Large SI
engines. These inputs are fuel tank sizes, population, and distribution throughout the nation.
The draft NONROAD model includes current and projected engine populations for each state
and we used this distribution as the national fuel tank distribution. Table 6.2.2-9 presents the
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Chapter 6: Emissions Inventory
population of Large SI gasoline engines for 1998.
Table 6.2.2-9
1998 Population of Large SI Engines by Region
Region
Northeast
Southeast
Southwest
Midwest
West
Northwest
Total
Total
106,000
46,600
27,600
42,500
34,700
11,200
269,000
The draft NONROAD model breaks this engine distribution further into ranges of engine
sizes. For each of these power ranges we apply a fuel tank size for our evaporative emission
calculations based on the fuel tank sizes used in the NONROAD model.
Table 6.2.2-10 presents the baseline diurnal emission factors for the certification test
conditions and a typical summer day with low vapor pressure fuel and a half-full tank.
Table 6.2.2-10
Diurnal Emission Factors for Test Conditions and Typical Summer Day
Evaporative Control
baseline
72-96 °F, 9RVP*Fuel, 40% fill
2.3 g/gallon/day
60-84 °F, 8RVP*Fuel, 50% fill
0.84 g/gallon/day
* Reid Vapor Pressure
We used the draft NONROAD model to determine the amount of fuel consumed by Large
SI gasoline engines. As detailed earlier in Table 6.2.2-1, the NONROAD model has annual
usage rates for all Large SI applications. Table 6.2.2-11 presents the fuel consumption estimates
we used in our modeling. For 1998, the draft NONROAD model estimated that Large SI
gasoline engines consumed about 300 million gallons of gasoline.
Table 6.2.2-11
Fuel Consumption Estimates used in Refueling Calculations for Large SI Gasoline Engines
Technology
Pre-control
Tier I/Tier 2
BSFC, Ib/hp-hr
0.605
0.484
To estimate inventories of hot-soak and running loss emissions from Large SI gasoline
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Draft Regulatory Support Document
engines, we applied a factor to the diurnal emissions inventory estimates based on evaporative
emission inventories prepared for the South Coast Air Quality Management District.12 The hot
soak inventory was estimated to be 3.9 times as high as the diurnal inventory, and the running
loss inventory was estimated to be two-thirds of the diurnal inventory. Finally, crankcase
emissions (from all Large SI engines) were generated using the draft NONROAD model.
Table 6.2.2-12 contains the baseline evaporative emission and crankcase emission
inventories for Large SI engines.
Table 6.2.2-12
Baseline Evaporative and Crankcase Emissions from Large SI Equipment [short tons]
Calendar
Year
2000
2005
2010
2020
2030
Diurnal
1,660
1,730
1,800
1,920
2,060
Refueling
1,250
1,300
1,350
1,450
1,550
Hot-Soak
6,530
6,790
7,040
7,560
8,070
Running Loss
1,100
1,150
1,190
1,280
1,360
Crankcase
58,280
63,620
69,690
82,760
95,870
6.2.2.2.2 Evaporative and Crankcase Emission Reductions Due to the Proposed
Requirements
We anticipate that the proposed evaporative emission requirements for Large SI engines
will result in approximately a 50% reduction in diurnal and running loss emissions, and a 90%
reduction in hot soak emissions. The proposed evaporative emission requirements are scheduled
to take effect in 2008 with the Tier 2 requirements. In addition, because the fuel consumption of
Large SI engines will be reduced by 20%, the refueling emissions will be reduced proportionally
as well. The refueling benefits will be realized beginning in 2004 as the Tier 1 standards take
effect. Finally, the proposed standards also require that engines have a closed crankcase. We
expect the crankcase emissions will be routed to the engine and combusted, nearly eliminating
crankcase emissions. For modeling purposes, we have assumed that the crankcase emissions are
reduced by 90%. The proposed crankcase requirements are schedule to take effect in 2004 with
the Tier 1 requirements.
Table 6.2.2-13 present the evaporative emission inventories and crankcase emissions
inventories for Large SI engines based on the reductions in emissions noted above. The
reductions are achieved over time as the fleet turns over to Phase 1 or Phase 2 engines. (The
control inventories were projected using a separate spreadsheet analysis. A copy of spreadsheet
calculating the control inventories has been placed in the docket for this rulemaking.13) Table
6.2.2-14 presents the corresponding reductions in evaporative and crankcase emissions for Large
SI engines due to the proposed requirements.
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Chapter 6: Emissions Inventory
Table 6.2.2-13
Control Case Evaporative and Crankcase Emissions from Large SI Equipment [short tons]
Calendar
Year
2000
2005
2010
2020
2030
Diurnal
1,660
1,730
1,370
1,070
1,060
Refueling
1,250
1,230
1,160
1,180
1,240
Hot-Soak
6,530
6,790
4,040
1,490
1,020
Running Loss
1,100
1,150
910
710
700
Crankcase
58,280
48,370
27,010
13,780
9,580
Table 6.2.2-14
Reductions in Evaporative and Crankcase Emissions from Large SI Equipment
[short tons]
Calendar
Year
2000
2005
2010
2020
2030
Diurnal
0
0
420
860
1,000
Refueling
0
70
180
270
310
Hot-Soak
0
0
3,000
6,070
7,050
Running Loss
0
0
280
570
660
Crankcase
0
15,240
42,680
68,970
86,240
6.2.2.3 Per Equipment Emissions from Large SI Equipment
The following section describes the development of the HC+NOx emission estimates on
a per piece of equipment basis over the average lifetime or typical Large SI piece of equipment.
The emission estimates were developed to estimate the cost per ton of the proposed standards as
presented in Chapter 7. The estimates are made for an average piece of Large SI equipment for
each of the three fuel groupings (gasoline, LPG, and CNG). Although the emissions vary from
one nonroad application to another, we are presenting the average numbers for the purpose of
determining the emission reductions associated with the proposed standards from a typical piece
of Large SI equipment over its lifetime.
In order to estimate the emission from a piece of Large SI equipment, information on the
emission level of the engine, the power of the engine, the load factor of the engine, the annual
hours of use of the engine, and the lifetime of the engine are needed. The values used to predict
the per piece of equipment emissions for this analysis and the methodology for determining the
values are described below.
The information necessary to calculate the HC and NOx emission levels of a piece of
equipment over the lifetime of a typical piece of Large SI equipment were presented in Table
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Draft Regulatory Support Document
6.2.2-3 through Table 6.2.2-5. A brand new piece of equipment emits at the zero-mile level
presented in the tables. As the equipment ages, the emission levels increase based on the
pollutant-specific deterioration factor. Deterioration, as modeled in the NONROAD model,
continues until the equipment reaches the median life of that equipment type. The deterioration
factors presented in Table 6.2.2-3 through Table 6.2.2-5 when applied to the zero-mile levels
presented in the same tables, represent the emission level of the engine at the end of its median
life. The emissions at any point in time in between can be determined through interpolation.
(For this analysis, the HC emissions from CNG engines is calculated on an NMHC+NOx basis,
with NMHC emissions estimated to be 4.08% of THC emissions.)
To estimate the average power for equipment in each of the Large SI fuel groupings, we
used the population estimates contained in the NONROAD model and the average horsepower
information presented in Table 6.2.2-1. To simplify the calculations, we used the most common
applications within each category that represent 80% or more of the fuel grouping population.
For gasoline engines, the top ten applications with the highest populations were used. For LPG
and CNG, the top four applications with the highest populations were used. Table 6.2.2-15 lists
the applications used in the analysis.
Table 6.2.2-15
Large SI Applications Used in Per Equipment Analysis
Gasoline
LPG
CNG
Commercial Turf Equipment
Balers
Forklifts
Aerial Lifts
Pumps
Swathers
Leafbl owers/Vacuum s
Sprayers
Welders
Air Compressors
Forklifts
Generator Sets
Aerial Lifts
Pumps
Forklifts
Generator Sets
Other Oil Field Equipment
Irrigation Sets
Based on the applications noted above for each fuel, we calculated the population-
weighted average horsepower for Large SI equipment to be 51.6 hp for gasoline equipment, 65.7
hp for LPG equipment, and 64.6 hp for CNG equipment.
To estimate the average load factor for equipment in each of the Large SI fuel groupings,
we used the population estimates contained in the NONROAD model and the load factors as
presented in Table 6.2.2-1. As noted above, to simplify the calculations, we used the most
common applications within each category that represent 80% or more of the fuel grouping
population. Based on the most populous applications noted above, we calculated the population-
weighted average load factor for Large SI equipment to be 0.58 for gasoline equipment, 0.39 for
LPG equipment, and 0.49 for CNG equipment.
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Chapter 6: Emissions Inventory
To estimate the average annual hours of use for equipment in each of the Large SI fuel
groupings, we used the population estimates contained in the NONROAD model and the hours
per year levels as presented in Table 6.2.2-1. As noted above, to simplify the calculations, we
used the most common applications within each category that represent 80% or more of the fuel
grouping population. Based on the most populous applications noted above, we calculated the
population-weighted average annual hours of use for Large SI equipment to be 536 hours for
gasoline equipment, 1365 hours for LPG equipment, and 1161 hours for CNG equipment.
Finally, to estimate the average lifetime for equipment in each of the Large SI fuel
groupings, we used the population estimates contained in the NONROAD model and the average
operating life information as presented in Table 6.2.2-1. As noted above, to simplify the
calculations, we used the most common applications within each category that represent 80% or
more of the fuel grouping population. Based on the most populous applications noted above, we
calculated the population-weighted average lifetime for Large SI equipment to be 12.3 years for
gasoline equipment, 12 years for LPG equipment, and 13 years for CNG equipment.
Using the information described above and the equation used for calculating emissions
from nonroad equipment (see Equation 6-1), we calculated the lifetime HC+NOx emissions from
typical Large SI equipment for both pre-control engines and engines meeting the proposed Phase
1 and Phase 2 standards. Table 6.2.2-16 presents the lifetime HC+NOx emissions for Large SI
equipment on both an undiscounted and discounted basis (using a discount rate of 7 percent).
Table 6.2.2-17 presents the corresponding lifetime HC+NOx emission reductions for the
proposed Phase 1 and Phase 2 standards.
Table 6.2.2-16
Lifetime HC+NOx Emissions from Typical Large SI Equipment (tons)*
Control
Level
Pre-control
Phase 1
Phase 2
Gasoline
Un-
discounted
3.51
0.75
0.17
Discounted
2.44
0.51
0.12
LPG
Un-
discounted
6.80
1.86
0.97
Discounted
4.79
1.30
0.68
CNG
Un-
discounted
7.06
1.83
1.07
Discounted
4.85
1.24
0.73
* For CNG engines only, the emissions are calculated on the basis of NMHC+NOx.
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Draft Regulatory Support Document
Table 6.2.2-17
Lifetime HC+NOx Emission Reductions from Typical Large SI Equipment (tons)*
Control
Increment
Pre-control
to Phase 1
Phase 1 to
Phase 2
Gasoline
Un-
discounted
2.76
0.58
Discounted
1.93
0.39
LPG
Un-
discounted
4.94
0.89
Discounted
3.69
0.62
CNG
Un-
discounted
5.23
0.76
Discounted
3.61
0.51
* For CNG engines only, the reductions are calculated on the basis of NMHC+NOx.
6.2.3 Snowmobiles
We projected the annual tons of exhaust HC, and CO from snowmobiles using the draft
NONROAD model discussed above. This section describes inputs to the calculations that are
specific to snowmobiles then presents the results. These results are for the nation as a whole and
include baseline and control inventory projections.
