Air and Radiation EPA420-R-05-023
December 2005
United States NR-011c
Environmental Protection
Agency
Nonroad Spark-Ignition
Engine Emission
Deterioration Factors
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EPA420-R-05-023
December 2005
NR-011C
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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I. Purpose
This report addresses the emission deterioration rates for spark-ignition engines used in
the final NONROAD2005 model. The specific deterioration inputs used in NONROAD and
their basis will be addressed for land-based spark-ignition engines at or below 25 horsepower,
land-based spark-ignition engines over 25 horsepower, and recreational marine spark-ignition
engines using gasoline. Deterioration is also addressed for land-based liquid petroleum gas
(LPG) and compressed natural gas engines (CNG). Deterioration inputs for compression-
ignition (diesel) engines are addressed in the report, Exhaust Emission Factors for Nonroad
Engine Modeling - Compression Ignition (NR-009c). The EPA welcomes comments and
suggestions concerning our approach to modeling nonroad engine emissions deterioration.
II. Background
As used here, the term "deterioration" refers to the degradation of an engine's exhaust
emissions performance over its lifetime due to normal use or misuse (i.e., tampering or neglect).
Engine deterioration increases exhaust emissions, usually leads to a loss of combustion
efficiency, and can in some cases increase nonexhaust emissions. The amount of emissions
increase depends on an engine's design, production quality, and technology type (e.g., spark
ignition two-stroke and four-stroke, compression ignition). Other factors, such as the various
equipment applications in which an engine is used, usage patterns, and how it is stored and
maintained, may also affect deterioration.
The term "deterioration rate" refers to the degree to which an engine's emissions increase
per unit of activity. Nonroad engine activity is expressed in terms of hours of use or fraction of
median life. The term "deterioration factor" refers to the ratio of an engine's emissions at its
median life divided by its emissions when new.
The terms useful life and median life are used in the following manner in this report in
order to avoid confusion. Useful life is a regulatory term used to indicate the amount of time
during the life of a nonroad engine that a manufacturer must certify to the U.S. EPA that the
engine meets a required emission standard as defined by a regulation. Median life, as used in this
report, refers to the age at which 50 percent of the engines sold in a given year have ceased to
function and have been scrapped.1
III. Core Challenge
The core challenge associated with estimating nonroad engine deterioration is the
development of reasonably accurate deterioration rates for the enormous range of nonroad
engine types and applications from the limited amount of nonroad emission deterioration data
that exist at this time. To estimate deterioration, the emission performance of engines at various
ages is required. Such information can be obtained from a longitudinal study that examines the
same set of engines periodically as they age, or from a sampling study that tests engines of
1
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various ages but the same basic design. In either case, the engines studied should be selected
randomly from the population of engines actually being used in the field.
Given the limited available test data, EPA is currently unable to develop unique
deterioration rates based on actual engine test data for the myriad of applications and power
levels covered by NONROAD. The Office of Transportation and Air Quality has conducted
emissions testing on several dozen small spark ignition lawn & garden engines and a few large
compression-ignition engines. The nonroad engine industry and a few States have also
conducted some nonroad engine emissions testing. However, the nonroad engine emissions data
currently available are still limited when compared to the large number of nonroad engine types
and applications for which these engines are used, particularly for the purposes of evaluating
emission deterioration as engines age. The EPA has obtained extensive data on the emissions
deterioration of light-duty highway engines, but these engines are unlikely to deteriorate in a
fashion typical of nonroad engines due to fundamental differences in engine and emission
control technology design, maintenance, and operation. Deterioration in emissions from light-
duty vehicles (LDVs) is thought to be due in large part to gross failures of emission control after-
treatment systems, which nonroad engines do not have at this time.
A related challenge is that the EPA has essentially no data on the incidence of tampering
and/or neglect of proper maintenance and only limited data that distinguish the effect of such
malmaintenance from the effects of normal usage. These data are based on emission tests of two
lawnmower engines that had various components, including the sparkplug, air filter, and oil,
manipulated to simulate bad maintenance practices (i.e., not changing the sparkplug, air filter
and oil on a regular basis, as recommended by the manufacturer). The results of this effort were
inconclusive, suggesting that intentional disablement of engine components does not adequately
simulate emissions deterioration from normal usage. The EPA requests that state and industry
stakeholders share any data regarding the incidence of tampering and neglect of proper
maintenance they may have. The EPA also requests that stakeholders share any data they have
regarding the relationship between emissions deterioration due to normal usage and emissions
deterioration due to intentional disablement of engine components.
