74-27
A COMPARATIVE STUDY OF THE FUEL ECONOMY CHARACTERISTICS
OF MAZDA ROTARY ENGINE VEHICLES VERSUS CONVENTIONAL
RECIPROCATING ENGINE VEHICLES
April 1974
Test and Evaluation Branch
Emission Control Technology Division
Environmental Protection Agency
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A COMPARATIVE STUDY OF THE FUEL ECONOMY CHARACTERISTICS
OF MAZDA ROTARY ENGINE VEHICLES VERSUS CONVENTIONAL
RECIPROCATING ENGINE VEHICLES
Introduction
Because of the widespread public interest in the fuel economy per-
formance ,of new automobiles available for purchase in the United States,
the Environmental Protection Agency published, on September 18, 1973,
the fuel economy results of 1974 model year prototype vehicles tested
by the EPA in its emission control certification program. The driving
cycle utilized in this program is representative of typical city vehicle
operation; the driving cycle is 7.5 miles long, and the test begins with
a cold start which is representative of typical commuter driving.
The fuel economy data were grouped by the weight class of automobiles,
because vehicle weight is the single most important vehicle design factor
characterizing fuel economy. Within each weight class, vehicles were
listed in order of their fuel economy performance, with the best per-
formers, in terms of highest miles per gallon, listed first.
The data published for the 2750 Ib. inertia weight class included
a range of fuel economy performance from a high of 24.6 mpg to a low of
10.6 mpg. The lowest fuel economy in the 2750 Ib. weight class was achieved
by three rotary engine Mazda vehicles: 10.6, 10.8 and ILO^mpg. Exclusive
of these three vehicles, the range of fuel economy results in the 2750 Ib.
class was from 24.6 to 15.1 mpg; in other words, the next lowest performing
vehicle in the 2750 Ib. weight class achieved 37% better fuel economy than
did the best rotary Mazda, while the best performer in the class achieved
124% better fuel economy.
When these data were first published, Washington counsel for Mazda
Motors of America informally contacted the EPA to convey the point of view
that Mazda Motors of America believed that the fuel economy results of its
vehicles were substantially better than that reported by the EPA. EPA
invited Mazda Motors to provide data to support the contention that an
error had been made in the EPA testing of Mazda vehicles. No such data
were presented at that time.
Early in January of 1974, United Press International carried a story
datelined Los Angeles which, stated that "Mazda Motors of America today
accused the Environmental Protection Agency of publishing misleading
figures about the fuel consumption of its Wankel-powered cars. Mazda
presented a report by J. D. Powers and Associates, a Los-Angeles research
firm, indicating a majority of owners of the rotary engine Mazda were
getting 17 miles per gallon in city driving and 20 miles on the highway."
The fuel economy for this vehicle was originally reported as 10.7 mpg
due to a clerical error.
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In response to inquiries on this matter from UPI, EPA explained the
basis of its fuel economy testing, and expressed the view that it is
confident that the relative fuel economy results on all cars for which
EPA has published fuel economy data, including the Mazda rotary, are
valid.
Mazda Motors of America, after these newspaper stories, offered in
rebuttal a variety of reports and statements from owners to the effect
that the fuel economy of its vehicles is higher than that reported by
the EPA. EPA technical staff studied these materials, and concluded
that they did not invalidate the relative fuel economy results measured
by EPA on the Mazda rotary engine car. Even though different absolute
miles per gallon results were reported in various studies, as would be
expected because of the differing test procedures used, several of these
studies commented specifically on the relatively low fuel economy per-
formance of the Mazda rotary engine car (compared to other equivalent
weight vehicles).
However, to further investigate Mazda Motors of America's assertion
that the Federal Test Procedure, while an adequate test for conventionally-
powered cars (including, according to Mazda, its own conventional car),
may be inadequate to fairly assess the fuel economy results of rotary
engine cars, the EPA invited Mazda to participate with it in a test pro-
gram. The purpose of this test program was to investigate whether in
the case of the rotary engine car the relationship of fuel economy in
city driving to highway driving may be different from that relationship
for conventionally-powered cars. The hypothesis was that if such a dif-
ference exists, it could help to explain the different fuel economy
results reported by Mazda and by EPA.
On March 4, 1974, Mazda Motors of America accepted the EPA invitation
to conduct a test program that consisted of the following basic approach:
A) EPA would develop a highway driving cycle that would simulate
on the chassis dynamometer a typical manner in which vehicles
are driven outside of cities.
B) EPA would determine the comparative fuel economy of Mazda and
contemporary piston engine vehicles on the newly developed high-
way driving cycle and the Federal City Driving Cycle.
2
EPA technical staff had for several months been working on a highway
test cycle with the SAE, and was in any case ready to define a highway
test cycle for 1975 model year testing.
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C) EPA would conduct such.other tests as might help to identify
inherent differences between the rotary and piston engine that
could further explain the fuel economy differences between the
engine types. Essentially, these tests.would involve determining
hot start versus cold start fuel economy characteristics of the
two engine types.
D) Other manufacturers would be invited to supply vehicles powered
by conventional piston engines for fuel economy performance
comparison with the Mazda rotary engine vehicles.
Background of EPA Fuel Economy Data
The President's Energy Message of April 18, 1973, directed EPA, in
cooperation with the Department of Commerce and the Council on Environmental
Quality, to develop a voluntary auto fuel labeling program beginning with
1974 model year cars. EPA promptly published the fuel economy
results that 1973 model year cars had demonstrated during testing at the
EPA laboratory for the purpose of certification that their air pollution
emissions were within Federal standards. Under Federal law, cars may
not be sold in the U.S. unless they comply with air pollution standards,
and thus prototype models of all basic types of cars are tested bv EPA
each year. The 1973 fuel economy data were published in the Federal
Register; beginning with the 1974 model year, some of the data appeared in
dealers' showrooms, and on the car themselves.
