FUEL ECONOMY
AND
EMISSION CONTROL
UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR AND WATER PROGRAMS
MOBILE SOURCE POLLUTION CONTROL PROGRAM
November 1972
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FUEL ECONOMY
AND
EMISSION CONTROL
UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR AND WATER PROGRAMS
MOBILE SOURCE POLLUTION CONTROL PROGRAM
November 1972
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OUTLINE
I. INTRODUCTION
II. DEFINITION
III. FACTORS AFFECTING FUEL ECONOMY
IV. EMISSION CONTROL EFFECTS ON FUEL ECONOMY
V. IMPACT OF OTHER AUTOMOTIVE DESIGN FEATURES ON FUEL ECONOMY
VI. FUTURE TRENDS IN FUEL ECONOMY
VII. SUMMARY
VIII.CONCLUSIONS
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I. INTRODUCTION
This paper analyzes the effect on fuel economy of emission controls
on automobiles. The analysis examines the various vehicle design factors,
including emission control devices, which affect motor vehicle fuel economy
and discusses the impact of the individual variables. Fuel penalties which
may be associated with emission control systems are placed into the perspective
of other fuel penalties which are currently, or may in the future, be experienced
by the motoring public.
No attempt is made here to deal with the question of national petroleum
consumption. However, this analysis provides a part of the necessary input
for such a study.
I/
II. DEFINITION OF "FUEL ECONOMY"
There are many ways to report the fuel economy of automobiles. Miles
per gallon (MPG) is the most commonly used and will be used in this analysis.
All figures reported in this analysis are in terms of miles per gallon
over the Federal Driving Cycle (see Section III. C.) While the single
parameter, miles per gallon, is easily understood and a good measure of
fuel economy, it must be qualified. Many factors influence fuel economy,
and a knowledge of these factors is needed if valid comparisons of fuel
economy figures are to be made.
III. FACTORS AFFECTING FUEL ECONOMY
The fuel economy of in-use light duty vehicles can range between 50
and 5 mpg. The major factors that influence fuel economy and account for
this wide spread are discussed below.
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A. The Design of the Automobile
The most important parameters associated with automobile design include
vehicle weight, rolling resistance (including tire, driveline and aerodynamic
drag) and axle ratio. Higher weight usually means poorer fuel economy because
more work is required to move the vehicle. Higher rolling resistance usually
means poorer fuel economy because more work is done deforming the tires and
pushing the vehicle through the air. A higher (numerically) axle ratio usually
means poorer fuel economy because the engine revolutions per mile are greater.
For modern vehicle design, however, weight is the single most important parameter.
B. The Manner In Which The Vehicle Is Driven
This factor is both important and difficult, if not impossible, to quantify.
In general, given identical vehicles, the driver who drives "harder" will get
poorer fuel economy than the driver who drives less hard. Examples of "hard"
driving are accelerating at or near the maximum capability of the vehicle, high
cruise speeds, not driving smoothly, and racing the engine at idle. The magnitude
of the effect due to the driver can be great, but there is no data on which to
quantify this factor.
C. The Type Of Route Traveled
The best fuel economy achievable with automobiles is at constant speed
cruise between 20 and 50 miles per hour in high gear. The exact optimum speed
depends on the vehicle and engine type. However, no realistic driving is done
at such a constant speed. Driving in heavy intracity traffic with many stops
per mile, long idling periods, and low average speeds generally results in the
poorest fuel economy. Driving on the highway at a constant speed usually results
in better fuel economy. For this reason, many references to vehicle fuel economy
also refer to the type of route traveled. Usually the distinction is made
between city or "around town" type of route; and "highway" type routes.
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All fuel economy figures reported in this analysis were measured
using the Federal Driving Cycle - an urban driving route. This was
done in part because it is the only cycle on which there is consistent
data. However, the cycle is useful for this analysis because it is
representative of a significant portion of vehicle operation, in particular
the driving done in urban areas.
D. The Engine
The design of the engine, its calibration, state of tune and overall
mechanical condition affect fuel economy. Important design factors include
compression ratio, intake and exhaust system configuration, internal
friction and carburetor design. The calibration of the engine, its spark
advance curve, the flow curve for the carburetor and the operation of
the choke can all affect fuel economy. The state of tune of the engine
as well as the condition of the parts that are usually involved in a tune up
are important. Finally, the mechanical condition of the engine, especially
valves and piston rings, can also hurt fuel economy if it is poor.
