An Evaluation- of Two Toyo Kogyo
1975 Prototypes With Rotary Engines
February 1973
Thomas C. Austin
Test & Evaluation Branch
Division of Emission Control Technology
Mobile Source Pollution Control Program
Office of Air and Water Programs
Environmental Protection Agency
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Background
Of all automobile manufacturer's who testified at the April
1972 Suspension Hearings, Toyo Kogyo was the most optimistic
about the possibility of meeting the 1975 Federal exhaust
emission standards. Toyo Kogyo had achieved the levels re-
quired for 1975, at low mileage, and had initiated 50,000-
mile durability tests to prove their capability to remain
below the required levels. This past October, when the
manufacturers submitted their annual status reports on
their progress toward meeting the 1975 standards, EPA learned
that Toyo Kogyo had completed 50,000 miles of durability on
one of their 1975 prototypes, a rotary engined Mazda RX3.
Emission levels were still below the 1975 requirements. A
letter was written to Toyo Kogyo offering confirmatory testing
in EPA1s Ann Arbor laboratory. The offer was accepted and
two vehicles, the RX3, which had completed 50,000 miles,and
and RX4, with 4000 miles accumulated, were delivered for
testing late in January.
Vehicles.Tested
Both vehicles supplied by Toyo Kogyo were equipped with rotary
engines using thermal reactors for the control of unburned
hydrocarbons (HC) and carbon monoxide (CO). No control systems
(such as exhaust gas recirculation) for the control of oxides
of nitrogen (NOx) were required to achieve the 1975 levels
because of the light weight of the Mazda vehicles (2350# and 2600#
for the RX3 and RX4, respectively) and the inherently lower
NOx emissions of rotary engines.
*
The RX3 vehicle was the smaller of the two. Toyo Kogyo
estimated that this vehicle would be in the 2750 pound inertia
weight* class for 1975. The two rotor engine installed in this
vehicle, had a swept volume of 70 cubic inches. The vehicle
was equipped with a four speed manual transmission. Before the
EPA testing, the RX3 had completed a 50,000-mile AMA durability
run. Toyo Kogyo's data indicated that the vehicle could
successfully certify for 1975.
The RX4 vehicle will be in the 3000 pound inertia weight class
for 1975. The two rotor engine in this vehicle had a swept
volume of 80 cubic inches. This vehicle was equipped with
an automatic transmission. Four thousand miles had been accumu-
lated on the vehicle, before the EPA testing.
*Note: inertia weight = curb weight + 300 pounds, rounded to
the nearest 250 pounds.
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Both vehicles used air-cooled thermal reactors witti "modulated"
air injection. Air injection rate is kept proportional to
engine speed and load by a special control valve. Mosjt manu-
facturers use an air injection system which does not match the
injection rate with the load of the engine. A non-proportional
system can cause a loss of emission control at light loads due
to an excess of injected air. On the Toyo Kogyo system, air
which is not injected into the core of the reactor is directed
into an annulus surrounding the reactor for cooling. Above
speeds of about 65 mph, all of the air is injected into the
annulus for cooling and: none'is injected into the reactor core.
Data reported by Toyo Kogyo indicate that a substantial loss
of HC and CO control occurs during this condition.
Manual chokes were also used on both vehicles. Toyo Kogyo
representatives indicated, however, that automatic choke-s
are scheduled for production in 1975.
Toyo Kogyo had operated these vehicles on a "low lead" fuel
containing .36 grams per gallon of Tetra-ethyl lead and .013%
sulfur (by weight). This fuel had a Research Octane Number
of 91 and contained 6.1% Olefins, 31.3% aromatics, and 62.6%
paraffins. The EPA testing was done on "Indolene Clear" which
contains about .05 grams per gallon lead. The Toyo Kogyo re-
presentatives who accompanied the two vehicles reported that
their engines were not sensitive to lead level. Lead is not
required for octane improvements or lubrication, neither is
"lead free" fuel required to prevent system deterioration.
