76-3 TCA
An Evaluation of Two Honda Automobiles
Powered by 91 CID Stratified Charge CVCC Engines
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.
This evaluation of two Honda Compound Vortex Controlled Combustion
(CVCC) vehicles is the third opportunity for ECTD to report on the
emission and fuel economy performance of vehicles incorporating the
stratified charge engine that Honda Motor Company of Japan announced
publicly in the fall of 1972. Results of tests conducted by EPA
on three "Civic" vehicles powered by 119 CID (1950 cc) versions of
the CVCC engine were reported in TAEB report number 73-11. The 1975
FTP emission values for the first cars tested were:
Hydrocarbons (HC) 0.21 gm/mi (.13 gm/Km)
Carbon Monoxide (CO) 1.96 gm/mi (1.22 gm/Km)
Oxides of Nitrogen (NOx) 0.81 gm/mi (.50 gm/Km)
After their earlier work on four cylinder engines and subcompact
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cars Honda adapted the CVCC process to a larger engine and vehicle com-
bination to demonstrate that the CVCC concept would successfully reduce
emissions on full-size American cars. A 350 CID Chevrolet V-8 engine was
modified and installed in a Chevrolet Impala. After Honda reported
achievement of the 1977 Statutory Standards, an EPA confirmatory test
program was conducted during late summer of 1973 (see Report No. 74-13).
The average 1975 FTP emission values for this testing were:
Hydrocarbons (HC) 0.25 gm/mi (.16 gm/Km)
Carbon Monoxide (CO) 2.98 gm/mi (1.85 gm/Km)
Oxides of Nitrogen (NOx) 1.23 gm/mi (.76 gm/Km)
In September of 1973 EPA requested the loan of a CVCC powered Civic
for use in comparison tests between various stratified charge, Diesel,
and conventional engined vehicles. In response to this request two
vehicles were pTovided by Honda for an indefinite period of time. This
report covers the first series of in-house evaluations of the vehicles
loaned by Honda for the comparison program. Further testing and
comparisons with other vehicles will be drawn in future EPA reports.
Vehicles Tested
Both vehicles tested were front wheel drive Honda Civic sedans
powered by 90.8 CID versions of the CVCC engine. One vehicle was
equipped with the 4-speed manual transmission, the other an automatic
transmission. Neither vehicle was representative of the 1975 production
Honda Civic because they had been calibrated by Honda to achieve
the 1977 statutory standards of .41 HC, 3.4 CO and 2.0 NOx. The cars
are described in detail in the Vehicle Description sheets (Tables
1 and 2). Figure 1 is a photograph of the manual transmission Honda
CVCC Civic tested and Figure 2 is a top view photograph of that
vehicle's engine with the air cleaner removed.
The CVCC engine burns a heterogeneous air-fuel mixture and in
this respect is similar to the stratified charge engines of Ford
(PROCO) and Texaco (TCCS). While the Ford and Texaco engines use
direct cylinder fuel injection to obtain charge stratification,
the Honda CVCC engine obtains stratification with the use of a
separately carbureted prechamber. The CVCC is classified as a
"small volume" prechamber. The prechamber is just large enough
to provide a jet of flame to ignite the main chamber in which the
bulk of the combustion takes place.
Two separate intake valves are used on each cylinder of the
CVCC engine. One valve is located in the prechamber and the other in
the main chamber. One small barrel of the three barrel carburetor
used on the CVCC engine supplies a rich mixture to each prechamber.
The other two barrels supply the main combustion chambers with a
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3
Table 1
TEST VEHICLE DESCRIPTION
Chassis model year/make - 1974 Honda Civic CVCC with manual
transmission
Emission control system - pre-chamber stratified charge with
engine modifications
Engine
type . .... 4 stroke pre-chamber, stratified charge,
spark ignited, single over head camshaft
in-line 4 cyl.