Emission controls have affected both the design and calibration of
engines. The design of the combustion chamber, the compression ratio,
the spark advance curve and the carburetor calibrations have all been changed.
In addition, other devices like air pumps and exhaust gas recirculation
have been added as emission control devices. All of these changes can have
an effect on engine efficiency and, in turn, fuel economy.
E. Power and Convenience Accessories
Many power and convenience accessories are used on modern automobiles,
including air conditioning, automatic transmissions, power steering, power
brakes, power seats and heated windows. Although all of the devices use
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energy which eventually results in fuel usage, the effect on fuel economy
of all but two are negligible. The two important ones are air conditioning
and automatic transmissions.
The use of air conditioning lowers fuel economy. The extent to which
it degrades fuel economy depends on how often the device is used, and how
much cooling load is required of it.
An automatic transmission is not as efficient as a manual transmission.
However, whether a vehicle equipped with an automatic transmission shows
better or worse fuel economy than a comparable manual transmission vehicle
depends on the way in which each vehicle is driven. All other things being
equal, the manual transmission equipped vehicle will generally show better
fuel economy.
F. Ambient Conditions
The ambient temperature, humidity, pressure (altitude), and wind speed and
direction all affect fuel economy. However, except in the case of large variations
from standard conditions (e.g. cruising into a strong headwind or operating at
a very high altitude,) the fuel economy effects of ambient conditions are minor.
IV. EMISSION CONTROL EFFECTS ON FUEL ECONOMY
There are, theoretically, two different ways to assess the effects
of emission control devices on fuel economy. One way is to determine
the effect of any one modification (e.g. retarded spark) on fuel economy.
This could be expressed as a percentage loss or gain, and the total effect
on a vehicle employing many modifications might be derived from adding up
all the individual device effects. This approach is not correct because
the effects are not, in general, additive. When one control approach or
device is used in combination with other devices as part of a total system,
there are various synergistic effects which can either lessen or worsen
the impact on fuel economy of any one device.
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The other approach, which is employed in this analysis, is to use actual
vehicle test data and from this data determine the effect of the complete
emission control system on fuel economy. While this approach does not provide
data on the effect of individual emission control components, it does yield
valid data on the complete system's performance, which is the ultimate concern
to the automobile user.
The choice of the test technique and of the type of data used in
making this kind of analysis are important. To validly compare fuel economy
figures so as to determine the effect of some change in vehicle design or
construction (emission controls in this case) the test must hold constant
all (or as many as possible) of the factors that influence fuel economy other
than the factor under study.
A. Use of the Federal Test Procedure
As indicated in Section III. C, the test used in this analysis to
derive the fuel economy figures is the Federal Emission Test Procedure,
involving an urban driving route run on a chassis dynamometer under controlled
.temperature conditions. The advantages and disadvantages of using this procedure
are summarized below.
1. Advantages
a. Ambient conditions are closely controlled, thus eliminating
variability associated with this factor.
b. Exactly the same route is used every time. The vehicle must
be driven over the same speed-time trace each time for the
emission test to be valid. This eliminates variability in
two factors: the route, and the driver.
c. The weight of the vehicle is known. Since the test procedure
involves testing vehicles at a discrete inertia weight, the
weight is known for every'test and can be isolated as a factor.
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2. Disadvantages
a. Since the driving cycle is an urban one, it is not possible
to compute a "highway" fuel economy figure.
b. The rolling resistance of the dynamometer used in the test
differs slightly from actual on-the-road rolling resistance.
These drawbacks do not, however, prevent valid comparisons regarding
urban fuel economy or the overall fuel economy potential of various engine
systems or engine/vehicle modifications. In addition, the measurement of
CO and CC^ and miles traveled during the test provides an accurate and
repeatable method —' of calculating fuel economy.
B. Data Sources
The data used as input for this study came from three major sources:
EPA surveillance data, EPA certification data, and EPA inhouse data from
various test and evaluation programs.
