APTD-1496
APRIL 1974
EXHAUST EMISSIONS
FROM UNCONTROLLED
VEHICLES
AND RELATED EQUIPMENT
USING INTERNAL
COMBUSTION ENGINES:
•\
PART 7 - SNOWMOBILES
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
Ann Arbor, Michigan 48105
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APTD-1496
EXHAUST EMISSIONS
FROM UNCONTROLLED
VEHICLES
AND RELATED EQUIPMENT
USING INTERNAL
COMBUSTION ENGINES:
PART 7 - SNOWMOBILES
by
Charles T . Hare and Karl J . Springer
Southwest Research Institute
San Antonio, Texas
Contract No. EHS 70-108
EPA Project Officer: William Rogers Oliver
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control Programs
Emission Control Technology Division
Ann Arbor, Michigan 48105
April 1974
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - as supplies permit - from the Air
Pollution Technical Information Center, Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; or, for a fee, from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Southwest ^Research Institute, in fulfillment of Contract No. EHS 70-108.
The contents of this report are reproduced herein as received from
Southwest Research Institute. The opinions, findings, and conclusions
expressed are those of the author and not necessarily those of the Environmen-
tal Protection Agency. Mention of company or product names is not to
be considered as an endorsement by the Environmental Protection Agency.
Publication No. APTD-1496
11
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ABSTRACT
This report is Part 7 of the Final Report, on "Exhaust Emissions
from Uncontrolled Vehicles and Related Equipment Using Internal Com-
bustion Engines, " Contract EHS 70-108. Exhaust emissions from four
snowmobile engines were measured using steady-state "mapping" pro-
cedures, employing 29 combinations of speed and load for each engine.
The engines tested were an Arctic 440, a Polaris 335, a Rotax 248, and
an OMC 528 rotary. The first three engines listed are all 2-stroke vert-
ical twins with blower cooling, and the last engine is a blower- (and charge-)
cooled rotary combustion (Wankel) engine.
The procedures used for operation of snowmobile engines included
idling and a variety of engine loads at four to six crankshaft speeds, de-
pending on the engine. The gaseous exhaust constituents measured on a
continuous basis during all the test modes included total hydrocarbons
by FIA; CO, CO2, NO, and HC by NDIR; NO and NOX by chemiluminescence;
and O2 by electrochemical analysis. Gaseous constituents measured during
some modes on a bag sample or grab sample basis included light hydro-
carbons by gas chromatograph>and formaldehyde (HCHO) and total aliphatic
aldehydes (RCHO) by wet chemistry. Exhaust smoke was measured using
a PHS full-flow smokemeter, and exhaust particulate was measured using an
experimental dilution-type particulate sampler. The smoke and particulate
measurements were acquired only at a limited number of conditions se-
lected from the 29 speed/load combinations used for gaseous emissions
testing.
The engines were operated on a special test stand, utilizing a
small water-brake dynamometer and inlet air controlled to a nominal
20° F. The emissions results are used in conjunction with available data
on snov/mobile population and usage to estimate national emissions impact.
Ill
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FOREWORD
The project for which this report constitutes part of the end
product was initiated jointly--on June 29, 1970 by the Division of Motor
Vehicle Research and Development and the Division of Air Quality and
Emission Data, both divisions of the agency known as NAPCA. Cur-
rently, these offices are the Emission Characterization and Control
Development Branch of MSAPC and the National Air Data Branch of
OAQPS, respectively, Office of Air and Water Programs, Environ-
mental Protection Agency. The contract number is EHS 70-108, and
the project is identified within Southwest Research Institute as 11-2869-001.
This report (Part 7) covers the snowmobile portion of the char-
acterization work only, and the other items in the characterization work
have been covered by six other parts of the final report. In the order in
which the final reports have been submitted, the seven parts of the char-
acterization work include: Locomotives and Marine Counterparts; Out-
board Motors; Motorcycles; Small Utility Engines; Farm, Construction
and Industrial Engines; Gas Turbine "peaking" Powerplants; and Snow-
mobiles. Other efforts which have been conducted as separate phases
of Contract EHS 70-108 include: measurement of gaseous emissions from
a number of aircraft turbine engines, measurements of crankcase drainage
from a number of outboard motors, and investigation of emissions control
technology for locomotive diesel engines; and those phases either have
been or will be reported separately.
Cognizant technical personnel for the Environmental Protection
Agency are currently Messrs. William Rogers Oliver and David S. Kircher;
and past Project Officers include Messrs. J. L. Raney, A. J. Hoffman,
B. D. McNutt, and G. J. Kennedy. Project Manager for Southwest Re-
search Institute has been Mr. Karl J Springer, and Mr. Charles T. Hare
has carried the technical responsibility.
The offices of the sponsoring agency (EPA) are located at 2565
Plymouth Road, Ann Arbor, Michigan 48105 and at Research Triangle
Park, North Carolina 27711; and the contractor (SwRI) is located at
8500 Culebra Road, San Antonio, Texas 78284.
The assistance of several groups and individuals has contributed
to the success of the snowmobile portion of this project, and it should be
acknowledged. Appreciation is first expressed to the International Snow-
mobile Industry Association (ISIA), in particular to Mr. John F. Nesbitt,
who supplied population, sales, and usage data gathered by ISIA from
its member companies. Thanks are also expressed to Sally Wimer,
editor of Invitation to Snowmobiling magazine for her interest in the
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snowmobile studies and her assistance over a period of two years or
more, and to Snow Goer Trade magazine for back issues containing
material of interest to this study. Appreciation is also expressed to the
corporations which supplied engines for testing and to technical personnel
at these companies who gave invaluable assistance, namely: Arctic
Enterprises, Inc. , and Messrs. Wayne Konickson and Ron Solberg;
Bombardier, Ltd., M. Zoel Bergeron; Outboard Marine Corporation,
and Messrs. Mike Griffith and George Miller; and Polaris Industries,
Mr. Les Foster. Mr. Lowell Haas of Scorpion, Inc. also assisted with
comments on test procedures and technical details.
The SwRI personnel who performed most of the preparation and
test work included: Russel T. Mack, lead technician; William P. Jack,
Paul Fowler, Ernest Krueger and Nathan Reeh, technicians; and Joyce
Winfield, laboratory assistant. The contributions of all these people
are sincerely appreciated.
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TABLE OF CONTENTS
ABSTRACT '
FOREWORD v
LIST OF FIGURES Vii
LIST OF TABLES x
1. INTRODUCTION 1
II. OBJECTIVES 2
III. TEST DOCUMENTATION, INSTRUMENTATION, PRO-
CEDURES, AND CALCULATIONS 3
A. Engine Specifications and Descriptions 3
B. Test Documentation and Equipment 3
C. Emissions Test Procedures 10
D. Calculations and Unmeasured Emissions 12
IV. EMISSION TEST RESULTS 16
A. Aldehyde and Light Hydrocarbon Concentrations 16
B. Major Gaseous Emissions Results 18
C. Particulate and Smoke Results 31
V. ESTIMATION OF EMISSION ^ACTORS AND NATIONAL
IMPACT 37
A. Development of Emission Factors 37
B. Estimation of National Impact 48
VI. SUMMARY 54
LIST OF REFERENCES 56
APPENDIX
VII
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LIST OF FIGURES
Figure Page
1 Arctic Cat 440 Engine on Test Stand 5
2 Polaris 335 Engine on Test Stand 5
3 Bombardier (Rotax) Z48 Engine
(Photo Supplied by Bombardier) 5
4 OMC 528 Rotary Engine on Test Stand 5
5 Details of Exhaust System Used on OMC 528
Rotary Engine 7
6 Details of Plastic Intake Duct Used on Polaris
335 Engine (Typical of Those Used on All Four
Engines) 7
7 Details of Intake Air Cooling System 7
8 Overall View of Equipment and Personnel During
a Test 7
9 Details of Fuel Scale, Water Traps, FIA De-
tector Unit, and Dynamometer Readouts 9
10 Typical Setup for Particulate Sampling 9
11 Details of Experimental Particulate Sampler 9
12 Details of PHS Smokemeter 9
13 Hydrocarbon Emissions from Four Snowmobile
Engines as Functions of Load, With Engine Speed
as Parameter - Data from Tables 5, 7, 8, and 9 27
14 Carbon Monoxide Emissions from Four Snow-
mobile Engines as Functions of Load, With Engine
Speed as Parameter - Data from Tables 5, 7,
8, and 9 28
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LIST OF FIGURES (Cont'd)
Figure Page
15 Oxides of Nitrogen Emissions from Four Snow-
mobile Engines as Functions of Load, With Engine
Speed as Parameter - Data from Tables 5, 7, 8,
and 9 29
16 Total Aliphatic Aldehyde (RCHO) Emissions from
Four Snowmobile Engines as Functions of Load
With Engine Speed as Parameter - Data from
Tables 5, 7, 8, and 9 30
17 Particulate Emissions from Four Snowmobile
Engines as Functions of Load, With Engine Speed
as Parameter - Data from Tables 5, 7, 8, and 9 33
18 8% Opacity Smoke from a Snowmobile Engine 36
19 14% Opacity Smoke from a Snowmobile Engine 36
20 2% Opacity Smoke from a Snowmobile Engine 36
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LIST OF TABLES
Table Page
1 Specifications of Test Engines Compared to Ap-
proximate Industry Ranges for the 1972-1973
Model Year 4
2 Engine Speed and Load Conditions Used for Emis-
sions Tests 11
3 Summary of Average Aldehyde Concentrations
from Four Snowmobile Engines 17
4 Concentrations of Light Hydrocarbons in the Ex-
haust of Four Snowmobile Engines 19
5 Average Fuel Rates, Mass Emissions, and Brake
Specific Emissions for an Arctic Cat 440 Snow-
mobile Engine 21
6 Average Fuel Rates, Mass Emissions, and Brake
Specific Emissions for an Arctic Cal 440 Snow-
mobile Engine with Rich High-Speed Jet Setting 22
7 Average Fuel Rates, Mass Emissions, and Brake
Specific Emissions for a Polaris 335 Snowmobile
Engine 23
8 Average Fuel Rates, Mass Emissions, and Brake
Specific Emissions for a Rotax 248 Snowmobile
Engine 24
9 Avera,ge Fuel Rates, Mass Emissions, and Brake
Specific Emissions for an OMC 528 Rotary Snow-
mobile Engine 25
10 Particulate Concentration Data on Four Snow-
mobile Engines 32
11 Summary of Average Smoke Opacity from 2~
Stroke Snowmobile Engines, Based on 2-Inch
Diameter Outlet 35
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LIST OF TABLES (Cont'd)
Table Page
12 Dynamometer Operating Cycles Used by Two
Manufacturers 37
13 Estimates of Average Owner Usage from Massey-
Ferguson 38
14 Field Usage Data Developed by John Deere 39
15 Regrouped and Modified Field Usage Data 40
16 Time-Based Weighting Factors for Snowmobile
Engine Emissions Results 41
17 Cycle Composite Mass and Specific Emissions
for Four Snowmobile Engines 43
18 Variation in Major Emissions and. Fuel Con-
sumption with Operating Cycle Load Factor 45
19 Description of Snowmobiles Owned ana Operating
Data Obtained from a Survey of Magazine Subscribers 47
20 Emissions, Fuel Consumption, and Power Output
of 2-Stroke Snowmobile Engines Divided by Engine
Displacement 49
21 Estimated Snowmobile Emission Factors (As-,
suming 362 cm3 Displacement) ^9
22 Estimates of Annual Operating Time from Massey-
Ferguson 50
23 Distribution of Registrations for the 1972-1973
Season 51
24 Estimated National Emissions Impact of Snow-
mobiles 52
25 Comparison of Snowmobile Emission Estimates
with EPA Nationwide Air Pollutant Inventory Data 52
26 Summary of Estimated Seasonal and Regional Varia-
tion in Snowmobile Emissions 53
XI
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I. INTRODUCTION
The program of research on which this report is based was
initiated by the Environmental Protection Agency to (1) characterize
emissions from a broad range of internal combustion engines in order
to accurately set priorities for future control, as required and (2) assist
in developing more inclusive national and regional air pollution inventories.
This document, which is Part 7 of a seven-part final report, concerns
emissions from snowmobiles and the national impact of these emissions.
Prior to the subject \vork, virtually no useful information on
snowmobile emissions had been published. Although a great many
papers were available on emissions from 2-stroke engines, they were
concerned with either engine modifications to reduce emissions or with
engines of sizes and types other than those commonly used in snow-
mobiles. The procedures used to acquire emissions data for this report
were chosen with the intent of gathering the most useful results, but little
consideration has been given to the potential usefulness of these procedures
for anything except research purposes. All the subject tests were per-
formed in the SwRI Emissions Research Laboratory between March 19
and July 31, 1973.
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II. OBJECTIVES
The objectives of the snowmobile part of this project were to
obtain exhaust emissions data on a variety of engines and to use these
data in conjunction with available information on a number of snow-
mobiles in service and their annual usage to estimate emission factors
and national impact. The emissions to be measured included total
hydrocarbons by FIA; CO, CO , NO, and HC by NDIR; O^ by electro-
chemical analysis; light hydrocarbons by gas chromatograph; aldehydes
by wet chemistry; particulates by gravimetric analysis; and smoke by
the PHS light-extinction smokemeter. These exhaust constituents are
essentially the same as those measured during all tests on gasoline-
fueled engines tested under this contract.
The objectives included implicitly the development of test pro-
cedures suitable for obtaining emissions data on snowmobile engines
and the development or modification of calculation techniques for emis-
sion factors and national impact. It was also necessary to simulate the
snowmobile's operating environment to some extent, and to this end a
system was constructed to provide air to the carburetor at a nominal
20° F and at normal atmospheric pressure.
2
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III. TEST DOCUMENTATION, INSTRUMENTATION,
PROCEDURES, AND CALCULATIONS
This report section includes descriptions and photographs of
the test engines, descriptions and photographs of the test equipment
and instrumentation used, and explanations of the test sequences and
calculation methods employed. Briefly, four engines were tested using
a small water-brake dynamometer and state-of-the-art emissions
measuring equipment; and the engines were supplied with intake air
at or near 20° F to help simulate field operation. Three of the engines
were 2-stroke twins, representative of the majority of newer engines
in service, and the fourth was a rotary (Wankel) engine which was chosen
due to mechanical novelty and anticipation of future engine trends. The
testing procedures used included three modes at idle plus 28 other speed/
load conditions which were intended to span the operating range of the
engines. These 28 conditions were not uniform from engine to engine
due to different rpm ranges and power bandwidths.
A. Engine Specifications and Descriptions
To show the extent to which the engines tested were representative
of those currently being offered, Table 1 has been prepared to show the
major specifications of the test engines as compared to approximate in-
dustry ranges for the 1972-1973 models. It appears that the test engines
generally fell in the center of the pov/er plants available according to
most design criteria, which was one of the main objectives of choosing
these engines. The exception to this rale is the OMC rotary, which was
included in the test program primarily to assess possible future changes
in snowmobile emissions rather than to help determine current national
impact. In terms of the results of a snowmobile ownership survey (1972-
1973 season)'"1''\ the three brands in most, widespread use were Ski-Doo
(Bombardier), Arctic Cat, and Polaris, represented by the three reci-
procating engines tested. The 2-stroke engine has become almost the
universal snowmobile powerplant (until the advent of the rotaries) due
to its relatively high pov/er/weight and power/size ratios, low cost.
minimum number of moving parts, and extremely good cold weather
starting capability.
