EPA-AA-TAEB 75-16
A Second Evaluation of the
Yamaha Lean Combustion Engine System
February 1975
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Air and Waste Management
Environmental Protection Agency
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Background
The Environmental Protection Agency receives information about
many systems which appear to offer potential for emission reduction or
fuel economy improvement compared to conventional engines and vehicles.
EPA's Emission Control Technology Division is interested in evaluating
all such systems, because of the obvious benefits to the Nation from
the identification of systems that can reduce emissions, improve
economy, or both. EPA invites developers of such systems to provide
to the EPA complete technical data on the system's principle of opera-
tion, together with available test data on the system. In those
cases in which review by EPA technical staff suggests that the data
available show promise, attempts are made to schedule tests at the
EPA Emissions Laboratory at Ann Arbor, Michigan. The results of all
such test projects are set forth in a series of Technology Assessment
and Evaluation Reports, of which this report is one.
The conclusions drawn from the EPA evaluation tests are necessarily
of limited applicability. A complete evaluation of the effectiveness
of an emission control system in achieving performance improvements
on the many different types of vehicles that are in actual use requires
a much larger sample of test vehicles than is economically feasible
in the evaluation test projects conducted by EPA. For promising
systems it is necessary that more extensive test programs be carried
out.
The conclusions from the EPA evaluation test can be considered
to be quantitatively valid only for the specific test car used,
however, it is reasonable to extrapolate the results from the EPA
test to other types of vehicles in a directional or qualitative manner,
i.e., to suggest that similar results are likely to be achieved on
other types of vehicles.
The Emission Control Technology Division (.ECTD) of the Office
of Mobile Source Air Pollution Control had previously tested the Yamaha
Lean Combustion System (JLCS) in August 1974 (ECTD report 75-8) . The
vehicles tested had very low pollutant emissions but had poor fuel
economy. ECTD agreed to perform additional confirmatory tests if
Yamaha was able to make significant fuel economy improvements and still
achieve low emissions.
Subsequent to the EPA tests Yamaha improved fuel economy and
built a second generation prototype system. ECTD was contacted by
representatives of Yamaha International Company in January 1975 about
confirmatory testing of the prototype second generation system.
Consistent with ECTD's continuing interest in the evaluation of advanced
automotive emission control technology, a test program was conducted
by the Technology Assessment and Evaluation Branch.
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Vehicle Description
The vehicle tested was a Toyota Corolla with a LCS four cylinder
1588 cubic centimeter dual overhead cam engine and a 5-speed manual
transmission. The car is described in detail in the Vehicle Description
Table on the following page.
The Yamaha LCS is a lean mixture combustion system. . The carburetor,
intake manifold, and cylinder head incorporate a number of proprietary
modifications to improve the quality of the fuel-air mixture and to
improve the distribution of the mixture. This allows the engine to
achieve the advantages of low hydrocarbon, carbon monoxide, and nitrogen
oxide emissions resultant from lean operation (air fuel ratios between
17:1 and 18:1). The exhaust manifold was modified to act as a low
temperature thermal reactor and thereby promote HC and CO oxidation
reactions in the exhaust. Yamaha was able to attain low pollutant
lean combustion without the need for fuel injection, dual intake
passages, special valves or an auxiliary combustion chamber. The
company's lean combustion technique permits its engine to achieve
low pollutant emissions without exhaust gas recirculation (EGR),
air injection, or a catalytic converter. (The vehicle tested
previously used EGR.)
Yamaha claims its system requires no significant modifications
to the basic engine design and causes less than 5% power loss. No
emission deterioration data has yet been established, however in EPA
judgement the system uses low deterioration components. Although the
DOHC engine used in the test vehicle is not sold in the U.S., Yamaha
believes its system is applicable to most engines. Yamaha considers its
test vehicle to be a stage of development in a continuing effort.
EPA has insufficient technical data to fully evaluate the above
claims associated with the Yamaha system and therefore cannot confirm
them.
Test Procedure
Exhaust emissions tests were conducted according to the 1975
Federal Test Procedure ('75 FTP), described in the Federal Register
of November 15, 1972 except that no evaporative emissions tests were
conducted. Additional tests included the EPA Highway Cycle and
steady state emissions test. All tests were conducted using an
inertia weight of 2250 pounds (1020 kg) with a road load setting
of 8.8 horsepower (6.6 kW) at 50 miles per hour (80.5 km/hr).
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1974 Toyota Corolla
Emission Control system - Yamaha LCS
Engine
type ' cycle, DOHC, 4-cyl., inline, Otto Cycle
bore x stroke 3.35 x 2.76 in./85.0 x 70.0 mm
displacement 96.9 CID/1558 cc
compression ratio 9.0:1
maximum power @ rpm in excess of 76 bhp/56.7 kW @ 3800 RPM
fuel metering 2 barrel carburetor
fuel requirement 91 RON unleaded
Drive Train
transmission type 5 speed manual (3.587, 2.022, 1.384, 1.000,
final drive ratio 4.30:1 .861)
Chassis
type unitized body/frame, front engine, rear
tire size 165 SR 14 wheel drive
curb weight 2080 pounds
inertia weight 2250 pounds
passenger capacity 4
Emission Control System
basic type lean combustion system
exhaust manifold low temperature thermal reactor
durability accumulated on system . . 3400 miles/5500 km
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Test Results
Exhaust emissions data, summarized below, showed that the Yamaha
test car using their LCS achieved the levels of 1977 Federal Emission
standards of .41 gm/mi HC, 3.4 gm/mi CO and 2.0 gm/iai NOx at low
mileage. It also met the proposed 1978 California standards of .41
gm/mi HC, 9.0 gm/mi CO, and 1.5 gm/mi NOx.
