EPA-460/3-74-011A
October 1975
A STUDY
OF STRATIFIED CHARGE
FOR LIGHT DUTY
POWER PLANTS
Volume 2
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
Ann Arbor, Michigan 48105
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This report Is Issued by the Environmental Protection Agency to report
technical data of Interest to a limited number of readers. Copies are available
free of charge to Federal employees, current contractors and grantees, and non-
profit organizations - as supplies permit - from the Air Pollution Technical
Information Center, Environmental Protection Agency, Research Triangle Park,
North Carolina 27711* or, for a fee, from the National Technical Information
Service, 5285 Port Royal Road, Springfield, VIrginla.22151.
This report was furnished to the Environmental Protection Agency by
Ricardo and Company Engineers (1927) Ltd., In fulfilment of Contract No. 68-03-0375.
The contents of this report are reproduced herein as received from Ricardo and
Company Engineers (1927) Ltd. The opinions, findings, and conclusions expressed
are those of the authors and not necessarily those of the Environmental Protection
Agency. Mention of company or product names Is not to be considered as an endorse-
ment by the Environmental Protection Agency,
Publication No. EPA-^60/3-7*»-011
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A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
VOLUME 2
by
RICARDO AND COMPANY ENGINEERS (192?) LTD
BRIDGE WORKS,
SHOREHAM-BY-SEA, SUSSEX, BN*t 5FG
CONTRACT NO, 68-03-0375
EPA PROJECT OFFICES
T.C. AUSTIN AND J.J. MCFADDEN
PREPARED FOR
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR AND WASTE MANAGEMENT
OFFICE OF MOBILE SOURCE AIR POLLUTION CONTROL
EMISSION CONTROL TECHNOLOGY DIVISION
ANN ARBOR, MICHIGAN *t8l05
October 1975
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ABSTRACT
The objectives of this project were to determine the acceptability of various
types of stratified charge engines as potential power plants for light duty
vehicles and motorcycles In America. The light duty vehicle considered was a 4/5
seat compact sedan with good acceleration capabilities and exhaust emissions below
a primary target of 0.41 g/mlle HC, 3.4 g/mlle CO, 1,5 g/mile NO . A secondary
target of 0.41 g/mlle HC, 3.4 g/mlle CO and 0.4 g/mile NO was also considered.
X
A literature survey was undertaken, comparing stratified charge engines with
examples of good conventional gasoline and diesel engines, While some stratified
charge engines had exhaust emission or fuel economy advantages, there were always
sacrifices In other areas,
Eleven engines were configured, four of which were specifically directed to-
wards the secondary emission targets, A method of rating the engines was derived,
and the design concepts were compared with two gasoline engines by a jury panel,
The overall result was that the Ford PROCO and Honda CVCC combustion processes
were serious contenders to the gasoline engine at the primary emission target, and
that both of these systems, together with the VW combustion process, might be
suitable at the secondary targets.
This section of the report covers the engine configuration study and power
plant rating, as well as the overall conclusions and recommendations from the
complete project.
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A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
SECTION G
ENGINE CONFIGURATION STUDY
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SUMMARY
This section contains details of the stratified charge gasoline engine con-
figurations which were schemed as potentially viable light duty power plants,
Information on two conventional gasoline power plants is also included for corn-
par I son.
The stratified charge power plants were all designed to propel the target
vehicle for the study, a 4-5 seat sedan with a maximum curb weight of 1600 kg
(3500 Ib) capable of 0-96 km/h (0-60 mph) In 13.5 s and 40-112 km/h (25-75 mph)
In 15 s. Computer calculations Indicated that a bare engine power of about 96 KW
(128 bhp) was required If a conventional 3-speed automatic transmission was used.
The range of engine configurations presented for each of the seven stratified
charge categories was largely dictated by the combustion limitations of each
category. In general, the configurations were schemed using combustion layouts
which have been proven and for which published performance results could be used,
In order that the performance of the proposed power plants could be predicted.
The following engines were configurated, in order to achieve the primary
emission target (HC 0.41 g/mlle, CO 3.4 g/mile, NO l'.5 g/mlle) and also the
secondary emission target (HC 0.41 g/mlle, CO 3.4 g/mlle, NO 0.4 g/mlle)--
f\.
Category 1
Primary Emission Target
(1) V-8, 4.12 1, PROCO combustion system
(2) Inline 6, 4.16 1, PROCO combustion system
Secondary Emission Target
(3) V-8, 5-25 1, PROCO combustion system,
Category 2
Primary Emission Target
(1) V-8, 5.4 1, TCCS combustion system
(2) V-8, 4.16 1, Turbocharged TCCS combustion system
(3) 2 Bank, Rotary, 5.5 1, CurtIss-WrIght combustion system
Secondary Emission Target
(4) V-8, 5.87 1, Turbocharged, TCCS combustion system
Category 3
Primary Emission Target
(1) V-7, 5.06 1, MANrFM combustion system
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Category k
Primary Emission Target
(1) V-8, 3-67 1, VW combustion system
Secondary Emission Target
(2) As above
Category 5
Primary Emission Target
(1) V-8, k.26 1, CVCC combustion system
Secondary Emission Target
(2) V-8, 5.58 1, CVSS combustion system
Category 6
No configurations
Category 7
No configurations
Drawings and performance curves were prepared for all the above engines, each
configuration being schemed In sufficient detail to allow a reliable assessment
of Its potential. The In-vehlcle characteristics of the power plant, i.e.
