United States Motor Vehicle Emission Lab EPA
Environmental Pint.-.-ti.MI 2585 Plymouth Rd JuK 19
Agency Ann ArK" Mirhui.in 48105
Assessment Of An
Empirical Technique
For Estimating
Vehicle Aerodynamic
Drag From Vehicle
Shape Parameters
-------
ASSESSMENT OF AN
EMPIRICAL TECHNIQUE
FOR ESTIMATING
VEHICLE AERODYNAMIC DRAG
FROM VEHICLE SHAPE PARAMETERS
by
W.M. Smalley and W.B. Lee
The Aerospace Corporation
El Segundo, California 90245
Contract No. 68-03-2482
EPA Project Officer: Glenn D. Thompson
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
Ann Arbor, Michigan 48105
July 1978
-------
This report is issued by the Environmental Protection Agency to report technical data of
interest to a limited number of readers. Copies are available free of charfe to Federal
employees, current contractors and grantees, and nonprofit organization* - as supplies
permit - from U.S. EPA, 2565 Plymouth Rd., 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 The Aerospace
Corporation, El Segundo, California 90245, in fulfillment of Contract No. 68-03*2482.
The contents of this report are reproduced herein as received from The Aerospace
Corporation. 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 Environmental
Protection Agency.
Publication No. EPA-460/3-78-010
-------
FOREWORD
This report, prepared by The Aerospace Corporation for the U.S.
Environmental Protection Agency, Emission Control Technology Division,
presents the results of a determination of aerodynamic drag coefficient, C_,
based on an empirical prediction technique developed by The Aerospace
Corporation in a previous EPA-sponsored study. Values of C~ so deter-
mined are compared with C~ values derived from wind tunnel test data.
iii
-------
ACKNOWLEDGMENTS
During the course of this study, Mr. Glenn Thompson of the
Environmental Protection Agency's Emission Control Technology Division,
who served as EPA Project Officer for the study, provided valuable guidance
and assistance. His efforts are gratefully acknowledged.
The following technical personnel of The Aerospace Corporation
made valuable contributions to the study.
William M. Smalley
Warner B. Lee
Bernard Pershing
Mamoru Masaki
L. Forrest, Systems Director
Vehicle Performance Directorate
Approved by
M. G. Hinton, Principal Director
Mobile Systems Directorate
Eastern Technical Division
Eastern Technical Division
anager
-------
CONTENTS
FOREWORD iii
ACKNOWLEDGMENTS v
SUMMARY S-1
1. INTRODUCTION AND BACKGROUND 1-1
2. ANALYTICAL APPROACH. 2-1
3. DATA BASE 3-1
3.1 Data Acquisition 3-1
3.2 Data Reduction 3-6
4. RESULTS 4-1
4.1 Calculated CD Value 4-1
4.2 Comparison with Wind Tunnel Results 4-3
5. CONCLUSIONS AND RECOMMENDATIONS 5-1
REFERENCES R-l
APPENDICES
A. DRAG PREDICTION METHOD A-l
B. SAMPLE CALCULATION B-l
C. VEHICLE DIMENSIONS AND AREAS C-l
vii
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TABLES
2-1. Vehicle Characteristics 2-2
3-2. Reference Panel Assignment 3-9
4-1. Summary of Results 4-2
4-2. Comparison of Calculated Aerodynamic Characteristics
with Wind Tunnel Results 4-5
FIGURES
3-1. 1977 Chevrolet Impala, Front View 3-3
3-2. 1977 Chevrolet Impala, Rear View 3-4
3-3. 1977 Chevrolet Impala, Side View 3-5
3-4. 1977 Chevrolet Impala, Front End Detail 3-7
3-5. 1977 Chevrolet Impala, Rear Detail 3-8
4-1. Comparison of Test and Calculated Values of
Aerodynamic Drag Coefficient 4-6
4-2. Porsche 924, Front End Detail 4-3
A-l. Vehicle Dimensions A-2
A-2. Hatchback-Notchback Drag Coefficient Ratio A-6
viii
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SUMMARY
Aerodynamic drag coefficients for a fleet of twenty 1977/1978
model year passenger cars were derived using an empirical drag predic-
tion technique previously developed for EPA by The Aerospace Corporation.
This method utilizes an aircraft type "drag build-up" approach wherein the
total drag is calculated as the sum of C_ contributions from various com-
ponents of the vehicle.
The development of the aerodynamic drag coefficient using this
method requires that an extensive data base of vehicle dimensions be
determined. This was done by direct measurements in the field and from
8 x 10 photographs of the vehicles. To minimize distortion, photographs
were taken from a distance of 100 meters using a telephoto lens in combina-
tion with a 35mm single lens reflex camera. The required projected areas
were determined by planimetry from the photographs.
Results of the study indicate that the largest single contributor to
the overall drag coefficient is the front end drag coefficient, CD , which
constitutes, on the average, about 29% of the total average drag coefficient.
The other major contributors were found to be the base region drag co-
efficient, CD (20%) and the front wheel and wheel well drag coefficient,
CD (26%). 5
Twelve of the twenty vehicles evaluated in this study were also
tested by the Lockheed-Georgia Company in their Low Speed Wind Tunnel
(LSWT). The LSWT test results were reported for two methods of wind
tunnel blockage corrections: the area ratio method and the ceiling static
pressure signature method. The latter blockage correction method re-
sulted in 8% lower values of C_ than those based on the area ratio method.
A comparison of the LSWT test results based on the area ratio
blockage correction method with the values derived in this study showed
that nine of the twelve vehicles were within + 10% of the wind tunnel test
S-l
-------
results. The remaining three vehicles were found to be 12 to 18% lower
than the wind tunnel results.
Wind tunnel test results based on the ceiling static pressure block-
age correction method could be compared to five of the vehicles evaluated
in this study. Calculated C's for four of these vehicles were within +10%
of the wind tunnel test results, while the CD for the fifth vehicle was 16. 5%
higher than the wind tunnel test result.
The reasons for the differences with the wind tunnel results are not
known precisely, although several potential sources of error have been iden-
tified which could have contributed to this lack of agreement. One is the
of precision involved in the use of edge radius as a sole descriptor of
contour in certain critical drag regions such as the vehicle front end. A
second factor is the high degree of sensitivity of the results to the ratio of
the edge radius and the projected length of that radius. Modifications to the
calculation technique in these and other areas could improve the accuracy of
the method.
A summary of the drag prediction method used in this study is givet\
in Appendix A. Sample calculations and individual vehicle dimensions and
areas are provided in Appendix B and C, respectively.
S-2
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SECTION 1
INTRODUCTION AND BACKGROUND
The current federal test procedure for certification testing of light
duty vehicles consists of running the vehicle on a dynamometer through a
prescribed duty cycle. The power absorption unit of the dynamometer is
adjusted according to a table of 50-mph road-load horsepower settings which
are defined for a discrete set of loaded vehicle weights. Beginning with the
1979 model year, the method of determining the nominal dynamometer road
load setting will be based primarily upon the vehicle reference frontal area
(rather than vehicle inertia weight) and adjustments will be made according
to whether the vehicle is classed as a fastback or non-fastback model (Ref. 1).
Implicit in these procedures is the assumption that aerodynamic drag effects
correlate simply with weight or frontal area and body type. Since, in general,
the aerodynamic drag is variable with specific vehicle shape and contours as
well as size, the ability to estimate the drag of individual vehicle configura-
tions could provide an analytical basis for improving the accuracy of fuel
consumption and exhaust emissions testing.
In a previous study for EPA (Ref. 2), the Aerospace Corporation
developed an empirical technique which estimates the aerodynamic drag of
road vehicles from various vehicle configuration parameters. The present
study is directed toward the acquisition and application of vehicle measure-
ments data as required to evaluate aerodynamic road load by this prediction
method for comparison with measured values. The intent of this work is to
test the relative accuracy of this prediction system as compared with the
1979 federal test procedure for determining dynamometer road load power
absorption settings.
1-1
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SECTION 2
ANALYTICAL APPROACH
The technique used to develop the aerodynamic drag coefficient is
based on the method developed in The Aerospace Corporation report,
"Estimation of Vehicle Aerodynamic Drag," Reference 2. This method con-
sists of an aircraft-type "drag build-up" wherein the total drag is considered
to be equal to the sum of the contributions of the various components of the
vehicle. The individual equations for each C-. component, together with a
definition of terms, are given in Appendix A for convenient reference. The
development of the aerodynamic drag coefficient by this method requires
that numerous vehicle physical dimensions be determined, including several
projected areas, edge radii and associated lengths, and the slope of the
windshield and hatch portions of the vehicle. The methods used to obtain the
required dimensions and areas are discussed in Section 3.
A total of twenty 1977/1978 model year vehicles were investigated
in the course of this study. Vehicles selected were based on a list of pri-
mary vehicle choices provided by the EPA. Characteristics of the individ-
ual vehicles are summarized in Table 2-1, including specific protuberances
such as antenna, rear-view mirrors, etc., on each vehicle.
2-1
-------
Table 2-1. Vehicle Characteristics
Manufacturer
Chrysler
Ford
General Motors
Porsche
Volkswagen
Model
Year
1977
1977
1978
1978
1977
1977
1977
1977
1978
1978
1978
1977
1977
1977
1978
1978
1978
1978
1978
1977
Make
Plymouth
Plymouth
Chrysler
Plymouth
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Chevrolet
Chevrolet
Oldsmobile
Chevrolet
Chevrolet
Chevrolet
Oldsmobile
Porsche
Volkswagen
Model
Arrow
Volare
LeBaron
Volare
Granada
LTD II
Mustang II
Pinto
Fairmont
Granada
LTD II
Impala
Nova
Cutlass
Supreme
Impala
Monza
Nova
Cutlass
Supreme
924
Rabbit
Body Style
2-d». Coupe
Station Wagon
4-dr. Sedan
Station Wagon
4-dr. Sedan
4-dr. Sedan
2-dr. Notch-
back
3 -dr. Runaboi*
4-dr. Sedan
4-dr. Sedan
4-dr. Sedan
4-dr. Sedan
4-dr. Sedan
2-dr. Coupe
4-dr. Sedan
2-dr. Fastback
4-dr. Sedan
2-dr. Coupe
2-dr. Coupe
2 -dr. Hatch-
back
Wheelbase
92.1
112.7
112.7
112.7
109.4
118.0
96.2
94.5
105.0
109.9
114.0
116.0
111.0
112.0
116.0
97.0
111.0
108.1
94.5
94.5
Protuberances
(1). (2)
(1). (3), (4). (6)
(D.(3),(6)
(1). (3). (4)
(1), <5), (6)
(1). (5). (6)
UU5)
(1). (5)
(1), (5). (6)
(1), (2), (6)
<1).<2),<6)
(5)
(5)
(5). (6)
(5)
(2)
(5)
(3). (6)
(1). (5)
(D,(3)
(1) External antenna
(2) Two bullet mirrors
(3) Two conventional mirrors
(4) Luggage rack
(5) One conventional mirror
(6J Hood ornament
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SECTION 3
DATA BASE
As indicated in Appendix A, the development of the aerodynamic
drag coefficient C_. using the drag build-up method requires that an exten-
sive data base of vehicle dimensions be developed. This was done by direct
measurement in the field and from 8 x 10 photographs of the vehicles.
3.1 DATA ACQUISITION
The numerous edge radii required to develop the various compon-
ents of C_ as defined in Appendix A were obtained by direct measurements
of the vehicles. For edge radii <0.75 inch, a series of fixed templates were
used to match the vehicle contours. For edge radii > 0. 75 inch, a flexible
curve was fitted to the vehicle contour, transferred onto paper and matched
to a known radius. The corresponding edge lengths were primarily deter-
mined by measurements from the photographs, as discussed in Section 3.2.
If a true projected length (e.g., vertical length) could be measured in the
field, it was recorded and served as confirmation of the value determined
from the photograph.
The angle of inclination of the windshield and hatch portion, which
are required in the evaluation of C— and C_. , respectively, were measured
2 5
with an inclinometer reading to the nearest 0. 5 degree. The local horizontal
at the vehicle was also determined in order to obtain the true angle of the
windshield and hatch portion.
Direct field measurements were also made of antenna, hood orna-
ments, and radiator dimensions in order to determine their projected areas,
since these could not be measured from the photographs.
The remaining required areas, as shown in Figure A-l, Appendix A,
include the projected frontal area (AR), the projected area of the front end
(A—), the projected area of the windshield (A^), the projected area of the
3-1
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body below the hood -wind shield intersection (A, ), the projected area of the
flat portion of the base region (A,J, the projected area of the upper rear or
hatch portion of the base region (Ar), and the projected area of various pro-
tuberances such as mirrors and luggage racks (A }.
i
In addition to these projected areas, certain vehicle dimensions
also had to be determined from the photographs. These included the proj-
ected length of the hood (L^), the projected length (L.) and width (W) of the
vehicle underbody and the vehicle height (H).
In order to obtain the above required information, front, side, and
rear views were taken of each vehicle from a distance of 100 meters. This
camera-to-subject distance was selected on the basis of the recommendations
presented in Reference 2, which indicates that a camera-to-subject distance
of at least 100 meters should be used to minimize errors due to perspective.
