United States
Environmental Protection
Agency
Motor Vehicle Emission Lab
2565 Plymouth Rd.
Ann Arbor, Michigan 48105
EPA-460/3-81-002
March 1981
Air
&EPA
Dynamometer and Track
Measurement of Passenger
Car Fuel Economy
-------
EPA-460/3-81-002
DYNAMOMETER AND TRACK MEASUREMENT
OF PASSENGER CAR FUEL ECONOMY
by
Falcon Research & Development Co.
One American Drive
Buffalo, New York 14225
Contract No. 68-03-2835
EPA Project Officer: Jack Schoenbaum
Prepared for:
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR, NOISE AND RADIATION
OFFICE OF MOBILE SOURCE AIR POLLUTION CONTROL
EMISSION CONTROL TECHNOLOGY DIVISION
CONTROL TECHNOLOGY ASSESSMENT
AND CHARACTERIZATION BRANCH
ANN ARBOR, MICHIGAN 48105
March, 1981
-------
This report is issued by the Environmental Protection Agency to disseminate technical
data of interest to a limited number of readers. Copies are available free of charge to
Federal employees, current contractors and grantees, and nonprofit organizations—in
limited quantities—from the Library, Motor Vehicle Emission Laboratory, Ann Arbor,
Michigan 48105, or, for a fee, from the National Technical Information Service, 5285
Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by Falcon Research &
Development Co., One American Drive, Buffalo, New York 14225, in fulfillment of Contract
No. 68-03-2835. The contents of this report are reproduced herein as received from
Hamilton Test Systems, Inc. The opinions, findings, and conclusions expressed are those
of the author and not necessarily those of the Environmental Protection Agency. Mention
of company or product names is not to be considered as an endorsement by the En-
vironmental Protection Agency.
-------
-------
TABLE OF CONTENTS
Section Title Page
1.0 INTRODUCTION 1
2.0 SUMMARY AND CONCLUSIONS 2
3.0 BACKGROUND 5
4.0 TEST DESIGN 7
4.1 Dynamometer MPG vs. Track MPG 7
4.2 Tire Type/Tire Pressure Effects 8
4.3 Air Conditioning Effects 8
4.4 Effects of Highway Test Modifications 9
4.5 CVS vs. Meter MPG 10
5.0 TEST VEHICLES 11
6.0 TEST PROCEDURES 14
7.0 RESULTS OF FUEL ECONOMY TESTS 17
8.0 ANALYSIS OF RESULTS 18
8.1 Use of Ratio Measure for Fuel Economy Comparisons 18
8.2 Comparison of Carbon Balance and Volumetric
Measurement 19
8.3 Estimates of Test-to-Test Variability 26
8.4 Dynamometer/Track Effects—Dynamometer Measured
Fuel Economy Compared to Track Measured Fuel Economy 30
8.5 Tire Effects—Fuel Economy Measured with Radial
Tires Compared to Fuel Economy Measured with Bias
Ti res 39
8.6 Cold Tire Warm-Up Effects 42
8.7 Air Conditioning Effects 44
-------
TABLE OF CONTENTS
(Continued)
Section Title Page
8.8 Air Conditioning Simulation Effect 51
8.9 Effects of Modified Cycles 53
8.10 Computed Road Load Horsepower from Coast-Downs 56
9.0 DISCUSSION 60
REFERENCES 70
APPENDIX A COMPARISON OF MODIFIED AND STANDARD HIGHWAY CYCLES 71
APPENDIX B TEST VEHICLE-DESCRIPTION 77
APPENDIX C RESULTS OF FUEL ECONOMY MEASUREMENTS FOR DYNAMOMETER
AND TRACK TESTS 87
APPENDIX D WEIGHTED LEAST SQUARES LINEAR REGRESSION OF VOLUMETRIC
AND CARBON BALANCE DIFFERENCES 119
APPENDIX E TWO-WAY ANALYSIS OF VARIANCE WITH UNEQUAL VARIANCE
ESTIMATES 121
APPENDIX F CALCULATION OF HORSEPOWER FROM COAST-DOWN TIMES 125
-------
LIST OF TABLES
Table Title Page
1 Comparison: Dynamometer MPG vs. Track MPG, 1975 Models
Source: TAEB Report 76-1 6
2 Test Vehicles 12
3 Relationship Between Effects Investigated and Test
Vehicles 13
4 Baseline Test Results 15
5 Numbers of Individual/Averaged Dynamometer Runs 21
6 Estimates of Test-to-Test Squared Coefficient of Variation 27
7 Ratio ± 1 Standard Error of Dynamometer MPG to Track MPG
(Radial, Air Off, Windows Up, Meter 1514 or Corrected) 31
8 Ratio ± 1 Standard Error of Dynamometer MPG to Track MPG
(Bias, Air Off, Windows Up, Meter 1514 or Corrected) 32
9 Ratio ± 1 Standard Error of Dynamometer MPG to Track MPG
(Radial, Air On, Windows Up, Meter 1514 or Corrected) 33
10 Ratio ± 1 Standard Error of Dynamometer MPG to Track MPG
(Bias, Air On, Windows Up, Meter 1514 or Corrected) 34
11 Analysis of Variance Results for Vehicles with and
without Air Conditioning for Selected Driving Sequences 36
12 Ratio ± 1 Standard Error of Dynamometer MPG to Track MPG
(Radial, Air On + Air Off, Windows Up, Meter 1514 or
Corrected) 37
13 Ratio ± 1 Standard Error of Dynamometer MPG to Track MPG
(Bias, Air On + Air Off, Windows Up, Meter 1514 or
Corrected) 38
14 Ratio ± 1 Standard Error of Fuel Economy Measured with
Radial Tires to Fuel Economy Measured with Bias Tires
for Dynamometer Tests 40
"IV
-------
LIST OF TABLES
(Continued)
Table Title Page
15 Ratio ± 1 Standard Error of Fuel Economy Measured with
Radial Tires to Fuel Economy Measured with Bias Tires
for Track Tests 41
16 Ratios of BAGS Fuel Economy with Cold Tires to BAG3 Fuel
Economy with Hot Stabilized Tires as Measured vs. Using
Bias or Radial Tires in Track or Dynamometer Tests 43
17 Ratio ± 1 Standard Error of Fuel Economy Measurement with
Air Conditioning Off to Fuel Economy Measured with Air
Conditioning On for Track Measurements of Vehicles with
Radial Tires 45
18 Ratio ± 1 Standard Error of Fuel Economy Measured with
Air Conditioning Off to Fuel Economy Measured with Air
Conditioning On for Track Measurements of Vehicles with
Bias Tires 46
19 Ratio ± 1 Standard Error of Fuel Economy Measured with
Air Conditioning Off to Fuel Economy Measured with Air
Conditioning on for Dynamometer Measurements of Vehicles
with Radial Tires 47
20 Ratio ± 1 Standard Error of Fuel Economy Measured with
Air Conditioning Off to Fuel Economy Measured with Air
Conditioning On for Dynamometer Measurements of Vehicles
with Bias Tires 48
21 Comparison of Ratios of Air Conditioning/On to Air
Conditioning/Off MPG for Track, Dynamometer and Tire
Type for Selected Driving Cycles 49
22 Ratio ± 1 Standard Error of Fuel Economy Measured with
Air Conditioning Off to Fuel Economy Measured with Air
Conditioning On (Weighted Mean of Dynamometer, Track,
Radial and Bias Tire Results) 50
23 Ratio ± 1 Standard Error of Fuel Economy Measured with
Air Conditioning Off to Fuel Economy Measured with
Simulated Air Conditioning for Dynamometer Measurements 52
-------
LIST OF TABLES
(Continued)
Table Title Page
24 Ratio of Modified Highway Test MPG to Standard Highway
Test MPG for Dynamometer Tests (Air Conditioner Off) 54
25 Ratio of Modified Highway Test MPG to Standard Highway
Test MPG for Track Tests (Air Conditioner Off) 55
26(a) Measured Coast-Down Times and Calculated Road Load
Horsepower for Dynamometer and Track Tests 57
26(b) Measured Coast-Down Times and Calculated Road Load
Horsepower for Dynamometer and Track Tests 58
27 Ratio of RLHP Determined from Track Coast-Down Tests
to RLHP Determined from Dynamometer Coast-Down Tests
(Air Conditioning Off/Windows Up) 59
28 Comparison of Dynamometer to Track Fuel Economy Ratios
as Measured Over the FTP (Mean Ratio ±1 Standard Error) 61
29 Comparison of the Ratios of Fuel Economy Measured
with Radial Tires to Fuel Economy Measured with Bias
Tires for Dynamometer and Track (Mean Ratios ± 1
Standard Error) 62
30 Comparison of the Ratio of Ratios by Two Methods 63
31 Ratio (RQ) of the Mean Horsepower (P^) Due to Rolling
Resistance Measured on a Small Twin-Roll Dynamometer to
the Mean Horsepower Due to Rolling Resistance Measured
on a Large Roll Dynamometer and Corrected to Road 64
32 Comparison of Dynamometer Power Absorber (PA) Settings
in HP 66
-------
LIST OF FIGURES
Figure Title Page
1 Relationship Between Dynamometer and Track Fuel
Economies 20
2 Regression Lines for Differences Between Carbon Balance
and Volumetric Fuel Consumption 23
3 Regression Lines for Difference Between Carbon Balance
and Volumetric Fuel Economy 24
-------
1.0 INTRODUCTION
The Environmental Protection Agency (EPA) is required under
Section 404 of the National Energy Conservation Policy Act of 1978 to
examine and analyze the factors that contribute to the fuel economy
differences achieved by actual road performance of automobiles as
compared to the fuel economies estimated for these automobiles by EPA
test procedures. EPA test procedures measure automobile fuel economy
by operating the vehicle on a chassis dynamometer.
This report is an analysis of data obtained under a testing program
conducted by EPA's Emission Control Technology Division (ECTD). The
analysis deals with a subset of the wide range of factors that contribute
to fuel economy differences measured on a road in consumer service as
compared to EPA estimates using a dynamometer. Specifically, this report
analyzes the relationship between the fuel economy of production cars
tested on dynamometer equipment and the fuel economy they achieve when
operated over the same driving sequence on a test track. The test track
simulates a subset of driving conditions that might be encountered in
actual driving.
The initial thrust of this report is to process the raw data and
statistically analyze any differences. The physical significance of
the results, supplemented wherever possible by other studies conducted
by the ECTD, are then discussed and unresolved issues noted.
-------
2.0 SUMMARY AND CONCLUSIONS
Analysis of the fuel economy data obtained in this program from
dynamometer and track tests on eight 1976 model year production light-
duty vehicles over the urban, highway, steady-state and modified highway
driving cycles permitted quantification of the effects on fuel economy
due to:
(1) Dynamometer and track differences, radial and bias
belted tire differences;
(2) Fuel consumption measurement differences including
carbon-balance-to-meter and meter-to-meter differences;
(3) Air conditioning;
(4) Air conditioning simulation procedure for dynamometer;
and
(5) Coast-down time differences between dynamometer and track.
Results of the analysis showed:
• Fuel economy in miles per gallon, as determined from fuel
consumption measurements over the urban and highway cycles,
ranged from 5% to 12% higher on the dynamometer compared to
track for vehicles tested with radial tires. For vehicles
tested with bias tires fuel economy over the urban and
highway cycles ranged from 5% to 15% higher on the dynamometer
compared to track.
• On dynamometer tests over all cycles, vehicles equipped
with radial tires obtained generally lower fuel economies
than vehicles equipped with bias tires. On track tests
vehicles equipped with radial tires generally obtained a
higher fuel economy than vehicles equipped with bias tires.
However, the fuel economies compared in this way depend
greatly on the type of radial and the type of bias tire as
well as the vehicle tested.
• The relationships between fuel consumption measurements
from flowmeter and carbon balance methods are reasonably
well fitted by straight lines in fuel consumption space.
-------
These lines have offsets that vary from meter to meter
However, the slopes are consistent for all meters and
imply that carbon balance fuel consumptions decrease
relative to meter fuel consumptions at a 5% rate. In
general, meter measured fuel consumptions were greater
than carbon balance fuel consumptions by as much as J>%_
over the range of measured fuel consumptions. No
conclusions could be drawn with regard to absolute
accuracy of the fuel consumption and fuel economy measure-
ment methods.
Operation of a vehicle's air conditioner resulted in an
8% to 17% decrease in fuel economy as measured on the
track over the urban cycle. Over the highway cycle the
decrease in fuel economy due to air conditioning ranges
from 5% to 12% as measured on the track. The simulation
of air conditioning on the dynamometer by a 10% increase
in the P.A.U. setting of the dynamometer above certifica-
tion value produces no significant change in fuel economy
as compared to certification P.A.U, setting.
For the five variations of the EPA highway cycle investigated,
fuel economy effects measured on the dynamometer were
directionally consistent, and statistically equivalent in
magnitude to the effects seen on the track. The results
showed:
(a) Cold starting decreases EPA highway mpg by 10%
(b) The noisy highway schedule produces a 3% lower mpg
compared to the EPA highway cycle
(c) The redistributed highway schedule produces a 4%
lower mpg compared to the EPA highway cycle
(d) The smooth highway schedule produces a 5% increase
in mpg compared to the EPA highway cycle
(e) A 50 mph highway cruise produces an 8% increase in
mpg compared to the EPA highway cycle
Coast-down tests conducted en six of the eight vehicles in
the test program permitted total road load horsepower
calculations at 50 mph on each of the six vehicles for both
track and dynamometer tests. The results showed that total
-------
road load horsepower estimates were generally lower on
the track than on the dynamometer. This result is not
consistent with the fact that the fuel economy estimates
are larger on the dynamometer as compared to track.
However, road load horsepower calculations were con-
sistently higher for bias tires than for radial tires on
track tests and were consistently higher for radial
tires than for bias tires on dynamometer tests. This
result is consistent with the fact that the rolling
resistance of radial tires is generally lower than for
bias tires on track tests.
Recent studies by EPA not within the scope of this program indicate
that small twin-roll dynamometers do not properly simulate vehicle road
loads because of velocity differences measured between the front and
rear rolls of the dynamometer when operating over a driving cycle. In
accordance with Federal Test Procedures, small twin-roll dynamometers
operate with their rolls uncoupled from each other. The front roTl is
coupled to flywheels and a power absorption unit, the latter simulating
the aerodynamic force experienced by a vehicle. The rear roll drives a
tachometer that measures vehicle speed. When the dynamometer rolls are
coupled together, preliminary tests indicate that dynamometer to track
fuel economy differences may be reduced by about 6%. The remaining dyno-
to-track mpg differences are probably explainable by the tire/surface
interaction differences.
-------
3.0 BACKGROUND
The fuel economy data obtained from eight 1976 light-duty passenger
vehicles and analyzed in this report represent data obtained in the
second phase of a program designed to investigate dynamometer/track
fuel economy differences. In the initial phase of the program, six
1975 productions cars were operated on EPA dynamometers and on the Ohio-
Transportation Research Center test track.1 The EPA City and Highway
cycle test results for these six cars are summarized in Table 1.
The dynamometer tests included standard EPA City tests (3-bag 1975
FTP's) and Highway tests, from which combined 55/45 dynamometer fuel
economy values were calculated. Since no systematic offset between
carbon balance and flowmeter mpg measurements was observed in these
tests, the results of these two measurements were averaged for each car.
The city tests conducted on the track employed onjyjiot. .starts, so
a weighted cold start/hot start value for the track Testing had to be
estimated. This was done using each car's ratio of 1975 FTP fuel economy
to hot LA-4 fuel economy, as observed in the dynamometer tests. The
resulting "75 FTP" track mpg values were then used with the raw highway
cycle track data to compute 55/45 track fuel economies.
The "dyno/track" mpg ratios in the table are thus the result of
comparing dyno and track 1975 FTP mpg, highway mpg, and 55/45 mpg.
The averages of these ratios are given at the bottom of the table.
-------
Table 1
COMPARISON:
DYNAMOMETER
SOURCE:
MPG VS. TRACK MPG, 1975 MODELS
TAEB REPORT 76-I1
A. DYNAMOMETER MPG
'75 FTP -Carbon Bal .
- Flowmeter
Average
Hot LA-4 - Carbon Bal .
- Flowmeter
Average
Ratio, '75 FTP/
Hot LA-4
Highway - Carbon Bal .
- Flowmeter
Average
Dyno 55/45 MPG
B. TRACK MPG
Hot LA-4 - Flowmeter
"75 FTP" Track
Highway - Flowmeter
Track 55/45 MPG
C. DYNO/TRACK RATIOS
City
Highway
55/45
VW
RABBIT
90-M*
24.4
23.8
24.10
26.1
25.0
25.55
0.943
36.9
34.5
35.70
28.23
24.0
22.63
33.7
26.56
1.065
1.059
1.063
FORD
PINTO
140-M*
17.8
17.6
17.70
18.9
18.6
18.75
0.944
28.1
27.6
27.85
21.17
16.6
15.67
25.5
18.96
1.130
1.092
1.117
PONTIAC
FIREBIRD
250-M**
17.0
17.3
17.15
17.4
17.8
17.60
0.974
24.4
25.3
24.85
19.93
16.4
15.97
23.8
18.75
1.074
1.044
1.063
FORD
GRANADA
250-A*
13.0
13.1
13.05
14.0
14.1
14.05
0.92.9
18.2
18.9
18.55
15.06
12.5
11.61
16.5
13.40
1.124
1.124
1.124
CHEVROLET
CHEVELLE
350-A**
14.0
13.4
13.70
14.6
13.7
14.15
0.968
19.4
18.7
19.05
15.68
13.1
12.68
17.7
14.54
1.080
1.076
1.078
LINCOLN
CONT'L.
460-A*
9.3
9.8
9.55
10.2
10.5
10.35
0.923
15.0
15.5
15.25
11.48
10.3
9.51
16.2
11.68
1.004
0.941
0.983
SIX-CAR AVERAGE RATIOS: CITY
1.080
HIGHWAY 1.056
55/45 1.071
* Radial Tires
** Bias Tires
-------
4.0 TEST DESIGN
The test program was designed to produce data on the following fuel
economy influences:
« Dynamometer mpg vs. track mpg
» Effects of tire type (radial vs. bias-belted) and tire
pressure
• Effects of air conditioner operation and air conditioner
simulation
• Effects of deviations from the standard EPA Highway Cycle
• Carbon balance vs. volumetric fuel consumption measurement
4.1 Dynamometer MPG vs. Track MPG
The same basic test cycles were run on the dyno and the track, and
included:
t The EPA urban driving schedule ("city cycle" or "LA-4")
i
• The EPA highway driving schedule
• Steady-state cruises
e Modified versions of the EPA highway schedule
e Coastdowns from 60 to 5 mph
Fuel flowmeters were used in the dyno tests to permit comparisons
with the track tests on a common fuel measurement basis. Unfortunately,
the same fuel flowmeter used to measure the fuel economy of a car tested
on a dynamometer was not always used to measure fuel economy of the same
car tested on the test track. Thus, any flowmeter to- flowmeter differences
or biases due to calibration or other effects introduce additional variability
or biases into the differences measured between dyno/track fuel economies.
More will be discussed concerning flowmeter effects in Section 8.2.