Use of the surveillance data of older cars can be challenged due to
the fact that the older in-use vehicles may not be directly comparable to
the 1973 certification prototypes, or to the advanced catalyst equipped
prototypes, due to the possible effects of maintenance and mileage on fuel
economy. It is, however, the only consistent data which exist for the earlier
model years and until such time as data on the effects of accumulated mileage
on MPG indicate otherwise, the aggregaton of all the data from the three sources
is considered to be a valid assumption.
C. Use of "C" Factor and Display of Data
When the data are plotted as fuel economy (in MPG) versus inertia weight
(IW) most of the data lies near the line represented by the equation
MPG x IW = C, where "C" is a constant value for any given model year. In
order to facilitate using a one parameter curve for each model year the
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value "C" was calculated in such a way to minimize the squared error. In
this way the effect of inertia weight can be eliminated and the value "C"
becomes an indicator of the average fuel economy for that model year. The
percent loss or gain in average fuel economy for each model year (all vehicle
weights) can then be determined by comparing the "C" values.
The average MPG figures for the various model years/inertia weights are
shown in Table I. Appendix I contains tables which give the detailed data
on average MPG and the range of MPG for the different inertia weights in model
years 1957-1973. Figure 1 is a plot of the curves for pre-68 cars and 1973
cars as well as 75/76 prototypes and alternative engines.
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TABLE I
MPG vs INERTIA WEIGHT AND MODEL YEAR*
Model INERTIA WEIGHT # of vehicles
Year iri sartpTe
1750 2000 2250 2500 2750 3000 3500 4000 4500 5000 5500
57 N.D. 26.5 N.D. N.D. N.D. N.D. 14.8 13.9 N.D. N.D. 12.9 24
58 N.D. 26.2 19.5 N.D. 13.4 N.D. 14.2 14.4 12.8 10.1 N.D. 23
59 N.D. 29.4 N.D. N.D. N.D. 15.7 15.2 14.1 13.4 13.9 N.D. 25
60 N.D. 20.3 N.D. 22.8 24.4 N.D. 16.0 13.4 11.0 11.1 N.D. 19
61 N.D. 30.3 N.D. 21.1 17.6 18.2 13.1 13.5 10.6 N.D. N.D. 26
62 N.D. 29.9 N.D. N.D. 18.9 17.2 15.7 15.0 12.4 11.2 N.D. 51
63 N.D. 25.0 20.1 19.2 16.7 15.9 13.7 12.8 11.5 10.7 N.D. 76
64 N.D. 24.1 N.D. N.D. 17.6 17.0 14.6 14.0 11.5 11.0 N.D. 94
65 N.D. 23.5 N.D. N.D. 19.0 16.7 14.5 13.4 13.2 10.6 N.D. 137
66 N.D. 24.6 N.D. N.D. 15.2 14.7 14.3 13.3 12.4 13.0 9.3 102
67 N.D. 24.7 30.6 N.D. 18.8 15.4 13.8 12.5 12.3 11.7 10.3 92
68 N.D. 21.5 20.8 19.3 19.5 15.4 13.3 12.1 11.6 8.8 N.D. 106
69 N.D. 23.1 20.4 19.7 N.D. 15.8 13.4 11.8 11.5 9.8 11.6 163
70 N.D. 24.5 21.1 17.8 18.9 15.6 13.5 12.1 10.9 10.2 9.7 287
71 27.4 21.9 21.2 19.6 18.5 15.2 13.0 11.3 10.6 9.3 8.1 148
72 N.D. 25.7 21.3 18.0 21.7 15.6 14.0 11.2 10.1 9.3 8.7 84
73 N.D. 25.5 20.7 19.9 17.9 16.2 14.0 11.2 10.1 9.4 8.8 630
*MPG figures for early model years (57-62) are based on limited data. This
is partly responsible for the wide scatter in this early'data.
N.D. - No Data
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D. Effect of Emission Control on Fuel Economy
Many things can be inferred from the mass of data. What has been
done here is to compare "C" values for each model year. The fuel economy
penalties in terms of the constant "C" for model years 68 thru 73 are
listed below.
