EPA-AA-TAEB 76-19
Exhaust Emissions and Fuel Economy
of Three Prototype Honda Motorcycles
April 1976
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
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 operation, 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 vehicle 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.
Early in 1976, the Honda Motor Company, Ltd., of Japan, offered to
make available for EPA testing three prototype motorcycles designed to
meet the proposed 1978 Federal emission standards for motorcycles.
These motorcycles incorporated improvements in fuel metering and com-
bustion control to reduce exhaust emissions and improvements in durability
to maintain the reduced exhaust emissions over the useful life of the
vehicle. One motorcycle would be equipped with an auxiliary hydrocarbon
control device in the exhaust system. Data supplied by Honda indicated
that the prototype motorcycles would achieve the proposed 1978 standards
with considerable improvement in fuel economy over that delivered by
their current production motorcycles.
The EPA agreed to test the three prototype motorcycles, and also
requested that three current production motorcycles (which have un-
controlled exhaust emissions) be supplied with the prototype motorcycles
so that comparisons between current production motorcycles and the
prototype motorcycles could be made.
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Test Vehicle Descriptions
The three models of Honda motorcycles supplied to the EPA were a
CB750, a XL250, and a MT250. Except for emission controls, the pro-
duction and prototype motorcycles were identical.
The CB750 is a large-displacement street motorcycle. The engine is
a four-stroke, overhead cam four-cylinder, with a displacement of 736 cc.
One carburetor is used for each cylinder. The engine is air-cooled, and
is in a vertical configuration (1-4). The transmission is a five speed
manual. The CB750 was tested at an inertia mass of 330 kg. Emission
control is by engine modifications.
The XL250 is a medium displacement on/off road motorcycle. The
engine is a single cylinder, overhead cam four-stroke, with a displace-
ment of 248 cc. The engine has 4 valves, 2 intake and 2 exhaust. A
single carburetor is utilized for fuel metering and the engine is air-
cooled. The transmission is a five-speed manual. The XL250 was tested
at an inertia mass of 230 kg. Emission control is by engine modifications.
The MT250 is also a medium displacement on/off road motorcycle.
The engine is an air-cooled single cylinder two-stroke, with a displace-
ment of 248 cc. The transmission is a five-speed manual. The MT250 was
tested at an inertia mass of 210 kg. Emission control is by engine
modifications and auxiliary HC control in the exhaust.
Test Program
Exhaust emission and fuel economy tests were conducted in accordance
with the Notice of Proposed Rule Making (NPRM), Federal Register, October 22,
1975, Part III. The NPRM contains the proposed Federal exhaust emission
regulations and test procedures for motorcycles (scheduled to become
effective in 1978). Because the road load specified in the NPRM for
each inertia mass class has been determined to be in error, the motor-
cycles were tested at road load values supplied by Honda. The road load
values supplied by Honda are in close agreement with revised EPA road
load values (which had not been published at the time of this test
program).
On each of the prototype motorcycles, the following series of tests
were conducted: 1975 Federal Test Procedure ('75 FTP), EPA Highway Fuel
Economy Test, steady state tests and the EPA Sulfate test cycle (SC-7).
Two '75 FTP's and Highway tests were run on each prototype motorcycle
(three on the CB750). One set of steady state tests and sulfate cycles
were conducted.
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The production motorcycles were tested twice in accordance with the
'75 FTP and Highway Fuel Economy Test.
Steady state emissions and fuel economy were measured at idle,
10 kph, 30 kph, 50 kph, 70 kph and 90 kph. A five minute sample was
taken at each speed.
In discussions with Honda engineers, it was pointed out to EPA
personnel that exhaust emissions from air-cooled motorcycles are very
sensitive to engine temperature. Therefore, to achieve repeatable
steady state emissions, it is necessary to continuously monitor some
indicator of engine temperature (such as oil temperature). Because of
the need to complete the EPA testing of the motorcycles within a limited
time frame, a rigorous control of engine temperature during steady state
testing was not attempted. Each motorcycle was warmed up until the oil
temperature reached 65 C. Steady state tests commenced at this time,
beginning with the idle test and proceeding through the test speeds
up to 90.kph.
Sulfate and particulate emissions were measured from all six motor-
cycles. It was expected that sulfate emissions could successfully be
measured from the prototype MT250 which operates on unleaded fuel.
