EPA420-R-99-009
Exhaust Emission Factors
for Nonroad Engine Modeling-
Spark Ignition
Report No. NR-OlOb
February 24, 1998
revised June 15, 1998
revised March 30, 1999
Megan Beardsley, Christian E. Lindhjem, and Craig Harvey
U.S. EPA Office of Mobile Sources, Assessment and Modeling Division
Purpose
This report describes and documents exhaust emission factors used for spark ignition (SI)
engines in EPA's NONROAD emission inventory model. It covers emission factors for engines
powered by gasoline, natural gas and liquefied petroleum gas.
EPA expects to recalculate most SI emission factors prior to release of the final version of
the NONROAD model. This report describes the emission factors that will be used for the draft
version of the model and lists the data sources that will be considered when calculating new
emission factors for the final model. When complete, the final emission factors will be similarly
documented and distributed for stakeholder review.
Additional EPA reports will describe other issues relating to emission factors including
NONROAD emission factors for evaporative emissions, crankcase emissions, spillage and other
non-exhaust emissions (NR-012), adjustments to emission rates due to variations in fuel and
temperature (NR-001), speciation of hydrocarbon emissions (NR-002), and adjustments to
emission rates as equipment deteriorates due to time and use (NR-011). Emission factors for
compression ignition (diesel) engines are covered in a separate report (NR-009).
Introduction
The U.S. EPA's NONROAD model computes county-level emission inventories for
nonroad engines. These calculations rely on emission factors — estimates of the amount of
pollution emitted by a particular type of equipment during a unit of use. Typically emission
factors for nonroad sources are reported in grams per horsepower-hour, but they also may be
reported in grams per mile, grams per hour, grams per gallon, etc.
nr-OlOb.wpd
-------
This report begins by describing emission factors used in prior models. It then briefly
describes our plans for pre-controlled and controlled SI exhaust emission factors in the draft and
final versions of NONROAD.
Appendix A provides information on the sources of emission factors. Appendix B has
two parts: (1) a large spreadsheet that lists the numerical value of emission factors that have been
used in prior inventories and that we intend to use for the draft version of NONROAD, and (2) a
guide to using the spreadsheet. Appendix C explains how NONROAD uses "technology groups"
to account for changes in emisssion factors over time.
The pollutants covered by this report include exhaust total hydrocarbons (HC), carbon
monoxide (CO), oxides of nitrogen (NOx), total particulate matter (PM), and brake specific fuel
consumption (BSFC). For nonroad engines all PM emissions are assumed to be smaller than 10
microns (PM10), and 92% of the PM from gasoline and diesel fueled engines is assumed to be
smaller than 2.5 microns (PM2.5). For gaseous fueled engines (LPG/CNG) 100% of the PM
emissions are assumed to be smaller than PM2.5. The NONROAD Reporting Utility allows the
user to select the desired size range.
As explained in NR-006, spark-ignition engine equipment population under 25
horsepower will be combined into one SCC per application to handle expected shifts in market
share between 2 and 4-stroke gasoline, LPG, and CNG engines. In the model, the distinction
between two- and four-stroke spark-ignition engine emission factors will be maintained using the
technology groups described in Appendix C of this report. In this current document, the SCC
distinction between 2 and 4-stroke gasoline, LPG, and CNG engines is maintained, however, in
the model, we will distinguish emission factors between them by using the technology group
methodology.
Background
Prior to the NONROAD model, there have been three major efforts to estimate nonroad
spark ignition emission inventories. We have relied heavily on these efforts in our work to select
emission factors for the draft version of NONROAD. The three inventories/models are:
• EPA's Nonroad Engine and Vehicle Emission Study ("NEVES"). [1] Published in
November, 1991, this study was mandated by Congress to determine whether nonroad
sources made a significant contribution to urban air pollution. The study covers
emissions from all nonroad engines and includes hydrocarbons (HC), carbon monoxide
(CO), nitrogen oxides (NOX), total particulates (PM), sulfur dioxide (SO2) and other
pollutants. It provides inventories for 19 ozone and 16 CO nonattainment areas.
• California Air Resources Board's nonroad model ("OFF-ROAD") [2], designed to
estimate nonroad emissions for the state of California only. A draft version of this model
was released August 1, 1997. The model covers HC, CO, NOX, PM, sulfur dioxide (SO2),
nr-OlOb.wpd
-------
and carbon dioxide (CO2) for all nonroad engines. ARB is currently revising much of its
work on nonroad modeling and the emission factors reported here may not reflect ARB's
most recent conclusions.
EPA's "Small Engine Model"—designed as an internal tool for evaluating various control
scenarios, EPA has used this model to estimate the effect of regulations on small spark-
ignition (SI) engines under 19 kW (25 hp) This model has evolved over time, but the pre-
control exhaust emission factors have not changed since the model was documented in
1995. [3] The model computes national-level inventories of nonroad HC, CO and NOx.
As detailed in Appendix A, the emission factors used in these prior efforts have been
based on a very small number of engine studies, particularly when compared to the large body of
data available for highway vehicles.
Emission Factor Categories
NEVES defines emission factors by the equipment use (i.e., by "application") but does
not assign different emission factors to engines of different sizes within the same application. On
the other hand, OFF-ROAD and the Small Engine Model define emission factors by engine size
(by horsepower in OFF-ROAD and by displacement in the Small Engine Model), but do not
assign different emission factors to engines used in different applications that are of the same
size. Given the structure of emission control regulations and the design similarities between
engines of the same horsepower used in various applications, we will likely define emission
factors primarily by power level for the final release of NONROAD. The NONROAD model
allows for the use of application-specific emission factors if there is sufficient information to
justify their use by the time of the final release. We expect to use application-based emission
factor categories only to distinguish handheld equipment, recreational marine engines and
selected recreational vehicles.
Due to time and resource constraints, inputs for the draft version of NONROAD will
retain some of the application-specific groupings given by NEVES and the Small Engine Model
as detailed below. However, we intend to recalculate emission factors for the final version of the
model based on the information given in Appendix A.
Accounting for In-Use Operation
Many nonroad engines operate under transient loads, but the engines are typically tested
with steady-state tests. While clear and significant differences between in-use transient and
steady-state emissions have been found for compression-ignition engines, such differences have
not been found conclusively for SI engines. Three studies have compared transient and steady-
state emissions in SI engines, but they have not found consistent results and in most cases
nr-OlOb.wpd
-------
transient and steady-state have produced equivalent emission factors. [4-6] At present, EPA
believes there is not sufficient information to justify an in-use transient adjustment factor for SI
engines, so the NONROAD model will use emission factors based on unadjusted steady-state test
results.
Emission Factors for Pre-control Engines-Draft Version
This section describes the emission factors that will be used for the draft version of
NONROAD. Because we plan to recalculate the pre-control emission factors for the final
version of the model, these emission factors should be considered placeholder values.
Gasoline Engines <25 hp
In general, for small gasoline engines, the draft version of the model will use emission
factors based on those in the Small Engine Model.[7] Like the Small Engine Model,
NONROAD will distinguish between handheld and non-handheld applications and distinguish
engines by size. The draft version of NONROAD separates overhead valve and side-valve four-
stroke engines and two-stroke engines through the use of technology types.
Gasoline engines > 25 hp
For larger gasoline engines, the draft version of the model will use emission factors from
NEVES. However, to simplify the entry of these placeholder values, and to move toward the
horsepower-based emission factors planned for the final version of the model, the draft version of
the inputs will not distinguish emission factors for specific applications such as "rubber-tired
dozer", but instead will use a single factor for all equipment in a general category such as
"construction" or "agriculture". Table 1 lists the specific NEVES emission factors to be used for
large engines in the draft version of NONROAD.
Table 1— NEVES sources of NONROAD large engine emission factors
Emissions Category in NONROAD (Draft
Version)
-All Construction > 25 hp
-All Industrial >25 hp
-All Lawn & Garden > 25 hp
-All Commercial >25 hp
-All Logging > 25 hp
-All Aircraft Support > 25 hp
-All Underground Mining >25 hp
-All Oil Field Equipment > 25 hp
-All Agricultural >25 hp
Based on NEVES Emission Factors for:
"Other Construction Equipment"
"Other General Industrial Equipment"
"Other Agricultural Equipment"
nr-OlOb.wpd
-------
NEVES used one average power level and one average emission factor for each
application. NEVES used emission factors from AP-42 which were calculated for the average
power level of each specific application. The draft version of the NONROAD model will
account for power level by using small and large engine emission factors for each application.
We expect this approach will provide results similar to NEVES and will serve as an acceptable
placeholder until new factors are calculated.
Recreational Marine Engines
Emission factors for recreational marine spark-ignition engines were taken from work
accomplished in support of the 1996 rulemaking for new emission standards for these engines.
[8] Table 2 shows how the outboard power level ranges used in the 1996 rulemaking analysis
were matched to the power levels used in NONROAD. The subsequent tables show the emission
rates by power range for precontrolled engines.