TABLE II - Effect of Emission Control on Fuel Economy
Model Year
57-67 (Uncontrolled)
68
69
70
71
72
73
Average loss 68-73, 7.75%
The penalty due to emission controls as expressed above is far from the
only cause of the increase in national automotive fuel consumption and can
not be compared with total fuel consumption on a one for one basis. Factors
such as increasing car population, the relative number of miles driven by
controlled and pre-controlled cars, and the varying distribution of vehicle
weight in each model year also have to be taken into account. These factors
were not analyzed in this study and thus n£ conclusions concerning total
nationwide impact on fuel consumption are drawn.
"C" Value
lied) 52129
47108
47891
48320
47009
49362
48667
Fuel Economy Loss
(% of Uncontrol lei
None (baseline)
9.6
7.9
7.3
9.8
5.3
6.6
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E. Effect of Compression Ratio Changes
General Motors vehicles went to lower compression ratios across the
board in 1971, and others have since done the same. To isolate the effect
of compression ratio, data from one-hundred and seventeen 1970 and fifty-five
1971 GM cars of varying weight were examined.
TABLE III - Effect of Lower Compression Ratio, in MPG
Model Year 3500 1b 4000 Ib 4500 1b 5000 1b 5500 1b
70 13.7 11.4 10.4 9.9 8.5
71 13.6 11.5 10.7 9.6 8.1
The fuel economy was worse in three weight classes, and better in two.
These data do not demonstrate that lowering compression ratio had any effect
on vehicle fuel economy.
V. IMPACT OF OTHER AUTOMOTIVE DESIGN FEATURES ON FUEL ECONOMY
To provide an appropriate perspective the data presented above need to
be related to other fuel economy penalties being experienced in today's cars.
A. Air Conditioning
EPA laboratory tests of air conditioned full sized cars with and without
the air conditioner operating show a 9% loss in fuel economy over the Federal
driving cycle in a 70 degree F ambient temperature. This penalty can go as
high as 20% (based on compressor hp calculations) for continuous use on a
hot day in urban traffic. The penalty can obviously, also, be very low or zero
when air conditioning is used little or not at all. .The 9% loss measured in
the EPA tests is approximately midway between these limits and is considered
representative.
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B. Automatic Transmissions
The fuel economy penalty associated with the use of automatic
transmissions (AT's) is difficult to quantify. There are many types
of AT's (different numbers of speeds, and different operating principles).
The same engine will be tuned differently for use with an AT than for use
with a manual transmission, and different rear axle ratios are used with
AT's to optimize their performance. All of this compounds the problem of
identifying the impact of AT's on fuel economy. Periodicals on the subject
of vehicle performance have reported fuel penalties of 10% for AT's. On
the other hand, as indicated earlier, an AT may in certain circumstances improve
fuel economy. EPA does not have independent data on this question. In view
of all the available data, EPA concludes that the fuel economy penalty of
5% to 6% reported by General Motors in public hearings in April 1972 is
representative.
By comparing the fuel economy penalties of an automatic transmission or
air conditioning with the penalty attributable to emission controls, it can
be seen that the loss due to emission controls through the 1973 model year
is about the same size as the penalty incurred due to use of convenience
devices such as air conditioning or automatic transmissions.
C. Vehicle Weight
The fuel economy loss associated with emission controls is significantly
less than that many vehicle operators claim they are experiencing. One major
reason for this is that much of the decreased fuel economy observed is in fact
attributable to the phenomenon of nameplate weight growth. When a nameplate,
(Chevorlet Impala, for example) is first introduced, it identifies a vehicle
weighing a certain amount. Over the years however, vehicles with the same
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nameplates have typically become heavier, a trend often unnoticed by the
vehicle operator. The data in Table I and in Appendix I indicates the
dramatic influence of weight on fuel economy. If one only compares the fuel
economy of vehicles with the same nameplate (but different weights,) a
conclusion regarding the impact of a non-weight parameter (such as emission
control) on fuel economy will be wrong. The following example shows this
effect:
TABLE IV - Effect of Vehicle Weight Growth on Fuel Economy
YEAR CAR HEIGHT NAMEPLATE MPG
1958 4000 Ib Chevorlet Impala 12.1
1973 5500 Ib Chevorlet Impala 8.5
In this case, the additional 1500 Ibs is predominatly responsible for
the loss in fuel economy, not the emission controls.
