75-8 AB
Evaluation of the Yamaha Lean Combustion
Engine System - Emissions
and Fuel Economy
September 1974
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 'devices for which emission reduction or fuel economy improvement
claims'are made. In some cases, both claims are made for a single
device. In most cases, these devices are being recommended or pro-
moted for retrofit to existing vehicles although some represent
advanced systems for meeting future -standards.
The EPA .is interested in evaluating the validity of the claims
for all such devices, because 'of the obvious benefits to the Nation of
identifying devices that live up to their claims. For that reason
the EPA invites proponents of such devices' to provide to the EPA
complete technical'data on the device's principle of operation,
together with' test data on the device made by independent laboratories.
In those cases in-which review by EPA technical staff suggests that
the'data submitted holds promise of confirming the claiins-made for
the device', confirmatory tests1 of the device''are scheduled at the
EPA'Emissions Laboratory at :Ann Arbor, Michigan. The results of such
confirmatory 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 confirmatory tests are
necessarily of limited applicability. A complete evaluation of the
effectiveness of an emission control-system in achieving its claimed
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 confirmatory test projects conducted
by-EPA. _!/ For'promising devices it is necessary that more extensive
test programs be carried out.
The conclusions from the EPA confirmatory tests .can be considered
to be quantitatively valid only for the specific type of vehicle
used in the EPA confirmatory test program. Although it is reasonable
' to extrapolate the results from the EPA confirmatory'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', tests of the device' on- such other vehicles would be
required' to reliably quantify results on other types of vehicles.
I/ See Federal Register 38 FR 11334, 3/27/74, for a description
of the test protocols proposed for definitive evaluations of the
'"' ; effectiveness' of retrofit devices.
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In summary, a device that.lives up to its claims in the EPA
confirmatory test must be further tested according to protocols
described in footnote I/, to quantify its beneficial effects on a
broad range of vehicles. A device which when tested by EPA does not
meet the claimed .results would not appear to be a worthwhile candidate
for such further testing from the standpoint of the likelihood of
ultimately validating the claims made. However, a definitive quantita-
tive evaluation of its effectiveness on a broad range of vehicle
types would equally require further tests in accordance w^th footnote I/.
During a June visit to the Japanese motorcycle industry, EPA
personnel were.informed by Yamaha of their developments in automotive
emissions control technology. Interest in the automotive emissions
control area stems from the little known fact that Yamaha is a
manufacturer and supplier of automotive engines to the automotive
industry. Yamaha claimed that their demonstration vehicle could
meet the statutory HC and CO standards and 2,0 gm/mi NOx (1.24 gm/km)
with a fuel penalty of about 7%. To confirm their results, Yamaha
requested confirmatory tests at EPA on two vehicles in early stages
of development.
Provided that the confirmatory testing proved successful, Yamaha
also proposed that they build second generation prototypes for
future EPA testing. (Subsequent to this test program, Yamaha has
: already provided EPA with data showing fuel economy improvement.
On the basis of this data EPA and Yamaha have tentatively agreed to
a confirmatory test program on two additional prototypes in the
near future.)
Vehicles tested
,The Yamaha Lean Combustion Engine System is a lean mixture
combustion system. The carburetor and, cylinder head incorporate a
number of proprietary modifications to facilitate lean operation (air-
fuel ratios between 17:1 and 18:1). The exhaust manifold was insulated
to elevate temperature, and thereby promote HC and CO oxidation
reactions in the exhaust. EGR is also employed. These modifications
were incorporated in engines installed in a Toyota Corolla and
Toyota Celica.
Yamaha considers their system to be a low cost, readily adaptable
modification to existing engine systems during vehicle manufacturing.
Presently, EPA has insufficient technical data to evaluate the
additional costs associated with the Yamaha system and therefore
cannot confirm this claim.
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Vehicle Specifications
Yamaha Corolla
Yamaha Celica
Engine Type
Transmission
Axle ratio
Inertia Weight
Displacement
Carburetion
Inline 4 cylinder
M5
4.30
2250 pounds
(1020 kilograms)
160,0, CC
1-2V
(1 Two-Barrel)
Inline 4 cylinder with DOHC
M5
4.38
2500 pounds
(1134 Kilograms)
2000 CC
4-1V
(4 singles-barrel)
Yamaha considered the multiple carburetion of the Celica vehicle
to be better s.uited to their lean burn concept than the single carbure-
tor system of the -.Corolla. Both vehicles had .accumulated approximately
4000 miles (7000 ..kilometres) with the Yamaha "engines at the time of
EPA .testing.