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IV. Method of Applying Deterioration In NONROAD
Generally, the NONROAD model addresses the effects of deterioration in the inventory
calculation by multiplying a zero hour emission factor for each category of engine by a
deterioration rate as the engine ages. The following formula describes the basic form of the
calculation:
EFaged = EF0*DF (1)
where: EF (aged) is the emission factor for an aged engine
EF0 is the emission factor for a new engine
DF is the deterioration factor.
In order for the NONROAD model to be compatible with the EPA's small nonroad spark
ignition engine rulemaking process and also be able to calculate deterioration for other engines,
we have derived the following multi-purpose deterioration function:
DF = 1 + A * (Age Factor)b for Age Factor < 1 (2)
DF = 1 + A for Age Factor > 1
where Age Factor= [Cumulative Hours * Load Factor]
Median Life at Full Load, in Hours
A, b = constants for a given technology type; b < 1.
The constants A and b can be varied to approximate a wide range of deterioration
patterns. "A" can be varied to reflect differences in maximum deterioration. For example,
setting A equal to 2.0 would result in emissions at the engine's median life being three times the
emissions when new. The shape of the deterioration function is determined by the second
constant, "b." This constant can be set at any level between zero and 1.0; currently, the
NONROAD model sets "b" equal to either 0.5 or 1.0. The first case results in a curvilinear
deterioration rate in which most of the deterioration occurs in the early part of an engine's life.
The second case results in a linear deterioration pattern in which the rate of deterioration is
constant throughout the median life of an engine. In both cases, the EPA decided to cap
deterioration at the end of an engine's median life, under the assumption that an engine can only
deteriorate to a certain point beyond which it becomes inoperable. For spark ignition engines at
or below 25 horsepower, NONROAD uses the regulatory useful life values in Appendix F of the
Phase 1 regulatory support document for median life values. For other engines, NONROAD
uses the median life values from the Power Systems Research (PSR) database.2 These functions
can be used to provide a close approximation to the shape of the deterioration curves used in
NSEEM1 and NSEEM2 (regulatory models for the Phase 1 and 2 Small Spark-Ignition Rules)
for spark ignition engines less than 25 horsepower.
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SI engines have a wide range of designs that affect their emissions deterioration. To
model these different deterioration patterns, NONROAD categorizes SI engines into "technology
types" by their design and emission control equipment. A given technology type can apply to
one or more horsepower-application categories, and a given horsepower-application category
can be divided into more than one technology type. NONROAD applies a given deterioration
function (that is, a given A and b value) to all engines of a given technology type, regardless of
their application or power range. As a result, a single technology type may be applied to engines
with very different median lives, but this difference is handled by expressing engine age in terms
of the "Age Factor" defined above. The EPA believes this approach is reasonable, since
deterioration patterns should be more closely related to the design of the engine and its emission
control technology than to the kind of application in which it is used. Furthermore, the available
data on emissions deterioration of nonroad SI engines is insufficient to develop separate
deterioration functions for the many combinations of application, horsepower range, and
technology type.
NONROAD's technology type feature allows each horsepower-application category to be
divided into as many as ten technology types, each with its own deterioration pattern. The
technology type feature gives the model flexibility to handle the full range of engine designs
used in nonroad equipment. For example, the technology type feature can handle the 33 distinct
engine types that are defined by EPA's Phase 1 and 2 Small Engine Rules, as shown in Tables 1
through 5. However, deterioration data for each technology type across different applications
are not available at the present time. Thus, the NONROAD model does not apply different
deterioration patterns to engines of the same technology type used in different applications.
Instead, the model applies different deterioration patterns to engines within each engine type
(i.e., two-stroke and four-stroke spark ignition) based on the more detailed engine classes
defined in the Phase 1 and 2 Small Engine Rules, the proposed Large Spark-Ignition Equipment,
Recreational Marine and Recreational Equipment Rule, and a analysis of 1998-2005 model year
emission certification data for recreational marine.3 In other words, NONROAD models
deterioration for tiller and a lawn mower applications that are equipped with the same engine
type by using the same deterioration pattern for that technology type.
V. Deterioration Inputs For Land-based Engines At or Below 25 Horsepower
In the final NONROAD2005 model, the constant 'b' is set at 0.5 for four-stroke engines,
resulting in a square root relationship between age and deterioration. The constant 'b' is set at
1.0 for two-stroke engines, which produces a linear relationship between age and deterioration.