VI. FUTURE TRENDS IN FUEL ECONOMY
A. The 1975/1976 Emission Control System
Very little valid or consistent data exists on fuel economy of 75/76
prototypes. Although some loss may be expected with the use of certain emission
control techniques, the small amount of data available to EPA does not yet
demonstrate any trends. This lack of trends is further supported by recent
(Nov. 1972) reports from several large auto manufacturers who report no difference
in the fuel economy of their 1975 prototypes and 1973 vehicles of the same
weight.
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TABLE V - Comparison of Fuel Economy of 1975/76 Prototypes with 1973 Vehicles
Vehicle Type Inertia Weight
75 Prototype
75 Prototype
75 Prototype
75 Prototype
76 Prototype
76 Prototype
76 Prototype
4000
4500
5000
5500
5000
5000
5000
# of Tests
1
3
1
1
1
1
1
Prototype Fuel 1973 Vehicles
Economy
10.0
10.7
9.3
6.9
8.6
9.5
6.6
Average
11.2
10.1
9.4
8.8
9.4
9.4
9.4
Ranqe
7.7-14.6
7.4-13.6
7.6-11.8
7.1-10.0
7.6-11.8
7.6-11.8
7.6-11.8
See also Figure 1.
Based on the limited data available from 75/76 systems, the only thing
that can be said is that a trend toward better or worse fuel economy has not
been demonstrated at this time.
B. Future Height Trends
Vehicles have historically been getting heavier. Any influences which
causes the weight to go up will reduce fuel economy. A major factor is the
potential increase in vehicle weight due to future safety standards. The
target weight for the Department of Transportation Experimental Safety Vehicle
(ESV) was 4200 pounds. Automotive Engineering, September 1972 P.32, reports
that the prototype vehicles had weights of 4900, 5300, 5400, and 5800 pounds.
If future vehicles in the standard size class increase as much as these
prototypes (700 to 1600 Ib) - fuel economy will suffer. As a hypothetical
example, increasing the weight of the average 1973 4000 Ib vehicle to 5000 Ib
could mean a drop in fuel economy from 11.2 to 9.4 MP6, a 16% fuel economy penalty.
C. Future NewEngines
1. Rotary Engine
While many engines are being investigated as replacements for the conventional
spark-ignition, reciprocating engine, the one with the highest potential for near ,
term use is the rotary, or Wankel, engine. Despite the recent increase in publicity,
the Wankel is not a newly developed engine. It has been under development for over '
20 years and in production for over 5 years by certain foreign manufacturers.
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FIGURE 1
FUEL ECONOMY VS VEHICLE WEIGHT
Federal Driving Cycle
- 75 Prototypes vehicles
A- 76 Prototypes vehicles
Pre-controlled Cars
(average 57-67)
All 1973 Cars
1973 Diesel
(Mercedes-220D)
Prototype
Stratified Charge (Capri)
1973 Rotary Engines
1.000
Vehicle Inertia Weight (pounds)
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Vehicle
14.6*
13.3
12.1
12.3
11.9
14.9*
Average
20.7
19.9
17.9
17.9
17.9
16.2
18.'
13.:
11.'
11.'
11.'
13.i
16
The data available to EPA on fuel economy of rotary engine vehicles
is presented below and compared to data on 1973 vehicles of the same weights
but equipped with conventional reciprocating engines. See also Figure 1.
TABLE VII - Comparison of Rotary Engine Fuel Economy With 1973 Vehicles
Inertia Weight Rotary Engine 1973 Vehicles
^_ Range
2250
2500
2750
2750
2750
3000 14.9* 16.2 13.6 to 19.7
*Not 1973 vehicles.
The rotary engine fuel economy results are consistently at or near the bottom
of the range in each weight class and are significantly below the average. The
fuel economy data on the 1973 rotary engine vehicles represents a 35% loss in
fuel economy when compared to the average for the same weight vehicles equipped
with conventional engines. Historically, engines have improved in performance
as their development continues and their use increases. Whether this will be
the case with the fuel economy, of the rotary engine is not known.