emissions, fuel consumption and noise, were estimated on the basis of previous
engine performance In cars and on test beds, of each combustion system,
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ENGINE CONFIGURATION STUDY
INTRODUCTION
The literature survey gives a preliminary and overall comparative analysis
of the potential of each category of stratified charge engine as a light duty
power plant, The aim of this configuration study is to enable a quantitative
assessment to be made of all the characteristics of those stratified charge engines
which were considered feasible as light duty power plants. This is achieved by
scheming the engines specifically for a particular vehicle and emissions
environment,
Definition of Vehicle
The vehicle selected for this study was a passenger car (typically a V5 seat
sedan) with a maximum test Inertia of 1600 kg (3500 Ib) when loaded and capable of
meeting the EPA standard car performance specifications, i.e. 0-97 km/h (0-60 mph)
in less than 13.5 s, 1*0-112 km/h (25-70 mph) In less than 15 s, and capable of
overtaking an 80 km/h (50 mph) truck in less than 15 s.
To assist In the definition of the power plant a computer program was written
to allow the maximum power output of the engine, the shape of Its torque curve and
the transmission system necessary to achieve these acceleration capabilities to be
calculated.
Use of this program showed that with a three-speed automatic gearbox and with
the final drive ratios selected to give approximately 136 km/h (85 mph) at the
rated engine speed, a bare engine power of 96 KW (128 bhp) was required to satisfy
the acceleration target. This Implies that the vehicle has acceleration "in hand"
at this rated speed and thus a non-speed limited engine will permit maximum speeds
on level roads to be greater than this nominal figure. Various gear ratios and
amounts of torque back-up were tried and the minimum power plant requirements were
finally selected ast-
Rated Speed 96 KW 128 bhp
.75 Rated Speed 76 KW 102 bhp
.50 Rated Speed 53 KW 71 bhp
.25 Rated Speed 17 KW 22.7 bhp
The detailed shape of the torque curve which is dependent on the particular
characteristics of each stratified engine variant is not a critical factor in
achieving the above performance requirements.
Target Emissions
For the purposes of this study two target emission levels were envisaged.
These were«-
Primary (or short term)
HC 0.1*1 g/mile
CO 3.1* g/mlle
NO 1.5 g/mlle
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Secondary (or long term)
HC O.k] g/mlle
CO 3.*» g/mile
NO O.k g/mlle
x 3
The above levels were selected essentially as the proposed 'Interim1 Federal
emissions levels and the statutory 'final1 limits as prescribed under the Clean
Air Act.
Configuration Notes
Each configured engine Is described by a separate specification and performance
table followed by notes on
(a) the predicted performance characteristics of the engine, and
(b) design notes which make reference to the performance curves and
design schemes Included In the text,
At the end of the Configuration Study a Summary Table Is shown which allows an
overall comparison to be made of all the engine configurations. The Summary Table
also Includes details of the gasoline and diesel I.D.I, engines.
The following considerations were taken Into account when estimating the
performance levels of each englne/vehlcle<-
(1) Any emission control system should be able to operate for 50,000 miles or at
least 25,000 miles with little maintenance in order to warrant practical con-
sideration. Factors such as the physical Integrity of the specialised exhaust
system, spark plug life, deterioration of the catalysts, thermal reactors and
EGR system have been considered when predicting the emission durability of
each engine configuration.
(2) In the summary table, the engine baseline HC and CO exhaust emissions are
presented as well as controlled levels1, Because of the different exhaust
flow rates, exhaust temperatures and engine baseline emissions each category
of stratified charge engine requires a different method of exhaust oxidation
treatment, the severity of which generally Increases with the baseline
emission level. The baseline HC and CO emissions have Included the effects
of EGR where fitted, therefore no baseline NO emissions are quoted.
X
Exhaust emissions were estimated by consideration of the performance of each
combustion' system In vehicles and from test bed results.
(3) In the case of those engines which have a smoke limited performance, the
torque curves are restricted to give smoke levels ranging from approximately
7% opacity at low speed to 2±% opacity at the rated speed. It is felt that
smoke levels higher than these would be totally unacceptable for a passenger
car engIne.
(b) Prediction of the fuel consumption on the CVS-CH test cycle for each engine
configuration was based on the results from a range of test engines and
vehicles uncovered by the literature survey. Published data was usually too
sparse to allow a more thorough comparison to be made between the stratified
charge variants. However, the CVS-CH test comparison Is now accepted as
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reflecting the true differences between systems since the cycle simulates
typical urban driving conditions. The fuel consumption has been predicted
while assuming the vehicle to have automatic transmission without lock-up,
With a manual gearbox the fuel consumption will be Improved by around 5"6%,
(5) Noise emission predictions were based on a distance of 15 m from the test
vehicle during the American drive-by procedure according to SAE J986A,
Established formulae were used which are known to be accurate for both
dlesel and gasoline engines. The method was:-
(a) prediction of the noise level of an equivalent conventional gasoline
engine of the same bore
(b) adjustment of this level by a correction factor based on either measured
comparative noise emissions or by consideration of the combustion pressure
diagram and engine structure,
These noise levels could be reduced by up to 3 dBA by the use of engine
shielding.
Design points which are applicable to all the reciprocating engines are as
fo11ows:-
(1) Cast Iron was universally applied as the cylinder block material for high
strength and low cost with integral cylinder bores. Cast iron was also
used for all cylinder heads.
(2) The major dimensions, design and rigidity of the crankcase and crankshaft
followed conventional gasoline engine practice in the cases when the maximum
cylinder pressures were equivalent to those of a gasoline engine. In all
cases the piston ring pack was designed for gasoline engine practice with
two compression rings and one oil control ring.