This use of a curvilinear deterioration pattern for four-stroke engines and a linear deterioration
pattern for two-stroke engines is similar to the approach used in the NSEEM2 model used for the
Phase 2 Small Engine Rule.
The inputs for the variable 'A' of the NONROAD deterioration function are shown in
Tables 1-5 for the small engine classes defined in the Phase 1 and 2 Small Engine Rules. EPA
derived the deterioration values for Phase 2 engines with catalysts (G2HxC2) and set NOx
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deterioration values to zero based on analyses done during the development of the Phase 2 rule.4
For the other types of small engines included in the Phase 1 and 2 rulemakings, the values came
from the Phase I Regulatory Support Document for maximum life emission factors and new
engine emission factors. It should be noted the HC deterioration 'A' value (0.201) for
snowblowers (G2GT25) is the same as that used for baseline Class 1 and 2 two-stroke
nonhandheld engines (G1N1 and G2N2).
For each pollutant and each engine type, variable 'A' represents the maximum
deterioration rate reached at one median life. It should be noted that particulate matter (PM)
standards were not considered or included in the Phase 1 and Phase 2 Small Engine Rules, and
little data exists for PM deterioration rates. Based on EPA's best judgement at this time, PM
deterioration in two and four-stroke engines are equated to that of HC in the final
NONROAD2005 model. The EPA requests stakeholders with information about the PM
emissions deterioration of two-stroke engines to submit such data.
The deterioration rates used in NONROAD for small engines covered under the Phase 1
and 2 Small Engine Rules approximate the levels of deterioration found in testing, including the
testing summarized in NEVES and the testing done to support the Phase 1 and 2 Small Engine
Rules. Where these test results differ, the EPA has chosen to give greater weight to data taken
from engines which have experienced usage patterns that reflect expected field conditions. The
test data submitted to EPA for the Phase 2 Small Engine Rule, for example, reflects testing of
engines that have undergone accelerated aging which EPA does not believe to be representative
of the aging experienced by engines in use. After evaluating all available data, the EPA has
determined that the level of deterioration used in NSEEM1 and Phase 1 Small Engine Rule
provides a reasonable basis for the deterioration rates used in NONROAD. These deterioration
rates are generally higher than the deterioration rates used for regulatory purposes in NSEEM2
and the Phase 2 Small Engine Rule, but are generally smaller than those used in NEVES. The
EPA believes that the deterioration rates used in NONROAD are more reflective of the
deterioration rates that one would expect to find out in the field when equipment powered by
small spark ignition engines is used by the average person than are the deterioration rates found
in NSEEM2 and the Phase 2 Small Engine Rule.
There are some small engine applications that are not covered by the Phase 1 or 2 Small
Engine Rules. These include marine engines (SCC 2282xxxxxx) and certain recreational
equipment such as snowmobiles (226x001020), off-road motorcycles, all-terrain vehicles
(226x001030), and specialty vehicle carts (226x001060). In NONROAD the two-stroke
versions of the recreational equipment engines are assigned deterioration values equal to the
G2N2 tech type shown in Table 2, but they use a tech type name of R12S since the emission
factors differ from the other engine applications. Four-stroke versions of these recreational
equipment engines use deterioration rates based on pre-1978 uncontrolled four-stroke on-
highway motorcycles from the MOBILE model.5
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Table 1
Class 1 (Displacement < 225 cc) Nonhandheld Deterioration Factor A
Engine Tech Type