B. Test Documentation and Equipment
Photographs of the test engines begin with Figure 1, which shows
the Arctic Cat 440 engine (manufactured by Kawasaki) mounted on a
-•' Superscript numbers in parentheses refer to the List of References
at the end of this report.
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TABLE 1. SPECIFICATIONS OF TEST ENGINES COMPARED TO
APPROXIMATE INDUSTRY RANGES* FOR THE 197Z-1973 MODEL YEAR
Specification
Displacement, cm
Cylinders
Rated Power, hp
Rated rpm
Induction
Cooling
Compression Ratio
Rated hp/ liter
Artie
440
436
2
32
7000
piston port
Air -Axial
Blower
6.8
73
Polaris
Star 335
335
2
25
6500
piston port
Air-Radial
Blower
6.7
77
Bombardier
(Rotax) 248
247
2
16
6000
piston port
Air- Axial
Blower
6.7
65
OMC 528
Rotary
528
(1 rotor)
35
6000
(d)
Air -Radial
Blower^'
8.5
66
Industry
Range
225-560
1-3
12-58 (b>
5500-8000(C>
(e)
Air, Liquid,
and Charge
6.5-6.8(g)
49-ll6(n)
* Do not include mini-snowmobiles or over-the-counter
racers--see notes b, c, and g
(a) Not from manufacturer's data
(b) Conventional engines only- -mini- snowmobiles down to
3 hp, racers up to 124 hp
(c) Conventional engines only- -mini- snowmobiles down to
3600 rpm, racers up to 9500 rpm
(d) Side and Peripheral ports
(e) Piston port, reed valve, and rotary valve for 2-strokes
(f) Plus charge cooling of rotor
(g) Z-stroke engines only
(h) Conventional engines only-- mini-snowmobiles down to
18, liquid-cooled up to 114, racers up to 190
stand constructed especially for these tests. The stand was made of
steel channel and angle, with a great deal of reinforcement; and the
engines were mounted on a 1/2-inch steel plate which was attached to
the stand proper using resilient mounts. In some cases, the severity
of vibration created by the engines required that the mounting plate be
damped by sections of angle bolted to it and the main frame.
The power absorption unit of the Stuska 90 hp water-brake dyna-
mometer is partially visible behind the engine in Figure 1. This photo
also shows a typical adaptation to the stock exhaust system made for
test purposes with the (stock) short cylindrical section exiting the muf-
fler at a right angle and immediately "dumping" into a 4-inch diameter
duct. The general approach taken was to allow the exhaust to enter as
large a duct as possible as it came out its normal opening, and to allow
the intake air to be drawn into its normal entrance (either the carburetor(s),
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FIGURE 1. ARCTIC CAT 440 ENGINE
ON TEST STAND
FIGURE 2. POLARIS 335 ENGINE
ON TEST STAND
FIGURE 3. BOMBARDIER (ROTAX)
248 ENGINE
(PHOTO SUPPLIED BY BOMBARDIER)
FIGURE 4. OMC 528 ROTARY
ENGINE ON TEST STAND
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silencer, or filter) from as large a volume as possible at atmospheric
pressure. The exhaust systems permitted pressures at the normal
exhaust outlet within 0. 1 inch Hg above atmospheric pressure.
Figure 2 shows the Polaris 335 engine, and the scale used to
determine fuel mass flow rate appears in the foreground. Fuel for all
the engines was equivalent to Federal emission test gasoline , plus
the recommended amount of lubricant as specified by each engine manu-
facturer. The fuel was drawn from a 5-gallon container on one side of
the scale, and balance weights were added to the other side to bring the
imbalance within the 0-2 ]bf range of the scale (readout in 0. 01 Ibf in-
crements). Fuel times were taken with a stopwatch while the engines
consumed a predetermined amount of fuel, the amount varying according
to rate of consumption to keep the time measurements to reasonable
lengths.
Figure 3 shows the Bombardier (Rotax) 248 engine (this photo
was supplied by Bombardier), and Figure 4 shows the OMC 528 rotary.
Note in Figure 4 that the stock air inlet grille is mounted in a flat surface
and that a Tedlar* plastic enclosure is used to duct intake air from the
cooling chamber to the grille. These flexible plastic ducts, having a
relatively large volume and no solid boundaries when the inlet air was at
atmospheric pressure, were used to prevent unwanted pulsations at the
intake point. The insulating panel shown beside the engine in Figure 4
can be located more precisely by referring to Figure 5, which shows it
to be located between the engine and muffler to prevent radiant transfer
of heat from muffler to engine. The square duct at the foreground in
Figure 5 is the outlet of a high-volume blower used to cool the muffler
on this engine, since the engine produces extremely high-temperature
exhaust gases.
Figure 6 shows more detail of the plastic intake duct used on the
Polaris 335 engine, which is also similar to those used on the others.
Some detail of the intake air cooling system is shown in Figure 7, with
the barrel on the left containing a naphtha-type liquid in -which were im-
mersed chunks of dry ice to keep its temperature down to about -75° C.
This cold liquid was pumped through three concentric coils of 1/2-inch
diameter copper tubing mounted in the other barrel, totalling about 250
feet in length. Room air at about 75° F was supplied to the second barrel
(at right in Figure 7) by the blower in the foreground, and it circulated
over the coils through a system of baffles. Pressure at the engine air
inlet \vas monitored by the water manometer mounted on the right-hand
barrel and was controlled to within 0. 1 inch H^O above atmospheric
pressure by restricting the make up blower inlet and adjustment of the
counterweighted waste-gate on the top of the right-hand barrel.
Registered trademark of E. I. duPont De Nemours & Company
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FIGURE 5. DETAILS OF EXHAUST
SYSTEM USED ON OMC 528
ROTARY ENGINE
FIGURE 6. DETAILS OF PLASTIC
INTAKE DUCT USED ON POLARIS
335 ENGINE (TYPICAL OF THOSE
USED ON ALL FOUR ENGINES)
FIGURE 7. DETAILS OF INTAKE
AIR COOLING SYSTEM
FIGURE 8. OVERALL VIEW OF
EQUIPMENT AND PERSONNEL
DURING A TEST
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Samples of exhaust for continuous analysis as well as batch
samples were withdrawn from the fabricated, large-diameter exhaust
pipe at a point from 2 to 3 feet downstream of the original muffler out-
let. The sample taps are shown quite clearly in Figure 2 along with a
thermocouple inserted nearer the muffler outlet, and they also appear
at the extreme left of Figure 8. Figure 8 shows the test layout quite
well, including the sampling cart operator (right), the engine operator,
and another technician to take fuel time measurements. Continuous
exhaust samples were piped to the main gaseous emissions cart via
an overhead sample line, but the samples for the FIA hydrocarbon ana-
lyzer and for aldehyde analysis were taken through a short, heated line
right next to the exhaust pipe. The proximity of the FIA analyzer's
detector unit (the box-shaped unit in the right background) to the exhaust
line can be seen in Figure 9, and the glass bubblers on the side of the
oven away from the engine were the ones used to collect samples for
aldehyde analysis. Figure 9 also shows the fuel scale in more detail,
as well as the row of ice-bath water traps (in front of the FIA) used to
dry the samples going to all the analyses except those for aldehydes and
hydrocarbons by FIA, The gauges on the wall in the background of Fig-
ure 9 are a tachometer and a load indicator for the dynamometer.
The continuous exhaust samples were analyzed for total hydro-
carbons by FIA (at l60°F) and for (mostly paraffinic) hydrocarbons by
NDIR, They were also analyzed for CO, CO2, and NO by NDIR; for NO
and NOX by chemiluminescence; and for O? by an electrochemical analyzer.
Samples taken by bubbling exhaust through reagents for a specific time
interval were analyzed for formaldehyde (HCHO) by the chromotropic acid
method^3) and for total aliphatic aldehydes (RCHO) by the MBTH method(4).
Bag samples were used for light hydrocarbon analysis (methane through
butane, total of seven compounds). The chromatograph employed a 10
foot by 1/8 inch column packed with a mixture of phenyl isocyanate and
Porasil C, preceded by a 1 inch by 1/8 inch pre-column packed with 100-
120 mesh Porapak N.
In addition to the gaseous emissions, particulates and smoke emit-
ted by the snowmobile engines -were also studied. Figure 10 shows the
system used to deliver exhaust gases to the particulate sampler for the
Polaris engine, which was typical of the systems used for the other engines
also. For particulate and smoke measurements, the exhaust pipes were
necked down to a 2-inch diameter at a point several feet downstream of
the standard muffler outlet. This change from the system used for gaseous
emissions sampling had a negligible effect on exhaust backpressure, and it
was necessary to provide exhaust gases in the correct range of velocities
for the particulate sampler. The sampler operated by diluting and cooling
a small stream of raw exhaust with clean air, filtering the mixture, and
providing flow measurements so that particulate concentrations could be
calculated. The sampler was experimental and was developed under this
contract for research purposes only. The 2-inch diameter outlet for smoke
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FIGURE °. DETAILS OF FUEL SCALE,
WATER TRAPS, EIA DETECTOR UNIT,
AXD DYNAMOMETER READOUTS
FIGURE 10. TYPICAL SETUP FOR
PARTICU LATE SAMPLING
FIGURE 11. DETAILS OF EXPERI-
MENTAL PARTICULATE SAMPLER
FIGURE 12, DETAILS OF PHS
SMOKE METER
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measurements was also thought to be more representative of "real"
exhaust appearance than something larger would have been, and it was
desired to make the diameter uniform for all the engines to permit
meaningful comparisons. The optimum situation, of course, would be
to measure smoke at the standard muffler outlet; but this approach (let-
ting the exhaust out into the test area) was impractical due to safety con-
siderations. The smoke measurements were taken outside on a Z-inch
diameter pipe protruding through the wall to circumvent the safety problem.
Details of the experimental particulate sampler are shown in Figure 11,
and a PHS smokemeter(^) of the type used is shown in Figure 12.
C. Emissions Test Procedures
It was initially planned to operate each of the engines at idle,
plus (seven loads x 4 speeds) in a uniform "map" of conditions. This
procedure was used substantially intact for testing the Arctic Cat 440
(the first engine tested), but it was revised to include more speeds and
fewer loads at some of the speeds (to keep the total number of test modes
constant) as understanding of snowmobile operation matured. A sum-
mary of the actual speed/load conditions used for gaseous emissions
sampling is given in Table 2, with the conditions used for light hydro-
carbon and aldehyde sampling indicated; those used for particulate
sampling indicated, and those used for smoke measurements also indicated.
Time simply did not permit a greater number of modes to oe used for
tests other than gaseous emissions sampling. It should be noted also
that smoke data were acquired under several conditions not used for gas-
eous emissions tests, namely 3000 rpm/full load for the Rotax and 2500
rpm/full load and 2500 rpm/1/2 load for the Polaris.
Time requirement in each mode of these procedures was dic-
tated by a combination of sampling time (for batch samples), time for
the engine to consume a predetermined amount of fuel, and stability of
emission levels (for constituents measured on a continuous basis). The
samples for aldehyde and light hydrocarbon analysis were acquired con-
currently with the continuous gaseous emissions tests, but both the part-
iculate and the smoke tests required individual runs.
All the test conditions were steady-state, and no attempt was
made to obtain numerical data during transient conditions. Observation
of the continuous recorder charts, however, indicated that excursions
of gaseous emission levels during transients were not so pronounced as
to cause marked changes in overall emissions from the snowmobile en-
gines tested. It was noted, however, that a full-throttle acceleration
against load after a prolonged idle sometimes produced a rather noticeable
smoke puff lasting from a few seconds to perhaps 30 seconds. The du-
ration and intensity of the puff seemed to vary directly with amount of
time spent at idle prior to the acceleration and with oil concentration in
the fuel. An example of the appearance of such a smoke puff will be given
in a later section of the report.
10
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TABLE 2. ENGINE SPEED AND LOAD CONDITIONS USED FOR EMISSIONS TESTS
Arctic Cat 440
Condition
Mode
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
rpm
Idle
5500
5500
5500
5500
5500
5500
5500
2500
2500
2500
2500
2500
2500
2500
Idle
4000
4000
4000
4000
4000
4000
4000
7000
7000
7000
7000
7000
7000
7000
Idle
Load
0
0
1/8
1/4
1/2
3/4
7/8
full
full
7/8
3/4
1/2
1/4
1/8
0
0
full
7/8
3/4
1/2
1/4
1/8
0
0
1/8
1/4
1/2
3/4
7/8
full
0
Notes
1,
1,
1,
1
1
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1
1
1,
1,
2,3
3
3
2,3
2,3
3
2,3
2,3
2,3
3
2, 3
3
3
2, 3
2,3
Polaris
335
Rotax 248
Condition
rpm
Idle
4500
4500
4500
4500
4500
2500
2500
2500
5500
5500
5500
5500
5500
5500
Idle
7000
7000
7000
3500
3500
3500
3500
3500
3500
6500
6500
6500
6500
6500
Idle
Load
0
0
1/4
1/2
3/4
100
1/4
1/8
0
0
1/4
1/2
3/4
7/8
full
0
full
7/8
3/4
0
1/8
1/4
1/2
3/4
full
full
7/8
3/4
1/2
0
0
Notes
1,
1,
1,
1,
1,
1,
1,
1,
3
1,
1
1,
1,
1
1
1
1
1
2,
2,
3
1,
2,3
3
2
3
2
3
2
2,3
3
3
2, 3
3
3
2,3
Condition
rpm
Idle
4000
4000
4000
4000
4000
4000
4000
3000
3000
3000
3000
3000
6500
6500
Idle
6500
6500
6500
6500
5000
5000
5000
5000
5000
5000
2500
2500
2500
2500
Idle
Load
0
0
1/8
1/4
1/2
3/4
7/8
full
3/4
1/2
1/4
1/8
0
0
1/4
0
1/2
3/4
7/8
full
full
7/8
3/4
1/2
1/4
0
0
1/8
1/4
1/2
0
Notes
1, 2, 3
1
1,2,3
1
3
1,3
1,2
1,3
1,2,3
3
1
1, 2, 3
1,2,3
1, 2
1,3
3
1, 2, 3
1
3
1,2,3
OMC 528 Rotary
Condition
rpm
Idle
3500
3500
3500
3500
3500
3500
2500
2500
2500
6000
6000
6000
6000
6000
Idle
6000
4000
4000
4000
4000
4000
4000
5000
5000
5000
5000
5000
5000
5000
Idle
Load
0
0
1/8
1/4
1/2
3/4
full
1/2*
1 / 4*
0
0
1/4
1/2
3/4
7/8
0
full
full
7/8
3/4
1/4
1/8
0
0
1/8
1/4
1/2
3/4
7/8
full
0
Notes
1,
1,
1,
1
1,
1,
1,
1,
1
1
1
1,
1
1,
2
2
2
2
2
2
2
2
2
Note: All conditions used for gaseous emissions measurements
1. Condition used for light HC and aldehyde measurements
2. Condition used for particulate measurements
3. Condition used for smoke measurements
* These loads were estimated because the engine was not to be run at
full load under 3500 rpm
11
-------
Engine operating data and other data acquired daring the tests
included intake and exhaust pressures, intake air and exhaust gas temp-
eratures, and spark plug seat and/or other critical engine temperatures,
in addition to ambient conditions and other data already discussed. Com-
plete raw data from all the continuous gaseous emissions tests are included
in the Appendix; and the data from the aldehyde, light hydrocarbon, part-
iculate, and smoke evaluations will be presented in Section IV of the text.