Two reference panels having known dimensions and areas were
included in each view, as indicated in Figures 3-1 to 3-3. For the front and
rear views (Figures 3-1 and 3-2), panel number I, to the right of the vehicle,
was located at a distance of 100 meters, in line with the front of the vehicle.
Panel number II, on the left, was located at the mid-point of the wheelbase.
In the side view (Figure 3-3), the near face of the vehicle was at 100 meters,
with both panels located at the vehicle longitudinal center line.
Because of the necessity of taking both front/rear and side views of
the vehicle and the approximate 2 to 1 vehicle dimensional disparity in these
views, lenses of two different focal lengths were used in conjunction with an
Olympus OM-1 35mm single lens reflex camera. For the side view, a
400mm focal length, f5.6 lens was used. For the front and rear views, the
400mm lens was used in combination with a 2X converter, which gave an
effective focal length of 800mm. The objective in selecting these focal
lengths was to obtain sufficient image size to minimize the degree of enlarge-
ment required in the 8x10 photographs. To minimize camera motion, the
lens/camera was mounted on a tripod. In addition, the camera mirror was
locked up prior to .photographing the vehicle, and the shutter was tripped by
the built-in shutter release.
3-2
-------
UJ
I
OJ
Figure 3-1. 1977 Chevrolet Impala, Front View
-------
Figure 3-2. 1977 Chevrolet Impala, Rear View
-------
i
Ul
Figure 3-3. 1977 Chevrolet Impala, Side View
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In order to adequately outline the underbody profile, a white panel
was placed behind each vehicle in all three views.
Test photographs indicated that thermal effects could create an
extreme image distortion effect, particularly on an asphalt surface. Accord-
ingly, a concrete surface was selected in order to minimize this effect.
In addition to those photographs taken at a distance of 100mt
three-quarter front and rear views were also taken of each vehicle using a
standard 50mm lens from a distance of 5 to 10 feet in order to provide
additional detail of front and rear body configurations and contours. Exam-
ples of these are shown in Figures 3-4 and 3-5.
3.2 DATA REDUCTION
Area measurements were made by planimetry, using a K & E
Model 4242 Compensating Polar Planimeter. The planimeter was calibrated
in terms of photo area (at a specific tracer arm setting) by use of the
2
standard 10. 00 in Test Rule provided with the instrument. The calibration
of actual (vehicle) area to photo area was obtained by determining the photo
area of the 6. 00 ft reference panels (formed by a 54 in x 16 in rectangle).
The latter area was found by measuring the height and width on the photo of
the reference rectangle, and taking the product of photo height and photo
width. This procedure was adopted because it was more rapid than plani-
metering the reference panels in the photo. Check measurements verified
that both procedures gave the same results for the photo area of the refer-
ence panels.
For the front and rear views, reference panel I was located at the
100 meter line (adjacent to the front or rear bumper, respectively) while
panel II was located on the other side of the car, at the midpoint of the wheel
base. The reference panel(s) used in conjunction with each planimetered
area are indicated in Table 3-2.
The notation (I + II)/2 means that the area calibration was taken to
be the arithmetic average of the calibration factors determined for each
3-6
-------
OJ
Figure 3-4. 1977 Chevrolet Impala, Front End Detail
-------
00
Figure 3-5. 1977 Chevrolet Impala, Rear Detail
-------
Table 3-2. Reference Panel Assignment
Area
Symbol
Area Calibration
Based on Panel(s)
FRONT VIEW
Reference
Hood and Front
Front
Windshield
Protuberance (Mirror
or Luggage Rack)
Base
Hatch
Non-Station Wagons
Station Wagons
AR
I + II
I
II
U
REAR VIEW
B
panel. It is seen that the calibration factor for each planimetered area was
based on the panel nearest to the segment of the vehicle defining that area.
For an area defined by vehicle segments lying between the two panels, or
comprised of sectors near each panel, the average calibration factor of the
two panels was utilized. The rationale for this approach is illustrated by
the case for vehicle frontal area A..., as follows.
t\.
The selection of the average of Panels I and IT for use as the cali-
bration factor in determining the vehicle reference frontal area, A._, was
£x
based on an assessment of the elements of the vehicle outline in the front
view. For that portion of the vehicle below the front wheel well, the con-
trolling perimeter is composed of the front wheel well, bumper, and front
3-9
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under carriage, all well forward of the Panel II location at the mid-point of
the wheelbase and behind Panel I. Above the front wheel well, the controlling
perimeter moves aft to the base of the windshield, then along the A-post and
finally across the top of the vehicle (at or near the Panel n location). Thus,
the controlling outline appears to range between Panel I and Panel II. If
Panel n alone had been used in evaluating A_, the calculated frontal area
tv.
would have been, on the average, about 2% larger. An increase of 2% in A,.,
.R
would have reduced C_. by about 1. 5% and the product C_.A which is used in
determining the aerodynamic drag force, would have been reduced by about
0.5%.
Reproducibility and precision of the planimetry was established by
performing replicates of the planimetry operation for two cars, including
the effect of varying the pole position for each measurement. Based on
the results, the photo areas of the remaining vehicles were planimetered
twice with additional measurements taken if the two readings differed by
more than 1% and by more than 0.02 planimeter unit (the precision of reading
was +0.01 planimeter unit).
Lengths were measured by engineering scale (60 divisions per inch)
with the aid of an optical magnifier. The photo lengths were calibrated in
terms of actual length by the previously measured photo length of one side of
the reference rectangle. The reference panel (1 or II) which was located
closest to the dimension being measured was used. For the side view photos,
an'additional (and longer) reference length was provided by the field measure-
ment of the spacing between the reference panels, both of which were the
same distance from the camera. All photo measurements were made from
8 x 10 enlargements.
The basic definitions of the various length and area terms are de-
fined in Appendix A. The specific definitions varied for each car, however,
and were keyed to the actual vehicle geometry. For example, in order to
establish the front end projected area Ap, it was necessary to define three
3-10
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aerodynamic "breaklines," i.e., front-hood, front-underbody and front-side.
In some cases the definition of the breakline was evident; in other cases,
however, complex trim, and sheet metal contours made this decision more
subjective. In these cases, a value judgment was made, based on field notes
and measurements and the photographs (both long range and closeup detail
shots). In any event, the objective of the procedure was to ensure that a com-
mon set of breaklines was used to define the various areas, lengths and radii
of curvature for a given vehicle.
For the purpose of planning future work, it may be noted that the
determination of the aerodynamic drag coefficient, C-., using the drag build
up technique employed in this study typically required about 8 hours per
vehicle. Field data collection, including vehicle measurements and position-
ing the vehicle and reference panels for photographic purposes, required
about 3 hours. Data reduction, including area determinations by planimetry
and linear measurements from the photographs, and the determination of
field measurements of the various radii of curvature required 3 to 4 hours,
while the computations, including the length weighted R/E ratios and the
C-p. calculations^ required an additional 1 to 2 hours.
3-11
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SECTION 4
RESULTS
4. 1 CALCULATED CD VALUES
The individual components (CD ) of the total drag coefficient, C_,
were evaluated as outlined by the "drag "build-up" method (Ref. 2) given in
Appendix A. A sample calculation of these individual drag components for
the 1977 Chevrolet Impala is shown in Appendix B.
The projected frontal area, A_, the individual drag components,
CD - C_ , and the total drag coefficient, CQ for each of the test vehicles
are summarized in Table 4-1.
Examination of these C_ components indicates that the largest
single contributor to C_ is the frtint end drag coefficient, C_ , with an aver-
age value of about 0. 154, or about 29% of the total average C—. The contribu-
tion of the base region, CD is about 0.105, or about 20% of the total. The
third major contributor is tne front wheel and wheel well drag coefficient Cn ,
7
taken to be a constant value of 0.140 (26% of the total Cn). These three com-
ponents; Cn , Cn , and Cn ; thus constitute, on the average, about 75% of
1 5 7
the total CD.
It will also be noted that the front end drag coefficient, C-. , en-
compasses the greatest vehicle-to-vehicle variation, ranging from 6.075
for the Porsche 924 to 0.228 for the 1978 Ford LTD II. In evaluating C_ ,
1
it was found that the results were extremely sensitive to the edge radii
and associated edge lengths. Examination of Equation 1, Appendix A shows
that of the three edge radii/length ratios, (R/E), the greatest weight is
placed on (R/E) , relating to the vertical edge geometry. Because the vertical
edge length, E , is considerably shorter than upper or lower edge lengths,
the (R/E) ratio is typically larger than the other two; i.e., (R/E) and (R/E),.
Hence, this ratio is generally dominant in the evaluation of CD. And, since
the vertical edge length was found to be quite similar on many of the domestic
4-1
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Table 4-1. Summary of Results
Manufacturer
Chrysler
ford
General Mofura
Porochc
Volkdwagon
M. v.
1977
1977
1978
1978
1977
1977'
1977
1977
1976
1978
1978
1977
1977
1977
1978
I97B
197 S
1978
1978
(977
Make
Plymouth
Plymouth
Chrydar
Plymouth
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Chevrolet
Chevrolet
Oldamubile
Chevrolet
Chevrolet
Chevrolet
Oldamobilo
Poracho
Volkuwagen
Model
Arrow
Volaro
LeBaron
Volaro
Granada
LTD II
Mualang II
Pinto
Fairmont
Granada
LTD 11
Impala
Nova
Cutlasa
Itnpala
Monca
Nova
CulUui
924
Rabbit
Body Style
2-dr. Coupe
Station Wagon
4-dr. Sedan
Station Wagon
4-dr. Sedan
4-dr. Sedan
2-dr. Nolchback
3 -dr. R unabout
4-dr, Sedan
.4-dr. Sedan
4-dr. Sedan
•4-dr. Sedan
4-dr. Sedan
2-dr. Coupe
4-dr. Sedan
2-dr. Fallback
4-dr. Sedan
2-dr. Coupe
2-dr. Sport q>e
2-dr. Hatchback
Frontal
Area,
HZ
17.82
22.76
23. OS
22.79
22.22
23.22
19.29
19.46
21. OS
22. 18
23.21
24. 14
22. 56
22.42
23.89
19.04
22.77
21.58
IS. 88
19.77
C°,
Front
End)
0. I8S
0. 133
0. 182
0. 146
0. 200
0. 223
0. 145
0. 100
0. 113
0.214
0.228
0. 179
0. 106
0. 157
0. 170
0. 165
0.093
0. 149
0.075
0. Ill
C"2
(Wtnd-
•hleldl
0.017
0.046
O. 044
0.051
0.024
0.023
0.019
0.031
0.030
0.028
0. 021
0.029
0.026
0.032
0.031
0.017
0.024
0.019
0. 018
0.035
C°»
(Front
Hood)
0.014
O.OI3
0.009
0.013
0.006
0. OOfc
0. Oil
0.022
0.009
0.007
0. 005
0.010
0.012
0.016
0.009
0.027
0. 0)2
0.019
0.055
0.037
X
(Rear
Verticil
Edge)
-0. 002
-0.001
-0. 002
-0.001
-0. 003
-0. 002
.0. 002
-0. 002
-0. 002
-0. 002
-0.001
-0.001
-O. 002
-0. 001
-0. 001
-0.004
-0. 002
-0. 001
-O. 008
-0. 002
C°5
(Baie
Region
0.097
a 111
O. Ill
0. 108
0. 107
0.099
0. 1)4
0. 124
0. 110
0. 114
0.098
0. 106
0. 105
0. 103
0. 108
0.084
0. (05
0. 116
0.073
0. 102
X
(Under
body)
0.037
0.044
0.044
0.044
O.O44
0.045
0.043
0.040
0.042
0.043
0.046
0.045
0.043
0.041
0.046
0.041
0.041
fl. 042
0.039
0.031
X
(Front
Wheel
Well)
0. 140
0. 140
0. 140
0. 140
0. 140
0. 140
0. 140
0. 140
0. 140
0.140
0. 140
0. 140
0. 140
0. 140
0. 140
O. 140
0. 140
0. 140
0. 140
0. 140
X
(Rear
Wheel
Well)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0. O
0.0
0.0
0. O
0.0
0.0
0,0
0.0
0. 0
0.0
0.0
0.0
0.0
CD,
(Protub-
erances)
0. 004
0.022
0.014
0.023
0.008
0.008
0.007
0,007
0.009
0.003
0. 002
0.007
0.006
0.009
0.006
0.0
0.007
0. 013
0.011
0. 009
CD,0
Bullet
Mirror)
0.007
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.004
0.004
0.0
0.0
0.0
0.0
0.005
0.0
0.0
0.0
0.0
CD,I
[Radia-
tor)
0.029
0. O46
0.043
0.041
0. O49
0.054
0.036
O.O14
0.052
0.041
0. O50
0.047
0.042
0.044
0.048
0.036
0.042
0.048
0.027
0.026
CD
(£cDi(
0.528
0.554
0.585
0.565
0,575
0,596
0.513
0.496
0.501
0.592
0.593
0.562
0.478
0.543
0.557
0.511
0.462
O. 547
0.430
0.489
-------
cars, the value of this ratio was largely dependent on the value of the vertical
edge radius in the fender/headlight region. It is believed that this particular
edge radius was largely responsible for the variation seen in C— .