All fuel economy testing has its limitations, because fuel economy
of any individual vehicle depends on many factors, one of the most im-
portant being how the vehicle is driven. The EPA has clearly pointed out
in the fuel economy data that it has published that individual drivers
can expect to get better or poorer fuel economy on their own cars of the
same type as tested by EPA, depending primarily on such factors as the
options on the car they buy, number of short and long trips, use in city
traffic or at steady speeds, and personal driving habits.
The EPA Federal City Driving Cycle test involves driving the vehicle,
on a dynamometer, through a 7.5 mile driving cycle that is typical of
city/suburban driving common to urban commuting. The test begins when
the vehicle is cold, because a cold start is typical of commuting travel.
This test procedure is different from fuel economy test procedures typically
used by automakers since automakers test their cars, with engines that are
already warmed up, at more or less steady speeds on a test track or on
the highway. The EPA test is far more repeatable than a test track or
highway fuel economy test, and of course more accurately represents the
type of driving of a typical commuter; also, the EPA-published fuel economy
data is the only data available on so large a number of different cars
that is obtained under strictly controlled, entirely repeatable conditions,
and for that reason provides the best basis for comparing the relative
fuel economy of cars that are available for purchase by consumers.
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Technical Characteristics of the Mazda Rotary-Powered Vehicle
The combustion chamber configuration of the rotary engine is unusual
in that it is extremely elongated in comparison to the conventional re-
ciprocating piston engine. This elongation results in the occurrence, of
three phenomena that create an unburned hydrocarbon problem for the un-
controlled rotary engine. The first phenomenon, wall quenching, perhaps
the most important emission source, results from the quenching or ex-
tinguishment of the flame front as it approaches the relatively cool
combustion chamber walls. The second phenomenon occuring in the rotary
engine is the "crevice effect" which is another quench process that
occurs where two relatively cool surfaces enclose an air/fuel mixture
at close proximity. In the rotary engine the crevices are formed at
the junction of the rotor tip and the housing and in effect represent
"dead-volume" where combustion does not occur. The third phenomenon
"seal leakage" or "blowby" is resultant from the complex sealing
required for the rotary. Even a small percentage of unburned mixture
can have a large effect on the overall concentration of hydrocarbons.
Consequently the uncontrolled rotary engine emits large quantities of
hydrocarbon relative to the reciprocating engine.
Fortunately, the high exhaust temperatures of the rotary engine
make the rotary conducive to relatively effective exhaust emission control
through the use of thermal reactor technology. The achievements of Toyo
Kogyo (manufacturers of Mazda) in this area are particularly significant
since in past EPA tests Mazda prototype vehicles have demonstrated3
capability of easily meeting 1975 statutory Federal emission standards
(0.41 gm/mi HC, 3.4 gm/mi CO, 3.1 gm/mi NOx). However, the most efficient
operation of the thermal reactor occurs with rich air/fuel ratios and
fuel economy must be traded-off for emissions control. In short, the
rotary engine/thermal reactor combination, while representing an ex-
cellent approach for emissions control, is not an optimum combination
for fuel economy.
One additional technical characteristic of the Mazda rotary which
could affect the reported fuel economy is that oil for lubricating of the
apex seals is injected into the combustion chamber. The combustion of
this oil could result in lower fuel economy being reported because any
measured carbon in the exhaust due to combustion of this oil would be
included in the carbon balance calculation. However, the effect of this oil
contribution to the fuel economy calculation is less than 1% for the Mazda
rotaries. At the typical rotary engine oil consumption rate of one-half to
one quart of oil per one thousand miles, the rotary engine vehicles would have
consumed 0.001 to 0.002 gallons of oil over the 7.5 mile city driving cycle.
Inclusion or exclusion of this oil consumption from the fuel economy
calculation would mean a difference of 0.02 to 0.04 miles per gallon, a
difference far too small to measure with accuracy.
3 Reference EPA test report 73-15, "An Evaluation of Two Toyo Kogyo 1975
Prototypes with Rotary Engines
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To address the Mazda Motors assertion that the Federal City Driving
Cycle is particularly disadvantageous to the rotary engined vehicle from
a fuel economy point of view, EPA also examined the detailed features of
the Mazda control system to determine if certain technical characteristics
might specifically penalize the Mazda rotary. This evaluation of the
Mazda control approach did suggest two control features which may detract
from fuel economy during cold start city driving:
1. Like the catalyst system, which will be used on future year cars,
the thermal, reactor must achieve a minimum operating temperature
to be effective for emission control. Consequently, during the
cold start phase the trailing spark p'lug of the Mazda engine is
rendered inoperative until the engine coolant reaches about
130°F, at which time the trailing spark plug is activated. This
mode of start-up causes the exhaust temperatures to be much
hotter thus allowing rapid warm-up of the thermal reactor. Of
course, the engine is less efficient during this period of only
one spark plug operation, and a fuel economy penalty is incurred.
It should be noted, however, that spark advance on conventional
engines is often modulated in an analogous fashion to facilitate
exhaust emission control during warm-up, and thus the effect on
fuel economy of Mazda's approach may not be unique. Nevertheless,
it merited further evaluation.
2. During deceleration and idle periods, the thermal reactor could
cool down enough to render the thermal reactor inefficient for
emission control. To offset this process, the Mazda control system
modulates air/fuel mixture and maintains partial throttle during
these modes of operation. This characteristic may contribute to
losses in fuel economy. However, it should also be noted that this
type of control during deceleration is also used in certain electronic
fuel injection systems.
Highway Cycle Developmelit
The development of a suitable highway fuel economy test cycle was a
project that happened to coincide, in terms of timing, with the need to
develop such a test cycle for 1975 model year fuel economy evaluations.
