71-27
A Report on the Exhaust Emissions of the
1971 Production Version of the Army M-^151 Jeep
April 1971
John C. Thomson
Bureau of Mobile Source Pollution Control
Office of Air Programs
ENVIRONMENTAL PROTECTION AGENCY
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71-27
A Report on the Exhaust Emissions of the
1971 Production Version of the Army M-151 Jeep
April 1971
John C. Thomson
Bureau of Mobile Source Pollution Control
Office of Air Programs
ENVIRONMENTAL PROTECTION AGENCY
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Vehicles Tested
As part of a continuous evaluation program of vehicles for
the U. S. Army Tank-Automotive Command, two new Army M-151's
were evaluated according to the 1972 Federal emission test
procedure. The vehicles tested were built during the start
of production in 1971 and had fewer than 60 miles when
received. This is the standard Army "Jeep" with provisions
for two or four wheel drive, a four speed manual transmission
and a four cylinder engine. The engine is an Army designed
overhead valve four cylinder, displacing 141 cubic inches.
The engine is designed to be operated over a wide range of
temperatures and grades and has provisions for underwater
operation up to five feet. For fording purposes, all vents
from the engine, and fuel tank dump into the oil bath air
cleaner, the fuel tank is vented to atmosphere in normal
operation.
Tests Performed
All tests reported in Table 1 were run using the 1972 Federal
emission test procedure. This is a 23 minute non-repetitive
driving schedule (LA 4-S4) run on a chassis dynamometer.
Exhaust emissions are collected using a constant volume
sampler (CVS) with a portion of the dilute exhaust bagged
for analysis. The analysis system measures unburned hydro-
carbons (HC) using a flame ionization detector (FID) while
carbon monoxide (CO) and carbon dioxide (C02) are measured
with non-dispersive infrared analyzers (NDIR). Two systems
were used for measuring oxides of nitrogen with results
reported by both chemiluminescence (CI) and modified Saltz-
man (Saltz). All NOX results are converted to N02 and
corrected for humidity. All of the results are reported in
grams per mile.
In addition to the exhaust emission tests, evaporative
emission losses were measured. In these tests an activated
charcoal filter is connected to the fuel tank and any other
potential source of fuel loss during a hot soak. The
procedure is spelled out in the Federal Register dated
November 10, 1970. The test requires a conditioning prior
to the soak and also heating of the fuel tank.
Results
Emission tests results are reported in Table 1. The vehicle
average hydrocarbons of 4.9 and 5.8 are considerably above
the 1972 Federal standard of 3.4 grams per mile (gpm). The
carbon monoxide values of more than 100 gpm are almost three
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times the standard of 39 gpm. These cars show values that
are typical of the uncontrolled cars that were built prior
to 1966.
In Table 2, results from the evaporative emission tests are
reported. The standard is presently 2.0 grams. The standard
is being met by one of the vehicles but not the other.
Additional evaluations using an enclosed shed are planned
to check these results.
The emission results found during this test essentially
duplicated levels found on previous M-151's tested by this
laboratory.
Conclusions
1. The emission levels of the M-151 are quite high when
compared to controlled production automobiles and
trucks.
2. The emission levels of the M-151 compare with the
uncontrolled car population produced prior to 1966.
3. Evaporative emission levels appear to be higher than the
current standards.
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Table 1
1972 Federal Emission Test (LA-4)
All Numbers in Grams Per Mile
HC CO CO2
FID NDIR NDIR
Vehicle No. 02LJ7871
NOX
Saltz
NOX
CI
Average
5.0 .
5.5
3.9
7.5
4.4
5.0
3.2
150+
128
101
150+
110
109
87
420
420
444
410
478
445
318
1.3
2.0
1.4
2.4
2.3
1.3
0.6
1.9
2.1
1.2
2.1
2.1
1.3
4.9
119+
419
1.8
1.6
Vehicle No. 02LK2771
6.2
4.8
7.3
5.0
5.9
103
115
137
103
102
387
456
440
355
381
1.8
2.0
2.1
1.8
2.3
1.8
3.0
2.3
1.6
1. 8
Average
5.8
112
404
2.0
2.1
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Table 2
Canister Evaporative Emission Test
All Results in grams
Carburetor
Fuel Tank
Total
Average
Vehicle no. 02LJ7871
0 4.32
0 2.35
0 0.6
0 1.99
0 2.30
0 2.67
2.37
Vehicle no. 02LK2771
0
0
0
1.97
0.55
1.97
0.55
1.88
Average
1.47
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