EPA-AA-SDSB-80-3
Technical Report
The Effect of Acceleration Rate on Automatic
Transmission Shift-Speeds for Two 1979 Novas
By
Randy Jones
January 1980
NOTICE
Technical Reports do not necessarily represent final EPA decisions
or positions. They are intended to present technical analysis of
issues using data which are currently available. The purpose in
the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical devel-
opments which may form the basis for a final EPA decision, position
or regulatory action.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, Noise and Radiation
U.S. Environmental Protection Agency
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I. Introduction
The Federal Test Procedure and the Highway Fuel Economy
Test are currently used by EPA to measure emissions and fuel
economy. The driving cycles used for these tests simulate the
experience of a vehicle on an average urban excursion and during
typical highway travel. However, during the development of the
driving cycles the maximum acceleration rate was limited to 3.3
mph/sec, because of performance limitations of the twin roll
dynamometers available at the time.I/
Variations in acceleration rates will result in variations in
vehicle fuel economy. If typical vehicle acceleration rates are
distributed in the same manner as the accelerations are distributed
on the EPA test cycles, or if the vehicle operational character-
istics do not significantly change with acceleration rate, then
results from the EPA cycles should be representative of average
vehicle use. However, if vehicle operational characteristcs change
with changing acceleration rates, and if vehicle accelerations in
consumer use are not distributed in the same manner as the accel-
erations of the EPA test cycle, then significant differences
between EPA estimated fuel economy and actual vehicle fuel consump-
tion may result. This effect would be most dramatic if the vehicle
operational characteristics significantly change when acceleration
rates exceed 3.3 mph/sec.
One important vehicle characteristic which often changes
with acceleration rate is the transmission shift speed for vehicles
with automatic transmissions. Consequently, to determine the
effects of acceleration rates on transmission shift speeds and to
determine if any anomalous change occurs in transmission shift
speeds at acceleration rates near 3.3 mph/sec., EPA recently
conducted a short test sequence on two vehicles with automatic
transmissions. These tests determined the relation between vehicle
acceleration rate and transmission shift speed for acceleration
rates from 1 to 6 mph/sec. The vehicles, the test sequence, and
the results are discussed in detail in the following sections of
the report.
II. Discussion
A. Test Equipment and Test Site
The test vehicles were two 1979 Chevrolet Novas; similar in
model, equipment, and accumulated mileage. Each vehicle was
equipped with a three-speed automatic transmission. A detailed
vehicle description is given in Appendix A.
To assure consistent operation of the vehicles, a "drivers
aid" strip chart recorder was installed in each. This "drivers aid"
was a feedback system which provided a continuous chart trace of
vehicle speed. The speed was sensed by a fifth wheel mounted on
the rear of the vehicle.
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The tests were conducted at the Transportation Research Center
of Ohio. The test site used for data collection was the straight,
smooth, north-south section of high speed oval track.
B. Procedure
Prior to conducting the tests, speed time lines representing
constant acceleration rates from 0 to 60 mph were drawn on the
"drivers aid" strip chart. The acceleration rates of the speed
time lines varied from one to six mph/sec. in increments of one
mph/sec.
The vehicles were first driven over a warm-up cycle consisting
of steady-speed operation at 55 mph for about 22.5 miles. The
vehicles were operated at all times with a driver and observer on
board.
In each test trial the driver matched, as accurately as
possible, the vehicle speed, as indicated on the "driver's aid"
system, to the constant acceleration speed-time lines previously
drawn on the strip chart paper. Each trial began with the vehicle
at rest and the transmission selector in the "drive" position. The
observer noted on the strip chart trace the transmission gear shift
points, judged by sound and sensed movement of the vehicle. Five
trials were conducted in each direction at each rate of accelera-
tion.
An example strip chart recording for two test trials of
Vehicle B is given in Figure I. The speed time lines represent
constant acceleration rates of 2 mph/sec. The vehicle speed trace
follows each acceleration trace closly. The X's denote the lst-2nd
and 2nd-3rd gear transmission shift speeds of the vehicle.
The speed at each transmission shift point was later read from
the strip chart for all test trials. All transmission shift speed
data are tabulated in Appendix B.
C. Results
Each vehicle experienced an increase in lst-2nd and 2nd-3rd
gear shift speeds with an increase in acceleration rate. The
average shift speed for each five-trial test sequence was computed
and tabulated in Table I.