A description of that cycle development program has been prepared for this
latter purpose. For complete details of that development refer to the
EPA Emission Control Technology Division's report "Development of Highway
Driving Cycle for Fuel Economy Measurements;" A speed versus time analysis
of this cycle is presented in 'the Appendix to this report.
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Vehicle Test Fleet
Table I shows the salient features of the vehicles agreed upon between
EPA and Mazda Motors of America for use in the test program. All vehicles
were obtained from their respective manufacturers. It should be noted that
the manufacturers were allowed to supply these vehicles in the best possible
state of tune; hence, fuel economy performance was potentially maximized.
TABLE I
Vehicle Characteristics
Make/Model Engine Family
Mazda RK2
Mazda BX3
Mazda RX4
AMC Gremlin
Saab 99EMS*
GM Vega
GM Vega
Ford Torino
70 CID/Toyo-3
70 CID/Toyo-3
80 CID/Toyo-4
232 CID/IA
121 CID/BE20
140 CID/GM 101
140 CID/GM 101
351 CID w/White
Garb.
(// Carb-# Venturi)
1-4
1-4
1-4
1-1
inj.
1-2
1-2
1-2
Trans.
Axle
Ratio
Inertia
Weight
Class
4 -man.
3-auto .
4-man .
3-man.
4-man.
4-man.
3-auto.
3-auto .
3.90
3.70
3.90
2.73
3.89
2.92
2.92
2.75
2750
2750
3000
3000
2750
3000
3000
4500
The reciprocating engine vehicles were selected to allow varied comparisons
with the Mazda rotaries. The Saab represents a small, luxury type vehicle
with performance similar to the Mazdas. The Torino in previous EPA testing
had demonstrated similar fuel economy to the Mazdas, while being in a
substantially higher inertia weight category. The Gremlin and Vega vehicles
represent other popular small cars in the Mazda weight class.
Vehicle Testing Program
Each vehicle was subjected to the same test procedure. Cars received
in the lab were prepared for testing by draining the fuel and replacing
it with Indolene gasoline. (At Mazda's request their vehicles were fueled
with unleaded Indolene gasoline while all other vehicles were fueled with
3 gram/gallon leaded Indolene. The request was made to avoid spark plug
Saab requested and received a recent "running change" for their distributor
calibration. EPA approved that change and testing was performed on a
vehicle incorporating the recent change. Data both with and without this
change is included in the Appendix for comparison.
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fouling of the Mazda rotaries and the use of low-lead fuel is recommended
in the Mazda Owner's Manual. This difference in fuel was not anticipated
to have a significant effect on fuel economy because the manufacturers
were permitted to tune the vehicle prior to the test. While no evappratiye
testing was performed, exhaust emissions tests were conducted on each vehicle
as specified in Federal regulations for 1975 and later model year light
duty vehicles. After completion of the normal Federal driving cycle the
vehicles were allowed to idle for one minute prior to initiation of the
highway driving cycle. Additional cooling air was requested by the manu-
facturers during the highway cycle for the Mazda vehicles and the Saab
vehicle to avoid possible engine or control system over-temperature under
the limited cooling normally supplied during dynamometer operation.
Fuel economy for each driving cycle was calculated from the measured
emissions of hydrocarbon, carbon monoxide and carbon dioxide using a carbon
balance technique.5 For comparative purposes gravimetric analysis of fuel
consumption was used for the Mazda and a Vega vehicle, in addition to the
carbon balance. The comparison is shown in the Appendix to this report.
It should be noted that with the exception of the Vega vehicles, which
were tested only with the additional ten percent horsepower loading specified
for air conditioning, all of the vehicles were tested both with and without
air conditioning load simulation. While all of the test data are presented
in the Appendix, in subsequent sections of this discussion all of the cars
will be compared with the additional 10% power absorption to simulate an
air conditioning load.
Each vehicle was inspected to assure that the vehicle was calibrated
within the tolerances specified by the manufacturers in their 1974 certifica-
tion application. Additionally, emission results were compared to certifica-
tion results to verify the validity of the vehicle's emission control per-
formance. This comparison showed that all of the vehicles did meet the
1974 emission standards.
Test Results
Table III presents the ranked average ratio of the highway cycle fuel
economy to the Federal test cycle fuel economy. This ratio is called the
B/A ratio in the subsequent portions of this report. For the purpose of
This procedure is detailed in "A Report on Automotive Fuel Economy,"
EPA, OAWP, October 1973.
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this table and all subsequent analyses presented,, average fuel economy
for the two or more tests conducted was calculated using the harmonic
mean^ rather than the arithmetic mean.
TABLE III
Ranked List of Ratio of Highway Cycle Fuel Economy
to Federal Cycle B/A Ratio
Vega Manual 1.75
Mazda RX4 1.64
Torino 1.60
Mazda RX2 1.58 '
Gremlin 1.54
Saab 1.49.
Vega Automatic 1,48
Mazda RX3 1,43
A statistical analysis of the data grouped as rotary engines versus
reciprocating engines was made to check the hypothesis that is apparent
from simple inspection of the data in Table III, i.e., that the mean B/A ratio
of each group was statistically the same for the two groups. That analysis,
with 99% confidence, did not reject that hypothesis. On the basis of this
statistical test, EPA concludes that there is no significant difference
between the average B/A ratio of the rotary engine powered Mazdas and the
average B/A ratio of the conventional reciprocating engine powered vehicles
included in the test program.
Table IV shows the ranked fuel economy for all of the vehicles for
both the Federal City Driving Cycle and for the Highway Cycle. While
indicating minor juxtiposition between the Federal City and Highway ranked
lists, reinforces EPA's judgement that the EPA published fuel economy
data is a reasonably valid predictor of overall relative fuel economy
performance. This outcome of the test program does not support the argument
that the Federal City Test Cycle unfairly ranks the Mazda rotary.