6.2.3.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the calculations for snowmobile exhaust emissions.
These inputs are load factor, annual use, average operating life, and population. Based on data
developed for our Final Finding for recreational equipment and Large SI equipment, we use a
load factor of 34 percent, an annual usage factor of 57 hours and an average operating life of 9
years for snowmobiles.14 The draft NONROAD model includes current and projected engine
populations. Table 6.2.3-1 presents these population estimates (rounded to the nearest 1,000
units) for selected years.
Table 6.2.3-1
Projected Snowmobile Populations by Year
Year
population
2000
1,571,000
2005
1,619,000
2010
1,677,000
2020
1,803,000
2030
1,931,000
The baseline emission factors and deterioration factors (for pre-control engines) were
developed for the Final Finding as noted above. For the control emission factors (i.e., engines
complying with the Phase 1 or Phase 2 standards), we assumed that the manufacturers would
design their engines to meet the proposed standards at regulatory useful life with a small
compliance margin. (Because we are not proposing a NOx standard for snowmobiles, we have
assumed that NOx levels will remain at the pre-control levels for both Phase 1 and Phase 2
snowmobile engines.) For both set of proposed standards for snowmobiles, we assumed a
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Chapter 6: Emissions Inventory
compliance margin of 20 percent to account for variability. (The proposed standards for
snowmobiles are not based on the use of catalysts. Engine out emissions tend to have more
variability than the emissions coming from an engine equipped with a catalyst. For this reason,
we are using a compliance margin of 20 percent. As noted earlier, including a margin of
compliance below the standards is a practice that manufacturers have followed historically to
provide greater assurance that their engines would comply in the event of a compliance audit.)
Because the proposed standards for snowmobiles are expected to be met by mostly improved 2-
stroke designs, we assumed that the deterioration rates would stay the same as the deterioration
rates for pre-control engines. Table 6.2.3-2 presents the emission factors used in this analysis for
new engines and the maximum deterioration factors applied to snowmobiles operated out to their
median lifetime. (For the calculations, the zero-mile levels were determined based on the pro-
rated amount of deterioration expected at the regulatory lifetime, which is 300 hours for
snowmobiles. As noted earlier, the regulatory useful life is the period of time for which a
manufacturer must demonstrate compliance with the emission standards. The median lifetime of
in-use equipment is longer than the regulatory life.)
Table 6.2.3-2
Zero-Mile Level Emission Factors (g/hp-hr) and Deterioration Factors (at Median
Lifetime) for Snowmobile Engines
Engine Category
Baseline/Pre-control
Control/Phase 1
Control/Phase 2
THC
ZML
111
75
56
MaxDF
1.2
1.2
1.2
CO
ZML
296
205
148
MaxDF
1.2
1.2
1.2
NOx
ZML
0.9
0.9
0.9
MaxDF
1.0
1.0
1.0
The Phase 1 standards are proposed to take effect in 2006 for all engines. The Phase 2
standards are proposed to take effect in 2010 for all engines.
6.2.3.2 Reductions Due to the Proposed Standards
We anticipate that the proposed standards for snowmobiles will result in a 63 percent
reduction in both HC and CO by the year 2020. We do not expect any reduction in NOx
emissions from snowmobiles under the proposed program. Tables 6.2.3-3 and 6.2.3.-4 present
our projected HC and CO exhaust emission inventories for snowmobiles and the anticipated
emission reductions from the proposed Phase 1 and Phase 2 standards. Table 6.2.3-5 presents the
projected NOx emission inventories from snowmobiles.
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Draft Regulatory Support Document
Table 6.2.3-3
Projected HC Inventories and Reductions for Snowmobiles (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
200,000
205,000
213,000
229,000
245,000
Control
200,000
205,000
155,000
85,000
88,000
Reduction
0
0
58,000
144,000
157,000
% Reduction
0
0
27
63
64
Table 6.2.3-4
Projected CO Inventories and Reductions for Snowmobiles (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
531,000
547,000
567,000
609,000
653,000
Control
531,000
547,000
415,000
227,000
234,000
Reduction
0
0
152,000
382,000
419,000
% Reduction
0
0
27
63
64
Table 6.2.3-5
Projected NOx Inventories for Snowmobiles (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
1,000
1,000
1,000
2,000
2,000
6.2.3.3 Per Equipment Emissions from Snowmobiles
The following section describes the development of the HC and CO emission estimates
on a per piece of equipment basis over the average lifetime or a typical snowmobile. The
emission estimates were developed to estimate the cost per ton of the proposed standards as
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Chapter 6: Emissions Inventory
presented in Chapter 7.
In order to estimate the emission from a snowmobile, information on the emission level
of the engine, the power of the engine, the load factor of the engine, the annual hours of use of
the engine, and the lifetime of the engine are needed. The values used to predict the per piece of
equipment emissions for this analysis and the methodology for determining the values are
described below.
The information necessary to calculate the HC and CO emission levels of a piece of
equipment over the lifetime of a typical snowmobile were presented in Table 6.2.3-2. A brand
new snowmobile emits at the zero-mile level presented in the table. As the snowmobile ages, the
emission levels increase based on the pollutant-specific deterioration factor. Deterioration, as
modeled in the NONROAD model, continues until the equipment reaches the median life. The
deterioration factors presented in Table 6.2.3-2 when applied to the zero-mile levels presented in
the same table, represent the emission level of the snowmobile at the end of its median life. The
emissions at any point in time in between can be determined through interpolation.
To estimate the average power for snowmobiles, we used the population and power
distribution information contained in the NONROAD model and determined the population-
weighted average horsepower for snowmobiles. The population-weighted horsepower for
snowmobiles was calculated to be 48.3 hp.
As described earlier in this section, the load factor for snowmobiles is estimated to be
0.34, the annual usage rate is estimated to be 57 hours per year, and the average lifetime is
estimated to be 9 years.
Using the information described above and the equation used for calculating emissions
from nonroad equipment (see Equation 6-1), we calculated the lifetime HC and CO emissions
from a typical snowmobile for both pre-control engines and engines meeting the proposed Phase
1 and Phase 2 standards. Table 6.2.3-6 presents the lifetime HC and CO emissions for a typical
snowmobile on both an undiscounted and discounted basis (using a discount rate of 7 percent).
Table 6.2.3-7 presents the corresponding lifetime HC and CO emission reductions for the
proposed Phase 1 and Phase 2 standards.
Table 6.2.3-6
Lifetime HC and CO Emissions from a Typical Snowmobile (tons)
Control Level
Pre-control
Phase 1
Phase 2
HC
Undiscounted
1.15
0.55
0.41
Discounted
0.88
0.43
0.31
CO
Undiscounted
3.05
1.51
1.09
Discounted
2.34
1.16
0.84
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Table 6.2.3-7
Lifetime HC and CO Emission Reductions from a Typical Snowmobile (tons)
Control Increment
Pre-control to Phase 1
Phase 1 to Phase 2
HC
Undiscounted
0.60
0.14
Discounted
0.45
0.12
CO
Undiscounted
1.54
0.42
Discounted
1.18
0.32
6.2.4 All-Terrain Vehicles
6.2.4.1 Exhaust Emissions from All-Terrain Vehicles
We projected the annual tons of exhaust HC, CO, and NOx, from all-terrain vehicles
(ATVs) using the draft NONROAD model discussed above. This section describes inputs to the
calculations that are specific to ATVs then presents the results. These results are for the nation
as a whole and include baseline and control inventory projections.
6.2.4.1.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the calculations for ATV exhaust emissions. These
inputs are annual use, average operating life, and population. Based on data developed for our
Final Finding for recreational equipment and Large SI equipment, we use an annual usage factor
of 7,000 miles and an average operating life of 13 years for ATVs.15 (Because the ATV
standards are chassis-based standard instead of engine-based, the NONROAD model has been
revised to model ATVs on the basis of gram per mile emission factors and annual mileage
accumulation rates. Load factor is not needed for such calculations.)
The draft NONROAD model includes current and projected engine populations. Table
6.2.4-1 presents these population estimates (rounded to the nearest 1,000 units) for selected
years. The ATV population growth rates used in the NONROAD model have been updated to
reflect the expected growth in ATV populations based on historic ATV sales information and
sales growth projections supplied by the Motorcycle Industry Council (MIC), an industry trade
organization. The growth rates were developed separately for 2-stroke and 4-stroke ATVs.
Based on the sales information from MIC, sales of ATVs have been growing substantially
throughout the 1990s, averaging 25% growth per year over the last 6 years. MIC estimates that
growth in sales will continue for the next few years, although at lower levels often percent or
less, with no growth in sales projected by 2005. Combining the sales history, growth projections,
and information on equipment scrappage, we have estimated that the population of ATVs will
grow significantly through 2010, and then grow as much lower levels. (The population of 2-
stroke ATVs presented in Table 6.2.4-1 are for baseline population estimates. Under the
proposed ATV standards, 2-stroke designs are expected to be phased-out as they are converted to
4-stroke designs.)
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Chapter 6: Emissions Inventory
Table 6.2.4-1
Projected ATV Populations by Year
Category
4-stroke ATVs
2-stroke ATVs*
All ATVs
2000
3,776,000
673,000
4,449,000
2005
5,513,000
1,457,000
6,970,000
2010
7,223,000
2,057,000
9,280,000
2020
8,460,000
2,424,000
10,884,000
2030
8,540,000
2,445,000
10,985,000
* - The projected population estimates for 2-stroke ATVs are for baseline calculations only.
Under the proposed Phase 1 standards, we expect all 2-stroke engines will be converted to 4-
stroke designs.
The baseline emission factors used in the NONROAD model for ATVs have been
updated based on recent testing of ATVs and Off-highway motorcycles as presented in Chapter 4
(sections 4.6 and 4.7). The baseline deterioration factors (for pre-control engines) were
developed for the Final Finding as noted above. For the control emission factors (i.e., engines
complying with the Phase 1 or Phase 2 standards), we assumed that the manufacturers would
design their engines to meet the proposed standards at regulatory useful life with a small
compliance margin. Because we are proposing a HC+NOx standard for ATVs, we have assumed
that the HC/NOx split will remain the same as the pre-control HC/NOx split for Phase 1. For
Phase 2 ATVs, we assumed the technologies expected to be used by the manufacturers would
result in HC control, and so the Phase 2 NOx emission factor was kept at the Phase 1 level. For
the Phase 1 standards for ATVs, we assumed a compliance margin of 20 percent to account for
variability. For the Phase 2 standards for ATVs, we assumed a compliance margin of 20 percent
to account for variability if a catalyst was not being used, and a compliance margin of 10 percent
if a catalyst was being used. (Engine out emissions tend to have more variability than the
emissions coming from an engine equipped with a catalyst. For this reason, we are using
different compliance margins for catalyst and non-catalyst ATVs. As noted earlier, including a
margin of compliance below the standards is a practice that manufacturers have followed
historically to provide greater assurance that their engines would comply in the event of a
compliance audit.) Because the proposed standards for ATVs are expected to be met by 4-stroke
designs, we assumed that the deterioration rates would stay the same as the deterioration rates for
pre-control 4-stroke ATVs. Table 6.2.4-2 presents the emission factors used in this analysis for
new ATVs and the maximum deterioration factors for ATVs which applies at the median
lifetime. (For the calculations, the zero-mile levels were determined based on the pro-rated
amount of deterioration expected at the regulatory lifetime, which is 18,640 miles (30,000
kilometers) for ATVs. As noted earlier, the regulatory useful life is the period of time for which
a manufacturer must demonstrate compliance with the emission standards. The median lifetime
of in-use equipment is longer than the regulatory life. As noted earlier, the regulatory useful life
is the period of time for which a manufacturer must demonstrate compliance with the emission
standards. The median lifetime of in-use equipment is longer than the regulatory life.) For the
Phase 2 standards, we have assumed that half of the ATVs will be engine recalibration and half
of the engines will be recalibration plus a catalyst.