Graphical representations (Figures II and III) indicate that
for each vehicle the relation between lst-2nd gear transmission
shift speed and acceleration rate was approximately linear in two
distinct regions; acceleration rates from 1-3 mph/sec and accel-
eration rates from 4-6 mph/sec. A distinct change in slope of the
linear relation occurred between acceleration rates of 3 mph/sec
and 4 mph/sec. Vehicle A experienced a significantly greater delay
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Table 1
Five Trial Average Vehicle Shift Speed for
Each Acceleration Rate
Acceleration
Rate
1 mph/sec
2 mph/sec
3 mph/sec
4 mph/sec
5 mph/sec
6 mph/sec
Direction
of Test
North
South
North
South
North
South
North
South
North
South
North
South
lst-2nd
Vehicle B
11.5
11.6
19.8
18.8
28.4
25.6
33.4
34.0
37.4
37.0
40.6
41.6
Average
gear
Vehicle A
13.4
13.0
18.6
17.8
25.2
24.0
40.4
40.4
44.0
43.8
43.8
43.8
Shift Speed
2nd-
Vehicle B
24.8
19.0
45.0
42.8
58.0
58.4
—
—
—
Vehicle A
22.6
23.8
50.0
43.4
60 +
60 +
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Figure I
Vehicle B; Speed-Time Trace
• ; l_J-.i_.-_L ._
_.. i ' •—• r-; -- - ~ ' . f"~"' 'r
_.: 4 •. bt...,...- . i '
-.._.. .
i ~: •.;_ _L ~"r'*lll"_:ilL'J.
••:-.. .-:-! .:.".-'.."" Li". •'.".!_:. L~._. __i.."."" .
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60,
-6-
/"-—*
Figure II ~~"~~
Average Shift Speed vs.
Acceleration Rate - Vehicle A
50
O
13
Q)
0)
40
QJ
t»0
n)
t-i
30.
20
10
i
/
o
Legend
lst-2nd shift north
lst-2nd shift south
2nd-3rd shift north
2nd-3rd shift south
O
O
1.0
2.0 3.0 4.0
Acceleration Rate (mph/sec.)
5.0
6.0
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Figure III
Average Shift Speed vs.
Acceleration Rate - Vehicle B
60
r
/
50
i
40'-
30--
20'-
10--
Legend
lst-2nd shift north
lst-2nd shift south
2nd-3rd shift north
2nd-3rd shift south
A
O
O
1.0
2.0
3.0
4.0
5.0
6.0
Acceleration Rate (mph/sec.)
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in lst-2nd gear shift speed at an acceleration rate of 4 mph/sec
than anticipated from the shift points at the first three accel-
eration rates. Vehicle B experienced less of a dramatic change of
lst-2nd gear shift speed between the acceleration rates of 3 to 4
mph/sec.
The 2nd-3rd gear shift speed appeared to be approximately
linear with acceleration rates for both vehicles up to accelera-
tions of 3 mph/sec. However, the shift speed for Vehicle A when
accelerating at 3 mph/sec. is not precisely known since it occured
at speeds greater than 60 mph. At acceleration rates of 4 mph/sec.
and above, the 2nd-3rd shift occurred above 60 mph on all test
trials.
The differences between the shift speed characteristics of the
two vehicles are surprising considering the similarity of the
vehicles. Ambient conditions could not have caused the observed
differences since the tests were run concurrently. Operator error
was possible in all test trials since the transmission shifts
were subjectively determined by sound and sensed movement of the
vehicle. However, all tests indicated very repeatable results,
indicating at least consistent operator behavior. No reason, other
than actual vehicle differences could be identified to explain the
variation in the shift speed characteristics of the vehicles.
Direction of travel appeared to have little effect on the test
results. This would be expected since the force required to
accelerate the vehicle would greatly exceed the forces resulting
from the low winds and small track grade. Any effects wind and
track grade might have had, were small.
D. Potential Effects on Vehicle Fuel Consumption
An EPA study has shown that delaying transmission shift
points until higher vehicle speeds results in increased vehicle
fuel consumption, even when the vehicle is accelerated at the same
rate.2/ This effect of transmission shift points on vehicle fuel
economy has also been reported by automotive manufacturers ._3/
Data on typical vehicle use indicate that consumer vehicles
are often operated at acceleration rates greater than 3.3 mph/sec.,
the maximum acceleration rate of the EPA test cycles.^/ Both
vehicles used in this test program demonstrated a delay in the
transmission shift points with increasing acceleration rate.