The following example illustrates the effect of using the harmonic mean
rather than the arithmetic mean. Suppose a motorist took a trip of 600
miles and used three tanks of gasoline. For the first 200 mile segment
he used 10 gallons, in the second 200 mile segment he used 20 gallons and
for the third 200 mile segment he used 18 gallons. The arithmetic mean
of the individual fuel economies would be 13.7 mpg - a wrong answer.
The trip was 600 miles total using 48 gallons with an economy of 12.5 mpg.
The correct answer is obtained by finding the harmonic mean.
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TABLE IV
Ranked Fuel Economy
City Driving
Cycle
Saab
Vega, auto
Gremlin
Vega, manual
Mazda RX2
Mazda RX3
Mazda RX4
Torino
%
20.6 mpg
18.7 mpg
17. 7 mpg
17.5 mpg
13.4 mpg
13.3 mpg
12.5 mpg
12.5 mpg
', Lower than
Best
__
9%
14%
15%
35%
35%
32%
32Z
Highway Driving
Cycle
Vega, Manual
Saab
Vega, auto.
Gremlin
Mazda RX2
Mazda RX4
Torino
Mazda KX3
30.7 mpg
30.6 mpg
27.7 mpg
27.2 mpg
21.2 mpg
20.5 mpg
20,0 mpg
19.0 mpg
Lower than
Best
10%
11%
31%
33%
35%
38%
The "% Lower than Best" columns in Table IV indicate the relative
fuel economy performance of the test vehicles in comparison to the best
performer tested, e.g. in city driving the Torino and Mazda vehicles got
35 to 32 percent lower fuel economy than the Saab. Interestingly, except
for the manual transmission Vega this relative performance is not signi-
ficantly different for the highway cycle when compared to the city cycle,
e.g. the Torino and Mazda vehicles got 31 to 38 percent lower fuel economy
than the Saab. This, of course, is attributable to the relative constancy
for the B/A ratio for the cars tested.
A comparison, where possible, was made of the cold start city driving
fuel economy of the test cars included in this test program, and the fuel
economy achieved under the same conditons by prototypes of these vehicles
in the 1974 model year certification program. Table V presents these
data for the Vega, Mazda and Ford vehicles. Direct comparison of the
other vehicles was not possible because comparable certification pro-
totypes were not tested by EPA.
From these data it can be seen that the Mazda vehicles and the Ford
Torino demonstrated higher cold start city driving fuel economy in this
test program than they did in 1974 certification testing; the Vega
vehicles' fuel economy results were within 5% of each other, which is
within the test-to-test variation that can be expected.
To explore the reasons for the differences in the fuel economy
results of the Mazdas and the Torino, a complete review of both vehicular
and test parameters was made. The parameters checked are listed in
Table VI. With the single exception of a clerical error on one Mazda
test, no discrepancies were found that would account for the differences
in fuel economy results?.
7 The Mazda vehicles' carburetors were not flow tested. Valid comparison
of flow tests results can best be made using the same apparatus and pro-
cedures as employed to generate the flow curves submitted during the
certification process. In the case of the Mazda vehicles such testing
would have had to be performed in Japan. EPA considered this possibility
and decided that it was Impractical.
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TABLE V
Comparison of City Driving Ccold start)
Fuel Economy - This Program
vs. 1974 Certification Results
Certification
Fuel Economy
Vehicle
Mazda RX2
•-i
Mazda RX3
Mazda RX4
Torino
Vega**
Vega**
Trans .
Manual
Auto
Manual
Auto
Auto
Manual
EPA
10.6 mpg
11.0*mpg
10.4 mpg
10.8 mpg
17.9 mpg
17.4 mpg
Manufacturer
12.1 mpg
12.1 mpg
11.3 mpg
10.4 mpg
.
Program
13.4 mpg
13.3 mpg
12.5 mpg
12.5 mpg
18.7 mpg
17.5 mpg
**
Due to a clerical error the results for this vehicle had been
previously reported by EPA as 10.7 mpg.
The same certification prototype tested by EPA for 1974
certification was furnished by General Motors for test
in the Rotary/Piston Fuel Economy Program.
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TABLE VI
Summary of Parametric Checks
Vehicular Parameters
Ford Torino
- Vacuum hose routing and connections
- Basic ignition timing
- Spark delay valve
- Carburetor number
- Carburetor flow curve (supplied by Ford)
- Choke setting
- Choke lever arm length
- Axle ratio
- Tire size
Mazda Rotary Vehiile
- Distributor calibration
- Control unit and modulating switches
- Carburetor number
- Deceleration and air control valve
- Throttle release
- Idle switch
- Altitude compensator
- Decel valve
- Air control valve
- Air pump and connections
- Axle ratio
- Tire size
Test Parameters
Dynamometer inertia settings
Dynamometer horsepower settings
Dynamometer power absorption calibration
Constant volume sampler calibration
CO2 analytical measurement calibration
Fuel economy calculation
Test cell and ambient temperature and barometric pressure
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Inasmuch as the Ford and EPA fuel economy tests on the Ford Torino
certification prototype vehicle correlated closely, the differences
in the results between certification vehicle and the special test
program Torino must be attributed to differences in the state of
tune of the vehicles Csee below for further discussion of this factor).
As regards the Mazda vehicles, for which EPA test results did not
correlate closely with results achieved in the Toyo Kogyo lab in Japan,
further investigations were made of test data drawn from two other
sources: results of end-of-assembly-line vehicles tested by Toyo Kogyo
in Japan, and results of new vehicles tested by the California Air
Resources Board on riew vehicles sampled at ports of entry. These results
are listed in Table VII, together with the Toyo Kogyo and EPA certi-
fication test results.