Test Program
The vehicles arrived on Monday August 19, 1974 and were con-
ditioned by driving the cars over the vehicle road preparation route
and then, using a chassis dynamometer, the Federal driving cycle.
The following tests were then conducted on the vehicles:
1. Corolla:
A. Four,.-cold start "75 Federal Test Procedures (FTP) at 2250
.po.unds (1020 kgm), simulated inertia weight. For one test the
distributor was modified.
B. Three highway fuel economy tests (FET) at 2250 pounds (1020 kgm)
simulated inertia weight. For one test the distributor was modified.
C. Steady state gaseous emissions testing at idle, 15 mph
(24,1 km/hr), 30 mph (48.3 km/hr) , 45 mph (72.4 km/hr) , and
60-mph (96..5 km/hr).
2. Celica:
A. Three cold.start '75 FTP: two at 2500 pounds (1134 kgm) and
one at 4000 pounds (1814 kgm) simulated inertia weight.
B. Three Highway FET: two at 2500 pounds (1134 kgm) and one
at 4000 pounds (1814 kgm) simulated inertia weight.
C. Steady State emissions testing.at idle, 15 mph (24.1 km/hr),
30 mph (48.3 km/hr), 45 mph (72.4 km/hr) and 60 mph (96.5 km/hr).
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The Corolla distributor advance was changed during the test
program by Yamaha to improve fuel economy. The distributor was
modified to give 5 degrees additional mechanical advance between
2000 and 2500 RPM while still giving the same maximum mechanical
advan ce.
Since the Celica had considerably higher than normal horsepower
for a car of its weight, it was tested at 4000 pounds (1814 kgm)
inertia weight, in addition to the standard weight of 2500 pounds
(1134 kgm), to evaluate the .performance of the system when operated
with a more typical power to weight ratio.
All EPA tests were run on .leaded fuel, although either leaded
or unleaded fuel may be used with the Yamaha Lean Cpmbustion System.
In addition to the analysis for typical gaseous emissions the
samples were analyzed for aldehydes using the MBTH (3-methyl, 2-
benzothiazplinone) method. Fuel economy was calculated using the
carbon balance technique. Because Yamaha had previously tested
the cars using a leaded fuel, sulfate emissions were not attempted
in order to prevent contamination of the EPA particulate tunnel.
In addition the evaporative emission tests required in 1975 FTP
were not attempted.
Test Results
Results of the emissions and economy tests on the Yamaha vehicles
are detailed in Tables I, II, and III. Pollutant mass emissions
are expressed in grams per mile. The fuel economy for the tests
was calculated Busing the carbon balance technique and is expressed
in miles per gallon. Equivalents of these emissions in grams per
kilometre and fuel consumption in litres per 100 kilometres are
given in parentheses.
Table I presents the results of the 1975 FTP emissions and
fuel economy measurements. Composite results are:
Yamaha Corolla
(4 test average)
Yamaha Celica (2500
Ibs. test 16-5791)
Yamaha Celica
(4000 Ibs.)
HC
gm/mi
(gm/km)
.36
(.22)
.34
(.21)
.46
(.28)
CO
gm/mi
(gro/km)
3,80
(2.36)
2.95
(1.83)
6.87
(4.27)
NC-X
gm/mi
(gm/km)
1.18
(.73)
1.54
(.96)
2.32
(1.44)
Fuel Economy(Consumption)
MPG (litres/100 km)
Urban Highway
16.0
(14.7)
14.5
(16.2)
14.7
(16.0)
28.7
(8.2)
23.6
(10.0)
19.4
(12.1)
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The Yamaha Corolla results demonstrate that levels of HC below
the original (1976) statutory emissions standards can be achieved with
this vehicle. CO levels were 12 percent above these standards and
oxides of nitrogen levels were consistently below the 1975 interim
emission standards. The high levels of HC and CO during bag 1 of
test 16-5805 appeared to be associated with the excessive cranking
by the EPA driver. For this test the fuel system was connected to' a
gasoline container for weighing the quantity of fuel used. It is-believed
that the cold start problem was possibly caused by the air in the fuel
system due to incomplete purging of air in fuel system when it was
reconnected. . . ,
When tested at the higher inertia weight, the Yamaha Celica easily
met the 1975 vehicle certification' levels. Urban fuel economy was
nearly identical to .that achieved at the lighter inertia weight. : It
should be noted however that the somewhat higher rear wheel tire losses
that would have occurred if the car actually weighed enough to place
It in the 4000. pound inertia weight class would have caused a slight
increase, in power requirements and a corresponding decrease in economy.