However, the other five motorcycles had previously been operated on
leaded fuel. Lead is known to interfere with the sulfate analysis pro-
cedure, so problems were anticipated when attempting to measure sulfate
emissions from these motorcycles.
A brief description of the sulfate test procedure is given at the end
of this report. A detailed description of the EPA sulfate test procedure
can be found in SAE publication number 760034, titled "Sulfuric Acid
Emissions from Light Duty Vehicles".
Driveability testing consisted of a short test drive of each pro-
duction motorcycle followed by a test drive of the same model prototype
motorcycle, and evaluating the two motorcycles relative to each, other.
No attempt was made to conduct a rigorous evaluation of driveability.
The purpose of the driveability testing was to determine if the proto-
type motorcycles had any obvious driveability faults that the production
motorcycles did not have.
Test Results
The following exhaust emissions and fuel consumption were measured
from the three prototype motorcycles.
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Summary of Prototype Motorcycle Test Data
'75 FTP Composite Mass Emissions
in grams per kilometer
HC CO NOx Fuel Consumption
CB750 Average
of 3 tests 1.47 8.3 0.71 4.5 liters/100 km
XL250 Average
of 2 tests 0.77 8.7 0.29 2.8 liters/100 km
MT250 Average
of 2 tests 3.92 9.9 0.02 3.2 liters/100 km
For comparison, the proposed 1978 Federal motorcycle emission standards
are (in grams per kilometer):
Displacement HC CO NOx
736cc 13.77 17 1.2
248cc 6.21 17 1.2
The emissions from all three prototype motorcycles are well within the
proposed 1978 standards.
Highway fuel consumption of the prototype motorcycles is presented
in the following table.
Highway Cycle Fuel Consumption
in liters/100 km
CB750 3.7
XL250 3.0
MT250 4.1
Highway cycle emissions are presented in Table V.
Exhaust emissions and fuel consumption of the three production
motorcycles are presented in Tables I, II and III. Additional '75 FTP
test data for the prototype motorcycles are also found in these Tables.
Both the XL250 and MT250 had higher fuel consumption during the
Highway Cycle than they did during the '75 FTP (urban driving). This is
probably due to the fact that these two motorcycles were operating near
wide open throttle during the Highway Cycle, which resulted in enrich-
ment of the fuel-air mixture.
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Steady state emissions of the prototype motorcycles are presented
in Tables VI, VII and VIII.
Results of the driveability tests indicate that the prototype MT250
and CB750 had slightly degraded driveability when compared to the pro-
duction motorcycles. The prototype and production XL250 had comparable
driveability. Both versions of the XL250 could be driven immediately
following a cold start without requiring any warmup. The prototype
XL250 did not exhibit any symptoms of lean carburetion.
The production MT250 generally had good driveability characteristics.
The prototype MT250 exhibited several driveability faults that were not
experienced with the production MT250. When operating the engine at
constant speed below 4000 rpm in 1st, 2nd and 3rd gears, symptoms of
lean carburetion were evident. The engine would not operate smoothly in
this speed range, making the motorcycle difficult to drive at low
speeds that would be encountered in urban-suburban driving. In ad-
dition, the engine returned to idle very slowly when declutching on
decelerations.
The production CB750 had one significant driveability fault: it
was necessary to warm up the engine for one to two minutes after a cold
start before the motorcycle could be driven.
The prototype CB750 had symptoms of lean carburetion. The idle
speed was slightly variable, and some lean surge was evident in all
gears when driving at constant speed. A significant hesitation occurred
when accelerating hard (WOT) from engine speeds below 3500 rpm in 4th
and 5th gears. However, this is probably a lower engine speed than one
might normally use in these gears. The driveability of the prototype
CB750 improved with engine running time. Unlike the production CB750,
the prototype could be driven immediately following a cold start.
Sulfate and particulate emissions measured over the EPA Sulfate
Cycle are presented in Table IX-. Attempts to measure sulfate emissions
from all the motorcycles except the prototype MT250 were unsuccessful,
possibly due to residual lead interference. (A recent modification to
the sulfate analysis system recommended by the EPA Office of Research
and Development may eliminate lead and various anion interference.)
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In addition, high levels of liquid condensate were noted in the
exhaust collection manifold that connects to the motorcycle exhaust
pipes. This condensate appeared to contain organic type compounds,
possibly from unburned oil or higher molecular weight hydrocarbons. The
condensate was also found to contain some sulfate when a sample was
analyzed on the barium chloranilate system. These phenomena would
affect the results for all six motorcycles.
