77-15 FPH
The Effects of Manual Transmission Shift Points
on Emissions and Fuel Economy of a 1977 Chevrolet
Chevette When Tested by the Hot LA-4 Procedure
December 1977
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
U.S. Environmental Protection Agency
Prepared by: F. Peter Hutchins
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Background
The Environmental Protection Agency is presently conducting studies
which are directed to identifying differences in fuel economy as measured
on the FTP test and reported in the Mileage Guide compared to in-use
vehicle measurement. One of these studies is directed to the identi-
fication of differences in the fuel economy performance of production
vehicles relative to the counterpart certification vehicle. A brief
study of the effects on emissions and fuel economy of variations in
manual transmission shift points was conducted on one of these production
vehicles.
The results of this transmission shift point study are contained in this
report. The conclusions from these tests can be considered to be quan-
titatively valid only for the specific type of vehicle used in the
study, although it is reasonable to extrapolate the results to other
types of vehicles in a directional or qualitative manner.
Test Vehicle
The vehicle used in this study was a production, 1977 Chevrolet Chevette,
equipped with the 1.6 litre engine, 4-speed manual transmission, standard
rear axle and original equipment tires. A detailed description of the
vehicle is given in the Appendix.
Test Program
Duplicate hot LA-4 tests were performed for each transmission shift
point sequence which was under study. Every precaution was taken to
minimize the effects of such testing variables as; 1) the driver 2)
changes in barometric pressure, humidity, dynamometer performance and
instrumentation, and 3) changes in the vehicle during the time of test-
ing. Control of the first two types of variables was accomplished by
performing all tests with the same driver, on the same dynamometer using
the same analytical equipment during one day of testing. Changes, if
any, in the vehicle were accounted for by performing the tests in the
following sequence:
Test Number Transmission Shift Sequence
1 General Motors shift point procedure (GM)
2 Previously standard EPA shift point procedure (EPA)
3 Torque peak bracketing shift point procedure (TPB)
4 General Motors shift point procedure (GM)
5 Previously standard EPA shift point procedure (EPA)
6 Torque peak bracketing shift point procedure (RPB)
The modal analyzer was used to facilitate a detailed evaluation of the
effects on emissions and fuel economy of the three shift point procedures.
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Transmission Shift Sequences Which Were Investigated
1. The General Motors procedure which appears to ensure that, at any
given point on the driving cycle, the vehicle is always in the
highest gear which, with the use of wide open throttle, permits the
vehicle to just follow the driving trace. The result of this
approach is that there is a random appearance to the shift points
when compared to vehicle speed (Figure l(a)). This procedure also
results in the lowest engine rotational speeds in the lower trans-
mission gears of the three procedures.
2. The previously standard EPA procedure specifies the following
manual transmission shift points for all vehicles: 1st to 2nd @ 15
MPH; 2nd to 3rd @ 25 MPH and 3rd to 4th @ 40 MPH (Figure l(b)).
3. The torque peak bracketing procedure is based on exercising the
engine in such a fashion as to include the peak torque rpm within
the operating range of each gear. The vehicle speed at which each
gear change occurs is a function of both the overall gearing of the
vehicle (N/V in highest gear), the gear ratios of the lower gears,
the peak torque rpm of the engine and the idle rpm of the engine.
The transmission shift points which were selected for the test
vehicle using this procedure are as follows: 1st to 2nd @ 17.5 MPH;
2nd to 3rd @ 28 MPH and 3rd to 4th @ 40 MPH (Figure l(c)). This
procedure results in the highest engine rotational speeds in the
lower transmission gears of the three procedures.
Test Results
Table 1 summarizes the vehicle exhaust emissions and fuel economy for
the three transmission shift point procedures as determined by the hot
LA-4 test. This table shows that, of the three manual transmission
shift point procedures which were investigated on the hot LA-4 test,
the General Motors shift point procedure produced the lowest HC and
CO emissions, the highest fuel economy and the highest NOx emissions.
Table II shows the average acceleration mode emissions from each pair
of tests for each cycle of the LA-4 as determined by the modal analyzer.
Table III is similar to Table II but shows the average cruise mode
emissions.