bore x stroke 2.91 x 3.41 in. (74.0 x 86.5 mm)
displacement 90.8 cu. in. (1488 cc)
compression ratio . 8.1:1 ;
maximum power @ rpm 53 hp (39.5 kw) @ 5000 rpm
fuel metering carbureted 3 venturi downdraft
2 venturi for combustion chamber
1 venturi for pre-chamber
fuel requirement indolene clear (96 RON) used
octane requirement not determined
Drive Train
transmission type manual 4 speed
final drive ratio 4.73:1
Chassis
type front transverse mounted engine, front
wheel drive, 4 door unitized body
tire size 6.00 S 12-4PR
curb weight 1,640 Ib. (745 kg)
inertia weight 2,000 Ib. (907 kg)
passenger capacity 4
Emission Control System
basic type pre-chamber stratified charge, positive
crankcase ventilation
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Table 2
TEST VEHICLE DESCRIPTION
Chassis model year/make - 1974 Honda Civic CVCC with automatic
transmission
Emission control system - pre-chamber stratified charge with
engine modifications
type 4 stroke pre-chamber, stratified charge
spark ignited, single over head camshaft
in-line 4 cyl.
bore x stroke 2.91 x 3.41 in. (74.0 x 86.5 mm)
displacement 90.8 cu. in. (1488 cc)
compression ratio ' 8.1:1
maximum power @ rpm 53 hp (39.5 kw) @ 5000 rpm
fuel metering carbureted 3 venturi downdraft
2 venturi for combustion chamber
1 venturi for pre-chamber
fuel requirement indolene clear (96 RON) used
• octane requirement not determined
Drive Train
transmission type 2 speed automatic
final drive ratio 4.12:1
Chassis
type front transverse mounted engine, front
wheel drive, 4 door unitized body
tire size 6.00 S 12-4PR
curb weight 1,660 Ib. (755 kg)
inertia weight 2,000 Ib. (907 kg)
passenger capacity 4
Emission Control System
basic type pre-chamber stratified charge, positive
crankcase ventilation
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Figure 1. Honda CVCC Civic with Manual Transmission
Main chamber carburetor
primary venturi
Main chamber carburetor
secondary venturi
Prechamber carburetor
venturi
Heat shield —
Valve cover
Figure 2. Ton View of Engine
with Air Cleaner Removed
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very lean mixture. Combustion is initiated in the prechamber with
a conventional ignition system and spark plugs (one plug per pre-
chamber) . As the burning gases expand from the prechamber, they
ignite and burn the lean mixture present in the main chamber. A
schematic of the combustion system appears in Figure 3.
The overall air-fuel ratio of the CVCC engine is significantly
leaner than stoichiometric. Conventional engines cannot generally
be operated as lean because of the difficulty in consistently
igniting homogeneous mixtures leaner than about 18:1 A/F. Ignition
is easily achieved in the CVCC engine by locating the spark plug
in the fuel rich prechamber. The very lean overall operation is
conducive to low CO emissions because the high availability of
oxygen facilitates the conversion of CO to CO.. The combination
of adequate oxygen and temperature in the main chamber is the
essential factor in controlling HC emissions.
NOx formation is a function of air (N + 0 ) availability and
temperature. The initial portion of the combustion in the CVCC
engine occurs in the very rich region of the prechamber where the
air availability is low, keeping NOx formation low. By the time
the combustion has progressed to the main chamber, where there is
high air availability, NOx formation stays low since the temperature
has dropped because of expansion and the lean conditions.
No "add-on" type emission control systems such as catalysts,
air injection, or exhaust gas recirculation (EGR) were used on
the test vehicles but the exhaust manifolds are sized to promote
post-cylinder HC oxidation.
Test Procedures
Exhaust emission tests were conducted according to the 1975 Federal
Test Procedure ('75 FTP), described in the Federal Register of
November 15, 1972, and the EPA Highway Cycle Test (HWC), described
in the EPA Recommended Practices for Conducting Highway Fuel Economy
Tests. Both of these tests are conducted on a chasses dynamometer and
employ the Constant Volume Sampling (CVS) procedure, which gives
exhaust emissions of HC, CO, NOx and C0_ in grams per mile. Fuel economy
is calculated by the carbon balance method. The fuel used was Indolene
unleaded 96 RON gasoline.
As received by EPA each vehicle had only been driven approximately
100 miles. After the initial tests were run both vehicles were taken
to a test track for accumulation of 4000 miles under AMA durability
conditions before any additional testing was performed.