Fuel consumption w.as also checked by weighing the -fuel for one-
test on each vehicle. 'The results show close areeement.
Fuel Economy (Consumption)
MPG (litres/100 km)
.. calculated by
carbon balance weight
Yamaha Corolla 16.4 15.9
test 16-5807 (14.3) (14.8)
Yamaha Celica 14.7 14.8
test 16-5808 (16.0) '(15.9)
Aldehydes levels as measured by the" EPA MBTH method are:
Composite HC Ald'y
gm/mi gm/mi %
(gm/km) (gm/km) Ald'y
Yamaha Corolla .34 .0235 6.9%
test 16-5790 (.21) (.0146)
Yamaha Celica .34 .0137 4%
test 16-5791 (.21) (.0085)
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In, comparison, with, other late model cars, the Yamaha Lean Combustion
Engine System appears to .yield low aldehyde emissions.
Several driveability problems were encountered with both cars.
The Corolla surged slightly, during constant speed portions of the' FTP.
The Celica stalle.d at .least once during each cold start when accelerated
from idle. This occurred after.;.the vehicle was running at least two
minutes. The tnore experienced Yamaha driver was better able to anticipate
the car's performance and experienced no stall problems.
Comparison of the vehicles' fuel economy with certification results
for 1973 vehicles of similar weight and engine displacement is given
in-Table III. .It is, apparent that the Yamaha Lean Combustion Engine
System had worse fuel economy that the certification vehicles when the
standard test weightsi of 2250 and. 2500 are considered. However, it
should be noted that these vehicles are first generation prototypes and
Yamaha has claimed' that little attention was devoted to optimization
of fuel, economy. The 'comparison of the results using the 4000 pound
test weight for the, iCelica. .are considered more representative of the
potential of the system however since the Celica was the more refined
of, the tw.o test'vehicles and its power to weight ratio at a 2500 test
weight was not- representative of typical 2500 class cars.
Conclusions
1. On the basis of their initial tests, both EPA and Yamaha
agree that the results are promising enough to warrant additional
development by Yamaha. In particular; Yamaha will concentrate
on fuel economy improvements and EPA will agree to test additional
prototypes if fuel economy objectives are met.
2. The Yamaha Lean Combustion Engine System appears to have the
potential to meet .41 gpm HC and 3.4 gpm CO standards without
catalytic devices. A 2.0 gpm NOx standard appears to be achievable
with Yamaha system, however, NOx standards significantly lower
than this will.require further development.
3. There were fuel economy penalties when compared to current
(1975 model) vehicles achieving similar levels of pollutant emissions.
The 4000. pound test however demonstrates some potential for achieving
fuel economy equivalent to that shown by other control approaches.
4. Aldehyde emissions from the Yamaha Lean Combustion Engine System
were lower than present production cars.
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TABLE I
1975 FTP Results
Yamaha - Corolla
.Test No.