These emission factors have been changed from the sales-weighted averages used in the
June 1998 draft version of NONROAD to be straight averages of the final Ml - M4 technology
type data used in the 1996 rulemaking to be consistent with the method used for the controlled
engine types (M5 - Ml 5). For the final version of NONROAD we may return to using sales-
weighted averages of the baseline data for tech types Ml - M4.
Table 2 Mapping of Recreational Marine Engine Power Ranges
Outboard
PWC
EPA-RIA
<3.9hp
3.9-9.9
9.9-29.9
29.9-49.9
4Q Q 74 Q
74.9 - 99.9
QQ Q 1 4Q Q
149.9- 199.9
30 - 50 hp
50-75
NONROAD Model
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
0 - 50 hp
50- 175
nr-OlOb.wpd
-------
Inboard
100- 150 hp
150-200
>200
0- 100 hp
100- 175
>175
Table 3 Two-Stroke Outboard (SCC - 2282005010) Emission Factors for Precontrolled Engines
(Ml Tech Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
340.5
292.8
220.5
156.0
136.7
172.5
172.5
NOx
(g/kW-hr)
4.12
3.38
1.34
1.60
2.46
6.00
6.00
CO
(g/kW-hr)
531.5
450.0
404.0
310.0
313.0
420.0
420.0
Table 4 Four-Stroke Outboard (SCC - 2282005010) Emission Factors for Precontrolled Engines
(M4 Tech Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
121.2
29.71
18.36
20.00
11.00
10.00
10.00
NOx
(g/kW-hr)
4.93
5.20
7.98
10.00
10.00
12.00
12.00
CO
(g/kW-hr)
585.0
585.0
454.7
454.7
346.0
346.0
346.0
nr-OlOb.wpd
-------
Table 5 Personal Watercraft (SCC - 2282005015) Precontrolled Emission Factors (M2 Tech
Type. For 4-stroke see Tech Type Ml3 in Table 20)
NONROAD
power range
0 - 50 hp
50- 175
HC
(g/kW-hr)
166.7
224.6
NOx
(g/kW-hr)
1.70
0.94
CO
(g/kW-hr)
355.6
450.7
Table 6 Inboard (SCC - 2282010005) Precontrolled Emission Factors (M3 Tech Type)
NONROAD
power range
0 - 100 hp
100- 175
>175
HC
(g/kW-hr)
7.2
7.0
5.4
NOx
(g/kW-hr)
7.6
7.6
10.4
CO
(g/kW-hr)
175
175
174
Motorcycles. All-Terrain Vehicles (ATVsX Snowmobiles. Specialty Vehicles, and Underground
Mining Equipment
These engines differ significantly from other SI engines in their basic design, operating
characteristics, and emission rates. For 2-stroke engines the June 1998 draft version of the model
uses the emission factors from testing of two snowmobile engines by Southwest Research
Institute. The two engines tested were a 1995 Suzuki 440cc and a 1997 Fudi HI 488cc 2-stroke
engine yielding similar emissions levels.[9, 10] The average emissions for these two engines
were 206 g/kW-hr THC, 523 g/kW-hr CO, 0.63 g/kW-hrNOx, 3.22 g/kW-hr PM, and 0.665
kg/kW-hr BSFC. The June 1998 draft release of NONROAD assumes that 2-stroke versions of
all-terrain vehicles, motorcycles, and specialty vehicles all produce similar exhaust emission
rates to these 2-stroke snowmobiles. However, for BSFC for all of these 2-stroke engines have
been 0.79 kg/kW-hr (1.3 Ib/hp-hr) based on the NEVES assumptions for all other 2-stroke
equipment categories. [1] For the final release of NONROAD we plan to change the BSFC input
to 0.665 kg/kW-hr (1.09 Ib/hp-hr) mentioned above, unless even better data become available.
For 4-stroke recreational equipment engines NONROAD uses the same emission factors
as the 4-stroke overhead valve nonhandheld Class 2 engines shown below. The NEVES
emission factors for these applications are given in units of grams per hour which is problematic
for determining SOx emissions and allows for no differences between the several power levels of
these types of engines. The Small Engine Model used in the EPA Phase 1 rulemaking does not
consider these applications because they are exempted from the rulemaking. [7]
nr-OlOb.wpd
-------
Natural Gas/LPG Engines
For small engines (less than 25 hp) fueled by natural gas and Liquefied Petroleum Gas
(LPG), we plan to use the emission factors from NEVES because these are the only estimates for
which full documentation is available. For larger engines the June 1998 draft also used NEVES
emission factors, but more recent test data from CARB testing done at Southwest Research
Institute [14] allowed these model inputs to be updated in July 1998. The resulting emission
factors are shown below.
Table 7 Emission Factors for LPG and CNG engines
Engine Type
LPG < 25hp
LPG > 25hp
CNG < 25hp
CNG > 25hp
THC
(g/hp-hr)
3.19
1.68
3.19
1.68
CO
(g/hp-hr)
84.27
28.23
84.27
28.23
NOx
(g/hp-hr)
5.25
11.99
5.25
11.99
PM
(g/hp-hr)
0.06
0.05
0.06
0.05
BSFC
(Ib/hp-hr)
0.693
0.507
0.693
0.507
It should be noted that the above emission factors for under 25 hp engines appear to have
been incorrectly translated from the NEVES values due to assuming g/kw-hr units when the
NEVES values were in fact g/hp-hr. Thus, the draft final release of NONROAD will use the
following values unless more recent test data becomes available.
Table 7a Emission Factors for LPG and CNG engines - Corrected (to be included in a future
draft final release of NONROAD)
Engine Type
LPG < 25hp
LPG > 25hp
CNG < 25hp
CNG > 25hp
THC
(g/hp-hr)
4.28
1.68
4.28
1.68
CO
(g/hp-hr)
113
28.23
113
28.23
NOx
(g/hp-hr)
7.04
11.99
7.04
11.99
PM
(g/hp-hr)
0.05
0.05
0.05
0.05
BSFC
(Ib/hp-hr)
0.693
0.507
0.693
0.507
nr-OlOb.wpd
-------
Emission Factors for Pre-control Engines—Final Model
For the final version of the model, EPA plans to recompute emission factors for pre-
control engines. The new factors will be based on data described in Appendix A. This data
includes confidential data from manufacturers and baseline data from a number of small studies.
EPA requests immediate assistance in identifying additional sources of pre-control emissions
data and assistance in obtaining raw data for the studies listed. Raw data is needed to
demonstrate that the emissions information is aggregated properly.
Controlled Emissions-Draft and Final
In addition to estimating emissions from pre-controlled engines, the NONROAD model is
designed to account for the effect of federal emissions standards. The model does not cover
California emission standards and federal standards that are not yet final. However, because
EPA expects to finalize the proposed Phase 2 small engine rule before the release of the final
NONROAD model, the proposed Phase 2 standards have been included in the draft version of
the model. Thus, NONROAD will include emission factors under three regulations:
• Emissions for New Nonroad Spark Ignition Engines at or below 19 Kilowatts. ("Small
Engine Rule, PhaseF) [11]
• Phase 2: Emission Standards for New Nonroad Spark-Ignition Engines At or Below 19
Kilowatts "Small Engine Rule Phase II" [12]
• Final Rule for New Gasoline Spark-Ignition Marine Engines; Exemptions for New
Nonroad Compression-Ignition engines at or Above 37 Kilowatts and New Nonroad
Spark-Ignition Engines at or Below 19 Kilowatts ("Marine Rule") [13]
NONROAD will use the brake-specific fuel consumption (BSFC) and the HC, CO, and
NOX emission factors that are in the regulatory support documents for the rules listed above.
The NONROAD input structure for handling the phase-in of new emission standards and
technologies is explained in Appendix C. The control emission factors for marine engines are
listed in the spreadsheet Techl.wk4 and the technology fractions are listed in the workbook
Techmix.wk4. The Phase 1 emission factors for small SI engines are from Appendix F of the
Phase 2 regulatory support document, and are listed as "new engine exhaust" values in Table F-
07. The Phase 2 emission factors are from the Phase 2 final rule. NONROAD's technology
fractions for these engines will follow the sales mixes for Phase 1 and Phase 2 as listed in Tables
F-03 and F-04 of the RSD appendix. The Phase 2 final rule did not include handheld engines, so
if those standards are changed from what was assumed in this report, the final version of the
model will reflect those changes.
Effect of the Federal Rulemaking on SI Recreational Marine Engines
nr-OlOb.wpd
-------
To determine the effect of the Federal rulemaking for these types of engines, technical
types were defined to reflect new technologies that would be employed to meet the emission
levels required. These new technologies would be employed to various degrees to reflect the
phase-in of the new emission standards. Technical types were defined to incorporate the
emission reductions expected and the phase-in of the standards.
Outboard Engine (SCC - 2282005010^) Emissions
The precontrolled outboard two-stroke and four-stroke engines were defined by the
technical types Ml and M4. New engine technical types were defined to account for the new
standards and allows for phase-in of the standards. The initial and the phase-in fleet fractions
were estimated for all of the technical types.