Ul
4.2 COMPARISON WITH WIND TUNNEL RESULTS
Twelve of the twenty vehicles evaluated in this study were also tested
by the Lockheed-Georgia Company, Marietta, Georgia in the Low Speed Wind
Tunnel (LSWT), as reported In References 3 and 4. Wind tunnel test results
were given in Reference 3 for eight of the 12 vehicles and were based on the
area ratio method of determining the wind tunnel blockage correction. In this
method, the test section blockage is computed as a function of the ratio of
automobile frontal area to test section cross section area; i.e., K = 1/2 (S/C),
where S is the automobile frontal area and C is the test section cross sectional
area.
Lockheed subsequently reported (Ref. 4) that studies of wind tunnel
blockage methods showed that the conventional area ratio method under-
corrects blockage and buoyancy for bluff bodies such as automobiles, due to
large wake effects. A method of accounting for the large wake, derived by
the Lockheed-Georgia Company, uses the test section ceiling static pressure
distribution to arrive at the blockage correction. For this ceiling static
pressure signature method, test section static pressures along the ceiling
centerline are measured with the model both in and out of the test section.
Lockheed reported that a comparison of the data using the two blockage
methods showed that coefficient data based on the area ratio method are higher
than those based on the ceiling static pressure signature method by 2.8 to 12
percent for the range of vehicles tested (Ref. 4).
Reference 4 provides wind tunnel test results for four additional
vehicles examined in this study as well as a retest of the 1977 Ford Granada
reported in Reference 3. The data presented are based on both the area ratio
blockage correction method and the ceiling pressure signature method.
""Lockheed values of frontal area were generally within +_ 1 percent of values
determined by Aerospace.
4-3
-------
A comparison of the LSWT test results with the values derived in
this study are shown in tabular form in Table 4-2 and graphically in Figure
4-1. The wind tunnel test results were given in terms of C^A and were der-
ived from F^/Q, where Fn is the drag force in pounds and Q is the dynamic
U 2 ^
pressure in Ib/ft . The values of CD shown for the wind tunnel results were
derived by dividing the reported value of C_A by the projected frontal area,
AR, as determined by the present study.
As indicated in Table 4-2, the calculated values of C~ developed in
this study average 5. 0% lower than the wind tunnel results based on the area
ratio blockage correction method and 5.9% higher than the wind tunnel results
based on the ceiling static pressure signature method. Thus, on average, the
calculated values of C_ would appear to be in good agreement with the wind
tunnel results. As indicated in Table 4-2, however, the data also shows a
high degree of dispersion; the standard deviation of the area ratio data set is
8. 1% compared to a mean deviation of -5.0%, while the static pressure data
set shows a standard deviation of 7.4% compared to a mean deviation of 5. 9%.
The dispersion in the area ratio set is due primarily to the results obtained
for the Pinto, the Mustang II, the 1978 Volare Station Wagon, and to a lesser
degree, to the Porsche 924. In the case of the static pressure data set, the
primary outlier is the 1973 Le Baron. Further discussion of these outliers
is provided below.
The vehicles which show the greatest disagreement with the area
ratio wind tunnel results are the Pinto (-18.4%), the Mustang H (-16.9%), the
1978 Volare Station Wagon (-11.9%), and the Porsche 924 (+8. 3%). In the
case of the Pinto, an examination of the individual components of C_ given in
Table 4-1 shows that C-. , the front end drag coefficient, is one of the lowest
the data set. This value is due primarily to the large (6 in.) upper edge
radius, R , above the grille at the hood-front breakline. The Mustang H,
however, does not show any single component of CD that is noticeably lower
than the other vehicles. Similarly, the disagreement indicated for the 1978
Volare Wagon is not explainable in terms of component drag peculiarities.
It should be noted that calculated CD values for the 1978 model Volare are
4-4
-------
Table 4-2. Comparison of Calculated Aerodynamic Characteristics
with Wind Tunnel Test Results
Vehicle
'77 Chevrolet Impala
'77 Ford Granada
'77 Ford Granada
•77 Ford Mustang II
•77 Ford Pinto
'77 Plymouth Arrow
'77 Plymouth Volare
Wauon
•77 Porache 924
>77 VW Rabbit
'76 Chevrolet Inipala
>78 Plym.Volaro Wagon
'78 Chrysler LeDaron
'7B Cutlass Supreme
Calculated Results
Projected
Frontal Area.
ARftZ
24.14
22.22
19.29
19.46
17.82
22.76
18. SB
19.77
23.89
22.79
23.05
21.58
'(talc. - W. T.)/W.T.
ZAl SO niph.
V2'
0.562
0.575
0,513
0.496
0.528
0.554
0.410
0.489
0.557
0.565
0.585
0.547
C A(2)
CDA
13.54
12.77
9.90
9.67
9.40
12.63
8. 13
9.64
13. 31
12.88
13.48
11.80
Wind Tunm
Area Ratio
Blockade Method
CD<2,.W
0.588
0.602
0.580
0,617
0.608
0.545
0.558
0.397
0.523
0.577
0.641
0.545
0.5HO
r A'Z)
CDA
14.I6<4>
I3.36<4>
12.88<5>
ll.90(4>
ll.85«>
9.70<«>
12.72«4>
7.50«4>
10.36'4'
13.79(5)
• 4.6l'5'
12.S7(S)
I2.5l'5>
1 Reaulta
Pressure Signature
Blockage Method
c (2), (3)
0.535
0.521
0.584
0.502
0.538
C A(Z)
CDA
11.90<5»
12.45<5'
I3.31<5'
11.58<5>
ll.6l'5»
'Derived from CDA/AR 'Reference 4 Mean % d CQ
Refe rence 3 SUnda rrf DevlaUon „
* A CD"»
Area Ratio
Method
-4.4
-4.5
-0.9
r!6.9
-18.4
-3. 1
-0.7
+ 8. 3
-6.5
-3.5
-11.9
+ 7.3
-5.7
-S.O
8. 1
Pressure
Signature
Method
+7.5
+6.9
-3.3
+ 16.5
+ 1.7
+ 5.9
7.4
-------
0.70
0.6!
0.60
0.55
1. 1977 Chevrolet Impala
2. 1977 Ford Granada
3. 1977 Ford Mustang 11 Notch back
4. 1977 Ford Pinto
5. 1977 Plymouth Arrow
6. 1977 Plymouth Volare Station Wagon
7. 1977 Porsche 924
8. 1977 VW Rabbit
9. 1978 Chevrolet Impala
10. 1978 Plymouth Volare Station Wagon
11. 1978 Chrysler LeBaron
12. 1978 Oldsmobile Cutlass Supreme
O Area Ratio Method, Ref. 3
a Area Ratio Method. Ref. 4
0 Pressure Signature Method, Ref. 4
202 /
10 Xmio
05
. # '
6 EJJ2 /
/
/
/
08<
/
G3
04
/
/
/
/
s\
,'*
0.35 0.40 0.45 0.50
Cn, LSWT
0.55
0.60
0.65
Figure 4-1. Comparison of Test and Calculated Values of
Aerodynamic Drag Coefficient
4-6
-------
very similar to those for the 1977 model, which showed excellent agreement
•with the test result (-.7%). The similarity in component C 's would be
expected in view of the minor styling changes between the two model years.
The value of Gn derived for the Porsche 924 was found to be ex-
tremely sensitive to the front hood configuration and the related effects on
C and C-. . The values of C_ and C~ shown in Table 4-1 were based on
D, UQ JJ, Uj
the assumption that the front of trie hood began at the top edge of the front
bumper. The selection of this line of demarcation resulted in the low value
(0.075) for Cn and the comparatively high value (0.055) for Cn . Examina-
tion of the front end detail of the Porsche 924, shown in Figure 4-2, suggests
the possibility of using an alternate breakline between the hood and front end;
that is, the line of intersection of two planes on the hood. This breakline
would result in a larger front end area, A^, and a smaller hood area
£
(A, - A^). The net effect would be to reduce C-, by 0.010. The net effect
h r JJ-i
on Cp. , however, is difficult to assess since an effective upper edge radius,
1
R , cannot be determined. As seen in Figure 4-2, this front-hood breakline
is essentially the intersection of two planes, with a very small radius of
curvature (i.e., 1/16 in.) at the point of intersection. However, since the
angular change at this breakline is on the order of 25 to 30°, it would seem
that some larger effective upper edge radius should be used. Indicative of
the sensitivity of C_ to this upper edge radius is the net change in C
which occurs when the value of R^ is altered. If, for example, the value of
1/16 in. were used, C_ would increase by 0.024 over that shown in Table
1
4-1. K, on the other hand, a value of say 6 in. were assumed, Cn would
be reduced by 0.040. 1
Based on the foregoing discussion, it would appear that the derived
value of C_ for the Porsche may be too high, although any revision to the
derived value would require a more definitive assessment of the upper edge
radius than is provided for in the technique used in this study.
Of the five vehicles available for comparison with the wind tunnel
data based on the ceiling static pressure blockage correction method, the
4-7
-------
00
Figure 4-2. Porsche 924, Front End Detail
-------
1978 Chrysler Le Baron shows the greatest disagreement; the calculated
value is 16.5% higher than the wind tunnel results. An examination of the
individual C_ components for this vehicle (Table 4-1) does not reveal any
significant differences from the other vehicles. Hence, the reason(s) for
the discrepancy in results is not apparent.
4-9
-------
SECTION 5
CONCLUSIONS AND RECOMMENDATIONS
The aerodynamic drag coefficient, C_, as developed by the "drag
build-up" method, was determined for a total of twenty 1977/1978 model
year vehicles. Results of the low speed wind tunnel tests conducted by the
Lockheed-Georgia Company (based on an area ratio blockage correction
method) on twelve of the vehicles were available for comparison, and
showed that the empirically derived value of C_. for nine of the twelve
vehicles was within +10% of the wind tunnel results. Of these nine vehicles,
the value of Cn determined for the Porsche must be considered somewhat
suspect in view of the uncertainties in defining the hood-front breakline and
the associated edge radius. The other three vehicles (the Mustang II, Pinto,
and 1978 Volare station wagon) were found to be 12 to 13% lower than the
wind tunnel results. The reason for this difference is not apparent in the
case of the Mustang II and Volare. The low value of Cn calculated for the
Pinto may be due in part to its low value of Cn (0. 100) which derives from
the large edge radius (6 in.) at the hood-front breakline above the grille.
Wind tunnel test results using the ceiling static pressure signature
blockage correction method were available for comparison for five of the
vehicles evaluated. The empirically derived C_^ values for four of the five
vehicles were also within +10% of the wind tunnel results. The value of C_
~~ D
for the remaining vehicle (the Le Baron) was found to be 16.5% higher than
the wind tunnel results.
In summary, the empirical evaluation of the vehicle aerodynamic
drag coefficient by the drag build-up method showed good agreement with
the wind tunnel results in most, but not all, cases. Several factors are
believed to have contributed to the lack of agreement. One is the subjective
interpretation required in evaluating certain edge radii. A second factor is
the high degree of sensitivity of the results to the ratio of the edge radius to
5-1
-------
the projected length of that radius (R/E). This factor was found to be parti-
cularly important in the case of C_ , but it also affected the evaluation of
C_ and C_ , although to a lesser degree. While this effect was recognized
in developing the equations for evaluating the forebody drag components
(Ref. 2), the results of this study suggest that the method could be improved
by modifying some of the simplifying assumptions made In defining the effect
of rounded edges.
Beginning with 1979 model year vehicles, the method used by EPA for
establishing dynamometer power absorption settings for emission certification
and fuel economy testing of light duty vehicles will be based on vehicle equiv-
alent inertia weight, vehicle reference frontal area, and vehicle protuberances,
using a formula in which aerodynamic drag road load effects are approximated
by the relation
HP = cA + P
where A is the vehicle projected frontal area, c is a constant which has differ-
ent values for fastback and non-fastback vehicles, and P is a protuberance
factor. This equation implicitly assumes that the contribution to the aero-
dynamic drag coefficient from the vehicle body (excluding protuberances) is
equal (constant) for all vehicles in each configuration category.
Using C's developed from the above relation, the accuracy of assum-
ing constant drag coefficients can be evaluated and compared to the accuracy
of the drag coefficient buildup method of this report. However, it must be noted
that the wind tunnel testing, which encompasses two different blockage correc-
tion methods, provides comparable data for only five of the 20 vehicles eval-
uated in this study (see Table 4-2). This small sample size precludes a rigor-
ous statistical analysis of the accuracy of the methods.
For the five vehicles that can be compared to both sets of wind tunnel
results, a simple computation of the average disparity^ between Cn calculated
"defined as£[ %& CD|/N
5-2
-------
and Cn tested yields (a) 6.2% and 7.2% for the drag buildup method as refer-
enced to the area ratio and pressure signature blockage correction test results,
respectively, and (b) 3.3% and 10.5% for corresponding values derived from the
EPA dynamometer relation. Slight differences in numerical values notwith-
standing, the significant aspect of this result is that the disparities are small
and similar in magnitude for the two methods. Thus, for this specific set of
five vehicles, the use of a relation based on a constant average C_. for the
vehicle body with correction for protuberances appears to provide as accurate
a prediction of the vehicle C_. as is obtained from the drag coefficient buildup
approach.
It is concluded that the data developed in this study does not indicate
an increase in the accuracy of predicting drag coefficient using the drag coeffi-
cient buildup approach compared with the accuracy obtained by assuming a
constant average drag coefficient for all similar vehicles. Therefore, no
changes to the current relation defining dynamometer road load horsepower
settings are recommended on the basis of the present work.