-------
-------
For all "A/C on" tests, the air conditioner temperature and blower
controls were set for maximum cooling. In the dyno A/C "simulation"
tests, the air conditioner was turned off and the dyno road load* at
50 mph increased 10% in accordance with EPA certification procedure.
4.4 Effects of Highway Test Modifications
Five variations from the standard EPA highway test were investigated
by means of the following:
• Cold starting, denoted as CST
• "Noisy" driving schedule, denoted as HNO
o "Redistributed" driving schedule, denoted as HRE
• "Smooth" driving schedule, denoted as HSM
t 50 mph steady state cruise
The cold start tests used the standard EPA nonurban driving schedule,
so any observed mpg penalty would derive solely from vehicle warmup.
In the Noisy cycle, the distribution of speeds is virtually the same
as the standard cycle (so no mpg effects of this cycle were related to
road load changes), but the undulations in the cycle are amplified so
that acceleration rates due to cycle "noise" are essentially doubled.
Any mpg penalty for this cycle would be a function of vehicle inertia.
In the Redistributed cycle, the fine texture of the cycle is pre-
served, but blocks of the trace are moved either up or down, giving a
wider distribution of speeds (up to 73 mph and down to 18 mph, compared
to 60 mph maximum and 28 mph minimum for the standard cycle). A fuel
economy penalty seen with this cycle would stem from operation in the
added lower—and higher—speed regimes, both of which are well-known
detriments to fuel economy.
In contrast to the above modifications, which increase the "busyness"
of the cycle, the Smooth cycle consists simply of the standard cycle's
initial acceleration, a constant 50 mph cruise, and the standard cycle's
final deceleration; it is the smoothest possible variant of a 10-mile
drive that begins and ends at idle and averages 48 mph.
Calibrated power abortion unit (PALI) setting
-------
-------
5.0 TEST VEHICLES
The vehicles tested in this program span a wide range of car sizes
and types. The vehicles were 1976 model production cars, with a minimum
of 2000 miles accumulated in routine service prior to the tests.*
Summary descriptions of the vehicles with both dynamometer and track
test data are given in Table 2; Appendix B gives more detailed configura-
tion data on each vehicle.
The vehicles involved in the different effects investigated in the
test program are shown in Table 3.
Exceptions: The Aspen Wagon and Impala had less than 2000 odometer
miles at delivery, and were "aged" to 2000 miles using the EPA
mileage accumulation procedure.
11
-------
Table 2
TEST VEHICLES
MAKE/MODEL
Honda Civic
Datsun B-210
Ford Pinto
AMC Pacer
Ford Granada
Dodge Aspen Wagon
Chevrolet Impala
Chevrolet Chevette
ENGINE
91 CID CVCC
85 CID
140 CID
232 CID
250 CID
225 CID
350 CID
98 CID
WEIGHT
CLASS
2000
2250
3000
3500
4000
4000
5000
2250
TRANSMISSION
4-Speed Manual
4-Speed Manual
3-Speed Auto-
matic
3-Speed Auto-
matic
3-Speed Auto-
matic
3-Speed Auto-
matic
3-Speed Auto-
matic
3-Speed Auto-
matic
AIR
CONDITIONED
No
No
No
Yes
Yes
Yes
Yes
Yes
12
-------
Table 3
RELATIONSHIP BETWEEN EFFECTS INVESTIGATED AND TEST VEHICLES
CAR
Honda CVCC
Datsun B-210
Ford Pinto
AMC Pacer
Ford Granada
Dodge Aspen
Wagon
Chevrolet
Impala
Chevrolet
Chevette
DYNO (METER MPG)
VS. TRACK
No
Radial , Bias
Radial, Bias
Bias
Radial , Bias
Radial , Bias
Radial, Bias
Radial
RADIALS VS.
BIAS-BELT
Dyno
Dyno, Track
Dyno, Track
Track
Dyno, Track
Dyno, Track
Dyno, Track
Track
AIR
CONDITIONING
No
No
No
Dyno, Track
Dyno, Track
Dyno, Track
Dyno, Track
Track
CVS VS.
METER
(DYNO)
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
TIRE WARMUP
Dyno, Bias
Dyno, Track
Radial , Bias
Track,
Radial , Bias
Dyno (Bias),
Track (Radial,
Bias)
Dyno (Radial),
Track (Radial,
Bias)
Dyno, Track
Radial , Bias
Dyno, Track
Radial s
No
MOD. HIGHWAY
CYCLES
Dyno, Radial s
Dyno, Track
Radial s
Dyno, Track
Bias
Dyno, (Bias) ,
Track (Radial,
Bias)
Dyno (Radial)
Track (Radial ,
Bias)
Dyno (Radial ,
Bias)
Track (Radial)
Dyno, Track
Radials
Track (Radials,
Bias)
FUEL FLOWMETER NO.
DYNO/TRACK
1514
Unknown, 2099
1513, 2099, 1514
1472
1514
1513, 1514, Unknown
Unknown, 1514
1513, 1514, 1358
Unknown
Unknown, 1514, 1472
Unknown
Unknown, 1514
Unknown, 1514
1472
Unknown
1472
-------
6.0 TEST PROCEDURES
At arrival, each test car was inspected, and tuning and condition of
vacuum and EGR lines compared to manufacturers' specifications. Five of
the cars required minor adjustments; none of the vehicles was found to
be significantly out of specification.
Following this incoming inspection, each vehicle was given a
standard dyno FTP and HFET test series, using certification-type pre-
conditioning and the certification city and highway procedures. These
baseline tests were used as a go/no-go screening prior to committing the
cars to the full series of dyno and track testing. Results of the base-
line tests are shown in Table 4.
The emissions column in Table 4 gives the highest value for each
pollutant in any one baseline test, not the average values for all base-
line tests. The only instance in which any pollutant exceeded the
levels of the 1976 Federal Emission Standards* was in one Pacer test,
where NOX was 5% high; average NOX for all of the baseline Pacer
tests was within the Standard.
All fuel economy values for the test cars were within 3% of certi-
fication car test results. The Pinto yielded the largest shortfalls
between test car mpg and certification car mpg; 7% city and 8%
highway; nevertheless, the Pinto was accepted for testing in view of
its admirable assault on the 1980 Emission Standards.
Most of the dynamometer tests were performed on the same twin-roll
water brake certification dynamometer, denoted #5 (some tests were
conducted on twin-roll dynamometer denoted #207), using the same inertia
weight and road load settings as each test car's certification couter-
part. Vehicle speed measurements were taken from the reaXdyno roll.
<
The track tests were run on the 7.5 mile high-speed oval at Ohio's
Transportation Research Center, using a 5th wheel for speed indication.
HC = 1.5 g/m; CO = 15 g/m; NO =3.1 g/m
14
-------
Table 4
BASELINE TEST RESULTS
VEHICLE
Honda
(Bias-Belt)
Datsun
(Bias-Belt)
Pinto
(Bias-Belt)
Pacer
(Bias-Belt,
A/C Sim)
Granada
(Radial,
A/C Sim)
Aspen
(Radial,
A/C Sim)
Impala
(Radial ,
A/C Sim)
MAXIMUM 1975 FTP
EMISSIONS, gm/mi(a)
HC 0.80
CO 4.88
NO 1 . 54
X
HC 0.99
CO 8.97
NOX 2.46
HC 0.42
CO 2.51
NOX 1.79
HC 1.06
CO 11.84
NOX 3.27(b)
HC 1.21
CO 3.72
NOX 1.46
HC 0.68
CO 3.03
NOX 2.54
HC 0.57
CO 12.57
NOX 2.50
City
Hwy
55/45
City
Hwy
55/45
City
Hwy
55/45
City
Hwy
55/45
City
Hwy
55/45
City
Hwy
55/45
City
Hwy
55/45
CARBON BALANCE
FUEL EC
Test Car
29.9
41.5
34.2
27.7
39.5
32.0
21.0
29.0
24.0
17.8
21.6
19.4
16.5
18.9
17.5
17.4
22.8
19.4
12.3
18.0
14.3
)ONOMY, MPG
Cert. Car
31.9
41.8
35.7
27.9
39.8
32.2
22.5
31.5
25.8
17.5
22.3
19.4
15.7
19.2
17.1
17.6
22.6
19.5
13.0
18.6
15.0
^ Highest value obtained for each pollutant in any replicate test.
(b)
Average NO for all Pacer baseline tests was 2.95.
/\
15
-------
-------
7.0 RESULTS OF FUEL ECONOMY TESTS
Major test parameters are:
Location (Dynamometer -No./Track)
Vehicle
Tire Type (Radial/Bias Belted)
Tire Pressure(s)
Air Conditioner Status (Off/On/Simulated*)
Fuel Flow Meter Number
Driving Cycle (CC/HH/HC/FTP/HST/CST/HNO/HRE/HSM -
Steady State: 10/20/30/40/50/60/70/80 mph)
Over urban driving cycles, CC/HH/HC/FTP, fuel economy values were recorded
for the individual transient and stabilized segments, viz. BAG1 (cold
transient), BAG2 (hot stabilized) and BAG3(hot transient), included in
the cycle. The BAG1, BAG2, and BAGS fuel economies were considered the
basic data, rather than the overall cycle composite fuel economies.
As will be described in Section 8.3, an analysis of dynamometer and
fuel flowmeter effects led to the conclusion that the two dynamometer
test cells used were essentially equivalent and that certain fuel
flowmeters could be validly aggregated after application of specified
corrections in fuel consumption space.
Tests which matched in all of the above parameters were then considered
replicated, and sample mean fuel economy values were computed. In case of
two or more replications, the coefficient of variation (unbiased estimate
of standard deviation divided by the sample mean) was also computed. These
aggregated results are presented in Appendix C.
Included in the results presented are FTP and HH (i.e., hot-start
urban cycle) fuel economies. These were derived from the individual
bag results by application of the standard FTP formulas.
FTP mpg =
1
r 0-21 i
LBAGI mpgl
f 0-52 ]
[BAG2 mpgj
0.27 I
BAG3 mpgl
HH mpq =
r o:52 i i
[_BAG2 mpgj
f 0.48 *
BAG3 mpg
* Dynamometer runs only.
17
-------
8.0 ANALYSIS OF RESULTS
8.1 Use of Ratio Measure for Fuel Economy Comparisons
Fuel economy differences between dyno and track runs (as well as
between radial and bias-belted tires, air conditioning off and on, and
other factor comparisons) were measured over a wide range of
absolute fuel economy levels, reflecting the various test vehicles and
driving sequences employed. It is desirable, therefore, to display fuel
economy differences in a manner which most effectively unifies the
observed effects throughout the test range of absolute fuel economy
levels.
The two alternatives frequently considered are based on an additive
model and a multiplicative model, respectively. In the former the
measure is the arithmetic difference in fuel economies; in the latter it
is their ratio. Mathematically, if Ej and E2 are the two fuel
economies being compared, these measures are defined as:
and
2
P =
Basically, the additive model is most appropriate when a given influential
factor produces a change in fuel economy from E^ to E2 which tends to
be independent of the magnitude of Ej; the multiplicative model is
appropriate when the change tends to be proportional to E}.
Actually, the use of fuel economy E (in mpg) as a measure of fuel
efficiency is somewhat arbitrary. An equally meaningful variable is its
inverse, fuel consumption C~ ( i n gpm) . Application of the additive
and multiplicative models to the fuel consumption variable yields:
AC = C2 - Cl
C2
pc = c~
L L
18
-------
Note, now, that the assumption of a multiplicative model in E is
fortuitously equivalent to a multiplicative model in C. By definition
of C = 1/E, it is easily seen that
PC = 1/PE
On the other hand, suppose an additive model in E were assumed. One
can then write
A_ c r — — _ — A r r ~ AT
r ? i ~ F "F ~ ~~?~F— - - A- • c.,1 ~ - A L
^ <- 1 tp t, 1 ?
which indicates that constant small fuel economy differences imply fuel
consumption differences proportional to the square of fuel consumption
level. By analogous reasoning, an additive model in C implies fuel
economy differences proportional to the square of fuel economy level.
Inasmuch as the same information is conveyed by A£ or pp_, either
measure may be selected. However, the above considerations suggest that
P£ may be more physically meaningful. Another argument for choosing
PE is that, under the reasonable assumption of constant measurement
error coefficient of variation1* p£ would have constant error variance,
whereas AE would not. It is further noted that the ratio measure was
employed in the previous dynamometer/track fuel economy study by EPA1
and hence its use here would also facilitate comparison of results.
A final consideration is how well the ratio measure fits the observed
data. Figure 1 is a plot of dynamometer fuel economy to track fuel
economy under matched experimental conditions (same car, same tires, same
driving sequence, etc.). Note that a ratio regression line is reasonably
compatible with the data.
8.2 Comparison of Carbon Balance and Volumetric Measurement
Past EPA studies2'3 have noted systematic differences between carbon
balance and volumetric method of fuel economy determination. Inasmuch as
the FTP and HFET dynamometer procedures specify use of the carbon balance
method, whereas in track runs practical considerations dictate reliance on
a fuel flowmeter, any realistic comparison of dynamometer to track fuel
economies must include possible systematic effects of using different
measurement techniques.
19
-------
pr= 1.108 for this example
24 32
TRACK FUEL ECONOMY (mpg)
FIGURE 1. Relationship Between Dynamometer and Track Fuel Economies
20
-------
Since all dynamometer runs in the test program were set up to
measure both carbon balance and volumetric fuel consumptions, it is
technically feasible to calculate the carbon balance to meter systematic
difference as a separate effect. All subsequent analyses could then be
simplified to direct comparison of metered fuel economies in both
dynamometer and track runs.
However, an additional complication which developed in the experi-
mental program was the use of several different fuel flowmeters with
potentially significant systematic differences amongst themselves. Three
of the meters were employed in both dynamometer and track runs and can therefore
be related to carbon balance measurements as a reference. Unfortunately,
three other meters were used only in track runs and are therefore not
accessible to analyses for systematic differences.
There follows below the results of a statistical analysis of
systematic carbon balance to volumetric measurement differences.
Dynamometer runs were identified as having been performed on either
of two dynamometers (#5 or #207) and as using one of three fuel flowmeters
(#1513, #1514, or #2099); in a significant number of instances the meter
identification was missing. The runs were grouped into eight separate
classes (2 dynamometer x 4 meters) to allow for the possibility of both
dynamometer test cell and fuel flowmeter effects. The distribution into
the eight classes was very uneven, and two classes were empty. Within
each class, replicated runs (same car, tires, air conditioning status,
driving sequence, etc.) were averaged. The occupancy of the eight
classes, by numbers of individual runs and numbers after averaging, is
shown in Table 5.
Table 5.
NUMBERS OF INDIVIDUAL/AVERAGED DYNAMOMETER RUNS
DYNO\NO .
NO. \\
5
207
1513
0
12/11
1514
95/58
4/2
2099
21/21
0
UNKNOWN
77/40
7/4
21
-------
For each class two alternative linear models were considered:
AE = E - E = a + bE
cm m
AC=C -C =r+sC
cm m
where E denotes fuel economy (mpg), C denotes fuel consumption (gpm)
and subscripts c and m refer to carbon balance measurements and
volumetric measurements, respectively. Weighted least squares regressions
were then carried out to estimate parameters a, b, r, and s. The
weighting was based on the assumption of a constant coefficient of
variation for the difference between carbon balance and meter readings
(relative to the meter reading as a base) over all individual runs within
a class, and statistical independence of replicated runs. Details of
the regression analyses are given in Appendix D. Figures 2 and 3
present the regression lines obtained for the linear fuel consumption
models and linear fuel economy models, respectively. The lines are
extended to cover only the data range, and the ± la ranges for midpoint
estimates are shown. For comparison purposes the two alternative
regression lines obtained in a recent EPA study are also reproduced in
Figure 2.
It is concluded from an examination of the results, including
residual coefficients of variation (which range from 1 to 3.5%), that:
(1) the linear fuel consumption model provides a somewhat better fit
to the data than the linear fuel economy model; (2) there is no appreciable
effect associated with the use of two different dynamometers; (3) all classes
including the earlier EPA study2'3- showed remarkably similar slopes in the variation
of measured carbon balance to meter differences as a function of absolute
fuel consumption; and (4) there are significant differences in intercept
between meters 1513 and 1514 and between meters 2099 and 1514.
It was accordingly decided to adjust meter 1513 and meter 2099 readings
so as to be consistent with meter 1514 readings. The unknown meter class
(presumably a mixture of meters 1513, 1514, and 2099 readings) was
sufficiently similar to meter 1514 as not to require any adjustment. The
adjustment formulas developed were:
E
adj. I-
where K = -0.00041 for Meter 1513
= +0.00063 fpr Meter 2099
22
-------
O.OOlf
\
-f-
0.04 \ 0.05— 0.06 0.07 Q-.08
NxVOLUMETRIC FUEL CONSUMPTION (CM) (gpm)
\
\
\
\
0:01
-0.001
-0.002
-0.003
M
V -„
\
\
\
EPA Regression Lines3
\3
iGeneral Linear Model
Constrained through Origin
: J \
; KEY:
A
B
C
D
E
F
DYNO METER
NO. NO.
5 2099
207 Unknown
5 1514
5 Unknown
207 1514
207 1513
NO. OF
REPLICATED
GROUPS
21
4
58
40
2
11
FIGURE 2. Regression Lines for Differences Between Carbon Balance and
Volumetric Fuel Consumption
23
-------
l.D
1.0
O
0.5
-0.5
-1.0
10
40
VOLUMETRIC FUEL ECONOMY (EM) (mpg)
KEY:
A
B
C
D
E
F
DYNO
NO.
5
207
5
5
207
207
METER
NO.
2099
Unknown
1514
Unknown
1514
1513
NO. OF
REPLICATED
GROUPS
21
4
58
40
2
11
45
FIGURE 3. Regression Lines for Difference Between Carbon Balance and Volumetric
Fuel Economy
24
-------
These adjustments were also made in all track runs using meters 1513 or
2099. Unfortunately, as previously noted, three other meters were used
on many of the track runs. The calibration of these meters relative to
1514 is unknown. Inasmuch as fuel economy ratios involving these
"uncalibrated" meters could involve an error of appreciable magnitude
just resulting from meter discrepancy, it was decided that ratios would
only be computed where both numerator and denominator readings are from
meter 1514 or adjusted to meter 1514.
The question as to which of the measurements are most accurate in an
absolute sense, however, cannot be determined from this investigation.
The fact that the carbon balance method is indirect whereas the fuel
flowmeters measure volume directly by positive displacement of an
essentially incompressible fluid suggests that the volumetric method is
apt to be more accurate. However, the observed meter- to-
me ter discrepancies certainly argue against placing any more confidence
in the meter data actually obtained than in the carbon balance results.
These considerations further support the decision to express all ratios on the
basis of a common meter reference.