A number of observations and conclusions can be made through
examination of Table VII:
(1) Laboratory-to-laboratory comparison of equivalent mileage
and type vehicle test data shows that the Toyo Kogyo laboratory
consistently measures higher fuel economy. The 4000-mile certi-
fication data comparison shows Toyo Kogyo measurements to be on
the average 10.2% higher than the EPA measurement. Similarly,
the assembly line test and California Air Resources Board results
show Toyo Kogyo measurements to be on the average 8.9% higher than
the California Air Resources Board measurements for zero mileage
vehicles.
C2) Comparison of Toyo Kogyo 4000-mile certification data to
Toyo Kogyo assembly line test data shows no significant difference
in fuel economy Con the average) between zero-mile vehicles and
4000-mile vehicles. In fact, the newly built vehicles show slightly
better fuel economy. This is a surprising fact since engine
break-in would be expected to reduce engine/drivetrain internal
friction, thus causing improvements in fuel economy with break-in.
Apparently, such improvements do not occur for the Mazda rotary,
or, if they do, are offset by deterioration of tuned condition
by the time 4000 miles are accumulated, e.g., lead fouling of spark
plugs, which Mazda's owners' manual specifically warns against.
C3) The highest average fuel economy in Table VII, obtained by
Toyo Kogyo, was 12.5 mpg for the RX3 manual on the basis of assembly
line tests. The Toyo Kogyo 4000-mile certification test of the RX3
manual, which must represent the average calibration, measured a
fuel economy of 11.8 mpg. The lowest fuel economy obtained by
Toyo Kogyo, as reported in Table VII, was 11.2 mpg for the 4000-mile
test of the RX4 automatic. These values are significantly lower than
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TABLE VII
Summary of Other Rotary Fuel Economy Data
Vehicle
RX2 manual
Data Source
4000-mi. cert. (TK Japan)
4000-mi. cert. (EPA)
Zero-mile (TK Japan)
Zero-mile (California)
Fuel Economy (mpg)
12.1
10.6
not available
12.1
RX3 manual
4000-mi. cert. (TK Japan)
•4000-mi. cert. (EPA)
(2)
Zero-mile (TK Japan)^ J
Zero-mile (California)^1'
11.8
10.8
12.5
11.7
RX3 automatic
4000-mi. cert. (TK Japan)
4000-mi. cert. (EPA)
Zero-mile (TK Japan)
Zero-mile (California) C1)
12.1
11.0
12.2
11.0
RX4 manual
4000-mi. cert. (TK Japan)
4000-mi. cert. (EPA)
Zero-mile (TK Japan)
Zero-mile (Calif ornia) G-).
11.3
10.4
11.8
not available
RX4 automatic
4000-mi. cert. (TK Japan)
4000-mi. cert. (EPA)
Zero-mile (TK Japan)
Zero-mile (California)
11.2
10.3
not available
not available
(1) California Air Resources Board test on port-of-entry new vehicle
sample - average of three tests on 1 car.
(2) Assembly line tests by Toyo Kogyo in Japan - average of 22 cars tested
in January and February 1974.
(3) Assembly line tests by Toyo Kogyo in Japan - average of 15 cars tested
in January and February 1974.
(4) Assembly line tests by Toyo Kogyo in Japan - average of 50 cars tested
in January and February 1974.
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14
the values obtained by EPA in the current test program. This
suggests that the vehicles currently tested by EPA represented
the exceptional Mazda vehicle rather than an average vehicle.
In view of the above considerations only one plausible explanation
for the differences among test program results for the Ford and Mazda
vehicles remains. Since the test program was voluntary and to insure
equal treatment for all manufacturers, each manufacturer was encouraged
by EPA to deliver his test cars to EPA in the best possible state of
tune-up. It is reasonable to assume that Mazda, which requested the
conduct of the special test program, toofc full advantage of this
opportunity to present the fuel economy of its cars in the most
favorable light. A similar assumption can be made for the other
manufacturers* vehicles. This means that the state of tune of the
cars in this test program is likely to have been better than the state of
tune of the cars after 4000 miles in the certification program,
since tune-up or maintenance are not allowed at any point during
the 4000-mile mileage accumulation or prior to the 4000-mile certi-
fication test.
As regards the Vega vehicles, for which city-driving cold-start fuel
economy correlated closely with fuel economy data generated last year, this is
explainable by the fact that General Motors furnished for the special test
program exactly the same vehicles that it used to demonstrate compliance with
emission standards in last year's certification program. General Motors,
as a matter of policy, retains these vehicles; no other manufacturer furnished
exactly the same vehicles for the special test program.
Further, the Mazda certification vehicles accumulated mileage
with leaded fuel and were tested with leaded fuel. The Mazda vehicles
in this program were, at Mazda's request, permitted to be tested
with lead-sterile fuel, since the EPA engineers had concluded that
use of such fuel would make no difference to fuel economy if tune-up
was permissible prior to the test (i.e., change of plugs, etc.).
However, plug fouling with leaded fuels has been reported to be a
problem with rotary engines in the past, which is one reason why
the Mazda owner's manual contains a recommendation to use low lead
fuel. Mazda's 4000-mile 1974 certification vehicles had, in accordance
with their applicable regulations, accumulated their 4000 miles with
fully leaded gasoline.
In addition to the p'receeding comparisons, EPA analyzed the relative
fuel economy performance under cold start conditions and hot start
conditions for the test vehicles. To do this the fuel economy of each
vehicle was calculated for a hot start Federal City Driving Cycle
(sample bags 2 and 3 of the 1975 Federal Test Procedure) and compared
to the cold start Federal City Driving Cycle (sample bags 1 and 2 of
the 1975 Federal Test Procedure). Table VIII indicates the results of
that analysis.