Table 8 Two-Stroke Outboard (SCC - 2282005010) Emission Factors with Carburetor &
Ignition Modifications (M5 Tech Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
340.50
292.80
216.50
156.00
136.67
155.00
155.00
NOx
(g/kW-hr)
4.12
3.38
1.34
1.60
2.46
11.00
11.00
CO
(g/kW-hr)
650.0
650.0
577.5
566.0
370.0
388.0
388.0
nr-OlOb.wpd
10
-------
Table 9 Two-Stroke Outboard (SCC - 2282005010) Emission Factors with Modifications and
Catalyst (M6 Technical Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
165.8
142.6
107.4
75. .97
66.55
84.00
84.00
NOx
(g/kW-hr)
3.43
2.82
1.12
1.33
2.05
5.00
5.00
CO
(g/kW-hr)
417.6
353.6
317.4
243.6
245.9
330.0
330.0
Table 10 Two-Stroke Outboard (SCC - 2282005010) Emission Factors with Catalyst &
Electronic Fuel Injection (M7 Technical Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
61.12
52.55
39.58
28.00
26.50
25.67
25.00
NOx
(g/kW-hr)
20.65
16.95
6.73
8.00
9.50
11.00
11.00
CO
(g/kW-hr)
625.8
529.8
475.7
365.0
342
325.0
325.0
nr-OlOb.wpd
11
-------
Table 11 Two-Stroke Outboard (SCC - 2282005010) Emission Factors with Electronic Fuel
Injections (M8 Technical Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
61.12
52.55
39.58
28.00
26.50
25.67
25.00
NOx
(g/kW-hr)
20.65
16.95
6.73
8.00
9.50
11.00
11.00
CO
(g/kW-hr)
625.8
529.8
475.7
365.0
342.5
325.0
325.0
Table 12 Direct-Injection Type A Outboard (SCC - 2282005010) Emission Factors (M9
Technical Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
77.21
66.39
50.00
38.00
43.00
54.00
51.00
NOx
(g/kW-hr)
15.34
12.59
5.00
5.00
5.00
5.00
5.00
CO
(g/kW-hr)
577.5
489.0
439.0
261.0
256.0
409.5
381.0
nr-OlOb.wpd
12
-------
Table 13 Direct-Injection Type B Air Assisted Outboard (SCC - 2282005010) Emission Factors
(Ml 5 Technical Type)
NONROAD
power range
0-3 hp
3- 11
11-25
25-50
50- 100
100- 175
>175
HC
(g/kW-hr)
77.21
66.39
50.00
38.00
43.00
54.00
51.00
NOx
(g/kW-hr)
15.34
12.59
5.00
5.00
5.00
5.00
5.00
CO
(g/kW-hr)
577.5
489.0
439.0
261.0
256.0
409.5
381.0
The technical types were used to allow the phase-in of the new engines. This phase-in
was estimated to be unique by the following power levels, 0-3 hp, 3-11, 11-25, 25-50, 50-100,
100-175, and greater than 175 hp. No changes from the initial 90% two-stroke and 10% four-
stroke outboard fleet fractions is estimated to occur for the less than 3 horsepower outboard
engines. The other fleet fraction estimates are shown below derived from information generated
for the rulemaking.
Table 14 Technical Type Fleet Fractions for 3 - 11 hp Outboard Engines
Year
1900
1997
2000
2003
2005
Ml
0.957
0.870
0.537
0.276
0.260
M4
0.043
0.130
0.463
0.724
0.724
M5
0.000
0.000
0.000
0.000
0.016
M6
0.000
0.000
0.000
0.000
0.000
M7
0.000
0.000
0.000
0.000
0.000
M8
0.000
0.000
0.000
0.000
0.000
M9
0.000
0.000
0.000
0.000
0.000
M15
0.000
0.000
0.000
0.000
0.000
nr-OlOb.wpd
13
-------
Table 15 Technical Type Fleet Fractions for 11 - 25 hp Outboard Engines
Year
1900
2002
2003
2004
2005
2006
Ml
0.989
0.962
0.780
0.640
0.633
0.091
M4
0.011
0.038
0.216
0.349
0.356
0.620
M5
0.000
0.000
0.004
0.011
0.011
0.011
M6
0.000
0.000
0.000
0.000
0.000
0.000
M7
0.000
0.000
0.000
0.000
0.000
0.000
M8
0.000
0.000
0.000
0.000
0.000
0.000
M9
0.000
0.000
0.000
0.000
0.000
0.277
M15
0.000
0.000
0.000
0.000
0.000
0.000
Table 16 Technical Type Fleet Fractions for 25 - 50 hp Outboard Engines
Year
1900
1998
2001
2002
2003
2005
Ml
1.000
0.972
0.683
0.105
0.098
0.085
M4
0.000
0.028
0.049
0.049
0.049
0.063
M5
0.000
0.000
0.000
0.000
0.007
0.007
M6
0.000
0.000
0.000
0.000
0.000
0.000
M7
0.000
0.000
0.000
0.000
0.000
0.000
M8
0.000
0.000
0.268
0.268
0.268
0.268
M9
0.000
0.000
0.000
0.578
0.578
0.578
M15
0.000
0.000
0.000
0.000
0.000
0.000
Table 17 Technical Type Fleet Fractions for 50 - 100 hp Outboard Engines
Year
1900
1999
2000
Ml
1.000
0.950
0.917
M4
0.000
0.050
0.050
M5
0.000
0.000
0.033
M6
0.000
0.000
0.000
M7
0.000
0.000
0.000
M8
0.000
0.000
0.000
M9
0.000
0.000
0.000
M15
0.000
0.000
0.000
nr-OlOb.wpd
14
-------
Table 18 Technical Type Fleet Fractions for 100- 175 hp Outboard Engines
Year
1900
1997
1998
1999
2003
2004
Ml
1.000
0.988
0.954
0.575
0.302
0.000
M4
0.000
0.000
0.000
0.000
0.000
0.000
M5
0.000
0.000
0.034
0.034
0.035
0.035
M6
0.000
0.000
0.000
0.000
0.267
0.267
M7
0.000
0.000
0.000
0.000
0.000
0.000
M8
0.000
0.012
0.012
0.012
0.012
0.314
M9
0.000
0.000
0.000
0.379
0.384
0.384
M15
0.000
0.000
0.000
0.000
0.000
0.000
Table 19 Technical Type Fleet Fractions for >175 hp Outboard Engines
Year
1900
1997
1998
2004
Ml
1.000
0.967
0.234
0.000
M4
0.000
0.000
0.000
0.000
M5
0.000
0.000
0.000
0.000
M6
0.000
0.000
0.000
0.000
M7
0.000
0.000
0.000
0.000
M8
0.000
0.033
0.033
0.290
M9
0.000
0.000
0.733
0.710
M15
0.000
0.000
0.000
0.000
Personal Water Craft (SCC - 2282005015} Emissions
Personal Water Craft (PWC) emissions are characterized by three technical types, 2-
stroke (labeled M2), 4-stroke (M13), and 2-stroke with major modifications (M14). Type M2
has the emission factors given above in Table 4.
Table 20 Personal Watercraft (SCC - 2282005015) 4-Stroke Emission Factors (M13)
NONROAD
power range
0 - 50 hp
50- 175
HC
(g/kW-hr)
16.13
16.98
NOx
(g/kW-hr)
6.33
7.00
CO
(g/kW-hr)
354.0
326.2
nr-OlOb.wpd
15
-------
Table 21 Personal Watercraft (SCC - 2282005015) 2-Stroke with Major Modifications Emission
Factors (M14)
NONROAD
power range
0 - 50 hp
50- 175
HC
(g/kW-hr)
166.70
224.55
NOx
(g/kW-hr)
1.70
0.94
CO
(g/kW-hr)
355.6
450.7
The first two tables below show the PWC technology phase-in fractions that are in the
draft NONROAD model as of December 1998. The 25-50hp phase-in fractions come directly
from the spreadsheets used in the June 1996 Regulatory Impact Analysis, except for 2002 for
which the RIA had fractions of 0.680, 0.320, and 0.000 for M2, M13, and M14. The 0-25hp
table requires some explanation because the RIA assumed there were no engines under 30hp. As
described in technical report NR-006a, "Nonroad Engine Population Estimates," the PSR data
that NONROAD uses as a basis for most of the engine population inputs does indicate some
engines in that lower power range, including some 4-strokes. The table below for 0-25hp PWC
engines takes into account those PSR population fractions.