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Table 6.2.4-2
Zero-Mile Level Emission Factors (g/mi) and Deterioration Factors (at Median Lifetime)
for ATVs
Engine Category
Baseline/Pre-control
2-stroke
Baseline/Pre-control
4-stroke
Control/Phase 1
4-stroke
Control/Phase 2 -
4-stroke plus Engine
Recalibration
Control/Phase 2 -
4-stroke plus Engine
Recalib rati on/C ataly st
THC
ZML
55.7
2.2
2.2
1.2
0.8
MaxDF
1.2
1.15
1.15
1.15
1.15
CO
ZML
52.7
48.3
31.1
31.1
31.1
MaxDF
1.2
1.17
1.17
1.17
1.17
NOx
ZML
0.15
0.34
0.31
0.31
0.31
MaxDF
1.0
1.0
1.0
1.0
1.0
The Phase 1 standards are proposed to be phased in at 50% in 2007 and 100% in 2008.
The Phase 2 standards are proposed to be phased in at 50% in 2010 and 100% in 2011.
However, because there are a significant number of small volume manufacturers that produce 2-
stroke ATVs, and because we have proposed compliance flexibilities for such manufacturers, we
have modeled the phase in of the proposed standards for the current 2-stroke ATVs based on the
schedule contained in Table 6.2.4-3.
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Table 6.2.4-3
Assumed Phase-In Schedule for Current 2-Stroke ATVs Used in the Modeling Runs
Model Year
2005
2006
2007
2008
2009
2010
2011
2012
Pre-control
2-stroke
100%
65%
30%
15%
0%
0%
0%
0%
Phase 1
4-stroke
0%
35%
70%
85%
65%
30%
15%
0%
Phase 2
4-stroke plus
Recalibration
0%
0%
0%
0%
17.5%
35%
42.5%
50%
Phase 2
4-stroke plus
Recalibration
and Catalyst
0%
0%
0%
0%
17.5%
35%
42.5%
50%
6.2.4.1.2 Reductions Due to the Proposed Standards
We anticipate that the proposed standards for ATVs will result in a 84% reduction in HC
and a 34% reduction in CO by the year 2020. As manufacturers convert their engines from 2-
stroke to 4-stroke design, we expect there could be a minimal increase in NOx. (Because the
amount of increase in the NOx inventory is so small, it is within the roundoff presented in the
table below. Therefore, only the baseline NOx inventory is shown.) Tables 6.2.4-4 through
6.2.4.-6 present our projected HC, CO, and NOx, exhaust emission inventories for ATVs and the
anticipated emission reductions from the proposed Phase 1 and Phase 2 standards.
Pro
Table 6.2.4-4
ected HC Inventories and Reductions for ATVs (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
381,000
771,000
1,098,000
1,301,000
1,317,000
Control
381,000
771,000
756,000
205,000
96,000
Reduction
0
0
342,000
1,096,000
1,221,000
% Reduction
0
0
31
84
93
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Table 6.2.4-5
Projected CO Inventories and Reductions for ATVs (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
1,860,000
2,903,000
3,901,000
4,589,000
4,641,000
Control
1,860,000
2,903,000
3,380,000
3,041,000
2,939,000
Reduction
0
0
521,000
1,548,000
1,702,000
% Reduction
0
0
13
34
37
Table 6.2.4-6
Projected NOx Inventories for ATVs (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
11,000
16,000
21,000
25,000
25,000
6.2.4.2 Evaporative Emissions from All-Terrain Vehicles
We projected the annual tons of hydrocarbons evaporated into the atmosphere from
ATVs using the methodology discussed above in Section 6.1.2. These evaporative emissions
include diurnal and refueling emissions. Although the proposed standards do not specifically
require the control of refueling emissions, we have included them in the modeling for
completeness. This section describes inputs to the calculations that are specific to ATVs and
presents our baseline national inventory projections for evaporative emissions from ATVs.
6.2.4.2.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the calculations of evaporative emissions from ATVs.
These inputs are fuel tank sizes, population, and distribution throughout the nation. The draft
NONROAD model includes current and projected engine populations for each state and we used
this distribution as the national fuel tank distribution. Table 6.2.4-7 presents the population of
ATVs for 1998.
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Chapter 6: Emissions Inventory
Table 6.2.4-7
1998 Population of ATVs by Region
Region
Northeast
Southeast
Southwest
Midwest
West
Northwest
Total
Total
1,420,000
1,010,000
363,000
457,000
423,000
249,000
3,930,000
The draft NONROAD model breaks this engine distribution further into ranges of engine
sizes. For each of these power ranges we apply a fuel tank size for our evaporative emission
calculations based on the fuel tank sizes used in the NONROAD model.
Table 6.2.4-8 presents the baseline diurnal emission factors for the certification test
conditions and a typical summer day with low vapor pressure fuel and a half-full tank.
Table 6.2.4-8
Diurnal Emission Factors for Test Conditions and Typical Summer Day
Evaporative Control
baseline
72-96 °F, 9RVP*Fuel, 40% fill
2.3 g/gallon/day
60-84 °F, 8RVP*Fuel, 50% fill
0.84 g/gallon/day
* Reid Vapor Pressure
We used the draft NONROAD model to determine the amount of fuel consumed by
ATVs. As detailed earlier in this section, the NONROAD model has an annual usage rate for
ATVs of 7,000 miles/year. Table 6.2.4-9 presents the fuel consumption estimates we used in our
modeling. For 1998, the draft NONROAD model estimated that ATVs consumed about 1.4
billion gallons of gasoline.
Table 6.2.4-9
Fuel Consumption Estimates used in Refueling Calculations for ATVs
Technology
Pre-control 2-stroke
Pre-control 4-stroke
BSFC, Ib/mi
0.197
0.332
Table 6.2.4-10 contains the diurnal and refueling emission inventories for ATVs.
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Table 6.2.4-10
Projected Diurnal and Refueling Emissions from ATVs [short tons]
Calendar Year
2000
2005
2010
2020
2030
Diurnal
2,910
4,690
6,280
7,270
7,440
Refueling
6,100
9,280
12,200
13,800
14,000
6.2.4.3 Per Equipment Emissions from All-Terrain Vehicles
The following section describes the development of the HC+NOx emission estimates on
a per piece of equipment basis over the average lifetime or a typical ATV. The emission
estimates were developed to estimate the cost per ton of the proposed standards as presented in
Chapter 7.
In order to estimate the emissions from an ATV, information on the emission level of the
vehicle, the annual usage rate of the engine, and the lifetime of the engine are needed. The
values used to predict the per piece of equipment emissions for this analysis and the methodology
for determining the values are described below.
The information necessary to calculate the HC and NOx emission levels of a piece of
equipment over the lifetime of a typical ATV were presented in Table 6.2.4-2. A brand new
ATV emits at the zero-mile level presented in the table. As the ATV ages, the emission levels
increase based on the pollutant-specific deterioration factor. Deterioration, as modeled in the
NONROAD model, continues until the equipment reaches the median life. The deterioration
factors presented in Table 6.2.4-2 when applied to the zero-mile levels presented in the same
table, represent the emission level of the ATV at the end of its median life. The emissions at any
point in time in between can be determined through interpolation. (The emissions for Phase 2
ATVs are based on a 50/50 weighting of the "engine recalibration" and the "engine recalibration
plus catalyst" technologies presented in Table 6.2.4-2.)
As described earlier in this section, the annual usage rate for an ATV is estimated to be
7,000 miles per year and the average lifetime is estimated to be 13 years.
Using the information described above and the equation used for calculating emissions
from nonroad equipment modified to remove the power and load variables (see Equation 6-1),
we calculated the lifetime HC+NOx emissions from a typical ATV for both pre-control engines
(shown separately for 2-stroke and 4-stroke engines and a composite weighted value) and engines
meeting the proposed Phase 1 and Phase 2 standards. Table 6.2.4-10 presents the lifetime
HC+NOx emissions for a typical ATV on both an undiscounted and discounted basis (using a
discount rate of 7 percent). Table 6.2.4-11 presents the corresponding lifetime HC+NOx
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Chapter 6: Emissions Inventory
emission reductions for the proposed Phase 1 and Phase 2 standards.
Table 6.2.4-10
Lifetime HC+NOx Emissions from a Typical ATV (tons)
Control Level
Pre-control (2-stroke)
Pre-control (4-stroke)
Pre-control (Composite)
Phase 1
Phase 2
HC+NO
Undiscounted
6.16
0.28
1.58
0.28
0.14
X
Discounted
4.19
0.19
1.07
0.19
0.10
Table 6.2.4-11
Lifetime HC+NOx Emission Reductions from a Typical ATV (tons)
Control Increment
Pre-control (Composite) to Phase 1
Phase 1 to Phase 2
HC+NOx
Undiscounted
1.30
0.14
Discounted
0.88
0.09
6.2.5 Off-highway Motorcycles
6.2.5.1 Exhaust Emissions from Off-highway Motorcycles
We projected the annual tons of exhaust HC, CO, and NOx, from off-highway
motorcycles using the draft NONROAD model discussed above. This section describes inputs to
the calculations that are specific to off-highway motorcycles then presents the results. These
results are for the nation as a whole and include baseline and control inventory projections.
6.2.5.1.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the calculations for off-highway motorcycles exhaust
emissions. These inputs are annual use, average operating life, and population. Based on data
developed for our Final Finding for recreational equipment and Large SI equipment, we use an
annual usage factor of 2,400 miles and an average operating life of 9 years for off-highway
motorcycles.16 (Because the off-highway motorcycle standards are chassis-based standard
instead of engine-based, the NONROAD model has been revised to model off-highway
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Draft Regulatory Support Document
motorcycles on the basis of gram per mile emission factors and annual mileage accumulation
rates. Load factor is not needed for such calculations.)
The draft NONROAD model includes current and projected engine populations. Table
6.2.5-1 presents these population estimates (rounded to the nearest 1,000 units) for selected
years. (The population of 2-stroke off-highway motorcycles presented in Table 6.2.5-1 are for
baseline population estimates. Under the proposed off-highway motorcycle standards, non-
competition 2-stroke designs are expected to be phased-out as they are converted to 4-stroke
designs. Competition models will remain 2-stroke designs.)
Table 6.2.5-1
Projected Off-Highway Motorcycle Populations by Year
Category
4-stroke
Off-highway
Motorcycles
2-stroke
Off-highway
Motorcycles*
All
Off-highway
Motorcycles
2000
397,000
805,000
1,202,000
2005
410,000
832,000
1,242,000
2010
425,000
862,000
1,287,000
2020
457,000
928,000
1,385,000
2030
489,000
993,000
1,482,000
* - The projected population estimates for 2-stroke off-highway motorcycles are for baseline
calculations only. Under the proposed standards, we expect all non-competition 2-strokes will be
converted to 4-stroke designs. All 2-stroke competition models are assumed to remain 2-strokes.