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15
TABLE
Ratio of Hot Start Fuel Economy
to Cold Start Fuel Economy
Mazda RX2 1.09
Mazda RX3 1.12
Mazda RX4 1.11
Vega manual 1.09
Vega automatic 1.12
Gfemlin 1.10
Torino 1.11
SaaB 1.08
The data in Table VIII do not indicate that the rotary-powered
vehicle suffers or benefits any more from a cold start test than
does a typical reciprocating engine-powered vehicle.
Conclusions
1. The relationship of fuel economy results obtained by comparing
vehicle operation on the highway driving cycle to cold start vehicle
operation on the Federal City Driving Cycle is about the same for
the rotary engine Mazda as it is for conventional piston engine
vehicles, i.e., highway driving results in about 50% better fuel
economy than does cold start city driving.
2. On both the highway cycle and city cycle, the three Mazda
rotary vehicles and the Ford Torino, a significantly heavier
car, demonstrated similar fuel economy performance that is
considerably lower than that demonstrated by the other vehicles
in the test program that are in about the same weight class as
the Mazda.
3. No significant differences between the relative hot start and
cold start fuel economy were found by comparing the Mazda rotary
vehicles to the conventional reciprocating piston engine vehicles
testedriin the program.
4. The state of tune is an important consideration when testing
vehicles for fuel economy, because the state of tune significantly
affects the performance of vehicles. The differences in fuel economy
found between the Mazda and Ford Torino certification and special
fuel economy test vehicles was attributed to this effect as checks
of vehicular and test parameters indicated no other differences.
This difference between the Mazda and Ford Torino fuel economy results
could be anticipated and is acceptable as all manufacturers were
recommended to bring the test vehicles to the EPA lab in the best
possible state of tune.
-------
16
APPENDIX
Appendix A
Highway Cycle - Speed vs. Time
Appendix B
Comparison of Fuel Economy -
Gravimetric Analysis vs. Carbon
Balance
Appendix C
Emission and Fuel Economy Data
-------
APPENDIX A
***** EPA HIGHWAY FUEL ECONOMY DRIVING CYCLE *****
»»* SPEED (MPH) VS TIME (SEC) »**
Sec. MPH Sec. MPII Sec. MPH Sec. MPH Sec. MPH Sec. MPH Sec. MPH Sec. MPH
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
16
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
46
49
0.0
4.7
9.6
14.5
17.4
19.8
21.6
24.0
25.8
27.1
28.0
29.0
30.0
30.7
31.5
32.2
32.9
33.5
34.1
34.6
34.9
35.1
35.7
35.9
35.8
35.3
34.9
34.5
34.6
34.8 .
35.1
35.7
36.1
36.2
36.5
36.7
36.9
37.0
37.0
37.0
37.0
37.0
37.0
37.1
37.3
37.8
38.6
39.3
40.0
40.7
50
51
52
S3
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
.70
71
72
. 73
74
75
76
77
78
79
80
81
82
83
«fl4
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
41.4
42.2
42.9
43.5
44.0
44.3
44.5
44.8
44.9
45.0
45.1
45.4
45.7
46.0
46.3
46.5
46.8
46.9
47.0
47.1
47.2
47.3
47.2
47.1
47.0
46.9
46.9
46.9
47.0
47.1
47.1
47.2
47.1
47.0
46.9
46.5
46.3
46.2
46.3
46.5
46.9
47.1
47.4
47.7
48.0
48.2
48.5
48.8
49.1
49.2
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
49.1
49.1
49.0
49.0
49.1
49.2
49.3
49.4
49.5
49.5
49.5
49.4
49.1
48.9
48.6
48.4
48.1
47.7
47.4
47.3
47.5
47.8
47.9
48.0
47.9
47.9
47.9
48.0
48.0
48.0
47.9
47.3
46.0
43.3
41.2
39.5
39.2
39.0
39.0
39.1
39.5
40.1
41.0
42.0
43.1
43.7
44.1
44.3
44.4
44.6
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
44.7
44.9
45.2
45.7
45.9
46.3
46.8
46.9
47.0
47.1
47.6
47.9
48.0
48.0
47.9
47.8
47.3
46.7
46.2
45.9
45.7
45.5
45.4
45.3
45.0
44.0
43.1
42.2
41.5
41.5
42.1
42.9
43.5
43.9
43.6
43.3
43.0
43.1
43.4
43.9
44.3
44.6
44.9
44.8
44.4
43.9
43.4
43.2
43.2
43.1
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
43.0
43.0
43.1
43.4
43.9
44.0
43.5
42.6
41.5
40.7
40.0
40.0
40.3
41.0
42.0
42.7
43.1
43.2
43.4
43.9
44.3
44.7
45.1
45.4
45.8
46.5
46.9
47.2
47.4
47.3
47.3
47.2
47.2
47.2
47.1
47.0
47.0
46.9
46.8
46.9
47.0
47.2
47.5
47.9
48.0
48.0
48.0
48.0
48.0
48.1
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
48.2
48.2
48.1
48.6
48.9
49.1
49.1
49.1
49.1
49.1
49.0
48.9
48.2
47.7
47.5
47.2
46.7
46.2
46.0
45.8
45.6
45.4
45.2
45.0
44.7
44.5
44.2
43.5
42.8
42.0
40.1
38.6
37.5
35.8
34.7
34.0
33.3
32.5
31.7
30.6
29.6
28.8
28.4
28.6
29.5
31.4
33.4
35.6
37.5
39.1
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
• 331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
40.2
41.1
41.8
42.4
42.8
43.3
43.8
44.3
44.7
45.0
45.2
45.4
45.5
45.8
46.0
46.1
46.5
46.8
47.1
47.7
48.3
49.0
49.7
50.3
51.0
51.7
52.4
53.1
53.8
54.5
55.2
55.8
56.4
56.9
57.0
57.1
57.3
57.6
57.8
58.0
58.1
58.4
58.7
58.8
58.9
59.0
59.0
58.9
58.6
58.6
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
58.4
58.2
58.1
58.0
57.9
57.6
57.4
57.2
57.1
57.0
57.0
56.9
56.9
56.9
57.0
57.0
57.0
57.0
57.0
57.0
57.0
57.0
57.0
56.9
56.8
56.5
56.2
56.0
56.0
56.0
56.1
56.4
56.7
56.9
57.1
57.3
57.4
57.4
57.2
57.0
56.9
56.6
56.3
56.1
56.4
56.7
57.1
57.5
57.8
58.0
NOTE:
3 seconds and 2 seconds of idle are added at the beginning and end of the cycle respectively.