Table 22 Estimate Phase-in of New Personal Water Craft Engines 0-25 hp
Year
1900
2005
M2
0.218
0.075
M13
0.782
0.925
M14
0.000
0.000
Table 23 Estimate Phase-in of New Personal Water Craft Engines 25-50 hp
Year
1900
1999
2002
2003
2004
2005
M2
1.000
0.680
0.680
0.496
0.496
0.075
M13
0.000
0.000
0.136
0.320
0.504
0.925
M14
0.000
0.320
0.184
0.184
0.000
0.000
nr-OlOb.wpd
16
-------
Table 24 Estimate Phase-in of New Personal Water Craft Engines >50 hp
Year
1900
1999
2000
2001
2002
2004
M2
1.000
0.177
0.177
0.177
0.177
0.038
M13
0.000
0.092
0.259
0.533
0.823
0.962
M14
0.000
0.731
0.564
0.291
0.000
0.000
Inboard Engines (SCC - 2282010005s) Emissions
There are no assumed improvements in emissions from this application as a result of the
Federal rulemaking.
Effect of Federal Rulemaking on Small (<19kW) SI Engines
New Federal regulations will be in place for most categories of small spark-ignition
engines. Phase 1 of the regulations starts with 1997 regulatory model year which begins
September, 1996 and provides allowances for special circumstances and manufacturers. The
NONROAD model accounts for this by assuming that some of the engines produced in the
calendar year 1996 meet the Phase 1 standard. The Phase 2 standard phases-in over 4 years for
handheld (Class ffi-V), 1 year for Class I, and 5 years for Class II new engines built in 2001 or
later. These new standards are considered in NONROAD through the use of technology types.
The technology types meeting the new standards (with appropriately lower emission factors) then
gain market share during the appropriate model years which represent the start year of the
regulations.
Engine standards are determined by the class of the engine (I - V) which is determined by
the use of the engine, handheld or nonhandheld, and engine displacement. The five classes were
associated with application and power level in NONROAD as described in another report (NR-
006) to closely simulate the expected effect of this rulemaking.
In order to account for the effect of the rulemaking and the phase-in of the new standards,
engines meeting the new standards were defined by technical types as described below.
Handheld engines (Classes ffi-V) are not expected to include any 4-stroke engines (but emission
factors are supplied for users) but are expected to include a small fraction of catalyst equipped
engines. Nonhandheld engines include both 2 and 4-stroke engines, but manufacturers are
expected to build only 4-stroke engines with the advent of the new regulations. Nonhandheld 4-
nr-OlOb.wpd
17
-------
stroke engine production is split between two technical types, side-valve and overhead valve
systems, which have been shown to exhibit significantly different emission characteristics.
New Engine Emission Factors
Emission rates from these engines are determined as a function of new engine emissions.
The emission rates for new engines have been determined from testing and the expected effects
of new emission standards, and the estimates for NONROAD are shown below.
Table 25; Class HI Engine Emissions for New Engines (g/kW-hr)
Engine Tech Type
G2H3 (gas 2-stroke handheld Class III, baseline)
G2H31 (Phase 1)
G2H3C1 (Phase 1 with catalyst)
G2H32 (Phase 2)
G2H3C2 (Phase 2 with catalysts)
HC
350
295
295
63.7
42.5
CO
964
644
644
644
644
NOx
1.3
1.05
1.05
1.97
5.0
PM
7.7
7.7
7.7
7.7
7.7
BSFC
830
720
720
500
500
Table 26; Class IV Handheld New Engine Emissions (g/kW-hr)
Engine Tech Type
G2H4 (gas 2-stroke handheld Class IV, baseline)
G2H41 (Phase 1)
G2H4C1 (Phase 1 with catalyst)
G4H41 (Phase 1 4-stroke)
G2H42 (Phase 2)
G2H4C2 (Phase 2 with catalysts)
G4H42 (Phase 2 4-stroke)
HC
350
241
241
30
63.7
42.5
30
CO
964
546.5
546.5
715.6
546.5
546.5
715.6
NOx
1.26
0.688
0.688
2.40
1.97
5.00
2.40
PM
7.7
7.7
7.7
0.06
7.7
7.7
0.06
BSFC
830
720
720
515
500
500
515
nr-010b.wpd
18
-------
Table 27; Class V Handheld New Engine Emissions (g/kW-hr)
Engine Tech Type
G2H5 (gas 2-stroke handheld Class V, baseline)
G2H51 (Phase 1)
G2H5C1 (Phase 1 with catalyst)
G2H52 (Phase 2)
G2H5C2 (Phase 2 with catalysts)
HC
214
161
161
76.93
56.14
CO
696
470.9
470.9
470.9
470.9
NOx
1.3
2.436
2.436
2.38
5.00
PM
7.7
7.7
7.7
7.7
7.7
BSFC
560
529
529
500
500
Table 28; Class I Nonhandheld New Engine Emissions (g/kW-hr)
Engine Tech Type
G2N1 (gas 2-stroke nonhandheld Class I, baseline)
G4N1S (gas, side-valved, 4-stroke nonhandheld Class I,
baseline)
G4N1O (gas, overhead-valved, 4-stroke nonhandheld Class
I, baseline)
G2N11 (2-stroke, Phase 1)
G4N1S1 (Phase 1 side-valved, 4-stroke)
G4N1O1 (Phase 1 overhead valved 4-stroke)
G4N1SC1 (Phase 1 side-valved, 4-stroke with catalyst)
G4N1S2 (Phase 2 side-valved)
G4N1O2
(Phase 2 overhead valved)
HC
278.8
52.3
17.96
161
11.27
11.27
11.27
10.63
8.22
CO
651.5
577.8
548.3
603
474.3
470.9
474.3
474.3
470.9
NOx
0.39
2.68
2.41
5.36
4.83
4.34
4.83
3.17
2.46
PM
7.7
0.06
0.06
7.7
0.06
0.06
0.06
0.06
0.06
BSFC
529
830
603
529
560
475
560
560
475
nr-010b.wpd
19
-------
Table 29; Class II Nonhandheld New Engine Emissions (g/kW-hr)
Engine Tech Type
G2N2 (gas 2-stroke nonhandheld Class II, baseline)
G4N2S (gas, side-valved, 4-stroke nonhandheld Class II,
baseline)
G4N2O (gas, overhead-valved, 4-stroke nonhandheld Class
II, baseline)
G4N2S1 (Phase 1 side-valved, 4-stroke)
G4N2O1 (Phase 1 overhead valved 4-stroke)
G4N2S2 (Phase 2 side-valved)
G4N2O2 (Phase 2 overhead valved)
HC
278.8
12.96
6.97
7.37
6.97
7.37
5.58
CO
651.5
578
548.3
519
472.8
519
472.8
NOx
0.39
2.76
4.69
6.03
4.69
6.03
3.72
PM
7.7
0.06
0.06
0.06
0.06
0.06
0.06
BSFC
529
570
570
528
450
528
450
nr-010b.wpd
20
-------
References
[1] "Nonroad Engine and Vehicle Emission Study" (NEVES), U.S. EPA, Office of Air and
Radiation, 21A-2001. November, 1991.
[2] "Documentation of Input Factors for the New Off-Road Mobile Source Emissions Inventory
Model," ("Inputs...") Energy and Environmental Analysis, Inc. for California Air Resources
Board. February, 1997.
[3] "Documentation of the OMS Small Gasoline Engine Spreadsheet System, Final Technical
Memorandum," Dan Bowman, TRC Environmental Corporation. August 1995.
[4] "Emissions Analysis of Small Utility Engines." Sun, X., et al. SAE paper 952080. 1995.
[5] "Emissions from 4-Cycle Walk-Behind-Mower Engines: Test Cycle Effects." Gabele, Peter.
SAE Paper 972793. 1997
[6] "Transient versus steady-state test procedure evaluation of 4-cycle utility engines,"
Carpenter, T., Buszkiewicz, T., Trimble, T. EPA regulation negotiation test procedure task
group, November, 1994. EPA Air Docket A-93-29, Docket Item U-M-27 and "Final Report -
Handheld Subgroup of the Test Procedure Task Group", EPA Air Docket A-93-29, Docket Item
II-M-40.
[7] "Regulatory Support Document, Control of Air Pollution, Emission Standards for New
Nonroad Spark-ignition Engines at or below 19 Kilowatts," U.S. EPA, May 1995, EPA Air
Docket, Docket Item # V-B-01.
[8] "Regulatory Impact Analysis: Control of Air Pollution Emission Standards for New
Spark-Ignition Marine Engines," U.S. EPA, October, 1996.
[9] "Emissions from snowmobile engines using bio-based fuels and
lubricants - draft final report" by Jeff J. White and James N. Carroll, SwRI
report #7383, August 1997, prepared for State of Montana Department of
Environmental Quality.
[10] "Development of Snowmobile Test Cycle - Final Report", SwRI report #
7574, by Janet P. Buckingham, Jeff J. White, and James N. Carroll, March
1996, prepared for the International Snowmobile Manufacturers
Association
[11] 60 FR 34581, July 3, 1995.
nr-OlOb.wpd 21
-------
[12] "Regulatory Support Document, Phase 2: Emission Standards for New Nonroad Spark
Ignition Engines At or Below 19 Kilowatts". U.S. EPA, Office of Air and Radiation, December
1997.
[13] 61 FR 52087, October 4, 1996.