Test Results
1975 FTP tests results for both vehicles are given in table 3.
Highway cycle results are given in table 4. It is evident from
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HONDA
CIVIC CVCC ENGINE
overhead
camshaft
spark plug
prechamber inlet valve
prechamber
Figure 3
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table 3 that emission levels just under the 1977 statutory standards
can be achieved with the standard transmission vehicle. The CO
results for the automatic transmission vehicle were slightly over
the 3.4 g/mi 1977 statutory standard for CO.
Table 4 results indicate approximately 32% better fuel economy
was achieved on the highway driving cycle than on the urban cycle.
This fuel economy difference is within the range of results which
have been seen for conventional engine powered vehicles.
Tables 3 and 4 reflect results using two different sets of tires.
After the 4000 mile break-in at the Dana test track the front tires of
both vehicles were worn out due to the tightness and surface roughness
of the Dana track. A new set of four tires was purchased. The tires
selected were radial ply (size 155 SR12); being the same size offered
as on option by Honda. These were mounted on one vehicle and the stock
(size 6.00 S12-4PR) bias ply rear tires of each vehicles were combined
as a set for the other vehicle. Upon testing the vehicle with the radial
tires a significant loss in fuel economy was observed. The tires
were suspect and the vehicles were retested with the stock tires which
showed improved fuel economy. Upon comparison of the new radial tires
with the stock tires it was found that the radials were approximately
one inch smaller in diameter. Increased fuel usage probably resulted
from an effective increase in axle ratio resulting from the small
diameter tires, and from increased tire flexure caused by the geometric
relationship between the smaller diameter tires and the fixed roller
spacing of the dual roller Clayton dynamometers used for testing.
The influence of tire flexture on dynamometer loading is probably
most noticeable for vehicles with less than 13" wheels as is the
case for the Civic. Tables 3 and 4 also compare the emission and
economy values of the two CVCC prototypes to the values obtained
on 1975 production versions of the Honda Civic. The CVCC production
cars calibrated to higher emission levels demonstrated fuel economy
that was nearly identical to the lower emission prototypes. The
conventional engine powered Civic vehicles had almost double the
HC and CO levels of the low emission prototypes. Urban economy for
the conventional engine powered vehicles was only 3% better than the
prototype CVCC's. Highway fuel economy was 5% better for the
conventional engine.
Conclusions
The standard transmission model Honda CVCC Civic demonstrated
the ability to meet the 1977 statutory emission levels of 0.41 HC, 3.4
CO, and 2.0 NOx. The automatic transmission model met the 1977 HC
and NOx levels, but exceeded the CO level by approximately .5 grams/
mile. Fuel economies of these two vehicles were essentially the same
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as those of the 1975 Honda CVCC Civic certification cars. Thus it
appears that calibrating to the more stringent 1977 emission levels
has not significantly degraded fuel economy from the 1975 model year.
As the maximum mileage of these vehicles as tested was around
4000 miles, the ability to maintain the 1977 calibrations with higher
mileage accumulation has yet to be determined.
A 10% decrease in the '75 FTP fuel economy was observed when the
standard bias ply tires were replaced with the optional radial ply
tires. The reasons for this are not certain, but the smaller diameter
of the radial and its interaction with the chassis dynamometer rolls
are suspected.
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TABLE 3
1975 FTP Composite Results
Mass Emissions
grams/mile
(grams/kilometre)
Fuel Usage
miles/gallon
(litres/100 kilometres)
Manual Transmission
Test Car, 1500 cc
CVCC engine, 2000 IW
Automatic Transmission
Test Car, 1500 cc
CVCC engine, 2000 IW
1975 Honda Certifi-
cation Cars
w/bias ply tires
Federal standards
Initial tests, 100
miles
w/bias ply tires
After 4000 miles,
w/bias ply tires
After 4000 miles,
w/radial tires
Initial tests, 100
miles
w/bias ply tires
After 4000 miles,
w/bias tires
After 4000 miles,
w/radial tires
CVCC w/manual
trans.
CVCC w/auto
trans.
1200 cc con-
ventional engine
w/manual trans.
1200 cc con-
ventional engine
w/auto trans.