If one wished to proceed further and attempt to estimate real dyno-
to-track fuel economy ratios where dyno fuel economy is measured by the
carbon balance method, then one could multiply the ratios presented
later in this report by the ratio of measured carbon balance to meter
1514 derivable from Figure 2. The latter is seen to vary from about
1.04 at fuel consumption levels of 0.08 gpm (12.5 mpg) to about 1.015
at fuel consumption levels of 0.025 gpm (40 mpg). However, it should
be kept in mind that the composite ratios so derived are meaningful only
in the context of meter 1514 (or one with similar calibration) employed
in measuring track fuel economy. The composite ratios would change if
the track meter had substantially different calibration. In the final
analysis, proper resolution of this whole problem requires the applica-
tion of a fuel measurement technique of validated high accuracy against
which all other measurements could be compared.
25
-------
8.3 Estimates of Testr-to-Test Variability
The presence of replicated runs in the data base permits estimation
of the basic variability from test to test in volumetric fuel economy
measurement. Such estimates are necessary for statistical analysis of
significant effects. The assumed model is that of a constant coefficient
of variation (COV), i.e., standard deviation divided by mean fuel economy
over the range of measured fuel economies.** However, one must allow for
the possibility of different COV's over track and dyno runs and also
over various driving sequences. The latter were partially aggregated
into BAG1/BAG3, BAG2, HST/CST, HNO/HRE, HSM, and CRUISE classes,
based on the judgment that hot vs. cold start has no impact on measure-
ment error, similarity of noisy and redistributed highway sequences, and
insufficient numbers of CRUISE replications at individual speeds.
Table 6 presents estimated COV's for each of the indicated classes,
determined as a weighted average of estimates from individual replicate
groups. As a result of the meter adjustments described in Section 8.2,
all dynamometers were rendered comparable; however, track runs
with uncalibrated meters additionally had to agree in meter number to
qualify as replicates. The number of degrees of freedom for estimation
is given by d.f. = £(n.j - 1) where n-j is the number of replications
in the i replicate group and summation is over all replicate groups
in a class.
Analysis revealed that differences among BAG2, HST/CST, HNO/HRE,
HSM, and CRUISE estimates of (COV)2 were not statistically signifi-
cant. Accordingly, these classes were pooled. Differences between
BAG1/BAG3 and the pooled results were statistically significant. We
are thus left with distinct estimates of (COV)2 for four cases: Dyno-
BAG1/BAG3, Dyno-Other, Track-BAGl/BAG3, Track-Other. Fortuitously,
these were found to be well-approximated by
DYNO
TRACK
BAG1/BAG3
OTHER
2 (COV)2
(COV)2
4 (COV)2
2 (COV)2
26
-------
Table 6
ESTIMATES OF TEST-TO-TEST SQUARED COEFFICIENT OF VARIATION
DRIVING SEQUENCE
BAG1/BAG3
BAG2
HST/CST
HNO/HRE
HSM
CRUISE
BAG2/HWY/CRUISE**
DYNAMOMETER
(COV)2 (%)2
7.34
2.25
3.69
3.42
4.02
4.97
3.53
d.f.*
56
32
32
30
15
24
133
TRACK
(COV)2 (%)2
14.36
7.78
8.76
2.37
5.24
7.56
7.13
d.f.*
64
73
44
30
12
106
265
* Number of degrees-of-freedom for estimation.
** Pooling of BAG2, HST/CST, HNO/HRE, HSM, and CRUISE.
27
-------
or in terms of COV by
BAGI/BAG3
OTHER
DYNO
TRACK
/T(COV)0
(COV)Q
2 (COV)Q
/2~(COV)0
where (COV)Q - 1.9%.
To investigate the consistency of these dynamometer test-to-test
variability estimates with previously obtained results, we note first
that the COV estimate for FTP fuel economy (0.21 BAG1 + 0.12 BAG2 +
0.27 BAG3) derived from the above is [(0.21)2 • 2 (COV)§ + (0.52)2 •
(COV)g + (0.27) - 2 (COV)£] = 1.35%. The HFET (Highway) fuel economy
COV is, of course, just 1.9%. Reference 4 indicates COV's reported
in the literature ranging from 0.75 to 4.8% and also includes an analysis
of recent EPA tests on thirty-one automobiles5 which yielded FTP and
HFET fuel economy COV's of 1.5% and 1.9%, respectively. COV estimates
based on data from the present program are therefore very much in line
with other estimates.
In subsequent sections, ratios of sample mean fuel economies are
calculated. The above results for test-to-test coefficient of variation
are used to estimate the standard error of the mpg ratios as follows:
mpg.
P =
where mpg^ and mpgo are sample means of Nj and N2 measurements,
respectively, and the squared coefficient of variation of single test
results are (COV)f and (COV)2, respectively. Then the standard error
of the estimate p is given by:
(s.e.)p =
/(COVjj2
(COV)
For example, if mpg is dynamometer BAG2 value with 3 replications and
inpgT is a track BAG2 value with 4 replications then
2r>
O
-------
(s.e.)p =
(COV)2 2 (COV)
'0
- = 0.91 (COV)Q = 0.015.
The standard error for FTP and HH ratios derived from replicated
BAG measurements is somewhat more involved. For example, if dynamometer
FTP is derived from an N^-replicate BAGjl value, an N12-replicate
BAG2 value, and an N13-replicate BAGS value, the standard error for
p = FTP (dyno)/FTP (track) is
(s.e.)p =
(0.21)2 2 (COV)2 (0.52)2 (COV)2 (0.27)2 2 (COV)2
11
12
13
(0.21)2 4 (COV)2 (0.52)2 2 (COV)2 (0.27)2 4 (COV)2
21
22
N
23
/0.0882 , 0.2704 . 0.0882 0.1764 0.5408 0.1764
/ ri + r, + —r. + ——r, + r, + n
11
12
13
21
22
23
With only one replication for each BAG, the dyno/track FTP ratio standard
error would become (s.e.)p = 0.022. The modest numbers of replications
appearing in the data generally result in ratio standard errors in the
range of 0.01 to 0.015, i.e., 1 to 1.5%
29
-------
8.4 Dynamometer/Track Effects—Dynamometer Measured Fuel Economy
Compared to Track Measured Fuel Economy
The prime focus of this program is to quantify when possible the
magnitudes of the differences between fuel economy as measured on a
dynamometer and on a test track. As previously discussed, the parameter
chosen to quantify the dyno/track effect is the ratio of the fuel economy
as measured by fuel flowmeter on a dynamometer, to fuel economy as measured
by fuel flowmeter on a test track. These ratios have been computed where
meter 1514 (or a meter that could be corrected to #1514) was used for both
the dynamometer and track measurements (i.e., meter 1514 was used as the
basis to which all the meters were corrected where possible).
Tables 7 through 10 present the calculated ratios with their
standard errors for the four tire-type/air-conditioning configurations:
radial tire/air off, radial tire/air on, bias tire/air off, and bias tire/
air on. Ratios were calculated for the above four groups to consider
possible effects due to either tire type and/or air conditioning. Once
the ratios are computed by group, an analysis of variance may be used to
test whether significant differences exist between the ratios of any two
groups. For instance, it is reasonable to expect that the dynamometer-
to-track effect (i.e., the ratio) should be the same when the vehicle
is tested with air conditioning on and air conditioning off.
To test our hypothesis that the ratios between two groups are the
same, we assume a model of the form:
y.. =y + b. + t. +e..
ij i i ij
where: y.. are the computed ratios for each i vehicle in the j
1J group (i.e., air or no air conditioning),
y is the mean ratio over all vehicles and groups,
b.j is the deviation from the mean ratio due to each itn
vehicle,
t.: is the deviation from the mean ratio due to each jth
group, and
e.. is the random component of error due to both measurement
1J and test variance for the ith vehicle in the jth
group.
In the above model the e-jj are assumed independent. By a weighted analysis
of variance, we may test for vehicle-to-vehicle differences in the ratios
(b. £ b) and group-to-group differences in the ratios (t. £ t). A complete
I vJ
30
-------
Table 7
RATIO ± 1 STANDARD ERROR OF DYNAMOMETER MPG TO TRACK MPG
(Radial, Air Off, Windows Up, Meter 1514 or Corrected)
BAG1
BAG2
BAG 3
FTP
HH
HST
CST
HND
HRE
HSM
10
20
30
40
50
60
PINTO
0.992 ± 0.033
1.055 ± 0.018
1.103 ± 0.029
1.051 ± 0.014
1.078 ± 0.017
1.063 ± 0.022
0.911 ± 0.030
1.023 ± 0.030
1.040 ± 0.030
1.074 ± 0.030
1.045 ± 0.030
1.027 ± 0.030
HONDA*
1.122 ± 0.029
1.111 ± 0.015
1.115 ± 0.022
1.114 ± 0.011
1.113 ± 0.013
1.118 ± 0.016
1.100 ± 0.030
1.159 ± 0.022
1.170 ± 0.022
1.084 ± 0.029
ASPEN
1.100 ± 0.029
1.100 ± 0.016
1.066 ± 0.027
1.092 ± 0.012
1.080 ± 0.015
1.066 ± 0.016
1.053 ± 0.033
1.053 ± 0.019
1.016 ± 0.016
1.053 ± 0.017
1.011 ± 0.033
0.991 ± 0.033
0.942 ± 0.033
1.021 ± 0.033
1.016 ± 0.033
0.993 ± 0.033
* Combined meter unknown and 2099 corrected on track.
31
-------
Table 8
RATIO ± 1 STANDARD ERROR OF DYNAMOMETER MPG TO TRACK MPG
(Bias, Air Off, Windows Up, Meter 1514 or Corrected)
BAG1
BAG 2
BAG 3
FTP
HH
HST
CST
HND
HRE
HSM
10
20
30
40
50
60
PINTO
1.051 ± 0.042
1.113 ± 0.018
1.152 ± 0.020
1.106 ± 0.015
1.132 ± 0.017
1.127 + 0.022
1.105 ± 0.019
1.114 ± 0.019
1.060 ± 0.022
HONDA
1.191 ± 0.031
1.076 ± 0.018
1.062 ± 0.025
1.097 ± 0.013
1.070 ± 0.015
1.148 ± 0.019
0.712 ± 0.027
0.919 ± 0.027
1.350 ± 0.027
1.350 ± 0.027
1.210 ± 0.027
PACER
1.065 ± 0.030
1.016 ± 0.033
1.040 ± 0.026
1.116 ± 0.029
ASPEN
1.179 ± 0.042
1.131 ± 0.016
1.120 ± 0.025
1.140 ± 0.014
1.126 ± 0.014
1.086 ± 0.021
0.825 ± 0.027
1.117 ± 0.027
1.035 ± 0.027
1.099 ± 0.027
1.118 ± 0.027
1.066 ± 0.027
32
-------
Table 9
RATIO ± 1 STANDARD ERROR OF DYNAMOMETER MPG TO TRACK MPG
(Radial, Air On, Windows Up, Meter 1514 or Corrected)
BAG1
BAG2
BAG3
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
ASPEN
1.111 ±
1.090 ±
1.015 ±
1.076 ±
1.052 ±
1.044 ±
0.870 ±
0.990 ±
0.950 ±
1.018 ±
1.029 ±
0.934 ±
0.033
0.019
0.033
0.015
0.019
0.019
0.027
0.027
0.027
0.027
0.027
0.027
33
-------
Table 10
RATIO ± 1 STANDARD ERROR OF DYNAMOMETER MPG TO TRACK MPG
(Bias, Air On, Windows Up, Meter 1514 or Corrected)
BA61
BAG2
BAGS
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
PACER
1.019 ± 0.033
1.083 ± 0.016
1.049 ± 0.029
1.057 ± 0.013
1.066 ± 0.016
1.150 ± 0.025
0.884 ± 0.033
0.967 ± 0.033
1.030 ± 0.033
1.038 ± 0.033
1.029 ± 0.033
ASPEN
1.216 ± 0.027
1.165 ± 0.038
1.193 ± 0.023
1.035 ± 0.021
34
-------
derivation and explanation of this analysis is presented in Appendix E.
Application of the above analysis of variance indicates that there
is no significant difference in the computed ratios (dynamometer fuel
economy to track fuel economy) for vehicles with air conditioning on and
for vehicles with air conditioning off. There is however, a significant
car to car effect among the calculated ratios. The analysis of variance
results for the FTP and HST driving cycles is presented in Table 11.
In Table 11 the quantities S/E and T/E are presented with the
estimate of y and SQZ. The quantity S is the reduction in mean
square error associated with fitting b-j, the quantity T is the
reduction in mean square error associated with fitting tj, and the
quantity SQZ is an externally derived mean squared error (with a large
number of degrees of freedom) which provides an estimate for the internal
mean squared error E. The ratios S/E and T/E were then compared
with F distributions of equivalent degrees of freedom at a selected
significance level (i.e., 0.05).
In all instances presented in Table 11 we reject the hypothesis that
vehicle effects are all the same (b-j =b) and accept the hypothesis that
a/c on and off effects are the same (tj 5 t). Thus we may combine the
ratios computed with air conditioning on with the ratios computed with
air conditioning off, but we may not combine the ratios computed for car
A with the ratios computed for car B. The ratios are combined by
inverse weighting by their standard errors for air off and air on and
are presented in Tables 12 and 13 for vehicles equipped with radial and
bias tires, respectively. Vehicle-to-vehicle differences within each
tire type group are evident. In addition, each vehicle equipped with
radial tires appears to have a different ratio when equipped with bias
tires. Fuel economy differences due to tire configuration effects are
discussed in the next section.
35
-------
Table 11
ANALYSIS OF VARIANCE RESULTS FOR VEHICLES
WITH AND WITHOUT AIR CONDITIONING
FOR SELECTED DRIVING SEQUENCES
VEHICLE
CONFIGURATION
HQ: b. »b
Bias Tires
Radial Tires
V V
Bias Tires
Radial Tires
DRIVING SEQUENCE
FTP
y = 1-087
SQ2 = 0.46385
d.f. = 4
S/E = 6.25*
d.f. = 4
T/E = 0.68
HH
y - 1.103
SQ2 = 0.8358
d.f. = 6
S/E = 9.96*
d.f. = 6
T/E = 0.08
HST
y = 1.108
SQ2 = 1.3365
d.f. = 6
S/E = 5.0*
y = 1.076
SQ2 = 0.9053
d.f. = 4
S/E = 3.18*
d.f. = 6
T/E = 0.73
d.f. = 4
T/E = 1.30
* Significant at 0.05 level.
36
-------
Table 12
RATIO ± 1 STANDARD ERROR OF DYNAMOMETER MPG TO TRACK MPG
(Radial, Air On + Air Off, Windows Up, Meter 1514 or Corrected)
BAG1
BAG2
BAGS
FTP
HH
HST
CST
HND
HRE
HSM
10
20
30
40
50
60
PINTO
0.992 ± 0.033
1.055 ± 0.018
1.103 ± 0.029
1.051 ± 0.014
1.078 ± 0.017
1.063 ± 0.022
0.911 ± 0.030
1.023 ± 0.030
1.040 ± 0.030
1.074 ± 0.030
1.045 ± 0.030
1.027 ± 0.030
HONDA
1.122 ± 0.029
1.111 ± 0.014
1.115 ± 0.022
1.114 ± 0.011
1.113 ± 0.013
1.118 ± 0.016
1.100 ± 0.030
1.159 ± 0.022
1.170 ± 0.022
1.084 ± 0.029
ASPEN
1.105 ± 0.022
1.096 ± 0.012
1.046 ± 0.021
1.086 ± 0.010
1.069 ± 0.012
1.056 ± 0.012
1.053 ± 0.033
1.053 ± 0.019
1.016 ± 0.016
1.053 ± 0.017
0.926 ± 0.021
0.990 ± 0.021
0. 950 ± 0.021
1.019 ± 0.021
1.024 ± 0.021
0.958 ± 0.021
37
-------
Table 13
RATIO ± 1 STANDARD ERROR OF DYNAMOMETER MPG TO TRACK MPG
(Bias, Air On + Air Off, Windows Up, Meter 1514 or Corrected)
BAG1
BAG 2
BAGS
FTP
HH
HST
CST
HND
HRE
HSM
10
20
30
40
50
60
PINTO
1.051 ± 0.042
1.113 ± 0.018
1.152 ± 0.029
1.106 ± 0.015
1.132 ± 0.017
1.127 ± 0.022
1.105 ± 0.019
1.114 ± 0.019
1.060 ± 0.022
HONDA
1.191 ± 0.031
1.076 ± 0.018
1.062 ± 0.025
1.097 ± 0.013
•1.070 ± 0.015
1.148 ± 0.019
0.712 ± 0.027
0.919 ± 0.027
1.350 ± 0.027
1.350 ± 0.027
1.320 ± 0.027
PACER
1.019 ± 0.033
1.079 ± 0.014
1.035 ± 0.022
1.057 ± 0.013
1.059 ± 0.014
1.136 ± 0.019
0.884 ± 0.033
0.967 ± 0.033
1.030 ± 0.033
1.038 ± 0.033
1.019 ± 0.033
ASPEN
1.179 ± 0.042
1.154 ± 0.014
1.133 ± 0.021
1.140 ± 0.014
L145 ± 0.012
1.060 ± 0.015
0.825 ± 0.027
1.117 ± 0.027
1.035 ± 0.027
1.099 ± 0.027
1.118 ± 0.027
1.066 ± 0.027
38
-------
8.5 Tire Effects—Fuel Economy Measured with Radial Tires Compared to
Fuel Economy Measured with Bias Tires
Testing of the vehicles with both bias belted and radial tires on
the dynamometer and the test track permits a comparison of the effect
of tire type on fuel economy. The ratio of the meter measured fuel
economy of a vehicle with radial tires to the meter measured fuel economy
of the same vehicle with bias belted tires is computed and presented in
Tables 14 and 15 for track and dynamometer runs, respectively.
Before the combined ratios in Tables 14 and 15 were computed, they
were computed separately for the conditions of air conditioning on and
off. Since no significant air conditioning effect was detected in
Section 8.4 and since there is no apparent basis for considering a tire
type air conditioning interaction effect,.the ratios (air on and off) were
combined. Also note in Tables 14 and 15 that since the same fuel meter
was often used to test the vehicle with radial and with bias tires,
more ratio calculations are possible than were possible for dynamometer-
to-track ratio calculations.
In general, we note that the radial-to-bias ratio is dependent on the
driving cycle and can be less than or greater than one. Ratios computed
from track tests are generally greater than one and tend to support the
contention that radial tires achieve somewhat better fuel economy
(0 to 4% better for highway cycle) than bias tires. For comparisons
on the dynamometer, ratios are generally lower than one, implying that
dynamometer testing—instead of simulating the on-road fuel efficiency
of radial tires in comparison to bias belted tires, generally shows
radial tires at a relative disadvantage.