All the data presented in concentrations (in both text and appendix) will
be expressed on a "wet" basis, that is, as measured at the exhaust outlet
before removal of water vapor from the sample, or as corrected back to
those conditions mathematically.
Lubrication of the test engines was a very important considera-
tion, since they were all lubricated by oil mixed with the fuel. The re-
commended practice of the manufacturers was followed in all cases ex-
cept one, that being the Rotax, which was run for gaseous emissions
measurements at Z0:l gasoline:oil ratio instead of 50:1 as recommended.
This measure was followed to ensure reliability, in light of (1) pro-
blems with other engines when run oil-lean, (2) a possible time lag in
obtaining parts from Canada should something go wrong, and (3) the
assumption that oil concentration should have relatively little to do with
hydrocarbon concentrations. The Rotax was run at both 20:1 and 50:1
for smoke and particulate evaluations, and the particular oil used was
a TCW-qualified Chrysler oil. Bombardier's recommendation read,
"we recommend our ski-doo oil at 50/1 ratio--any good snowmobile
two cycle oil could be used. "
The Arctic Cat 440 was run at 20: 1 using Arctic's "Modified
Purple Powerlube" oil. The Polaris 335 was initially run at 40:1 but
was switched to 20:1 after encountering a piston seizure. Particulate
and smoke measurements were made at both 20: 1 and 40:1, ratios,
and the particular oil used was a TCW-qualified oil marketed by Evin-
rude. The OMC rotary was run at 50:1 using a special OMC rotary
engine oil marketed only for that purpose.
D. Calculations and Unmeasured Emissions
In converting emission measurements to mass rates, the first
step usually taken is conversion of concentrations measured "dry" to
a "wet" basis. One of the complicating factors in this mathematical
process is the presence of water vapor in the intake air; but in the case
of the snowmobile engine tests, this problem was effectively eliminated
by the intake air cooling system. It is safe to assume that the intake air,
cooled to about 20°F, was saturated with water vapor. The saturation
value, however^ would be so low as to be negligible; and thus the intake
air can be assumed as dry air fox calculation purposes at the temperatures
12
-------
listed in the Appendix tables for each mode. All the concentration data
appearing in this report are on a wet basis, as already mentioned.
To avoid placing air flow measurement devices upstream of the
engine air intakes and thereby running the risk of upsetting air flow and
engine performance, it was decided to measure fuel flow rates and com-
pute mass emissions using a fuel-based procedure. The following def-
initions and equations were used to make the concentration-to-mass flow
conversion on a mode -by-mode basis:
F = fuel rate, Ib/hr
ill *
TC = total carbon = % CO + % CO2 + (ppmC x 10'4)
HC(g/hr) = 0.0454(ppmC) (F/TC)
C0(g/hr) = 916. (%CO) (F/TC)
NO (g/hr) = 0.150(ppmNO ) (F/TC) as NO? (ppm NOy by
.X X LJ •"•
chemilumlnescence)
RCHO(g/hr) - 0. 0982(ppm RCHO) (F/TC) as HCHO
Particulate(g/hr) = 2. 79(Particulate mg/SCF) (F/TC)
The only major assumption made in forming these equations was that
fuel composition approximated (CHj §5) , for which many good precedents
exist(^). Note also that total aliphatic aldehydes (RCHO) are expressed
"as HCHO" to fix an assumed molecular weight per carbonyl group. All
the NOX mass rates and brake specific rates in this report, as well as
NO and NO concentrations, are on a wet basis but not "corrected" to a
X —
standard ambient humidity by one of several equations available for the
purpose'"' 7). The reasons that NO is not being "corrected" here are
that (1) no work has been done to establish an applicable relationship of
NOX to humidity for either the 2-stroke SI engine or the rotary and (Z)
the standard ambient humidity used in existing equations (75 grains H-.O/
lbm dry air) is far from correct for normal snowmobile operation. It
should also be noted that the NOX mass and brake specific rates are based
on NO concentrations measured by the chemiluminescent instrument.
Although a number of important exhaust constituents were meas-
ured during the snowmobile engine tests, a few measurements of less
important emissions were neglected due either to time and financial
constraints or the lack of a reliable analysis method. Using these
criteria, it was decided to estimate emissions of sulfur oxides (SO r),
A.
evaporative hydrocarbons, and crankcase (blowby) hydrocarbons rather
than attempt to measure them.
Beginning with evaporative hydrocarbons and crankcase hydro-
carbons, they will both be neglected but for different reasons. In the
case of evaporation, it is recognized that winter fuel Rvp's (Reid vapor
pressures) are high enough to permit evaporation under some conditions,
13
-------
but it is felt that the generally low temperatures under which snowmobiles
are operated and stored will make evaporation negligible. Regarding
crankcase losses, the Z-stroke engines use crankcase induction; so they
produce no crankcase losses. The rotary engine tested has no oil sump
either, nor does it have other design features which would permit unburned
fuel-air mixture to escape into the atmosphere; so none of the snowmobile
engines tested produce any losses of fuel-air mixture past combustion
chamber seals to the atmosphere. Although it has not been possible to
check on all the engine models currently being produced, it seems doubtful
that any of them produce blowby losses; and the zero-loss situation will
be assumed for the purposes of this report.
In the case of SOX, instrumentation for the measurement of this
pollutant in raw exhaust has not been developed to the same extent as that
for other common constituents; so it has become more or less accepted
practice to calculate sulfur oxide emissions based on fuel sulfur content.
In a 4-stroke gasoline engine or a diesel in which substantially all the fuel
is burned (perhaps 99 percent or more), the assumption is usually made
that all the sulfur in the fuel oxidizes to SC>2. This assumption leads to
computation of an SCK mass emission rate which is 2.00 times the rate
at which sulfur enters the engine in the fuel (2.00 = molecular weight of
SO^/a-tomic weight of S). For snowmobile engines, however, a fairly
significant fraction of the fuel is emitted without being burned at all (from
2 to 4 percent for the Wankel tested to 24 to 35 percent for the 2-stroke
engines based on cycle composites) which means that roughly the same
fraction of fuel sulfur is being emitted without being oxidized. Emissions
of sulfur oxides, then, are computed for snowmobile engines in the same
way as for other engines, except that the final result is multiplied by the
fraction of fuel burned before being reported as SC>2.
Prior to estimation of emission factors and national impact, emis-
sions will be computed on a cycle composite basis by assuming that each
mode listed in Table 2 occupied some fraction of total snowmobile operating
time (the fractions can be zero, of course). In terms of definitions and
equations:
Mi = individual mode emissions, g/hr
Fi - individual mode fuel consumption, lbm/hr
hpi = individual mode power, hp
W^ = individual time-based mode weighting factor
i = mode number (1 to 31)
31
cycle composite g/hr = J M-W.
14
-------
31
^^
^t
i=l
31
cycle composite g/hp-hr =
If it appeared desirable for some reason, fuel specific emissions could
also be computed by the relation:
31
y M.W.
i=l * *
cycle composite g/lbm fuel - -r-j -
F.W.
The desirability of performing this calculation might arise if, for example,
it were determined that reliable data on total fuel consumption by snow-
mobiles did exist. The weighting factors to be used in computing cycle
composite emissions -will be developed in a later report section (V), based
on the best data available from manufacturers, snowmobile publications,
and the International Snowmobile Industry Association (ISIA).
15
-------
IV. EMISSION TEST RESULTS
This section includes concentration data on aldehydes, light
hydrocarbons, particulate, and smoke; and it also includes mass and
brake specific emission rates for HC, CO, NOX, RCHO (aldehydes),
particulate, and SOX. These rates are presented on a mode-by-mode
basis, and cycle composites will be given in a later section of the report.
Concentration data for the gaseous emissions measured continuously
are presented in the Appendix (all concentrations on a wet basis).
A. Aldehyde and Light Hydrocarbon Concentrations
Aldehydes were generally measured during two or three runs
and only at those conditions which were considered most important in
each engine's operation. Variation in mode choices also occurred due
to inability of some engines to maintain operating temperatures below
specified maximum limits for the required sampling period. The number
of test modes was restricted because there is a long analysis time in-
volved with each sample, and the importance of aldehyde emissions is
not so great as to justify time and efforts which might compromise some
other part of the test program. The intended numbers of aldehyde measure
ments were acquired for all the engines except the OMC rotary, which
encountered operating difficulties beyond the contractor's maintenance
abilities and had to be removed from the test program prematurely.
Concentrations of formaldehyde (HCHO) and total aliphatic alde-
hydes (RCHO) are given in Table 3, and the most noticeable features of
these data (for 2-strokes) are their relatively high concentrations and
their relatively small total variation (range of RCHO from 106 to 531 ppm,
or about 5-to-l) as compared with other emissions. Although four data
points cannot be considered even strongly indicative, let alone conclusive,
it appears that aldehyde concentrations from the rotary engine might be
substantially lower than those from the 2-stroke reciprocating engines.
The aldehyde concentrations from the snowmobile engines are in the same
general range as those measured for other 2-stroke engines (such as
motorcycles^ ' and small utility engines^ '') under the subject contract.
They are generally quite a bit higher, however, than those measured
during this project for either 4-stroke gasoline engines^. 9, 11) or diesel
Light hydrocarbons were measured during most of the same modes
as aldehydes, and this measurement was made using bag samples of ex-
haust which could be analyzed by gas chromatograph as time permitted.
Depending on sample composition, time required to analyze one bag of
16
-------
TABLE 3. SUMMARY OF AVERAGE* ALDEHYDE CONCENTRATIONS
FROM FOUR SNOWMOBILE ENGINES
Condition
Arctic Cat 440 Data
rpm
1560
Load HCHO, ppm
Idle
2500 0
2500 1/2
2500 full
4000 0
4000 1/2
4000 full
5500 0
5500 1/2
7000 0
7000 1/4
Condition
104
103
121
166
59
148
239
60
100
47
100
RCHO, ppm
209
186
221
246
158
205
531
160
187
116
160
Rotax 248 Data
rpm Load HCHO, ppm
1850 Idle
2500
2500
3000
3000
4000
4000
4000
5000
5000
5000
6500
6500
0
1/4
1/4
1/2
1/4
1/2
3/4
1/2
3/4
full
3/4
full
83
140
80
74
140
70
69
117
141
110
161
140
148
RCHO, ppm
106
208
158
141
186
153
155
175
185
172
177
181
165
Condition
rpm Load
1010 Idle
2500 0
2500 1/4
3500 0
3500 1/4
3500 1/2
4500 0
4500 1/4
4500 1/2
4500 3/4
4500 full
5500 1/2
5500 3/4
5500 full
7000 3/4
7000 full
Condition
rpm Load
2500 0
2500 1/4^
3500 1/4
3500 1/2
Polaris
HCHO, ppm
158
93
94
160
199
141
156
278
260
156
142
177
151
125
335 Data
RCHO, ppm
189
197
174
188
245
266
281
407
400
328
367
423
261
283
OMC 528 Rotary Data(a)
HCHO, ppm
29
19
14
17
RCHO, ppm
47
47
20
24
* Two runs in most cases
(a.) Tests aborted due to engine
problems one run only
(b) Estimated
17
-------
exhaust ranged up to one hour, pointing up the need to keep the total
number of samples to a minimum. Light hydrocarbons are of interest
primarily because concentrations of combustion products (hydrocarbons
not normally present in the fuel) are indicative of processes occurring
within the engine. Table 4 gives the data obtained on snowmobile engines,
generally showing a rather complex mixture of combustion products. The
propane concentrations were uniformly low, because there is little propane
in the fuel and because it does not occur often as a combustion product.
Butane concentrations were more variable and were probably quite pro-
portional to total hydrocarbon concentrations. Butane evaporates rapidly,
even at room temperatures, so some of the butane variation is possibly
due to evaporation during the hours over which the tests were conducted.
On the basis of average concentrations in ppm C for the 2-stroke
engines, the alkenes (C2H^. and C^H^) and unburned fuel (C^H,, and C^H, Q)
were roughly equal; and these two categories made up over 80 percent of
the light hydrocarbons. The remainder -was mostly alkanes (CH^ and
CzH-fa) with a small fraction of acetylene (C^H-,). The few samples taken
on the OMC rotary indicate a very small fraction of unburned fuel and
roughly 50 percent alkenes, 30 percent alkanes, and ZO percent acetylene.
The total ppm C in light hydrocarbons for the 2-strokes averaged about
3300, with about 2000 ppm C of this amount in combustion products. The
light hydrocarbons totalled an average of about 2300 ppm C for the OMC
rotary, virtually all of which was combustion products.
B. Major Gaseous Emissions Results
As already mentioned in the introduction to Section IV, data on
concentrations of major gaseous emissions (those measured by continuous
techniques) are given in the Appendix. The data given here in the text
are in mass rates and brake specific rates and could easily'be computed
on a fuel specific basis if it were shown to be desirable by available
statistics.
Average mass and specific emissions are given in Tables 5 through
9 on a mode-by-mode basis. Tables 5, 7, 8, and 9 present data for reg-
ular tests on the Arctic, Polaris, Rotax, and OMC engines, respectively.
Table 6 shows information gathered on the Arctic engine using a richer
high-speed jet setting, a modification recommended for field usage where
operating temperatures are difficult to hold down. These tables contain
a great many individual items of information which are difficult to inter-
pret, so the data will also be presented in other ways. These presenta-
tions will include calculation of composite emissions in a later report
section, as well as graphical presentation in this section as functions of
engine load with engine speed as parameter.
-------
TABLE 4. CONCENTRATIONS OF LIGHT HYDROCARBONS IN THE
EXHAUST OF FOUR SNOWMOBILE ENGINES
Arctic Cat 440
Condition
rpm
1560
2500
2500
2500
4000
4000
4000
5500
5500
5500
7000
7000
7000
7000
Load
Idle
0
1/2
full
0
1/2
full
0
1/2
full
0
1/4
1/2
full
CH4
1610
98
65
342
114
189
258
204
159
225
49
209
246
367
C2Hfr
148
32
32
0
35
89
82
18
19
64
7
33
51
61
Condition
rpm
1010
2500
2500
3500
3500
4500
4500
4500
4500
5500
5500
5500
7000
Load
Idle
0
1/4
1/4
1/2
0
1/4
1/2
3/4
1/2
3/4
full
full
CH4
384
621
246
456
235
439
611
326
325
406
611
366
268
C2H6
176
44
29
258
131
179
230
123
93
34
154
51
55
Concentrations
C?H4
971
149
143
0
168
341
400
116
176
302
85
210
222
737
Polaris
C H
16
0
0
0
0
0
0
0
0
0
0
0
0
0
335
Concentrations
C2H4
301
268
183
275
428
779
895
573
537
191
681
298
223
C3H8
0
0
0
17
0
0
12
0
4
4
0
0
7
in ppm
C?H?