G2N1 (gas 2-stroke nonhandheld Class 1, baseline)
G4N1S (gas, side-valve, 4-stroke nonhandheld Class 1,
baseline)
G4N1O (gas, overhead valve, 4-stroke nonhandheld Class 1,
baseline)
G2N11 (2-stroke, Phase 1)
G4N1S1 (Phase 1 side-valve, 4-stroke)
G4N1O1 (Phase 1 overhead valve, 4-stroke)
G4N1SC1 (Phase 1 side-valve, 4-stroke with catalyst)
G4N1S2 (Phase 2 side-valve, 4-stroke)
G4N1O2 (Phase 2 overhead valve, 4-stroke)
HC
0.201
1.1
1.1
0.266
5.103
1.753
5.103
5.103
1.753
CO
0.199
0.9
0.9
0.231
1.109
1.051
1.109
1.109
1.051
NOx
0
0
0
0
0
0
0
0
0
PM
0.201
1.1
1.1
0.266
5.103
1.753
5.103
5.103
1.753
BSFC
0
0
0
0
0
0
0
0
0
Table 2
Class 2 (Displacement >225 cc; Power Rating < 25 hp) Nonhandheld Deterioration Factor A
Engine Tech Type
G2N2 (gas 2-stroke nonhandheld Class 2, baseline)
G4N2S (gas, side-valve, 4-stroke nonhandheld Class 2,
baseline)
G4N2O (gas, overhead valve, 4-stroke nonhandheld Class 2,
baseline)
G4N2S1 (Phase 1 side-valve, 4-stroke with catalyst)
G4N2O1 (Phase 1 overhead valve 4-stroke)
G4N2S2 (Phase 2 side-valve)
G4N2O2 (Phase 2 overhead valve)
HC
0.201
1.1
1.1
1.935
1.095
1.935
1.095
CO
0.199
0.9
0.9
0.887
1.307
0.887
1.307
NOx
0
0
0
0
0
0
0
PM
0.201
1.1
1.1
1.935
1.095
1.935
1.095
BSFC
0
0
0
0
0
0
0
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Table 3
Class 3 (Displacement < 20cc) Handheld Deterioration Factor A
Engine Tech Type
G2H3 (gas 2-stroke handheld Class 3, baseline)
G2H31 (Phase 1)
G2H3C1 (Phase 1 with catalyst)
G2H32 (Phase 2)
G2H3C2 (Phase 2 with catalysts)
HC
0.2
0.24
0.24
0.24
0.72
CO
0.2
0.24
0.24
0.24
0.24
NOx
0
0
0
0
0
PM
0.2
0.24
0.24
0.24
0.24
BSFC
0
0
0
0
0
Table 4
Class 4 (20cc < Displacement < 50 cc) Handheld Deterioration Factor A
Engine Tech Type
G2H4 (gas 2-stroke handheld Class 4, baseline)
G2H41 (Phase 1)
G2H4C1 (Phase 1 with catalyst)
G4H41 (Phase 1 4-stroke)
G2H42 (Phase 2)
G2H4C2 (Phase 2 with catalyst)
G4H42 (Phase 2 4-stroke)
HC
0.2
0.29
0.29
1.1
0.29
0.77
1.1
CO
0.2
0.24
0.24
0.9
0.24
0.24
0.9
NOx
0
0
0
0
0
0
0
PM
0.2
0.29
0.29
1.1
0.29
0.29
1.1
BSFC
0
0
0
0
0
0
0
Table 5
Class 5 (Displacement > 50cc; Power Rating <25 HP) Handheld Deterioration Factor A
Engine Tech Type
G2H5 (gas 2-stroke handheld Class 5, baseline)
G2H51 (Phase 1)
G2H5C1 (Phase 1 with catalyst)
G2H52 (Phase 2)
G2H5C2 (Phase 2 with catalyst)
HC
0.2
0.266
0.266
0.266
0.626
CO
0.2
0.231
0.231
0.231
0.231
NOx
0
0
0
0
0
PM
0.2
0.266
0.266
0.266
0.266
BSFC
0
0
0
0
0
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VI. Deterioration Inputs for Land-based Spark Ignition Engines Greater than 25
Horsepower (19 kilowatts)
The deterioration factors currently used in NONROAD for recreational equipment (i.e.,
snowmobiles, all-terrain vehicles, and offroad motorcycles) and other large spark-ignition
engines over 25 horsepower found in industrial and commercial equipment (e.g., forklifts,
generators, compressors) are based on those used in the final rulemaking for recreational
equipment and large spark-ignition engines.6 These are based on on-highway deterioration data.
At this time, EPA does not have deterioration data on large spark-ignition engines.
However, EPA currently believes that larger uncontrolled carbureted gasoline nonroad engines
would likely deteriorate more similarly to on-highway light-duty gasoline truck engines from the
1960's and 1970's.7 These older on-highway engine models used similar technology as today's
large nonroad gasoline engines.
MOBILES includes emission factors and deterioration and tampering rates for on-
highway heavy-duty gasoline engines. From this information, we can calculate the "A" value in
Equation 2 by dividing the deteriorated emission factor at 100,000 miles by the new engine
emission factor (and subtracting 1). To capture carbureted engines, we looked at the 20-year
average for the 1960 through 1979 model years. Also, MOBILES uses linear deterioration for
heavy-duty gasoline engines which translates to a "b" value of 1.0 in Equation 2.