39
-------
Table 14
RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH RADIAL TIRES
TO FUEL ECONOMY MEASURED WITH BIAS TIRES FOR DYNAMOMETER TESTS
BAG1
BAG 2
BAG 3
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
PINTO
0.975 ± 0.027
0.964 ± 0.016
0.965 ± 0.022
0.967 ± 0.012
0.964 ± 0.014
0.980 ± 0.015
0.952 ± 0.023
0.961 ± 0.023
0.917 ± 0.023
0.990 ± 0.023
0.980 ± 0.023
0.967 ± 0.023
HONDA
0.997 ± 0.024
1.029 + 0.013
1.030 ± 0.017
1.022 ± 0.010
1.034 ± 0.011
0.985 ± 0.017
0.984 ± 0.019
0.987 ± 0.023
0.989 ± 0.023
0.990 ± 0.023
0.986 ± 0.023
0.988 ± 0.023
0.987 ± 0.023
DATSUN
0.967 ± 0.024
0.985 + 0.014
0.994 ± 0.019
0.984 ± 0.010
0.990 ± 0.012
0.975 ± 0.014
0.969 ± 0.023
1.008 ± 0.017
1.116 ± 0.017
0.962 ± 0.019
0.958 ± 0.019
0.953 ± 0.019
0.958 ± 0.019
1.000 ± 0.019
0.968 ± 0.019
ASPEN*
0.999 ± 0.021
0.977 ± 0.013
0.989 ± 0.018
0.992 ± 0.009
0.983 ± 0.010
1.038 ± 0.012
1.002 ± 0.027
0.989 ± 0.016
1.002 ± 0.016
1.198 ± 0.027
0.997 ± 0.017
0.997 ± 0.027
0.977 ± 0.027
0.988 ± 0.027
0.983 ± 0.027
IMPALA
0.961 ± 0.027
1.014 + 0.016
0.988 ± 0.023
0.996 ± 0.012
1.001 ± 0.014
0.982 ± 0.014
* Combined ratios for air on and air off.
-------
Table 15
RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH RADIAL TIRES
TO FUEL ECONOMY MEASURED WITH BIAS TIRES FOR TRACK TESTS
BAG1
BAG2
BAGS
FTP
HH
HC
HST
CST
UNO
HRE
HSM
10
20
30
40
50
60
70
BO
PINTO
1.032 ± 0.047
1.017 ± 0.020
1.008 ± 0.035
1.018 ± 0.017
1.013 ± 0.019
—
1.039 ± 0.027
0.978 ± 0.033
—
—
—
—
—
—
—
—
—
—
HONDA
1,057 ± 0.035
0.997 ± 0.019
0.982 ± 0.028
1.006 ± 0.014
0.994 ± 0.017
—
1.012 ± 0.018
—
0.992 ± 0.027
1.009 ± 0.027
1.029 ± 0.033
1.070 ± 0.027
0.955 ± 0.027
1.088 ± 0.027
1.064 ± 0.027
1.028 ± 0.027
—
— —
DATSUN
1.093 ± 0.042
1.040 ± 0.016
1.053 ± 0.028
1.055 ± 0.014
1.046 ± 0.016
—
1.034 ± 0.019
—
—
—
—
0.998 ± 0.027
1.009 ± 0.027
1.030 ± 0.027
1.033 ± 0.027
1.035 ± 0.027
1.020 ± 0.027
1.011 ± 0.027
1.027 ± 0.027
CHEVETTE
1.028 ± 0.038
1.016 ± 0.022
1.060 ± 0.030
1.030 ± 0.016
1.037 ± 0.018
—
1.022 ± 0.029
—
0.995 ± 0.027
1.019 ± 0.027
PACER*
—
1.051 ± 0.033
0.970 ± 0.047
—
1.015 ± 0.028
1.009 ± 0.028
0.999 ± 0.038
1.025 ± 0.033
—
—
1.012 ± 0.027]
—
1.073 ± 0.027
1.108 ± 0.027
1.054 ± 0.027
1.013 ± 0.033
0.988 ± 0.027
1.064 ± 0.027
—
—
—
—
—
— — — —
ASPEN**
1.107 ± 0.044
1.029 ± 0.013
1.066 ± 0.023
1.057 ± 0.015
1.048 ± 0.013
—
1.044 ± 0.015
—
—
—
- —
1.053 ± 0.021
1.068 ± 0.021
1.075 ± 0.021
1.058 ± 0.021
1.073 ± 0.021
1.058 ± 0.021
—
—
IMPALA**
1.100 ± 0.025
1.075 ± 0.011
1.071 ± 0.022
1.080 ± 0.010
1.075 ± 0.012
—
1.030 ± 0.018
—
—
—
—
0.892 ± 0.028
1.038 ± 0.023
1.040 ± 0.023
1.014 ± 0.023
1.030 ± 0.023
1.007 ± 0.023
1.027 ± 0.023
1.032 ± 0.023
GRANADA
0.930 ± 0.038
0.986 ± 0.016
0.977 ± 0.023
0.970 ± 0.013
0.980 ± 0.013
—
1.030 ± 0.019
—
—
—
—
1.103 ± 0.038
1.036 ± 0.033
1.009 ± 0.033
1.017 ± 0.036
1.014 ± 0.036
1.018 ± 0.036
1.025 ± 0.036
0.999 ± 0.036
* Meter 1358 data for radial only not used; ** Combined ratios with air on and off
-------
8.6 Cold Tire Warm-Up Effects
In order to assess the potential influence of tire warm-up on fuel
economy, comparable hot start LA-4 cycles were run using hot stabilized
tires (HH) and cold tires (HC). These tests were conducted on the Aspen,
Datsun, and Granada. Both the HC and HH fuel economies are computed
by harmonically combining the fuel economies measured from BAGS2 and 3.
In all cases tested, there were no significant differences either between
HC and HH tests or between BAGS tests run with hot tires and BAGS tests
run with cold tires. BAGS fuel economies were compared because these were
the first segments of the HC and HH cycles and any fuel economy
differences due to tire temperature should be greatest over the BAGS
segment.
Table 16 presents the ratios of HC to HH BAGS fuel economies as
measured on the test track and dynamometer with either bias belted or
radial ply tires. Comparisons between hot and cold tire fuel economies
were made only where the same meter was used for measurement. In none
of the individual cases, or combined groups, are the ratios significantly
different from 1.00.
42
-------
Table 16. RATIOS OF BAGS FUEL ECONOMY WITH COLD TIRES TO BAGS FUEL ECONOMY WITH HOT STABILIZED
TIRES AS MEASURED VS. USING BIAS OR RADIAL TIRES IN TRACK OR DYNAMOMETER TESTS
^^tEST LOCATION
TIRE TYPE
VEHICLE
Aspen
Datsun
Granada
Honda
WEIGHTED MEAN
(By Facility &
Tire Type)
WEIGHTED MEAN
(By Facility)
TRACK
BIAS
N*
2/2
1/2
2/3
Ratio ± 1 S.E.**
1.033 ± 0.038
0.992 ± 0.047
1.003 ± 0.035
—
RADIAL
N*
1/2
1/4
1/1
Ratio ± 1 S.E.**
0.951 ± 0.047
0.995 ± 0.042
1.072 ± 0.054
—
1.011 ± 0.023 1.000 ± 0.027
1.006 ± 0.018
DYNAMOMETER
BIAS
N*
3/1
Ratio ± 1 S.E.**
—
—
0.953 ± 0.031
RADIAL
N*
2/2
Ratio ± 1 S.E.**
—
0.977 ± 0.027
—
—
0.953 ± 0.031 0.977 ± 0.027
0.967 ± 0.020
CO
* Number of HC BAGS runs/number of HH BAGS runs.
** Standard errors based on COV estimated for test-to-test variability of BAG1/BAG3 runs on track and
dynamometer derived in Section 8.3
-------
8.7 Air Conditioning Effects
Ratios of the meter-measured fuel economy with air conditioning off
to the meter-measured fuel economy with air conditioning on have been
computed for both dynamometer and track measurements separately. The
results are presented in Tables 17 through 20 for the four groups:
radials on track, radials on dynamometer, bias on track and bias on
dynamometer.
A subjective analysis of variance may be conducted by inspection of
the ratios as recompiled in Table 21 for the four groups of conditions
described. Notice that for each of the driving cycles presented, the four
ratios for each vehicle do not appear to have any systematic pattern and
may be collapsed into one ratio by weighted averaging (proportional to the
inverse square of the standard error of each of the four group ratios).
The recomputed ratios of fuel economy measured with air conditioning
off to fuel economy measured with air conditioning on over all dynamometer,
track, radial and bias tire configurations are presented in Table 22. It
may be noted in Table 22 that a reduction is achieved in standard error for
the weighted ratios as compared to the standard error for the individual
configuration unweighted ratios, and that an apparently significant vehicle-
to-vehicle difference in ratios remains. These ratios indicate decreases
in fuel economy due to air conditioning ranging from 8 to 17% over the
urban cycle and 5 to 12% over the highway cycle.
The air conditioning effect in Table 22 appears to be inversely
related to vehicle speed for the steady-state runs. That is, the ratios
(converted to percent differences) calculated for each of the steady-state
speeds indicated in the table decrease from about 16% at 10 mph to about
5% at 80 mph.
44
-------
Table 17. RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASUREMENT WITH AIR CONDITIONING OFF
TO FUEL ECONOMY MEASURED WITH AIR CONDITIONING ON FOR TRACK MEASUREMENTS OF
VEHICLES WITH RADIAL TIRES
en
BAG1
BAG2
BAG3
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
70
80
GRANADA*
1.150 ± 0.038
1.181 ± 0.016
1.192 ± 0.025
1.176 ± 0.013
1.186 ± 0.014
1.112 ± 0.015
—
---
—
—
1.164 ± 0.033
1.187 ± 0.033
1.131 ± 0.033
1.131 ± 0.033
1.102 ± 0.033
1.090 ± 0.033
1.111 ± 0.033
1.014 ± 0.033
CHEVETTE**
1.081 ± 0.038
1.098 ± 0.022
1.129 ± 0.030
1.101 ± 0.016
1.113 ± 0.018
1.050 ± 0.022
—
—
—
—
—
1.139 ± 0.027
1.119 ± 0.027
1.081 ± 0.027
1.033 ± 0.033
0.995 ± 0.027
1.029 ± 0.027
—
PACER***
1.044 ± 0.047
1.034 ± 0.020
1.103 ± 0.038
1.055 ± 0.018
1.064 ± 0.021
1.091 ± 0.038
—
1.070 ± 0.027
1.049 ± 0.027
1.086 ± 0.033
—
1.180 ± 0.027
1.095 ± 0.027
1.051 ± 0.027
1.058 ± 0.027
1.042 ± 0.027
1.001 ± 0.027
1.055 ± 0.027
ASPEN****
1.080 ± 0.035
1.108 ± 0.018
1.040 ± 0.035
1.084 ± 0.015
1.074 ± 0.019
1.062 ± 0.021
—
—
—
—
1.031 ± 0.033
1.163 ± 0.033
1.123 ± 0.033
1.063 ± 0.033
1.082 ± 0.033
1.052 ± 0.033
—
—
1
IMPALA**
1.056 ± 0.038
1.110 ± 0.017
1.083 ± 0.032
1.091 ± 0.015
1.097 ± 0.018
1.043 ± 0.025
—
---
—
—
—
1.206 ± 0.027
1.153 ± 0.027
1.111 ± 0.027
1.069 ± 0.027
1.100 ± 0.027
1.063 ± 0.027
1.056 ± 0.027
* Meter 1514 + Unknown *** Meter 1358
** Meter 1472 **** Meter 1514
-------
Table 18.
RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH AIR CONDITIONING OFF
TO FUEL ECONOMY MEASURED WITH AIR CONDITIONING ON
FOR TRACK MEASUREMENTS OF VEHICLES WITH BIAS TIRES
BAG1
BAG 2
BAGS
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
70
80
GRANADA*
1.103 ± 0.038
1.187 ± 0.016
1.148 ± 0.023
1.157 ± 0.013
1.169 ± 0.013
1.117 ± 0.022
—
—
—
—
—
—
—
1.134 ± 0.033
1.157 ± 0.033
1.119 ± 0.033
1.140 ± 0.033
1.019 ± 0.033
PACER*
—
1.154 ± 0.028
1.154 ± 0.044
—
1.154 ± 0.025
1.154 ± 0.031
—
—
—
—
—
—
—
—
—
—
—
—
ASPEN**
—
1.100 ± 0.022
1.045 ± 0.033
—
1.075 ± 0.020
1.062 ± 0.022
—
—
—
—
1.172 ± 0.027
1.142 ± 0.027
1.125 ± 0.027
1.073 ± 0.027
1.059 ± 0.027
1.058 ± 0.027
—
—
IMPALA***
1.028 ± 0.031
1.080 ± 0.016
1.068 ± 0.035
1.066 ± 0.015
1.074 ± 0.019
1.059 ± 0.031
—
—
—
—
1.199 ± 0.038
1.301 ± 0.038
1.134 ± 0.038
1.064 ± 0.038
1.075 ± 0.038
1.062 ± 0.038
1.056 ± 0.038
1.025 ± 0.038
* Meter 1514
** Meter--Unknown
*** Meter 1472
46
-------
Table 19.
RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH
AIR CONDITIONING OFF TO FUEL ECONOMY MEASURED WITH
AIR CONDITIONING ON FOR DYNAMOMETER MEASUREMENTS
OF VEHICLES WITH RADIAL TIRES
BAG1
BAG2
BAGS
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
ASPEN*
1.069 ± 0.027
1.119 ± 0.017
1.093 ± 0.025
1.100 ± 0.012
1.106 ± 0.015
1.084 ± 0.014
—
—
—
—
1.202 ± 0.027
1.160 ± 0.027
1.118 ± 0.027
1.066 ± 0.027
1.070 ± 0.027
1.119 ± 0.027
IMPALA*
1.102 ± 0.027
1.109 ± 0.016
1.089 ± 0.023
1.103 ± 0.012
1.099 ± 0.014
1.111 ± 0.017
--„
—
—
—
—
—
—
—
—
* Meter—Unknown
47
-------
Table 20.
RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH
AIR CONDITIONING OFF TO FUEL ECONOMY MEASURED WITH
AIR CONDITIONING ON FOR DYNAMOMETER MEASUREMENTS
OF VEHICLES WITH BIAS TIRES
BAG1
BAG2
BAGS
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
PACER*
1.099 ± 0.027
1.135 ± 0.019
1.117 ± 0.027
1.121 + 0.013
1.126 ± 0.016
1.120 ± 0.022
—
—
__-
—
1.141 ± 0.027
1.134 ± 0.027
1.106 ± 0.027
1.041 ± 0.027
1.048 ± 0.027
1.019 ± 0.027
ASPEN*
1.081 ± 0.033
1.023 ± 0.022
1.005 ± 0.031
1.032 ± 0.016
1.015 ± 0.019
1.114 ± 0.019
—
—
—
___
—
—
—
—
—
* Meter—Unknown
48
-------
Table 21.
COMPARISON OF RATIOS OF AIR CONDITIONING/ON TO AIR CONDITIONING/OFF MPG
FOR TRACK, DYNAMOMETER AND TIRE TYPE FOR SELECTED DRIVING CYCLES
FTP
HH
HST
30
40
50
60
GRANADA
1.18
—
1.16
--
1.19
--
1.17
--
1.11
—
1.12
--
1.13
--
--
--
1.13
--
1.13
--
1.10
--
1.16
--
1.09
--
1.12
--
KEY;
Track
Dyno
Radic
CHEVETTE
1.10
—
--
--
1.11
--
--
--
1.05
—
--
--
1.12
—
--
--
1.08
--
--
--
1.03
--
--
--
1.00
—
--
--
n Bias
PACER
ASPEN
IMPALA
1.06
--
—
1.12
1.10
--
--
1.11
1.05
--
--
1.04
1.06
--
--
1.05
1.04
--
--
1.02
1.15
--
1.06
--
1.11
--
1.08
--
1.07
--
1.06
--
1.10
--
1.06
--
49
-------
Table 22. RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH AIR CONDITIONING OFF
TO FUEL ECONOMY MEASURED WITH AIR CONDITIONING ON
(Weighted Mean of Dynamometer, Track, Radial and Bias Tire Results)
en
o
BAG1
BAG2
BAGS
FTP
HH
HST
CST
HNO
HRE
HSM
10
20
30
40
50
60
70
80
GRANADA
1.127 ± 0.027
1.184 ± 0.011
1.168 ± 0.017
1.167 ± 0.010
1.177 ± 0.010
1.114 ± 0.013
—
—
—
—
1.164 ± 0.033
1.187 ± 0.033
1.131 ± 0.033
1.133 ± 0.023
1.130 ± 0.023
1.105 ± 0.023
1.126 ± 0.023
1.017 ± 0.023
CHEVETTE
1.081 ± 0.038
1.098 ± 0.022
1.129 ± 0.030
1.101 ± 0.016
1.113 ± 0.013
1.050 ± 0.022
—
—
—
—
—
1.139 ± 0.027
1.119 ± 0.027
1.081 ± 0.027
1.033 ± 0.033
0.995 ± 0.027
1.029 ± 0.027
—
PACER
1.085 ± 0.023
1.101 ± 0.012
1.121 ± 0.020
1.097 ± 0.011
1.114 ± 0.011
1.124 ± 0.016
—
1.070 ± 0.027
1.049 ± 0.027
1.086 + 0.033
1.141 ± 0.027
1.157 ± 0.019
1.101 ± 0.019
1.046 ± 0.019
1.053 ± 0.019
1.031 ± 0.019
1.001 ± 0.027
1.055 ± 0.027
ASPEN
1.075 ± 0.018
1.093 ± 0.010
1.053 ± 0.015
1.077 ± 0.008
1.073 ± 0.009
1.089 ± 0.009
—
—
—
—
1.136 ± 0.016
1.154 ± 0.016
1.115 ± 0.016
1.056 ± 0.016
1.065 ± 0.016
1.065 ± 0.016
—
—
IMPALA
1.067 ± 0.018
1.099 ± 0.010
1.083 ± 0.016
1.088 ± 0.008
1.092 ± 0.010
1.083 ± 0.013
—
—
—
—
1.199 ± 0.038
1.238 ± 0.022
1.147 ± 0.022
1.095 ± 0.022
1.071 ± 0.022
1.087 ± 0.022
1.087 ± 0.022
1.046 ± 0.022
-------
8.8 Air Conditioning Simulation Effect
Air conditioners are not normally operated during vehicle testing
on dynamometers. To simulate the effect of air conditioning on
fuel economy as measured on a dynamometer, the dynamometer road
load at 50 mph is instead increased 10%. The ratios of
fuel economy measured with air conditioning off (i.e., proper road load)
to fuel economy measured with simulated air conditioning (i.e., road
load increased 10%) are presented in Table 23 for both radial and bias
tires. More appropriately, this analysis may be considered to be the
effect on fuel economy due to a 10% increase in dynamometer power
absorption unit setting.
A two-way analysis of variance of the ratios among vehicles ano
driving sequences yields a mean ratio of 1.0087. Thus, a 10% increase
in road load produces on average less than a 1% decrease in fuel
economy. This may be compared to an approximately 10% decrease in
fuel economy in Table 22. The analysis of variance indicated no
significant vehicle-to-vehicle ratio difference. However, a marginally
significant test cycle effect was noted; however, this effect does not
appear to be correlated with average test speed.