1300
0
0
0
11
0
0
137
32
0
0
53
0
0
in ppm
CzH2
55
722
101
137
23
225
151
27
63
193
169
146
231
C-^Hf,
974
419
343
0
706
0
0
25
257
407
0
51
432
910
C3Hfe
26
0
281
213
340
549
0
539
526
415
488
408
75
C4H| n
877
0
0
0
0
438
444
400
0
0
0
448
0
0
(~* T T
43
513
393
1900
0
592
654
202
310
206
339
206
61
(continued)
19
-------
TABLE 4 (Cont'd). CONCENTRATIONS OF LIGHT HYDROCARBONS IN
THE EXHAUST OF FOUR SNOWMOBILE ENGINES
Rotax 248
Condition
rpm
1850
2500
2500
300Q
3000
4000
4000
4000
5000
5000
5000
6500
6500
Load
Idle
0
1/4
1/4
1/2
1/4
1/2
3/4
1/2
3/4
full
3/4
full
CH4
113
106
63
86
111
119
219
127
191
201
153
398
351
C2Hfe
54
53
39
59
56
84
41
78
145
151
128
239
224
OMC
Condition
rpm
2500
2500
3500
3500
Load
0
1/4W
1/4
1/2
CH4
1280
563
552
352
C2H6 <
104
39
48
41
Concentrations
C2H,
241
232
194
250
280
351
223
359
528
556
504
811
80?.
528
^ C3Hg
31
37
31
29
24
29
30
27
31
31
39
26
28
Rotary(a>
Concentrations
C2H,
680
301
386
271
1 C3H8
0
3
0
0
in ppm
CZH2
77
69
43
56
67
64
81
39
54
52
39
118
102
in ppm
C2H2
946
220
208
133
C?H^
104
110
95
80
80
74
74
70
65
66
89
57
59
C3Hfe
288
175
141
106
C4H10
533
546
487
460
444
494
410
498
574
575
607
753
750
f~" T-T
15
3
17
0
(a) Tests aborted due to engine problems one run only
(b) Estimated
20
-------
TABLE 5.
AVERAGE FUEL RATES , MASS EMISSIONS, AND BRAKE SPECIFIC EMISSIONS
FOR AN ARCTIC CAT 440 SNOWMOBILE ENGINE
Condition
Fuel,
rpm
1560
2500
2500
2500
2500
2500
2500
2500
4000
4000
4000
4000
4000
4000
4000
5500
5500
5500
5500
5500
5500
5500
7000
7000
7000
7000
7000
7000
7000
Load
Idle
0
1/8
1/4
1/2
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
Ibrn/hr
1.56
1.77
1.95
2.27
3.32
4.71
6.96
6.34
2.32
2. 70
3. 07
5.65
8.71
9.66
10.3
3.06
3.34
4.84
8.40
15.7
17.3
20.7
3.56
5.73
8.43
15.3
20. 0
26. 0
23.3
Mass Emissions in g/hr
HC
347.
243.
262
A47
903.
419.
0 C 1
1230.
1 "3 1
ley.
2170.
9'7in
CO
373.
388.
230
?^A
7 1 "^
? i n
60.7
93.0
c i n
1120.
•at L
1A fl
c -a A
^47n
NOV RCHO Part.l*'
0.18 1.8 10.4
0.27 1.9 19.3
035
0 70
•3 f,Q C 7
174
7 C 1
80.1 10. 66.9
0.90 2.6 15.7
1 4A _._
7 QO 7 f,
?R Q
92. 7 35. 65.2
177 1 ft
c c q
CO f.
7fl^ 1 1 O
qcn ._ .
147 _____ ......
i z.A 1 47
sojb>
0. 16
0. 24
0 27
0 32
n 44
0 64
n ftQ
0.85
0.27
0 38
0 48
o 90
1 •a 7
1.48
0 54
n c: Q
0 83
1 1 7
237
7 4ft
? PI
062
0 Q7
1 14
2 27
2 Q7
3 65
3. 37
Specific Emissions in g/hp-hr
HC
276.
146.
128.
111.
166.
122.
183.
87.
63.
79.
81.
86.
41.
38.
83.
75.
79.
91.
86.
86.
99.
88.
119.
87.
9
3
4
8
3
8
5
2
2
5
5
2
3
3
6
3
CO
242.
135.
5.73
36.3
304.
8.21
23.4
11.9
67.7
213.
153.
78.2
6.24
5.47
239.
157.
183.
117.
37.8
211.
292.
172.
257.
110.
NC
0.
0.
0.
2.
0.
10.
0.
0.
1.
0.
1.
6.
0.
1.
1.
2.
2.
7.
2.
1.
0.
2.
1.
4.
)x RCHO Part.la'
37
37
99 1.5
14
55
8 1.4 9.05
76
57
05 1.0
80
97
48 2.5 4.56
43
01
25 0.66
61
03
22 3.93
33
08 1.0
86
09
46
92 4.69
SOj
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
^
.28
.17
.12
. 11
.14
. 11
. 20
. 15
. 12
. 12
. 11
. 10
.16
. 12
.08
. 11
.09
.10
. 24
.16
. 14
. 12
. 13
. 11
(a) These particulate data are for a 20:1 gasoline:oil ratio
(b) Calculated
-------
TABLE 6. AVERAGE FUEL RATES, MASS EMISSIONS, AND BRAKE SPECIFIC EMISSIONS
FOR AN ARCTIC CAT 440 SNOWMOBILE ENGINE WITH RICH HIGH-SPEED JET SETTING
Condition
rprn
1580
2500
2500
2500
2500
2500
2500
2500
4000
4000
4000
4000
4000
4000
4000
5500
5500
5500
5500
5500
5500
5500
7000
7000
7000
7000
7000
7000
7000
Load
Idle
0
1/8
1/4
1/2
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
Fuel,
lbm/hr
1.51
1. 70
3.82
7.50
2.12
6.61
13.5
3.01
12.6
18.2
22.1
23.8
3.52
15.9
21.8
27.7
25.7
Mass Emissions in g/hr
HC
323.
288.
485.
1190.
373.
546.
1710.
124.
1150.
2040.
2760.
2980.
180.
1680.
2610.
3860.
3440.
CO
336.
293.
23.1
1370.
54.3
1330.
2510.
28.1
4330.
6160.
7490.
5310.
25.8
5180.
6290.
9840.
5900.
NOX RCHO
0.
0.
4.
14.
1.
7.
38.
1.
11.
22.
27.
77.
1.
12.
26.
17.
78.
1 ^
4
i ^
7
Q
0
Q
7g
£
Q
7
Part. SO.
0
_ - - . _ o
1
1
- - - - 0
1
2
-a
3
------ 0
------ 3
•a
3
y(a)
16
21
54
95
25
05
90
54
96
67
12
36
61
38
13
74
53
HC
126.
159.
71.3
106.
79.7
94.6
109.
107.
1/8.
109.
142.
114.
Specific Emissions in g/hp-hr
CO NOX RCHO Part.
6.01 1.08
182. 1.91
174. 0.97
156. 2.41
300. 0.81
286. 1.06
295. 1.06
190. 2.79
334. 0.78
262. 1.11 ---
363. 0.66
196. 2.61
so^a)
0. 14
0.13
0. 14
0.12
0. 14
0. 12
0.12
0.12
0. 15
0. 13
0, 14
0.12
(a) Calculated
-------
TABLE 7. AVERAGE FUEL RATES, MASS EMISSIONS, AND BRAKE SPECIFIC EMISSIONS
FOR A POLARIS 335 SNOWMOBILE ENGINE
Condition
rpm
1010
2500
2500
2500
3500
3500
3500
3500
3500
3500
4500
4500
4500
4500
4500
5500
5500
5500
5500
5500
5500
6500
6500
6500
6500
6500
7000
7000
7000
Load
Idle
0
1/8
1/4
0
1/8
1/4
1/2
3/4
full
0
1/4
1/2
3/4
full
0
1/4
1/2
3/4
7/8
full
0
1/2
3/4
7/8
full
3/4
7/8
full
Fuel,
lbm/hr
1.11
2.00
2.29
2.45
2.67
3.10
3.57
4.65
6.25
13.8
3.09
4.73
7.34
11.5
16.7
3.84
7.06
10.3
13.7
17.6
21.6
3.79
11.5
15.7
16. 8
22.2
15.9
19.6
23. 9
Mass Emissions in g/hr
HC
237.
436.
401.
348.
546.
535.
464.
480.
751.
2440.
507.
366.
657.
1410.
2820.
567.
484.
879.
1730.
2750.
3630.
306.
996.
1670.
1900.
3200.
1740.
2440.
3160.
CO
216.
483.
618.
541.
650.
673.
672.
559.
908.
4580.
604.
609.
1500.
2740.
5030.
844.
1340.
2430.
3020.
3600.
6730.
1080.
2640.
4150.
3060.
6050.
3690.
4250.
7150.
NO
0.
0.
0.
2.
0.
0.
1.
5.
16.
27.
0.
4.
12.
33.
25.
4.
7.
16.
47.
70.
37.
4.
16.
36.
83.
47.
32.
69.
43.
v RCHO
16 1.2
32 2.1
44 2.7
58 2.9
25 8.3
82 5.4
29 9.6
3 20.
5 29.
0 30.
gf,
9 26.
2 40.
6
4 28.
8 39.
Part.
0.
1.
0.
0.
0.
2.
2.
0.
1.
2.
1.
1.
1.
2.
3.
1.
1.
1.
3.
1.
1.
2.
1.
54
64
64
65
99
10
45
96
30
33
40
41
44
78
58
73
29
99
75
89
67
88
66
1.
1.
2.
2.
2.
1.
2.
2.
1.
1.
7
5.31
6
2 1.98
2
0 1.34
7
3
4
1.50
2.71
4
5
0. 34
0. 21
0.32
0. 20
0.13
0. 11
0. 14
0. 17
0.12
0. 11
0. 11
0.21
0. 14
0.11
0. 11
0.12
0. 14
0, 13
0. 11
0.12
0. 12
0. 11
0.13
(a) These particulate values are for a 40:1 gaeoline:oil ratio
(b) Calculated
-------
TABLE 8. AVERAGE FUEL RATES, MASS EMISSIONS, AND BRAKE SPECIFIC EMISSIONS
FOR A ROTAX 248 SNOWMOBILE ENGINE
Condition
rpm
1850
2500
2500
2500
2500
3000
3000
3000
3000
3000
4000
4000
4000
4000
4000
4000
4000
5000
5000
5000
5000
5000
5000
6500
6500
6500
6500
6500
6500
Load
Idle
0
1/8
1/4
1/2
0
1/8
1/4
1/2
3/4
0
1/8
1/4
1/2
3/4
7/8
full
0
1/4
1/2
3/4
7/8
full
0
1/4
1/2
3/4
7/8
full
Fuel,
lbm/hr
0.98
1.13
1.45
1.61
1.86
1.57
1.72
1.87
2.67
3.13
2.13
2.71
2.89
4.39
5.10
6.00
7.30
2.48
4.10
5.31
7.07
8.28
9.56
2.17
5.52
9.29
12.0
12.7
13.2
Mass Emissions in a/hr
HC
223.
253.
299.
309.
305.
327.
334.
349.
467.
555.
430.
456.
446.
725.
862.
1070.
1400.
434.
574.
797.
1100.
1380.
1760.
145.
741.
1360.
1830.
2050.
2200.
CO
25.4
21.2
33.1
32.7
30.5
52.0
48.5
52.5
444.
152.
74.8
217.
155.
487.
232.
263.
145.
94.4
390.
86.2
299.
368.
288.
40.8
44.3
263.
452.
556.
333.
NOX RCHO
0.14 0.77
0.19 1.8
0 24
0.30 1.9
0 56
Q 25
0.47 2.0
1.20 3.1
Q 33
1.20 3.2
2.24 4.9
9.52 6.6
1 ft ^
0 86
7 RCi _ _.
8.94 7.8
22.2 8.9
52.4 12.
1 1 H
662 - - -
213
56.9 16.
73 3
92.2 17.
Part. (*) SOx(b)
0.96 0.095
1,25 0.11
- -- - 0 1 ^
- - - 0 23
017
3.97 0.21
032
- --. 0^7
------ 0 23
13.2 0.54
----- 062
0 30
- n R ^
069
25.2 0.91
in?
28.9 1.11
O -a A
160
30.2 1.63
HC
906.
507.
218.
1110.
465.
265.
271.
490.
284.
214.
158.
166.
191.
204.
145.
140.
146.
166.
168.
157.
143.
143.
135.
Specific Emissions in g/hp-hr
CO
100.
53.6
21.8
162.
70.0
252.
74.1
233.
98.7
144.
42.6
40.7
19.8
138.
15.7
38.1
38.9
27.2
100.
30.3
35.3
38.6
20.6
NOX
0. 73
0.49
0.40
1.07
0.63
0.68
1.50
0. 76
0. 76
0.66
1.75
2.86
5.40
1.01
1.63
2.83
4.12
4.94
1.50
2.45
4.45
5.44
5.69
RCHO Part.(a)
3.2
2.6 5.30
1.8
2.0
1.4 3.89
1.2
1.4
1.1 3.22
1.2 2.73
1.2
1.0 1.86
0.47
0. 30
0. 17
0.64
0. 29
0. 18
0. 18
0. 36
0. 24
0. 16
0.11
0. 11
0. 11
0. 20
0. 13
0.12
0. 11
0. 10
0. 17
0. 14
0.12
0. 11
0. 10
(a) These particulate values are for a 50:1 gasoline:oil ratio
(b) Calculated
-------
TABLE 9. AVERAGE FUEL RATES, MASS EMISSIONS, AND BRAKE SPECIFIC EMISSIONS
FOR AN OMC 528 ROTARY SNOWMOBILE ENGINE
Condition
rpm
1370
2500
2500
2500
3500
3500
3500
3500
3500
3500
4000
4000
4000
4000
4000
4000
5000
5000
5000
5000
5000
5000
5000
6000
6000
6000
6000
6000
6000
Load
Idle
0
1/44
0
1/8
1/4
1/2
3/4
full
0
1/8
1/4
3/4
7/8
full
0
1/8
1/4
1/2
3/4
7/8
full
0
1/4
1/2
3/4
7/8
full
Fuel,
lbm/hr
2.75
4.07
5.18
6.96
5.33
6.45
7.38
10.2
13.2
16.7
5.76
6.60
7.43
15.5
17.6
21.1
7.54
9.84
10.9
14.1
18.9
22.8
25.1
9.89
14.6
18.5
23.0
25,8
27.7
Mass Emissions in g/hr
HC
302.
232.
108.
131.
146.
157.
127.
151.
210.
287.
97.9
96.7
97. 4
246.
303.
437.
50.6
87.9
98.9
153.