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(a) GENERAL MOTORS PROCEDURE
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Both of these tables clearly show the modal superiority of the GM
procedure in controlling HC and CO emissions while causing an increase
in NOx emissions.
Table IV shows the average idle, acceleration, cruise and deceleration
mode emissions for each pair of tests for the LA-4. Of note is the
continued benefit in HC and CO emissions even at idle and during
deceleration of the GM procedure.
Table 1
Hot LA-4 Mass Emissions in Grams/Mile
and Fuel Economy in Miles/Gallon
Shift Point Procedure
General Motors Previously Torque Peak
Standard EPA Bracketing
Hydrocarbon
Test 1 0.20
Test 2 0.21
MEAN 0.21
Carbon Monoxide
Test 1 2.54 3.87 4.80
Test 2 2.98 4.01 4.88
MEAN 2.76 3.94 4.84
Oxides of Nitrogen
Test 1
Test 2
MEAN
Fuel Economy
Test 1 29.65 26.81 25.07
Test 2 29.61 26.78 25.10
Mean 29.63 26.80 25.09
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Table II
Acceleration Mode Mass Emissions in Grams/Mile by Cycle
as a Function of Shift Point Procedure
Cycle
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
HC Emissions
Shift Point Procedure
GM
.064
.211
.068
.055
.079
.012
.015
.020
.017
.025
.049
.048
.055
.015
.039
.019
.036
.015
EPA
.087
.383
.123
.132
.132
.041
.006*
.032
.024
.046
.063
.055
.054*
.042
.052
.050
.075
.024
TPB
.107
.385
.141
.101
.197
.042
.007*
.095
.034
.084
.072
.057
.113
.068
.053
.049
.073
.062
CO Emissions
NOx Emissions
Shift Point Procedure
GM
.738
2.563
1.355
1.428
1.761
.231
.502
.375
.395
.566
1.421
1.273
1.190
.216
.836
.346
.754
.233
EPA
1.116
4.560
2.077
2.061
1.829
.687
.125*
.697
.557
1.108
1.582
1.229
1.136
.945
.701*
.913
1.121
.493
TPB
1.453
4.404
2.048
1.514
2.570
.853
.126*
1.287
1.017
1.592
1.924
1.641
2.072
1.182
1.115
1.036
1.242
1.185
Shift
GM
067
737
307
121
267
"166
054
146
195
176
112
098
156
200
054
178
149
139
Point Procedure
EPA
.088
.626*
.291*
.188
.280
.161*
.052*
.147
.169*
.195
.150
.154
.207
.129*
.066
.136*
.164
.084*
TPB
.073
.535*
.287*
.252
.304
.160*
.033*
.138*
.141*
.169*
.150
.193
.114*
.191*
.090
.156*
.194
.094*
*Cycle/pollutant where the previously standard EPA and/or
Torque Peak Bracketing shift point procedures resulted in
lower emissions than the GM procedure.
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Table III
Cruise Mode Mass Emissions in Grams/Mile by Cycle
as a Function of Shift Point Procedure
HC Emissions
CO Emissions
NOx Emissions
1
2
3
4
5
6
7
g
9
10
11
12
13
14
15
16
17
18
Shift Point Procedure
Shift Point Procedure
Shift Point Procedure
GM
EPA
TPB
GM
EPA
TPB
GM
EPA
TPB
.187
.148
.008
.015
.004
.018
.235
.159
.011
.013*
.005
.015*
.294
.123*
.012
.018
.007
.012*
.999
.563
.028
.207
.007
.195
1.334
1.038
.015*
.035*
.022
.182*
2.843
.941
.136
.088*
.024
.169*
.703
2.265
.237
.390
.161
.246
.663*
2.127*
.190*
.281*
.137*
.260
.540*
2.032*
.161*
.299*
.089*
.249
.050
.025
_
.009
_
.007
.013
.085
.022*
_
.009
_
.022
.027
.059
.013*
_
.011
_
.035
.016
.191
.415
_
.063
_
.008
.046
1.049
.350*
_
.091
_
.145
.328
.715
.203*
_
.063
_
^36JB
.094
1.873
.378
_
.309
_
.096
.319
1.508*
.294*
_
.230*
_
.111
.177*
1.479*
.334*
.128*
.118
.133*
*Cycle/pollutant where the previously standard EPA and/or
Torque Peak Bracketing shift point procedures resulted in
lower emissions than the GM procedure.