51
-------
Table 23
RATIO ± 1 STANDARD ERROR OF FUEL ECONOMY MEASURED WITH
AIR CONDITIONING OFF TO FUEL ECONOMY MEASURED WITH
SIMULATED AIR CONDITIONING FOR DYNAMOMETER MEASUREMENTS
BAG1
BAG2
BAGS
FTP
HH
HST'
CST
HNO
HRE
HSM
10
20
30
40
50
60
DATSUN*
0.996 ± 0.027
1.030 ± 0.017
0.996 ± 0.025
1.014 ± 0.012
1.013 ± 0.015
0.947 ± 0.017
PACER*
0.963 ± 0.033
0.983 ± 0.023
1.018 ± 0.033
0.998 ± 0.016
0.996 ± 0.020
1.016 ± 0.017
0.950 ± 0.027
0.986 ± 0.027
0.954 ± 0.027
0.992 ± 0.027
1.024 ± 0.027
0.993 ± 0.027
ASPEN**
1.020 ± 0.027
1.030 ± 0.017
1.018 ± 0.025
1.025 ± 0.012
1.024 ± 0.015
0.998 ± 1.250
1.208 ± 0.027
1.000 ± 0.027
1.021 ± 0.027
1.027 ± 0.027
1.051 ± 0.027
1.052 ± 0.027
IMPALA**
I
0.971 ± 0.027
1.023 ± 0.016 \
1.021 ± 0.023 i
1.010 ± 0.012
1.022 ± 0.014
1.044 ± 0.017
* Bias Tires
** Radial Tires
52
-------
8.9 Effects of Modified Cycles
Tables 24 and 25 present the computed ratios of the fuel economy
for each modified highway test to the fuel economy of the standard
highway test for dynamometer and track tests, respectively. Note from
the tables that the cold start highway dynamometer and track tests
represent a degradation in fuel economy of about 10% compared to the
standard test. The noisy and redistributed cycle tests impose a 3%-5%
fuel economy penalty on both the dynamometer and the track. The smooth
and 50 mph cruise cycles result in a 4% to 8% fuel economy improvement
over the standard cycle.
In some instances, vehicle to vehicle differences among the ratios
can be statistically inferred both from the dynamometer and track tests.
Even so, we present the mean ratios over all vehicles for each modified
test and note that the mean ratios from dynamometer tests are statistically
undistinguishable from the mean ratios from the track tests. A comparison
of the modified test cycles with the standard highway cycle is presented
in Appendix A.
53
-------
Table 24. RATIO OF MODIFIED HIGHWAY TEST MPG TO STANDARD HIGHWAY TEST MPG FOR DYNAMOMETER TESTS
(Air Conditioner Off)
Datsun
Pinto
Honda
Chevette
Pacer
Aspen
Impala
Mean
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
COLD START
(CST)
0.885 ± 0.021
0.890 ± 0.017
—
0.892 ± 0.019
0.893 ± 0.017
—
—
0.920 ± 0.021
0.940 ± 0.023
0.933 ± 0.022
0.908 ± 0.008
NOISY CYCLE
1.015 ± 0.014
0.981 ± 0.017
0.962 ± 0.016
1.000 ± 0.017
—
0.952 ± 0.015
0.933 ± 0.014
0.966 ± 0.017
0.969 ± 0.015
0.972 ± 0.005
REDISTRIBUTED
CYCLE
1.000 ± 0.014
0.873 ± 0.017
0.964 ± 0.016
1.003 ± 0.017
—
0.930 ± 0.016
0.926 ± 0.013
0.947 ± 0.019
0.988 ± 0.015
0.954 ± 0.006
SMOOTH CYCLE
1.072 ± 0.014
1.034 ± 0.016
1.028 ± 0.016
—
1.046 ± 0.016
1.036 ± 0.014
1.062 ± 0.017
1.034 ± 0.015
1.045 ± 0.006
50 MPH CRUISE
1.083 ± 0.016
1.055 ± 0.017
1.067 ± 0.017
1.067 ± 0.022
1.066 ± 0.019
—
1.063 ± 0.022
1.103 ± 0.021
1.143 ± 0.023
1.091 ± 0.022
1.082 ± 0.007
-------
Table 25. RATIO OF MODIFIED HIGHWAY TEST MPG TO STANDARD HIGHWAY TEST MPG FOR TRACK TESTS
(Air Conditioner Off)
Datsun
Pinto
Honda
Chevette
Pacer
Aspen
Impala
Mean
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
Radial
Bias
COLD START
(CST)
—
0.876 ± 0.027
0.906 ± 0.029
0.804 ± 0.029
0.934 ± 0.038
0.931 ± 0.030
0.937 ± 0.031
0.898 ± 0.012
NOISY CYCLE
0.963 ± 0.017
0.981 ± 0.025
0.965 ± 0.022
0.984 ± 0.025
0.939 ± 0.022
0.965 ± 0.033
0.988 ± 0.033
0.945 ± 0.020
0.985 ± 0.022
0.968 ± 0.008
REDISTRIBUTED
CYCLE
0.935 ± 0.019
0.975 ± 0.025
0.960 ± 0.022
0.963 ± 0.025
0.961 ± 0.022
0.964 ± 0.033
0.977 ± 0.033
0.972 ± 0.019
0.995 ± 0.022
0.967 ± 0.008
SMOOTH CYCLE
1.047 ± 0.019
1.100 ± 0.027
1.061 ± 0.029
1.042 ± 0.025
1.051 ± 0.022
1.061 ± 0.033
1.121 ± 0.038
1.049 ± 0.019
1.071 ± 0.022
1.067 ± 0.008
50 MPH CRUISE
1.093 ± 0.022
—
0.952 ± 0.022
0.906 ± 0.025
1.081 ± 0.029
1.091 ± 0.033
1.211 ± 0.033
1.157 ± 0.030
1.126 ± 0.025
1.077 ± 0.010
-------
8.10 Computed Road Load Horsepower From Coast Downs
Coast-down tests were conducted on the track and dynamometer on
vehicles equipped with bias belted and radial tires. The quantities
that were measured were vehicle direction (i.e., north, south, curve for
track tests), wind speed, wind direction, and time in seconds for the
vehicle to coast from 55 mph to 45 mph. Coast-down tests were also
conducted on the track to measure the effect of the vehicles' windows
being up or down and on the dynamometer to measure the effect of air
conditioning off or simulated. The coast-down results are presented in
Table 26.
Table 26 also presents the calculated Road Load Horsepower (RLHP)
at 50 mph. This quantity is calculated from the coast-down times by the
expression
RLHP = i^tia weight (Ibs) (0>06073)*
coast-down time (sees)
For the track tests, the effect of track grade is eliminated by
averaging the coast-down times for two different track directions (e.g.,
north and south). The RLHP calculated is the total horsepower required
to overcome both rolling and aerodynamic resistance for a vehicle with
a particular inertia weight as tested on the track or dynamometer.
One way of assessing the dynamometer-to-track effect due to
improper RLHP simulation on the dynamometer is to ratio the RLHP
determined from track tests to the RLHP determined from dynamometer
tests. These ratios are presented in Table 27 for radial and bias
tires for tests with air conditioning off and windows up. Note that
the ratio for bias tires is consistently larger than the corresponding
ratio for radial tires for each of the vehicles tested. This is
consistent with the notion that the rolling resistance of radial tires
is less than the rolling resistance of bias tires. Also note that in
all but two instances, the ratios (bias and radial) are less than unity
and this would seem to imply that the track road load horsepower
necessary to overcome rolling and aerodynamic resistance is less than
the dynamometer road load horsepower.
* See Appendix F for derivation of formula,
56
-------
Table 26(a)
MEASURED COAST-DOWN TIMES AND CALCULATED ROAD LOAD HORSEPOWER FOR DYNAMOMETER AND TRACK TESTS
VEHICLE
PINTO
IMPALA
ASPEN
SITE
TRACK
DYNO
#5
TRACK
DYNO
#5
TRACK
DYNO
#5
TEST
WEIGHT
(Ibs)
3150
3000
4869
5000
4318
4000
DIRECTION
N
S
N
S
N
S
W. Curve
E. Curve
N/A
N
S
N/A
N
S
N
S
N/A
TIRE
TYPE
R
B
R
B
R
R
B
R
B
R
B
WIND
SPEED
(mph)
1
6
N/A
3
N/A
6
1
N/A
WIND**
DIRECTION
(deg)
90
335
N/A
272
N/A
328
323
N/A
WINDOWS
UP
DOWN
UP
N/A
UP
N/A
UP
N/A
A/C*
OFF
OFF
OFF
OFF
SIM.
OFF
SIM.
OFF
OFF
SIM.
OFF
SIM.
AVG. TIME
FROM
55 TO 45 MPH
(sees)
13.07
15.23
12.80
14.13
11.83
14.27
12.30
13.10
12.40
13.80
15.00
20.20
14.14
14.00
14.60
13.93
13.86
19.66
14.00
17.46
12.34
14.00
12.93
12.23
CALCULATED
RLHP
(3 50 MPH
13.52
14.21
14.66
15.06
14.69
13.20
16.80
21.47
21.69
20.80
21.80
15.65
16.67
19.6.9
20.47
18.79
19.86
* A/C = Airconditioning
** Relative to North.
-------
Table 26(b)
MEASURED COAST-DOWN TIMES AND CALCULATED ROAD LOAD HORSEPOWER FOR DYNAMOMETER AND TRACK TESTS
en
OO
VEHICLE
GRANADA
PACER
DATSUN
SITE
TRACK
DYNO
#5
TRACK
DYNO
#5
TRACK
DYNO
#5
TEST
WEIGHT
(Ibs)
3978
4000
3776
3500
2497
2250
DIRECTION
N
S
N
S
E. Curve
W. Curve
N/A
N
S
N
S
N
S
N/A
N
S
N
S
N
S
N
S
N/A
TIRE
TYPE
R
B
R
B
R
B
R
B
B
R
R
B
WIND
SPEED
(mph)
5
4.5
N/A
0
4
N/A
6.5
4.5
6.0
7.0
N/A
WIND**
DIRECTION
(deg)
157
20
N/A
0
90
N/A
300
270
300
270
N/A
WINDOWS
UP
N/A
DOWN
UP
UP
N/A
UP
DOWN
UP
DOWN
N/A
A/C*
OFF
OFF
OFF
OFF
SIM.
flFF
Urr
OFF
AVG. TIME
FROM
55 TO 45 MPH
(sees)
14.90
14.00
11,45
11.60
11.60
12.40
13.60
13.87
14.03
14.83
16.03
17.33
15.30
17.27
13.00
13.50
12.80
12.00
12.60
11.53
12.20
13.90
13.00
13.00
11.80
10.77
10.99
CALCULATED
RLHP
(3 50 MPH
16.72
18.66
20.13
17.86
17.51
15.89
13.75
14.08
16.35
15.74
16.61
12.33
12.78
11.27
12.23
12.69
12.43
* A/C = Air Conditioning
** Relative to North
-------
Table 27
RATIO OF RLHP DETERMINED FROM TRACK COAST-DOWN TESTS TO
RLHP DETERMINED FROM DYNAMOMETER COAST-DOWN TESTS
(AIR CONDITIONING OFF/WINDOWS UP)
VEHICLE
PINTO
IMPALA
ASPEN
GRANADA
PACER
DATSUN
TIRE TYPE
BIAS
1.111
—
0.887
1.066
0.895
0.992
RADIAL
0.920
0.782
0.795
0.936
0.841
0.888
RATIO OF TRACK TEST
WEIGHT TO DYNO TEST WEIGHT
1.05
0.97
1.08
0.99
1.08
1.11
59
-------
9.0 DISCUSSION
This test program and analysis attempts to identify, quantify,
and statistically verify the individual parameters contributing to
dynamometer to track fuel economy differences. To this end, the
testing of each vehicle is carefully controlled both for dynamometer
and for track tests to every extent possible.
Each vehicle was inspected and tuned to manufacturers' specifi-
cations before testing began, so that any fuel economy differences due
to vehicle state-of-tune could be eliminated. Also, to the extent
possible, each vehicle was tested on the track at ambient temperatures
within the same range (68°F to 86°F)* as that required by the FTP for
dynamometer tests. Effects of wind and grade, which are not simulated
on dynamometer tests, were compensated for on track tests by conducting
the test cycle in two opposing directions and averaging the resulting
measurements.
Odometer mileage also can affect fuel economy and can contribute to
dynamometer to track variability. The odometer readings for the vehicles
tested ranged from approximately 2000 to 11000 miles. In most cases,
however, there were only a few hundred miles difference between the points
at which the vehicles were tested from dynamometer to track.
The above differences in testing conditions from dynamometer to
track were considered to be small. That is, differences in temperature
and mileage (uncontrolled parameters considered to possibly influence
fuel economy) were judged to be small contributors to fuel economy
variability compared to measurement variability. Thus, no attempts
were made to correct fuel economy for vehicle mileage or ambient
temperature.
Fuel economy measured on the dynamometer is normally calculated
by the carbon balance method. In this study, it was determined that
the differences between meter fuel consumption and carbon balance fuel
consumption were a function of the particular meter used as well as
the magnitude of fuel consumption. Therefore, comparisons between
fuel economy on the track and dyno were always made using the same or
equivalently adjusted meter (i.e., for purposes of presentation meter
#1514 was arbitrarily chosen and fuel consumptions measured with
different meters were corrected by whatever the offset was determined
to be between it and meter 1514).
In a few instances, tests were conducted at ambient temperatures
as low as 50°F, but never above 86 F.
60
-------
Dynamometer measured fuel economy divided by track measured fuel
economy provides a measure of the dyno/track effect. As determined in
the analysis, no statistically significant differences between the ratios
computed for air conditioning on and air conditioning off are detectable.
However, vehicle to vehicle differences between ratios do exist. Further,
there is a difference between ratios due to tire type (i.e., radial and
bias belted). If we compare the FTP ratios presented in Table 28
it may be noted that fuel economy as measured on the dynamometer is greater
than the fuel economy measured on the track for all cases. Except for
the Honda, the ratio is larger for the vehicle tested with bias tires
as compared to the same vehicle tested with radial tires. We note two
factors that may be responsible for the reverse effect in the Honda.
First, the Honda is the only front-wheel drive vehicle in the group, and
second, the Honda was tested with 12" bias tires and 13" radial tires.
Table 28.
COMPARISON OF DYNAMOMETER TO TRACK FUEL
ECONOMY RATIOS AS MEASURED OVER THE FTP
(Mean Ratio ±1 Standard Error)
TIRE TYPE
Radial
Bias
PINTO
1.05U0.014
1.106±0.015
HONDA
1.114±0.011
1.097±0.013
PACER
—
1.057±0.013
ASPEN
1.086±0.010
1.140±0.014
Table 29 presents the ratios of fuel economy as measured with radial
tires to the fuel economy as measured with bias tires for both dyna-
mometer and track FTP tests.
Note in the table, that the ratios computed for dynamometer tests
are all less than unity except for the Honda. This seems to imply that
fuel economy of a vehicle measured on a dynamometer is less if it is
equipped with radial tires as compared to bias belted tires. Another way
of saying the same thing is that the rolling resistance of radial tires
is greater than the rolling resistance of bias tires when tested on the
dynamometer.
61
-------
Table 29
COMPARISON OF THE RATIOS OF FUEL ECONOMY MEASURED WITH
RADIAL TIRES TO FUEL ECONOMY MEASURED WITH BIAS TIRES
FOR DYNAMOMETER AND TRACK
(Mean Ratios ±1 Standard Error)
VEHICLE
Pinto
Honda
Datsun
Chevette
Pacer
Aspen
Impala
Granada
DYNAMOMETER
0.967 ± 0.012
1.022 ± 0.010
0.984 ± 0.010
—
—
0.992 ± 0.009
0.996 ± 0.012
—
TRACK
1.018 ± 0.017
1.006 ± 0.014
1.005 ± 0.014
1.030 ± 0.016
—
1.057 ± 0.015
1.080 ± 0.010
0.970 ± 0.013
For track tests, it may be noted from Table 29 that the ratios are
greater than unity (except for the Granada). This implies that for
track tests fuel economies for vehicles equipped with radial tires are
greater than fuel economies for vehicles equipped with bias tires
(i.e., rolling resistance is greater for bias tires than for radial
tires on track tests).
Another way to assess and compare the ratios in Tables 28 and 29,
is to compute the ratios of the ratios. For example,
Table 28 compares the ratios of dynamometer fuel economy to track fuel
economy.for vehicles with radial tires (DR/TR) and for vehicles with
bias tires (DB/Tg>. The ratio of these two ratios may be written:
VTR
VTB
V°B
VTB
Note that (DR/DB)/(TR/TB) is exactly the ratio of the ratios presented
in Table 29. On the other hand, it is observed in Table 30 that the two
alternatively calculated ratios of the ratios are not exactly equal.
This is explained by the fact that in some cases a different number of
tests were available for the dynamometer to track comparisons than were
available for radial to bias tire comparisons on the same vehicle.
62
-------
Table 30.
COMPARISON OF THE RATIO OF RATIOS BY TWO METHODS
Pinto
Honda
Datsun
Aspen
Impala
VDB
VTB
0.950 ± 0.021
1.016 ± 0.017
0.979 ± 0.019
0.939 ± 0.017
0.922 ± 0.016
°R/TR
°B/TB
0.950 ± 0.021
1.015 ± 0.019
—
0.953 ± 0.017
—
Because the same meter was not always used to measure both dynamometer
and track fuel consumptions, fewer comparisons could be made, in general,
between the fuel economies from dynamometer to track than between fuel
economies from radial to bias tires.
If the relative tire/track interactions of radial and bias tires
were properly simulated by the dynamometer, then the dynamometer-to-track
MPG ratio for radial tires would equal the dynamometer-to-track MPG
ratio for bias tires (i.e., the ratio of the ratios would be unity).
From Table 30 note that this is not true. In most cases, the ratio of
the ratios is less than unity, and the magnitude of deviations is as much
as 8%. The implication is that the relatively higher fuel economy
achieved on the average with radial tires on the track is not reproduced
on the dynamometer.
A previous study of tire-surface interaction by Burgeson6 sheds
some light on reasons for the discrepancy between dynamometer and track
results. Burgeson's study investigated the rolling resistive forces on
29 pairs of tires ranging in size from BR78xl3 to LR78xl5 and consisting
of radial, bias belted, and bias ply construction. The pairs of tires
were tested on a small twin-roll dynamometer (r ~ 5") and on a large
single-roll dynamometer (r -24"). No aerodynamic losses were simulated
(i.e., no PUA settings). The power absorbed by the dynamometers due to
only rolling resistive losses were calculated from coast-down times on
both the large and small roll dynamometers.
63
-------
It is generally assumed in the dynamometer test procedure that
the power absorbed by a tire (inflated to 45 psi) on the dynamometer
is twice that of the tire (inflated to a typical 26 psi) on the road.
That is, one might expect a rolling resistive force, FR, measured
on the dual small roll dynamometer (at 45 psi) to be twice that
force measured on a flat surface (at 26 psi).
The rolling resistance determined from measurements with two tires
at 45 psi on a small-roll Clayton Dynamometer was compared to the
rolling resistance determined from corrected results on the large roll
dynamometer. The results are reproduced in Table 31 and show that the
ratio R£ of the mean rolling force on the small roll dynamometer at
45 psi to the corrected mean rolling force on a flat surface for
different tire types is less than the expected factor of two and varies
by tire type. From the table, note that radial tires come closest to
producing a ratio of 2. In general, it may be inferred from Burgeson's
results that the Clayton twin-roll dynamometer underloads vehicles (i.e.,
the force due to rolling resistance measured on the dynamometer is less
than that actually measured on the road). Furthermore, this dynamometer
underloading effect is more severe for bias belted tires than for radial,
which is in qualitative agreement with Table 30.