237.
313.
356.
51.4
96. 8
183.
265.
207.
384.
CO
974.
1700.
1840.
2360.
1940.
2240.
2190.
3060.
4510.
5820.
1980.
1850.
1360.
4710.
57-7^.
8650.
947.
1920.
2140.
3450.
6070.
7870.
9440.
1250.
3210.
4870.
7980.
9220.
9190.
NOX RCHO
1.15 1.1
2.87 1.5
•51 q
3 ;>3
8.22 0.93
29.9 1.6
Q3 Q
-a Q?
4 Q4
i A 7
C.Q q
1 7 O
E.C. ft _-___
co 7
Part.(a) SOx
7.22 0.41
4.01 0.69
0 96
i ^n
I 19
8.71 1.38
19.5 1.92
? 4ft
313
1 Oft
1 ?S
- - -- 141
. ? Q2
Q -30
•3 q-a
I 45
„__ i 88
- -- 2 08
2 68
24.5 3.58
431
4 74
_ 1 Q 1
. 281
353
29.3 4.37
4 94
32.4 5.24
Specific Emissions in g/hp-hr
HC
28.
17.
53.
21.
12.
11.
12.
28.
13.
11.
12.
15.
21.
12.
9.
10.
11.
10.
10.
9.
9.
£,
11.
6
2
2
3
7
7
1
5
6
8
3
7
5
3
56
0
3
9
2
68
40
AC,
5
CO
487.
312.
758.
369.
257.
252.
247.
547.
190.
226.
235.
311.
472.
266.
216.
257.
284.
291.
338.
258.
283.
7R7
275.
NC
0.
4.
1.
1.
2.
2.
3.
1.
2.
2.
2.
1.
5.
4.
3.
2.
2.
1.
3.
2.
2.
2
1.
)x RCHO Part, (a)
76 0.41
21
09
38 0.16 1.46
51 0.13 1.64
85
55
46
33
83
52
46
24
06
14
48 1.04
34
99
30
91
06 1.04
06
67 0.97
SO.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
o
0
,
.26
.17
.40
.23
.16
. 14
.13
.37
. 20
.14
.13
. 14
.46
.26
. 17
.15
.16
.15
. 30
. 19
. 16
1 S
.16
(a) These particulate values are for a 50:1 gasoline:oil ratio
(b) Calculated
(c) Estimated - engine could not be run at full load and 2500 rpm to calculate partial loads
-------
The graphs are given as Figures 13 through 16 and include emissions
of total hydrocarbons, CO, NOX, and aldehydes (RCHO). These plots have
been made on semi-logarithmic graph paper to permit legible inclusion of
mass emissions data which span wide ranges, almost three decades in
some cases. Note also that all four graphs on any one page do not neces-
sarily have the same ordinate, due to the rather large variations from
engine to engine for some emissions. The major purpose of Figures 13
through 16 is to show trends in mass emissions with engine load and
speed, and any ambiguity in the assignment of parameters can be resolved
by referring to Tables 5, 7, 8, and 9. These tables are likewise to be
consulted when specific mode values are needed, because the accuracy of
the plots is low compared to tabular values. Note that on semi-log paper,
the ordinate of a curve calculated from constant concentration values would
increase with increasing load but that it would decrease in slope with in-
creasing load (it would be concave downward). Neglecting the zero-load
point, the 6500 rpm curve for the Rotax in Figure 13 (HC mass emissions)
is a reasonably good approximation of a constant-concentration curve.
Referring to Figure 13 again, HC emissions ranged from about
130 g/hr to about 3600 g/hr for the 2-stroke engines. The range for the
OMC rotary was from about 50 g/hr to about 440 g/hr. Effects of speed
on mass emissions of HC were relatively uniform for the 2-stroke engines,
with higher speeds producing more HC under most conditions. Emissions
of HC from the OMC rotary, however, were only slightly dependent on
speed. All the engines exhibited HC emissions quite strongly dependent
on load (or throttle opening). Hydrocarbon emissions from the Rotax
were quite high, considering its small size, probably as a result of a high
delivery ratio.
Figure 14 shows CO emissions, and the scatter in evidence for the
Arctic 440 and the Rotax 248 is probably due primarily to changes in fuel/
air ratio. As has been shown in other studies^ 1^, 13, 14); QQ production
is very sensitive to fuel/air ratio. In addition, not all the test modes
were used during any one run on the Arctic 440 (high load conditions were
run last, and only for short times, to prevent engine overheating); so some
day-to-day variations may be in evidence. Of particular interest, also,
are the consistently low (although not entirely smooth) CO emissions from
the Rotax 248 (20 to 560 g/hr) and the consistently high CO emissions from
the OMC 528 rotary (950 to 9440 g/hr). The low CO values for the Rotax
as compared to the other 2-strokes probably result from a high delivery
ratio and consequent good scavenging.
Emissions of NOX for the four engines are shown in Figure 15,
and here the speed and load effects are quite pronounced. These NOX
values are generally very low, with few data points exceeding 100 g/hr.
Although relation of NOX emissions to the independent variable and para-
meter differs from engine to engine, mass emissions over a composite
26
-------
-------
m
a
o
•rH
CO
to
w
o
o
CO
a
o
w
o
u
FIGURE 14. CARBON MONOXIDE EMISSIONS FROM FOUR SNOWMOBILE
ENGINES AS FUNCTIONS OF EOAD, WITH ENGINE SPEED AS
PARAMETER DATA FROM TABEES 5, 7, 8, AND 9
28
-------
0
0
25 50
75 100
25 50~~~ 75 100
Percent Full Load Percent Full Load
FIGURE 15. OXIDES OF NITROGEN EMISSIONS FROM FOUR SNOWMOBILE
ENGINES AS FUNCTIONS OF LOAD, WITH ENGINE SPEED AS
PARAMETER - DATA FROM TABLES 5, 7, 8, AND 9
29
-------
SO
TE
n-
! 50~
-:-- ' .-:gs---~--- - = ~-
>•"—-:'-_
TT-Jg'
5E
&J£
- ;y^
•-•PS ;^?
m
-i:
25---^ 50. --" 7,
3tr
^Load
'100
-P^f€
-Fall to;
-iSl
9..
8
7
6
^TlviC 52
K
ARV
- -Q
7_
6 .
5_
^T~
5 -
U&r-S-
o ---+
~J
——P-e-r-e-ent -F
:zz2s:ii:
—P^rtrertt
i^vk:
FIGURE
TOTAL,; .
P-OUR
SNOV^MOB]
ALDEJPIYDE
LE
AS FUNG1
(RCHO)
EIV
ISSIGH
PARAMETER P DAlfA FR
.J i I i --
30
lONSiOF -LOAD,
DM TABLES
5, 7,
JIR
WITH
8, ar.d 9
FROM
-------
cycle of realistic operation will probably not vary over a wide range from
one engine to another. Although NOX mass emissions from the OMC
rotary peaked out at levels equal to or below peak levels from the 2-
strokes, NOX from the rotary w.as generally higher at mid-load and low
load conditions.
The curves showing mass emissions of total aliphatic aldehydes
in Figure 16 are somewhat sketchy compared to those already analyzed.
The reason for the lesser number of data points for aldehydes is simply
that wet chemistry analysis is time-consuming, and the importance of
the aldehyde measurements did not justify a larger effort. Aldehydes
show quite a strong dependence on speed and load for the 2-stroke engines,
but an insufficient number of points were acquired on the OMC rotary
for the drawing of such conclusions. It should be noted, however, that
the few points acquired for the rotary engine were somewhat below com-
parable data for the 2-strokes.
C. Particulate and Smoke Results
Particulate measurements were taken on the exhausts of the
snowmobile engines using the experimental sampler described in Section
III. B. and shown in Figure 11. The results of these measurements were
first obtained on a concentration basis, and they are presented in concen-
tration terms in Table 10 to document variability. Table 10 shows that
reasonable repeatability was achieved for most conditions and that dif-
ferences from one condition to another, one engine to another, and one
fuel mixture to another were the more important types of variation.
For all conditions except one (Polaris 335, 6500 rpm full load), higher
oil concentrations in a given engine produced higher particulate concentrations.
Using data on mass emissions from Tables 5, 7, 8, and 9, Figure
17 was constructed to provide a better feel for particulate variation with
speed, load, and engine. The overall trend is an increase in particulates
emitted with increasing speed and load, -which is not a surprising result.
The data plotted in Figure 17 are for the gasoline:oil ratios recommended
by the respective engine manufacturers for the 1972-1973 models, although
other data are available (Table 10) to show the influence of oil concentration
on particulate emissions. The particulate data obtained at oil concentrations
other than those recommended by the manufacturers are shown in Figure 17
on the graphs for the Polaris and Rotax engines.
Smoke measurements were obtained on the three 2-stroke snow-
mobile engines using the PHS smokemeter shown earlier in Figure 12.
No smoke measurements were acquired on the OMC rotary engine. It
should be noted that the PHS smokemeter was used as a research tool
only and not because it is recommended for use with white smoke. While
it is felt that the meter gives accurate results as to the opacity of white
31
-------
TABLE 10. PARTICULATE CONCENTRATION DATA ON FOUR SNOWMOBILE ENGINES
Condition
Participate Cone. , mg/SCF
Condition
rpm
1560
2500
2500
4000
4000
5500
7000
I \J W
i ni n
1 v A v
7^00
£. I? U\/
7^OO
tr.? >_/ V
Ac.OO
*X_J VU
,1 c no
*X_) U U
A c: nn
O D UU
A Ci OO
D _) UVJ
1850
2500
3000
4000
5000
5000
6500
Load
Idle
0
full
0
full
full
full
AULJ.
Trll*»
J.U1C
0
u
1 /4
J. / T
1 /4
l / ^
•3/4
J / rt
•J/4
J/ *t
f., 11
IU11
Idle
0
1/4
1/2
3/4
full
full
Run 1 Run 2
Arctic 440,
39.3 40.9
63.8 66.2
43.1 70.7
28.2 40.6
34.7 33.1
32.0 22.2
35 2 2Q 2
•J J * t-i t*jtf*
Polaris 335,
1 1 7 7A 7
11* f £O t, U . U
100 ft "^0
A w , W O , J VJ
10^ R 7fl
1 u . -? o . ^>o
9fl7 Q Q7
.Of 7 . 7fc
1 A ^ IRQ
1 O . J 1 O . 7
Rotax 248,
3.67 5.63
4.42 5.94
8.88 11.4
14.3 15.0
16.0 18.4
12.9 16.4
9.76 11.4
Run 3
20:1 Fuel
49.8
69.9
55.4
30.8
35.3
27.6
40:1 Fuel
50:1 Fuel 1
-..-.
_-!--
Avg.
Mix
43.3
66.6
56.4
33.2
34.4
27.3
37 ?
J t* • L*
Mix
1 Q ?
i 7 . £
20 2
£< V/ * £.
1 ft Q
1 O . 7
Q IS
7 * 1 ->
Q 7Q
7 . £7
Q QO
7 . 7"
177
i i • i
Vlix
4.65
5.18
10.1
14.6
17.2
14.6
10.6
rpm
1010
2500
2500
4500
4500
6500
6500
1850
2500
3000
4000
5000
5000
6500
1370
2500
3500
3500
5000
6000
6000
Load
Idle
0
1/4
1/4
3/4
3/4
full
Idle
0
1/4
1/2
3/4
full
full
Idle
0
1/4
1/2
3/4
3/4
full
Cone. , mg/5CF
Run 1
Run 2
Polaris 335, 20
26.4
59.3
26.3
9.96
12.5
10.6
UL,
36.1
41. 0
22. 7
8. 49
12.3
10. 4
1 C. I-.
Rotax 248, 20:
43 4
34 4
^0 ft
37 A
26 7
28 1
21 0
OMC
14.3
6.61
6.58
10.6
8.48
8.62
7.51
3£. L
33 R
34 4
34 3
7"\ 7
77 1
1 Q ft
528 Rotary,
12.8
3.62
6.71
9.67
5.93
7.34
7.27
Run 3
Avg.
:1 Fuel Mix
1 Fuel Mix
50:1 Fuel
14.3
7.75
5.58
10.1
7.56
5.98
6.00
31.2
50.2
24. 5
9. 22
12.4
10.5
1 4 A
4fi I")
34 1
37 L
"^A n
75 ?
77 A
70 4
Mix
13.8
5.99
6.29
10.1
7.32
7.31
6.93
-------
FIGURE 17. PARTICULATE EMISSIONS FROM FOUR SNOWMOBILE
ENGINES AS FUNCTIONS OF LOAD, WITH ENGINE SPEED AS
PARAMETER DATA FROM TABLES 5, 7, 8, AND 9
33
-------
smoke plumes, these opacity values may not relate to plume visibility the
same way as for black smoke^-5'. In particular, white smoke may be more
visible than black smoke for a given opacity value. This difference might
be attributed to contrast with background, or more probably, to the stronger
angular scattering exhibited by white smoke (I"'.
The smoke data are summarized in Table 11, with each average
value representing two to four original data points. Smoke values showed
a great deal of variability, but there is a general trend toward higher
opacity values for higher oil concentrations. To document the appearance
of smoke from snowmobile engines, Figures 18 through 20 show three
different levels. Figure 18 shows smoke measured at 8 percent opacity
as viewed in bright, direct sunlight. Figure 19 shows smoke measured
at 14 percent opacity as viewed under overcast conditions. These photo-
graphs also show the difficulty in making an objective visual smoke eval-
uation where ambient light conditions, viewing angle, and background are
not constant. The smoke being emitted was generally somewhat more
visible than the photographs make it appear, possibly due to absence of
color in the photos and the ability of the eye to see smoke puffs better than
the still camera. The limit of visibility appeared to be about 2 to 3 percent
opacity, with lower levels being indistinguishable from the background.
Figure 20 shows smoke measured at 2 percent opacity in bright, direct
sunlight, with the small contrast within the ring being its only visible point.
The pipe shown in the photos was a 4 foot extension of 2 inch diameter, and
about 4 feet of 3- or 4-inch pipe connected it to the engines' mufflers. The
pipe probably had little effect on the smoke readings due to its short length.
34
-------
TABLE 11. SUMMARY OF AVERAGE SMOKE OPACITY FROM 2-STROKE
SNOWMOBILE ENGINES, BASED ON 2-INCH DIAMETER OUTLET
Arctic Cat 440
Polaris 335
Rotax 248
OJ
Ul
Condition
rpm
1560
2500
2500
2500
4000
4000
4000
5500
5500
5500
7000
7000
7000
Load
Idle
0
1/2
full
0
1/2
full
0
1/2
full
0
1/2
full
% Opacity
20:1 Mix
1.9
2.7
4.3
20.
1.0
0.5
0.5
2.9
2.1
0.8
1.7
0.5
0.7
Condition
rpm
1010
2500
2500
2500
4500
4500
4500
5500
5500
5500
6500
6500
6500
Load
Idle
0
1/2
full
0
1/2
full
0
1/2
full
0
1/2
full
% Opacity
20:1 Mix
0.4
1.4
2.0
4.5
0.9
0.8
11.
1.4
9.