With these caveats, it can be noted that the prototype MT250
seemed to emit only small quantities of sulfate. However the particulate
emissions from this motorcycle are very high (110 mgpm for the controlled
version and 340 mgpm for the uncontrolled version), compared to particulate
emissions from automobiles. The other two motorcycles (XL250 and CB750)
showed very low particulate emissions.
Conclusions
The prototype motorcycles met the proposed 1978 emission regula-
tions with considerable improvement in fuel consumption compared to
current production motorcycles.
All three prototype motorcycles demonstrated substantial reductions
in HC and CO emissions compared to the production motorcycles. Reduc-
tions in HC emissions ranged from 26% (XL250) to 73% (MT250). Reductions
in CO ranged from 44% (XL250) to 81% (CB750). The XL250 and CB750 had
increases in NOx emissions of 93% and 318% respectively. However, even
with this large percentage increase, the NOx emissions from the CB750
were only 0.71 grams per kilometer.
Fuel consumption was improved by 13 to 40% during urban driving
('75 FTP). Reductions in highway fuel consumption ranged from 17% to
43%.
In the case of the XL250 and CB750, these reductions in exhaust
emissions and fuel consumption have been achieved with relatively minor
modifications to the engine and fuel system, and have not affected
maximum power output. The modifications made to the MT250 were somewhat
more extensive and involved a 5% loss in peak power output.
Data supplied by Honda regarding these prototypes indicate that the
savings in fuel costs over the life of the motorcycle would pay for the
engine and fuel system modifications.
Both the MT250 and CB750 prototypes demonstrated some deterioration
of driveability when compared to the production models. Driveability of
the prototype XL250 was comparable to the production XL250.
The driveability of the CB750 and MT250 could probably be improved
by slightly decreasing the air-fuel ratio. Both motorcycles are suf-
ficiently below the proposed 1978 emission levels to allow some mixture
adjustment.
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Table I
MT250 '75 FTP Mass Emissions
in grams per kilometer
Test # HC CO
Production MT250 (uncontrolled)
CO,
NOx
18-1051
18-1061
Average
13.19
15.92
14.56
28.2
29.6
28.9
33.5
32.2
32.9
0.02
0.02
0.02
Prototype MT250
18-714 3.96 10.2 46.2 0.02
18-850 3..S7 9.6 46.3 0.02
Average 3.92 9.9 46.3 0.02
% change from
baseline -73% -66% +41% 0
liters/100 km (miles/gal.)
5.1 (46.1)
5.5 (42.8)
5.3 (44.5)
3.2 (73.5)
3.1 (75.9)
3.2 (74.7)
-40% (+68%)
Table II
XL250 '75 FTP Mass Emissions
in grams per kilometer
Test # HC CO
Production XL250 (uncontrolled)
CO,
NOx
18-1053
18-1065
Average
0.99
1.08
1.04
15.1
15.7
15.4
44.3
48.9
46.6
0.15
0.15
0.15
Prototype XL250
18-791 0.82 9.0 52.0 0.31
18-789 0.71 8.3 48.9 0.27
Average 0.77 8^7 50.5 0.29
% change from
baseline -26% -44% +8% +93%
liters/100 km (miles/gal.)
3.0 (78.4)
3.3 (71.3)
3.2 (74.9)
2.9 (81.1)
2.7 (87.1)
2.8 (84.1)
-13% (+12%)
1978 Federal Motorcycle Emission Standards for 248cc displacement.
HC CO NOx
6.21 gm/km 17 gms/km 1.2 gms/km
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Table III
CB750 '75 FTP Mass Emissions
in grams per kilometer
Test f EC CO
Production CB750 (uncontrolled)
18-1045 2.81 47.0
18-1057 . 2.41 39.9
Average 2.61 43.5
Prototype CB750
18-778
18-857
18-776
Average
% Change from
baseline -44% -81%
CO,
78.5
67.4
73.0
NOx
0.20
0.14
0.17
1.57
1.51
1.32
1.47
8.0
8.8
8.2
8.3
88.7
85.5
88.5
87.6
0.75
0.68
0.70
0.71
Liters/100 km (miles/gal.)