5-3
-------
REFERENCES
1. Federal Register, Vol. 4Z, No. 176, September 12, 1977.
2. Estimation, of Vehicle Aerodynamic Drag, Aerospace Report No.
ATR-77(7359-l), The Aerospace Corporation, El Segundo,
California, October 1976.
3. E. A. Payne, Low Speed Wind Tunnel Test to Determine the
Aerodynamic Characteristics of Thirteen Automobiles, Report
No. LSWT 211, Lockheed-Georgia Company, Marietta, Georgia,
May 1977.
4. D. L. Bruce, Determination of Automobile Aerodynamic
Characteristics, Low Speed Wind Tunnel Tests, Lockheed-Georgia,
Company, Marietta, Georgia, June 1978.
R-l
-------
APPENDIX A
DRAG PREDICTION METHOD
The drag prediction technique developed by The Aerospace
Corporation in Reference 2 breaks the drag of a road vehicle into 11 dis-
crete contributions. The reference area, A_, which is used to normalize
the component drag contributions, is taken to be the projected frontal area
of the vehicle including tires and underbody details but excluding protuber-
ances such as mirrors, antenna, and luggage carriers. The contribution
of a component is a function of its size so that typically a representative
area A. of each component, as well as A_, appear in the formulas. The
relevant vehicle dimensions and areas are illustrated in Figure A-l. The
details of the drag build-up are presented in the following pages.
A-l
-------
IS)
A - LxW
P
W
r A,
0
Figure A-1. Vehicle Dimensions
-------
Front End Drag Coefficient, C^
'A \( / \ / \ / \
-^M 1. 0 - 2. 79 (•£•! + 0. 82 f-g-K - 5. 21 (-^-1
J£.l 1 O - 7 •« q I •"•
^ST" It \ Ji* v» ™ t,» C.J \ ^Sf
(1)
where
Ap = projected frontal area of the vehicle including tires and
* underbody details, m2 (ft2)
A— = front end projected area, m (ft )
£
R = edge radius, m (ft)
E = projected length of the edge radius, m (ft)
and the subscripts u, 1, and v refer to the upper, lower, and vertical edges
of the front end, respectively. The (R/E). are to be taken as 0.105 when
the estimated values exceed this magnitude.
Windshield Drag Coefficient, Cp
=0.707
^2
where
, cos2y (2)
= projected area of windshield, m (ft )
y = slope of the windshield measured from the vertical, deg
ft = 27
and the subscripts u' and v1 refer to the roof-windshield intersection and the
windshield posts, respectively. The value of cos£ is to be taken as zero
for V larger than 45° and the (R/E). are to be taken as 0.105 for estimated
values exceeding this magnitude.
A-3
-------
Front Hood Drag Coefficient, Cp
where
= projected area of body below the hood-windshield
intersection, m^ (ft2)
= length of hood in the elevation or side view, m (ft)
and the quantity (A^ - AF) is to be taken as zero if it is negative.
Rear Vertical Edge Drag Coefficient, C^
•V-'-^W'-W0-105!
/E. \ /R ' >
= -0. 02 (TT for -^-) > 0.105
\ « /
where
RV = radius of rear vertical edges, m (ft)
W = projected width of rear vertical portion, m (ft)
E, = projected length of rear vertical edge radius, m (ft)
H = vehicle height, m (ft)
Base Region Drag Coefficient, C,
(5)
A-4
-------
where
= projected area of flat portion of base region
A-, = projected area of upper rear or hatch portion of base
region measured from the upper rear roof break (or for
smoothly curved rooflines, that point where the roofline
slope is 15°) to the top of the flat base, m2 (ft2)
Cn = drag coefficient of the flat base
DB
CD - drag coefficient of the upper rear or hatch portion of
H the base region
and the ratio (Cn /Cn ) is shown in Figure A-2 as a function of 4>t the
H B
angle of the line r?om tfie upper rear roof break to the top of the flat base
as measured from the horizontal.
Underbody Drag Coefficient, CD
Cn = 0. 025 (0. 5 - x/L) (-T2-) for 0 < x/L < 0. 5
^6 \ R/ (6)
= 0 for x/L > 0. 5
where
x = smoothed forward length of the underbody, m (ft)
L = vehicle underbody length, m (ft)
2 2
A = projected plan area of the vehicle underbody, m (ft)
Wheel and Wheel Well Drag Coefficient. CD
CD =0.14 (7)
Rear Wheel Well Fairing Drag Coefficient, CD
Cf. = -0. 01 for rear wheel well covered
(8)
C— = 0. 0 for real wheel well not covered
8
A-5
-------
2.0
CO
o
o
x 1.8
o
o
5 u
i—
LiJ
G 0-8
o
o
<:
a:
o
0.4
0
NOTCHBACK
HATCHBACK
I
I
I
0 10 20 30 40 50 60 70
HATCHBACK SLOPE, ~ deg
FASTBACK
o
90
100
Figure A-2. Hatch back-Notch back Drag Coefficient Ratio
-------
Protuberance Drag Coefficient, Cp __
D9 AR
where
A = projected area of jth protuberance, m (ft )
Pj
Bullet Mirror Drag Coefficient, Cn
Ai
C_ = 0.4-r (10)
D10
where
A., = projected area of mirror with bullet fairing, m (ft )
Cooling Drag Coefficient, C—
where
A = radiator area, m (ft )
u = exit velocity of cooling air from radiator, m/sec (mph)
u = vehicle speed, m/sec (mph)
(ur/u) = 0.233 [1.0 - k (u/100)2]
and
k = 1.146 (m/sec)"2 [or 0.229 (mph)"2]*
"Represents a correction to Ref. 2, published as .299.
A-7
-------
APPENDIX B
Sample Calculation
Vehicle 1977 Impala
License No. 807SMV
1.625 in.
65.45 in.
(R/E)u 0.0248 (max. = 0.105)
R£ 0.935 in.
Ej 68.41 in.
(R/E). 0.0137 (max. = 0.105)
1.029 in.
17.74 in.
0.0580 (max. =0.105)
9.657 ft*
24.137 ft*
'D '
/AF\
; a0.707US.)
Dl \AR/
=0.1785
(AF/AR) 0.4001
2.79(-|-).. + 0.82
ru
(£-} -
\*h
'R \
.T/v
RU, 2.5 in.
EU, 50.43 in.
Rv. 1. 5 in.
Ev. 15. 28 in.
(R/E)u, 0.0496 (max. = 0.105)
(R/E)v, 0.0982 (max. = 0.105)
B-l
-------
Sample Calculation (Continued)
CD (Cont'd)
53*
5. 517 ft*
AR 24. 137 ft
=0.0286
2y = 106° (cos£= 0 fory> 45°)
(AW/AR) 0.2286
,02 - 2.79
L, COS0-5.21 -£-
cos
12. 708
D
5.118ft
9.657ft2 A,, 24.137ft2
0.707
I /5,, , Fn /\
TI J '
'D4'
=0.0104
RV 0.854 in.
W 67. 08 in.
18. 65 in.
H 43. 10 in.
-0.02(4)
CD =0.0010
4
0.0127
0* 4327
for l-^-)< 0.105
/R \
for!
> 0.105
B-2
-------
Sample Calculation (Continued)
9. 157 ft
24. 137 ft
20°
8.629ft*
0.3794
CD CD °' 925
H/ £
0.3575
» from Fi«- A'2)
CD = 0.1065
5
'V
L 211.50 in.
W 58. 55 in.
Cn =0.025 (0.5 -x/L)
D6
A (=L x W) 86. 00
P
ft)
for 0 < x/L < 0. 5
CV°
for x/L > 0. 5
Cn = 0.0445
D6
CD = 0.140
'D '
-. = 0 (rear wheel wells not covered)
8
-. = -0.01 (rear wheel well covered)
D8
B-3
-------
Sample Calculation (Continued)
A_(mirror) 0.1591 A^ AD 24.137
<
r
D9
=0.0073
9
c . °'4AM
D10 *R~
C =0.0
k « 1. 146 (m/sec)"2
= 0.229 (mph)"2
/ur/u\ = 0.233 [l.O - k (u/100)2]
A (= L x h ) 3.438 ft2, Ap 24.137 ft2
r r r ———i^^— iv. •———•—•
B-4
-------
Sample Calculation (Continued)
j (Cont'd)
-II. /A \/u \[ >u Y)
CD =l.8f1^)(-Tf-)|l.0.0.75(-^)i =0.3303 (T^-)® 50 mph
C^ = 0.0470
CD:
0.5618
B-5
-------
APPENDIX C
VEHICLE DIMENSIONS AND AREAS
The individual vehicle dimensions and areas which are required to
evaluate the aerodynamic drag coefficient according to the methods outlined
in Appendix A are given for each of the 20 vehicles evaluated.
When more than one edge radius is indicated for a given portion of
the vehicle, the effective value was determined as follows:
where
R = effective edge radius
Ri = specific radius over length Ei
Ei = projected length. associated with a given radius, Ri
The parameter (R/E) was then taken to be the ratio of the effective
edge radius to the sum of the individual edge lengths, Ei.
C-l
-------
VEHICLE DIMENSIONS/ARE AS
Vehicle: Manufacturer Chrysler
Make Plymouth Arrow
Model 2-dr. Coupe
Model Year 1977
License No/VTN Dlr 2529 (Calif. )/7P24K78901899
Projected Frontal Area, ft 17,82
C_ : Frqnt_End Drag Coefficient
—— Location
1. hood portion R 0.125 in. E 46.59 in. (R/E) 0.0027
u: Uj u —.
2. above headlights R 0.25 in, E 4.24 in,
U2 U2
1. body sheet metal Rj 0.125 in. Et 51.45 in. (R/E). 0.0024
below bumper L1 zl / "—•
1. upper portion of R 0.375 in. E 6 in. /R/E) 0.0625
fender vl Vl v '
2. lower portion of R 1 in. E 2.5 in.
fender 2 2
3, upper portion of RV 1.625 in. EV 4.5 in.
bumper and lower 3 3
sheetmetal
4, lower portion of Ry 1.313 in. EV 3 in.
bumper 4 4
Ar 6. 985 ft2
Cjj : Windshield Drag Coefficient
—— Location
1. roof windshield RU, 4.5 in. EU, 39.76 in. (R/E)V 0.113*
intersection ~
2. A-post RV, 3 in. EV, 13.25 in. (R/E)v, 0.226*
3. windshield slope y 60°
from vertical use 0,105
C-2
-------
Vehicle: 1977 Plymouth Arrow (Continued)
C_ : Front Hood Drag Coefficient
Location
1. front area below windshield A. 9.413 ft
2. front end area AF 6.985 ft
3. hood length 1 4,028 ft
CD : Rear Vertical Edge Drag Coefficient
— Location
1. upper portion of R 0.875 in. E, 10.5 in. R 1.030 in.
vertical section vl 1 v
2. lower portion of RV 1 in. E, 3 in. E, 18.75 in.
vertical section 2 2
3. upper portion of R 1.5 in. E, 2. 25 in. W 57. 50 in.
bumper 3 3
4. lower portion of RV 1.25 in. E^ 3 in. H 37.07 in.
bumper 4 4 ~~~
CD : Base Region Drag Coefficient
Location
1. area of base region A« 7.845 ft
2. area of hatch portion A,, 4.267 ft
3» rear slope from horizontal
-------
Vehicle: 1977 Plymouth Arrow (Continued)
C_ : Protuberance Drag Coefficient
Location
1. antenna Ap 0.0609 ft2 £Ap 0.0609ft2
Cn : Bullet Mirror Drag Coefficient
D10
• "• Location
1. one each side ^T.I ^* ^2^ ^
Cn : Cooling Drag Coefficient
radiator height 12.125 in,
radiator width 18.375 in. Ar 1. 547 ft2
C-4
-------
Vehicle: Manufacturer Chrysler
Make Plymouth Velar e
Model Station Wagon
Model Year 1977
License No/VTN Dlr 2529 (Calif. )/HH45G7G135783
Projected Frontal Area, ft 22. 76
CD : Front End Drag Coefficient
- Location
1. above headlights RU 0. 125 in, EU 20 in, (R/E) 0. 0092
2. above parking R 2 in, E 16. 94 in,
lights U2 U2
3. above grille RU Q. 0625 in. EU 27.23 in.
J J
1. botton of bumper R, 1.75 in. E- 66.30 in. (R/E). 0.0264
*1 ll /
1. at fender R 0. 563 in. E 9 in. (R/E) 0.0974
vl vl v
2, upper portion of R 3.75 in. E 2.75 in.
bumper V2 V2 ~~~"~~— —
3. lower portion of R 2.25 in. E 4.25 in.
bumper V3 V3
2
Ar 8.861 ft
CD : Windshield Drag Coefficient
.- Location
1. roof-windshield R , 1.625 in. E , 49. 03 in. (R/E) , 0,0331
intersection
2. A-post R^, 1. 125 in. EV, 16.24 in. (R/E) , 0.0693
3. windshield slope y 51° _ AW 5. 888 ft
from vertical
C-5
-------
Vehicle: 1977 Volare Station Wagon (Continued)
CD : Front Hood Drag Coefficient
Location
1. front area below windshield A 11.783 ft2
2. front end area Ap 8.861 ft2
3. hood length L^ 4.508 ft
C_ : Rear Vertical Edge Drag Coefficient
—— Location
1. vertical portion RV 0.688 in. Eb 7 in. R.. 0.996 in.
above bumper 1 1 ~ "
2. upper portion of R 1,875 in. E, 2 in. E, 15 in.
bumper V2 2
3. lower portion of RV 1.063 in. E^ 6 in. W 65.87 in.
bumper 3 3
H 42.17 in.