1.2
2.2
0.8
1.6
40:1 Mix
0.2
0.8
1.1
1.9
0.3
0.4
1.4
1.0
0.8
1.0
1.4
0.9
1.0
Condition
rpm
1850
2500
2500
3000
3000
3000
4000
4000
5000
5000
5000
6500
Load
Idle
0
1/2
0
1/2
full
1/2
full
0
1/2
full
1/2
% Opacity
20:1 Mix
3.0
4.2
16.
3.8
12.
25.
7.5
12.
3.0
3.
7.
1.
50:1 Mix
1.1
1.3
2.0
1.4
3.3
8.3
2.4
4.7
1.1
1.3
2.1
0.9
-------
* * 1
FIGURE 18. 8% OPACITY SMOKE
FROM A SNOWMOBILE ENGINE
FIGURE 19. 14% OPACITY SMOKE
FROM A SNOWMOBILE ENGINE
FIGURE 20. 2% OPACITY SMOKE FROM A
SNOWMOBILE ENGINE
36
-------
V. ESTIMATION OF EMISSION FACTORS AND NATIONAL, IMPACT
In order to develop emission factors for snowmobiles, mass
emission rates must be known, and operating cycles representative of
usage in the field must be either known or assumed. Extending applicability
of data on a few engines to the population requires additional input on the
composition of the snowmobile population by size and type. It is also
necessary to have data on annual usage and total machine population when
national emissions impact is estimated.
A.
Development of Emission Factors
Operating data on snowmobiles are somewhat limited, but enough
are available so that an attempt can be made to construct a representative
operating cycle for the purposes of this report. The required end products
of this effort are time-based weighting factors for the speed/load conditions
at which the test engines were operated; and use of these factors will
permit computation of "cycle composite" mass emissions, power, fuel
consumption, and specific emissions.
Since the operating data and other information on normal snow-
mobile driving patterns comes from a variety of sources, a summary
will be made so that the validity of assumptions made later can be assessed.
Table 12 shows dynamometer operating cycles used by two manufacturers
.(PolarisV-1- ?) and John Deere(l°)), indicating high overall load factors,
TABLE 12. DYNAMOMETER OPERATING CYCLES
USED BY TWO MANUFACTURERS
Polaris Data<17)
rpm Throttle Opening % of Time
1500
3500
4500
5000
6000
6500
7000
7500
0
1/4
1/2
3/4
full
full
full
full
13. 2
13.2
15.8
17. 1
35.5
2.6
1.3
1.3
John Deere Data(18)
rpm Throttle Opening % of Time
2500
5000
6500
6500
6500
0
1/4
1/2
3/4
full
28.6
22. 7
18.1
2.9
27.6
and these cycles are presumably used for accelerated-stress testing of
engines and/or driveline components. It is doubtful that they represent
37
-------
field operation accurately, and they probably are not intended to do so.
Table 13 presents estimates from Massey-Ferguson (Ski-Whiz)^ "',
obtained through test experience and customer use contacts. These
TABLE 13. ESTIMATES OF AVERAGE OWNER USAGE
FROM MASSEY-FERGUSON
Throttle Opening
Idle
1/4
1/2
3/4
full
Speed, mph
Owners from Northern Regions
and in Mountains
Owners from Metro. Areas
Spending Weekends North
5
30
45
15
5
5
35
35
20
5
% of Operating Time for
Conditions
15 Trail Riding
15 Heavy Lugging in Wet
Snow & Towing Sleds
ZO Breaking Trails in
Fresh Snow
20 Hill Climbing
35 Operating on Lakes
and Packed Snow
50 High Speed Operation
Owners from Northern
Regions and in Mountains
40
5
20
10
20
5
Owners from Metro. Areas
Spending Weekends North
60
5
10
5
15
5
estimates indicate a division in rider habits depending ostensibly on area
of residence but perhaps actually depending on rider experience or the
types of use the riders make of their sleds (purely recreational for the
metropolitan group versus recreational plus utilitarian for the northern/
mountain group).
In addition to the tabular data already presented, several sources
have made generalizations on snowmobile operation, such as, "The
snowmobile's variable-speed transmission is such that almost all loaded
operation occurs between 4000 and 5500 rpm".' ' Another source said
that snowmobiles ". . . are operated in a range from 4500 to 6000 rpm with
a bulk of the running in the 5000 to 5500 rpm range". (21)
38
-------
The final item of operating data' ', and the most useful, ib
shown in Table 14. This tabulation shows percentage of operating time
as a function of both engine rpm and throttle position for data taken on
three snowmobiles operating at high altitude in the Colorado Rockies.
TABLE 14. FIELD USAGE DATA DEVELOPED BY JOHN DEERE
rpm
0-
500-
1000-
1500-
2000-
2500-
3000-
3500-
4000-
4500-
5000-
5500-
6000-
6500-
499
999
1499
1999
2499
2999
3499
3999
4499
4999
5499
5999
6499
6999
of Operating Time at Throttle Opening (%) and rpm
0
q<
0
o
n
4.
5 .
5.
6.
0.
0.
%
} 7
04
4^
38
05
59
04
64
02
1C
19
n
3.
6.
7.
10.
3.
0.
)-
'%
? 1
67
05
90
23
84
09
2C
29
0.
0.
1.
5.
6.
0.
)-
%
22
94
86
82
72
73
3(
39
0.
0.
0.
2.
5.
1.
n
)-
'%
09
44
61
06
20
69
n^
4C
49
0.
0.
0.
0.
2.
1.
n
)-
%
04
21
31
66
19
72
n«
5C
59
0.
0.
0.
0.
1.
1.
n
)-
%
02
20
28
48
14
38
nq
6(
69
0.
0.
0.
0.
0.
1.
n
)-
'%
02
14
22
36
99
27
nq
7C
79
0.
0.
0.
0.
0.
1.
n
)-
'%
02
13
25
37
86
28
1 4
8(
89
fi
0.
0.
0.
0.
0.
1.
n
)-
%
n i
01
09
19
18
95
28
1 4
9C
IOC
0.
0.
0.
0.
0.
0.
n
)-
)%
02
05
16
09
13
34
01
These data were carefully qualified by John Deere regarding possible lack
of applicability to average snowmobile operation, but at this point they
represent the only available quantitative information acquired under field
conditions. Since no better information is available at present, the John
Deere data in Table 14, modified where necessary, have been chosen to
form the basis for a snowmobile duty cycle applicable to the test engines.
The first modification of the Table 14 data necessary for the pur-
poses of this report is to regroup the percentages of operating time on
intervals corresponding to load increments used in this study. At the
sa ,2 time, the rpm intervals have been combined into 1000 rpm increments;
and an arbitrary 10 percent has been included as idle time. These mod-
ifications result in the data shown in Table 15; and it should be noted that
the rpm increment centered on 3500 rpm includes the interval 3000-3999
rpm, and so forth for the other categories.
The test procedure used for each test engine was somewhat dif-
ferent than those used for the others, both in selection of operating speeds
39
-------
TABLE 15. REGROUPED AND MODIFIED FIELD USAGE DATA
% of Operating Time at rpm and Load
Load Idle 3500 rpm 4500 rpm 5500 rpm 6500 rpm Subtotals
full --- 0.1 0.1 0.2 0.4
7/8 --- 0.3 1.0 1.3 2.6
3/4 --- 0.6 2.2 2.4 5.2
1/2 0.1 1.3 6.0 3.6 11.0
1/4 0.7 4.8 17.9 1.8 25.2
1/8 4.7 14.7 13.5 0.1 33.0
0 10.0 3.0 6.0 3.8 --- 22.8
Subtotals 10.0 8.5 28.1 44.5 9.4
and the loads used in conjunction with those speeds, as shown in Table 2.
These differences made it necessary to modify the data in Table 15 some-
what for each engine, reflecting the various speed/load conditions used.
The time-based weighting factors generated by this process are given in
Table 16, and these factors are the ones which will be used in determining
emission factors. To explain some of the deviations of the weighting factors
in Table 16 from the data in Table 15, it should be noted that the speed
range (above idle) for each engine is somewhat different, making the speed
subtotals vary from engine to engine. Again on speed subtotals, the Rotax
is weighted more heavily toward maximum rpm than the other engines
because power output was more strongly dependent on speed for the Rotax
than for the other engines near maximum speed. The larger weights given
the maximum speed (6500 rpm) had the effect of increasing the composite
load factor without undue increases in the weighting factors for the high-
load conditions.
Looking at the load subtotals, those for the Arctic 440 and the OMC
528 Rotary are fairly close to those for the field data in Table 15. The
subtotals for 1/4, 1/8, and zero loads on the Polaris and Rotax, however,
show higher factors at 1/4 and zero loads and a lower factor at 1/8 load.
This discrepancy is due to omission of the 1/8 load condition from the
schedules of the Polaris and Rotax at several speeds, which was the re-
sult of the apparently inaccurate assumption that this condition was not
important in the duty cycle. The omission was compensated for by increasing
the weights of the 1/4 load and zero load conditions in such a way as to keep
the composite horsepower (or load factor) constant. The higher load con-
ditions for the Rotax were given somewhat more weight than those for the
other engines because the weight/power ratio for the Bombardier Elan 250T
(which uses the Rotax 248) is about 31 lbf/hp (loaded), as compared to a
range of 19-22 for machines in which the other three engines are used.
40
-------
TABLE 16. TIME-BASED WEIGHTING FACTORS FOR SNOWMOBILE ENGINE EMISSIONS RESULTS
Arctic 440-% Time at rpm&i Load
Polaris 335 - % j. ime at rpm & Load
Load
full
7/ft
3/4
1/2
1/4
1/8
0
Subtotals
Load
full
7/8
3/4
1/2
1/4
1/8
0
Subtotals
Idle 2500
*#
**
*#
##
** 2
10 1
10 3
Rotax 248
Idle 2500
## **
** **
## *#
. .
*?*?
*#
** 2
10 1
10 3
4000
1
2
15
6
5500
i
2
6
20
18
3
24 50
- % Time at
3000
**
**
1
4
2
7
4000
1
2
5
14
5
27
7000 Subtotals Idle
? ^ **
2 4 **
4 11 **
3 25 **
1 36 **
20 10
13 10
rpm &c Load
5000 6500 Subtotals
1 2 3
1 5 6
25 8
55 12
16 5 27
* * 20
6 24
31 22
2500
*
*
2
1
3
OMC
Idle
**
**
*#
**
**
##
10
10
3500
1
4
3
4500
1
1
15
*
10
8 27
528 Rotary -
2500
*#
**
**
*
3
3
3500
##
*#
1
5
4
10
5500
1
2
5
26
#
8
42
% Time
4000
1
*
5
13
6
25
6500
1
2
4
*
*
7000
i
i
#
*
*
**
8 2
at rpm&cLoad
5000
1
1
2
5
17
13
4
43
6000
1
1
2
3
2
*
- _ — _
9
Subtotals
2
3
5
10
42
6
32
Subtotals
2
2
5
8
25
31
27
* No data taken
** No data taken, and point computed to have zero weight
-------
Earlier in the report, it was noted that the Arctic 440 engine was
subjected to a special set of runs intended to assess emissions changes
when the carburetor high-speed jet was set richer than normal. This
change in jet setting is a recommended field adjustment when operating
temperatures get too high, and the data obtained under rich conditions
were presented in Table 6. Since the "rich" data were acquired at rel-
atively few operating conditions, it was necessary to modify the weighting
factors shown in Table 16 somewhat to apply to the Table 6 data. The
aim of the changes was to keep the load factor as constant as possible
using available data points, and this goal was essentially accomplished.
These same comments apply in general to emissions of aldehydes and
particulate from all the test engines.
Based on calculation techniques from Section III. D. and data
from Tables 5 through 9 and 16, composite mass emissions and com-
posite brake specific emissions were calculated for the four snowmobile
engines tested (including the "rich" runs on the Arctic 440). These data
are presented in Table 17 along with calculated composite power outputs,
load factors on fuel and power bases, and fuel rates. These composite
results show considerable variation from engine to engine, but it appears
that most of the variations can be explained by examining design and
tuning differences in the engines.
To begin, the most obvious design differences are between the
three 2-stroke engines (as a group) and the rotary. The absence of fuel
short-circuiting in the rotary as compared to the 2-strokes explains the
rotary's lower specific hydrocarbon emissions; and this same feature
had some effect on particulate emissions, also. The combustion process
in the rotary appears more like that in a 4-stroke engine than that in a 2-
stroke engine. This same design difference contributed to the higher CO
and SOX emissions of the rotary, since a greater fraction of the fuel
charge was being burned in the rotary.
The major variations between the individual 2-stroke engines can
probably be explained by (1) the relatively lean mixture used by the Arctic
(in stock configuration), as compared to the Polaris and the Rotax; and
(2) the high delivery ratio used in the Rotax, as compared to the Arctic
and the Polaris. The first of these explanations had a lot to do with the
Arctic's low CO, HC, and RCHO (compared to the Polaris). Note that
mixture was singled out as a causative factor because the Arctic and
Polaris were otherwise quite similar (specific output, compression ratio,
and delivery ratio/port timing as determined by fractions of fuel short-
circuited). Additional credence is lent to this deduction by the fact that
the Arctic engine consistently ran hotter than the Polaris under similar
conditions.
42
-------
TABLE 17. CYCLE COMPOSITE MASS AND SPECIFIC EMISSIONS FOR FOUR SNOWMOBILE ENGINES
Load Factors
Composite Fuel Rate
Composite Emissions, g/hr
Engine
Arctic 440
Arctic 440 (Rich)
Polaris 335
Rotax 248
OMC 528 Rotary
Engine
Arctic 440
Arctic 440 (Rich)
Polaris 335
Rotax 248
OMC 528 Rotary
Power Fuel Ib^/hr agal/hr
0.204 0.240 5.60 0.90
0.211 0.265 6.81 1.10
0.212 0.265 6.33 1.02
0.233 0.353 4.66 0.75
0.217 0.345 9.57 1.54
Composite
Power, hp Fuel Cons. , Ibr^/hp-hr
6.40 0.88
6.38 1.07
5.59 1.13
3.78 1.23
7.05 1.36
HC
567
701
662
739
145
CO
909
1720
1310
238
2510
NOX RCHO
9.15 5.7
6.18
10.1 14.
12.7 5.3
21.2
cpart
38. 1
13.8
9.40
10.2
bsox
0.85
1.02
0.95
0.59
1.81
Composite Specific Emissions, g/hp-hr
HC
88.6
110.
118.
196.
20.6
CO
142.
270.
235.
63.0
356.
NOY RCHO
1.43 0.88
0.97
1.81 2.5
3.36 1.5
3.01
cpart
6. 13
2.50
2.60
1.50
bSOY
0. 13
0. 16
0. 17
0. 16
0.26
aAssuming 6. 2 lbm/gal
^Calculated from fuel consumption assuming 0.043 percent by weight fuel sulfur content(23)
cBased on gasoline:oil ratios of 20:1 for the Arctic, 40:1 for the Polaris, and 50:1 for the Rotax and the OMC
-------
The second of the two explanations is probably responsible for
the relatively high HC and NOX and the relatively low CO emitted by
the Rotax. The high delivery ratio (diagnosed by the 35 percent of fuel
short-circuited by the Rotax, compared to 23 percent for the Arctic and
Polaris) probably contributed to the high HC directly, and indirectly to
the low CO and high NOX, because the cylinders were probably scavenged
more completely than those of the other two engines. The high delivery
ratio also contributed to the much cooler running of the Rotax as com-
pared to the Artie and Polaris.