6.9 (34.1)
5.9 (39.9)
6.4 (37.0)
4.5
4.4
4.5
(52.3)
(53.5)
(52.3)
+20%
+318%
4.5 (52.7)
-30% (+42%)
1978 Federal Motorcycle Emission Standards for 736cc displacement
HC CO NOx
13.77 gins/km 17 gms/km 1.2 gms/km
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Table IV
Test #
CB750
18-776
18-778
18-857
MT250
18-714
18-850
XL250
18-789.
18-791
Individual Bag Emissions
in grams per kilometer
Prototype Motorcycles
Bag
HC
1.97
2.78
2.49
5.09
5.55
0.87
0.93
1: Cold Transient Bag 2: Stabilized
CO C02 NOx £/100km HC CO CO NOx £/100km
4.9
5.6
5.8
13.1
14.6
8.6
8.6
96.6
98.3
98.4
52.3
53. .1
55.2
59.2
0.84
0.94
0.88
0.03
0.03
0.32
0.35
4.7
5.0
,4.9
3.8
4.0
3.0
3.2
1.18
1.32
1.36
3.51
3.32
0.69
0.83
10.6
9.8
11.2
6.7
5.5
7.7
8.4
87.2
87.7
83.2
44.4
43.8
46.0
49.2
0.35
0.40
0.34
0.01
0.01
0.18
0.23
4.6
4.6
4.5
2.8
2.7
2.6
2.8
Bag
HC
1.08
1.14
1.06
3.95
3.61
0.63
0.72
3: Hot Transient
CO C02 NOx £/100k
6.2
6.5
6.6
14.6
13.6
9.3
10.2
85.0
83.4
80.3
45.1
46.0
49.7
51.5
1.24
1.27
1.18
0.02
0.03
0.38
0.41
4.2
4.1
4.0
3.4
3.4
2.8
3.0
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Table V
EPA Highway Cycle
Mass Emissions in
grams per kilometer
Test #
HC
CO
Production Motorcycles
MT250
18-1052
18-1063
Average
10.69
10.81
10.75
38.2
38.1
38.2
34.9
34.2
34.6
0.02
0.02
0.02
XL250
18-1054
18-1067
Average
CB750
18-1050
18-1059
Average
0.47
0.49
0.48
,96
,80
1.88
Prototype Motorcycles
MT250
18-667 3.98
18-788 3.86
Average 3.92
% change from
baseline -64%
XL250
18-790 0.45
18-792 0.40
Average 0.43
% change from
baseline -10%
CB750
18-777 0.68
18-779 0.72
Average 0.70
% change from
baseline -63%
C0~ NOx Liter/lOOkm (miles/gal.)
5.5 (42.8)
5.5 (42.8)
5.5 (42.8)
22.2 45,8 0.17 3.5 (67.2)
25.0 44.9 0.15 3.7 (63.6)
23.6 45.4 0.16 3.6 (65.4)
61.1 61.1 0.14 7.0 (33.6)
54.1 50.6 0.11 6.0 (39.2)
57.6 55.9 0.13 6.5 (36.4)
27.7 41.3 0.02 4.1 (57.4)
27.5 39.0 0.02 4.0 (58.8)
27.6 40.2 0.02 4.1 (58.1)
-28% +16% 0 -25% (+36%)
12.4 51.0 0.39 3.1 (75.9)
10.4 51.0 0.49 2.9 (81.1)
11.4 51.0 0.44 3.0 (78.5)
-52% +12% +175% -17% (+20%)
1.7 80.8 1.97 3.6 (65.4)
2.2 83.9 2.06 3.8 (61.9)
1.9 82.4 2.02 3.7 (63.7)
-97% +47% +1454% -43% (+75%)
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Table VI
MT250 Steady State
Mass Emissions in
grams per kilometer
HC
CO
CO,
NOx
Liters/lOOkm
Idle (300
sees)
10 kph,
1st gear
30 kph
2nd gear
50 kph,
4th gear
70 kph,
5th gear
90 kph,
5th gear
5.63 gms 6.3 gms
8.26 6.6
2.59 2.2
1.79 0.3
2.07 6.9
1.05 37.5
22.9 gms 0.0
50.3 0.01
37.4 0.01
39.9 0.01
40.5 0.03
39.7 0.02
3.7
2.1
2.0
2.5
4.3
Table VII
Idle (300
sees)
10 kph,
1st gear
30 kph,
2nd gear
50 kph,
4th gear
70 kph,
5th gear
90 kph,
5th gear
XL250
Mass
grams
HC CO
0.74 gms 7.0 gms
,0.62 17.9
0.41 14.1
0.34 8.7
0.33 9.7
0.51 18.2
Steady State
Emissions in
per kilometer
C02 NOx
36.1 gms 0.01 gms
69.1 0.02
49.4 0.04
40.4 0.12
45.6 0.25
55.3 0.42
Liters/lOOkm
4.2
3.1
2.4
2.6
3.6
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Table VIII
CB750 Steady State
Mass Emissions in
grams per kilometer
Idle (300
sees)
10 kph,
1st gear
30 kph,
1st gear
50 kph,
3rd gear
70 kph,
5th gear
90 kph,
5th gear
HC
2.22 gms
1.48
0.89
0.49