2. Diesel Engine
The Diesel engine is the only engine other than the gasoline, spark-
ignition, rotary and reciprocating engines that is being used commercially
in significant numbers in passenger cars in this country (approximately
6000 are imported each year). The Diesel, however, is not a new engine. It
has been used in trucks for over 30 years and is widely used in passenger cars
in Europe. The data available to EPA on the fuel economy of a diesel engine
vehicle are shown below, and compared to that on 1973 vehicles of the same
weight equipped with conventional engines.
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TABLE VIII - Comparison of Diesel Engine Fuel Economy With 1973 Data
Inertia Weight Diesel All 1973 Vehicles
Average Range
3500 24.7 14.0 9.8 to 17.8
The Diesel (which in this case met the emission levels required by the 1975
standards) achieved 75% better fuel economy than the average 1973 vehicle
of the same weight equipped with a conventional engine. See also Figure 1.
3. Other Engines
In addition to the Wankel and Diesel, several other engines are being
considered as replacements for the gasoline, spark-ignition, reciprocating
engine. These include stratified charge, Stirling, Rankine cycle and gas
turbine engines.
For these engines, valid data exists for only the stratified charge
engine. At an inertia weight of 2,500 pounds, a vehicle equipped with a
stratified charge engine (which in this case met the emission levels, at
low mileage, required by the 1976 standards) demonstrated fuel economy of
about 23 miles per gallon or 12% better than the average 1973 vehicle of
that weight. See Figure 1. Valid data on the fuel economy of the other
possible engines is not available at this time.
VII. SUMMARY
The EPA has analyzed fuel economy data from more than 2000 cars (of
which over 1400 were equipped with emissions controls) tested on the Federal
Driving Cycle.
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The data were derived from certification, surveillance and inhouse
evaluation testing. This is the most extensive data analysis known to have
been.performed on this subject to date. It is also considered to be the
most accurate for the purpose of comparing vehicle design parameters because
of the use of a single consistent driving cycle and controlled ambient conditions.
The study indicates that vehicle weight is the single most important vehicle
design parameter affecting fuel economy. Past and future increases in vehicle
weight have had, and will continue to have, a significant adverse effect on fuel
usage. Weight is a parameter over which the car buyer has direct discretionary
control.
The average fuel economy loss due to emission control for 1968-1973 vehicles
is less than 8%. This penalty is approximately equal to the penalty associated
with the use of convenience devices such as air conditioning or automatic
transmissions. Despite the many statements regarding the loss in fuel economy
due to meeting the 1975/1976 standards, no significant trend has yet developed
in the data available to EPA. EPA will continue to gather data on 75/76 prototype
with the aim of making a more definitive statement in the future.
The use of engines other than the present spark-ignition, reciprocating
engine could have a significant impact on vehicle fuel economy. Use of the
spark-ignition, rotary engines presently results in significant losses in
fuel economy, while the Diesel engine offers a significant increase in fuel
economy.
VIII. CONCLUSIONS
1. Vehicle weight is the single most important parameter affecting
urban fuel economy; a 5000 pound vehicle demonstrates 50% lower fuel
economy than a 2500 pound vehicle.
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2. The fuel economy loss for 1973 vehicles, compared to uncontrolled
(pre 68) vehicles, is less than 7%. The average fuel economy loss due
to emission control for all controlled (68-73) vehicles is 7.7%.
3. The fuel economy penalty due to the use of convenience devices such
as air conditioning or automatic transmission is roughly equal to the
penalty due to emission controls.
4. No trend is shown for fuel economy for 1975 and 1976 vehicles at
this point in time. More data are needed.
5. Data on 172 1970 and 1971 GM cars did not demonstrate any effect
on fuel economy of reduced compression ratio.
6. Future trends, including increased vehicle weight and possible use
of the rotary engine, may result in a significant (20%-35%) fuel economy
penalties.
7. The Diesel and stratified charge engines show better fuel economy
then the conventional engine with the Diesel showing a fuel economy
improvement of more than 70%.
8. Today's car buyer has available a choice of vehicles in terms of the
size and weight, engine type, and convenienge devices. These choices
can influence a vehicle's fuel economy over a range of 4 to 1 (See
Range of Data in Appendix I).