The particulate results tend to confirm several points in the fore-
going analysis. First, the much higher specific value for the Arctic
(even through it ran on a leaner mixture) can be traced to the 20:1 gas-
oline:oil mixture recommended for it, as compared to 40:1 for the Polaris
and 50:1 for the Rotax. In addition, the contribution of fuel short-circuiting
to particulate emissions is emphasized by the higher specific particulate
value for the Rotax as compared to the Polaris, even though the latter
used a. higher oil concentration.
The special runs on the Arctic 440 using a richer-than-normal
high-speed jet setting resulted in the expected outcome, namely, lower
NOX (and lower operating temperatures) and higher HC and CO. The
fraction of fuel short-circuited was the same for both sets of runs on
the Arctic.
The power-based load factors shown in Table 17 are fairly close
for all the engines, but there is a slight variation (intentionally) related
to the weight/power ratios of the machines in which the engines are used.
The degree of difference between the power-based and fuel-based load
factors for a particular engine reflect the difference in specific fuel con-
sumption between the maximum-power condition and the conditions under
which the engines are assumed to be operated in service. In order to
gain an understanding of the variation in emissions and fuel consumption
with load factor, two other operating cycles were constructed for each
engine. These alternate cycles both had higher load factors, and the
results of this analysis are presented in Table 18. The alternate cycles
are composed of the same speed/load conditions as used to make up the
cycles shown in Table 16, but with more weight given the higher power
conditions.
The cycles based on higher load factors generally produced higher
mass emissions, except for CO from the Rotax and HC from the rotary
(both of which were quite minimal to begin with). Specific emissions
varied less strongly with changes in operating cycles,and exhibited both
increases and decreases with increasing load factor, depending on the
particular engine and constituent being considered. Fuel consumption
increased with increasing load factor in all cases; but specific fuel con-
sumption generally decreased, indicating that operating conditions nearer
to maximum power were being used a greater percentage of the time.
44
-------
TABLE 18. VARIATION IN MAJOR EMISSIONS AND FUEL CONSUMPTION WITH OPERATING CYCLE LOAD FACTOR
Composite
Engine
Arctic 440
Wans 335
Rotax 248
OMC 528
Rotary
Cycle
From Table 16
Alternate A
Alternate B
From Table 16
Alternate A
Alternate B
From Table 16
Alternate A
Alternate B
From Table 16
Alternate A
Alternate B
Load
Factor
0. 204
0.326
0.438
0. 212
0.333
0.455
0. 233
0.337
0.481
0.217
0.307
0.416
Fuel
lbm/hr
5.60
7.43
10.3
6.33
7.95
10.4
4.66
5.47
7.33
9.57
9.98
12.5
Rate
gal/hr
0.90
1.20
1.66
1.02
1. 28
1.68
0. 75
0. 88
1.18
1.54
1.61
2.02
Fuel Cons.,
lbm/hp-hr
0. 88
0. 73
0. 75
1.13
0. 90
0.87
1.23
1.00
0.94
1.36
0.98
0.90
Power,
6. 40
10. 2
13. 7
5. 59
8.80
12.0
3. 78
5.46
7. 79
7. 05
10. 2
13.9
Mass
HC
567
904.
1200.
662.
868.
1230.
739.
860.
1160.
145.
171.
155.
Emissions,
CO
909.
1910.
2490.
1310.
1710
2290.
238.
205.
275.
2510.
2700.
3610.
g/hr
NOV
9.15
19.0
29.0
10. 1
17. 7
28. 8
12.7
18.9
30.7
21.2
25.4
34.4
Specific
HC
88.6
88. 6
87.6
118.
98.6
102.
196.
158.
149.
20.6
16.8
11.2
Emissions,
CO
142.
187.
182.
235.
194.
191.
63.0
37.5
35.3
356.
265.
260.
g/hp-hr
NOX
1. 43
1. 86
2. 12
1. 81
2.01
2. 40
3.36
3. 46
3. 94
3.01
2.49
2.47
-------
, II
The data in Table 18 generally support the choice of the John
Deere operating data'^2) as ^Q basis for the assumed operating cycle
for the purposes of this report. The primary factor involved is the fuel
consumption, which seems quite a bit more reasonable for the "Table 16'
cycles than for either of the alternates. The lowest set of fuel consumption
figures gives an average operating time for machines using the test engines
of 5. 3 hours per tank of fuel, while the middle set yields 4. 3 hours and
the highest set 3.3 hours.
The total engine power required to propel a snowmobile under any
set of conditions can be considered as
power - (velocity)(total drag/ drive train efficiency).
The "total drag" term in this equation is composed of an undefined mix-
ture of forces including sliding friction, air resistance, rolling resistance
of the track/ snow interface, force required to displace parts of the snow
surface, and possibly others. Some of these forces may be essentially
independent of velocity (V), while others are proportional to V or perhaps
even higher powers of V. As a result, the power to propel a snowmobile
is proportional to velocity raised to some power, probably between 1 and 3
(power oc V would be analogous to low-speed sliding friction, while power
ocV would be roughly analogous to a displacement-hull ship, a fan, or
an automobile). Losses in the drive train also vary with rotational speed
of the components. These ideas and some assumptions about snowmobile
ground speeds can lead to a (simplified) calculated load factor which can
be compared to those shown in Table 18.
Referring back to data presented in Table IS '', an average speed
for each category of snowmobile usage can be calculated from the bottom
set of numbers; and these averages turn out to be 22. 2 mph for "Northern"
owners and 20.5 mph for "Metropolitan" owners. If the average of these
two numbers (21. 4 mph) is considered typical, and if a typical snowmobile's
top speed can be estimated at 45 mph, then it remains only to choose a
velocity exponent as described above to calculate a load factor based on
operating speed. In mathematical terms
estimated load factor = (21.4 mph/45 mph)x,
where x is the velocity exponent. Based on experience with other types
of machines, the best estimate for the velocity exponent is 2.0; less
than that for a planing-hull boat (2.5) but greater than that for a simple
sliding block (1.0). Inserting this estimate into the equation above yields
estimated load factor = (21. 4 mph/45 mph)2- ° = 0. 226,
46
-------
which is quite close to the 0.216 average load factor for the assumed
operating cycle. If the exponent chosen had been 1.8, the calculated
load factor would be 0. 262. If the exponent had been 2. 2, the load factor
would be 0. 195. Consequently, small changes in the velocity exponent
do not alter the conclusion that the operating cycle given in Table 16 is
more representative than the alternate cycles. It is conceded that the
derivation of the assumed operating cycle is not rigorous, but in the
absence of more comprehensive data on field operation, it is the best
effort possible within the scope of the subject contract.
To arrive at emission factors which have a degree of applicability
to the snowmobile population as a whole, the logical starting point is to
reiterate available data on the composition of that population. Considering
machines in service as of the 1972-1973 season, the OMC rotary engine
is a minor factor, with approximately 5000 units in the field (or about
0.34 percent, as will be shown later). The best estimates of a population
breakdown by size and other pertinent quantities comes from a survey of
magazine subscribers^ ', which generated data shown in Table 19. Some
TABLE 19. DESCRIPTION OF SNOWMOBILES OWNED AND OPERATING
DATA OBTAINED FROM A SURVEY OF MAGAZINE SUBSCRIBERS
Engine
Displ. ,
cm
0-295
296-340
341-400
401-600
601 &up
Sizes
% of
Owners
22.5
27. 8
27. 0
17. 7
5. 1
Brand Ownership (Engine)
Brand
Ski-Doo (Rotax)
Arctic Cat (own)
Polaris (own)
Sno-Jet (Yam. )
Rupp (own)
Moto-Ski (BSE)
% of
Owners
31. 7
23.4
6.9
6.2
5.4
4.9
Scorpion (CCW, JLO) 4.9
Others
16.6
Fuel Mixtures
Ratio
20:1
24:1
40:1
50:1
% of Owners
69.3
16. 4
17. 9
2. 4
Machine
Time
Single Riding
Double Riding
Usage
14 hr/wk
75%
25%
Age of Machines
Model Year
1972
1971
1970
1969
1968
1967 & prior
% of
Owners
24.9
29.4
21.8
12.3
7. 4
4. 2
Consumption per Week
Gasoline
Oil
*Total Fuel
11.8 gal
2.4 qt
12. 4 gal
*Sum of gasoline and oil
of these data, especially machine usage and fuel consumption, should
probably be qualified because the survey respondents may be cbnsiderably
47
-------
more active in snowmobiling than the average owner. Since both usage
and fuel consumption were from the same sample of people, however,
a comparison of the two should be valid. This comparison yields an
average fuel consumption of 0. 89 gal/hr.
To arrive at a reasonable estimate for machine size, an average
displacement will be assumed for each displacement class in the table.
These assumptions are 250cm3 for the 0-295cm3 class, 325 for the 296-
340 class, 390 for the 341-400 class, 440 for the 401-600 class, and
630cm3 for 601 cm3 and over class. Weighting the assumptions by
owner percentages from Table 19 yields an estimated average displace-
ment of 362cm3. Since a breakdown of the snowmobile population in
terms of rated power is not available, mass emissions will be restated
in terms of engine displacement; and characteristic emissions for 2-stroke
snowmobile engines will be estimated on that basis.
Table 20 shows the results of dividing mass emissions, fuel con-
sumption, and power output from 2-strokes by engine displacement. The
last line of the table also shows data resulting from taking a weighted
mean of the data on individual engines. The weights used reflect the de-
gree to which each engine is assumed to be representative of the popu-
lation of engines in service, not the relative popularity of the engines in
the marketplace. A relatively small weight was given to the Rotax 248
data, because the high delivery ratio of this engine made its emissions
quite different from engines considered more typical of those in service.
The weighted means in Table 20 are considered to be as representative
as possible of snowmobile engines in the field, so they can be considered
as estimates of characteristic snowmobile emissions for the purposes of
this report. Applying these estimates to the previously-approximated
average displacement of 362cm3 yields the estimated snowmobile emis-
sion factors given in Table 21 and an estimated average fuel consumption
of 0.94 gal/hr (very similar to the 0.89 gal/hr figure calculated from
the data in Table 19^'). The mass emission rates given in Table 17 for
the OMC rotary will be assumed applicable to snowmobiles employing
that engine.
B. Estimation of National Impact
To compute a figure for snowmobile emissions on a national basis,
it is necessary to know not only the emission factors but also total num-
ber of machines in service and annual operating time. Commenting on
the latter item first, one figure perhaps indicative of annual usage has al-
ready been given in Table 19, namely, 14 hours per week average obtained
from a survey of magazine subscribers^). This value, as already mentioned,
is probably higher than the overall average because the subscribers are
probably more enthusiastic about their snowmobiling than the average owner.
48
-------
TABLE 20. EMISSIONS, FUEL CONSUMPTION, AND POWER OUTPUT OF 2-STROKE
SNOWMOBILE ENGINES DIVIDED BY ENGINE DISPLACEMENT
-4D
Composite Power/Displ. , Fuel Cons./Displ. ,
Emissions/Displ. , g/(hr)(liter Displ. ]
Engine (Displ. , cmj)
Arctic 440 (436)
Polaris 335 (335)
Rotax 248 (247)
* Weighted Mean
hp/liter Displ.
14.
16.
15.
15.
7
7
3
8
gal/(hr)(liter Displ
2.
3.
3.
2.
06
04
04
59
.) HC
1300.
1980.
2990.
1740.
CO
2080.
3910.
964.
2700.
NOX
21.0
30.1
51.4
27.7
RCHO
13.
42.
21.
25.
Part.
87.
41.
38.
**77.
4
2
1
1
soy
1.95
2.84
2.39
2.35
* Weights are 0.5 for the Arctic, 0. 4 for the Polaris, 0. 1 for the Rotax (except participate)
** Based on mixture data from Table 19, weights for particulate were: Arctic--0. 78, Polaris--0. 20, Rotax--0.02
(after correcting for multiple answers, 78% of owners report approx. 20:1, 28% report 40:1, and 2% report 50:1)
TABLE 21. ESTIMATED SNOWMOBILE EMISSION FACTORS (ASSUMING 362 cm3 DISPLACEMENT)
Emission Factors in g/hr
HC
630.
HC
670.
CO
978.
Emission
CO
1000.
NOX
10.0
Factors
NOV
11.
RCHO
9.2
in g/gal Fuel
RCHO
9.8
Part.
27.9
Consumed*
Part.
30.
sox
0.85
sov
0.90
* Assuming fuel consumption of 0. 94 gal/hr
-------
Information submitted to ISIA by Massey-Ferguson'^ 9) (Ski-Whiz) is
summarized in Table 22, indicating about 50 to 100 hours' usage per
year depending on the type of service expected of the machine. Mr.
John F. Nesbitt, Director of Engineering of ISIA, reports that 100
hr/year was a figure used previously but that 50 hr/year is now believed
to be more accurate^ >.
TABLE 22. ESTIMATES OF ANNUAL OPERATING TIME
FROM MASSEY-FERGUSON
Hours of Usage
Owners from
Owners from Metropolitan
Northern Regions Areas Spending
Time Period and in Mountains Weekends North
Day of Usage 3 4
Week of Usage 8 6
Year of Usage 100 50
Most snowmobiles are in the "snow belt" region, defined as the
area where there is 1 inch or more of snow on the ground for at least
80 days per year' '. The season for snowmobile usage, then, is at least
12 weeks long in most cases, which means that the 14 hr/week estimate
from Table 19*1' could translate into as much as 168 hr/year. Likewise,
the weekly estimates from Table 22^ ^ could easily mean 72 hr/year to
96 hr/year (or more, considering the longer season in the northern regions
and mountains). Usage cannot be resolved quantitatively from such figures,
so an assumption must be made to permit impact computation until such
time as real usage data are acquired. This assumption will be that snow-
mobiles are operated an average of 60 hours per year.
Total snowmobile population is a more accurately-known figure,
because most states require registration. Data on registrations^^ are
presented in Table 23 and were supplied through Mr. Nesbitt of ISIA.
The most notable features of these registration data are that the total
is almost 1.5 million sleds in the U.S., that over 70 percent of the snow-
mobiles are registered in just four states ( Michigan, Minnesota, Wis-
consin, and New York), and that only about 12 percent of all snowmobiles
are found in areas outside the northeast and northern midwest.
For immediate purposes, the important figure is the total reg-
istration figure of 1.46 million, which will be assumed to be the total
population of snowmobiles in use during the 1972-1973 season for the
purposes of this report. Based on this assumption, the estimated average
annual usage figure of 60 hours, and emissions data from Tables 17 and
50
-------
TABLE 23. DISTRIBUTION OF REGISTRATIONS FOR THE 1972-1973 SEASON
State
Michigan
Minnesota
Wisconsin
New York
Maine
Massachusetts
New Hampshire
Vermont
Illinois
Iowa
North Dakota
Montana
Colorado
State Total
U.S. Total
Canada Total
Percent of
U. S. Registrations
State
368,
328,
196,
135,
65,
44,
43,
35,
28,
27,
21,
15,
14,
956
246
837
487
607
000
197
000
500
000
000
914
200
25.