Test Program
Four different types of emission tests were performed during
the EPA evaluation:
*
1. 1975 Federal Test Procedure (FTP) at the standard
test weights (2750# for RX3, 3000* for RX4).
2. Hot start 1972, 2-bag FTP's on the RX4 with a richer
carburetor.
3. 1975 FTP on the RX3 at an elevated (3500#) inertia weight.
4. Steady state tests on both vehicles at idle, 15,30,45,
and 60 mph.
Gaseous emissions (HC, CO, NOx, and C02) and fuel economy were
determined during each type of test. A description of the Federal
Test Procedure for exhaust emissions is enclosed (Attachment I).
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Test Results
Results are summarized in Tables I, II, III, and IV. Table I
lists the results on the 1975 FTP for both vehicles at their
standard test weights. Toyo Kogyo's data from their last
series of tests run on these cars is also included for com-
parison. Every test on each vehicle was below the levels
required for 1975. The 50,000-mile RX3 averaged approximately
one-half of the required levels for HC and CO and one-third
of the required NOx level.
One test on the RX3 (not reported in Table I) had to be voided
because the EPA driver did not use the correct choking procedure.
The Toyo Kogyo rotarys are very sensitive to the choking pro-
cedure used. Tests were conducted using continuous analysis
of the exhaust to see the effect of choking procedure on the
hot restart. With no choke the HC levels remained high for a
much longer period of time, levels above 100 ppm propane (dilute)
were recorded one minute after start-up. With the choke, however,
the HC levels stayed below 100 ppm after only 15 seconds.
Fortunatly, since Toyo Kogyo is planning to equip production
vehicles, with automatic chokes, this critical operation will
not be left up to the driver.
The fuel economy data appearing on Table I was calculated
using a carbon balance technique. ' The 12.36 and 11.92 mpg,
recorded for the RX3 and RX4, respectively, indicates that
no loss in fuel economy has occurred in meeting the 1975
levels. 1973 rotary Mazdas in the same weight class had
almost identical fuel economy. It should be noted, however,
that Mazda rotarys seem to get poorer fuel economy than vehicles
with conventional engines. EPA tests indicate that the average
fuel economy for Mazda rotarys is 30% worse than the average
of all vehicles in their respective weight classes.
Table II shows the emissions during steady state operation for
both vehicles. The extremely low HC emission level at each
point is a characteristic of vehicles with emissions controlled
by thermal reactors. CO emissions are also quite low at each
point. NOx emissions continually increase as speed increases
for both vehicles. Calculated fuel economy was better at
every steady state cruise than during the LA4 (Federal) driving
cycle. This is to be expected since fuel economy is adversely
affected by the stop and go type driving which is represented
by the LA4 cycle. Testing at 65 mph and above was not possible
due to the limitation of the particular chassis dynamometers
used, but it should be noted that a loss of HC and CO emission
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control is expected at such speeds when the air injection does
not enter the reactor core. Toyo Kogyo representatives were
unable to provide any data which indicated that vehicle or engine
speeds were the most meaningful parameters to triager the air
injection by-pass valve. The possibility of changing the
activating signal to load or reactor temperature was discussed.
The results of the testing of the RX3 vehicle at elevated inertia
weight appears in Table III. Since Toyo Kogyo vehicles have
relatively high power to weight ratios, it is not unrealistic
to assume that the engine from the 2750# test weight class RX3
would do an acceptable job of propelling a vehicle in the 3500#
test weight class. Comparing the results of the test at the
3500# weight with the average of the tests at the 2750# weight,
it can be seen that very little emission control was sacrificed.