The baseline emission factors used in the NONROAD model for off-highway
motorcycles have been updated based on recent testing of off-highway motorcycles and off-
highway motorcycles as presented in Chapter 4 (sections 4.6 and 4.7). The baseline deterioration
factors (for pre-control engines) were developed for the Final Finding as noted above. For the
control emission factors (i.e., Phase 1 off-highway motorcycles), we assumed that the
manufacturers would design their engines to meet the proposed standards at regulatory useful life
with a small compliance margin. Because we are proposing a HC+NOx standard for off-highway
motorcycles, we have assumed that the Phase 1 HC/NOx split will remain the same as the pre-
control HC/NOx split. For the Phase 1 standards for off-highway motorcycles, we assumed a
compliance margin of 20 percent to account for variability. (Including a margin of compliance
below the standards is a practice that manufacturers have followed historically to provide greater
assurance that their engines would comply in the event of a compliance audit.) Because the
proposed standards for off-highway motorcycles are expected to be met by 4-stroke designs, we
assumed that the deterioration rates would stay the same as the deterioration rates for pre-control
4-stroke off-highway motorcycles. Table 6.2.5-2 presents the emission factors used in this
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Chapter 6: Emissions Inventory
analysis for new off-highway motorcycles and the maximum deterioration factors applied to off-
highway motorcycles operated out to their median lifetime. (For the calculations, the zero-mile
levels were determined based on the pro-rated amount of deterioration expected at the regulatory
lifetime, which is 6,210 miles (10,000 kilometers) for off-highway motorcycles. As noted
earlier, the regulatory useful life is the period of time for which a manufacturer must demonstrate
compliance with the emission standards. The median lifetime of in-use equipment is longer than
the regulatory life.)
Table 6.2.5-2
Zero-Mile Level Emission Factors (g/mi) and Deterioration Factors (at Median Lifetime)
for Off-Highway Motorcycles
Engine Category
Baseline/Pre-control
2-stroke*
Baseline/Pre-control
4-stroke
Control/Phase 1
4-stroke
THC
ZML
55.7
2.2
2.2
MaxDF
1.2
1.15
1.15
CO
ZML
52.7
48.3
30.7
MaxDF
1.2
1.17
1.17
NOx
ZML
0.15
0.34
0.31
MaxDF
1.0
1.0
1.0
* - Competition models are assumed to remain at pre-control levels under the proposed program
for off-highway motorcycles.
The Phase 1 standards are proposed to be phased in at 50% in 2007 and 100% in 2008.
However, because there are a significant number of small volume manufacturers that produce
off-highway motorcycles (who can take advantage of proposed compliance flexibilities), and
because competition off-highway motorcycles are exempt from the proposed standards, we have
modeled the phase in of the proposed standards for off-highway motorcycles based on the
schedule contained in Table 6.2.5-3.
Table 6.2.5-3
Assumed Phase-In Schedule for Current Off-Highway Motorcycles
Used in the Modeling Runs
Model Year
2005
2006
2007
Current 4-stroke
Off-highway Motorcycles
Pre-control
100%
56%
12%
Phase 1
0%
44%
88%
Current 2-stroke
Off-highway Motorcycles
Pre-control
100%
76%
53%
Phase 1
0%
24%
47%
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Model Year
2008
2009+
Current 4-stroke
Off-highway Motorcycles
Pre-control
6%
0%
Phase 1
94%
100%
Current 2-stroke
Off-highway Motorcycles
Pre-control
49%
46%
Phase 1
51%
54%
6.2.5.1.2 Reductions Due to the Proposed Standards
We anticipate that the proposed standards for off-highway motorcycles will result in a
22% reduction in HC and a 26% reduction in CO by the year 2020. As manufacturers convert
their engines from 2-stroke to 4-stroke design, we project there could be a small increase in NOx
inventories. (Because the amount of increase in the NOx inventory is so small, it is within the
roundoff presented in the table below. Therefore, only the baseline NOx inventory is shown.)
Tables 6.2.5-4 through 6.2.5.-6 present our projected HC, CO, and NOx, exhaust emission
inventories for off-highway motorcycles and the anticipated emission reductions from the
proposed Phase 1 standards. (The emission inventories presented below for off-highway
motorcycles include the competition motorcycles that would be exempt from the proposed
standards.)
Table 6.2.5-4
Projected HC Inventories and Reductions for Off-Highway Motorcycles (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
134,000
138,000
143,000
154,000
165,000
Control
134,000
138,000
112,000
77,000
81,000
Reduction
0
0
31,000
77,000
84,000
% Reduction
0
0
22
50
51
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Chapter 6: Emissions Inventory
Table 6.2.5-5
Projected CO Inventories and Reductions for Off-Highway Motorcycles (short tons)
Calendar Year
2000
2005
2010
2020
2030
Baseline
181,000
187,000
194,000
208,000
223,000
Control
181,000
187,000
172,000
154,000
164,000
Reduction
0
0
22,000
54,000
59,000
% Reduction
0
0
11
26
27
Table 6.2.5-6
Projected NOx Inventories for Off-Highway Motorcycles (short tons)
Calendar
Year
2000
2005
2010
2020
2030
Baseline
1,000
1,000
1,000
1,000
1,000
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6.2.5.2 Evaporative Emissions from Off-highway Motorcycles
We projected the annual tons of hydrocarbons evaporated into the atmosphere from off-
highway motorcycles using the methodology discussed above in Section 6.1.2. These
evaporative emissions include diurnal and refueling emissions. Although the proposed standards
do not specifically require the control of refueling emissions, we have included them in the
modeling for completeness. This section describes inputs to the calculations that are specific to
off-highway motorcycles and presents our baseline national inventory projections for evaporative
emissions from off-highway motorcycles.
6.2.5.2.1 Inputs for the Inventory Calculations
Several usage inputs are specific to the calculations of evaporative emissions from off-
highway motorcycles. These inputs are fuel tank sizes, population, and distribution throughout
the nation. The draft NONROAD model includes current and projected engine populations for
each state and we used this distribution as the national fuel tank distribution. Table 6.2.5-7
presents the population of off-highway motorcycles for 1998.
Table 6.2.5-7
1998 Population of Off-Highway Motorcycles by Region
Region
Northeast
Southeast
Southwest
Midwest
West
Northwest
Total
Total
427,000
304,000
109,000
137,000
127,000
75,000
1,180,000
The draft NONROAD model breaks this engine distribution further into ranges of engine
sizes. For each of these power ranges we apply a fuel tank size for our evaporative emission
calculations based on the fuel tank sizes used in the NONROAD model.
Table 6.2.5-8 presents the baseline diurnal emission factors for the certification test
conditions and a typical summer day with low vapor pressure fuel and a half-full tank.
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Chapter 6: Emissions Inventory
Table 6.2.5-8
Diurnal Emission Factors for Test Conditions and Typical Summer Day
Evaporative Control
baseline
72-96 °F, 9RVP*Fuel, 40% fill
2.3 g/gallon/day
60-84 °F, 8RVP*Fuel, 50% fill
0.84 g/gallon/day
* Reid Vapor Pressure
We used the draft NONROAD model to determine the amount of fuel consumed by off-
highway motorcycles. As detailed earlier in this section, the NONROAD model has an annual
usage rate for off-highway motorcycles of 2,400 miles/year. Table 6.2.5-9 presents the fuel
consumption estimates we used in our modeling. For 1998, the draft NONROAD model
estimated that off-highway motorcycles consumed about 120 million gallons of gasoline.
Table 6.2.5-9
Fuel Consumption Estimates used in Refueling Calculations for Off-Highway Motorcycles
Technology
Pre-control 2-stroke
Pre-control 4-stroke
BSFC, Ib/mi
0.291
0.170
Table 6.2.5-10 contains the diurnal and refueling emission inventories for off-highway
motorcycles.
Table 6.2.5-10
Projected Diurnal and Refueling Emissions from Off-Highway Motorcycles [short tons]
Calendar Year
2000
2005
2010
2020
2030
Diurnal
800
830
860
920
980
Refueling
490
510
520
530
560
6.2.5.3 Per Equipment Emissions from Off-highway Motorcycles
The following section describes the development of the HC+NOx emission estimates on
a per piece of equipment basis over the average lifetime or a typical off-highway motorcycle.
The emission estimates were developed to estimate the cost per ton of the proposed standards as
presented in Chapter 7.
In order to estimate the emissions from an off-highway motorcycle, information on the
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Draft Regulatory Support Document
emission level of the vehicle, the annual usage rate of the engine, and the lifetime of the engine
are needed. The values used to predict the per piece of equipment emissions for this analysis and
the methodology for determining the values are described below.
The information necessary to calculate the HC and NOx emission levels of a piece of
equipment over the lifetime of a typical off-highway motorcycle were presented in Table 6.2.5-2.
A brand new off-highway motorcycle emits at the zero-mile level presented in the table. As the
off-highway motorcycle ages, the emission levels increase based on the pollutant-specific
deterioration factor. Deterioration, as modeled in the NONROAD model, continues until the
equipment reaches the median life. The deterioration factors presented in Table 6.2.5-2 when
applied to the zero-mile levels presented in the same table, represent the emission level of the
off-highway motorcycle at the end of its median life. The emissions at any point in time in
between can be determined through interpolation.
As described earlier in this section, the annual usage rate for an off-highway motorcycle
is estimated to be 2,400 miles per year and the average lifetime is estimated to be 9 years.
Using the information described above and the equation used for calculating emissions
from nonroad equipment modified to remove the power and load variables (see Equation 6-1),
we calculated the lifetime HC+NOx emissions from a typical off-highway motorcycle for both
pre-control engines (shown separately for 2-stroke and 4-stroke engines and a composite
weighted value) and engines under the proposed Phase 1 standards. (Competition bikes, which
are exempt from the proposed standards, are not included in the calculations.) Table 6.2.5-11
presents the lifetime HC+NOx emissions for a typical off-highway motorcycle on both an
undiscounted and discounted basis (using a discount rate of 7 percent). Table 6.2.5-12 presents
the corresponding lifetime HC+NOx emission reductions for the proposed Phase 1 standards.
Table 6.2.5-11
Lifetime HC+NOx Emissions from a Typical Off-highway Motorcycle (tons)*
Control Level
Pre-control (2-stroke)
Pre-control (4-stroke)
Pre-control (Composite)
Phase 1
HC+NO
Undiscounted
1.47
0.07
0.70
0.07
X
Discounted
1.13
0.05
0.53
0.05
* The emission estimates do not include competition off-highway motorcycles that remain at pre-
control emission levels.
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Chapter 6: Emissions Inventory
Table 6.2.5-12
Lifetime HC+NOx Emission Reductions from a Typical Off-highway Motorcycle (tons)*
Control Increment
Pre-control (Composite) to Phase 1
HC+NOx
Undiscounted
0.63
Discounted
0.48
* The reduction estimates do not include competition off-highway motorcycles that remain
uncontrolled, and therefore do not realize any emission reductions under the proposal.
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Chapter 6 References
1. API Publication No. 4278, "Summary and Analysis of Data from Gasoline Temperature
Survey Conducted at Service Stations by American Petroleum Institute," Prepared by Radian
Corporation for American Petroleum Institute, November 11, 1976, Docket A-2000-01,
Document II-A-16.
2. D. T. Wade, "Factors Influencing Vehicle Evaporative Emissions," SAE Paper 670126, 1967,
Docket A-2000-01, Document II-A-59.