As a check on these deterioration rates, we reviewed emission data from ten 1969 light-
duty gasoline trucks in an EPA report titled "Procurement and Emissions Testing of 1969 and
1972/1973 Model Year Gasoline Powered Light Duty Trucks" (EPA-460/3-80-11). These trucks
were emission tested in 1980 before and after engine maintenance. The ratio of the emissions
before and after maintenance gives some insight into the emission deterioration of the engines.
These data showed equivalent A values of 0.11 to 0.58 for HC, 0.31 to 0.39 for CO, and 0.05 to
0.10 for NOx. These data are consistent with the deterioration rates used in the final
NONROAD2005 model (see Appendix 1). The ranges of A values from the test data are due to
reporting the averages with and without one truck that appeared to be an outlier.
At this time, we do not have any information on the deterioration of fuel-injected
gasoline engines (without catalysts). MOBILE does not include emission rates for non-catalyzed
engines with fuel injection because catalysts were introduced before fuel-injection into the on-
highway market. Anecdotal information suggests that deterioration is low from these engines
compared to deterioration in a catalyst. For instance, accepted emission deterioration test
methods for current on-highway engines are performed by aging the catalyst to full life but using
a relatively new engine. Because we do not have better information, EPA used the same
deterioration coefficients for fuel-injected engines (without catalysts) as for carbureted engines.
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.
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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.8
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.9
It should be noted that PM is not addressed in the rulemaking process for large SI engines
used in commercial, industrial, and other types of equipment and little or no data exist for PM
deterioration associated with these types of equipment. Based on EPA's best judgement at this
time, PM deterioration has been equated with HC deterioration rates for these types of engines.
EPA welcomes any comments or information stakeholder may have concerning PM
deterioration.
Table 6 shows the deterioration factors used for recreational equipment and Table 7
shows the deterioration factors used for other large spark-ignition equipment.
Table 6
Deterioration Factors for Offroad Motorcycles, All-Terrain Vehicles, and Snowmobiles
Equipment/Tech Type
Precontrol 2-stroke offroad motorcycles (R12S)
Precontrol 4-stroke offroad motorcycles (R14S)
Phase 1 4-stroke offroad motorcycles (R14S1)
Precontrol 2-stroke all terrain vehicles (R12S)
Precontrol 4-stroke all terrain vehicles (R14S)
Phase 1 4-stroke all terrain vehicles (R14S1)
Precontrol 2-stroke snowmobiles (R12S)
Modified 2-stroke snowmobiles (R12S1)
Direct Injection 2-stroke snowmobiles (R12S2)
4-stroke snowmobiles (R14S)
HC
0.2
0.15
0.15
0.2
0.15
0.15
0.2
0.2
0.2
0.15
CO
0.2
0.17
0.17
0.2
0.17
0.17
0.2
0.2
0.2
0.17
NOX
0
0
0
0
0
0
0
0
0
0
PM
0.2
0.15
0.15
0.2
0.2
0.15
0.2
0.2
0.2
0.15
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Table 7
Deterioration Factors for Spark-Ignition Engines > 25 HP
Engine Tech Type
HC
CO
NOX
PM
Uncontrolled
G4GT25 (gas, 4-stroke, baseline)
LGT25 (LPG, baseline)
NGT25 (CNG, baseline)
0.26
0.26
0.26
0.35
0.35
0.35
0.03
0.03
0.03
0.26
0.26
0.26
Phase 1
G4GT251 (gas, 4-stroke)
LGT251 (LPG)
NGT251 (CNG)
0.64
0.64
0.64
0.36
0.36
0.36
0.15
0.15
0.15
0.26
0.26
0.26
Phase 2
G4GT252 (gas, 4-stroke)
LGT252 (LPG)
NGT252 (CNG)
0.64
0.64
0.64
0.36
0.36
0.36
0.15
0.15
0.15
0.26
0.26
0.26
VII. Deterioration Inputs for Recreational Marine Spark-Ignition Engines
Deterioration factors for sterndrive/inboard engines are those used in the draft
NONROAD2004 model. They are based on information gathered for the recreational marine
engine rulemaking (61 FR 52087, October 4, 1996).10 Deterioration factors for outboard and
personal watercraft have been updated for the final NONROAD2005 model, using 1998-2005
model year emissions certification data for these engines.3
The technology class descriptions and associated designations, which are used in the
NONROAD model, are shown in Table 8. The deterioration values for each technology class by
designation are shown in Table 9.