0.51
0.54
CO
12.1 gms
27.7
20.3
7.6
0.6
0.8
co2
87.0 gms
101.5
90.7
56.2
67.1
83.8
NOx
0.05
0.06
0.10
0.13
0.94
1.95
Liters/100km
6.4
5.3
3.0
3.0
3.7
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Table IX
EPA Sulfate Cycle Emissions in
milligrams per kilometer
Prototype Motorcycles
H2S04 Emissions Particulate Emissions
MT250 1.3 116.5
1.3 63.6
2.2 151.0
Average 1.6 110.4
XL250 * 12.9
* 2.5
Average 7.7
CB750 * 6.8
Production Motorcycles
MT250 * 381.2
* 293.8
Average 337.5
XL250 * 1.7
* 7.4
Average 4.6
CB 750 * 14.8
* 15.1
Average 15.0
* H?SO, measurements unsuccessful due to possible residual lead interference.
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1975 Honda CB750
Emission control system - Engine Modifications
Engine
type 4 stroke, Otto cycle, 1-4, ohc
bore x stroke 61 x 63 mm
displacement . 736cc
compression ratio ; . ^__9_. 2_:1
"fuel metering one carburetor per cylinder
fuel requirement leaded fuel
Drive Train
transmission type .... . . . . 5 speed manual
Chassis
type motorcycle
tire size 4.00 x 18 (rear)
curb weight . . . 246 kg
inertia weight 330 kg
passenger capacity 2
actual road load 30.7 Ib. ft at 65 kph
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1975 Honda MT250
Emission control system - Engine modification and exhaust treatment
Engine
type .2 stroke, Otto cycle-, single cylinder
bore x stroke 70 x 64.4 mm
displacement 248cc
compression ratio 6.4:1 (6.8:1 production)
fuel metering 1 barrel carburetor
fuel requirement unleaded fuel.
Drive Train
transmission type 5 speed manual
Chassis
type motorcycle
tire size . . . . . . .- 4.00 x 18 (rear)
curb weight 130 kg
inertia weight 210 kg
passenger capacity 1
actual road load 24.9 Ib ft at 65 kph
Emission Control System
basic type Engine modifications with auxiliary
HC control in the exhaust
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Engine
16
TEST VEHICLE DESCRIPTION
Chassis model year/make - 1975 Honda XL250
Emission control system - Engine modifications
4 stroke, Otto cycle, single cylinder, ohc
bore x stroke ........... 74 x 57.3 ^
displacement ...... 248cc
compression ratio .. 9.1:1
TueT metering. . 7 ... Y"7" ." . ~~T baTreT~carburetor
fuel requirement leaded fuel
Drive Train
transmission type ......,, 5 speed manual
Chassis
type motorcycle
tire size 4.00 x 18 (rear)
curb weight 148 kg
inertia weight . 230 kg
passenger capacity . . 2
actual road load 25.9 Ib. ft at 65 kph
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Procedure for Measuring Sulfate Emissions
1. The fuel was drained from the test motorcycle. The motorcycle
was re-fueled with Indolene HO containing 0.03 wt. % sulfur. This
fuel was used throughout the sulfate testing.
2. The motorcycle was driven over one LA-4 cycle in preparation for
the test series.
3. The following sequence of test cycles was used to measure sulfate
emissions:
a) Cold start '75 FTP.
b) One hot start sulfate cycle.
e) One EPA Highway Driving Cycle
d) One hot start sulfate cycle.
4. The barium chloranilate procedure was used to determine the con-
centration of sulfates in the exhaust.
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