The fuel economy compared to the average 1973 vehicle in the
3500# class indicates a 20% penalty. This is less of a penalty
than was indicated by comparing the results at 2750# with the
average 1973 vehicle in the 2750# class, indicating that the
rotary Mazda's fuel economy problems are due in part to the
high power to weight ratios of Mazda vehicles. It should be
noted that the Toyo Kogyo personnel made a modification to the
carburetor on the RX3 prior to the testing at 3500#. This
modification either delayed or eliminated the opening of the
secondaries in the carburetor. The attached driver's trace
(Figure 1.) indicates that the vehicle could not quite keep
up with the hardest acceleration of the cycle with the modified
carburetor.
In Table IV appears the results of the hot start testing of
the RX4 with the richer carburetor. In this configuration
fuel economy was somewhat adversely affected. NOx levels,
however, were only 17% higher than the requirement for 1976
of .40 grams per mile (gpm). HC and CO levels should not be
directly compared to the 1975 or 1976 standards since these
tests were "hot" rather than "cold" start. The Toyo Kogyo
representatives indicated that the HC emissions would probably
be below the 1975 and 1976 requirement during a cold start
test, but CO emissions would be a problem. It should be noted
that the .47 gpm NOx level was achieved without EGR. Toyo
Kogyo representatives indicated that EGR, a common control
technique for reciprocating engines, also has a beneficial
effect on NOx emissions from the rotary engine.
Although not reported in the tables, the RX4 vehicle was also
tested for aldehyde emissions using a wet chemical technique.
The formaldehyde level of the exhaust was too low to be
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accurateiy determined by the procedure used. The formaldehyde
level is well below the levels of uncontrolled conventional
engines.
The driveability of the RX4 vehicle was evaluated on the road
and there were no problems encountered. The engine was very
responsive and there were no hints of hesitation or stumbling.
Acceleration was very good, typical of current Mazdas which
are not known for having any trouble keeping up with traffic.
Conclusions
1. Toyo Kogyo appears to have successfully demonstrated the
ability to certify for 1975.
2. The two 1975 prototypes did not demonstrate any fuel economy
penalty compared to current Mazda vehicles. There were no drive-
ability problems encountered.
3. The Toyo Kogyo rotary engine and control system will also
achieve the 1975 levels at higher test weights than required
for Mazda vehicles.
4. There does not appear to be a formaldehyde emission problem
associated with the rotary engine/thermal reactor concept.
Additional NOx control will be necessary to reach the 1976
"levels, but it should be noted that the vehicles tested did
not use EGR.
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TABLE I
Toyo Kogyo 1975 Prototypes With Rotary Engines
1975 Federal Test Procedure
(emission data in grams per mile)
Vehicle
50,000
mile car
MGCIII
Nn 1
LV\J m JL
RX3,
4-speed
2750#
Inertia
Lab
EPA
EPA
EPA
EPA
Toyo
Kogyo
Toyo
Kogyo
Toyo
Kogyo
Toyo
Kogyo
Test Number
16-0205
16-0209
16-0227
AVERAGE
1-1
1-2
1-3
AVERAGE
HC
.25
.12
.25
.21
.316
.326
.369
.337
CO
2.09
1.53
1.76
1.79
2.40
2.32
2.66
2.46
NOx
1.04
.98
.94
.99
.96
.97
.95
.96
MPG
12.38
12.64
12.07
12.36
___
— — —
...
^ •» ^
4,000
mile car
MCCIV
No. 1
RX4
automatic
3000#
Inertia
EPA
EPA
EPA
EPA
EPA
Toyo
Kogyo
Toyo
Kogyo
Toyo
Kogyo
Toyo
Kogyo
16-0206
16-0210
16-0213
16-0218
AVERAGE
2-1
2-2
2-3
AVERAGE
.29
.28
.34
.34
.31
.204
.258
.240
.234
2.45
2.13
2.52
2.88
2.50
2.10
1.99
2.20
2.10
1.55
1.48
1.37
1.45
1.46
1.33
1.26
1.30
1.30
11.87
11.76
12.37
11.67
11.92
— — —
— —
•» *• «
"""
1975 Federal Standards
.41 3.40 3.10
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TABLE II
Toyo Kogyo 1975 Prototypes With Rotary Engines
Steady State Emissions and Fuel Consumption
(idle mode data in grams per minute, all other modes
in grams per mile)
Vehicle
Mode
HC
CO
NOx
MPG
50 .000-mile
car,MCCIII
No. 1, RX3,
4-speed,
2750 #
inertia
40,000-mile
car,MCCIV,
No.l, RX4,
automatic,
AOGOtt
^Cnertia
idle
15 mph
' 30 mph
45 mph
60 mph
idle
15 mph
30 mph
45 mph
60 mph
0.00
.02
.01
0.00
0.00
.002
0.00
.01 .