(3) Crankshaft bearing loadings were based on the maximum cylinder pressure and
taking Into account the bearing overlap but without Inertia relief, All
connecting rods were stralght^cut.
CO The cylinder head combustion gas face was made flat and parallel to the
cylinder head deck for simplicity of manufacture in most of the configurations
Exhaust valve seats were also Induction hardened to prevent valve seat
recession which can occur with unleaded gasoline,
(5) Valve gear generally adopted followed current American gasoline engine
practice with pushrod operated valves, pressed steel rockers and hydraulic
tappets. On the V-8 configurations a single central camshaft was chosen
for compactness and simplicity. Overhead camshafts were not considered to
offer any significant advantages for this application and speed ranges
although In one case It proved necessary In order to relieve cylinder head
congestion,
(6) The choice of a 90° V-angle for all the V-8 configurations was influenced by
current American practice. With a cruciform crankshaft complete external
balance and equal engine firing intervals are obtained. Complete external
balance Is also obtained with the In-line 6 configurations together with
equal firing Intervals.
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(7) V-8 balance: There Is complete balance of the primary forces, secondary
forces and secondary couples, Primary couples are fully balanced by means of
suitable crankshaft balance weights,
In-line 6 balance? Complete primary and secondary balance Is achieved. The
crankshafts are provided with counterweights to relieve Inertia loads on end
and central main bearings.
(8) For all the V-8 configurations the optimum position for the Inlet manifold
was found to be between the engine banks, This position was generally
determined by the need for a single throttle to be conveniently positioned,
Outboard Inlet manifolds make for difficult air control, Synchronisation
of two throttles, one per bank, would be necessary or alternatively long
Inlet tracts leading to a single throttle,
(9) In the Interests of low noise the use of sound deadened steel material was
used for the rocker box covers and oil sump covers on the V-8 configurations
and additionally for the tappet Inspection covers on the In-line 6 con-
figurations,
(10) V-8 water circuit: The water pump was positioned on the front face of the
block, discharging coolant through both cylinder banks and returning via the
cylinder heads to a collector with a single outlet.
In-line 6 water circuit: The water pump was positioned on the front face
of the block discharging directly into the cylinder block,
(11) The design of the complex fuel Injection systems for many of the engines
assumed the use of present-day technology In a form that could be developed
for production relatively quickly, In all cases this has resulted in a fully
mechanical system as In the stratified charge variants covered in the
literature survey. It Is quite possible that electronic fuel injection systems
offer significant advantages, but a longer development time would be
necessary before production could begin,
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GASOLINE ENGINE
While no engine configuration studies have been carried out on standard
gasoline engines, It was necessary to have estimates of performance for comparison
with the various stratified charge engines,
Two gasoline engines were studied, the first being a V-8 following current
American practice both In design and performance, and the second a 6 cylinder
engine more typical of European practice.
Category; Standard GasolIne
V-8, Naturally Aspirated Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Power
BMEP
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
97 mm
76 mm
1 .28
96 kW
at 66,7 rev/s
6.26 bar
7.9 bar
at '»1 .6 rev/s
285 Nm
25%
21 .*» kW/L
10.2 m/s
3.82 in
3.0 in
275 in3
128 bhp
at ^000 rev/min
91 lbf/inZ
115 lbf/in2
at 2500 rev/min
210 Ibf.ft
O'.l»65 bhp/in3
2000 ft/mln
Engine Weight
Predicted CVS-CH results
Fuel Economy
Fuel Consumption
HC
CO
Baseline/Controlled
NO Controlled
x
Estimated Noise
Specific Performance and Emissions
21*5 kg
16.0 mlles/U.S, gallon
1^.6 L/100 km
1.8/0.2 g/mile
30/1.0 g/mile
1.3 g/mile
71 dBA
Ib
Using typical specific performance levels for this type of engine, I.e.
21.0-22.0 kW/L (0.46-0.^8 bhp/in3), the target power output demands a swept volume
of 4,5 L (275 In3). This capacity, in conjunction with a rated speed of 66.7 rev/s
7
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(typical of most standard American engines) produces the target performance levels
resulting In satisfactory driving characteristics with a simple three or four
speed transmission. The performance curves for this engine can be seen In
Figure 1.
The performance levels can be achieved with the engine in low emissions build
but external hang on emissions control devices are necessary, their complexity
depending on the severity of the emissions target. The primary project targets can
be achieved by using close tolerance sophisticated carburettors In conjunction with
modulated exhaust gas recycle, air injection Into the exhaust and an oxidation
catalyst. All these devices can be considered current technology and the various
trade offs for low emissions are well known (Increased power plant weight, first
cost, maintenance cost, a demand for lead^free fuel, and a depreciation In vehicle
fuel economy),
A fuel economy of 16.0 mlles/U.S, gallon 04.6 L/100 km) has been assumed for
the gasoline powered vehicle when In the primary target build. This figure Is
representative of good gasoline engines of this type, The philosophy adopted in
the literature survey of making comparisons with good, rather than average,
gasoline engines has been retained for this study. The estimated engine weight
was 245 kg C540 Ib).
Using established noise prediction formulae, bare engine noise levels on a
test bed would be 94 dBA at rated load and speed. This correlates with a drive-by
noise level of 71 dBA at 15,23 m under standard American test conditions,
The secondary project emissions objectives of 0.4 g/mlle NO while maintaining
HC and CO levels, demand the additional use of a reducing catalyst and possible
further catalytic devices (getter box) to protect the reducing catalyst from
oxygen spikes. Due to the need to operate with low oxygen concentration in the
exhaust (less than 0,5%) It Is necessary to run with a mixture strength approaching
stolchlometrIc conditions with a resultant fuel economy penalty. However, although
the secondary target emissions can be reached at zero miles, the present day
reducing catalysts have Insufficient durability to achieve the secondary target,
Therefore no gasoline engines were configured for the secondary target.