-------
APPENDIX A (con't.)
Sec. MPH
Sec. MPH
Sec. MPH
Sec. MPH
Sec. MPH
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
41ft
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
58.0
58.0
58.0
58.0
58.0
57.9
57.8
57.7
57.7
57.8
57.9
58.0
58.1
58.4
58.9
59.1
59.4
59.8
59.9
59.9
59.8
59.6
59.4
59.2
59.1
59.0
58.9
58.7
58.6
58.5
58.4
58.4
58.3
58.2
58.1
Sfl.O
57.9
57.9
57.9
57.9
57.9
58.0
58.1
58.1
58.2
58.2
58.2
58.1
58.0
58.0
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
4«5
486
487
488
489
490
491
492
493
494
495
496
497
498
499
58.0
58.0
58.0
58.0
57.9
57.9
58.0
58.1
58.1
58.2
58.3
58.3
58.3
58.2
58.1
58.0
57.8
57.5
57.1
57.0
56.6
56.1
56.0
55.8
55.5
55.2
55.1
55.0
54.9
54.9
54.9
54.9
54.9
54.9
55.0
55.0
55.0
55.0
55.0
55.0
55.1
55.1
55.0
54.9
54.9
54.8
54.7
54.6
54.4
54.3
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
54.3
54.2
54.1
54.1
54.1
54.0
54.0
54.0
54.0
54.0
54.0
54.0
54.0
54.1
54.2
54.5
54.8
54.9
55.0
55.1
55.2
55.2
55.3
55.4
55.5
55.6
55.7
55.8
55.9
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
56.0
55.9
55.9
55.9
55.8
55.6
55.4
55.2
550
551
552
553
554
555
556
557
558
559
560
561
562
563
- 564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
55.1
55.0
54.9
54.6
54.4
54.2
54.1
53.8
53.4
53.3
53.1
52.9
52.6
52.4
52.2
52.1
52.0
52.0
52.0
52.0
52.1
52.0
52.0
51.9
51.6
51.4
51.1
50.7
50.3
49.8
49.3
48.7
48.2
48.1
48.0
48.0
48.1
48.4
48.9
49.0
49.1
49.1
49.0
49.0
48.9
48.6
48.3
48.0
47.9
47.8
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
47.7
47.9
48.3
49.0
49.1
49.0
48.9
48.0
47*1
46.2
46.1
46.1
46.2
46.9
47.8
49.0
49.7
50.6
51.5
52.2
52.7
53.0
S3. 6
54.0
54.1
54.4
54.7
55.1
55.4
55.4
55.0
54.5
53.6
52.5
50.2
48.2
46.5
46.2
46.0
46.0
46.3
46.8
47.5
48.2
48.8
49.5
50.2
50.7
51.1
51.7
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
52.2
52.5
52.1
51.6
51.1
51.0
51.0
51.1
51.4
51.7
52.0
52.2
52.5
52.8
52.7
52.6
52.3
52.3
52.4
52.5
52.7
52.7
52.4
52.1
51.7
51.1
50.5
50.1
49.8
49.7
49.6
49.5
49.5
49.7
50.0
• 50.2
50.6
51.1
51.6
51.9
52.0
52.1
52.4
52.9
53.3
53.7
54.2
54.5
54.8
55.0
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
. 730
731
732
733
734
735
736
737
738
739
740
741
742
. 743
744
745
746
747
748
749
55. S
55.9
56.1
56.3
56.4
56.5
56.7
56.9
57.0
57.3
57.7
58.2
58.8
59.1
59.2
59.1
58.8
58.5
58.1
57.7
57.3
• 57.1
56.8
56.5
56.2
55.5
54.6
54.1
53.7
53.2
52.9
52.5
52.0
51.3
50.5
49.5
48.5
47.6
46.8
45.6
44.2
42.5
40.2
36.7
32.0
. 28.0
24.5
21.5
19.5
17.4
750
751
752
753
754
755
756
757
758
15.1
12.4
9.7
7.0
5.0
3.3
2.0
0.7
0.0
oo
-------
19
Appendix
B
Fuel Weigh vs. Carbon Balance
Fuel Economy
Vehicle
RX2
RX2
RX2
RX3
RX3
RX3
RX4
RX4
RX4
Configuration
without AC
with AC
with AC'
without AC
with AC
with AC
without AC
with AC
with AC
Fuel
•72 FTP
12.8
12.4
12.3
12.3
12.3
12.5
11.7
12.5
12.6
Weigh
Highway
20.8
21.4
20.6
19.1
18.5
17.5
20.1
20.3
20.1
Carbon
•72 FTP
13.8
13.2
13.6
13.7
13.3
13.2
12.8
12.6
12.4
Balance
Highway
21.4
21.3
21.0
19.7
19.0
19.0
20.5
20.8
20.2
Vega Auto with AC
17.8
27.0
18.6
27.6
-------
APPENDIX C
Emission and Fuel Economy Data
'75 FTP
Test
9-329
9-330
9-331
9-344
9-350
21-18
21-19
21-20
21-21
21-22
21-23
21-24
21-25
21-26
21-27
21-28
21-29
V|l-30
fi-3i
21-32
21-33
21-35
21-37
21-38
21-40
21-42
21-43
21-45
Date
3-12
3-12
3-12
3-14
3-15
3-15
3-05
3-06
3-06
3-06
3-06
3-06
3-07
3-07
3-»07
3-07
3-07
3-08
3-08
3-08
3-08
3-09
3-09
3-09
3-10
3-13
3-13
3-13
Vehicle
99 EMS
Gremlin
Torino
99 EMS
99 EMS
Gremlin
Torino
Gremlin
Torino
RX3
RX2
RX4
Vega
Vega
RX4
RX2
RX3
99 EMS
Torino
RX4
RX2
99 EMS
RX3
Vega
Vega
Gremlin
Vega
99 EMS
Trns.