^ : Base Region Drag Coefficient
11
1.
2.
3.
Location
area of base region
area of hatch portion
rear slope from horizontal
A^ 7.360ft2
AJJ 9.530ft2
* 45° Cn /Cn
1.0
H "B
rag Coefficient
Location
C_ : Underbody Drag Coefficient
u .
1. underbody length L 16.507 ft
2. underbody width W 4.854 ft Ap(= LXW) 80.13 ft2
C-6
-------
Vehicle: 1977 Volare Station Wagon {Continued)
cr> : Protuberance Drag Coefficient
9
- Location
1. mirrors (one each side) A 0,2417 ft
PI
2. antenna A 0.0260 ft2
p2
3. luggage rack Aw 0.1828 ft2 £A 0.4505 ft2
p3 p.
CD : Bullet Mirror Drag Coefficient
Location
1. none
n : Cooling Drag Coefficient
radiator height 17.25 in.
radiator width 26.25 in. A 3.145ft2
C-7
-------
Vehicle: Manufacturer Chrysler
Make Le Baron
Model 4-dr. Sedan
Model Year 1978
License No/VIN 311 TYY (Calif. )/FP41J8G145760
Projected Frontal Area, ft 23.05
C— : Front End Drag Coefficient
— Location
1. above headlights RU 1.5 in. EU 30.78 in. (R/E)u 0.0122
2. above grille R 0.031 in. E 31.38 in.
U2 U2
1. center segment R, 2.75 in. E. 31.03 in. (R/E). 0.0318
of bumper ^ 1 *>\ *
2. outer segments R« 1.563 in. E. 35,51 in.
of bumper ^2 ^2
1. headlight trim, RV 0.75 in. EV 1.5 in. (R/E)v 0.0618
horizontal portion 1 1
2. fender above R 0.469 in. E 2 in.
headlights V2 2
3. headlight trim, Ry 0.031 in. Ey 7.5 in.
vertical portion 3 3
4. bumper R 2.625 in. E 5.5 in.
V4 4
AF 8.991ft
2
CD : Windshield Drag Coefficient
— (Location)
1. roof-windshield RU, 2.625 in. EU, 47.90 in. (R/E)u, 0.0548
intersection ——
2. A-post
3. windshield slope y 51.5° A ' oin ^2
from vertical
R, 1.125 in. E, 16.04 in. (R/E), 0.0701
C-8
-------
Vehicle: 1978 Le Baron, (Continued)
*"• •
3
•MMI^™»
1.
2.
3.
CD :
•^••MM*
1.
2.
3.
4.
!v
i.
2.
3.
CD *'
6
1.
2.
Front Hood Drag Coefficient
Location
front area below windshield
front end area
hood length
A^ 11.500ft2
A^ 8. 991 ft2
1*. 4.766ft
Rear Vertical Edge Drag Coefficient
Location
vertical portion R 1.375 in.
of body vl
sloping portion R 1.281 in.
of body V2
upper portion of R 1. 875 in.
bumper 3
lower portion of R 1.25 in.
bumper 4
Base Region Drag Coefficient
Location
area of base region
area of hatch portion
rear slope from horizontal
Underbody Drag Coefficient
Location
underbody length L 16.
underbody width W 4.
E, Sin. R 1.394 in.
Et 3 in. E^ 18. 5 in.
^ 2. 5 in. W 66. 97 in.
E^_ Sin. H 42. 51 in.
°4
A,, 8.770ft2
A« 7. 866 ft2
6 22° Cn /C 1.06
DH DB
801 ft
818 ft A (= LXW) 80.94 ft2
C-9
-------
Vehicle: 1978 Le Baron (Continued)
CD : Protuberance Drag Coefficient
—-— Location
1. mirrors (one each side) A 0.2475 ft
2. antenna A 0.0394 ft2
3. hood ornament A 0.0104 ft2 £A 0.2973 ft2
P3 pj —
CD : Bullet Mirror Drag Coefficient
Location
1* none
C_ : Cooling Drag Coefficient
radiator height 17 in.
radiator width 25.5 in, Ar 3.0104 ft2
C-10
-------
Vehicle: Manufacturer Chrysler
Make Plymouth Volare
Model Station Wagon
Model Year 1978
License No/VIN Dlr 2529 (Calif. )/HL45C8B170977
Projected Frontal Area, ft2 22.79
C-. : Front End Drag Coefficient
- Location
1. above headlights RU 0. 125 in. EU 19.48 in. (R/E)u 0.0075
2. above parking R 1.5 in. E 18.10 in.
lights U2 U2 -
3. above grille R 0.0625 in. E 26. 97 in.
U3 U3 -
1. bottom of bumper R. 1.375 in. E, 66.76 in. (R/EL 0.0206
l\ t\ - I
1. at headlights R 0.438 in. E 9 in. (R/E> 0.0871
vl vl ' v
2. upper portion of R 3.25 in. E 2.75 in.
bumper 2 V2
3. lower portion R 2.25 in. E 4. 5 in.
°f bUmper 3 "3 A 8.727ft2
CD : Windshield Drag Coefficient
. Location
1. roof-windshield R . 2. 5 in. E... 48.27 in. (R/E) . 0.0518
intersection u " " u -
2. A-post Rv, 1 in. EV, 17.64 in. (R/E>v, 0. 0567
3. windshield slope y 51° _ A... 5. 906 ft2
from horizontal ————— — ____^___
C-ll
-------
Vehicle 1978 Volare Station Wagon (Continued)
C_ : Front Hood Drag Coefficient
^1
1.
2.
3.
•
4
•^•^•M
1.
2.
3.
D5:
MHMM
1.
2.
3.
V
1.
2.
Location
front area below windshield
front end area
hood length
A,. 11.622ft2
A^, 8. 727 ft2
Lu 4. 537 ft
Rear Vertical Edge Drag Coefficient
Location
vertical portion R 0. 688
above bumper vl
upper portion of R 1.625
bumper 2
lower portion R 1. 125
of bumper V3
Base Region Drag Coefficient
Location
area of base region
area of hatch portion
rear slope from horizontal
Underbody Drag Coefficient
Location
underbody length L
underbody width W
in. E 7 in. R 0. 978 in.
in. E, 2 in. E, 14 in.
2 D ""
in. Eb 5 in. W 65.56 in.
3 H 40. 50 in.
A,, 6. 859 ft2
An 9. 476 ft2
0 45° Ct, /C
fcH DB i—-
16.462 ft
4.882ft Ar(= LXW) 80T *A ft2
C-12
-------
Vehicle: 1978 Volare Station Wagon (Continued)
C_ : Protuberance Drag Coefficient
Q
• Location
1. mirrors (one each side) A 0,2570 ft
2. antenna A 0.0267 ft2
b
3. luggage rack A 0.1828 ft2 £A 0.4665 ft2
P3 Pj
C : Bullet Mirror Drag Coefficient
10
i Location
1. none
: Cooling Drag Coefficient
11
•«HBMMW
radiator height 18.75 in.
radiator width 22.0 in. AT 2.865 ft2
C-13
-------
Vehicle: Manufacturer Ford
Make Granada
Model 4-dr. Sedan
Model Year 1977
License No/VIN 132 RTT(Calif.)/7W81F121893
Projected Frontal Area, ft 22. 22
Y
i.
2.
3.
1.
1.
2.
: Front End Drag
Location
at fender
above headlights
above grille
bottom of
bumper
at fender
at bumper
Coefficient
Ru
ul
R
U2
R
U3
R/
*1
R
"l
R
V2
1.875 in.
2.625 in.
0.0625 in.
1.125 in.
0. 125 in.
2.25 in.
E . 1. 25 in.
Ul
E 28 in.
U2
E 33.5 in.
U3
E, 62. 61 in.
*1
E 12 in.
"1
E 7 in.
V2
(R/E).. 0.
(R/E)^ o.
. (R/EJv-O*.
AF 8.943
0198
0180
•— — ~
0478
CD : Windshield Drag Coefficient
Location
1. roof-windshield RU, 4.5 in. EU, 47.62 in. (R/E)U, 0.0945^
intersection
2. A-post R^t 1.625 in. EV. 14.87 in. (R/E).., 0.109^
3. windshield slope y 56° A^ 5.312 ft *exceedg
from vertical uge Q
C-14
-------
Vehicle: 1977 Ford Granada (Continued)
C : Front Hood Drag Coefficient
.11 - Location
1. front area below windshield A 11.033 ft2
2. front end area Ap 8.943 ft
3. hood length 1 4.648 ft
C_ : Rear Vertical Edge Drag Coefficient
- Location
1. vertical portion R 1. 125 in. E, 1.75 in. R 1. 576 in.
above tail light vl Dl v
2. tail light portion R, 0.6875 in. E, 4.5 in. E, 21. 51 in.
V2 °2 - °
3. vertical portion R 1.0 in. E, 2. 5 in. W 64. 60 in.
below tail light V3 D3
4. sloping portion R 0. 906 in. E, 5.26 in. H 38.21 in.
above tail light V4 D4 "~
5. bumper RV 2.875 in. 7. 5 in.
C_ : Base Region Drag Coefficient
DC — - — ^— — —
- Location
1. area of base region A- 10.00 ft
2. area of hatch portion A,, 6. 24 ft2
3. rear slope from horizontal 0 20° _ CD /CD 0. 925
H £
C_ : Underbody Drag Coefficient
jj -
— — Location
1. underbody length L 16.281 ft
2. underbody width W- 4.814ft A (= LXW) 78.38 ft2
- p -
C-15
-------
Vehicle: 1977 Ford Granada (Continued)
C_ : Protuberance Drag Coefficient
9
Location
1. mirror A 0.1212 ft2
2. antenna A 0.0269 ft2
fa
3. hood ornament A 0.0113 ft2 IA 0.1594 ft2
C_ : Bullet Mirror Drag Coefficient
i£- Location
1. none
— : Cooling Drag Coefficient
^11
radiator height 18 in.
radiator width 26.5 in. Ay 3,313 ft2
C-16
-------
Vehicle: Manufacturer Ford
Make LTD II
Model 4-dr. Sedan
Model Year 1977
License No/VIN 404 SYY (Calif. )/7A31H156239
Projected Frontal Area, ft 23.22
r : Front End Drag Coefficient
_.. .- Location
1. at fender RU 1.375 in. EU 20 in. (R/E)U 0.0090
2. above headlights R 0.563 in. E 17 in.
U2 2
3. above grille R 0.0625 in. E^ 28.9 in.
1. bottom of R. 0.50 in. E- 67.5 in. (R/E) 0.0074
bumper Ll Ll *
1. at fender R 0.0625 in. E 12.5 in. (R/E) 0.0322
vl (use 0) vl v
2. bumper RV 1.75 in. EV 7 in.
Ar 9.024ft2
C : Windshield Drag Coefficient
_ 2- Location
1. roof-windshield RU, 4.75 in. EU, 46.57 in. (R/E)u, 0.1020
intersection
2. A-post Rv, 1.125 in. EV, 13.45 in. (R/E)v, 0.0836
3. windshield slope y 59° AW 4.993 ft
from vertical
C-17
-------
Vehicle: 1977 Ford LTD n (Continued)
CD : ^ront Hood Drag Coefficient
—— Location
1. front area below windshield Ah 11.375ft2
2. front end area Ap 9.024 ft
3. hood length L^ 5.407 ft
CD : Rear Vertical Edge Drag Coefficient
• Location
1. fender R, 0.0625 in. EL 14.95 in. R 1.079 in
Vl bl v '
2. bumper R 3.25 in. E, 7 in. E, 21.95 in.
V2 D2 ' b ~~ •
W 65.51 in.
H 40. 52 in.
C_ : Base Region Drag Coefficient
~~"~ Location
1. area of base region Afi 10.174 ft
2. area of hatch portion A-, 6.040 ft2
3. rear slope 19°
_ : Underbody Drag Coefficient
*J^
Location
1. underbody length L 16.242 ft
2. underbody width W 5.113 ft A (= LXW) 83. 05
C-18
-------
Vehicle: 1977 Ford LTD II (Continued)
C_ : Protuberance Drag Coefficient
9
- • Location
1. mirror A 0.1153 ft2
2. antenna A 0.0269 ft
3. hood ornament A 0. 0247 ft2 £ A 0. 1669 ft2
P3 - p. -
C-. : Bullet Mirror Drag Coefficient
^10
-- iii- Location
1. none A,. 0
n : Cooling Drag Coefficient
radiator height 19.5 in.
radiator width 28 in. A 3.792 ft2
C-19
-------
Vehicle: Manufacturer Ford
Make
Model
Model Year
License No/VTN
Projected Frontal Area, ft
Mustang II
2-dr. Coupe (Notchback)
1977
397 SYY (Calif. )/7R02Z 13 1023
19.29
CD : Front End Drag Coefficient
1_
1.