3. Wade et. al., "Mathematical Expressions Relating Evaporative Emissions from Motor
Vehicles without Evaporative Loss-Control Devices to Gasoline Volatility," SAE Paper 72070,
1972, Docket A-2000-01, Document II-A-58.
4. S. Raghuma Reddy, "Prediction of Fuel Vapor Generation from a Vehicle Fuel Tank as a
Function of Fuel RVP and Temperature," SAE Paper 892089, 1989, Docket A-2000-01,
Document II-A-61.
5. "Final Regulatory Impact Analysis: Refueling Emission Regulations for Light Duty Vehicles
and Trucks and Heavy Duty Vehicles," U.S. EPA, January 1994, Docket A-2000-01.
6. Pagan, Jaime, "Investigation on Crankcase Emissions from a Heavy-Duty Diesel Engine,"
U.S. Environmental Protection Agency, March, 1997, Docket A-2000-01, Document II-A-70.
7."The Role of Propane in the Fork Lift/Industrial Truck Market: A Study of its Status, Threats,
and Opportunities," Robert E. Myers for the National Propane Gas Association, December 1996,
Docket A-2000-01.
8."Three-Way Catalyst Technology for Off-Road Equipment Powered by Gasoline and LPG
Engines—Final Report" Jeff J. White, et al, April 1999, p. 45, Docket A-2000-01, Document II-
A-08.
9."Revisions to the June 2000 Release of NONROAD to Reflect New Information and Analysis
on Marine and Industrial Engines," EPA memorandum from Mike Samulski to Docket A-98-01,
November 2, 2000, Docket A-2000-01, Document II-B-08.
10."Regulatory Analysis and Environmental Impact of Final emission Regulations for 1984 and
Later Model Year Heavy Duty Engines," U.S. EPA, December 1979, p. 189, Docket A-2000-01.
11. "Comparison of Transient and Steady-state Emissions for Gasoline and LPG Large Spark-
Ignition Engines," EPA memorandum from Alan Stout to Docket A-2000-01, September 2001,
Docket A-2000-01.
12. "Measurement of Evaporative Emissions from Off-Road Equipment," prepared for South
Coast Air Quality Management District by Southwest Research, November 1998, Docket A-
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Chapter 6: Emissions Inventory
2000-01, Document II-A-10.
13. "Spreadsheet for Predicting Evaporative and Crankcase Emission Inventories from Large SI
Engines Under the September 2001 Proposed Rule," EPA memorandum from Phil Carlson to
Docket A-2000-01, September 12, 2001.
14. Emission Modeling for Recreational Vehicles," EPA memorandum from Line Wehrly to
Docket A-98-01, November 13, 2000, Docket A-2000-01, Document H-B-19.
15. Emission Modeling for Recreational Vehicles," EPA memorandum from Line Wehrly to
Docket A-98-01, November 13, 2000, Docket A-2000-01, Document H-B-19.
16. Emission Modeling for Recreational Vehicles," EPA memorandum from Line Wehrly to
Docket A-98-01, November 13, 2000, Docket A-2000-01, Document H-B-19.
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Chapter 7: Cost per Ton
CHAPTER 7 Cost Per Ton
7.1 Cost Per Ton by Engine Type
7.1.1 Introduction
This chapter presents our estimate of the cost per ton of the various standards contained
in this proposal. The analysis relies on the costs estimates presented in Chapter 5 and the
estimated lifetime emissions reductions using the information presented in Chapter 6. The
chapter also presents a summary of the cost per ton of other recent EPA mobile source
rulemakings for comparison purposes. Finally, this chapter presents the estimated costs and
emission reductions as incurred over the first twenty years after the proposed standards are
implemented.
In calculating net present values that were used in our cost-per-ton estimates, we used a
discount rate of 7 percent, consistent with the 7 percent rate reflected in the cost-per-ton analyses
for other recent mobile source programs. OMB Circular A-94 requires us to generate benefit and
cost estimates reflecting a 7 percent rate. Using the 7 percent rate allows us to make direct
comparisons of cost-per-ton estimates with estimates for other, recently adopted, mobile source
programs.
However, we anticipate that the primary cost and cost-per-ton estimates for future
proposed mobile source programs will reflect a 3 percent rate. The 3 percent rate is in the 2 to 3
percent range recommended by the Science Advisory Board's Environmental Economics
Advisory Committee for use in EPA social benefit-cost analyses, a recommendation incorporated
in EPA's new Guidelines for Preparing Economic Analyses (November 2000). Therefore, we
have also calculated the overall cost-effectiveness of today's rule based on a 3 percent rate to
facilitate comparison of the cost-per-ton of this rule with future proposed rules which use the 3
percent rate. The results using both a 3 percent and 7 percent discount rate are provided in this
Chapter.
7.1.2 Compression-Ignition Recreational Marine
As described in Chapter 5, several of the anticipated engine technologies will result in
improvements in engine performance that go beyond emission control. While the cost estimates
described in Chapter 5 do not take into account the observed value of performance
improvements, these non-emission benefits should be taken into account in the calculation of
cost-effectiveness. We believe that an equal weighting of emission and non-emission benefits is
justified for those technologies which clearly have substantial non-emission benefits, namely
electronic controls, fuel injection changes, turbocharging, and aftercooling for diesel engines and
upgrading to electronic fuel injection for gasoline engines. For some or all of these technologies,
a greater value for the non-emission benefits could likely be justified. This has the effect of
7-1
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Draft Regulatory Support Document
halving the cost for those technologies in the cost-per-ton calculation. The cost-per-ton values in
this chapter are based on this calculation methodology.
Although the proposed rule will also result in PM reductions, we apply the total cost to
the ozone forming gases (HC and NOx) presented in Chapter 6 for these calculations. The
estimated per vessel costs presented in Chapter 5 change over time, with reduced costs in the
long term. We have estimated both a near-term and long-term cost per ton as presented in Table
7.1.2.-1 assuming a 7 percent discount rate. Table 7.1.2.-2 presents the cost per tons results
assuming a 3 percent discount rate..
Table 7.1.2.-1
Estimated CI Recreational Marine Cost Per Ton of HC + NOx Reduced
(7 percent discount rate)
100 kW near-term
100 kW long-term
400 kW near-term
400 kW long-term
750 kW near-term
750 kW long-term
Composite near-term
Composite long-term
Total Cost per
Vessel (NPV)
$475
$197
$384
$210
$707
$368
$443
$212
Lifetime Reductions
(NPV tons)
0.24
1.13
2.12
0.76
Discounted Per Vessel Cost
($/ton)
$1,963
$814
$339
$185
$334
$174
$560
$277
7-2
-------
Chapter 7: Cost per Ton
Table 7.1.2.-2
Estimated CI Recreational Marine Cost Per Ton of HC + NOx Reduced
(3 percent discount rate)
100 kW near-term
100 kW long-term
400 kW near-term
400 kW long-term
750 kW near-term
750 kW long-term
Composite near-term
Composite long-term
Total Cost per
Vessel (NPV)
$475
$197
$384
$210
$707
$368
$443
$212
Lifetime Reductions
(NPV tons)
0.33
1.73
3.24
1.15
Discounted Per Vessel Cost
($/ton)
$1,450
$600
$222
$122
$218
$114
$387
$185
7.1.3 Large Industrial SI Equipment
This section provides our estimate of the cost per ton of emissions reduced for large SI
engines >19 kW. We have calculated cost per ton on the basis of HC plus NOx for gasoline,
LPG and CNG engines. The analysis relies on the costs estimates in presented in Chapter 5 and
the estimated net present value of the per vehicle lifetime emissions reductions (tons) presented
in Chapter 6.
The estimated per vehicle costs presented in Chapter 5 change over time, with reduced
costs in the long term. We have estimated both a near-term and long-term cost per ton. In
addition, we have estimated cost per ton both with and without estimated fuel/maintenance
savings. We have estimated the cost per ton for both the Phase 1 and Phase 2 standards, with the
Phase 2 estimates incremental to Phase 1. The results of the analysis are presented in Tables
7.1.3.-1 through 7.1.3-3 for gasoline, LPG and CNG engines assuming a 7 percent discount rate.
The cost-per-ton results using a 3 percent discount rate follow in Tables 7.1.3.-4 through 7.1.3.-6.
7-3
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Draft Regulatory Support Document
Table 7.1.3.-1
Estimated Large SI Gasoline Engine >19 kW Cost Per Ton of HC+NOx Reduced
(7 percent discount rate)
Standard
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
(NPV)
$787
$507
$51
$20
Lifetime
Fuel/
Maintenance
Cost per
Vehicle
(NPV)
($3,257)
.
Lifetime
Reductions
(NPV tons)
1.9
0.4
Discounted Per
Vehicle Cost Per Ton
without
Fuel/Maintenance
Savings
($/ton)
$409
$264
$129
$51
Discounted Per
Vehicle Cost Per Ton
with
Fuel/Maintenance
Savings
($/ton)
($1,283)
($1,428)
$129
$51
7-4
-------
Chapter 7: Cost per Ton
Table 7.1.3.-2
Estimated Large SI LPG Engine >19 kW Cost Per Ton of HC+NOx Reduced
(7 percent discount rate)
Standard
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
(NPV)
$546
$354
$38
$14
Lifetime
Fuel/
Maintenance
Cost per
Vehicle
(NPV)
($4,554)
.
Lifetime
Reductions
(NPV tons)
3.5
0.6
Discounted Per
Vehicle Cost Per Ton
without
Fuel/Maintenance
Savings
($/ton)
$156
$101
$61
$23
Discounted Per
Vehicle Cost Per Ton
with
Fuel/Maintenance
Savings
($/ton)
($1,147)
($1,202)
$61
$23
7-5
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Draft Regulatory Support Document
Table 7.1.3.-3
Estimated Large SI CNG Engine >19 kW Cost Per Ton of HC+NOx Reduced
(7 percent discount rate)
Standard
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
(NPV)
$546
$354
$38
$14
Lifetime
Fuel/
Maintenance
Cost per
Vehicle
(NPV)
($1,648)
.
Lifetime
Reductions*
(NPV tons)
3.6
0.5
Discounted Per
Vehicle Cost Per Ton
without
Fuel/Maintenance
Savings
($/ton)
$151
$98
$74
$27
Discounted Per
Vehicle Cost Per Ton
with
Fuel/Maintenance
Savings
($/ton)
($306)
($359)
$74
$27
* The reductions are calculated on the basis of NMHC+NOx for CNG engines only.
Table 7.1.3.-4
Estimated Large SI Gasoline Engine >19 kW Cost Per Ton of HC+NOx Reduced
(3 percent discount rate)
Standard
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
(NPV)
$787
$507
$51
$20
Lifetime
Fuel/
Maintenance
Cost per
Vehicle
(NPV)
($3,940)
-
Lifetime
Reductions
(NPV tons)
2.3
0.5
Discounted Per
Vehicle Cost Per Ton
without
Fuel/Maintenance
Savings
($/ton)
$336
$217
$105
$41
Discounted Per
Vehicle Cost Per Ton
with
Fuel/Maintenance
Savings
($/ton)
($1,346)
($1,465)
$105
$41
7-6
-------
Chapter 7: Cost per Ton
Table 7.1.3.-5
Estimated Large SI LPG Engine >19 kW Cost Per Ton of HC+NOx Reduced
(3 percent discount rate)
Standard
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
(NPV)
$546
$354
$38
$14
Lifetime
Fuel/
Maintenance
Cost per
Vehicle
(NPV)
($5,489)
.