1975 49-state
1975 California
1977
1978
HC
.37
(.23)
.39
(.24)
.36
(.22)
.42
(.26)
.40
(.25)
.39
(.24)
.55
(.34)
.51
(.32)
.81
(.50)
.61
(-38)
1.5
(.93)
.9
(.56)
.41
(.25)
.41
(.25)
CO
2.91
(1.81)
2.97
(1.85)
3.48
(2.16)
3.80
(2.25)
4.58
(2.85)
3.96
(2.46)
4.34
(2.69)
4.79
(2.98)
6.67
(4.14)
6.00
(3.73)
15.0
(9.3)
9.0
(5.6)
3.4
(2.1)
3.4
(2.1)
NOx
1.44
(0.89)
1.30
(0.81)
1.32
(0.82)
1.83
' (1.14)
1.72
(1.07)
1.73
(1.08)
1.25
(.78)
1.10
(.68)
1.40
(.87)
1.91
(1.19)
3.1
(1.9)
2.0
(1.2)
2.0
(1.2)
0.40
(.25)
26.3
(8.94)
26.4
(8.91)
23.3
(10.1)
24.1
(9.76)
24.5
(9.60)
22.2
(10.6)
27.5
(8.55)
24.2
(9.72)
28.0
(8.40)
24.5
(9.60)
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1500 cc Manual trans CVCC
w/bias ply tires
w/radial ply tires
1500 cc Auto trans CVCC
w/bias ply tires
w/radial ply tires
TABLE 4
EPA Highway Cycle Results
Mass Emissions
grains/mile
(grams/kilometre)
HC
CO
NOx
.02 .50 1.75
(.01) (.31) (1.09)
.02 .61 1.76
(.01) (.38) (1.09)
1975 Honda certification cars (w/bias ply tires)
1500 cc CVCC manual trans
1500 cc CVCC, auto trans
1200 cc conventional engine
w/manual trans
1200 cc conventional engine
w/auto trans
Fuel Usage
miles/gallon
(litres/100 kilometres)
.02
(.01)
.01
(.01)
.66
(.41)
.67
(.42)
1.47
(.92)
1.49
(.93)
36.5
(6.46)
34.8
(6.76)
30.4
(7.74)
30.3
(7.76)
38.4
(6.13)
28.8
(8.17)
40.0
(5.88)
30.0
(7.84)
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Test 0 Vehicle Tire Type
Hydrocarbon
Bag 1 Bag 2 Bag 3
a/mi
21-90
16-i859
16-4380
15-4471
15-4450
15-4422
21-91
15-4857
15-4470
Std.Tran. Bias ply
ii it
ii u
11 ' Radial
ii u
u u
Auto Tran. Bias
It M
" Radial
0.82
0.89
0.97
1.07
0.83
0.93
1.19
0.95
1.08
0.15
0.10
0.11
0.11
0.10
0.11
0.15
0.13
0.13
0.45
0.28
0.71
0.32
0.45
0.45
0.35
0.52
0.36
APPENDIX
Individual Bag Results
Carbon Monoxide Carbon Dioxide
Bag L Bag 2 Bag 3
g/mi g/mi g/ini
3.90 2.75 2.48
4.22 2.36 1.90
5.16 2.68 3.17
6.25 2.67 1.57
5.16 3.07 3.28
5.16 2.82 3.33
6.41 2.91 3.54
12.32 2.37 2.99
5.82 3.41 3.61
Rag 1 Bag 2 Bag 3
g/mi g/rai g/mi
332.4 344.2 304.9
315.8 332.8 284.8
344.4 364.7 312.9
360.0 403.0 336.8
370.2 387.8 336.4
364.9 405.1 330.5
369.1 378.6 320.7
365.5 363.3 325.8
412.1 404.9 355.1
Oxides of Nitrogen
Bag 1 Bag 2 Bag 3
g/mi_ g/mi g/mi
1.83 1.07 1.86
1.62 0.96 1.59
1.70 1.03 1.62
1.58 0.97 1.57
1.70 1.06 1.65
1.62 1.10 1.60
2.37 1.50 2.04
2.21 1.40 1.98
2.07 1.41 2.09
Fuel Economy
Bag 1 Bag 2 Bag 3
mpg tpg rcpg , _
26.0 25.4 28.6
27.3 26.3 30.7
25.0 24.0 27.7
23.8 21.8 25.9
23.3 22.6 25.9
23.6 21.6 26.3
23.2 23.1 27.1
22.9 24.1 26.7
20.9 21.6 24.5
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