73-18
LOW AMBIENT TEMPERATURE
EMISSION TESTING, A
PRELIMINARY REPORT
February 1973
R. Bruce Michael
Test and Evaluation Branch
Environmental Protection Agency
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Background
This is a report on the first part of a program to characterize
exhaust emissions at low temperatures. The testing accomplished
thus far was done on two pre-1968 and three post-1968 vehicles.
It was desirable to determine if any basic differences in per-
formance at low ambient temperatures existed between controlled
and pre-controlled vehicles.
Test Program
The vehicles tested consisted of the following. All were
equipped with automatic transmissions:
1962 Chevrolet 283 CID 8 cylinder
1963 Ford 289 CID 8 cylinder
1970 Valiant 225 CID 6 cylinder
1970 Chevrolet 350 CID 8 cylinder
1971 Ford 351 CID 8 cylinder
The vehicles were tested using a Clayton dynamometer according
to the 1975 Federal Test Procedure, except for changes in ambient
temperature. The vehicles were each tested twice at the
following ambient temperatures: 68-86°F (baseline), 60°F, 59°F,
and 40°F. The 60° and 50°F tests were achieved simply by
changing the thermostat setting in the test cell. The 40°F
temperature was achieved by opening the outside doors slightly
and drawing into the cell the outside cold air by means of a fan.
This method was not precise because the rear of the cell near the
doors was necessarily 30°F to achieve a temperature of 40°F at
the front of the vehicle, and it was not possible to have a
steady temperature for vehicle soak because of normal changes
in atmospheric temperature. Soak temperatures varied by as much
as 5° during the twelve hour period, but for about four hours
before the test, and during the test, the cell temperature was
within two degrees of the nominal 40°F test temperature. Temp-
eratures of the air being blown into the engine, engine water
and air going into the carburetor were continuously recorded
throughout the emission testing.
Test Results
The test data and calculations are presented in the Appendix of
this report. Carbon monoxide and hydrocarbon emissions tended
to increase at the lower temperatures (except in the unexpected
case of the 1962 Chevrolet CO emissions at 40°). At 40° one of
the older vehicles had 29% more CO than baseline and the other
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had 59% less, for an average of 17% less than baseline, while
all the newer vehicles increased greatly at 40° to an average
of 75% greater than baseline. Oxides of nitrogen emissions on
the uncontrolled vehicles stayed about the same while on the
controyled cars NOx slightly decreased at the lower temperatures.
Carbon dioxide emissions varied insignificantly with no dis-
cernable trend.
Conclusions
Compared to their baseline tests at 68-S6°F, post-1968 controlled
vehicles show a relatively greater increase in carbon monoxide [
emissions as temperature is reduced than was evident for the [
pre-controlled vehicles. This trend, however, is predicted based [.
on very limited data.
ffi
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APPENDIX
TABLE I
Average Emission Levels
(all results in grams per mile)
2 pre-1968 vehicles (avg.)
HC
CO
NOx
Baseline
6.17
90.2
4.50
60°
7.66
98.6
4.38
50°
7.20
40°
8.23
94.1 74.4
4.65 4.28
3 post-1968 vehicles (avg.)
Baseline
HC 2.28
CO 21.6
NOx
6.14
60° 50° 40°
2.48 2.79 3.13
27.8 31.4 37.8
5.82 5.49 5.65
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BLE II
Percent .,:e from Baseline (68°-86°F)
60°
50°
40°
60°
50°
40°
60°
50°
40°
HC
eT968
+ 24
+ 17
+ 33
CO
re-1968
+ 9
+ 4
-17 •
NOx
're-1968
-3
+ 3
-5
Post-196
+ 9
+ 22
+ 37
Post-196
+ 29
+ 45
+ 75 - -.
Post-196
-5
-11
-8
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TABLE III
Individual Vehicle Emission Data
(all results in grams per mile)
Each figure is the average of tv,ro tests
1962 Chevrolet EPA 157
HC
Baseline
60°
50°
40°
1963 Ford EPA 155
Baseline
60°
50°
40°
1970 Valiant EPA 158
Baseline
60°
50°
40°
1971 Ford EPA 161
Baseline
60°
50°
40°
1970 Chevrolet EPA 160
Baseline
60°
50°
40°
5.50
6.97
6.39
8.20
HC
6. 84
8.36
8.02
8.26
HC
1.85
2.44
3.27
3.83
HC
2.71
2.79
2.69
3.43
HC
2.27
2.27
2.41
2.12
CO
CO
21.2
29.4
35.6
45.1
CO
18.9
25.5
26.3
35.9
CO
24.8
28.6
32.3
32.38
CO,
C02
458
456
445
453
C02
725
747
698
718
co2
732
770
731
736
NOx
94.8
100.9
89.4
38.7
599
625
625
632
4.43
3.99
4.26
4.49
CO
85. 7
96.4
98.8
110.2
C02
564
606
610
575
NOx
4.58
4.77
5.05
4,06
NOx
7.38
6.29
5.61
6.67
NOx
5.39
5.43
5.42
5.12
NOx
5.66
5.73
5.44
5.16
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