• 75 FTP Composite Mass Emissions
grams per mile
(grams per kilometre)
Fuel Economy
HC CO NOx (Fuel Consumption)
Average of 3 tests .34 3.00 1.44 23.6 miles/gal
(.21) (1.86) (.89) (10.0 litres/100 km)
On the EPA Highway Cycle the results were:
EPA Highway Cycle Mass Emissions
Average of 4 tests .01 .37 1.40 36.3 miles/gal
(.01) (.23) (.87) (6.5 litres/100 km)
Steady state fuel economy results were:
Speed Fuel Economy (Fuel Consumption)
mph (km/hr) Gear miles/gallon litres/100 km
15 (24.1) 2nd 23.0 (10.2)
30 (48.3) 3rd 32.4 ( 7.3)
45 (72.4) 4th 36.5 ( 6.4)
45 (72.4) 5th 40.2 ( 5.9)
60 (96.6) 5th 34.4 ( 6.8)
In contrast to the previous vehicles, this test vehicle had no
driveability problems. Detailed emission test results are given in
tables at the end of this report.
Comparison of the test vehicle's fuel economy with certification
results for 1975 vehicles of the same inertia weight (2250 pounds)
showed that there was no fuel penalty. But several of these
certification vehicles also met the 1977 emission standards.
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Fuel Economy Comparison
1975 Certification Tests of 49 State Vehicles
'75 FTP
Fuel Economy miles/gal Average-13 Tests Yamaha LCS
(Fuel Consumption litres/100 km) of 49 State Vehicles
20.0 to 27.4 23.6 23.6
(11.8 to 8.6) (10.0) (10.0)
EPA Highway Cycle
30.4 to 41.1 36.2 36.3
(7.7 to 5.7) (6.5) (6.5)
1975 Certification Test of California Vehicles
'75 FTP
Fuel Economy miles/gal Average-6 Tests Yamaha LCS
(Fuel Consumption litres/100 km) of California Vehicle
20.6 to 27.4 23.7 23.6
(11.4 to 8.6) (9.9) (10.0)
EPA Highway Cycle
30.5 to 41.1 36.8 36.3
(7.7 to 5.7) (6.4) (6.5)
Conclusions
The Yamaha vehicle met the 1977 Federal Emission levels and
was able to achieve this with a minimum of external engine emission
control devices. There were no fuel economy penalties for the car
when compared to current (1975 model) vehicles.
Yamaha is continuing development of its system. Presently the
Company is testing larger vehicles (subcompact American car and 4000
pound inertia weight car). EPA has agreed to perform confirmatory
testing of these vehicles if their emissions and fuel economy warrant it,
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TABLE la
'75 FTP Mass Emissions
grams per mile
Bag 1 Cold Transient FUEL ECONOMY Bag 2 Hot Stabilized FUEL ECONOMY Bag 3 Hot Transient FUEL ECONOMY
TEST NUMBER
21-7504
21-7540
21-7547*
21-7585
HC CO C02
.86 7.04 389
.79 6.50 377
.74 6.16 379
TEST
NOx
2.15
2.28
2.11
NUMBER
21-7504
21-7540
21-7585
MPG HC CO
C02 NOx
22.1 .13 i.58 402
22.8 .12 1.68 391
.16 1.73 401
22.7 .14 1.57 389
TABLE Ib
1 75 FTP Composite Mass
grams per mile
HC CO
.39
.31
.33
3.29
2.87
2.85
MPG
99 21.9
99 22.5
94 22.0
96 22.7
Emissions
C02 NOx
378
367
365
1.
1.
1.
45
48
40
HC CO C02 NOx
.54 3.74 324 1.80
.30 2.39 316 1.81
.40 3.25 313 1.70
.37 2.80 309 1.72
COMPOSITE FUEL
ECONOMY MPG
23.1
23.8
23.9
MPG
26.8
27.7
27.8
28.2
* Void; not used in averages.
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TABLE II
EPA Highway Cycle Mass Emissions
grains per mile
FUEL ECONOMY
TEST NUMBER HC
21-7504 .01
21-7540 .02
21-7547 .01
21-7585 .01
CO
.35
.42
.36
.35
TABLE
C02 NOx
251 1.43
246 1.48
244 1.36
236 1.34
III
MPG
35.3
36.0
36.3
37.5
Steady State Mass Emissions
grams per mile
SPEED
TEST NUMBER MPH GEAR
0 (idle) N
15 2
30 3
45 4
45 5
60 5
HC
.02*
.03
.00
.01
.00
.01
CO C02 NOx
.34* 98* .02*
1.22 383 .28
.33 273 .48
.25 242 .96
.29 220 .78
.24 258 2.13
FUEL ECONOMY
MPG
N/A
23.0
32.4
36.5
40.2
34.4
* Idle emission values are in grams per minute.
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