Category; Standard Gasoline
In-LIne 6, Naturally Aspirated Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Power
BMEP
Max. BMEP
Max, Torque
Torque Back-up
8
88 mm
82 mm
1 ,08
2.99 L
96 kW
at 83',3 rev/s
7.6 bar
9.75 bar
at 50 rev/s
232 Nm
20%
3.46 in
3,22 In
183 In3
128 bhp
at 5000 rev/mln
110 Ibf/in2
141 Ibf/in2
at 3000 rev/mln
171 Ibf.ft
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Power/Unit Displacement 32.1 kW/L 0.7 bhp/irT
Max, Piston Speed 13.6 m/s 2680 ft/mln
Engine Weight 204 kg 450 Ib
Predicted CVS-CH Results
Fuel Economy 17,4 miles/U.S, gallon
Fuel Consumption 13.5 L/100 km
HC ) 1.8/0.2 g/mlle
CO J Baseline/Controlled 30/1.0g/mile
NO Controlled 1.3 g/mlle
?\
Estimated Noise 73 dBA
The first and obvious difference between American and European engines of
this power range Is that of specific performance. Whereas the American V-8 gasoline
engine runs to around 67 rev/s and develops 21 kW/L (0.47 bhp/ln3), the European
engine runs to at least 83 rev/s and develops a minimum of 32 kW/L (0.7 bhp/In3),
normally nearer 36 kW/L (0,8 bhp/ln3). The major reason for these vastly
differing philosophies Is one of economics} mainly because of taxation, European
fuel prices have always been high In terms of real spending power with a resultant
continuing trend towards small capacity, high economy engines and cars. On the
other hand, the price of fuel In America has always been low and fuel consumption
has never been a major consideration until recently, engine size has therefore
Increased over the years to Improve drlveabllity and to some extent is a sales
feature.
A total power requirement of 96 kW (128 bhp) and a torque back-up of 20%
to enable the prototype vehicle to achieve Its target performance could be
achieved easily with a 3 Htre, six cylinder engine running up 83.3 rev/s, A
typical oversquare cylinder configuration of 88 mm bore x 82 mm stroke (3,46" x
3.22") has been selected. The use of petrol Injection will ensure good distribu-
tion between cylinders and should allow the engine to run at generally leaner
mixture strength than If carburettors were used, Estimated performance can be
seen In Fig'. 2.
These performance figures and the project primary emissions targets could be
achieved using the same external hang-on control devices as the V-8 gasoline
engine, I.e. modulated exhaust gas recycle, air Injection and an oxidation
catalyst.
Overall economy levels during CVS-CH testing have been predicted at 17.4
mlles/U.S. gallon 03.5 L/100 km). This results In a total fuel consumption
saving of some 7.5% compared with the V-8 gasoline engine.
From European data, the predicted engine weight Is 204 kg (450 Ib), a
reduction of 41 kg (100 Ib) compared with the V<-8 engine.
Estimated drive-by noise levels of this engine In the prototype vehicle are
73 d!3A at 15 m '(50 ft). The reason for the 2 dBA Increase in drive-by levels
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compared with the V-8 Is the higher rotational speed of the 3 litre engine,
As with the V-8 engine, the secondary target could be achieved at low mile-
age with reducing catalysts but current versions of these catalysts cannot
achieve adequate durability and so no configuration is given for the secondary
target.
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ENGINE CONFIGURATION WITHIN CATEGORY I
The Ford PROCO combustion system was chosen from the various systems within
Category 1 for application to the configuration study because It has already been
satisfactorily developed and utilised for automotive purposes, In addition, the
hydrocarbon emission levels are tolerable, and can be easily controlled. This
system has, therefore, a better known potential compared to the other systems of
which only the M.C.P, has been developed to a stage suitable for possible
automotive application.
Turbocharged versions were not considered to give any useful advantages to
this category of stratified charge engine, and were, therefore, not Included,
No rotary engines were Included since It is believed that an early fuel Injection
timing would not provide satisfactory charge stratification during the period of
time before the Ignition point, Furthermore, no experimental evidence could be
found to support the feasibility of a rotary version within this category,
Engines Included In the configuration study and schemed to meet the primary
emission target were:-
(1) V-8, V.15 L, PROCO engine.
(2) I-L 6, k.\5 L, PROCO engine.
Only one engine configuration was considered feasible to achieve the
secondary emission target:-
(3) V-8, 5.25 L, PROCO engine
Category I
(1) V-8 Naturally Aspirated - PROCO Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Compression Ratio
Power
BMCP
Max. BMEP
Max, Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
Max. CylInder Pressure
87 mm
87 mm
1
*U5 L
1 1 x« 1
96 kW
at 66.7 rev/s
6.93 bar
8.9 bar
at 38 rev/s
292 Nm
23.1 kW/L
11 .6 m/s
65.5 bar
3.43 In
3.43 In
254 In3
128 bhp
at 4000 rev/mln
100 lbf/ln2
129 lbf/in2
at 2280 rev/min
215 Ibf.ft
0.504 bhp/!n:
2280 ft/mln
950 lbf/in2
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Con-rod
Distance between centres, L 148.6 mm
Ratio of L to crank throw (r), r 3.42
5.85 In
Cylinder bore spacing
Package
Engine length
height
width
box volume
weight
Predicted CVS-CH Results
Fuel Economy
Fuel Consumption
1 ,17 x cylInder bore
HC )
' Baseline/Controlled
CO )
NO Controlled
x
Estimated noise
770 mm
597 mm
600 mm
,275 m3
250 kg
30,3 In
23,5 In
23.6 In
9,72 ft:
550 Ib
18,7 miles/U.S. gallon
12.5 L/100 km
1 .0/0.15 g/mlle
8.0/1.0 g/mlle
1.1* g/mlle
71 dBA
Predicted Performance, Economy, Emissions and No Ise
A total swept volume o
bmep of 6.9 bar (100 Ibf/ln
yield 96 kw 0 28 bhp) .