[14] "Three-Way Catalyst Technology for Off-Road Equipment Powered by Gasoline and LPG
Engines; Volume 2, Cost-Effectiveness Analysis," Jeff J. White, Melvin N. Ingalls, Lit-Mian
Chan, Southwest Research Institute, May 1998.
nr-OlOb.wpd 22
-------
Appendix A
Detailed Discussion of Pre-Control Emission Factors for
Spark Ignition Engines
This appendix provides a detailed description of the data sources used for pre-control
emission factors for spark ignition (SI) engines in previous nonroad emission inventories. The
Appendix also describes the pre-control emission factors that will be used in the draft version of
NONROAD and it lists additional studies that EPA will consider when recalculating pre-control
emissions factors for the final version of NONROAD. The appendix is divided into four
sections:
• Emission Factors that Apply to All Spark Ignition Engines
• Emission Factors for 2-stroke Gasoline Engines
• Emission Factors for 4-stroke Gasoline Engines
• Emission Factors for Natural Gas/Petroleum Gas Engines
Note: This appendix uses the following abbreviations:
ARB (California) Air Resources Board
ATV All-Terrain Vehicle
BSFC brake-specific fuel consumption
CO carbon monoxide
CO2 carbon dioxide
EEA Energy and Environmental Analysis, Inc.
EMA Engine Manufacturers Association
EPA U.S. Environmental Protection Agency
FC fuel consumption
HC hydrocarbons
man. manufacturers
na not available
NEVES (U.S. EPA) Nonroad Engine and Vehicle Emission Study
NMHC non-methane hydrocarbons
NOX nitrogen oxides
OHV overhead valve
OPEI Outdoor Power Equipment Institute
PPEMA Portable Power Equipment Manufacturers Association.
PM paniculate matter
rpm revolutions per minute
TSD technical support document
SwRI Southwest Research Institute
nr-OlOb.wpd Al
-------
SO2 sulfur dioxide
UM University of Michigan
WBM walk-behind (lawn) mower
All Spark Ignition Engines
Sulfur Dioxide Emission Factors
Sulfur dioxide emissions are rarely measured. Instead, they typically are calculated from
fuel consumption and fuel sulfur content. We have retained this approach for the NONROAD
inputs. Sulfur dioxide emission factors for gasoline engines are calculated using the following
equation:
SO2 = (BSFC * 453.6 - HC) * Sulfur Level * 2
where
SO2 is in g/hp-hr
BSFC is in Ib/hp-hr
453.6 is the conversion factor from Ibs to g
HC is hydrocarbon emissions in g/hp-hr
Sulfur Level for gasoline is 0.00034 weight fraction
2 is the grams of SO 2 formed from a gram of sulfur
The calculation for CNG/LPG engines is similar, with an average fuel sulfur content of
0.00003. This equation differs from the equation used for diesel engines in that all the sulfur is
assumed to become sulfur dioxide. This may be a simplification because a relatively small
fraction of sulfur (roughly 2%) can be converted in the engine to sulfur trioxide. Sulfur trioxide
or the paniculate derived from sulfur trioxide is not measured from gasoline engines, so there is
no basis upon which to determine a sulfur related particulate emission rate. Therefore we ignore
the small effect of particulate sulfur for the sulfur dioxide calculation.
The SO2 emission factors are calculated for NONROAD's input data files based on the
default fuel sulfur content listed here. NONROAD users may use the model interface to adjust
the fuel sulfur content without changing the input files.
Carbon Dioxide
The NONROAD model does not require emission factor inputs for carbon dioxide. CO2
emissions are estimated by the model based on fuel consumption using the equation below. Note
that there is currently no subtraction of the carbon in exhaust HC emissions, since this is a
negligible portion of the carbon for most engines. However, for 2-stoke engines a substantial
nr-OlOb.wpd A2
-------
portion of the fuel (up to one third) goes into exhaust HC instead of CO2. We plan to address
this in the final release of the model. The most likely approach is to simply subtract exhaust
THC from BSFC in the following equation.
CO2 = BSFC * 453.6 *0.87 * (44/12)
where
CO2 is in g/hp-hr
BSFC is in Ib/hp-hr
453.6 is the conversion factor from Ibs to grams
0.87 is the carbon mass fraction of gasoline
44/12 is the ratio ofCO2 mass to carbon mass
Fuel Consumption
There are few studies that also measured fuel consumption in nonroad engines. NEVES
does not explicitly report fuel consumption, but fuel consumption is reported for selected sources
in the NEVES Appendix I. ARB reports fuel consumption and cites two studies: (1) ARB's 4-
stroke factors for overhead valve (OHV) engines less than 25 horsepower and for side-valve
engines of all horsepower are from an SwRI report.[1] (2)ARB's fuel consumption factors for
OHV 4-stroke gasoline engines greater than 25 horsepower were based on pre-control on-road
engine BSFC.[2] The small engine model lists fuel consumption for engines <25 hp, but the
source of this estimate is not clear.
EPA intends to improve fuel consumption factors in the final version of the model;
however, due to time constraints, the draft version of the model will use BSFC data adapted from
that available in NEVES.
Two Stroke Gasoline Engines
Table Al lists the sources of data used for emission factors of two-stroke engines in
previous inventories and planned for the NONROAD draft model. The table also lists studies
that provide additional data that EPA will consider when recalculating emission factors for the
final version of the model. The references listed in the table are described below.
[1] White, Carroll, Hare and Lourenco. Emission Factors for Small Utility Engines.
Southwest Research Institute and California Air Resources Board. 1991. (SAE Paper 910560).
[2] "Documentation of Input Factors for the New Off-Road Mobile Source Emissions
Inventory Model", Energy and Environmental Analysis, Inc., for California Air Resources Board,
February, 1997. Appendix A.
nr-OlOb.wpd A3
-------
Table Al-Data Sources for Baseline Emission Factors for Two-Stroke Gasoline Engines
Equipment
Description
General non-
handheld
(>=3 hp)
Offroad
Motorcycles
ATVs
(all hp)
Golf carts,
Minibikes and
Specialty
Carts (>3 hp)
(<3 hp)
Snowmobiles
(all hp)
Outboard
marine
engines
(all hp)
Personal
Watercraft
(all hp)
Non-handheld
(<3 hp)
Handheld
Emission Factor Data Sources given in
Table A2 and Used by:
NEVES
A
C,?
c
C
D
A,E,F
na
A
G
ARE
A,B
C
A,B
G
D
A,E
na
G
G
Small
Engine
Model
A
na
A
A
na
na
na
A
G (mod-
ified)*
Nonroad
Draft
Version
A
C,?
A
G
D
A,E,F
9
G
G (mod-
ified)*
Notes
ARB includes a
deteriorated engine
(B) in PM estimate.
It is not clear where
NEVES PM
estimates are from,
but we will use them
for draft.
Operating at lower
rpm, these engines
are more like
lawnmowers than
motorcycles.
NEVES and ARB
use (A) for PM.
NEVES uses (F) for
SO2
For draft, calculate
HC, CO, NOX and
SOX from new data.
UseBSFCandPM
from outboards.
Additional
Data
Sources
1,2
3
4,5
6,7
8
9, 10, 11
12-18
* The small engine model documentation states that the emission factors for handheld engines
were modified based on manufacturers data.
nr-OlOb.wpd
A4
-------
Table A2-Emission Factor Data Sources Listed in Table Al for Two-Stroke Gasoline Engines
Reference
Code
A
B
C
Number
of
Engines.
Tested
1
1
?
Age and
Application
of Engines
WBM
11 -year-old
WBM
?
Horse-
power
of
engine
5hp
2.4 hp
?
Testing
lab
SwRI
SwRI
?
Emissio
ns
measure
d
HC,
CO,
NOX,
PM,FC
HC,
CO,
NOX,
C02,
PM,FC
HC,
CO,
NOX
Citation and notes
"Technical Support Document for California Exhaust
Emission Standards and Test Procedures for 1994 and
Subsequent Model-Year Utility and Lawn and Garden
Equipment Engines." (ARB TSD) California Air Resources
Board. Attachment C to ARB Mailout #90-64. December
1990. p. 31. Some of this data also is reported in SAE 910560.
Carroll, James N. Emission Tests of In-Use Small Utility
Engines, Task in Report Non-Road Source Emission Factors
SwRI 3426-006 for EPA, September 1991.
ARB Mailout #90-58, "Proposal to control emissions from
Off-Road Motorcycles," September 7, 1990. The mail-out
does not describe the source of the emission factors.
According to Ingalls, M. "Nonroad Emission Factors, Interim
Report" SwRI 08-3426-005. February 1991, for NEVES, the
mailout factors were converted to g/hr based on average speed
of 25 mph.
nr-OlOb.wpd
A5
-------
D
E
F
G
3
25
4
50
including
legible
data on:
8
11
2
snow-mobiles
outboard
engines
outboard
engines
chainsaws
chainsaws
trimmers
?
?
?
1-3 hp
3-6 hp
0-1 hp
SwRI
EMMA
SwRI
PPEMA
HC,
CO,
NOX,
PM,FC
HC,
CO,
NOX,
BSFC
HC,
CO,
NOX,
SOX
HC,
CO,
NOX
AP-42, 4th Edition, Sept. 1985. U-8. Data is based on: C.T.