***
16-5769
16-5790
16-5807
16-5824
***
16-5791
16-5791
A***
16-5808
(1814 kgra)
16-5826
Hydrocarbons
Bag 1
1.72
(1.07)
1.37
(.85)
1.45
(.90)
1.40
(.87)
1.17
(.72)
5.46
(3.39)
1.38
(.86)
Bag 2
.04
(.02)
.05
(.03)
.04
(.02)
.04
(.02)
75
.11
(.07)
.20
(.12)
.15
(.09)
gm/mi*
Bag 3
.11
(.07)
.12
(.07)
.11
(.07)
.14
(.09)
Carbon Monoxide gm/mi*
Composite
.40
(.25)
.34
(.21)
.35
(.22)
.35
(.22)
FTP incomplete due to water
.15
(.09)
.20
(.12)
.35
(.22)
.34
(.21)
1.28
(.80)
.46
(.28)
Bag 1 Bag 2
11.72 .73
(7.28) (.45)
16.15 .81
(10.03) (.50)
16.72 .88
(10.38) (.55)
9.70 1.22
(6.03) (.76)
Yamaha
leak requiring
5.60 2.42
(3.48) (1.50)
iO.ll 3.24
(6.28) (2.01)
11.60 3.71
(7.28) (2.31)
Bag 3
1.65
(1.02)
1.72
(1.07)
1.95
(1.21)
2.49
(1.55)
Celica
shutdown to
1.97
(1.22)
2.28
(1.42)
9.32
(5.79)
- Composite
3.24
(2.01)
4.21
(2.62)
4.43
(2.75)
3.31
(2.06)
repair leak
2.95
(1.83)
4.39
(2.73)
6.87
(4.27)
Oxides of Nitrogen gm/mi*
Consumption
Bag 1 Bag 2
2.12 .76
(1.32) (.47)
2.13 .79
(1.32) (.49)
2.20 .85
(1.37) (.53)
1.92 .83
(1.19) (.52)
2.16 1.20
(1.34) (.75)
2.17 1.22
(1.35) (.76)
2.96 1.89
(1.84) (1.17)
Bag 3
1.21
(.75)
1.17
(.73)
1.33
(.83)
1.12
(.70)
1.73
(1.08)
1.79
(1.11)
2.64
(1.64)
Composite
1.16
(.72)
1.17
(.73)
1.26
(.78)
1.13
(.70)
1.54
(.96)
1.57
(.98)
2.32
(1.44)
Calculated Fuel
MFC**
75 FTP
16.6
(14.2)
15.5
(15.2)
15.7
(15.0)
16.2
(14.5)
14.4
(16.3)
14.6
(16.1)
14.7
(16.0)
29.6
(7.9)
28.5
(8.3)
__
23.1
(8.4)
10.2
(23.1)
24.0
(9.8)
19.4
(12.1
* ( ) gm/kra
**( ) Litres/lOOkm
*** Yamaha Driver
**** Excessive cranking during startup - (see text)
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TABLE II
Steady State Emissions
1600 cc Yamaha Corolla
Test No.
16-5770
16-5771
16-5772
16-5773
16-5774
16-5775
16-5777
16-5778
16-5779
16-5780
Speed
Idle (gm/5-
min.)
15 mph.
24.1 km/mi
(30 mph)
48.3 km/hr
(45 mph)
72.4 km/hr
(60 mph)
96.5 km/hr
Idle (gm/5-
min. )
(15 mph)
24.1 km/hr
(30 mph)
48.3 km/hr
(45 mph)
72.4 km/hr
96.5 km/hr
(60 mph)
Gear HC gm/mi*
N 0
2 0
3 0
4 0
5 0
2000 cc Yamaha
N .01
(oOl)
2 .01
(.01)
3 .0
(.00)
4 .0
(.00)
5 .0
(.00)
CO gm/mi*
.26
(.16)
.09
(.06)
.08
(.05)
.13
(.08)
.27
(.17)
Celica
.68
(.42)
.87
(.54)
.18
(.11)
.13
(.08)
.16
(.10)
NOx gm/mi*
.51
(.32)
.30
(.19)
.37
(.23)
.59
(.37)
1.05
(.65)
.36
(.22)
.52
(.32)
.55
(.34)
.89
(.55)
2.03
(1.26)
Fuel
Economy
NA
14.3
(16.5)
23.1
(10.2)
29.1
(8.1)
28.8
(8.2)
NA
17.7
(30.6)
20.2
(11.6)
23.3
(10.1)
22.1
(10.6)
* ( ) gm/km
** ( ) Litres/100 km
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TABLE III
Fuel Economy of Yamaha Vehicles and 1975 Vehicles
Yamaha Corolla
1975 Vehicles
Yamaha Celica
1975 Vehicles
Yamaha Celica
1975 Vehicles
Test
Inertia wt. Ibs,
2250
2250
2500
2500
4000
4000
Fuel Economy (Consumption)
MPG(litres/100 km)
Urban Cycle Highway Cycle
16.0
(14.7)
20.6 to 24.8
(9.5 to 11.4)
14.5
(16.2)
13.8 to 23.4
(10.0 to 17.0)
14.7
(16.0)
11.2 to 15.3
(15.4 to 21.0)
28.7
(8.2)
30.5 to 41.1
(5.7 to 7.7)
23.6
(10.0)
20.1 to 38.4
(6.2 to 11.7)
19.4
(12.1)
16.5 to 25.0
(9.4 to 14.3)
1975 Vehicle Data represents the calculated fuel economy from vehicle emission
certification tests. Above data is for vehicles equipped with manual transmissions,
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