73-18
    LOW AMBIENT TEMPERATURE
     EMISSION TESTING, A
     PRELIMINARY REPORT
         February 1973
       R.  Bruce Michael
  Test and Evaluation Branch
Environmental Protection Agency

-------
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

-------
                             -2-
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

-------
                         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

-------
                     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

-------
                         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

-------