Hare, KJ. Springer, T.A. Huls, "Snowmobile Engine
Emissions and Their Impact", SAE 740735, 1974. Converted
to g/hp-hr by dividing by an average hp of 5.8.
NEVES
Hare C.T. and K. J. Springer. "Exhaust Emissions from
Uncontrolled Vehicles and Related Equipment Using Internal
Combustion Engines. Part II, Outboard Motors. Final
Report." Southwest Research Institute. January 1973.
Heiden Report cited in "ARE TSD". The closest in EPA
dockets is Untitled, A-93-25 II-D-23. Only part of this data is
legible EPA requests assistance locating this report.
nr-OlOb.wpd
A6
-------
Table A3—Known Additional Data Sources Listed in Table Al for Gasoline Two-Stroke Engines
Reference
Code
1
2
3
4
5
6
7
Number
of
Engines.
Tested
2
2
1
8
1
1
7
Age and
Application
of Engines
7
7- and 10-
year-old
mower*
moped/ATV
snowmobile
snowmobile
outboard
marine
outboard
marine
Horse-
power
of
engine
3,4.5
7
6
?
50 hp
9.9 hp
7
Testing
lab
UM
UM
SwRI
man.
SwRI
EPA
man.
Emissions
measured
HC, CO,
NOX, CO2
HC, CO,
NOX
NMHC,
CO, NOX,
PM
HC+ NOX,
CO
HC, CO,
NOX, PM,
BSFC
HC, CO,
NOX, FC
HC, CO,
NOX
Citation and notes
Sun, X., et al., "Emissions Analysis of Small Utility Engines."
SAE paper 952080. 1995.
Charmley, William. "Memorandum: U/M data on in-use two
strokes" 1993. (Docket A-93-25/II-B-03)
Hare, C.T., and JJ. White. "Toward the Environmentally-
Friendly Small Engine: Fuel, Lubricant, and Emission
Measurement Issues," 1991. SAE 91 1222 in SAE P-254.
"Regulatory Strategies for Off-Highway Equipment.
Addendum: Potential Emission Control Regulations for
Snowmobiles, Preliminary Draft" EEA for ARB, February
1992, p. A-12. Data from International Snowmobile Industry
Association.
White, Jeff J. et al. "Baseline and Controlled Exhaust
Emissions from Off-Highway Vehicle Engines," SAE 931541,
(SwRI/ARB 1993) December, 1993.
"Memorandum: Exhaust Emission Testing of a Two-Stroke
and a Four-Stroke Marine Engine; Results and Procedures,"
Mike Samulski to Docket #A-92-28.
Manufacturer testing of 56 engine families. (Confidential
business data.)
nr-OlOb.wpd
A7
-------
8
9
10
11
12
?
1
O
1
1
PWC
non-handheld
?
11 -year-old
WBM*
?
?
2hp
1.2,
2.2,
2.3 hp
2.4 hp
1.25
hp
man.
SwRI
UM
SwRI
UM
HC, CO,
NOX
HC, CO,
NOX, PM
HC, CO,
NOX, CO2
HC, CO,
NOX,
C02, PM,
FC
HC, CO,
NOX, C02
Manufacturer testing of 10 engine families (Confidential
business data)
Hare, C.T., KJ. Springer. "Exhaust Emissions from
Uncontrolled Vehicles and Related Equipment using Internal
Combustion Engines, Final Report Part 4, Small Air-Cooled
Spark Ignition Utility Engines." May 1973. Table 19.
Sun, X., et al., "Emissions Analysis of Small Utility Engines."
SAE paper 952080. 1995.
Carroll, James N. Emission Tests of In-Use Small Utility
Engines, Task in Report Non-Road Source Emission Factors
SwRI 3426-006 for EPA, September 1991.
Sun, X., et al., "Emissions Analysis of Small Utility Engines."
SAE paper 952080. 1995.
nr-OlOb.wpd
A8
-------
13
14
15
16
17
18
24
including
O
3
6
O
9
5
O
O
1
1
handheld
blowers
blowers
trimmers
chainsaws
chainsaws
1-7-year-old
handheld
engines*
string
trimmers
chainsaws
4-year-old
string
trimmer*
string-
trimmer
0-1 hp
1-3 hp
0-1 hp
0-1 hp
1-3 hp
?
0-1 hp
1.4hp
0.5 hp
?
Poulan/
Weed
Eater
SwRI
PPEM
A
PPEM
A
SwRI
SwRI
HC, CO,
NOX, FC
HC, CO,
NOX
HC, CO,
NOX
HC, CO
HC, CO,
NOX,
CO2, PM,
FC
HC, CO,
NOX, FC
Liechty, Kim. "Investigation of In-Use Deterioration of
Exhaust Emissions from Small Single-Cylinder Two Stroke-
Cycle Engines," SAE 952137.
Carroll, J.N., JJ. White. "Emission Testing of In-Use
Handheld Engines" SwRI 08-4855-21 1 . (EPA Docket A-93-
25//U-A-06).
"PPEMA/AQC In-Use Emissions Test Report: 25 cc String
Trimmers." 1993. (Docket A-93-25/II-D-23, attach 2)
EPA/PPEMA "In-Use" Emissions Test Report. (Docket A-93-
25/U-D-23, attach. 3)
Carroll, James N. "Emission Tests of In-Use Small Utility
Engines, Task in Report Non-Road Source Emission Factors"
SwRI 3426-006 for EPA, September 1991.
J.P. Latusek and R.W. Burrahm, "Conversion of Two Small
Utility Engines to LPG Fuel", 1993, SAE 932447. Note, data
is from a 2-mode test.
*In-use testing listed for reference only. EPA does not plan to include this data when calculating emission factors for new engines.
nr-OlOb.wpd
A9
-------
4-Stroke Gasoline Engines
Table A4 lists references for data used for four-stroke gasoline engines in previous
inventories and planned for the NONROAD draft model. The table also lists studies that provide
additional data that EPA will consider when recalculating emission factors for the final version
of the model.
Tables A5 and A6 describe the studies referenced in Table A4.
nr-OlOb.wpd A10
-------
Table A4-Data Sources for Baseline Emission Factors for Four-Stroke Gasoline Engines
Equipment
Description
Off-Road
Motorcycles,
ATVs
Golf carts,
Minibikes and
Specialty Carts
(>3 hp)
Snowmobiles
General
(>25 hp)
General
(<25 hp)
Lawn & Gard.,
Commercial,
Logging,
Airport
Support
(<25 hp)
Rec. Marine—
Outboards
Rec Marine—
Sterndrive/
Inboards
Rec Marine—
PWC
Emission Factor Data Sources Used
for:
NEVES
A?
A
na
D
D
C
F
G
na
ARE
A
B
na
C,E
B
B
F
G*
na
Small
Engine
Model
na
C
na
na
C
C
na
na
na
Nonroad
Draft
Version
A
C
A
D
C
C
F
G
na
Notes
It is not clear where
NEVES PM estimates
are from, but we will
use them for draft.
Operating at lower
RPM, these are more
like lawnmowers than
motorcycles.
A few exist. We will
use motorcycle
factors.
See Table 1 in the
main report.
No 4-strokes in
baseline years
Additional
Data
Sources
1
2-5
6-15
6-15
16
17-18
* There may be a typographic error in ARB's emission factor for 4-stroke inboards.
nr-OlOb.wpd
All
-------
Table A5-Emission Factors Data Sources Listed in Table A4 for Four-stroke Gasoline Engines
Reference
Code
A
B
C
Number
of
Engines.
Tested
?
"more
than 500"
29
including
7
9
4
6
O
Age, design
and
Application
of Engines
?
?
"1 1
side-valve
OHV
side-valve
OHV
side-valve
Horse-
power
of
engine
?
?
3.5-5
i
hp
4-5 hp
8-12 hp
11-12.5
hp
16-18
hp
Testing
lab
?
man.
SwRI
Emissions
measured
HC, CO,
NOX
HC, CO,
NOX
HC, CO,
NOX (PM
andFC
for 6
engines)
Citation and notes
ARB Mailout #90-58, "Proposal to control emissions from
Off-Road Motorcycles," September?, 1990. (For NEVES,
converted to g/hr based on an average speed of 25 mph).
Documentation of Input Factors for the New Off-Road Mobile
Source Emissions Inventory Model, Energy and
Environmental Analysis, Inc., for California Air Resources
Board, February, 1997. Appendix A.
Technical Support Document for California Exhaust Emission
Standards and Test Procedures for 1994 and Subsequent
Model-Year Utility and Lawn and Garden Equipment Engines.
(ARB TSD) California Air Resources Board. Attachment C
to ARB Mailout #90-64. December 1990. p. 31. Six of these
engines are reported in SAE 910560, which lists PM and FC.