2.
3.
1.
1.
2.
3.
!v
i.
2.
3.
Location
above headlights
above grille
between head-
lights and grille
bottom of
bumper
at headlights
upper portion of
bumper
lower portion of
Windshield Drae
Location
roof -wind shield
intersection
A-post
windshield slope
R
ul
R
U2
R
U3
R.
R
Vl
R
V2
R
0.031 in.
0.0625 in.
1.75 in.
0.625 in.
0.031 in.
2. 5 in.
2.375 in.
E
Ul
E
U2
E
U3
E
E
Vl
E
V2
E
14 in.
33.75 in.
8 in.
58 in.
8.25 in.
3 in.
3 in.
Coefficient
Ru'
R ,
y
6 in.
1.75 in.
59°
Eu'
*v
AW-
41.69 in.
12.35 in.
4. 228 ft2
(R/E)u 0.0053
(R/E), 0. 0108
1 •
(R/E) 0. 0733
if ^"^^^•^^•^^•WfciWI
AF 6. 425 ft2
(R/E)u, .0144*
-------
Vehicle: 1977 Ford Mustang II (Continued)
C : Front Hood Drag Coefficient
• •• Location
1. front area below windshield A, 8.843 ft
2. front end area A_, 6.425 ft
3. hood length L. 4.416 ft
C_ : Rear Vertical Edge Drag Coefficient
Location
S
1. vertical portion R 0.50 in. E, S in. R 1.096 in.
of body vl bl v
2. sloping portion R 0.625 in. E, 5 in. E, 17 in.
of body V2 °2 b
3. upper portion of Ry 2 in. E^ 3 in, W 62.85 in.
bumper 3 3 ————
4. lower portion of RV 1.75 in. E, 4 in. H 36.90 in.
bumper 4 4 ""
C_ : Base Region Drag Coefficient
*5
i- Location
1. area of base region Afi 7.747 ft
2. area of hatch portion A,, 5.678 ft2
3. rear slope from horizontal 0 24° C_ /C-. 1.21
DH DB
C-, • Underbody Drag Coefficient
— Location
1. underbody length L 14.477 ft
2. underbody width W 4.550 ft A (= LXW) 65.87 ft2
C-21
-------
Vehicle: 1977 Ford Mustang n (Continued)
tuberanc
Location
C_ : Protuberance Drag Coefficient
u
2
1, mirror A 0.1017 ft
2. antenna A 0.0250 ft2 LA 0.1267
P2 pj
C_ : Bullet Mirror Drag Coefficient
- — Location
1. none A,, 0
C : Cooling Drag Coefficient
Dll
radiator height 16 in.
radiator width 19 in. A 2.111 ft2
C-22
-------
Vehicle: Manufacturer
Ford
•oje<
Make
Model
Model Year
License No/VTN
cted Fromal Area, ft
Pinto
3 -dr. Runabout
1977
152 TDB (Calif. )/8RllY105096
19.46
: Front End Drag Coefficient
^M«
1.
2.
1.
1.
2.
3.
Location
above grille RU
above headlights R
bottom of Ri
bumper ^1
at headlights R
vl
upper portion R
of bumper 2
lower portion R
of bumper V3
6 in. E_ 41. 5 in. (R/E) 0.0707
0.0625 in. E 18 in.
U2
0.625 in. E, 61 in. (R/E). 0.0102
LI /
0. 0625 in. E 9 in. (R/E) 0.0736
3 in. E 2 in.
2. 5 in. E 4 in.
A^ 6.741ft2
: Windshield Drag Coefficient
^^«M
1.
2.
3.
Location
roof- wind shield R ,
intersection
A-post R ,
windshield slope
4 in, E., 36. 87 in. (R/E), 0. 109 in.
0.375 in. E ., 12. 19 in, (R/E), 0.031 in.
60° A^ 4. 091 ft2 *exceeds max.
from vertical
use 0.105
C-23
-------
Vehicle: 1977 Ford Pinto (Continued)
CD : Front Hood Drag Coefficient
• Location
1. front area below windshield A, 9.690 ft
2. front end area Ap 6.741 ft
3. hood length L^ 3.819 ft
CD : Rear Vertical Edge Drag Coefficient
•• Location
1. body portion R 1. 188 in. E, 10 in. R 1. 693 in
vl bl v
2. upper portion of R 3.25 in. E, 2 in. E, 16. 5 in.
bumper V2 D2 b - "
3. lower portion R 2.125 in. E, 4. 5 in. W 60.73 in
of bumper V3 3 R 37. 05 in.
C,j : Base Region Drag Coefficient
^— — Location
1. area of base region Afi 6.629 ft
2. area of hatch portion A-* 6.615 ft
3. rear slope from horizontal 0 27
Cn : Underbody Drag Coefficient
\j
• Location
1. underbody length L 13.964 ft
2. underbody width W 4.473 ft A (= LXW) 62.46 ft2
P1
C-24
-------
Vehicle: 1977 Ford Pinto (Continued)
Cn • Protuberance Drag Coefficient
u
• 7. Location
1. mirror A^ 0.1037 ft2
2. antenna A 0.0250 ft £A 0.1287
P2 Pj
C_ J Bullet Mirror Drag Coefficient
10
— • Location
1. none A,. 0
Cn : Cooling Drag Coefficient
~~ radiator height 16.75 in.
radiator width 17.125 in. A 1.992 ft2
C-25
-------
Vehicle: Manufacturer Ford
Make Fairmont
Model 4-dr. Sedan
Model Year 1978
License No/VIN 031 UDH (Calif. )/8K92T132207
Projected Frontal Area, ft2 21.05 ft2
CD : Front End Drag Coefficient
— — — Location
1. above grille RU 2.25 in. EU 32.41 in. (R/E)u 0.0229
2. above headlights R 0.375 in. E 27.87 in.
1. bottom of R. 0. 50 in.
1.
2.
3.
!v
i.
2.
3.
bumper
at fender
upper portion
of bumper
lower portion
of bumper
Windshield Drag
Location
roof-windshield
intersection
A-post
windshield slope
L\
R
R
"2
R
1.125 in.
2. 75 in.
2.125 in.
V3'
Coefficient
R i
R .
y
3.5 in.
2.25 in.
54°
L\
E
E
V2
E
V3
Eu'
Ev'
AW-
8
in.
2. 5 in.
3
46.
17.
5.
in.
0 in.
11 in.
668 ft2
I B
(R/E^^O,
AF 7.608
-" ' ^
J955
ft2
(R/E)U, 0. 076j^
(R/E)V. 0.132*
*
exceeds max.
from vertical use 0. 105
C-26
-------
Vehicle: j^978 Ford Fairmont (Continued)
CD : Front Hood Drag Coefficient
. Location
1. front area below windshield A. 9.828 ft2
W\ ^••^^^^•^^^^^•^^^^•(••i
2. front end area A_, 7.608 ft
3. hood length 1^ 4.352 ft
C_ : Rear Vertical Edge Drag Coefficient
-• Location
1. vertical portion R 1.375 in. E, 4.203 in. R 1.
of base region vl Dl v
557 in.
2. sloping portion R 1.313 in. E, 10. 088 in. E, 20. 175 in.
of base region V2 D2 °
3. upper portion R 2. 75 in. E. 2. 942 in. W 63.47 in.
of bumper 3 3 — —~-— —
4. lower portion RV 2 in. E. 2. 942 in. H 40.53 in.
of bumper 4 4
TV * Base Region Drag Coefficient
5
— Location
1. area of base region A_ 9. 181 ft
2. area of hatch portion A__ 6.713 ft2
3. rear slope from horizontal 20° _ C_ /C_ 0. 925
DH DB
C-. : Underbody Drag Coefficient
jj
. . Location
1. underbody length L 15.492 ft
2. underbody width W 4. 558 ft A (= LXW) 70. 62 ft2
C-27
-------
Vehicle: 1978 Ford Fairmont (Continued)
C,-j : Protuberance Drag Coefficient
9
— Location
1. mirror A^ 0.1383 ft2
2. antenna A 0.0252 ft2 LA 0.1635 ft2
P2 PJ •
: Bullet Mirror Drag Coefficient
— Location
1. none A~, 0
Cn : Cooling Drag Coefficient
^11
radiator height 19 in.
radiator width 25 in. A 3.299 ft2
r
C-28
-------
Vehicle: Manufacturer Ford
Make Granada
Model 4-dr. Sedan
Model Year 1978
License No/VIN 492 TSP (Calif. )/8W82F108082
Projected Frontal Area, ft 22.18
C~ : Front End Drag Coefficient
D. *
— * • Location
1. fender and body R 1.75 in. E 11.75 in. (R/E) 0.0066
excluding head- ul ul u
lights &c grille areas
2. above headlights RU 0.1875 in. EU 20 in.
3. above grille R 0.0625 in. E 31.5 in.
3 3
1. bottom of R. 1.125 in. E/ 63.25 in. (R/E), 0.0178
bumper Ll *1 /
1. at fender Rv 0.125 in. E 11 in. (R/E) 0.0392
. vl (use 0) vl v
2. upper portion Ry 2.25 in. E 3 in.
of bumper 2 " V2 ~—"—~—~——-
, 3. lower portion Ry 1.5 in. E 3.5 in.
of bumper 3 3 8.529ft2
: Windshield Drag Coefficient
~ Location
1. roof-windshield R. 4.75 in. E . 47.93 in. (R/E) . 0.0991
intersection
2. A-post R. 1.25 in. EV< 14.26 itu (R/E)y. 0.0877
3. windshield slope y 56° A... 5.252 ft2
from vertical
C-29
-------
Vehicle: 1978 Ford Granada (Continued)
CD : Front Hood Drag Coefficient
" Location
o
1* front area below windshield A, 10.724 ft
2. front end area A^, 8.529 ft2
3. hood length L, 4.719 ft
C_ : Rear Vertical Edge Drag Coefficient
fL
• • • Location
1. sloping portion R 1 in. E 6 in. R it 543 ^
of body 1 Dl ' v —
2. vertical portion R 1.375 in.
v.
of body 2
3. upper portion R 2.75 in. E^ 4 in. W__66.85m.
of bumper 3 3
4. lower portion R 1.5 in. E, 3.5 in. H 41.0 in..
of bumper 4 4 "
n : Base Region Drag Coefficient
Location
• A *>r+ ^"%*» /_
B
1. area of base region A_ 10.151 ft
2. area of hatch portion A,. 6,706 ft
3. rear slope from horizontal 0 21°
C_ : Underbody Drag Coefficient
"' • Location
1. underbody length L 16.201 ft
2. underbody width
C-30
-------
Vehicle: 1978 Ford Granada (Continued)
C-. : Protuberance Drag Coefficient
DQ B
... 7 Location
1. antenna A 0.0530 ft2 lA 0.0530 ft2
Pl Pj
C : Bullet Mirror Drag Coefficient
- Location
1. one each side AM 0.2277 ft2
C_ : Cooling Drag Coefficient
'radiator height 16.5 in.
radiator width 24 in. A, 2.750 ft
C-31
-------
Vehicle: Manufacturer Ford
Make LTD II
Model 4-dr. Sedan
Model Year 1978
License No/VIN Dlr 6985 (Calif. )/8A30S175412
Frontal Area, ft 23.2
C_ : Front End Drag Coefficient
Projected Frontal Area, ft 23.23
'i
— Location
1. fender and body RU 1.25 in. EU 20 in. (R/E) 0. QQ82
exluding head- 11 u "
lights and grille
areas
2. above headlights R 0. 5625 in. EU 17 in.
2 2
3. above grille R 0.031 in. E 28. 9 in.
1.
1.
2.
3.
bottom of
bumper
at fender
upper portion
of bumper
lower portion
Rf
R
V
R
' V2'
R .
0.625 in. E.
LI
0. 0625 in. E
(use 0) 11
1. 813 in. E
2
2 in. E
68. 5 in.
12.5 in.
3 in.
3.5 in.
(R/E)
£~
(R/E)v _
0. 0091
0.0345
-•—•••«•• •
C : Windshield Drag Coefficient
Location
1. roof-windshield RU, 6 in. EU, 46.26 in. (R/E)u, 0.1297*
intersection ~~
2. A-post Rv,, 1.25 in. EV,
3. windshield slope y 59° _ AW 4. 901 ft exceeds max.
from vertical use 0. 105
C-32
-------
Vehicle: 1978 Ford LTD II (Continued)
CD ! Front Hood Drag Coefficient
- Location
1. front area below windshield A. 11.459 ft2
2. front end area Ap 9.309 ft2
3. hood length L^ 5.563 ft
C~ : Rear Vertical Edge Drag Coefficient
4
— Location
1. at fender R 0.0625 in. E. 14.85 in. R 0.856 in.
vl bl v
2. upper portion R 3.25 in. E, 3.25 in. E, 21.60 in.
of bumper V2 b2 °
3. lower portion R 2 in. E. 3.5 in. W 66.01 in.
of bumper 3 3 •~~~~~—~~— —————
H 40.25 in.