Lifetime
Reductions
(NPV tons)
4.2
0.8
Discounted Per
Vehicle Cost Per Ton
without
Fuel/Maintenance
Savings
($/ton)
$129
$84
$50
$19
Discounted Per
Vehicle Cost Per Ton
with
Fuel/Maintenance
Savings
($/ton)
($1,171)
($1,217)
$50
$19
Table 7.1.3.-6
Estimated Large SI CNG Engine >19 kW Cost Per Ton of HC+NOx Reduced
(3 percent discount rate)
Standard
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
(NPV)
$546
$354
$38
$14
Lifetime
Fuel/
Maintenance
Cost per
Vehicle
(NPV)
($2,005)
.
Lifetime
Reductions*
(NPV tons)
4.4
0.6
Discounted Per
Vehicle Cost Per Ton
without
Fuel/Maintenance
Savings
($/ton)
$124
$80
$60
$22
Discounted Per
Vehicle Cost Per Ton
with
Fuel/Maintenance
Savings
($/ton)
($331)
($374)
$60
$22
* The reductions are calculated on the basis of NMHC+NOx for CNG engines only.
7.1.4 Recreational Vehicles
This section provides our estimate of the cost per ton of emissions reduced for
recreational vehicles. We have calculated cost per ton on the basis of HC plus NOx for off-road
7-7
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Draft Regulatory Support Document
motorcycles and ATVs, and CO for snowmobiles. If reductions in other pollutants were
included, the cost per ton estimates would be lower. The analysis relies on the per vehicle costs
estimated in Chapter 5.2 and the estimated net present value of the per vehicle lifetime emissions
reductions (tons) presented in Chapter 6.
The estimated per vehicle costs presented in Chapter 5 change over time, with reduced
costs in the long term. We have estimated both a near-term and long-term cost per ton. In
addition, we have estimated cost per ton both with and without estimated fuel savings. For
ATVs and snowmobiles, we have estimated the cost per ton for both the Phase 1 and Phase 2
standards, with the Phase 2 estimates incremental to Phase 1. The results of the analysis using
the 7 percent discount rate are presented in Tables 7.1.4.-1 through Table 7.1.4.-3. The results
using the 3 percent discount rate follow in Tables 7.1.4.-4 through 7.1.4.-6.
Table 7.1.4.-1
Estimated Snowmobile Average Cost Per Ton of CO Reduced
(7 percent discount rate)
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
$55
$27
$216
$125
Lifetime Fuel
Cost per
Vehicle
(NPV)
($509)
Lifetime
Reductions
(NPV tons)
1.18
0.32
Discounted Per
Vehicle Cost Per Ton
without Fuel Savings
($/ton)
$50
$20
$670
$390
Discounted Per
Vehicle Cost Per Ton
with Fuel Savings
($/ton)
$50
$20
($910)
($1,200)
7-8
-------
Chapter 7: Cost per Ton
Table 7.1.4.-2
Estimated ATV Average Cost Per Ton of HC + NOx Reduced
(7 percent discount rate)
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
$60
$38
$52
$28
Lifetime Fuel
Cost per
Vehicle
(NPV)
($102)
Lifetime
Reductions
(NPV tons)
0.88
0.09*
Discounted Per
Vehicle Cost Per Ton
without Fuel Savings
($/ton)
$70
$40
$550
$300
Discounted Per
Vehicle Cost Per Ton
with Fuel Savings
($/ton)
($50)
($70)
$550
$300
: HC reductions only. We are not projecting a change in NOx emissions from the Phase 2 standard.
Table 7.1.4.-3
Estimated Off-highway Motorcycle Average Cost Per Ton of HC + NOx Reduced*
(7 percent discount rate)
near-term
long-term
Total Cost
per
Vehicle
$151
$94
Lifetime Fuel
Cost per
Vehicle
(NPV)
($98)
Lifetime
Reductions
(NPV tons)
0.48
Discounted Per
Vehicle Cost Per Ton
without Fuel Savings
($/ton)
$310
$190
Discounted Per
Vehicle Cost Per Ton
with Fuel Savings
($/ton)
$110
($10)
* non-competition models only
7-9
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Draft Regulatory Support Document
Table 7.1.4.-4
Estimated Snowmobile Average Cost Per Ton of CO Reduced
(3 percent discount rate)
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
$55
$27
$216
$125
Lifetime Fuel
Cost per
Vehicle
(NPV)
($621)
Lifetime
Reductions
(NPV tons)
1.36
0.37
Discounted Per
Vehicle Cost Per Ton
without Fuel Savings
($/ton)
$40
$20
$580
$330
Discounted Per
Vehicle Cost Per Ton
with Fuel Savings
($/ton)
$40
$20
($1,080)
($1,330)
Table 7.1.4.-5
Estimated ATV Average Cost Per Ton of HC + NOx Reduced
(3 percent discount rate)
Phase 1
near-term
Phase 1
long-term
Phase 2
near-term
Phase 2
long-term
Total Cost
per
Vehicle
$60
$38
$52
$28
Lifetime Fuel
Cost per
Vehicle
(NPV)
($131)
.
Lifetime
Reductions
(NPV tons)
1.08
0.12*
Discounted Per
Vehicle Cost Per Ton
without Fuel Savings
($/ton)
$60
$40
$450
$240
Discounted Per
Vehicle Cost Per Ton
with Fuel Savings
($/ton)
($70)
($90)
$450
$240
* HC reductions only. We are not projecting a change in NOx emissions from the Phase 2 standard.
7-10
-------
Chapter 7: Cost per Ton
Table 7.1.4.-6
Estimated Off-highway Motorcycle Average Cost Per Ton of HC + NOx Reduced*
(3 percent discount rate)
near-term
long-term
Total Cost
per
Vehicle
$151
$94
Lifetime Fuel
Cost per
Vehicle
(NPV)
($124)
Lifetime
Reductions
(NPV tons)
0.56
Discounted Per
Vehicle Cost Per Ton
without Fuel Savings
($/ton)
$270
$170
Discounted Per
Vehicle Cost Per Ton
with Fuel Savings
($/ton)
$50
($50)
* Non-competition models only
7.2 Cost Per Ton for Other Mobile Source Control Programs
Because the primary purpose of cost-effectiveness is to compare our program to
alternative programs, we made a comparison between the cost per ton values presented in this
chapter and the cost-effectiveness of other programs. Table 7.2-1 summarizes the cost
effectiveness of several recent EPA actions for controlled emissions from mobile sources.
Table 7.2-1
Cost-effectiveness of Previously Implemented
Mobile Source Programs (Costs Adjusted to 1997 Dollars)
Program
Tier 2 vehicle/gasoline sulfur
2007 Highway HD diesel
2004 Highway HD diesel
Off-highway diesel engine
Tier 1 vehicle
NLEV
Marine SI engines
On-board diagnostics
Marine CI engines
Won
1,340-2,260
1,458-1,867
212-414
425 - 675
2,054 - 2,792
1,930
1,171 - 1,846
2,313
24 - 176
By comparing the cost per ton values presented in presented earlier in this chapter to
those in Table 7.2-1, we can see that the cost effectiveness of the proposed standards for this
rulemaking fall within the range of these other programs. It is true that some previous programs
have been more cost efficient than the program we are proposing today. However, it should be
expected that the next generation of standards will be more expensive than the last, since the
least costly means for reducing emissions is generally pursued first.
7-11
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Draft Regulatory Support Document
The primary advantage of making comparisons to previously implemented programs is
that their cost-effectiveness values were based on a rigorous analysis and are generally accepted
as representative of the efficiency with which those programs reduce emissions. Unfortunately,
previously implemented programs can be poor comparisons because they may not be
representative of the cost-effectiveness of potential future programs. Therefore, in evaluating the
cost-effectiveness of our engine/diesel sulfur program, we also considered whether our proposal
is cost-effective in comparison with potential future means of controlling emissions. In the
context of the Agency's rulemaking which would have revised the ozone and PM NAAQS", the
Agency compiled a list of additional known technologies that could be considered in devising
new emission reductions strategies.1 Through this broad review, over 50 technologies were
identified that could reduce NOx, VOC, or PM. The cost-effectiveness of these technologies
averaged approximately $5,000/ton for VOC, $13,000/ton for NOx, and $40,000/ton for PM.
Although a $10,000/ton limit was actually used in the air quality analysis presented in the
NAAQS revisions rule, these values clearly indicate that, not only are future emission control
strategies likely to be more expensive (less cost-effective) than past strategies, but the cost-
effectiveness of our engine/diesel sulfur program falls within the range of potential future
strategies.
In summary, given the array of controls that will have to be implemented to make
progress toward attaining and maintaining the NAAQS, we believe that the weight of the
evidence from alternative means of providing substantial NOx + NMHC emission reductions
indicates that our proposed program is cost-effective. This is true from the perspective of other
mobile source control programs or from the perspective of other stationary source technologies
that might be considered.
7.3 20-Year Cost and Benefit Analysis
The following section presents the year-by-year cost and emission benefits associated
with the proposed standards for the 20-year period after implementation of the proposed
standards. For the categories where we expect a reduction in fuel consumption due to the
proposed standards, the fuel savings are presented separately. The overall cost, incorporating the
impact of the fuel savings is also presented.
Table 7.3.-1 presents the year-by-year cost and emission benefits for the proposed
compression-ignition (CI) recreational marine requirements. (The numbers presented in Table
7.3.-1 are not discounted.)
n This rulemaking was remanded by the D.C. Circuit Court on May 14, 1999. However,
the analyses completed in support of that rulemaking are still relevant, since they were designed
to investigate the cost-effectiveness of a wide variety of potential future emission control
strategies.
7-12
-------
Chapter 7: Cost per Ton
Ta
Cost and Emission Benefits of the Pro
Year
2"
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
7075
HC+NOx
Benefits (tons)
408
827
1,245
1,729
2,216
2,710
3,194
3,683
4,171
4,661
5,157
5,639
6,124
6,611
7,093
7,576
8,054
8,547
9,068
9679
CO
Benefits (tons)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ble 7.3.-1
posed CI Recreational Marine Requirements
Costw/o^^
Fuel Savings
$2,951,157
$3,312,159
$3,396,992
$3,646,513
$3,735,360
$2,314,047
$2,367,961
$2,230,244
$2,191,180
$2,238,896
$2,290,857
$2,338,809
$2,386,760
$2,434,712
$2,482,664
$2,530,616
$2,578,568
$2,626,520
$2,674,472
$7 777 473
Fuel Savings
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
$0
Cost w/
Fuel Savings
$2,951,157
$3,312,159
$3,396,992
$3,646,513
$3,735,360
$2,314,047
$2,367,961
$2,230,244
$2,191,180
$2,238,896
$2,290,857
$2,338,809
$2,386,760
$2,434,712
$2,482,664
$2,530,616
$2,578,568
$2,626,520
$2,674,472
$7 777 473
Table 7.3.-2 presents the sum of the costs and emission benefits over the twenty year
period after the CI recreational marine requirements are proposed to take effect, on both a non-
discounted basis and a discounted basis (assuming a seven percent discount rate). The
annualized cost and emission benefits for the twenty-year period (assuming the seven percent
discount rate) are also presented.