Table 31.
RATIO (RC) OF THE MEAN HORSEPOWER (PR) DUE TO ROLLING RESISTANCE
MEASURED ON A SMALL TWIN-ROLL DYNAMOMETER TO THE MEAN HORSEPOWER
DUE TO ROLLING RESISTANCE MEASURED ON A LARGE ROLL DYNAMOMETER
AND CORRECTED TO ROAD*
Tire Type
Radial
Bias
Belted Bias
Clayton
(Tires at 45 psi)
P Clayton (hp)
K
7.67
6.99
7.81
Large Roll
Corrected to Road
(Tires at 26 psi)
PD Road (hp)
K
4.15
5.04
5.25
,PD Clayton
n - K .
1XC PD Road
K
1.85
1.39
1.49
* Extracted from Reference 6.
64
-------
The results in Table 31 should be viewed qualitatively inasmuch as
the magnitude of the ratio, RC, obtained by Burgeson may not be correct
for all tire/vehicle combinations. The reason for this is discussed by
Burgeson. Radial and bias tires exhibit ranges of rolling resistance
characteristics that may vary by tire manufacturer and vehicle configuration,
There may be high and low rolling resistance radial and bias tires and
tire-track surface interactions may be different from tire-dynamometer
surface interactions.
Consistent with the above, the dynamometer to track MPG ratios
computed in this study are seen to vary significantly from vehicle to
vehicle. The vehicle-to-vehicle effect is more appropriately defined
as a vehicle/tire configuration effect.
In addition to the contributions that rolling resistance variations
make to fuel economy differences are the contributions of aerodynamic
resistance. Newell7 has investigated the extent to which manufacturer
supplied PAU settings (i.e., aerodynamic resistive force) agreed with
aerodynamic forces measured on ten production vehicles. In this program,
vehicles were chosen for test if their manufacturer supplied PAU settings
were atypically low compared to PAU settings for other similar vehicles.
Vehicle road load horsepowers (aerodynamic and rolling resistance
contributions) were determined from coast-down tests on a test track.
The RLHPs were corrected to an ambient air temperature of 68°F and
barometric pressure of 29.00 inches Hg. The vehicle was then set up on a
twin small-roll dynamometer and the PAU was set to a value that reproduced
the same coast-down time that was measured on the test track. The PAU
values obtained in this way were compared with the PAU values submitted
by the manufacturer for that vehicle. The manufacturer and test
determined PAU settings in horsepower are reproduced in Table 32.
From Table 32, note that the manufacturers' recommended PAU settings
are consistently lower than those measured from the production vehicles
(except for the Omni, a front-wheel drive vehicle). Also presented in
Table 32 are the total RLHP calculated from coast-down times in Newell's
tests. The difference between total RLHP and PA (the PAU setting) is
the implied power dissipated due to rolling resistance. The calculated
values range from 4.0 to 8.0 HP and do not compare with the power dissi-
pation results due to rolling resistance computed by Burgeson in Table 31
and which range from 8.3 to 10.5 HP.
65
-------
Table 32
COMPARISON OF DYNAMOMETER POWER ABSORBER (PA) SETTINGS IN HP*
01
CTl
'79 VEHICLE
Fiesta
Omni
Monza
Granada
Firebird
Lebaron
Corvette
Eldorado
Trans Am
Olds '98
PA MFR.
(PAU)
7.3
7.8
8.1
10.1
8.8
10.8
8.0
9.6
9.5
11.6
PA STUDY
(PAU)
8.05
7.8
11.3
12.6
10.0
11.6
9.4
10.0
9.9
12.2
PT
TOTAL
RLHP
(MFR)
12.2
12.7
--
13.7
1 14.9
16.3
_-
| 16.4
15.3
18.1
j
PT
TOTAL
RLHP
(STUDY)
12.0
11.8
15.9
17.8
14.3
16.9
17.4
17.4
14.4
18.2
PR
IMPLIED ROLLING RESISTANCE
(TOTAL RLHP- PAU) STUDY
3.95
4.0
4.6
5.2
4.3
5.3
8.0
7.4
4.5
6.0
* Extracted, in part, from Reference 7.
-------
There are several possible reasons for the apparent discrepancy in
power dissipation measurements and calculations due to rolling resistance.
The first and most obvious reason for the differences in rolling resistance
has previously been discussed and refers to the wide range of rolling
resistance characteristics possible for both radial and bias tires.
Second, Burgeson's estimates of track rolling resistance were made
by testing tires on a large roll dynamometer (r -24") at 45 psi. He
had to correct his results to account for roll curvature and tire pressure.
Klingbeil8 has shown that the curvature correction formula most often used
(due to Clark9 and used by Burgeson) does not correctly account for
curvature due to thermal effects. If this is the case, Burgeson's absolute
estimates of track rolling resistance are too high.
Third, Newell's estimates of the contribution of aerodynamic resistive
forces seem to be too large a fraction of total road load horsepower
(e.g., 54% to 71%). Newell's estimates of aerodynamic forces are higher
than the manufacturers' estimates even though his estimates of total road
load horsepower at 50 mph are consistent with manufacturer supplied total
road load horsepower. Newell cites tire-surface interaction effects and
possible dynamometer calibration differences as possible reasons for the
observed differences between his test-determined PAU settings and those
submitted by the manufacturer.
Results of coast down tests on six of the eight vehicles in this
test program indicate that total road load horsepower at 50 mph (RLHP)
is, in general, lower on track tests than on dynamometer tests. This is
exactly opposite what would be expected on the basis of fuel economy
comparisons. Nevertheless, the relative relationship of the imputed
rolling resistance of radial-to-bias tires on the track as compared to
that on the dynamometer is consistent with the fuel economy ratio of
ratios presented in Table 30. However, since we cannot accurately resolve
the contributions of rolling and aerodynamic forces for these vehicles
tested, we cannot completely account for the RLHP differences from track-
to-dynamometer tests.
Recent studies by Yurko10 and Gugett11 have shown another possible
influence on vehicle fuel economy as measured on a dynamometer. Yurko
and Grugett have shown that there is a velocity difference (i.e., a slip)
between the front and rear rolls of a small twin-roll dynamometer due to
tire deformation. The effective tire radius on the rear roll is greater
than the effective tire radius on the front roll. Therefore the rotational
velocity of the front roll is less relative to the rear roll.
67
-------
As is presently the case for a small twin-roll dynamometer, the major
tractive load imposed on the vehicle is applied at the front roll. The
rear roll is presently uncoupled from the front roll and is used to
determine speed. Since the fuel economy, as calculated over a specified
driving sequence, is dependent on the speed of (and distance traveled
by) the rear roll, fuel economy estimates are greater than they would be
if speed was measured from the front roll.
Results of testing by Yurko with one 1978 Mercury Montego indicate
that the velocity differences between the rolls were least when the rolls
we*-e coupled (e.g., a -0.22%*'velocity difference for radial tires and a
0.40% velocity difference for bias tires). Coast-down tests with radial
tires indicated that the coupling of the rolls resulted in a 2% to 6%
increase in measured fuel consumption rate as compared to the case when
the rolls were uncoupled.
Grugett measured the fuel consumption differences due to the coupling
of the dynamometer rolls as compared to the uncoupled case over the urban
and highway driving cycles. Tests were conducted with one 1979 Chevrolet
Nova on a test track, on a small twin-roll dynamometer with rolls uncoupled,
and on a small twin-roll dynamometer with the rolls coupled. Tests showed
that the uncoupled dynamometer tests overestimated fuel economy by about
10% over track tests. Coupled dynamometer tests overestimated fuel
economy by about 4%.
Additional studies are needed to verify the vehicle tire slip
influence on fuel economy as measured on a dynamometer. Preliminary
investigations indicate that coupling of the front and rear rolls of the
dynamometer might account for as much as 6% of the approximate 10%
difference in fuel economy measured between dynamometer and track. Tests
need to be conducted on a test track, and on a coupled and uncoupled
dynamometer using different size and technology vehicles (i.e., front
and rear wheel drive), and different tire types.
Additional investigations within the present study indicate that
the use of air conditioning results in an increase in fuel consumption
of from 7% to 18% measured over the FTP urban cycle. The increase
in fuel consumotion due to the use of air conditioning is independent
of track or dynamometer testing and of tire type. However, the increase
in fuel consumption does vary significantly from vehicle to vehicle.
The rotational velocity of the front roll was 0.22% larger than
the rear roll.
68
-------
At present, the impact on fuel economy due to air conditioning is
simulated on the dynamometer by increasing the dynamometer road load
(PAD) at 50 mph by 10%. This study found that the dynamometer simulation
of air conditioning did not produce any significant change in measured
fuel economy. Dynamometer simulated air conditioning is not a good
indication of the effect on fuel economy due to the use of air conditioning
in actual practice.
Finally, effort was expended in this study to determine the extent
to which different types of driving, similar to highway driving, affected
vehicle fuel economy. Public criticism over the EPA estimated highway
fuel economy of vehicles has raised doubts as to whether the highway
estimate is attainable. Tests in the study over modified highway cycles
demonstrate highway fuel economies that are as much as 10% lower or 8%
higher than the fuel economies estimated over the standard EPA highway
cycle. The tests demonstrated that highway type driving characterized by
smooth steady driving resulted in a highway fuel economy approximately 6%
larger than the EPA estimate. Driving at a constant 50 mph resulted in
an 8% increase in fuel economy over the EPA highway cycle fuel economy. On
the other hand, highway type driving characterized by a greater percentage
of time either accelerating/decelerating or at speeds above 60 mph resulted
in significant decreases in fuel economy of about 3-4% compared to EPA
estimates. Cold start highway fuel economy was about 9%-10% lower than
EPA highway cycle fuel economy. In all cases, the dynamometer produced
statistically equivalent effects on fuel economy due to the modified cycles
as those produced on track tests.
69
-------
REFERENCES
1 Technology Assessment and Evaluation Branch, ECTD, OMSAPC, EPA,
"Passenger Car Fuel Economy—Dynamometer vs. Track vs. Road,"
Report 76-1, August 1975.
2 D. Turton, "Fuel Consumption Measurements—Carbon Balance vs. Flow
Meter," EPA Technical Report, SDSB79-28, July 1979.
3 T. Newell, "Carbon Balance and Volumetric Measurements of Fuel
Consumption," EPA Technical Report, SDSB80-05, April 1980.
4 S. Kaufman, "Individual Manufacturer Procedures to Establish Fuel
Economy Adjustment Factors," Falcon Research and Development Company,
Report No. 3520-4/BUF-42, Appendix A, February 1981.
5 F. P. Hutchins and J. Kranig, "An Evaluation of the Fuel Economy
Performance of Thirty-one 1977 Production Vehicles Relative to Their
Certification Counterparts," EPA Report 77-18FPH (TAEB), January 1978.
6 Richard N. Burgeson, "Tire-Dynamometer Roll Effects," EPA Technical
Report LDTP-77-4, March 1978;
Richard N. Burgeson, "Clayton Dynamometer-to-Road Tire Rolling
Resistance Relationship," EPA Technical Report LDTP-78-09, April 1978.
7 Terry Newell, "Independent Coast-Down Road Load Power Determination
for Ten Diverse Production Vehicles," EPA Technical Report SDSB-80-15,
August 1980.
8 W. W. Klingbeil, "Theoretical Prediction of Test Variable Effects,
Including Twin Rolls, on Rolling Resistance," SAE Paper 800088,
February 1980.
9 S. K. Clark, "Rolling Resistance Forces in Pneumatic Tires,"
Dept. of Transportation, UM-013658-1-1, DOT-TSC-76-1, January 1976.
10 John Yurko, "Computer Simulation of Tire Slip on a Clayton Twin Roll
Dynamometer," EPA Technical Report SDSB-79-10, February 1979;
John Yurko, "A Track to Twin Roll Dynamometer Comparison of Several
Different Methods of Vehicle Velocity Simulation," EPA Technical
Report SDSB-79-26, June 1979.
11 Bruce Grugett, "Vehicle Fuel Economy Track vs. Dynamometer," EPA
Technical Report SDSB-80-8, June 1980.
70
-------
APPENDIX A
COMPARISON OF MODIFIED AND STANDARD HIGHWAY CYCLES
71
-------
APPENDIX A
Table A-l
COMPARISON OF MODIFIED AND STANDARD HIGHWAY CYCLES
Distance, Miles
Time, Seconds
Average Speed, mph
Minimum mph*
Maximum mph
Stops per Mile
STANDARD
CYCLE
10.24
765
48.2
28.4
59.5
0.098
SMOOTH
CYCLE
10.23
765
48.1
50.0
50.0
0.098
NOISY
CYCLE
10.26
765
48.3
25.1
63.0
0.097
REDISTRIBUTED
CYCLE
10.56
765
49.7
18.1
72.5
0.095
PERCENT TIME IN SPEED RANGES
Idle
0-10 mph
10-20 mph
20-30 mph
30-40 mph
40-50 mph
50-60 mph
60-70 mph
> 70 mph
0.5
2
1
2
8
41
46
0
0
0.5
2
1
1
1
3
92
0
0
0.5
2
1
2
9
38
46
2
0
0.5
2
1
3
10
25
40
16
2
* Excluding initial acceleration and final deceleration.
72
-------
Table A-2
DISTRIBUTION OF TIME SPENT IN
ACCELERATION AND SPEED RANGES:
Standard EPA Highway Cycle
ACCELERATION RATE
(MPH/sec)
Total % of Time
in Speed Range
0-10 10-20
SPEED (MPH)
20-30 30-40 40-50
1.8
1.1
2.0
7.7
40.8
50-60
3.6
3.0
2.4
1.8
1.2
0.6
0
0
-0.6
-1.2
-1.8
-2.4
-3.0
-3.6
-4.2
-4.8
... 4.2
... 3.6
... 3.0
... 2.4
... 1.8
... 1.2
... 0.6
Zero
... -0.6
... -1.2
... -1.8
... -2.4
... -3.0
... -3.6
... -4.2
... -4.8
... -5.4
2 3
1 2
1 1
3
1
4 1
1
1 2
3
1 3 1
2 1 2
1
1
4
1
15
19
6
7
3
3
7
73
103
100
21
4
3
1
1
57
141
151
6
1
46.7
73
-------
Table A-3
DISTRIBUTION OF TIME SPENT IN
ACCELERATION AND SPEED RANGES:
Smooth Highway Cycle
ACCELERATION RATE
(KPH/sec)
0-10 10-20
SPEED (HPH)
20-30 30-40
40-50 50-60
3.6
3.0
2.4
1.8
1.2
0.6
0
0
-0.6
-1.2
-1.8
-2.4
-3.0
-3.6
-4.2
-4.8
... 4.2
... 3.6
... 3.0 231
... 2.4 2
... 1.8 1 232
... 1.2 4 6
... 0.6 3 1
Zero 4 702
... -0.6 6
... -1.2 1 3
... -1.8 3 2
... -2.4 1 3 1
... -3.0 2 1 2
... -3.6 1 3
... -4.2
... -4.8
... -5.4
Total % of Time
in Speed Range
1.8
0.9
1.2
1.3
2.9
91.8
74
-------
Table A-4
DISTRIBUTION OF TIME SPENT IN
ACCELERATION AND SPEED RANGES:
Noisy Highway Cycle
ACCELERATION RATE
SPEED (MPH)
(MPH/sec)
3.6
3.0
2.4
1.8
1.2
0.6
0
0
-0.6
-1.2
-1.8
-2.4
-3.0
-3.6
-4.2
-4.8
... 4.2
... 3.6
... 3.0
... 2.4
... 1.8
... 1.2
... 0.6
Zero
... -0.6
... -1.2
... -1.8
... -2.4
.. . -3.0
... -3.6
... -4.2
... -4.8
... -5.4
0-10 10-20 20-30
1 2
1
3
1
1 1
2
7
1 1
2
2 2
1 1 1
2 1 1
1 1
1
30-40
1
2
1
7
16
10
14
6
4
2
1
1
1
1
40-50
9
24
59
62
93
23
9
3
2
1
1
1
2
50-60 60-70
19 1
67 3
110 5
128 6
24 3
5
1
Total % of Time
in Speed Range
1.8
0.9
2.1
37.8
46.3
2.3
75
-------
Table A-5
DISTRIBUTION OF TIME SPENT IN
ACCELERATION AND SPEED RANGES:
Redistributed Highway Cycle
ACCELERATION RATE
(MPH/sec)
-3.6 ... -4.2
-4.2 ... -4.8
-4.8 ... -5.4
Total % of Time
in Speed Range
0-10 10-20 20-30
SPEED (MPH)
30-40 40-50
50-60 60-70 70-80
3.6
3.0
2.4
1.8
1.2
0.6
0
0
-0.6
-1.2
-1.8
-2.4
-3.0
... 4.2
... 3.6
... 3.0
... 2.4
... 1.8
... 1.2
... 0.6
Zero
... -0.6
... -1.2
... -1.8
... -2.4
... -3.0
... -3.6
2 3
1
1
1
4 1
2
1 2
3
1 3
2 1
2
5
3
1
1
4
4
1
2
1
1
8
16
19
25
4
3
9
40
55
64
18
5
1
1
83 17
95 56
112 49
11 3
2
1
7
6
1
1.8 1.8
3.3
9.9 25.1 39.8 16.3
1.8
76
-------
APPENDIX B
TEST VEHICLE-DESCRIPTIONS
77
-------
APPENDIX B
TEST VEHICLE-DESCRIPTIONS
1. CHASSIS MODEL YEAR MAKE - 1976 Honda CVCC Civic
EMISSION CONTROL SYSTEM - Honda CVCC
Engine
Type . 4-stroke prechamber, stratified charge,
spark ignited, single OHC, in-line
4 cyl.
Bore x Stroke . 2.91 x 3.41 in./74 x 86.5 mm
Displacement 90.8 CID/1488 cc
Compression Ratio 7.9:1
Maximum Power at rpm , 60 hp kW at 5000 rpm
Fuel Metering Single carburetor with progressive 2 bbl
for combustion chamber and 1 bbl for pre-
chamber
Fuel Requirement 91 RON
Drive Train
Transmission Type 4 speed manual
Final Drive Ratio ... 3.875:1
Chassis
Type Unitized body, front transverse mounted
engine, front wheel drive
Tire Size OEM Goodrich 6.005x12 and OEM Michel in
155SRxl3
Curb Weight 1795 lb/815 kg
Inertia Weight ..... 2000 lb/910 kg
Passenger Capacity Four
78
-------
Emission Control System
Basic Type Prechamber stratified charge with
thermal reactor and PCV
Mileage on Vehicle 5,460 miles
79
-------
2. CHASSIS MODEL YEAR/MAKE - 1976 Datsun B-210
EMISSION CONTROL SYSTEM - EGR, Air Injection
Engine
Type 4-stroke Otto Cycle, OHV, in-line,
4 cyl.