) at
litre (254 in ) was calculated using an estimated
the rated speed of 66.7 rev/s (4000 rev/mln), to
The engine bmep curve was estimated by predicting the Imep from the volumetric
and Indicated thermal efficiencies, and taking account of engine friction,
Knowledge of the performance of the proposed helical type of Inlet ports provided
values of volumetric efficiency and Indicated thermal efficiencies were obtained
from published curves on PROCO engines- The friction (fmep) losses of the Ford 7
litre FCP engine were used for these calculations and the resulting engine bmep Is
slightly above that for the Ford Ll4l PROCO engine, The estimated performance
curve of this engine Is shown In Fig, 3.
To meet the primary NO emission level of 1.5 g/mlle, an average of 1% of
the exhaust gas must be rectrculated with proportional modulation, but reduced to
zero flow at full load. A large oxidation catalyst will also be required for the
vehicle to achieve the primary emission levels of 0.41 g/mlle HC and 3-4 g/mlle
CO. The catalyst position will be underneath the vehicle floor and must be placed
as close as possible to the exhaust manifolds. In order to generate high exhaust
gas temperatures following a cold start, the exhaust manifolds must have a low
12
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thermal Inertia, so that the catalyst may light off.
Fuel consumption and emission estimates were made by careful extrapolation
of published data from tests on various PROCO engines. Emissions durability of
this vehicle Indicated that the primary target emissions should be maintained for
at least 25,000 miles. The most critical emissions durability factor Is the HC
catalyst conversion efficiency required to hold the HC result to below 0.^1 g/mlle.
The test results recorded on the PROCO Capri by SWR1 were taken into account
In making the noise estimation,
Design Notes
The choice of a bore/stroke ratio of 1 compared to a bore/stroke ratio of
1.2<) on the Ford 1.141 engine was made because a smaller bore will give better
combustion control and combustion efficiency. Moreover, a smaller bore will give
lower noise so the bore/stroke ratio of 1 Is therefore a compromise with adequate
breathing and engine height,
The engine Installation drawing (Fig. 4) shows the Important engine package
dimensions. Cylinder centres at 1.17 x cylinder bore are controlled by the casting
core thickness of the water jacket between the bores.
Cylinder head and manifold arrangement
Swirl type Inlet ports, fuel Injectors and push rods are positioned on the
Inboard side with the exhaust ports and spark plugs on the outboard side. The
cylinder head layout Is shown In Fig. $• Spark plugs and fuel Injectors are
retained by the use of screwed sleeves.
The exhaust manifolds are placed outboard to give cross-flow porting and the
best: cylinder head layout with four retaining cylinder head studs surrounding each
bore:. The manifolds are then turned downwards from the cylinder ports and do not
Increase the width of the engine significantly.
Combustion system and breathing considerations
The combustion chamber which Is concentrically placed In the piston crown Is
symmetrical about the vertical bore centreline. The piston Is designed to have
about 60% squish area. Fig. 5 shows the combustion chamber, spark plug and fuel
Injector layout. The spark plug and Injector relative positions are essentially
the same as used on the Ll^l PROCO engine so that the spark plug gap Is located
just: above the conical spray of Injected fuel.
In-cyllnder air swirl Is Imparted by means of a helical type of swirl-
generating Inlet port, as Indicated In Fig, 5, The PROCO method of Imparting
swirl Is to use an Intake port having a directed Intake restriction In the shape
of a crescent but helical Inlet ports give a superior volumetric efficiency, The
In-cyllnder swirl Is estimated to be 3 times the crankshaft speed.
The Inlet valve Inner seat diameter Is 3^,6 mm, about kQ% of the bore, which
a mean Inlet gas velocity of about 73,2 m/s C2*»0 ft/sec) at the rated speed.
Fuel Injector and control system
The fuel Injector Is the outwardly opening poppet valve type and Is identical
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to the one used on the Ford PROCO L141 engine. The poppet valve is designed to
vibrate at 2000-4000 Hz during Injection to Improve the fuel spray quality. The
valve opening pressure Is \1,2k bar.
A combined Injection pump and Ignition distributor unit, again identical to
that used on the Ford PROCO Ll4l engine, has been utilised. This unit Is
positioned In front of and at the same angle to the vertical as the left hand bank
(see Fig. 4), Because of the difficulty of positioning this unit with a suitable
drive, this was considered to be the best compromise solution to give the shortest
length of fuel pipes leading to the Inboard Injectors, The drive of this unit Is
by a mitre bevel gear off the front end of the camshaft, for timing accuracy,
Auxl1lary Drives
The camshaft, fuel pump/distributor unit and hydraulic pump are driven by an
Internal gear system. Gear drives give good reliability and accuracy of timing over
long periods with low noise.