Therefore, in consumer use the delay in transmission shift points
would be expected to contribute to greater fuel consumption than
that measured on the EPA test cycles. In addition, more rapid
vehicle acceleration demands greater power from the vehicle, which
also results in greater fuel consumption.
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This shortfall between EPA measured fuel economy and consumer
fuel economy would be most dramatic in the case of Vehicle A. For
this vehicle an anomously large change in the speed of the lst-2nd
transmission gear shift, from 24.5 mph to 40.4 mph, occurred when
the vehicle acceleration rate changed from 3 mph/sec to 4 mph/sec.
III. Conclusion
The two vehicles tested exhibited an increase in the vehicle
speed at both the 1st to 2nd and 2nd to 3rd gear shift points with
an increase in acceleration rate.
Vehicle A exhibited a significant anomalous change in the
speed at which the transmisison lst-2nd gear shift occurred
when the vehicle acceleration rate exceeded the maximum accel-
eration rate which occurs during the EPA test cycle. Vehicle B
also experienced a significant, but less dramatic, change in
lst-2nd gear shift characteristics once the vehicle exceeded the
maximum acceleration rate on EPA test cycles. The difference in
the behavior between the two vehicles was attributed to inherent
vehicle-transmission differences.
The fuel consumption of both vehicles in consumer use would be
expected to be greater than that measured on the EPA test cycles
because the acceleration rates of vehicles in consumer use are
often greater than those of the EPA test schedules and because of
the occurrence of the characteristic delay in transmission shift
speeds at the greater acceleration rates. This consumer-EPA
shortfall would be most dramatic in the case of Vehicle A which
experienced a large anomalous delay in the vehicle speed at which
the transmission lst-2nd gear shift occurred when the vehicle
acceleration rate exceeded the maximum acceleration rate of the EPA
test cycles.
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References
I/ "Development of the Federal Urban Driving Schedule," Kruse,
Ronald E., Huls, Thomas A., SAE Paper 730553, Society of
Automotive Engineers, New York, 1973.
2/ Memo to John P. DeKany, EPA/ECTD, "Manual Transmission Shift
Points on the FTP and HFET," Hutchins, F. Peter, EPA/ TAEB,
May 4, 1977.
3/ "A Summary and Analysis of Comments Received in Response
~ to the EPA/NHTSA Information Request Regarding the Effects of
Test Procedure Changes on Fuel Economy," Hourihane, James,
Thompson, Glenn D. , LeBaron, Edward, EPA Technical Report,
January 1980.
k] Memo to Charles Gray, EPA/ECTD, Garbe, Robert J., January
17, 1980.
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Appendix A
Test Equipment
Vehicle A - Silver 1979 Nova
250 CID engine/Ibbl.
Model 350 turbo-hydromatic transmission
EPA combined city/highway : 20 mpg
OEM tires
Approximate test weight: 3750 Ibs.
Vehicle B - Brown 1979 Nova
250 CID engine/Ibbl.
Model 350 turbo-hydromatic transmission
EPA combined city/highway: 20 mpg
OEM tires
Approximate test weight: 3750 Ibs.