Bore x Stroke 2.99 x 3.03 in./76 x 77 mm
Displacement ..... 85 cu. in./1397 cc
Compression Ratio 8.5:1
Maximum Power at rpm . . 80 hp/60 kW at 6000 rpm
Fuel Metering .......... Single progressive 2 bbl carburetor
Fuel Requirement . 91 RON low lead
Drive Train
Transmission Type ........ 4 speed manual
Final Drive Ratio 3.89:1
Chassis
Type ...... .... Unitized body, front engine, rear wheel
drive
Tire Size ... .... OEM Toyo 155SRxl3 and OEM Bridgestone
155x13
Curb Weight ..... 1965 lb/890 kg
Inertia Weight .......... 2250 lb/1020 kg
Passenger Capacity ... Four
Emission Control System
Basic Type EGR, PCV, air injection
Mileage on Vehicle 3,600 miles
80
-------
3. CHASSIS MODEL YEAR/MAKE - 1976 Ford Pinto
EMISSION CONTROL SYSTEM - Catalyst, EGR, Air Injection
Engine
Type 4-stroke, Otto cycle, OHC, in-line,
4 cyl.
Bore x Stroke 3.78 x 3.13 in.796.0 x 79.5 mm
Displacement ........... 140 cu. in./2300 cc
Compression Ratio ... 9.0:1
Maximum Power at rpm ....... 92 hp/69 kW at 5000 rpm
Fuel Metering . . . Single 2 bbl carburetor
Fuel Requirement 91 RON unleaded
Drive Train
Transmission Type . 3 speed automatic
Final Drive Ratio .. 3.18:1
Chassis
Type ....... Unitized body, front engine, rear wheel
drive
Tire Size . . OEM Goodyear A78xl3 and OEM Goodyear
BR78xl3
Curb Weight 2587 lb./1175 kg
Inertia Weight . 3000 Ib.71360 kg
Passenger Capacity ........ Four
Emission Control System
Basic Type Single monolith noble metal catalyst,
EGR5 PCV, air injection
Mileage on Vehicle 10,220 miles
81
-------
4. CHASSIS MODEL YEAR/MAKE - 1976 AMC Pacer
EMISSION CONTROL SYSTEM - EGR
Engine
Type 4-Stroke Otto Cycle, OHV, in-line,
6 cyl.
Bore x Stroke 3.75 x 3.50 in./95 x 89 mm
Displacement 232 CID/3802 cc
Compression Ratio . 8.0:1
Maximum Power at rpm ....... 90 hp/67 kW at 3050 rpm
Fuel Metering .......... Single one bbl carburetor
Fuel Requirement 91 RON
Drive Train
Transmission Type . 3 speed automatic
Final Drive Ratio . 3.08:1
Chassis
Type ............... Unitized body, front engine, rear wheel
drive
Tire Size OEM Goodyear DR70xl4 and OEM Goodyear
6.95x14
Curb Weight 3330 lb/1510 kg
Inertia Weight 3500 lb/1590 kg
Passenger Capacity Five
Emission Control System
Basic Type EGR, PCV
Mileage on Vehicle . 4,940 miles
82
-------
5. CHASSIS MODEL YEAR/MAKE - 1976 Ford Granada
EMISSION CONTROL SYSTEM - Catalyst, EGR, Air Injection
Engine
Type .............. 4-stroke Otto cycle, OHV, in-line,
6 cyl.
Bore x Stroke 3.68 x 3.91 in./93 x 99 mm
Displacement .......... 250 CID/4100 cc
Compression Ratio ....... 8.0:1
Maximum Power at rpm ...... 86 hp/64 kW at 3000 rpm
Fuel Metering ......... Single one bbl carburetor
Fuel Requirement ........ 91 RON unleaded
Drive Train
Transmission Type ....... 3 speed automatic
Final Drive Ratio . 3.07:1
Chassis
Type .............. Unitized body, front engine, rear wheel
drive
Tire Size ........... OEM Goodyear DR78xl4 and OEM Goodyear
C78xl4
Curb Weight .......... 3490 lb./1585 kg
Inertia Weight .... 4000 1b./1820 kg
Passenger Capacity Five
Emi ssi on Contro1 Systern
Basic Type ... . Single monolith noble metal catalyst,
secondary air injection, EGR5 PCV
Mileage on Vehicle ....... 4,940 miles
83
-------
6. CHASSIS MODEL YEAR/MAKE - 1976 Dodge Aspen Wagon
EMISSION CONTROL SYSTEM - Catalyst, EGR
Engine
Type 4-stroke Otto, OHV, in-line,
6 cyl.
Bore x Stroke . . 3.40 x 4.12 in./86 x 105 mm
Displacement ........... 225 CID/3687 cc
Compression Ratio . , 8.4:1
Maximum Power at rpm 100 hp/75 kW at 3600 rpm
Fuel Metering Single one bbl carburetor
Fuel Requirement ......... 91 RON unleaded
Drive Train
Transmission Type 3 speed automatic
Final Drive Ratio .. 2.94:1
Chassis
Type Unitized body, front engine, rear wheel
drive
Tire Size OEM Goodyear FR78xl4 and OEM Goodyear
E78xl4
Curb Weight 3811 lb/1730 kg
Inertia Weight 4000 lb/1820 kg
Passenger Capacity . Six
Emission Control System
Basic Type Dual element monolith noble metal
catalyst, EGR, PCV
Mileage on Vehicle . 4,360 miles
84
-------
7. CHASSIS MODEL YEAR/MAKE - 1976 Chevrolet Impala
EMISSION CONTROL SYSTEM - Catalyst, EGR
Engine
Type 4-stroke, Otto cycle, OHV, V-8
Bore x Stroke 4.00 x 3.48 in./101.6 x 88.4 mm
Displacement 350 cu. in./5735 cc
Compression Ratio 8.5:1
Maximum Power at rpm
Fuel Metering Single two bbl carburetor
Fuel Requirement 91 RON unleaded
Drive Train
Transmission Type 3 speed automatic
Final Drive Ratio 2.73:1
Chassis
Type Body/frame, front engine, rear wheel
drive
Tire Size OEM Goodrich HR78xl5 and OEM Goodrich
H78xl5
Curb Weight 4266 lb./1935 kg
Inertia Weight 5000 lb./2270 kg.
Passenger Capacity Six
Emission Control System
Basic Type Single pelletted noble metal catalyst,
EGR, EFE, PCV
Mileage on Vehicle 4,190 miles
85
-------
8. CHASSIS MODEL YEAR/MAKE - 1976 Chevrolet Chevette
EMISSION CONTROL SYSTEM - Catalyst, EGR, Air Injection
Engine
Type 4-stroke, Otto cycle, OHV, in-line,
4 cyl.
Bore x Stroke 3.23 x 2.61 in.
Displacement 58 cu. in./1400 cc
Compression Ratio 8.5:1
Maximum Power at rpm 52 hp at 5300 rpm
Fuel Metering 1 ME single bbl carburetor
Fuel Requirement 91 RON unleaded
Drive Train
Transmission Type 3 speed automatic
Final Drive Ratio
Chassis
Type Body/frame, front engine, rear wheel
drive.
Tire Size OEM Goodyear 155/800R13
Curb Weight 1950 lb/1091 kg
Inertia Weight 2250 lb/1227 kg
Passenger Capacity Four
Control System
-------
APPENDIX C
RESULTS OF FUEL ECONOMY MEASUREMENTS
FOR DYNAMOMETER AND TRACK TESTS
87
-------
APPENDIX C
RESULTS OF FUEL ECONOMY MEASUREMENTS
FOR DYNAMOMETER AND TRACK TESTS
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Honda, CVCC
Radial 45 psi
Off
#1514
LOCATION: Dyno #5
VEHICLE: 76 Honda, CVCC
TIRE: Bias 45 psi
A/C: Off
METER: #1514
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
4
4
2
2
3
3
4
2
2
2
2
2
2
MEAN FUEL
ECONOMY
28.02
28.22
32.13
29.13
30.06
40.16
35.83
40.15
40.27
41.30
19.00
33.11
43.39
49.05
42.82
35.68
COV
PERCENT*
0.40
1.13
3.33
0.63
0.34
1.43
2.11
1.57
2.87
4.74
4.27
•4.61
2.92
4.52
NUMBER OF
REPLICATIONS
3
4
6
3
2
MEAN FUEL
ECONOMY
28.11
27.43
31.18
28.50
29.07
40.77
36.40
19.26
33.47
43.82
49.77
43.33
36.14
COV
PERCENT*
0.61
2.21
2.26
0.68
0.87
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
-------
LOCATION: Dyno #5 and #207
VEHICLE: 76 Datsun
TIRE: Radial 45 psi
A/C: Off
METER: 2099 Corrected + 1514
LOCATION: Dyno #5 and #207
VEHICLE: 76 Datsun
TIRE:
A/C:
METER:
Bias 45 psi
Off
2099 Correc
1513 Corrected
TEST TYPE
BAG1
BAG2
BAGS
FTP
r 1 r
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
3
4
6
4
1
3
3
3
2
2
2
2
2
2
MEAN FUEL
ECONOMY
24.62
25.54
28.90
26.16
27.12
37.97
33.61
38.53
37.96
40.69
18.94
29.06
38.92
46.72
41.13
34.66
COV
PERCENT*
3.37
1.16
3.03
3.765
1.60
1.87
0.95
0.40
1.36
1.04
-0.06
1.67
0.01
NUMBER OF
REPLICATIONS
2
3
3
3
2
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
25.42
25.92
29.07
26.59
27.40
38.95
34.68
38.21
34.00
19.69
30.33
40.86
48.79
41.10
35.80
COV
PERCENT*
0.23
1.80
1.44
1.00
2.58
0.45
1.69
1.62
0.75
0.29
0.42
0.00
0.00
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
89
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
LOCATION: Dyno 207
VEHICLE: 76 Datsun
TIRE: Bias 45 psi
A/C: Simulated
METER: Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
NUMBER OF
REPLICATIONS
2
2
2
2
MEAN FUEL
ECONOMY
25.51
25.16
29.20
26.21
27.06
41.13
COV
PERCENT*
0.20
0.37
2.25
0.14
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
90
-------
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno 207
76 Chevette
Radial 45 psi
Off
Unknown
LOCATION: Dyno 207
VEHICLE: 76 Chevette
TIRE:
A/C:
METER:
Bias 45 psi
Off
Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
1
1
1
1
1
1
MEAN FUEL
ECONOMY
25.94
39.45
34.80
35.11
32.55
28.24
cov
PERCENT*
NUMBER OF
REPLICATIONS
2
2
2
1
MEAN FUEL
ECONOMY
19.56
24.26
25.36
23.36
24.78
30.55
COV
PERCENT*
0.36
0.44
0.25
1
I
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
91
-------
LOCATION; Dyno #5
VEHICLE: 76 Pinto
TIRE: Radial 45 psi
A/C: Off
METER: 1514
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Pinto
Bias 45 psi
Off
1514
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
3
2
2
2
2
2
2
MEAN FUEL
ECONOMY
16.50
20.10
21.67
19.59
20.84
27.64
17.05
30.65
33.04
32.32
29.50
25.31
COV
PERCENT*
1.03
0.46
1.27
0.63
0.87
2.31
0.94
-0.33
0.55
1.90
NUMBER OF
REPLICATIONS
2
5
5
3
3
3
3
1
1
1
1
1
1
MEAN FUEL
ECONOMY
16.93
20.86
22.46
20.26
21.61
28.21
COV
PERCENT*
0.501
1.76
2.00
1.08
i
1
27.14
27.20
29.18
17.91
31.90
36.04
32.65
30.09
26.12
1.79
1.86
0.43
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
92
-------
LOCATION.
VEHICLE:
"TIRE:
A/C:
METER:
LOCATION: Dyno #5
VEHICLE: 76 Pacer
TIRE: Bias 45 psi
A/C: Off
METER: 1514 + Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
NUMBER OF
REPLICATIONS
2
2
2
3
3
3
3
1
1
1
1
1
MEAN FUEL
ECONOMY
13.11
17.26
15.48
15.73
16.38
21.21
20.19
19.73
22.19
17.00
27.07
27.24
25.22
22.54
16.54
COV
PERCENT*
6.58
3.44
•4.20
0.38
1 . 83
0.61 i
1.62
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
93
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
LOCATION: Dyno #5
VEHICLE: 76 Pacer
TIRE: Bias 45 psi
A/C: On
METER: 1514
TEST TYPE
BAG1
BAG2
BAG3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
NUMBER OF
REPLICATIONS
2
2
2
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
11.93
15.24
13.86
14.03
14.54
18.94
14.90
23.87
24.62
24.22
21.51
16.23
COV
PERCENT*
5.75
1.30
0.15
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
94
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Pacer
Bias 45 psi
Simulated
Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
NUMBER OF
REPLICATIONS
1
1
1
2
1
1
1
1
1
1
MEAN FUEL
ECONOMY
13.61
17.55
15.20
15.92
16.45
20.88
17.90
27.45
28.56
25.43
22.01
16.65
COV
PERCENT*
0.14
!
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
95
-------
LOCATION;
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Aspen
Radial 45 psi
Off
Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Aspen
Bias 45 psi
Off
Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
3
3
4
1
3
4
3
1
1
1
1<
1
1
MEAN FUEL
ECONOMY
15.07
16.69
17.57
16.54
17.10
22.14
20.36
20.66
20.51
22.94
22.11
29.12
27.29
26.19
24.41
20.83
COV
PERCENT*
2.44
3.03
1,88
2.90
1.23
1.42
4.48
NUMBER OF
REPLICATIONS
2
3
3
2
1
2
2
3
1
1
1
1
1
1
MEAN FUEL
ECONOMY
14.59
16.64
17.33
16.33
16.96
21.61
20.31
20.88
20.46
22.94
18.54
30.44
27.92
26.81
24.71
21.20
COV
PERCENT*
8.82
5.19
3.04
i
0.69
2.18
1.83
0.64
i
i
1
!
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
96
-------
LOCATION.:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Aspen
Radial 45 psi
On
Unknown
LOCATION: Dyno #5
VEHICLE: 76 Aspen
TIRE: Bias 45 psi
A/C: On
METER:
Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
I ii 1
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
3
1
1
1
1
1
1
MEAN FUEL
ECONOMY
14.1
14.92
16.07
15.03
15.46
20.42
18.40
25.10
24.40
24.58
22.82
18.61
COV
PERCENT*
1.60
1.23
0.31
2.50
NUMBER OF
REPLICATIONS
1
1
1
1
2
MEAN FUEL
ECONOMY
13.50
16.26
17.24
15.82
16.71
19.40
COV
PERCENT*
4.01
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
97
-------
LOCATION;
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Aspen
Radial 26 psi
Off
Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
1
1
1
1
1
1
MEAN FUEL
ECONOMY
18.55
29.57
29.06
26.42
24.10
20.45
cov
PERCENT*
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
I
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
98
-------
LOCATION;
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Aspen
Radial 45 psi
Simulated
Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Aspen
Bias 45 psi
Simulated
Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
14.78
16.20
17.26
16.14
16.70
22.18
18.30
29.11
26.74
25.49
23.23
19.80
COV
PERCENT*
1.10
0.79
0.70
NUMBER OF
REPLICATIONS
4
MEAN FUEL
ECONOMY
20.32
COV
PERCENT*
9.22
i
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
99
-------
LOCATION;
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Impala
Radial 45 psi
Off
Unknown
LOCATION: Dyno #5
VEHICLE: 76 Impala
TIRE: Bias 45 psi
A/C: Off
METER: Unknown
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
— — — ^^^_— __^_
NUMBER OF
REPLICATIONS
2
4
4
3
1
3
3
3
MEAN FUEL
ECONOMY
10.62
11.55
13.38
11.77
12.41
18.45
17.22
17.87
18.23
19.07
COV
PERCENT*
1.93
0.34
0.47
0.46
2.22
3.33
1.50
NUMBER OF
REPLICATIONS
2
2
2
3
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
11.05
11.39
13.54
11.82
12.40
18.78
10.09
18.97
22.87
20.80
20.48
18.40
COV
PERCENT*
1.02
0.43
0.57
1.66
1
1
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
100
-------
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Impala
Radial 45 psi
Simulated
Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Dyno #5
76 Impala
Radial 45 psi
On
1514 + Unknown
TEST TYPE
BAG1
BAG2
BAG 3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
2
1
1
1
1
1
1
MEAN FUEL
ECONOMY
10.94
11.29
13.10
11.65
12.14
17.68
10.24
19.08
19.69
20.47
19.54
17.54
cov
PERCENT*
0.45
1.19
0.70
0.60
NUMBER OF
REPLICATIONS
2
2
2
2
i
t
1
1
1
1
MEAN FUEL
ECONOMY
9.64
10.4,1
12.29
10.67
11.29
16.61
17.61
18.59
17.98
16.15
COV
PERCENT*
6.16
0.68
0.46
0.21
t
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
101
-------
LOCATION. Track
VEHICLE: 76 Honda CVCC
TIRE: Radial (24/24 psi)
A/C: Off/Windows Up
METER: Unknown + 2099 Corrected
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Honda CVCC
Bias (24/24 psi)
Off/Windows Up
2099 Corrected
TEST TYPE
BAG1
BAG2
BAG 3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
3
6
5
8
1
2
2
1
2
2
2
2
2
2
MEAN FUEL
ECONOMY
24.96
25.41
28.81
26.14
27.01
35.92
32.56
34.65
34.48
38.10
50.01
50.29
45.55
40.17
34.21
28.05
cov
PERCENT*
1.75
1.76
0.78
2.77
1.08
0.86
0.65
2.97
2.00
0.65
0.76
1.16
NUMBER OF
REPLICATIONS
2
3
3
2
3
2
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
23.61
25.49
29.35
25.98
27.17
35.51
34.93
34.18
37.02
47.01
47.68
36.91
32.16
27.28
21.12
COV
PERCENT*
5.93
0.60
3.55
1.29
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
102
-------
LOCATION. Track
VEHICLE: 76 Honda CVCC
TIRE: Radial (24/24 psi)
A/C: Off/Windows Down
METER: Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
TEST TYPE
BAG1
BAG2
BAG3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
2
2
2
MEAN FUEL
ECONOMY
52.01
50.90
46.65
41.86
35.72
29.47
COV
PERCENT*
2.35
3.10
2.90
1.37
0.48
0.17
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
i
i
i
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
103
-------
LOCATION. Track
LOCATION: Track
VEHICLE: Datsun
TIRE: Radial (24/24 psi)
A/C: Off/Windows Up
METER: #1472
VEHICLE:
TIRE:
A/C:
METER:
Datsun
Bias (24/24 ps-j)
Off/Windows Up
#1472
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
4
9
5
6
4
3
3
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
23.78
24.60
27.54
25.14
25.98
36.76
35.40
34.38
38.48
18.48
28.94
39.50
45.58
40.18
34.81
29.69
24.96
cov
PERCENT*
3.46
1.48
1.21
1.41
1.98
1.36
2.68
1.11
0.54
0.52
0.34
0.67
0.02
0.29
4.08
NUMBER OF
REPLICATIONS
1
4
3
3
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
21.76
23.65
26.15
23.83
24.83
35.56
18.51
28.68
38.35
44.12
38.83
38.14
29. 3-6
24.31
COV
PERCENT*
4.82
2.88
3.04
i
1.64
1.65
1.00
1.70
1.51
0.06
0.02
0.26
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
104
-------
LOCATION. Track
LOCATION: Track
VEHICLE: 76 Chevette
TIRE: Radial (24/24 psi)
A/C: Off/Windows Up
METER: #1472
VEHICLE:
TIRE:
A/C:
METER:
76 Chevette
Bias (24/24 psi)
Off/Windows Up
#1472
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
7
7
7
1
2
2
2
2
2
2
1
2
2
MEAN FUEL
ECONOMY
17.68
22.09
23.51
21.32
22.76
26.69
21.47
25.07
25.66
28.05
35.88
34.33
32.16
28.85
23.59
20.09
cov
PERCENT*
0.32
4.20
6.71
0.64
1.86
0.03
0.30
2.35
5.48
0.88
5.10
2.92
NUMBER OF
REPLICATIONS
2
2
2
1
2
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
17.20
21.74
22.18
20.70
21.95
26.11
25.20
25.18
27.71
33.44
30.98
30.52
28.49
23.87
18.88
COV
PERCENT*
1.69
1.30
2.55
0.36
0.81
0.77
3.98
3.72
2.76
1.91
1.78 i
9.62
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
105
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Chevette
Radial (24/24 psi)
Off/Windows Down
#1472
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
TEST TYPE
BAG1
BAG2
BAG3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
1
1
2
2
MEAN FUEL
ECONOMY
27.20
35.05
30.63
30.46
28.55
24.29
20.05
cov
PERCENT*
1.14
5.61
2.26
1.51
0.21
NUMBER OF
REPLICATIONS
1
MEAN FUEL
ECONOMY
COV
PERCENT*
i
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
106
-------
LOCATION. Track
VEHICLE: 76 Chevette
TIRE: Radial (24/24 psi)
A/C: On/Windows Up
METER: #1472
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
TEST TYPE
BAG1
BAG2
BAG 3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
16.35
20.12
20.82
19.36
20.45
25.42
31.51
30.69
29.74
27.94
23.72
19.52
cov
PERCENT*
0.16
1.09
1.05
0.36
4.76
2.79
3.45
1.59
2.71
1.09
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
1
1
1
1
|
1
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
107
-------
LOCATION. Track
VEHICLE: 76 Pinto
TIRE: Radial (24/24 psi)
A/C: Off/Windows Up
METER: 1513 Corrected + Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Pinto
Bias (26/26 psi)
Off /Windows Up
1514 + Unknown
TEST TYPE
BAG1
BAG-2
BAG 3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
5
3
2
1
.