22.
13.
9.
4.
3.
3.
2
1.
1.
1.
1.
1.
2
4
5
3
5
0
0
4
9
8
4
1
0
Idaho
Utah
Connecticut
Washington
Alaska
Indiana
California
Wyoming
South Dakota
Oregon
New Mexico
Nebraska
•f Penns ylvania
1, 462, 678
517, 132
State Total
Percent of
U. 5. Registrations
14,
12,
11,
10,
7,
7,
6,
6,
6,
5,
1,
55,
000
000
963
500
580
500
470
000
000
161
235
325
000
1.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
3.
0
8
8
7
5
5
4
4
4
4
1
-
8
* Estimated
-------
21, national emissions impact has been calculated and appears as Table
24. An assessment of the national importance of these emissions can
TABLE 24. ESTIMATED NATIONAL EMISSIONS
IMPACT OF SNOWMOBILES
Pollutant
HC
CO
NOX
RCHO
P articulate
*SOX
g/unit Y ear Tons Emitted per Year
37, 800
58,700
600
552
1, 670
51
60,900
94,600
967
890
2, 700
82
'''Calculated on the basis of fuel consumption and
sulfur content of 0. 043 percent by weight
be made by comparing them to revised EPA Nationwide Air Pollu-
tant Inventory data' ', which has been done in Table 25. This com-
parison shows snowmobile emissions to be minimal on a national
basis, but effects in more limited areas cannot be neglected.
TABLE 25. COMPARISON OF SNOWMOBILE EMISSION ESTIMATES
WITH EPA NATIONWIDE AIR POLLUTANT INVENTORY DATA
1970 EPA Inventory Data,
106 tons/yr(27) (Revised)
Pollutant
HC
CO
NOX
Particulate
All Sources
27. 3
100.7
22. 1
33.4
25. 5
Mobile Sources
15.2
78. 1
11.0
1.0
0.9
Snowmobile Estimates as % of
All Sources
0.223
0.094
0.004
0.008
0.0003
Mobile Sources
0.401
0. 121
0.009
0.270
0.009
Since most snowmobile operation occurs in just a few states and
mostly during three or four months of the year, the possible importance
of these machines as a localized source of pollutants cannot be dis-
counted. In particular, localized concentrations of CO and HC could
rise significantly where a number of machines are operated in a restricted
area. In most cases, areas of concentrated activity are probably rural
rather than urban due to space requirements.
A summary of estimated variation in snowmobile emissions by
season and region is given in Table 26. The northern region includes the
52
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TABLE 26. SUMMARY OF ESTIMATED SEASONAL AND
REGIONAL VARIATION IN SNOWMOBILE EMISSIONS
Percentage of Total Emissions by Season
Region Dec-Feb Mar-May Jun-Aug Sep-Nov Subtotals
Northern 55.8 18.6 0.0 18.6 93.0
Central 7.0 0.0 0.0 0.0 7.0
Southern 0. 0 0.0 0.0 0.0 0.0
Subtotals 62.8 18.6 0.0 18.6 100.0
area between 49° and 43° North latitude, the central region is between
43° and 37°, and the southern region is between 37° and 31°. The
basic breakdown comes from assuming a 5-month snow season in the
northern region, a 3-month season in the central, and no season in the
southern region. The other major variable considered is geographic
distribution of snowmobiles (by states), according to data from Table 23.
It was assumed that most snowmobiling is done in the state and region in
which the machine is registered, but operation was assumed to be in
another state or region where such an occurrence seemed obvious. One
example would be New York state, which is placed in the central region
by its population center, but in which most snowmobile operation is pro-
bably in the northern half (or in the northern region as defined here).
Grass racing and other summer activities have not been considered.
Regarding concurrence with emissions released by other sources,
snowmobiles probably emit only very small amounts in most urban areas
or during peak traffic hours. In these respects, snowmobile emissions
can hardly be considered additive to other emissions in estimating con-
tributions to most urban air pollution episodes.
53
-------
VI. SUMMARY
This report is the end product of a study on exhaust emissions
from snowmobile engines, and it is Part 7 of a seven-part final report
on "Exhaust Emissions from Uncontrolled Vehicles and Related Equip-
ment Using Internal Combustion Engines, " Contract EHS 70-108. It
includes test data, documentation, and discussion on detailed emissions
characterization of four engines (three 2-stroke twins and one rotary),
as \vell as estimated emission factors and national emissions impact.
As a part of the final report on the characterization phase of EHS 70-108,
this report does not include information on aircraft turbine emissions,
outboard motor crankcase drainage, or locomotive emissions control
technology. As required by the contract, these three latter areas have
been or will be reported on separately.
The emission measurements on the four snowmobile engines were
conducted in,and by the staff of,the Emissions Research Laboratory. Data
were acquired daring steady-state "mapping" procedures, which included
idle conditions and 28 other speed/load combinations, not all of which
were the same for any two engines.
The exhaust products measured included total hydrocarbons by
FIA; CO, CO2, NO, and hydrocarbons by NDIR; NO and NOX by chemi-
luminescence; Q£ by electrochemical analysis; light hydrocarbons by
gas chromatograph; aldehydes by wet chemistry; particulates by gravi-
metric analysis; and smoke by the PHS light extinction smokemeter.
The engines were operated with (nominal) 20° F intake air, fuel losses
by evaporation (in the field) were considered negligible, and SO emis-
sions were calculated rather than being measured. Emission factors
and national impact were computed for hydrocarbons (total'), CO, NO ,
RCHO (aldehydes), particulate, and SOX.
Expressing snowmobile engine emissions as percentages of re-
vised 1970 national totals from all sources, snowmobiles appear to
account for approximately 0. 2 percent of hydrocarbons, 0. 1 percent of
CO, 0. 004 percent of NOX, 0. 008 percent of particulate, and 0. 0003 per-
cent of SOX. As percentages of revised 1970 mobile source emissions,
snowmobiles are estimated to account for about 0.4 percent of hydrocar-
bons, 0. 1 percent of CO, 0. 009 percent of NOjj, 0. 3 percent of particulate,
and 0. 009 percent of SOX. All these figures are rather minimal on a
national basis.
Since emissions from snowmobiles occur mainly in a few states
and during a few months of the year, their local impact may be more
severe in some cases than indicated by national comparisons. Particular
instances may arise, for example, in which a number of machines are
54
-------
operated in a relatively small area; and this situation could lead to un-
desirable HC and CO levels. It should also be noted, however, that
snowmobile emissions, being released primarily in suburban/rural areas
and during leisure hours, should not be frequent contributors to air
pollution episodes associated with highway vehicles or industrial processes.
An estimate of seasonal and regional variation in snowmobile emissions
shows that about 93% of such emissions occur in the northern region and
7% in the central region. About 63% of snowmobile emissions occur in the
Dec. -Feb. quarter, and around 19% each in the late fall and early spring.
After a number of years of very rapid growth, the snowmobile mar-
ket seems to be leveling off. This factor leads to a slowly increasing snow-
mobile population projected for the near future, with most sales as replace-
ment rather than expansion of the population. It is not expected that drastic
changes in snowmobile emissions will occur on a national basis due to any
forseeable factor, but fuel shortages or rationing could change the whole
picture.
55
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LIST OF REFERENCES
1. "The Snowmobile Owner 1972, " Snow Goer Trade magazine, August
1972, Webb Publishing Company, St. Paul, Minnesota.
2. Federal Register, Volume 38, No. 124, Part III, June 28, 1973;
Section 85. 074-10(a).
3. Altshuller, A. P., et al, Determination of Formaldehyde in Gas
Mixtures by the Chromotropic Acid Method, Anal. Chem. 33:621,
1961.
4. Sawicki, E. , et al, The 3-Methyl-3-benzathiazalone Hydrazone
Test, Anal, Chem. 33:93, 1961.
5. Federal Register, Volume 37, No. 221, Part II, November 15, 1972;
Section 85. 874-13.
6. Federal Register, Volume 38, No. 124, Part III, June 28, 1973;
Section 85. 074-26(d).
7. Federal Register, Volume 37, No. 221, Part II, November 15, 1972;
Section 85. 774-18(1).
8. Hare, Charles T. and Springer, Karl J., "Exhaust Emissions from
Uncontrolled Vehicles and Related Equipment Using Internal Com-
bustion Engines, " Final Report Part 3,Motorcycles, Contract No.
EHS 70-108, March 1973.
9. Hare, Charles T. and Springer; Karl J., "Exhaust Emissions
from Uncontrolled Vehicles and Related Equipment Using In-
ternal Combustion Engines, " Final Report Part 4,Small Air-
Cooled Spark Ignition Utility Engines, Contract No. EHS 70-108,
May 1973.
10. Hare, Charles T. and Springer, KarlJ., "Exhaust Emissions
from Uncontrolled Vehicles and Related Equipment Using In-
ternal Combustion Engines, " Final Report Part 1,Locomotive
Diesel Engines and Marine Counterparts, Contract No. EHS 70-108,
October 1972.
11. Hare, Charles T. and Springer, KarlJ., "Exhaust Emissions
from Uncontrolled Vehicles and Related Equipment Using In-
ternal Combustion Engines, " (currently) Draft Final Report Part
5,Heavy-Duty Farm, Construction, and Industrial Engines, Con-
tract No. EHS 70-108, July 1973.
56
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LIST OF REFERENCES (Cont'd)
12. Hare, Charles T. and Springer, KarlJ., "Small Engine Emissions
and Their Impact, " SAE Paper No. 730859, Presented at the
Society of Automotive Engineers Meeting in Milwaukee, Wisconsin,
September 10-13, 1973.
13. Eccleston, B. H. and Hum, R. W. , "Exhaust Emissions from Small,
Utility, Internal Combustion Engines, " SAE Paper No. 720197, Pre-
sented at the Society of Automotive Engineers Congress in Detroit,
Michigan, January 1972.
14. Donahue, J. A., et al, "Small Engine Exhaust Emissions and Air
Quality in the United States, " SAE Paper No. 720198, Presented
at the Society of Automotive Engineers Congress in Detroit, Michigan,
January 1972.
1 5. Optical Properties and Visual Effects of Smoke-Stack Plumes, A
Cooperative Study: Edison Electric Institute and U.S. Public Health
Service, Publication No. 999-AP-30, Cincinnati, Ohio, 1967.
16. Halow, John S. and Zeek, Susan J. , "Predicting Ringelmann Number
and Optical Characteristics of Plumes, " Journal of the Air Pollution
Control Association, Volume 23, No. 8, August 1973.
17. Letter from Mr. L. W. Foster of Polaris to C. T. Hare, March
16, 1973.
18. Letter from Mr. Joe Budd of John Deere to C. T. Hare, October
4, 1972.
19. Letter from Mr. J. H. Rose of Massey-Ferguson to John Nesbitt
of ISIA, April 6, 1973, Submitted to C. T. Hare by Mr. Nesbitt.
20. Ward, Harry M. , Griffith, Michael J., Miller, George E. , and
Stephenson, Donald K. , "Outboard Marine Corp.'s Production
Rotary Combustion Snowmobile Engine," SAE Paper No. 730119,
Presented at the Society of Automotive Engineers Congress in
Detroit, Michigan, January 8-12, 1973.
21. Letter from Mr. Harvey E. Schultz of Kohler Company to B. C.
Dial of SwRI.
22. Letter and Enclosures from Mr. Martin A. Berk of John Deere to
C. T. Hare, August 31, 1973.
57
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LIST OF REFERENCES (Cont'd)
23. Petroleum Products Survey No. 73, U.S. Department of the Interior,
Bureau of Mines, January 1972.
24. Letter from Mr. John Nesbitt of ISIA to C. T. Hare, July 13, 1973.
25. The Off-Road Vehicle and Environmental Quality, Malcolm F. Bald-
win, The Conservation Foundation, Washington, D. C. , 1970.
26. Product News, May/June 1973 (Submitted by John Nesbitt of ISIA).
27. 1970 EPA Air Pollutant Inventory Estimates (Revised), 1973 Annual
Report of the Council on Environmental Quality.
58
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APPENDIX
A-l
-------
Mode
rpm
Obs.
Power,
Fuel,
lbm/hr
Temp. , °F
Int. I Exh.
FIA
HC,
ppmC
NDIR
HC,
NDIR
CO,
NDIR
C02
NDIR
NO,
ppm
C. L.
NO,
pprn
C.L.
NOX,
ppm
Elect.
1
1 OLE
I.TI
15-
4.3g
Ji.
- fa
2.20
30?
73.
39.6
\310
/ 2.3k
0.13
f6-3
SSOO
iS"
5-20
14/00
D.ll
9S-./
/o/.
3.4.
/2.-S
2.3
628
3-104
7-1 /
6(0.0
8^-4
IS-
ZSkoo
3-
l.ns'
2-44-
4.3
BS30
' i,A
l&.
41? o&o
/
3-2-4
2-1
0.II
8.C?
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-------
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1
2
3
4
5
6
7
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9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
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-------
Mode
1
2
3
4
5
6
7
8
9
10
11
12.
13
14
15
16
17
18
19
20
' 21
22
23
24
25
26
27
28
29
30
31
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-------
Mode
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
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1
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3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
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1
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3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
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-------
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1
2
3
4
6
7
8
9
10
11
12
13
14
15
16
18
19
20
21
22
23
24
25
26
27
28
29
30
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12
13
14
15
16
17
18
19
20
21
22
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16
17
18
19
20
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-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO
APTD-1496
3. RECIPIENT'S ACCESSI Or* NO.
4. TITLE AND SUBTITLE
Exhaust Emissions from Uncontrolled Vehicles and
Related Equipment Using Internal Combustion Engines
Part 7: Snowmobiles
5. REPORT DATE
April 1974
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Charles T. Hare and Karl J. Springer
8. PERFORMING ORGANIZATION REPORT NO
AR-946
9. PERFORMING ORG'NNIZATION NAME AND ADDRESS
Southwest Research Institute
Vehicle Emissions Research Laboratory
8500 Culebra Road
San Antonio, Texas 78284
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EHS 70-108
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
2565 Plymouth Road
Ann Arbor, Michigan 48105
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report includes test data, documentation, and discussion on detailed exhaust
emission characterization of four snowmobile engines (three two-stroke cycle and one
rotary combustion cycle). It also covers the estimation of emission factors and
national air quality impact. Broad regional and seasonal estimates of the distribu-
tion of these emissions are also made.
The exhaust products measured include HC, CO, C02, NO, 02, light hydrocarbons,
aldehydes, particulate, and smoke; SOX emissions were calculated rather than measured.
The engines were operated with steady-state "mapping" procedures using 20°F intake
air.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group
3. DISTRIBUTION STATEMENT
Unlimi ted
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
M. NO. OF PAGES
22. PRICE
EPA Form 2220-1 (9-73)
A-21
------- |