(Note that both NEVES and the Small Engine model use this
data, but the emission factors are different because the
calculations use different groupings. The Draft version of
NONROAD will start with the emission factors from the small
engine model, but will combine them into NONROAD
categories using the sales fractions for OHV and Side Valve
engines listed for "All Other Equipment" in Table B3 of
Appendix B.)
nr-OlOb.wpd
A12
-------
D
C
F
G
4
2
O
3
?
?
outboard
engines
sterndrive/
inboard
engines
30-85
53.5
and?
10-45
hp
120-
200 hp
SwRI
?
NMM
A
NMM
A
HC, CO,
NOX, PM,
FC
HC, CO,
NOX
HC, CO,
NOX,
BSFC
HC, CO,
NOX,
BSFC
Hare, C.T and KJ. Springer. Exhaust Emission from
Uncontrolled Vehicles and Related Equipment Using Internal
Combustion Engines, Final Report, Part 5, Heavy Duty Farm,
Construction and Agricultural Engines. San Antonio TX:
Southwest Research Institute, October 1973. (SwRI provided
differently-weighted averages for various applications,
creating a large number of emission factors from a few data
points.)
Cited in Regulatory Strategies for Off-Highway Equipment."
EEA for ARE, August 1992.
NEVES Table I- lib
NEVES Table I-llc
nr-OlOb.wpd
A13
-------
Table A6—Known Additional Data Sources Listed in Table A4 for Four-Stroke Gasoline Engines
Reference
Code
1
2
3
4
5
Number
of
Engines.
Tested
1
3
2
2
5
(planned)
Age, design
and
Application
of Engines
OHV golf cart
lift-trucks
utility engines
various
applications
Horse-
power
of
engine
8.4 hp
106,
107,
109hp
41.4,
85 hp
60,
lOOhp
37-
205 hp
Testing
lab
SwRI
SwRI
SwRI
SwRI
SwRI
Emissions
measured
HC, CO,
NOX, PM,
BSFC
HC, NOX
HC, CO,
NOX, PM,
CO2, FC
HC, CO,
NOX, PM,
BSFC
HC, CO,
NOX,
BSFC
Citation and notes
White, Jeff J. et al. "Baseline and Controlled Exhaust
Emissions from Off-Highway Vehicle Engines," SAE 931541
(SwRI/ARB), December 1993.
Carroll, J.N. "Emission Tests of a 4.9 Liter Ford Utility
Engine in Twelve Configurations", SwRI for Geometric
Results, April 1994.
Carroll, James N. and J. J. White. "Final Letter Report
"Emission Tests of Three Lift- Truck Engines". SwRI 08-53L
to William Montweiler, Industrial Truck Association.
February 10, 1993.
White, Jeff J. et al. "Baseline and Controlled Exhaust
Emissions from Off-Highway Vehicle Engines," SAE 931541
(SwRI/ARB) December, 1993.
White, Jeff J. et al. "Three-Way Catalyst Technology for Off-
Road Equipment Powered by Gasoline and LPG Engines,
Interim Report" SwRI 8778 for CA ARE, December 1997.
nr-OlOb.wpd
A14
-------
6
7
8
9
10
11
3
8
including
6
2
45
1
1
O
side-valve
WBMs, 1-10
years old*
1-16 year-old
lawnmowers*
utility engine
riding mower
2
lawnmowers,
1 utility
engine
3.5-5
hp
1-5 hp
8-12.5
hp
3-5 hp
8hp
7
4.5, 5,
11 hp
EPA
UM
Ctr. for
Em.
Res.
Anal.
SwRI
7
SwRI
HC, CO,
NOX,
CO2, other
toxics and
HC
fractions
HC, CO,
C02, NOX
HC, CO,
NOX, C02
HC, CO,
NOX,
CO2, FC
CO, HC+
NOX
HC, CO,
NOX,
CO2, FC
Gabele, Peter. "Emissions from 4-Cycle Walk-Behind-Mower
Engines: Test Cycle Effects. SAE 972793.
Sun, X., et al. "Emissions Analysis of Small Utility Engines"
SAE paper 952080. Data on same engines reported in "Small
Engine Emissions" in Off Highway Engineering, Dec. 1995.
Assessment of In-Use Emissions of Gasoline Engine Powered
Lawnmowers, Final Report" The Center for Emissions
Research and Analysis, Project #92-002 for EPA, etc., March
17, 1995
Burrahm, Robert W., Jeff J. White and James N. Carroll.
"Small Utility Engine Emissions Reduction Using Automotive
Technology." SAE paper 91 1805 in Two Stroke Engines,
Small Engines and Emissions Reductions, SAE SP-883. Table
3.
Swanson, Mark. "An Emission Comparison Between a
Carburetor and an Electronic Fuel Injection System for Utility
Engines." SAE paper 911806 in SAE SP-883. Table 2.
White, Jeff J. et al. "Emission Control Strategies for Small
Utility Engines," SAE paper 91 1807 in SAE SP-883. Table 7,
9,10.
nr-OlOb.wpd
A15
-------
12
13
14
15
16
17
18
4
?
1
1
1
4
1
7
7*
OHV WBM
OHV
outboard
marine engine
inboard
marine
engines
sterndrive
marine engine
3.5,4,
12.5,
18 hp
7
3.5hp
(435
cc)
8hp
7
7
SwRI
Onan
SwRI
SwRI
EPA
EPA
Mich.
Auto.
Res.
Corp.
HC, CO,
NOX, PM
NMHC,
CO, NOX,
PM
7
HC, CO,
NOX, FC
HC, CO,
NOX, FC
HC, CO,
NOX, FC
Hare, C.T., and Karl Springer. "Exhaust Emissions from
Uncontrolled Vehicles and Related Equipment Using Internal
Combustion Engines, Final Report, Part 4, Small Air-Cooled
Spark Ignition Utility Engines." May 1973.
Fax from Onan Corporation: "OPEI In-Use Emissions
Testing." Docket A-93-25/H-D-46.
Hare, C.T., and JJ. White. "Toward the Environmentally-
Friendly Small Engine: Fuel, Lubricant, and Emission
Measurement Issues," 1991. SAE911222.
Energy and Environmental Analysis, Inc. "Regulatory
Strategies for Off-Highway Equipment," August, 1992.
"Memorandum: Exhaust Emission Testing of a Two-Stroke
and a Four-Stroke Marine Engine; Results and Procedures,"
Mike Samulski to Docket #A-92-28, May 30, 1996.
"Memorandum: Effects of Transience on Emissions from
Inboard Marine Engines," from Michael Samulski, to Docket
#A-92-28. May 30, 1996. (Note: includes data from
Samulski, M., "Sensitivity of Test Cycle and Fuel Type on a
Spark-Ignition Four-Stroke Inboard Marine Engine," 1994.
SAE 941782.)
"A Comparison of Exhaust Emissions on a Marine Engine
Run on Steady State and Simulated Transient Cycles,"
Michigan Automotive Research Corporation for National
Marine Manufacturers Association, October 8, 1992.
*In-use data listed for reference only. EPA does not plan to include this data when calculating emission factors for new engines.
nr-OlOb.wpd
A16
-------
Other Spark Ignition Engines
Table A7-Data Sources for Baseline Emission Factors for CNG/LPG engines
Equipment
Description
All CNG/LPG
Equipment
Emission Factor Data Sources
Used for:
NEVES
A,B
ARE
C,D
Nonroad Draft
Version
A,B
Notes
NEVES created emission factors by multiplying the
relevant gasoline factor by an adjustment factor. The
draft version of NONROAD will use the NEVE emission
factor.
Additional Data
Sources
1-5
nr-OlOb.wpd
A17
-------
Table A8-Emission Factors Data Sources Listed in Table A7 for Natural Gas/LPG Engines
Reference
Code
A
B
C
D
Number
of
Engines
Tested
1
1
?
1
Age, design
and
Application
of Engines
?
utility engine
Horse-
power
of
engine
?
?(400
cc)
Testing
lab
SwRI
Onan
man.
Walbro
Emissions
measured
HC, CO,
NOX, PM
HC, CO,
NOX
HC, CO,
NOX
HC, CO,
NOX,
BSFC
Citation and notes
JJ. White, et. al. "Emission Factors for Small Utility
Engines," 1991. SAE 910560
Williamson, Dale E. Onan Corporation. Letter to California
Air Resources Board, July 20, 1990.
Documentation of Input Factors for the New Off-Road Mobile
Source Emissions Inventory Model, Energy and
Environmental Analysis, Inc., for California Air Resources
Board, February, 1997. Appendix A.
"A Study of the Potential of Propane Fuel to Reduce Utility
Engine Exhaust Emissions," Kenneth J. Cotton, Walbro
Engine Management Corp. SAE 921696, September, 1992.
nr-OlOb.wpd
A18
-------
Table A9—Known Additional Data Sources Listed in Table A7 for Natural Gas/LPG Engines
Reference
Code
1
2
3
4
5
Number
of
Engines
Tested
2
1
1
1
4
(planned)
Age, design
and
Application
of Engines
lift truck,
utility engine
2s trimmer
4s side-valve
lift truck
various
Horse-
power
of
engine
40,60
hp
?