Twin V-belt drives are used for the alternator and water pump and a single
V-belt for the air conditioning unit. A conventional skew gear drive Is used for
the oil pump,
Category I
(2) In-Llne 6. Naturally Aspirated - PROCO Engine - Primary Emission Target
lore
troke
lore/Stroke Ratio
1 splacement
ompression Ratio
'ower
IMEP
lax. BMEP
lax. Torque
'orque Back-up
ower/Unlt Displacement
lax. Piston Speed
lax. Cylinder Pressure
96 mm
96 mm
1.0
4,15 L
Mil
96.5 kW
at 66,7 rev/s
6,95 bar
8,8 bar
293 Nm
26%
23.3 kW/L
12.8 m/s
65.5 bar
3.78 In
3.78 in
254 In3
129 bhp
at 4000 rev/mln
101 lbf/In2
128 lbf/In2
216 Ibf.ft
0.508 bhp/!n3
2520 ft/mln
950 Ibf/ln2
Con-rod
Distance between centres, L
Ratio of L to crank throw (r)> r
14
mm
6,0 In
3.17
-------
Cylinder bore spacing 1.17 x cylinder bore
Package
Engine length 995mm 39.16 in
height 638 mm 25.12 In
width 528 mm 20.8 In
box volume .335 m3 11.84 ft3
weight 263 kg 580 Ib
Predicted CVS-CH Results
Fuel Economy 18,4 mlles/U,S. gallon
Fuel Consumption 12.74 L/100 km
HC ) 1.0/0.15 g/mlle
) Baseline/Controlled
CO ) 8.0/0.8 g/mlle
NO Controlled 1.3 g/mlle
X
Estimated noise 75 dBA
Predicted Performance, Economy, Emissions, and Noise
The specification for a target power output of 96 kW (128 bhp) was met by an
In-line 6 cylinder engine of 4.15 litre (254 In^). The method of performance
calculation used for the previous PROCO V~8 configuration was applied and the
estimated performance curve of this engine Is shown In Fig, 7. Fuel consumption,
exhaust emission and noise predictions were also made, using the previous methods.
The same exhaust emission control methods as proposed for the V-8 configuration
will be necessary. That Is, an average rate of 1% EGR with proportional mod-
ulation, reducing to zero flow at full load, plus a single oxidising catalyst
fitted Into the exhaust system underneath the vehicle floor. Emissions durability
sho'uld be satisfactory to hold the exhaust emission levels to within the primary
target for at least 25,000 miles.
Design Notes (Figs. 8, 9)
The bore/stroke ratio of I was chosen, common to the V-8 configuration and
for the same reasons.
The engine Installation drawing (Fig, 8) shows the Important engine package
dimensions" and a cross-sectional arrangement of this engine Is shown In Fig. 9.
Cylinder centres at 1.17 x cylinder bore controlled by casting core thickness of
the water jacket between bores.
Cylinder Head and Manifold Arrangement
Cylinder head layout as for previous W8 configuration. Cross-flow porting
gives more latitude to the porting, spark plug and Injector layout than a unl-slded
-------
port arrangement, An air throttle is used to control the inlet air quantity during
part load operation.
Combustion system and breathing considerations
The layout of the Injector, spark plug and valves in relation to the com-
bustion chamber Is practically Identical to the previous V-8 configuration.
Helical Inlet ports are used to impart the In-cyllnder air swirl,
. The Inlet valve Inner seat diameter Is 39.8 mm, !»!',5% of the bore,, which
gives a mean Inlet gas velocity of 80 m/s at the rated speed. Although this high
velocity penalises the breathing at high speeds,, the target power is met and torque
back-up Is excellent,
Fuel Injector and Control System
The same fuel Injector and a similar fuel pump/distributor unit as described
for the previous V-8 configuration has been schemed for this engine, The fuel
pump/distributor unit Is mounted in a vertical position at the front of the engine
and driven by a mitre bevel gear from the end of the camshaft for accuracy of
tIming.
Auxi1lary Drives
An Internal gear system Is used to drive the camshaft, fuel pump/distributor
unit and hydraulic pump, Twin V-belt drives are used for the alternator and water
pump and a single V-belt drive for the air conditioning unit, All the above
auxiliaries are mounted on the front of the engine as Indicated in Fig- 8
Category 1
(3) V-8 Naturally Aspirated - PROCO Engine - Secondary Emission Target
Bore 9** mm 3,7 in
Stroke 3k mm 3.7 in
Bore/Stroke Ratio 1 .0
Displacement 5.25 L 320 in^
Compression Ratio llcl
Power 122 kW 163 bhp
at 66.7 rev/s at ^000 rev/min
BMEP 7 bar 101 5 lbf/in2
Max. BMEP 8.8 bar 128 lbf/in2
Max. Torque 365 Mm 270 Ibf.ft
Torque Back-up 13%
Power/Unit Displacement 23^ kW/L 0.509 bhp/ln3
Max. Piston Speed 12.6 m/s 2^70 ft/min
16
-------
Max. Cylinder Pressure
65.5 bar
950 Ibf/in
Con-rod
Distance between centres, L
L,
Ratio of L to crank throw (r), r
Cylinder bore spacing
Package
Engine length
height
width
box volume
weight
Predicted CVS-CH Results
Fuel Economy
Fuel Consumption
162.6 mm 6.** in
3.45
1.17 x cylinder bore
800 mm
609 mm
622 mm
0.303 m
259 kg
3
31.5 in
2k in
24.5 In
10.7 ft
570 Ib
3
HC )
) Baseline/Controlled
CO )
NO Controlled
Estimated Noise
16.5 miles/U.S. gal Ion
14.2 L/100 km
2.5/0.25 g/mile
12.0/0.8 g/mile
0.37 g/mlle
72.5 dBA
Predicted Performance. Economy. Emissions and Noise
In order to offset the power loss due to the extra EGR quantities and so
maintain satisfactory vehicle propulsion during the CVS-CH driving cycle, an
Increased engine swept volume over that proposed for the primary emission target
engines will be required. Computer calculations Indicated that an engine swept
volume of 5.25 litre (320 in3) would be sufficient for this purpose.