7-13
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Draft Regulatory Support Document
Table 7.S.-2
Annualized Cost and Emission Benefits for the Period 2006-2025
due to the Proposed CI Recreational Marine Requirements
Undiscounted
20-year Value
Discounted
20-year Value
Annualized
Value
HC+NOx
Benefits
(tons)
98,342
43,726
4,127
CO Benefits
(tons)
0
0
0
Cost w/o
Fuel Savings
(Million $)
$53.5
$31.4
$3.0
Fuel Savings
(Million $)
$0.0
$0.0
$0.0
Cost w/
Fuel Savings
(Million $)
$53.5
$31.4
$3.0
Table 7.3.-3 presents the year-by-year cost and emission benefits for the proposed large
spark-ignition (SI) engine requirements. (The numbers presented in Table 7.3.-3 are not
discounted.)
7-14
-------
Chapter 7: Cost per Ton
Table 1.3.-3
Cost and Emission Benefits of the Proposed Large SI Engine Requirements
Year
2"
-------
Draft Regulatory Support Document
Table 7.S.-4
Annualized Cost and Emission Benefits for the Period 2004-2023
due to the Proposed Large SI Engine Requirements
Undiscounted
20-year Value
Discounted
20-year Value
Annualized
Value
HC+NOx
Benefits
(tons)
10,059,802
4,795,369
452,649
CO Benefits
(tons)
37,263,648
17,202,416
1,623,789
Cost w/o
Fuel Savings
(Million $)
$1,599.8
$904.3
$85.4
Fuel Savings
(Million $)
$7,145.0
$3,434.8
$324.2
Cost w/
Fuel Savings
(Million $)
($5,545.2)
($2,530.5)
($239.8)
Table 7.3.-5 presents the year-by-year cost and emission benefits for the proposed
snowmobile requirements. (The numbers presented in Table 7.3.-5 are not discounted.)
7-16
-------
Chapter 7: Cost per Ton
Table 7.3.-S
Cost and Emission Benefits of the Proposed Snowmobile Requirements
Year
2"
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
7075
HC
Benefits (tons)
10,949
21,937
32,848
44,140
57,886
71,954
85,448
98,859
111,904
119,312
126,527
132,390
137,680
141,024
143,752
145,933
147,725
149,129
150,308
151 397
CO
Benefits (tons)
28,488
57,072
85,448
114,808
151,436
188,906
224,873
260,626
295,402
315,519
335,157
351,235
365,808
374,871
382,265
388,154
393,054
396,874
400,077
403 005
Cost w/o
Fuel Savings
$8,490,613
$8,549,323
$7,734,547
$7,785,697
$39,496,324
$37,231,135
$30,986,329
$31,281,836
$26,191,916
$25,003,879
$25,253,918
$25,506,457
$25,761,522
$26,019,137
$26,279,329
$26,542,122
$26,807,543
$27,075,618
$27,346,375
$77619 838
Fuel Savings
$0
$0
$0
$0
$6,636,300
$13,258,300
$19,660,300
$26,031,500
$32,094,700
$37,988,500
$43,918,600
$49,436,200
$54,772,300
$57,184,600
$59,141,500
$60,773,900
$62,147,800
$63,261,000
$64,179,500
$64 907 700
Cost w/
Fuel Savings
$8,490,613
$8,549,323
$7,734,547
$7,785,697
$32,860,024
$23,972,835
$11,326,029
$5,250,336
($5,902,784)
($12,984,621)
($18,664,682)
($23,929,743)
($29,010,778)
($31,165,463)
($32,862,171)
($34,231,778)
($35,340,257)
($36,185,382)
($36,833,125)
C$37 787 3671
Table 7.3.-6 presents the sum of the costs and emission benefits over the twenty year
period after the requirements for snowmobiles are proposed to take effect, on both a non-
discounted basis and a discounted basis (assuming a seven percent discount rate). The
annualized cost and emission benefits for the twenty-year period (assuming the seven percent
discount rate) are also presented.
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Draft Regulatory Support Document
Table 7.S.-6
Annualized Cost and Emission Benefits for the Period 2006-2025
due to the Proposed Snowmobile Requirements
Undiscounted
20-year Value
Discounted
20-year Value
Annualized
Value
HC+NOx
Benefits
(tons)
2,081,097
979,258
92,435
CO Benefits
(tons)
5,513,078
2,588,835
244,368
Cost w/o
Fuel Savings
(Million $)
$487.0
$255.6
$24.1
Fuel Savings
(Million $)
$715.4
$300.0
$28.3
Cost w/
Fuel Savings
(Million $)
($228.4)
($44.4)
($4.2)
Table 7.3.-7 presents the year-by-year cost and emission benefits for the proposed
requirements for ATVs. (The numbers presented in Table 7.3.-7 are not discounted.)
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Chapter 7: Cost per Ton
Table 7.S.-7
Cost and Emission Benefits of the Proposed ATV Requirements
Year
2
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
7075
HC+NOx
Benefits (tons)
29,157
100,482
171,247
255,542
341,496
426,374
515,980
612,610
701,796
786,092
863,212
934,816
999,821
1,054,946
1,095,016
1,124,352
1,148,062
1,165,443
1,179,935
1 191 565
CO
Benefits (tons)
52,512
165,812
281,480
401,518
520,318
639,187
762,621
892,416
1,013,664
1,129,162
1,235,362
1,334,947
1,425,240
1,499,879
1,548,389
1,581,524
1,608,835
1,631,560
1,651,047
1 666 387
Cost w/o
Fuel Savings
$27,160,891
$50,131,272
$45,689,331
$63,725,033
$78,458,613
$71,127,217
$67,349,374
$60,745,130
$57,190,382
$56,810,044
$56,810,044
$56,810,044
$56,810,044
$54,369,424
$51,928,804
$51,928,804
$51,928,804
$51,928,804
$51,928,804
$51 978 804
Fuel Savings
$4,292,200
$14,731,200
$24,938,100
$36,446,300
$47,393,500
$58,026,100
$69,170,200
$81,152,500
$91,989,700
$102,064,600
$111,098,900
$119,334,600
$126,656,200
$132,697,400
$136,876,300
$139,763,800
$142,059,500
$143,763,400
$145,032,800
$146411 100
Cost w/
Fuel Savings
$22,868,691
$35,400,072
$20,751,231
$27,278,733
$31,065,113
$13,101,117
($1,820,826)
($20,407,370)
($34,799,318)
($45,254,556)
($54,288,856)
($62,524,556)
($69,846,156)
($78,327,976)
($84,947,496)
($87,834,996)
($90,130,696)
($91,834,596)
($93,103,996)
C$Q4 487 7961
Table 7.3.-8 presents the sum of the costs and emission benefits over the twenty year
period after the requirements for ATVs are proposed to take effect, on both a non-discounted
basis and a discounted basis (assuming a seven percent discount rate). The annualized cost and
emission benefits for the twenty-year period (assuming the seven percent discount rate) are also
presented.
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Draft Regulatory Support Document
Table 7.3.-S
Annualized Cost and Emission Benefits for the Period 2006-2025
due to the Proposed ATV Requirements
Undiscounted
20-year Value
Discounted
20-year Value
Annualized
Value
HC+NOx
Benefits
(tons)
14,697,944
6,640,351
626,803
CO Benefits
(tons)
21,041,860
9,603,721
906,525
Cost w/o
Fuel Savings
(Million $)
$1,114.8
$629.8
$59.5
Fuel Savings
(Million $)
$1,873.9
$858.0
$81.0
Cost w/
Fuel Savings
(Million $)
($759.1)
($228.3)
($21.5)
Table 7.3.-9 presents the year-by-year cost and emission benefits for the proposed off-
highway motocycles requirements. (The numbers presented in Table 7.3.-9 are not discounted.)
7-20
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Chapter 7: Cost per Ton
Table 1.3.-9
Cost and Emission Benefits of the Proposed Off-Highway Motorcycle Requirements
Year
2"
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
7075
HC+NOx
Benefits (tons)
3,202
9,491
16,459
23,879
31,288
38,820
46,025
53,114
60,067
65,156
69,060
71,707
73,763
75,530
76,986
78,115
79,014
79,721
80,289
80 807
CO
Benefits (tons)
2,250
6,704
11,600
16,832
22,063
27,392
32,505
37,549
42,510
46,242
48,936
50,833
52,303
53,567
54,608
55,411
56,053
56,555
56,961
57 373
Cost w/o
Fuel Savings
$8,806,305
$17,208,490
$15,768,334
$14,297,728
$13,123,614
$11,551,224
$11,289,563
$11,402,459
$11,516,483
$11,631,648
$11,747,964
$11,865,444
$11,984,099
$12,103,940
$12,224,979
$12,347,229
$12,470,701
$12,595,408
$12,721,362
$17848 576
Fuel Savings
$691,900
$2,036,100
$3,495,800
$5,024,800
$6,519,700
$8,010,200
$9,406,100
$10,753,600
$12,050,500
$13,010,800
$13,713,700
$14,203,200
$14,582,700
$14,911,600
$15,184,400
$15,395,600
$15,566,100
$15,701,400
$15,812,500
$15 910400
Cost w/
Fuel Savings
$8,114,405
$15,172,390
$12,272,534
$9,272,928
$6,603,914
$3,541,024
$1,883,463
$648,859
($534,017)
($1,379,152)
($1,965,736)
($2,337,756)
($2,598,601)
($2,807,660)
($2,959,421)
($3,048,371)
($3,095,399)
($3,105,992)
($3,091,138)
C$3 061 87/n
Table 7.3.-10 presents the sum of the costs and emission benefits over the twenty year
period after the requirements for off-highway motorcycles are proposed to take effect, on both a
non-discounted basis and a discounted basis (assuming a seven percent discount rate). The
annualized cost and emission benefits for the twenty-year period (assuming the seven percent
discount rate) are also presented.
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Draft Regulatory Support Document
Table 7.3.-10
Annualized Cost and Emission Benefits for the Period 2006-2025
due to the Proposed Off-Highway Motorcycle Requirements
Undiscounted
20-year Value
Discounted
20-year Value
Annualized
Value
HC+NOx
Benefits
(tons)
1,112,488
521,170
49,195
CO Benefits
(tons)
788,197
369,020
34,833
Cost w/o
Fuel Savings
(Million $)
$249.5
$142.9
$13.5
Fuel Savings
(Million $)
$222.0
$104.7
$9.9
Cost w/
Fuel Savings
(Million $)
$27.5
$38.2
$3.6
Table 7.3.-11 presents the year-by-year cost and emission benefits for all of the proposed
requirements, excluding snowmobiles. (The numbers presented in Table 7.3.-11 are not
discounted.) Snowmobiles have been excluded from this aggregate analysis because the focus of
the proposed snowmobile controls is CO emissions, unlike the other categories where the focus
of the proposed controls is HC and/or NOx emissions.
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Chapter 7: Cost per Ton
Table 7.3.-11
Cost and Emission Benefits of the Proposed Requirements
for All Equipment Categories covered by the Proposal (Excluding Snowmobiles)
Year
2"
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Draft Regulatory Support Document
Table 7.3.-12
Annualized Cost and Emission Benefits for the Period 2004-2025
due to the Proposed Requirements for All Equipment (Excluding Snowmobiles)
Undiscounted
22-year Value
Discounted
22-year Value
Annualized
Value
HC+NOx
Benefits
(tons)
29,579,850
11,941,041
1,037,257
CO Benefits
(tons)
69,744,333
28,460,357
2,476,552
Cost w/o
Fuel Savings
(Million $)
$3,361.5
$1,688.7
$149.4
Fuel Savings
(Million $)
$11,006.2
$4,700.0
$410.6
Cost w/
Fuel Savings
(Million $)
($7,644.7)
($3,011.2)
($261.3)
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Chapter 7: Cost per Ton
Chapter 7 References
1 ."Regulatory Impact Analyses for the Particulate Matter and Ozone National Ambient Air
Quality Standards and Regional Haze Rule," Appendix B, "Summary of control measures in the
PM, regional haze, and ozone partial attainment analyses," Innovative Strategies and Economics
Group, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, July 17, 1997.