VIII. Liquid Petroleum and Compressed Natural Gas Spark-Ignition Engines
Because liquid petroleum gas (LPG) and compressed natural gas (CNG) engines are
primarily four-stroke engines, the EPA decided to assume that they would deteriorate at the same
rate as the corresponding gasoline-powered four-stroke SI engines for all pollutants. The EPA is
not aware of any deterioration data available for LPG and CNG engines and requests that
commenters submit any such data they may have to EPA. If such data become available, EPA
will revise the deterioration rates for these engines in NONROAD accordingly.
10
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Table 8
Marine Engine Technology Class and Designations
Technology Class Differentiation
Type
Outboard
PWC
SD/I
Cycle
2- Stroke
4- Stroke
2- Stroke
4- Stroke
4-stroke
Fuel System
Carbureted
Carburetor Modifications
Carbureted
Indirect Injection
Direct Injection
Carbureted
In direct Injection
Direct Injection
Carbureted
Carburetor Modifications
Carbureted
In direct Injection
Direct Injection
Carbureted
In direct Injection
Direct Injection
Carbureted
Direct Injection
Aftertreatment
none
none
3- Way Catalyst
none
none
none
none
none
none
none
2- Way Catalyst
none
none
none
none
none
none
none
Class Designation
NONROAD
2004*
Ml
M5
M6
M8
M9
M4
—
—
M2
M14
—
—
—
M13
—
—
M3
M10
NONROAD
2005
MO2C
—
—
MO2I
MO2D
MO4C
MO4I
MO4D
MP2C
—
MP2CA
MP2I
MP2D
MP4C
MP4I
MP4D
MS4C
MS4D
* NONROAD2004, the previous version, has additional marine designations that have
placeholders but are not used.
11
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Table 9
Deterioration Factors for Recreational SI Marine Engines
Technology Class
MO2C, MP2C
MO2I, MP2I
MO2D, MP2D
MP2CA
MO4C, MP4C
MO4I, MP4I
MO4D, MP4D
MS4C, MS4D
HC
0.00
0.03
0.03
0.26
0.05
0.03
0.03
0.26
CO
0.00
0.03
0.03
0.26
0.05
0.03
0.03
0.35
NOx
0.00
0.08
0.05
0.06
0.05
0.03
0.03
0.03
PM
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.26
Endnotes
1. Median life is defined as the midpoint of the scrappage curve at which half of the engines in
a given population cease to function and are scrapped. For more information, please refer to
the technical report on activity, load factors and median life (NR-005c) and the technical
report about scrappage (NR-007c).
2. See endnote 1.
3. "Updates to Technology Mix, Emissions Factors, Deterioration Rates, Power Distribution,
and Fuel Consumption Estimates for SI Marine Engines in the NONROAD Emissions
Inventory Model," EPA Memorandum From Mike Samulski to Docket EPA-HQ-OAR-2004-
0008, November 30, 2005.
4. U.S. EPA NONROAD Model Technical Report Addenda for Tier 2 Rulemaking Version.
March 24, 1999.
5. "Emission Modeling for Recreational Equipment," EPA Memorandum From Line Wehrly to
Docket A-98-01, November 13, 2000.
6. Final Regulatory Support Document: Control of Emissions from Unregulated Nonroad
Engines. Chapter 6, Office of Air and Radiation, EPA420-R-02-022, September 2002.
7. "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.
8. Proposed Control of Emissions from Nonroad Large Spark Ignition Engines, Recreational
Engines (Marine and Land-based), and Highway Motorcycles, Regulatory Support
Document, EPA420-D-01-004, September 2001, Chapter 6.
9. See endnote 8.
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10. "Deterioration Factors for Existing Technology, Gasoline, Outboard Marine Engines," EPA
memorandum from Mike Samulski to Chester J. France, Director, Engine Programs and
Compliance Division, March 4, 1996.
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Appendix 1
Deterioration Ratio Data for 1969 MY LDGTs
6.00 -,
5.00 -
4.00 -
3.00 -
2.00 -
1.00 -
0.00
c
HC deterioration ratio
•
average = 1 .58
average w/o outlier =1.11
•
* * t * *
20,000 40,000 60,000 80,000 100,000
m iles
CO deterioration ratio
4 00
3.00
2.00
1 00
0 00
average = 1 .31 *
average minus HC/NOx outlier = 1.39
•
•
•
"
•
0 20,000 40,000 60,000 80,000 100
m iles
000
NOx deterioration ratio
2 50
2.00
1.50
1 00
0.50
0 00
average =1.10
average minus outlier = 1.05 »
•
* * • . •
•
•
0 20,000 40,000 60,000 80,000 100
m iles
000
14
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