C_ : Base Region Drag Coefficient
- Location
1. area of base region Ap 10.273 ft2
2. area of hatch portion A-, 6.069 ft2
3. rear slope from horizontal # 18° Cn /C_ 0,80
DH DB
C— : Underbody Praia; Coefficient
6
— Location
1. underbody length L 16.971 ft
2. underbody width W 5.042 ft A (= LXW) 85.56 ft2
C-33
-------
Vehicle: 1978 Ford LTD n (Continued)
C-. : Protuberance Drag Coefficient
9
1. antenna A 0.0252 ft2
2. hood ornament A 0.0247 ft2 £A 0. 0499 ft2
P2 Pj ~~
D : Bullet Mirror Drag Coefficient
= — Location
1. one each side Aj^ 0. 2303 ft2
T, : Cooling Drajg Coefficient
Dll
radiator height 18 in«
radiator width 28 in. Ar 3. 50 ft
C-34
-------
Vehicle: Manufacturer General Motors
Make Chevrolet Impala
Model 4-dr. Sedan
Model Year 1977
License No/VIN 807 SMV (Calif. )/lL69U7C147622
Projected Frontal Area, ft 24.14
C~ ' Front End Drag Coefficient
D, — B
*- Location
1. hood-front R 1. 625 in. E 65.45 in, (R/E) 0.0248
breakline Ul Ulu
1. center segment R. 1.25 in. E. 37.06 in. (R/E). 0.0137
of bumper Ll *1 *
2. outer segment R. 0.563 in. E* 31.35 in.
of bumper *2 *2
1. at fender R 0.125 in. E 10.74 in. (R/E) 0.0580
Vj yi v
2. upper section R 3 in. E 4 in.
of bumper 2 2
3. center section RV 1.375 in. Ey 1.75 in.
of bumper 3 3
4. lower section RV 2 in. EV 1.25»in.
of bumper 4 4 Ap 9.657ft2
r : Windshield Drag Coefficient
D, —
., r- Location
1. roof-windshield RU, 2.5 in. EU, 50.43 in. (R/E)u, 0.0496
intersection
2. A-post RT. 1.5 in. EV> 15.28 in. (R/E)^. 0.0982
3. windshield slope y 53° AW 5.517 ft2
from vertical
C-35
-------
Vehicle: 1977 Chevrolet Impala (Continued)
C_ : Front Hood Drag Coefficient
u --.._.-.
• " Location
1. front area below windshield A. 12.708 ft2
n i "
2. front end area AF 9.657 ft2
3. hood length L 5.118 ft
CD : Rear Vertical Edge Drag Coefficient
1111 Location
1. fender portion R 0.125 in. E. 10.55 in. R 0.854 in.
1 1 v~~ ~~~
2. upper portion R^ 2.875 in. Efe 3.25 in. E 17.05 in.
of bumper V2 2 ~
3. center portion RV 1.375 in. Eb 1.75 in. W 67.08 in.
of bumper 3 3
4. lower portion RV 1 in. Efe 1.5 in. H 43.10 in.
of bumper 4 4
C_ : Base Region Drag Coefficient
——— Location
1. area of base region A^ 9.157 ft
2. area of hatch portion AJJ 8,629 ft
3. rear slope from horizontal 20 CD /CD 0.925
CD : Underbody Drag Coefficient
11 Location
1. underbody length L 17.625 ft
2. underbody width W 4.879ft Ap(= LXW) 86.00 ft2
C-36
-------
Vehicle: 1977 Chevrolet Impala (Continued)
C : Protuberance Drag Coefficient
Dp
'- Location
1. mirror A^ 0.1591 ft DA 0.1591ft2
C • Bullet Mirror Drag Coefficient
D10 °
"*"• Location
1. none
Cooling Drag Coefficient
" radiator height 18 in.
radiator width 27. 5 in. A 3.438 ft2
C-37
-------
Vehicle: Manufacturer
Make
Model
Model Year
General Motors
Chevrolet Nova
4-dr, Sedan
1977
License No/VIN 125 SZS (Calif. )/lX69D7L146791
Projected Frontal Area, ft 22.56
CTN • Front End Drag^Coefficient
— Location
1. above headlights R
2. above grille
1 in.
Ll "1
1. 375 in. E
En 20• 5 fa«
-------
Vehicle: 1977 Chevrolet Nova (Continued)
CD : Front Hood Drag Coefficient
— • Location
1. front area below windshield A. 11.225 ft2
2. front end area Ap 8.393 ft2
3. hood length L^ 4.674
CD : Rear Vertical Edge Drag Coefficient
—. Location
1. body above RV 0.375 in. E. 11.326 in. R 1.195 in.
bumper 1 1 "~ v
2. upper portion R 3.5 in. E. 3.5 in. E 18.826 in.
of bumper 2 2 b "
3. lower portion RV 1.5 in. E. 4 in. W 62.291 in.
of bumper 3 3 TT ,. f., .
H 40. 556 in.
CD : Base Region Drag Coefficient
-. Location
1. area of base region A,, 8.001 ft2
J3 ——i>-_____
2. area of hatch portion A,, 7.734ft2
3. rear slope from horizontal
-------
Vehicle: 1977 Chevrolet Nova (Continued)
C_ : Protuberance Drag Coefficient
— Location
1. mirror A 0.1169 ft2 LA 0.1169 ft2
Pj PJ—
CD : Bullet Mirror Drag Coefficient
• Location
1. none Aj^
CD : Cooling Drag Coefficient
——~" radiator height 16 in.
radiator width 26 in. Ar 2.889 ft2
C-40
-------
Vehicle: Manufacturer General Motors
Make Oldamobile Cutlass Supreme
Model 2-dr. Coupe
Model Year 1977
License No/VIN 866 SMA (Calif. )/3J57R7R209999
Projected Frontal Area, ft2 22.62
Cn : Front End Drag Coefficient
-. '- Location
1. center portion R 1.125 in. E 10.75 in. (R/E) 0.0116
. . . .
ul ul u
2. above headlights R 1.188 in. E 32 in.
. .
U2 U2
3. sheet metal R 0. 0625 in. E 24 in.
behind grille U3 U3
1. center portion of R . 2.25 in. E 35 in. (R/E) 0. 0296
*1 *1 L
bottom of bumper
2. outer segments R. 1.625 in. E. 31 in.
of bottom of iz l^ ~~
bumper
1. at fender R 0.125 in. E 9 in. _ (R/E) 0.0740
YI Vi - v -
2. upper portion R 3.25 in. E 3.75 in.
of bumper 2 2
3. lower portion Ry 2 in. _ E 5 in.
of bumper 3 V3
Ar 8. 406 ft*
CD : Windshield Drag Coefficient
— • Location
1. roof-windshield R.. 4. 75 in. E 45. 8 in. (R/E) . 0.1037
intersection u u u -
2. A-post R^, 0.75 in. EV, 14. 1 in. (R/E)v, 0.0532
3. windshield slope V 56° _ A.,, 4. 522 ft2
from vertical —————.
C-41
-------
Vehicle: 1977 Oldsmobile Cutlaas Supreme (Continued)
C_ : Front Hood Drag Coefficient
——•— Location
1. front area below windshield A 12.279 ft
2. front end area Ap 8.406 ft2
3. hood length L^ 5.371 ft
CD : Rear Vertical Edge Drag Coefficient
1 Location
1. body portion Ry 0.25 in. Eb 9.5 in. R.. 0.745 in.
2, upper portion R 1.563 Jn^ E^ 4.5 in. Efe 18 in,
of bumper 2 2 ~
3. lower portion RV 1 in. E^ 4 in. W 65.46 in.
of bumper 3 3
H 39. 93 in.
C : Base Region Drag Coefficient
• - ' Location
1. area of base region A£ 9.021 ft
2. area of hatch portion AJJ 6. 991 ft2
3. rear slope from horizontal 20° CD /CD .0.925^
rr B
CD : Underbody Drag Coefficient
1 Location
1. underbody length L 15.800 ft
2. underbody width W 4.970 ft Ap(= LXW) 78.53 ft2^
C-42
-------
Vehicle: 1977 Oldsmobile Cutlass Supreme (Continued)
CD : Protuberance Drag Coefficient
—i •• Location
1. mirror A 0.1491 ft2
2. hood ornament A^ 0.0275 ft2 £A o. 1766 ft2
p2 p.
C_ : Bullet Mirror Drag Coefficient
10
Location
1. none
: Cooling Drag Coefficient
"""""" radiator height 15. 5 in.
radiator width 28 in. Ar 3.014 ft2
C-43
-------
Vehicle: Manufacturer General Motors
Make Chevrolet Impala
Model 4-dr, Sedan
Model Year 1978 _
License No/VIN 759 ULU (Calif. )/lL69U8S193433
Projected Frontal Area, ft 23.89
CD : Front End Drag Coefficient
• Location
1. above headlights RU 1.5 in. EU 28. 52 in. (R/E)u 0. 0244
2. above grille R 1.625 in. E 35.93 in.
U2 2
1. center segment R. 1. 5 in. R, 37.28 in. (R/E) 0.0154
of bumper *\ ^ 1 / """""
2. outer segment R. 0. 563 in. R. 31.89 in.
of bumper *2 ^2
1. at headlights RV 0. 125 in. EV 10 in. (R/E)y 0.0676
2. upper portion RV 3.25 in. EV 4 in.
of bumper 2 2
3. center portion R 1.5 in. E 1.75 in.
» i V- ™~ •""" v^
of bumper 3 -5
4. lower portion RV 2.125 in. EV 1«25 in.
of bumper 44
A 9. 843 ft2
CD : Windshield Drag Coefficient
— — Location
1. roof-windshield RU, 2.625 in. EU, 50. 51 in. (R/E)u, 0. 0520
intersection
2. A-post RV, 1.375 in. EV, 15.15 in. (R/E)v, 0. 0907^
3. windshield slope X 53° AW 5. 482 ft2
from vertical
C-44
-------
Vehicle: 1978 Chevrolet Impala (Continued)
C *
3
MVM^^"
1.
2.
3.
!^!
i.
2.
3.
4.
5
1.
2.
e.
CD ''
6
1.
2.
Front Hood Drag Coefficient
Location
front area below windshield
front end area
hood length
A,. 12.659ft2
AF
Lu
9. 843 ft2
5. 067 ft
Rear Vertical Edge Draa Coefficient
Location
at fender R 0. 125 in.
1
upper portion R 3.25 in.
of bumper 2
center portion R 1.75 in.
of bumper V3
lower portion R 1.25 in.
of bumper V4
Base Region Drag Coefficient
Location
area of base region
area of hatch portion
rear slope from horizontal
Underbody Drag Coefficient
Location
underbody length L 17.
underbody width W 5.
°l~
^
°2
Efc
b3
^
D4
AD
*!!
0
63 ft
03 ft
10. 34 in. R 0. 997 in.
3. 25 in. E^ 16. 84 in.
1.75 in. W 67. 28 in.
1.5 in. H 43. 84 in.
9.110 ft2
8.710 ft2
20° C_ /C^ 0. 925
DH DB
A _(= LXW) 88.77 ft2
C-45
-------
Vehicle: 1978 Chevrolet Impala (Continued)
C_ : Protuberance Drag Coefficient
M -
Location
1. mirror A 0.1295 ft2 XA^ 0.1295ft2
: Bullet Mirror Drag Coefficient
10
—=— Location
1. none
: Cooling Drag Coefficient
radiator height 18 in.
radiator width 27.5 in. Ay 3.438 ft2
C-46
-------
Vehicle: Manufacturer General Motors
Make Chevrolet Monza
Model 2-dr. Faatback
Model Year 1978
License No/VIN none (He s 3 ell Chev-rolet>/lR07A8U102658
Projected Frontal Area, ft 19.04
V
1.
2.
1.
1.
Front End Drag
Location
above headlights
between head-
lights
body below
bumper
at headlights
Coefficient
Ru
Ul
Ru
U2
R
1
R
o.
0.
0.
0.
0625
0625
0625
0625
in.
in.
in.
in.
E
ul
E
U2~
E
1
E
30
26
53
8
in.
in.
in. .
.5 in.
(R/E)U .
u •
(R/E) m
- (R/E)V .
0.0011
0. 0012
0. 0294
l (use 0)
•2. bumper R 2 in. E 3 in.
v2 V2
3. body below R 0.0625 in. EV 3 in.
C_ : Windshield Drag Coefficient
j2 -
— Location
1. roof-windshield R . 6 in. E^. 42. 98 in. (R/E)u. 0.1396*
intersection
2. A-post RT. 2.5 in. E^. 12.69 in. (R/E>v. 0.197*
9 dc
3. windshield slope y 61° _ A.., 4.263 ft exceeds max.
from vertical u«* 0. 105
C-47
-------
Vehicle: 1978 Chevrolet Monza (Continued)
C_ : Front Hood Drag Coefficient
—— Location
1. front area below windshield A^ 9.026 ft2
2. front end area Ap 5.268 ft
3. hood length 1^ 4.400 ft
C_ : Rear Vertical Edge Drag Coefficient
4
MMMBB
1.
2.
3.
V
Location
tan light R
bottom of tail R
light to bottom
of bumper
below bumper R
Base Region Drag
Location
^1
12
2. 25 in. E
2. 75 in. E,
5 in. E,
V3~
Coefficient
3.5 in. R^ 3.348 in.
6 in. E, 14 in.
~ D "
4.5 in. W 53.47 in.
H 39.18 in.