The BMEP developed by the engine when operating with the high EGR rates
during the CVS-CH driving cycle was assumed to be between 4.8 and 5.8 bar
(70-&5 Ibf/Irn) depending on speed, based on Ford's published figures from their
L141 PROCO engine. The engine capacity of 5.25 litre ensures that the maximum
BMEP of 5.8 bar should not be exceeded during the CVS-CH driving cycle. Predictions
of the engine full throttle performance were made using the same method as described
for the V-8 primary emission target engine and the estimated performance curve is
shown In Fig. 10. It is clear that since ,the EGR Is modulated to zero rate at full
load, the maximum power Is well above the target of 96 kW, at 125 kW and therefore
road performance will be more than adequate.
To meet the stringent secondary NO emission target of 0.4. g/mile higher EGR
17
-------
rates of about 20-25% at light loads modulated to 15% at the maximum CVS test loads.
These EGR rates will increase the engine HC emissions such that a single catalyst
would not give a satisfactory durability.
Two oxidation catalysts, fitted in series, underneath the vehicle floor, is
considered to be the most convenient method to control the HC and CO emissions.
Low thermal inertia exhaust manifolds will also be necessary. Emission durability
to meet the secondary emission target levels of 25,000 miles driving, cannot be
assured at the present moment, but should be possible after further catalyst and
engine development.
Design Notes
The necessary engine swept volume of 5.25 litre was best met with a V-8
engine configuration.
The same reasoning was used in the determination of a bore/stroke ratio of
unity as was applied to the earlier configurations within this category. In other
words, the minimum bore size compatible with the combustion system was chosen to
give good combustion control.
The cylinder head and general engine layout Is basically identical but
proportionally increased in size to that used for the V-8 configuration schemed to
meet the primary emission target. For this reason only the installation drawing,
Fig. 11, has been Included to allow an assessment of the engine configuration.
Auxiliary drive systems and installation positions also follow those proposed
for the previous V-8 configuration.
18
-------
ENGINE CONFIGURATIONS WITHIN CATEGORY 2
The Texaco TCCS has undergone a considerable development programme for
automotive applications and was therefore chosen for this configuration study,
Deutz have a system with a similar arrangement to Texaco but not developed so
extensively, whilst CurtIss-Wrlght have applied their system to a rotary engine.
A rotary engine with the Curtlss-Wrtght system has also been configurated.
To meet the primary emission target, three engine builds have been schemed:-
(1) V-8, 5.4 L Naturally Aspirated, TCCS engine.
(2) 1-L 6, 4.16 L, Turbocharged, TCCS engine.
(3) Rotary, 2 bank, 5-5 L, CurtIss-Wrlght engine.
Only one engine has been schemed to meet the secondary emission target::
(4) V-8, 5-87 L, Turbocharged, TCCS engine.
Category 2
(1) V-8 Naturally Aspirated - TCCS Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Compression Ratio
Powe: r
BMEP
Max. BMEP
Max. Torque'
Torque Back-up
Poweir/Unit Displacement
Max. Piston Speed
Max. Cylinder Pressure
Con-rod
Distance between centres, L
L,
Ratio of L to crank throw (r) r
Cylinder bore spacing
95 mm
95 mm
1.0
•5.* I
10:1
96 kW
at 66.7 rev/s
5.3 bar
6.5 bar
at 29 rev/s
280 Nm
23%
17.8 kW/L
12.7 m/s
51.4 bar
162.6 mm
3-74 in
3-74 in
330 in3
128 bhp
at 1*000 rev/min
77 Ibf/in2
Sk lbf/in2
at 1740 rev/mln
206 Ibf.ft
0.388 bhp/ln
2500 ft/mln
745 lbf/ln2
3
6.
in
1.23 x cylinder bore
19
-------
Package
Engine length 823 mm 32.4 in
height 658 mm 25-9 in
width 622 mm 2k.5 in
box volume 0.337 m3 11.9 ft
weight ' 273 kg 600 Ib
Predicted CVS-CH Results
Fuel Economy 17 miles/U.S, gallon
Fuel Consumption 13.8 L/100 km
HC ) 2.5/0.3 g/mile
) Baseline/Controlled
CO ) 10/1.5 g/mile
NO Controlled 0.8 g/mile
/\
Estimated Noise 70.5 dBA
Predicted Performance. Economy. Emissions and Noise
The relatively low bmep characteristic of this engine required a large engine
swept volume of 5.4 litre (330 In3) in order to achieve the target power output,
96 kW (128 bhp) at 67 rev/s (4000 rev/mln). An In-line 6, naturally aspirated
version was not considered to be attractive, due to high piston speeds.
Performance calculations were made using the following method. The maximum
power air/fuel ratio and Indicated specific fuel consumption for the TCCS process
had first to be established. Since the TCCS process is smoke limited, the maximum
power air/fuel ratio Is a function of the engine smoke level. Information
extracted from reports by Texaco and Toyota on the L141 engine is shown in Fig. 12.