M4
M3
A3
M4
M4
M3
A3
M3
A3
A3
M4
M4
A3
M4
M4
M4
A3
M4
A3
M4
M4
M4
A3
A3
M4
M3
M4
M4
Conf .
w/AC
w/AC
w/AC
w/AC
w/AC
wo/AC
wo/AC
wo/AC
wo/AC
wo/AC
wo/AC
wo/AC
w/AC
w/AC
w/AC
w/AC
w/AC
wo/AC
w/AC
w/AC
w/AC
wo/AC
w/AC
w/AC
w/AC
w/AC
w/AC
w/AC
HC
1.73
1.47
2.41
1.77
1.92
1.52
2.53
1.55
2.50
1.97
1.83
1.97
1.48
1.89
2.25
1.61
1.76
1.63
2.25
2.07
1.77
1.71
1.56
1.58
2.39
1.41
2.38
1.54
CO
25.35
21.50
15.40
20.24
21.45
20.84
18.86
19.92
17.58
17.37
14.73
13.13
20.25
20.06
10.67
13.04
15.57
24.30
15.70
10.63
12.30
24.99
15.18
21.86
16.51
17.62
15.89
22.87
co2
407.20
448.61
643.67
376.90
376.91
427.33
649.36
431.75
664.58
579.94
604.25
646.95
407.56
458.52
659.17
622.78
595.31
410.74
641.02
651.05
601.56
409.25
599.14
411.74
443.09
439.70
447.22
416.51
NOx
1.39
2.15
3.17
1.79
1.85
1.84
3.06
1.74
3.19
1.01
1.03
1.07
2.53
1.85
1.18
. 1.00
1.06
1.30
2.92
1.19
1.01
1.37
1.12
2.64
1.77
1.94
1.81
1.53
MPG
19.6
18.2
13.1
21.4
21.3
19.1
12.9
19.0
12.7
14.5
14.0
13.2
20.0
17.9
13.0
13.7
14.2
19.5
13.2
13.2
14.2
19.5
14.1
19.7
18.6
18.8
18.5
19.4
HC
2.03
. 1.60
2.64
2.00
2.23
1.84
2.84
1.72
2.74
2.02
2.12
2.07
1.67
2.23
2.33
2.01
1.93
2.02
2.52
2.28
2.12
2.05
1.81
1.96
2.51
1.51
2.48
1.84
CO
29.67
25.59
22.48
24.11
26.07
26.45
28.58
24.51
25.26
16.24
15.12
12.89
26.70
26.69
9.27
13.91,
15.10
29.28
22.95
9.86
13.19
29.72
15.16
28.72
21.52
22.30
21.21
27.64
'72- '74 FTP
C02
423.42
464.78
670.37
385.38
387.13
435.89
668.47
441.49
682.66
614.52
612.10
668.82
427.90
462.88
682.13
645.99
635.85
423.79
663.00
691.39
624.84
427.50
640.39
425.89
442.97
453.09
460.24
431.68
NOx
1.36
2.24
3.16
1.74
1.79
1.88
2.98
1.79
3.06
1.06
1.08
1.04
2.67
1.86
1.18
0.99
1.12
1.25
2.87
1,18
1.02
1.34
1.18
2.69
1.78
2.04
1.85
1.49
MPG
18.6
17.4
12.4
20.7
20.4
18.4
12.3
18.3
- 12.1
13.7
13.8
12.8
18.7
17.3
12.6
13.2
13.3
18.6
12.5
12.4
13.6
18.5
13.2
18.6
18.3
18.0
17.7
18.4
HC
0.34
0.49
1.62
0.54
0.56
0.48
1.62
0.51
1.68
0.12
0.09
0.25
0.76
0.63
0.25
0.09
0.16
0.30
1.27
0.36
0.08
0.34
0.11
0.82
0.71
0.47
0.70
0.28
CO
5.81
2.75
6.48
5.46
5.85
2.25
7.95
2.86
7.52
2.16
1.96
4.08
2.96
3.10
5.69
1.94
2.31
5.06
5.16
6.13
1.10
6.00
2.15
3.47
2.63
5.34
2.60
4.66
Highway
C02
317.27
319.08
466.85
279.94
279.55
309.80
452.87
312.77
471.27
446.99
411.87
426.28
312.18
284.78
417.09
412.30
462.20
307.96
396.57
427.44
419.95
300.58
463.60
312.95
284.91
318.54
280.35
308.96
Cycle
NOx
1.98
3.49
4.63
2.66
2.51
2.76
4.53
2.81
4.64
0.91
1.05
1.08
2.89
2.62
1.18
1.07
1.03
1.80
3.84
1.30
1.10
1.74
1.05
3.08
2.64
3.31
2.59
2.09
MPG
27.1
27.3
18.4
30.6
30.5
28.2
18.9
27.8
18.2
19.7
21.4
20.5
27.8
30.4
20.8
21.3
19.0
28.0
21.7
20.2
21.0
28.5
19.0
27.6
30.5
27.0
31.0
28.0
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