1. area of base region A_ 5,535 ft
2. area of hatch portion A-, 5.089 ft2
°
3. rear slope from horizontal 0 21
D : Underbody Drag Coefficient
—- Location
1. underbody length L 14.056 ft
2. underbody width W 4.477 ft Ap(= LXW) 62.92
C-48
-------
Vehicle: 1978 Chevrolet Monza (Continued)
Co ; Protuberance Drag Coefficient
". Location
1. none
A
pl
_ : Bullet Mirror Drag Coefficient
i2- Location
1. one each side Aj^ 0.2313 ft
_ : Cooling Drag Coefficient
Dll
radiator height 15 in,
radiator width 20 in. Ay 2. 083 ft2
C-49
-------
Vehicle: Manufacturer General Motors
Make
Model
Model Year
Chevrolet Nova
4-dr. Sedan
1978
License No/VIN None {Hessell Chevrolet)/lY69U8102645
Projected Frontal Area, ft2 22. 77
v
1.
1.
1.
2.
3.
4.
C_ :
MBMMMM
1.
2.
3.
: Front End Drag
Location
hood-front
breakline
bottom of
bumper
at headlights
above head-
lights
upper portion
of bumper
lower portion
of bumper
Windshield Drag
Location
roof-windshield
intersection
A-post
windshield slope
Coefficient
R 2. 125 in. E.. 62. 44 in.
1 1
R, 1.25 in. E, 64.27 in.
R . 031 in. E 7. 5 in.
vl (use 0) ^1
R^ 0.0625 in. E 1.25 in.
^2 2
R 4. 75 in. E 4 in.
V3 ^3
RV 2. 25 in. Ev 3. Sin.
Coefficient
R.., 3. 5 in. E.., 45. 65 in.
KV, 3 in. E^ 15,82 in.
X 54° A.,, 5.015ft2
. (R/E).. 0.0340
(R/E). 0.0194
. (R/E).. 0.1021
Aw 7. 967 ft2
(R/E) , 0.0767
(R/E)r, 0.1896*
exceeds max.
noo n i nc
C-50
-------
Vehicle: 1978 Chevrolet Nova (Continued)
C_ : Front Hood Drag Coefficient
3
-i .. Location
1. front area below windshield A, 10.846 ft
2, front end area AF 7.967 ft
3. hood length 1 4.721 ft
C : Rear Vertical Edge Drag Coefficient
4
- • Location
1. body above Ry 0.938 in. E, 10.338 in. R 1.537 in.
bumper 1 1 v
2. upper portion R 3.25 in. E, 4 in. E, 18.338 in.
of bumper V2 °2 b
3. lower portion R 1.375 in. E, 4 in. W 62.428 in.
of bumper 3 3
H 41.292 in.
C_ : Base Region Drag Coefficient
— Location
1. area of base region A- 7.842 ft2
2. area of hatch portion Ay 8. 039 ft2
3. rear slope from horizontal 0 21° C_ /C_ 1.0
DH DB
CD : Underbody Drag Coefficient
• Location
1. underbody length L 15.160 ft
2. underbody width W 4.957 ft A ( =LXW) 75.15 ft2
C-51
-------
Vehicle: 1978 Chevrolet Nova (Continued)
C-. : Protuberance Drag Coefficient
9
1 ' Location
1. mirror A 0.1468 ft2 £A 0.1468 ft2
C_ : Bullet Mirror Drag Coefficient
— Location
1. none A.. 0
Cn : Cooling Drag Coefficient
^11
radiator height 16 in.
radiator width 26 in. A 2.889 ft2
C-52
-------
Vehicle: Manufacturer
General Motors
Make
Model
Model Year
License No/VIN
•ejected Frontal Area, ft
Olds mobile Cutlass
2 -dr. Coupe
1978
Supreme
448 TRW (Calif.)/3R47F8R407693
21.58
D : Front End Drag_ Coefficient
— Location
1. hood-front R
breakline ul
1. center segment R.
of bumper *1
2. outer segment R-
of bumper *2
1. at fender R
2. upper portion R
of bumper V2
3. lower portion R
of bumper V3
: Windshield Drag Coei
— Location
1. roof-windshield R ,
intersection u
2. A-post RV,
3. windshield slope y
0. 0625 in. E
Ul
0. 813 in. E.
1.75 in. Em
0.625 in. E
2. 375 in. E
"2
1.563 in. E
"3
Eficient
3.75 in. E ,
1.938 in. E .
59° A.
'iV
63. 20 in. (R/E) 0.0010
15 in. (R/E), 0. 0242
48 in.
8 in. (R/E) 0.0814
3.5 in.
4 in.
A^ 7.692ft2
46. Sin. (R/E)., 0.0806
14.8 in. (R/E) , 0.1309*
2 $
4.881 ft exceeds max..
use 0.105
C-53
-------
Vehicle: 1978 Oldsmobile Cutlass Supreme (Continued)
CD : Front Hood Drag Coefficient
• Location
1. front area below windshield A 11,286ft
2. front end area Ap 7,692 ft
3. hood length 1^ 4.663 ft
C_ : Rear Vertical Edge Drag Coefficient
4
M^MMMMH
1.
2.
3.
!v
i.
2.
3.
Location
body portion R 0.0625 in.
vl
upper portion R 3 in.
of bumper V2
lower portion R 1.875 in.
of bumper V3
Base Region Drag Coefficient
Location
area of base region
area of hatch portion
rear slope from horizontal
Eb
Eb
Eb
b3
"R —
AJJ
9. 25 in. RT
3. 5 in. Eb
3. 5 in. W
H
8.660 ft2
7. 254 ft2
23° 1C.
1. 086 in.
16.25 in.
62.60 in.
41. 52 in.
/Cn 1.14
: Underbody Drag Coefficient
—£- Location
1. underbody length L 15.233 ft
2. underbody width W 4.716 ft A ( = LXW) 71.84 ft2
C-54
-------
Vehicle: 1978 Old3mobile Cutlass Supreme (Continued)
C : Protuberance Drag Coefficient
9
... -• Location
1. mirrors (one each side) A 0.2575 ft
2. hood ornament A 0.0091 ft2 LA 0.2666 ft2
P2 Pj
C_ : Bullet Mirror Drag Coefficient
10
. — Location
1. none
: Cooling Drag Coefficient
radiator height 16 in.
radiator width 28 in. A 3.111 ft2
C-55
-------
Vehicle: Manufacturer Porsche
Make Porsche
Model
Model Year
924
1978
License No/VIN Distr. 11976 (Calif.)
Projected Frontal Area, .ft 18. 88
C_ : Front End Drag Coefficient
— Location
1. top edge of
bumper
1. bottom edge of
front dam
1. at bumper
R 0.438 in. EU
R 7.0 in.
54. 9 in.
(R/E)u 0.0080
0.063 in. E. 57,8 in.
ll
(R/E)., 0.0011
4. 75 in.
(R/E).. 1. 474
^ «•
*
exceeds max, use
0.105
Ar 4.633 ft2
J-i.
1.
2.
3.
!v
i.
2.
3.
Location
r oof -wind shie Id
intersection
A-post
windshield slope
from vertical
Front Hood Drag
Location
R , 12 in.
R , 4. 5 in.
y 60°
Coefficient
area of front below windshield
front end area
hood length
E , 44. 0 in.
E , 12. 9 in.
A 4. 1^2 ft
*Vt«r *• A-*** »**
A^ 10. 548 ft2
A^ 4.633 ft2
L, 4. 858 ft
(R/E).., 0.273'
u
(R/E)v, 0.349'
exceeds max.
use 0.105
C-56
-------
Vehicle: 1978 Porsche 924 (Continued)
C, : Rear Vertical Edge Drag Coefficient
^ Location
1. above tail lights RV 6 in. Efe 5.12 in. RV 5.275 in.
2. below tail lights R,, 5.5 in. E, 5.12 in. E, 15 in.
V2 D2 b
3. bumper R, 4.25 in. E, 4.75 in. W 54.885 in.
V- - Q- - ~"
H 36.6 in.
C * Base Region Drag Coefficient
__ - Location
I. area of base region A_ 7.198 ft2
2. area of hatch portion A__ 2,627ft2
3. rear slope from horizontal 0 17.5° C /C 0,76
DH DB
C— : Underbody Dray Coefficient
^J / ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*i^m^^*m*^^m*^f***^^
__ - Location
1. underbody length L 12.287 ft
2. underbody width W 4.740 ft A (= LXW) 58.24 ft2
C_. : protuberance Drag Coefficient
^.—i Location
1. mirror A 0.1455 ft2
2. antenna A_ 0.0436 ft2 £A_ 0.1891 ft2
~__ »w ^ »^ ^ ^» ^^ * -in.
v : Bullet Mirror Drag Coefficient
10
Location
1. none A,. 0
: Cooling Drag Coefficient
' radiator height 10.75 in.
radiator width 20.375 in. AT 1.5Z1 ft2
C-57
-------
Vehicle: Manufacturer Volkswagen
Make Rabbit (Diesel)
Model 2-dr. Hatchback
Model Year 1977
License No/VIN Distr. 11976 (Calif. )/1773260730
Projected Frontal Area, ft 19.77
C-. : Front End Drag Coefficient
— Location
1. hood-front
breakline
U
0.375 in. E 52.1 in. (R/E) 0.0072
U
1. bottom of front R. 0.031 in. E 44.3 in. (R/E). 0.0007
underbody *1 'l *
1. at fender
RV 1.75 in. E
13 in.
). 1346'
exceeds max.
use 0.105
A 7.188 ft2
D : Windshield Drag Coefficient
Location
1. roof-windshield R , 5 in.
intersection
2. A-post
3. windshield slope y
from vertical
51'
C_ : Front Hood Drag Coefficient
Location
2. front end area
3. hood length
E , 42. 2 in.
u1 ••
R i 2.25 in. E , 15.6 in.
5. 415 ft4
1. area of front below windshield A, 10.325 ft
A_ 7.188ft*
£ —————
3,093ft
(R/E).., 0.1185'
u
(R/E)v, 0.1449
'exceeds max.
use 0.105
C-58
-------
Vehicle: 1977 VW Rabbit(Diesel) (Continued)
,r Vertica
Location
C_ : Rear Vertical Edge Drag Coefficient
1. tail light and R 0.25 in. E_ 10.25 in. R 1.462 in.
body above tail vl bi v
light
2. body below tail R 2.625 in. E. 3 in. Et 18.25 in.
light V2 *>2 b
3. bottom portion R 3.25 in. E. 5 in. W 50.07 in.
of body V3 b3 __ ., ._ .
H 46. 35 in.
CD : Base Region Drag Coefficient
— Location
1. area of base region A 8.094 ft2
2. area of hatch portion A., 5.331 ft2
3. rear slope from horizontal 0 42° Cn /Cn 1.0
Cn : Underbody Drag Coefficient
—— Location
1. underbody length L 10. 867 ft
2. underbody width W 4. 487 ft. A (= LXW) 48.76 ft2
C-. : Protuberance Drag Coefficient^
9
. Location
1. mirror A 0.1226 ft2
2. antenna A 0. 0474 ft2 I A 0.1700 ft2
C-, ' Bullet Mirror Drag Coefficient
jj -•
- Location
1. none A.,
C-. : Cooling Drag Coefficient
Dll
radiator height 12 in.
radiator width 18.75 in. Ar 1.562 ft2
C-59
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-460/3-78-010
4. TITLE AND SUBTITLE
Assessment of an Empiric
Vehicle Aerodynamic Drag
meters
2.
al Technique for Estimating
from Vahicle Shape Para-
7. AUTHOR(S)
W. M. Smalley, W. B. L«e
9. PERFORMING ORGANIZATION NAME AND ADDRESS
The Aerospace Corporation
El Segundo, California 90245
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency-
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
3. RECIPIENT'S ACCESSION NO.
S. REPORT DATE
July 1978
6. PERFORMING. ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
AT3.-73(7623-03)-l
1O. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-03-2482
13. TYPE OF REPORT ANO PERIOD COVERED
Final Task Report
14. SPONSORING AGENCY CODE
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
This report presents the results of a determination of aerodynamic drag
coefficient, Cp, based on an empirical prediction technique developed by The
Aerospace Corporation Ln a previous EPA-sponsored study. This method utilizes
an aircraft type "drag build-up" approach wherein the total drag is calculated as the
sum of CQ contributions from components of the vehicle. Component contributions
are determined from various body/chassis shape parameters. The present study
was directed toward the acquisition and application of vehicle measurements data
as required to evaluate aerodynamic road load by this prediction method for com-
parison with measured values.
Twenty 1977/1978 model year passenger cars were examined for which
aerodynamic drag coefficients were derived. Comparison of these results with
wind tunnel test data on twelve of the vehicles showed good agreement on an average
basis; the maximum disparity in an individual result was 18 percent.
17.
a. DESCRIPTORS
KEY WORDS AND DOCUMENT ANALYSIS
b. IDENTIFIERS/OPEN ENDED TERMS
Aerodynamic Drag
Motor Vehicles
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report/
Unclassified
20. SECURITY CLASS (This page>
Unclassified
c. COSATi Field/Croup
13F
21. NO. OF PAGES
106
22. PRICE
EPA Form 2220-1 (9-73)
-------
INSTRUCTIONS
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17. KEY WORDS AND DOCUMENT ANALYSIS
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