.01
.01
.362
.44
.31
.22
.22
.016
.02
.21
.17
.20
.016
.26
.35
.40
.93
.026
.19
.25
.77
1.64
*
13.8
16.7
21.2
20.3
**
14.3
16.8
16.8
17.8
*idle fuel consumption
**idle fuel consumption
.633 gallons per hour
.711 gallons per hour
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' TABLE III
Toyo Kogyo RX3 Rotary @ 3500# Inertia
(emission data in grams per mile)
RX3 with
modified
secondaries
Test Number
16-0229
HC
.33
CO
1.88
NOx
1.17
MPG
11.67
1975 Federal Standards .41 3.40 3.10
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TABLE IV
Hot Start 1972 FTP'S of RX4 With
Richer Carburetion
(emission data in grams per mile)
Vehicle Test Number HC CO NOx MPG
RX4 w/richer
carburetion
16-0225
16-0228
.04
.09
3.56
7.28
.48
.46
11.38
11.33
AVERAGE .07 5.42 .47 11.36
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Driver's Trace tor RX3
at Elevated (3500#) Inertia
Figure 1.
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FEDERAL EMISSION TESTING PROCEDURES
FOR LIGHT DUTY VEHICLES
The Federal procedures for emission testing of light
duty vehicles involves operating the vehicle on a chassis
dynamometer to simulate a 7.5 mile (1972 procedure) or
11.1 mile (1975 procedure) drive through an urban area.
The cycle is primarily made up of stop and go-driving and
includes some operation at speeds up to 57 mph. The
average vehicle speed is approximately 20 mph. Both the
1972 and 1975 procedures capture the emissions generated
during a "cold start" (12-hour soak @ 68°F to 86°F before
start-up). The 1975 procedure also includes a "hot start"
after a ten minute shut-down following the first 7.5 miles
of driving. ' .
Vehicle exhaust is drawn through a constant volume
sampler (CVS) during the test. The CVS dilutes the vehicle's
exhaust to a known constant volume with make up air. A
continuous sample of the diluted exhaust is pumped into
sample bags during the test. -~
Analysis of the diluted exhaust collected in the sample
bags is used to determine the mass of vehicle emissions per
mile of operation (grams per mile). A flame ionization de-
tector (FID), is used to measure unburned hydrocarbon (HC)
concentrations. Non-dispersive, infrared (NDIR) analyzers are
used to measure carbon monoxide (CO) and carbon dioxide .'(C02) .
A chemiluminescence (CL) analyzer is used to determine oxides
of nitrogen (NOx) levels.
»
These procedures are used for all motor vehicles designed
primarily for transportation of property and rated at. 6,000
pounds GVW or less, or designed primarily for transportation of
persons and having a capacity of twelve persons or less. Each
new light duty vehicle sold in the United States in model years
1973 and 1974 must emit no more than 3.4 gpm HC, 39. gpm CO
and 3.0 gpm NOx when using the 1972 procedure. In 1975 the.
standards will change to .41 gpm HC. 3.4 gpm CO and 3.1 gpm NOx
using the 1975 procedure. In 1976 the standards will be .41
gpm HC, 3.4 gpm CO and .4 gpm NOx using the 1975 procedure.
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