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Appendix B
Vehicle A
November 7, 1979
Acceleration Rate
Shift Point
Trial Direction
1 North
South
2 North
South
3 North
South
4 North
South
5 North
South
1 mph/sec
lst-2nd 2nd-3rd
14
13
14
13
13
13
13
13
13
13
23
—
22
29
23
22
22
22
23
22
2 mph/sec
lst-2nd 2nd-3rd
18
15
20
18
19
17
17
20
19
19
43
48
38
53
50
42
52
41
3 mph/sec
lst-2nd 2nd-3rd
24
25
23
23
27
25
27
24
25
23
60+
60+
60+
60+
60+
60+
60+
60+
—
4 mph/sec
lst-2nd
35
35
46
41
37
44
43
40
41
42
5 mph/sec
lst-2nd
44
44
44
44
44
43
44
44
44
44
6 mph/sec
lst-2nd
44
44
44
44
44
44
43
44
44
43
Ambient Temperature:
Barometric Pressure:
Wind Speed:
Wind Direction:
35°
29.06 "HG
7 mph
270°
S
36°
29.06 "HG
8 mph
270°
S
36°
29.06 "HG
5 mph
270°
S
37°
29.05 "HG
6 mph
270°
S
37°
29.05 "HG
6 mph
270°
S
37°
29.05 "HG
8 mph
270°
S
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Acceleration Rate
Shift Point
Trial Direction
1 North
South
2 North
South
3 North
South
4 North
South
5 North
South
Ambient Temperature:
Barometric Pressure:
Wind Speed:
Wind Direction:
1 mph/sec
lst-2nd 2nd-3rd
13
11
10
10
12
12
12
13
11
28
22
19
25
23
26
35°
29.06 "HG
6 mph
315°
SE
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Appendix B
Vehicle B
November 7, 1979
2 mph/sec
lst-2nd 2nd-3rd
23
19
20
18
18
20
18
19
20
18
38
43
42
42
53
44
48
42
44
43
— —
3 mph/sec
lst-2nd 2nd-3rd
23 53
26 59
27 57
24 53
34 60
28 60
28 60
24 60+
30 60
26 60
36°
29.06 "HG
8 mph
270°
S
4 mph/sec
lst-2nd
30
37
29
30
36
31
36
37
36
35
37°
29.06 "HG
6 mph
225°
SW
5 mph/sec
lst-2nd
35
36
36
38
39
36
38
40
39
35
37°
29.05 "HG
6 mph
270°
S
6 mph/sec
lst-2nd
35
41
42
42
42
41
42
42
42
42
37°
29.05 "HG
6 mph
270°
S
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
DATE:
February 12, 1980
SUBJECT-. Release of Report
FROM: Randy Jones
Standards Developm
and Support Branch
T0: Charles L. Gray, Jr., Director
Emission Control Technology Division
THRU: Glenn Thompson, Project Manager
Standards Development and Support Branch
The attached Technical Report has been prepared by SDSB and is now
submitted for your approval for distribution.
Number and Title
SDSB "The Effect of Acceleration Rate on Automatic Trans-
mission Shift Speeds for Two 1979 Novas."
Subject Matter
The results of a recent track test to determine the relation
between acceleration rate and the vehicle speed at the automatic
transmission shift points for two similar 1979 Novas are discussed
in this report.
Results
«—
Each vehicle experienced an increase in the vehicle speed at both
lst-2nd gear and 2nd-3rd gear shift points when the vehicle accler-
ation rate increased. Also, each vehicle experienced a change in
lst-2nd gear shift speed characteristic when the vehicle acceler-
ation rate changed from 3 to 4 mph/sec. For example in the case of
Vehicle "A", an anomalous delay in the speed of the lst-2nd gear
shift point, from 24 to 40 mph, occurred when the accleration rate
changed from 3 to 4 mph/sec.
Conclusion
Recent data indicates consumer vehicles are often operated at
accleration rates exceeding the 3.3 mph/sec. maximum currently
represented on EPA test cycles. Therefore, the report concludes
EPA Form 1320-6 (Rev. 3-76)
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the characteristic delay in shift speed, particularly the dramatic
delay observed in the case of Vehicle "A", could contribute to
greater consumer fuel consumption than that measured on EPA test
cycles.
Attachment
Approved:
Charles L. Gray, DirectorDate
Emission Control Technology Division
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
DATE: Februray 25, 1980
SUBJECT: Distribution of Report
FROM:
TO:
Randy Jones
Standards Develo
t and Support Branch
Distribution List Below
THRU: Charles L. Gray, Jr., Director ^^
Emission Control Technology Division
A copy of the EPA Technical Report, "The Effect of Acceleration
Rate on Automatic Transmission Shift Speed for Two 1979 Novas" is
attached for your information.
Distribution
M. Walsh
R. Maxwell
M. Korth
K. Hellman
G. Reschke
R. Busick
G. Thompson
J. Garvey
Attachment
G. Gruggett
R. Re ineman
D. Murrell
G. Dana
C. Bramson
K. Konishi, JAMA
H. Weaver, MVMA
D. Schwentker, AIA
EPA Form 1320-6 (Rev. 3-76)
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