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FOOTNOTES:
V Fuel economy should not be confused with fuel consumption which is expressed
Th terms of gallons of fuel consumed per mile. One is the inverse of the other.
A certain percentage increase or decrease in fuel economy does not equal the
same percentage decrease or increase in fuel consumption. For example, one car
getting 20 MPG has 33% better fuel economy than one with 15 MPG. However its
fuel consumption is 25% less. The two terms cannot be used interchangeably.
2_/ Calculation of Fuel Economy
Since both CO and CO? are measured for the test, an approximate
carbon balance fuel economy figure can be generated from the CO and
C02 data. The formulae used are:
72 FTP MPG = 2360
.429 (CO) + .272 (C02)
Where the dimensions of CO and CO, are grams per mile for the complete test.
75 FTP MPG = 17800 _
.429 (CO) + .272 (COo)
Where the CO and the C0? are the total number of grams of CO and OL in
Bags 1 and 2. ^
Both of these formulae neglect the hydrocarbon contribution to the
carbon balance. This however is not serious if the data are used for
comparative purposes as is the case in this analysis. In addition, to
the accuracy to which the data are reported, the neglect of the hydrocarbons
influence is not important.
The accuracy of any single data point is believed to be within +_ B%
of the true value. This is the maximum inaccuracy in the C02 measurement.
The accuracy of the mean or average values is believed to be much higher
since the experimental errors are random and tend to cancel out in the
sample. No statistical analysis has been performed on this data. The data
and conclusions presented on the preceding pages are based only on the
observed means of the samples.
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APPENDIX I
Inertia Weight Average _MPG_ Range # of Data Points
Model Year 1973
2000
2250
2500
2750
3000
3500
4000
4500
5000
5500
Model Year 1972
2000
2250
2500
2750
3000
3500
4000
4500
5000
5500
Model Year 1971
1750
2000
2250
2500
2750
3000
3500
4000
4500
5000
5500
Model Year 1970
2000
2250
2500
2750
3000
3500
4000
4500
5000
5500
C = 48667
25.5
20.7
19.9
17.9
16.2
14.0
11.2
10.1
9.4
8.8
C = 49362
25.7
21.3
18.0
21.7
15.6
14.0
11.2
10.1
9.3
8.7
C = 47009
27.4
21.9
21.2
19.6
18.5
15.2
13.0
11,3
10.6
9.3
8.1
C = 48320
24.5
21.1
17.8
18.9
15.6
13.5
12.1
10.9
10.2
9.7
23.7 to 28.5
18.9 to 21.9
13.3 to 23.7
11.9 to 23.7
13.6 to 19.7
9.8 to 17.8
7.7 to 14.6
7.4 to 13.6
7.6 to 11.8
7.1 to 10.0
21.4 to 37.8
18.5 to 27.8
17.0 to 19.0
13.0 to 41.7
10.1 to 20.6
10.7 to 19.2
6.3 to 15.3
8.5 to 11.3
7.8 to 10.6
7.8 to 9.2
—
19.3 to 23.9
18.7 to 27.0
14.7 to 25.0
16.8 to 21.9
7.8 to 20.7
8.9 to 20.2
8.8 to 13.6
7.8 to 12.7
5.4 to 15.4
-
20.2 to 32.0
13.1 to 40.1
10.9 to 22.1
15.8 to 20.2
11.5 to 22.4
9.4 to 17.7
8.5 to 15.6
7.3 to 13.3
6.6 to 13.4
8.3 to 12.2
6
8
74
62
37
64
69
157
96
57
5
5
2
10
7
5
28
8
11
3
1
6
11
16
6
10
15
42
30
10
1
8
7
11
9
21
65
78
51
30
7
-------
A-2
InertiaWeight
Average MPG
Range
I of Data Points
Model Year 1969
2000
2250
2500
3000
3500
4000
4500
5000
5500
C = 47891
23.1
20.4
19.7
15.8
13.4
11.8
11.5
9.8
11.6
15.3 to 26.0
17.8 to 24.4
18.1 to 26.8
10.5 to 19.8
9.8 to 17.4
9.0 to 15.4
9.1 to 21.2
8.7 to 11.7
10.2 to 12.9
14
4
13
13
37
43
31
6
2
Model Year 1968
2000
2250
2500
2750
3000
3500
4000
4500
5000
Model Year 1967
2000
2250
2750
3000
3500
4000
4500
5000
5500
Model Year 1966
2000
2750
3000
3500
4000
4500
5000
5500
C = 47108
21,
20,
19.