1
1
1
1
i
1
i
1
MEAN FUEL
ECONOMY
16.63
19.06
1-9.64
18.64
19.33
26.01
21.43
18.72
29.97
31.78
30.08
28.23
24.64
20.99
16.26
COV
PERCENT*
11.95
1.58
0.10
2.47
NUMBER OF
REPLICATIONS
1
3
2
1
2
2
3
3
2
MEAN FUEL
ECONOMY
16.11
18.75
19.49
18.31
19.09
25.03
21.92
24.55
24.41
27.53
COV
PERCENT*
3.10
6.31
3.08 1
4.46
2.23
2.22
2.13
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
108
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Pacer
Radial (24/24 psi)
Off/Windows Up
1514
LOCATION: Track
VEHICLE:
TIRE:
A/C:
METER:
76 Pacer
Bias (26/24 psi)
Off/Windows Up
1514
TEST TYPE
BAG1
BAG2
BAG 3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
2
1
1
1
1
1
MEAN FUEL
ECONOMY
17.04
14.78
15.98
18.99
16.62
17.62
17.12
18.14
COV
PERCENT*
3.82
1.20
NUMBER OF
REPLICATIONS
1
1
1
2
MEAN FUEL
ECONOMY
16.21
15.24
15.74
19.00
16.22
COV
PERCENT*
1.66
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
109
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Pacer
Radial (24/24 psl)
Off/Windows Up
1358
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
TEST TYPE
BAG1
BAG2
BAG 3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
4
2
1
1
2
2
1
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
12.69
15.10
15.00
14.50
15.05
17.88
16.70
17.67
17.47
20.04
33.16
29.87
25.43
21.66
16.29
14.11
12.45
cov
PERCENT*
0.28
3.72
2.26
1.40
0.36
4.50
3.53
4.73
3.46
6.64
0.25
0.17
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
110
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
LOCATION: Track
VEHICLE: 76 Pacer
TIRE: Bias (26/24 psi)
A/C: On/Windows Up
METER: 1513 Corrected + 1514
TEST TYPE
BAG1
BAG2.
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
NUMBER OF
REPLICATIONS
2
5
3
3
1
1
1
1
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
11.71
14.05
13.21
13.27
13.64
16.47
16.20
15.39
16.70
19.53
27.00
25.49
23.51
20.72
15.77
13.88
11.62
COV
PERCENT*
2.85
0.89
6.16
5.49
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
111
-------
LOCATION. Track
VEHICLE: 76 Pacer
TIRE: Radial (24/24 psi)
A/C: On/Windows Up
METER: 1358
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
1
3
2
1
2
2
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
12.15
14.60
13.60
13.75
14.14
16.39
16.51
16.66
18.46
28.10
27.27
24.20
20.48
15.63
14.09
11.80
COV
PERCENT*
2.18
4.78
0.21
0.04
0.50
1.38
0.16
0.26
0.66
0.32
0.35
2.70
NUMBER OF
REPLICATIONS
MEAN FUEL
ECONOMY
COV
PERCENT*
i
1
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
112
-------
LOCATION. Track
VEHICLE: 76 Aspen
TIRE: Radial (26/32 psi)
A/C: Off/Windows Up
METER: 1514
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Aspen
Bias (26/32 psi)
Off/Windows Up
1514
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
3
6
3
4
1
3
4
4
MEAN FUEL
ECONOMY
13.70
15.17
16.48
15.15
15.79
20.77
19.33
19.62
20.19
21.78
21.88
29.39
28.97
25.66
24.03
20.97
cov
PERCENT*
3.59
1.41
2.88
2.79
1.38
1.16
3.73
NUMBER OF
REPLICATIONS
1
5
4
3
2
2
2
2
2
2
MEAN FUEL
ECONOMY
12.38
14.71
15.47
14.33
15.06
19.90
COV
PERCENT*
0.98
2.80
2.71
I
I
22.48
27.24
26.97
24.39
22.10
19.89
!
1
1.48
2.05
0.60
0.20
i
1.31
1.03
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
113
-------
LOCATION. Track
VEHICLE: 76 Aspen
TIRE: Radial (26psi/32psi)
A/C: On/Windows Up
METER: 1514
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Aspen
Bias (26psi/32psi)
On/Windows Up
1514
TEST TYPE
BAG1
BAG 2
BAG3
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
4
2
3
2
2
2
2
2
2
MEAN FUEL
ECONOMY
12.69
13.69
15.84
13.97
14.70
19.56
21.22
25.28
25.79
24.15
22.20
19.93
COV
PERCENT*
0.72
6.32
0.312
4.25
NUMBER OF
REPLICATIONS
2
2
2
3
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
13.37
14.80
14.01
18.74
COV
PERCENT*
2.75
3.87
2.44
i
19.18
23.86
23.98
22.74
20.86
18.80
15.91
13.63
I
4.76
1.72
1.15
0.44
0.44
1.73
0.89
1.40
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
114
-------
LOCATION. Track
VEHICLE: 76 Ford Granada
TIRE: Radial (25/25 psi)
A/C: Off/Windows Up
METER: 1514 + Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Ford Granada
Bias (25/25 psi)
Off/Windows Up
1514
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
6
4
3
3
1
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
11.66
14.34
14.77
13.78
14.54
18.33
16.99
19.98
26.40
25.63
23.14
20.88
18.03
14.49
10.91
cov
PERCENT*
4.49
4.82
3.95
NUMBER OF
REPLICATIONS
2
7
5
3
2
1
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
14.58
14.79
14.08
14.68
17.81
15.89
18.11
25.49
25.39
22.78
20.95
17.73
14.11
11.00
COV
PERCENT*
1.93
1.69
0.59
5.43
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
115
-------
LOCATION. Track
VEHICLE: 76 Ford Granada
TIRE: Radial (25/25 psi)
A/C: On/Windows Up
METER: 1514 + Unknown
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Ford Granada
Bias (25/25 psi)
On/Windows Up
1514
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
5
3
3
1
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
10.14
12.14
12.39
11.72
12.26
16.49
18.99
21.75
22.21
20.48
18.59
16.12
12.68
10.78
cov
PERCENT*
0.56
1.94
2.33
NUMBER OF
REPLICATIONS
2
5
3
2
1
1
1
1
1
MEAN FUEL
ECONOMY
11.14
12.28
12.88
12.17
12.56
15.94
20.09
18.10
15.84
12.38
10.79
COV
PERCENT*
2.66
8.04
3.52
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
116
-------
LOCATION. Track
VEHICLE: 76 Impala
TIRE: Radial (26/28 psi)
A/C: Off/Windows Up
METER: 1472
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Impala
Bias (26/28 psi)
Off/Windows Up
1472
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
7
5
3
1
3
3
3
1
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
10.75
11.70
13.29
11.86
12.45
17.59
16.48
17.32
17.50
18.84
8.83
17.63
20.15
20.14
19.81
18.12
15.94
13.93
cov
PERCENT*
5.20
3.89
4.09
7.18
1.07
0.16
0.88
2.41
3.68
0.91
0.96
0.98
0.93
0.25
NUMBER OF
REPLICATIONS
3
6
3
3
3
1
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
9.65
10.76
12.35
10.88
11.50
17.16
11.81
17.65
19.22
19.45
19.29
17.69
15.48
13.30
COV
PERCENT*
1.71
1.09
1.68
2.19
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
117
-------
LOCATION.
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Impala
Radial (26/28ps1)
On/Windows Up
1472
LOCATION:
VEHICLE:
TIRE:
A/C:
METER:
Track
76 Impala
Bias (26/28psi)
On/Windows Up
1472
TEST TYPE
BAG1
BAG2
BAGS
FTP
(Derived)
HH
(Derived)
HST
CST
HNO
HRE
HSM
10 mph
20 mph
30 mph
40 mph
50 mph
60 mph
70 mph
80 mph
NUMBER OF
REPLICATIONS
2
4
2
2
2
2
2
2
2
2
2
2
MEAN FUEL
ECONOMY
10.18
10.54
12.27
10.87
11.35
16.86
9.85
14.62
17.48
18.13
18.53
16.47
14.99
13.19
cov
PERCENT*
3.06
2.16
3.63
0.34
0.72
6.92
0.53
1.68
0.50
3.13
2.08
0.96
NUMBER OF
REPLICATIONS
3
5
2
1
1
1
1
1
1
1
1
1
MEAN FUEL
ECONOMY
9.39
9.96
11.56
10.21
10.71
16.20
9.85
13.57
16.95
18.28
17.94
16.66
14.66
12.97
COV
PERCENT*
1.35
1.37
2.26
i
i
i
|
i
* Coefficient of variation of replicated measurements
(standard deviation divided by mean)
118
-------
APPENDIX D
WEIGHTED LEAST SQUARES LINEAR REGRESSION
OF VOLUMETRIC AND CARBON BALANCE DIFFERENCES
Let x.j , y.j be volumetric and carbon balance measures, respectively
for the ith group of replicated runs, and let n-j be the number of
replications. Two different types of measures may be considered, namely,
mean fuel consumption (in gpm) or mean fuel economy (in mpg) of the
replicated runs, but the regression technique is the same in either case.
Define A^ = y^ - x^ , the difference between volumetric and carbon
balance measures, and assume a linear model for the dependence of A on
x. That is,
A. = a + bx. + e.
i i i
where a and b are unknown constants to be estimated and e^ is an
error of zero mean and variance given by
„
ni
It is assumed here that the variabilities of a single carbon balance
measurement and of a single volumetric measurement are expressed by
constant coefficients of variation, (COV)C and (COV)M, respectively,
and that (COV)02= (COV)C2 + (COV)M2 is the (squared) coefficient of
variation of an unreplicated difference A relative to the mean of
either measure.
From this, it follows that as shown above, the variance of e-j
(the error in Aj ) is (COV)g2 multiplied by the squared mean
(approximately x^) to convert to variance, and then divided by rii
to reflect the variance reduction derived from replication.
Because the ae-j2 are not uniform over the data set, those points
with smaller variance should receive relatively higher weight in estima-
tion of a regression line. The appropriate weighting is proportional to
the inverse of the variance. Thus, define normalized weights as follows:
119
-------
u. . V*,' . ",
i z n./x,2 " x.2U
J J I
The estimation of a and b by least (sum of weighted) squares regression
is based on the following statistics:
A *= Z u.A.
l i
l
A2 = Z u.A.2
l l
X = Z U.X.
X2 = Z U.X.2
A • x = Z u.A.x.
i
Weighted least squares estimates for a and b may then be expressed as
x - A x
x2 - (x):
a = A - b x
In order to assess the significance of the coefficient values so
derived, their variance also needs to be estimated. To do this we need
an estimate for (COV)Q, which is given by
= [A2 - (A)2 - (b)2 (x2 - (x)2)] U
where N is the number of data points (i.e., replication groups). The
S\ "^
variance of a and b are then
a.2 - (COVV
a u
(COV) 2
b U (x2 - (x)2)
J2Q
-------
APPENDIX E
TWO-WAY ANALYSIS OF VARIANCE WITH UNEQUAL VARIANCE ESTIMATES
Let us suppose we have sample means y-y and estimated variances
s.j .2 of a response variable for various combinations of blocks
(i = 1, 2, ..., I) and treatments (j = 1, 2, ..., J). We desire to
know if there are significant effects due to blocks and/or treatments.
This situation is different from a conventional Analysis of Variance
(ANOVA) situation in that we do not have available individual responses
within each (i,j) cell, but rather a cell mean and an associated variance.
However, there is a very strong similarity with the 2-way ANOVA model with
unequal numbers* and the formulas derived will be seen to be analogs of
that model.
For applications made in this report, the y^ are mean fuel economy
ratios, the sij2 are squared standard error estimates, and the blocks
and treatment groups may cover such factors as different test cars, air
conditioning status, and different test driving sequences.
Responses are generally available for only a subset of all (i,j).
However, there must be at least one response for each block and for each
treatment and, if N is the total number of cells for which responses
are available,
N >_ I + J - 1.
The model assumed is a two-way effects model with no interaction:
y"T7 = u + b. + t. + e..
•Mj M i J iJ
where e^ . are independent normal errors with zero mean and variance,
s.j-2. Th^ quantity y is the (weighted) grand mean over all available
responses and the b-j (and t,-j are systematic effects due to particular
blocks (and particular treatments). We desire to test certain hypothesis,
notably
and
H : b. = b, i.e., there are no differential effects among blocks
b i
H : t. = t, i.e., there are no differential effects among treatments
t J
* See, for example, 0. Kempthorne, The Design and Analysis of Experiments,
John Wiley, New York, 1952, p. 79.
121
-------
Define weighting coefficients
„ - N / Z 1
1' • • 9/11 o
1J Sij / kJ Skl
utilizing the convention that 1/s-jj = 0 for all non-response (i,,ij) cells,
Note, therefore that
n. =0 for all non-response (ij)
and
Zn. . = N
Define
N, = Z n. . N = Z n..
V< U 'Vj i IJ
Y. = Z n.. y.. V = Z n. . y.
1.- . U U Y.j . U ^i
J I
= I n.. y. .
Impose the two conditions
Z N. b. = Z N . t. = 0
i* i -J J
on the model because of linear dependences of the coefficients. This says
that the weighted average block effect over all blocks is constrained to
zero and the weighted average treatment effect over all treatments is
constrainted to zero, therby defining an unambiguous grand mean effect y.
Weighted least squares estimates of the coefficients, y, b., t.,
are next obtained. The grand mean estimate is computed first
122
-------
Define the column vectors
X = (b1,b2,...,bI_1,t1,t2>...,tJ_1)
C= (Y1.-N1.y,...5YI_lj.-NI_1.u5Y.1-
and the I+J-2 order square matrix
N. 0
1-
1-1-
V. .
1J
A. .
1J
'N.
N . 0
•1 •.
J-1*
/
i = 1, ..., 1-1
j = I, ..., I+J-1
i = I, ..., I+J-1
j = 1, ..., 1-1
Solve the matrix equation y\.X = C for X, i.e.,
X =yV C
/V /% /
This provides all the b. except bj and all the tj except tj.
Solve for bj and tj from the previously imposed constraints.
The reduction in Sum of Squares (S.S,) due to fitting y, b-j is
R(y,b) =
; I degrees of freedom (d.f.)
123
-------
Similarly, the reduction in S.S. due to fitting y,t, is
J J
-
R(y,t) = y - r - ; J degrees of freedom (d.f.)
T-:-
J=l
Finally, the reduction in S.S. due to fitting all parameters, y.b^tj is
R(y,b,t) = y Y + £ b. Y. + Z t. Y . ; (I+J-1) d.f.
j i i* • J *J
For testing hypothesis H. : b. ~ b
R(y,b,t) - R(y,t)
Mean square due to fitting bn- : s = - —•> -
Mean square error: E = — - ; d.f. > > 1*
Under H. , S/E has approximately F-distribution with (1-1,°°) degrees
of freedom. Therefore, for tests at a level of significance a, reject
H. if S/E > f. .
b I-l,°°,a
For testing hypothesis H : t. = t
_^___ J
R(y,b,t) - R(y,b)
Mean square due to fitting t. : T = —
j o-J.
Mean square error: E = —. ; d.f. > > 1*
77 E 1 / S..2
N .. ij
Under H., T/E has approximately F-distribution with (J-l,°°) degrees
of freedom. Therefore, for tests at a level of significance a, reject
Ht if T/E > f, .
L -
* Note, in contradistinction to conventional ANOVA, the mean square error
is estimated (externally) from the S-jj2, rather than from the variations
of y-jj among the block/treatment cells, because of the considerably
greater degrees of freedom in the external estimate.
124
-------
APPENDIX F
CALCULATION OF HORSEPOWER FROM COAST-DOWN TIMES
If the time, At, it takes a vehicle of mass, M, to decelerate from
55 mph to 45 mph is measured in seconds, then the force acting on the
vehicle at 50 mph is estimated to be
F is in units of pounds if M is in units of slugs, Av in units of feet
per second and At in units of seconds. The power dissipated by the vehicle
at speed VT is
P = FVT
where P is in units of ft-lbs/min if Vy is in units of ft/min.
V = 50 mph = 4400 ft/min
Av = 10 mph = 14.667 ft/sec
Thus,
M '14'667
n /je 1L, . . 32.16 Ib/sli
P (ft-lb/nrrn) =— —
and
n i*>. TI_/ • \ Mass of vehicle in Ib /onn,- -7 r* / • \
P (ft-lb/min) = 7 -—. — : — (2006.7 ft sec/min
v ' ' Coast-down time in seconds v
n /i, \ Mass of vehicle in Ib /n neno1»
P (Horsepower) = -—, r-: : r—J 0.06081)
v Coast-down time in seconds)
since
1 ft-lb _ 1 horsepower
min ~ 33,000
125
------- |