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Table IV
Total LA-4 Modal Emissions, in Grains
HC Emissions CO Emissions NOx Emissions
Shift Point Procedure Shift Point Procedure Shift Point Procedure
Mode GM EPA TPB GM EPA TPB GM EPA TPB
Idle .107* .113 .120 .125* .729 .696 .251* .298 .311
Accel .840* 1.371 1.738 16.182* 22.980 28.250 3.321 3.298 3.274
Cruise .485* .602 .602 2.722* 4.589 5.643 6.978 5.977 5.561
Decel .117* .142 .170 1.154* 1.280 1.672 .845 .690 .680
*Modes/pollutants where the GM shift point
procedure resulted in lower emissions than
the other shift point procedures under study.
Comparative Summary of Results
1) The overall percentile change as measured by the Hot LA-4 test on
exhaust emissions and fuel economy of the two alternative shift
point procedures relative to the General Motors shift point pro-
cedure are summarized in Table V.
Table V
Percentage Change in Emissions and Fuel Economy Relative
to the General Motors Manual Transmission Shift Point Procedure
Transmission Emissions
Shift Point Procedure HC CO NOx Fuel Economy
Previously
Standard EPA 42.9% 42.8% -9.9%* -9.6%*
Torque Peak
Bracketing Procedure 66.7% 75.4% -13.8% -15.3%
*A negative result means a reduction in either emissions
or fuel economy relative to the General Motors Shift Point Procedure.
2) The percentile change, by mode, as measured by the Hot LA-4 test
on exhaust emissions of the two alternative shift point procedures
relative to the General Motors shift point procedure are summarized
in Table VI.
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Table VI
Percentage Change in Modal Emissions Relative to the
General Motors Manual Transmission Shift Point Procedure
Transmission Modes
Shift Point Idle Accel. Cruise Decel.
Procedure HC CO NOx HC C0_ NOx HC CO NOx HC CO NOx
Previously
Standard EPA 5.6% 483.2% 18.7% 68.2% 42.0% -0.7%* 24.1% 68.6% -14.4%* 21.4% 10.9% -8.3%*
Torque Peak
Bracketing 12.2% 456.8% 23.9% 106.9% 74.6% -1.4%* 24.1% 107.3% -20.3%* 45.3% 44.9% -19.5%*
*A negative result means a reduction in
emissions relative to the General Motors
Shift Point Procedure.
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Conclusions
1. The transmission shift points selected by General Motors resulted
in significantly better fuel economy on the Hot LA-4 test than was
obtained by the other shift point procedures.
2. The transmission shift points selected by General Motors and used
in the certification process resulted in significantly lower hydro-
carbon and carbon monoxide emissions when compared to the other
shift point procedures. The General Motors shift points caused
higher NOx emissions than the other two procedures.
3. The use of higher speed shift points by the public than those used
by General Motors during the vehicle certification process can
result in lower than expected fuel economy.
4. On the road Hydrocarbon and Carbon Monoxide emissions can be much
higher than the certification values if other than the certification
manual transmission shift points are used by the public.
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Appendix
Test Vehicle Description
Model Year/Make - 1977 Chevrolet Chevette
VIN - 1B08E7Y155084
Emission Control System - EM/EGR/CAT
Engine
Type 4 stroke, Otto Cycle, 4 cyl., ohc
Bore x stroke 82 mm (3.23 in) x 75.7 mm (2.98 in)
Displacement 1.6 litre (97.6 cu. in.)
Compression ratio 8.5:1
Maximum power @ rpm ... 63 HP 2 4800 RPM
Maximum torque @ rpm .. 82 ft Ib. @ 3200 RPM
Fuel metering Single, 1 barrel carburetor
Fuel requirement Unleaded regular
Drive Train
Transmission type 4 speed manual
Gear ratios 1st - 3.75:1; 2nd - 2.16:1; 3rd - 1.36:1; 4th - 1.0:1
Final drive ratio 3.7:1
Chassis
Type Unitlzed
Tire size P 155/80 R 13
Curb weight 2020 Ib.
Inertia weight 2250 Ib.
Passenger capacity .... 4
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