19.
15.
13.
12.
11.
8,
C = 54170
24.
30.
18.
15.
13.
12.
12.
11.
10.
C = 48934
24.
.15,
14.
14.
13.
12.
13,
19.9 to 23.6
11.9 to 19.8
9.5 to 25.0
8.8 to 14.8
9.1 to 14.2
8.7 to 8.9
20.0 to 33.0
17.9 to 19.7
13.0 to 17.1
11.5 to 18.6
8.4 to 19.7
9.7 to 13.4
10.7 to 12.1
20.5 to 31.2
12.0 to 16.9
10.0 to 20.7
8.6 to 28.8
9.8 to 15.5
10.9 to 16.9
9.3
8
1
1
1
15
29
31
18
2
8
1
2
5
21
36
16
2
1
6
1
16
25
34
16
3
1
-------
A-3
Inertia Weight
Average MPG
Range
# of Data Points
Model Year 1965
2000
2750
3000
3500
4000
4500
5000
Model Year 1964
2000
2750
3000
3500
4000
4500
5000
Model Year 1963
2000
2250
2500
2750
3000
3500
4000
4500
5000
Model Year 1962
2000
2750
3000
3500
4000
4500
5000
C = 50581
23.5
19.0
16.7
14.5
13.4
13.2
10.6
C = 50259
24.1
17.6
17.0
14.6
14.0
11.5
11.0
C = 48209
25.0
20.1
19.2
16.7
15.9
13.7
12.8
11.5
10.7
C = 56105
29.9
18.9
17.2
15.7
15.0
U.4
11.2
19.0 to 27.5
16.4 to 21.2
10.9 to 21.9
8.4 to 21.8
9.5 to 19.7
7.4 to 27.8
10.1 to 11.0
22.1 to 26.6
16.3 to 20.5
14.3 to 20.9
10.2 to 29.8
9.6 to 30.4
8.6 to 15.5
10.2 to 11.6
22.3 to 27.2
-
-
14.4 to 21.2
10.5 to 20.1
6.0 to 19.0
9.2 to 18.3
9.3 to 13.5
-
25.8 to 38.0
17.1 to 20.6
13.3 to 20.1
13.2 to 18.6
9.4 to 18.6
10.5 to 14.3
10.2 to 12.1
4
8
18
42
46
15
4
3
8
21
28
19
12
3
3
1
1
8
15
19
18
10
1
4
2
9
10
19
5
2
-------
A-4
Inertia Weight
Average MPG
Range
# of Data Points
Model Year 1961
2000
2500
2750
3000
3500
4000
4500
C = 53672
30.3
21.1
' 17.6
18.2
13.1
13.5
10.5
_
19.9 to 22.2
12.0 to 21.3
17.5 to 18.9
8.7 to 17.5
10.5 to 17.1
9.6 to 12.3
1
5
4
2
2
9
3
Model Year 1960
2000
2500
2750
3500
4000
4500
5000
Model Year 1959
2000
3000
3500
4000
4500
5000
Model Year 1958
2000
2250
2750
3500
4000
4500
5000
Model Year 1957
2000
3500
4000
5500
C = 52474
20.3
22.8
24.4
16.0
13.4
11.0
11.1
C = 56386
29.4
15.
15,
14.1
13.4
13.9
C = 48095
26
19
13
14
14
.2
.5
.4
.2
.4
12.8
10.1
C = 54537
26.5
14.8
13.9
12.9
15.1.to 16.8
9.9 to 17.9
10.6 to 11.4
18.7 to 44.2
15.3 to 16.1
14.4 to 16.1
10.6 to 17.7
10.6 to 17.5
-11.9 to 17.0
10.8 to 20.2
11.2 to 15.1
23.0 to 31.9
11.5 to 18.3
9.4 to 21.6
1
1
1
2
11
2
1
3
2
3
13
3
1
1
1
1
8
9
3
1
3
13
7
1
------- |