85 hp
102hp
37-53
hp
Testing
lab
SwRI
SwRI
SwRI
SwRI
SwRI
Emissions
measured
HC, CO,
NOX, PM,
BSFC
HC, CO,
BSFC
HC, CO,
NOX,
C02,
BSFC
HC, NOX
HC, NOX,
CO,
BSFC
Citation and notes
White, Jeff J. et al. "Baseline and Controlled Exhaust
Emissions from Off-Highway Vehicle Engines," SAE 931541
(SwRI/ARB 1993) December 1993. (Note, while ARE
sponsored these tests, they chose not to use the data because
the engines were tested at very lean calibrations.)
J.P. Latusek and R.W. Burrahm, "Conversion of Two Small
Utility Engines to LPG Fuel," 1993, SAE 932447.
Carroll, James N. and J. J. White. "Final Letter Report:
Emission Tests of Three Lift- Truck Engines". SwRI 08-53L
to William Montweiler, Industrial Truck Association.
February 10, 1993.
Carroll, J.N. "Emission Tests of a 4.9 Liter Ford Utility
Engine in Twelve Configurations", SwRI for Geometric
Results, April 1994.
White, Jeff J. et al. "Three-Way Catalyst Technology for Off-
Road Equipment Powered by Gasoline and LPG Engines,
Interim Report" SwRI 8778 for ARE, December 1997.
nr-OlOb.wpd
A19
-------
Appendix B
Cross-Inventory Comparison of SI Emission Factors
The body of Appendix B is the large Microsoft Excel™ spreadsheet compare.xls. This
document explains how the spreadsheet was created and explains how to use the spreadsheet,
which compares emission factors from NEVES, OFF-ROAD, EPA's Small Engine Model and
the draft version of NONROAD.
To make it possible to compare emission factors for specific equipment types, the rows in
the spreadsheet compare.xls are a list of every combination of Source Classification Code (SCC)
and horsepower group for spark ignition engines. The rows include SCCs (including 2266xxxxx
and airport service equipment) that are not used in NONROAD but are used by California Air
Resources Board (ARB). The columns in the spreadsheet are emission factors from NEVES,
from ARB's draft OFF ROAD model, and from the Small Engine model. These are followed by
some notes on differences between the factors and by a list of the emission factors used in the
Draft version of NONROAD. Various subsets of the spreadsheet's columns can be selected by
choosing"View Manager"™ in Excel's "View" menu.
Comparing emission factors between inventory models is not straightforward because the
different models and inventories use different units and different categories in distinguishing
emission factors. To compare the factors, all factors were converted to list emission factors in
g/hp-hr by engine type, application and horsepower. This conversion required mapping both the
ARB horsepower groups and the Small Engine Model's displacement classes to the horsepower
groups used by the NONROAD model (see Tables B-l and B-2). It was also necessary to
combine the Small Engine Model's overhead-valve and side-valve categories into a single
category by using a sales-weighted average, using the sales mix listed in Table B-3.
Note that the BSFC column labeled as NEVES BSFC is not directly from NEVES, but is
based on NEVES information. Also note that the input files for NONROAD will have fewer
entries because, without the need to compare across models and inventories, emission factors
will be grouped by global SCCs and larger horsepower ranges.
Bl
-------
Table Bl —Mapping of small engine groupings used in the Small Engine Model and ARB's OFF-
ROAD model to the small engine groupings used in the NONROAD model
Small Engine Model
Class/Displacement
Non-Handheld, I
<225 cc
Non-Handheld, H
>225 cc
Handheld, IE
0-20 cc
Handheld, IV
20-50 cc
Handheld, V
>50cc
ARE Power
Range
2-5 hp
5-15 hp
15-25hp
<2hp
<2hp
2-15 hp
NONROAD
Power Range
3-6 hp
6-16 hp
16-25 hp
0-1 hp
1-3 hp
3-6 hp
NONROAD
source classification
All engines except 2-stroke
trimmers/edgers/cutters, chainsaws,
leafblowers, and snowblowers
All engines except 2-stroke
trimmers/edgers/cutters, chainsaws,
leafblowers, and snowblowers
All engines
All engines
All 2-stroke trimmers/edgers/cutters,
chainsaws, leafblowers, and
snowblowers
Table B2-- Mapping of large engine groupings used in ARB's OFF-ROAD model to the large
engine groupings used in the NONROAD model.
ARB hp range
5-15
15-25
25-50
50-120
120-175
175-250
250-500
500-750
750-9999
NONROAD hp Range
6-11 & 11-16
16-25
25-50
50-100
100-175
175-250
250-500
500-750
750-3000+
B2
-------
Table B3—Sales Mix for Small Engine Model, Pre-control [1]
Application
Lawn Mowers
Trimmers/
Edgers/ Cutters
Chain Saws
Leaf Blowers/
Vacuums
Generator Sets
Tillers
Snowblowers
Commercial
Turf Equipment
Rear Engine
Riding Mowers
Lawn & Garden
Tractors
Pumps
All Other
EauiDment
Sales Mix
2-stroke handheld
Class 3
0.0501
0.0035
0.0528
Class 4
0.9173
0.6426
0.6299
0.0101
Class 5
0.0077
0.3539
0.2086
0
0.3205
2-stroke non-
handheld
Class 1
0.1
0.0017
0.0099
0.0974
Class 2
0.0024
4-stroke non-handheld,
overhead- and side- valve
Class 1
OHV
0.065
0.0016
0.0007
0.0057
0.04
0.0222
0.0375
Class 1
SV
0.835
0.0231
0.0721
0.2853
0.7938
0.3732
0.0647
0.0499
0.804
0.0049
0.4064
Class 2
OHV
0.0001
0.0551
0.0001
0.3658
0.1563
0.0013
0.1421
0.0081
Class 2
SV
0.0014
0.0002
0.0359
0.6522
0.196
0.3063
0.5196
0.7939
0.1725
0.8531
0.4482
[l]"Documentation of the OMS Small Gasoline Engine Spreadsheet System, Final Technical Memorandum" TRC Environmental
Corporation for U.S. EPA Air and Energy Research Laboratory. August 1995.
B3
-------
Appendix C
Technology Groups
NONROAD accounts for changes in sales fractions and emissions from the advent of
emission standards or other changes by assigning technology groups to each Source
Classification Code (SCC). Each technology group has its own emission factor and the fraction
of the population assigned to each group can change over time. These "technology fractions" are
contained in an input file in NONROAD called tech.dat. A sample record for 4-stroke
lawnmowers might show a shift in engine sales from side-valve engines (Tech Group 1) to
overhead valve engines (Tech Group 2) as illustrated in Table Cl, which shows side-valve
engines declining from 90% of sales in 1991 to 50% of sales in 1997.
Table Cl: Sample Technology Fractions
SCC/Year
2260004010
1990
1997
Horsepower
Range
3-6 hp
Tech
group/fraction
1
0.90
0.50
Tech
group/fraction
2
0.10
0.50
Each technology group has an associated emission factor given in the emission factor
input file for that pollutant. This emission factor can change with time. For example, CO
emissions from Technology Group 1 (side-valve engines) might decrease from 819 g/hp-hr for
model year engines 1990 through 1996 to 387 g/hp-hr for model years 1997 and later as shown in
Table C2. The year listed in the emission factor input file is the first year in which the new
emission factor applies.
Table C2: Sample Emission Factors
SCC/Year
2265004010
1990
2265004010
1997
Horsepower
Range
3-6 hp
3-6 hp
Technology
group/emissions
1
819
1
387
Units
g/hp-hr
g/hp-hr
Pollutant
CO
CO
For pre-controlled engines the only technology groups currently identified are those used
to combine SCCs for spark-ignition engines <25 hp as described in NR-006. Technology groups
primarily will be used for engines subject to emissions regulations. The regulations discussed in
the main body of this report are expected to influence the sales fraction of various technology
Cl
-------
types and the emission rates of those technologies. These anticipated changes are described in
EPA's rulemakings and set forth in the spreadsheets Techl.wk4, Techmix.wk4, and Appendix F
of the small engine Phase II regulatory support document. The emission factors for Phase I and
Phase II engines are listed as "new engine exhaust" values in Table F-07. The expected sales
mixes for Phase I and Phase II as listed in Tables F-03 and F-04 of the RSD appendix. [1] For
both the draft and final versions of NONROAD, EPA will simply format this information for the
NONROAD input files.
If new emission factors are developed for other parts of the inventory (e.g., larger SI
engines) to reflect distinctions between different engine technologies with different emission
levels, then appropriate technology groups, technology fractions, and emission factors will be
added to the model. Similarly, appropriate emission factors will be added to the model if new
emission standards are implemented.
References
[1] "Regulatory Support Document, Phase 2: Emission Standards for New Nonroad Spark
Ignition Engines At or Below 19 Kilowatts". U.S. EPA, Office of Air and Radiation, December
1997.
C2
------- |