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Draft Regulatory Support Document
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Chapter 8: Initial Regulatory Flexibility Analysis
CHAPTER 8: Initial Regulatory Flexibility Analysis
This section presents our Initial Regulatory Flexibility Analysis (IRFA) which evaluates
the impacts of our proposed program on small businesses. Prior to issuing our proposal, we
analyzed the potential impacts of our program on small businesses. As a part of this analysis, we
convened a Small Business Advocacy Review Panel, as required under the Regulatory Flexibility
Act as amended by the Small Business Regulatory Enforcement Fairness Act of 1996
(SBREFA). Through the Panel process, we gathered advice and recommendations from small
entity representatives (SERs) who would be affected by our proposed vehicle and fuel standards.
The report of the Panel has been placed in the rulemaking record.
8.1 Requirements of the Regulatory Flexibility Act
When proposing and promulgating rules subject to notice and comment under the Clean
Air Act, we are generally required under the Regulatory Flexibility Act (RFA) to conduct a
regulatory flexibility analysis unless we certify that the requirements of a regulation will not
cause a significant impact on a substantial number of small entities. The key elements of the
FRFA include:
• the number of affected small entities;
• the projected reporting, record keeping, and other compliance requirements of the
proposed rule, including the classes of small entities that would be affected and
the type of professional skills necessary for preparation of the report or record;
• other federal rules that may duplicate, overlap, or conflict with the proposed rule;
and,
any significant alternatives to the proposed rule that accomplish the stated
objectives of applicable statutes and which minimize significant economic
impacts of the proposed rule on small entities.
The RFA was amended by SBREFA to ensure that concerns regarding small entities are
adequately considered during the development of new regulations that affect them. Although we
are not required by the CAA to provide special treatment to small businesses, the RFA requires
us to carefully consider the economic impacts that our rules will have on small entities.
Specifically, the RFA requires us to determine, to the extent feasible, our rule's economic impact
on small entities, explore regulatory options for reducing any significant economic impact on a
substantial number of such entities, and explain our ultimate choice of regulatory approach.
In developing the NPRM, we concluded that the program under consideration for
recreational vehicles would likely have a significant impact on a substantial number of small
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Draft Regulatory Support Document
entities.
8.2 Description of Affected Entities
The following table (Table 1) provides an overview of the primary SB A small business
categories potentially affected by this regulation. EPA is in the process of developing a more
detailed industry characterization of the entities potentially subject to this regulation.
Table 8.2-1
Primary SBA Small Business Categories Potentially Affected by this Proposed Regulation
Industry
Motorcycles and motorcycle parts
manufacturers
Snowmobile and ATV
manufacturers
Independent Commercial
Importers of Vehicles and parts
Nonroad SI engines
Internal Combustion Engines
Boat Building and Repairing
NAICSa Codes
336991
336999
421110
333618
333618
336612
Defined by SBA as a
Small Business If:b
<500 employees
<500 employees
<100 employees
<1,000 employees
<1000 employees
<500 employees
NOTES:
a. North American Industry Classification System
b. According to SBA's regulations (13 CFR 121), businesses with no more than the listed number of employees or
dollars in annual receipts are considered "small entities" for purposes of a regulatory flexibility analysis.
8.2.1 Recreational Vehicles (off-highway motorcycles, ATVs, and snowmobiles)
The ATV sector has the broadest assortment of manufacturers. There are seven
companies representing over 95 percent of total domestic ATV sales. The remaining 5 percent
come from importers who tend to import inexpensive, youth-oriented ATVs from China and
other Asian nations. EPA has identified 21 small companies (as defined in Table 4.1, above) that
offer off-road motorcycles, ATVs, or both products. Annual unit sales for these companies can
range from a few hundred to several thousand units per year.
Based on available industry information, four major manufacturers, Arctic Cat,
Bombardier (also known as Ski-Doo), Polaris, and Yamaha, account for over 99 percent of all
domestic snowmobile sales. The remaining one percent comes from very small manufacturers
who tend to specialize in unique and high performance designs .
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Chapter 8: Initial Regulatory Flexibility Analysis
We have identified three small manufacturers of snowmobiles and one potential small
manufacturer who hopes to produce snowmobiles within the next year. Two of these
manufacturers (Crazy Mountain and Fast), plus the potential newcomer (Redline) specialize in
high performance versions of standard recreational snowmobile types (i.e., travel and mountain
sleds). The other manufacturer (Fast Trax) produces a unique design, which is a scooter-like
snowmobile designed to be ridden standing up. Most of these manufacturers build less than 50
units per year.
8.2.2 Marine Vessels
Marine vessels include the boat, engine, and fuel system. Exhaust emission controls
including NTE requirements, as addressed in the August 29, 1999 SBREFA Panel Report, would
affect the engine manufacturers and may affect boat builders.
8.2.2.1 Small Diesel Engine Marinizers
EPA has determined that there are at least 16 companies that manufacture CI diesel
engines for recreational vessels. Nearly 75 percent of diesel engines sales for recreational vessels
in 2000 can be attributed to three large companies. Six of the 16 identified companies are
considered small businesses as defined by SBA SIC code 3519. Based on sales estimates for
2000, these six companies represent approximately 4 percent of recreational marine diesel engine
sales. The remaining companies each comprise between two and seven percent of sales for 2000.
8.2.2.2 Small Recreational Boat Builders
EPA has less precise information about recreational boat builders than is available about
engine manufacturers. EPA has utilized several sources, including trade associations and Internet
sites when identifying entities that build and/or sell recreational boats. EPA has also worked
with an independent contractor to assist in the characterization of this segment of the industry.
Finally, EPA has obtained a list of nearly 1,700 boat builders known to the U.S. Coast Guard to
produce boats using engines for propulsion. More than 90% of the companies identified so far
would be considered small businesses as defined by SBA SIC code 3732. EPA continues to
develop a more complete picture of this segment of the industry and will provide additional
information as it becomes available.
8.2.3 Large Spark Ignition Engines
The Panel is aware of one engine manufacturer of Large SI engines that qualifies as a
small business. This company plans to produce engines that meet the standards adopted by
CARB in 2004, with the possible exception of one engine family. If EPA adopts long-term
standards, this would require manufacturers to do additional calibration and testing work. If EPA
adopts new test procedures (including transient operation), there may also be a cost associated
with upgrading test facilities.
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Draft Regulatory Support Document
8.3 Projected Costs of the Proposed Program
The costs associated with the proposed program can be found in Chapter 5 of the Draft
Regulatory Support Document. Chapter 5 includes a description of our approach to estimating
the cost of complying with emission standards. We start with a general description of the
approach to estimating costs, then describe the technology changes we expect and assign costs to
them. We also present an analysis of the estimated aggregate cost to society.
8.4 Projected Reporting, Recordkeeping, and Other Compliance
Requirements of the Proposed Rule
For any emission control program, EPA must have assurances that the regulated engines
will meet the standards. Historically, EPA programs have included provisions placing
manufacturers responsible for providing these assurances. The program that EPA is considering
for manufacturers subject to this proposal may include testing, reporting, and record keeping
requirements. Testing requirements for some manufacturers may include certification (including
deterioration testing), and production line testing. Reporting requirements would likely include
test data and technical data on the engines including defect reporting. Manufacturers would
likely have to keep records of this information.
8.5 Other Related Federal Rules
We are aware of several other current Federal rules that relate to the proposed rule under
development. During the Panel's outreach meeting, SERs specifically pointed to Consumer
Product Safety Commission (CPSC) regulations covering ATVs, and noted that they may be
relevant to crafting an appropriate definition for a competition exclusion in this category. The
Panel recommends that EPA continue to consult with the CPSC in developing a proposed and
final rule in order to better understand the scope of the Commission's regulations as they may
relate to the competition exclusion.
The Panel is also aware of other Federal rules that relate to the categories that EPA would
address with the proposed rule, but are not likely to affect policy considerations in the rule
development process. For example, there are now EPA noise standards covering off-road
motorcycles; however, EPA expects that most emission control devices are likely to reduce,
rather than increase, noise, and that therefore the noise standards are not likely to be important in
developing a proposed rule.
8.6 Regulatory Alternatives
The Panel considered a wide range of options and regulatory alternatives for providing
small businesses with flexibility in complying with the proposed emissions standards and related
requirements. As part of the process, the Panel requested and received comment on several ideas
for flexibility that were suggested by SERs and Panel members. The major options
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Chapter 8: Initial Regulatory Flexibility Analysis
recommended by the Panel can be found in Section 9 of the Panel's full Report.
Many of the flexible approaches recommended by the Panel can be applied to several of
the equipment categories that would potentially be affected by the proposed rule EPA is
developing. These approaches are identified in Table 1. First Tier Flexibilities: Based on
consultations with SERs, the Panel believes that the first four provisions in Table 1 are likely to
provide the greatest flexibility for many small entities. These provisions are likely to be most
valuable because they either provide more time for compliance (e.g., additional leadtime and
hardship provisions) or allow for certification of engines based on particular engine designs or
certification to other EPA programs. Second Tier Flexibilities: The remaining four approaches
have the potential to reduce near-term and even long-term costs once a small entity has a product
it is preparing to certify. These are important in that the costs of testing multiple engine
families, testing a fraction of the production line, and/or developing deterioration factors can be
significant. Small businesses could also meet an emission standard on average or generate
credits for producing engines which emit at levels below the standard; these credits could then be
sold to other manufacturers for compliance or banked for use in future model years.
During the consultation process, it became evident that, in a few situations, it could be
helpful to small entities if unique provisions were available. Three such provisions are described
below.
(a) Snowmobiles: The Panel recommends EPA seek comment on a provision which
would allow small snowmobile manufacturers to petition EPA for a relaxed standard for
one or more engine families, up to 300 engines per year, until the family is retired or
modified, if such a standard is justifiable based on the criteria described in the Panel
report.
(b) ATVs and Off-road Motorcycles: The Panel recommends that the hardship provision
for ATVs and off-road motorcycles allow hardship relief to be reviewed annually for a
period that EPA anticipates will likely be no more than two years in order for importers to
obtain complying products.
(c) Large SI: The Panel recommends that small entities be granted the flexibility initially
to reclassify a small number of their small displacement engines into EPA's small spark-
ignition engine program (40 CFR part 90). Small entities would be allowed to use those
requirements in lieu of the requirements EPA intends to propose for large entities.
Table 1 describes the flexibilities that the Panel is generally recommending for each of
the sectors where appropriate as indicated in the table.
The Panel also crafted recommendations to address SERs' concerns that ATV and off-
road motorcycle standards that essentially required manufacturers to switch to four-stroke
engines might increase costs to the point that many small importers and manufacturers could
experience significant adverse effects. The Panel recommends that EPA request comment in its
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Draft Regulatory Support Document
proposed rule on the effect of the proposed standard on these small entities, with the specific
intent of developing information—including the extent to which sales of their products would
likely to be reduced in response to changes in product price attributable to the proposed
standards—that could be used to inform a decision in the final rule as to whether EPA should
provide additional flexibility beyond that considered by the Panel.
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