Apparently, the Toyota engine reached a Bosch No. 4 smoke limit at a leaner air/
fuel ratio than the Texaco engine. Therefore, the power output was lower. At a
Bosch smoke number of 2-2J, which is realistic for automotive applications, the
power output of the Texaco engine was reduced by about 10%. Presumably the per-
formance of the Toyota engine would be compromised by a similar factor at this
smoke level. However, It was decided that the more optimistic Texaco results should
be used for this prediction
Indicated specific air consumption was calculated from air/fuel ratios multi-
plied by indicated specific fuel consumption, Fig. 13, and extrapolated to 1000 and
4000 rev/min. The volumetric efficiency was estimated by calculation of the gulp
factor. Unity gulp factor was found to be at 5000 rev/min. A correlation exists
in Taylor and Taylor (The Internal Combustion Engine, publisher International
Textbook Company) between gulp factor and volumetric efficiency, so these values
were extracted and Increased by 1%. The values in Taylor and Taylor refer to a
gasoline engine, and If fuel Is absent from the Induced air, the volume occupied by
the fuel vapour can be replaced b,y air. Engine power was then calculated from:-
20
-------
IMEP = Volumetric efficiency ^_
Indicated specific air consumption
Next, the friction levels of three Ll^l engines were inspected, Fig. 1*». At
2500 rev/mln and 3000 rev/min the FMEP was lower than for a typical European A
cylinder gasoline engine. This was surprising, In view of the additional motoring
loss of the fuel Injection equipment. However, the late closing of the inlet valve
of the Ll*»1 and the low volumetric efficiency at higher speeds may result In a
lower effective compression ratio. This would reduce the compression expansion
motoring loss. In the predicted engine, the inlet valve opening period has been
reduced, so one would expect the friction levels to be similar to the typical k
cylinder engine. Thus, the BMEP of the predicted engine was calculated from the
IMEP above, and the average friction levels of the Ll^l engines.
The resulting performance curves for this engine are shown in Fig. 15, and the
target power of 96 kW (128 bhp) is reached at 66.7 rev/s. It Is clear that the
specific power output of this engine Is low at 17.8 kW/l?tre (.39 bhp/ln3) due to
the lean operating air/fuel ratio, at the smoke limit of Bosch No. 2£-l£.
This category of stratified charge engine inherently gives high baseline HC
emissions and for this reason there will be a high dependence on oxidising
catalysts in order to achieve the HC primary emission target of 0.^1 g/mile. It is
considered that for all engine configurations within this category, two catalysts,
connected In series, will be necessary to control the HC emissions. This catalyst
arrangement will automatically control the CO emissions satisfactorily. Ricardo
did not propose a thermal reactor plus an oxidising catalyst, as Texaco have done
to achieve the secondary target, since it is considered less economic to produce
two different exhaust control components.
The exhaust pipe from each engine bank will require it to be joined as close
to the engine as Is conveniently possible to allow an early entry into the first
catalyst. Low thermal inertia exhaust manifolds, preferably Insulated, will also
be necessary to avoid exhaust gas-temperature losses.
A level of about 10% EGR modulated during the light to medium loads of the
CVS-OH driving cycle Is recommended. This relatively high EGR rate will reduce
the NO emission more than necessary but is considered as the best method of in-
creasing the exhaust gas temperature for catalyst operation. EGR should be mod-
ulated to zero rate at full load.
It is thought that there may be problems In maintaining the HC levels to
within the primary target of O.*»l g/mile. However, with the large volume of two
catalysts the target emission levels should be held for a period of 25,000 miles.
A good NO emission durability should result and no problems in meeting the NO
emission target for 50,000 mile periods are envisaged. x
Deslcm Notes (Figs. 16. 17. 18)
This engine was designed in a conservative manner following many stipulated
procedures set down by Texaco for guidance related to engines having the TCCS com-
bustion system.
Having calculated the engine swept volume of S.k litre (330 in ), the
mathematical procedures prescribed by Texaco were employed to optimise the bore/
stroke ratio to 1 and compression ratio to 10:1.
21
-------
The cylinder centres at 1.23 x cylinder bore are wider than standard American
gasoline engine practice. The wide cylinder spacing was found necessary in order
to allow sufficient space for the necessary porting and combustion system layout.
A penalty In extra engine length results.
The engine Installation drawing, Fig. 16, shows the important engine package
dimensions. Fig. 17 shows the cylinder head layout and Fig. 18 is a cross-
sectional arrangement.
Cylinder Head and Manifold Arrangement
The porting layout of the TCCS combustion system employing high swirl inlet
ports was best achieved with a cross-flow arrangement.
Five retaining cylinder head studs surrounding each bore were found to give
the greatest design scope for the porting layout. Fuel injectors and spark plugs
were on the outboard (exhaust) side and pushrods on the inboard side.
Combustion System and Breathing Considerations
The TCCS combustion system was employed which comprises a toroidal type,
deep bowl combustion chamber in the piston. The piston bowl diameter, being 58%
of the bore, was designed to give Texaco swirl levels of 3.5 x engine speed and
7-5 x engine speed at the end of Induction and at t.d.c. respectively.
The fuel injector and spark plug positions follow close.ly those recommended
by Texaco such that the spark plug gap is on the edge of the fuel spray, as can be
seen in Fig. 17. A special ignition system, the Texaco Transistorised Ignition
system, provides a high energy and long duration spark. Furthermore, the spark
plug Is sleeve mounted Into the cylinder head at a pre-determlned radial position
to ensure that Its earth electrode does not Interfere with the fuel spray directed
towards the ignition source.
High swirl Inlet ports specially developed by Ricardo have been utilised in
place of the Inlet ports stipulated by Texaco. The Ricardo Inlet ports should
give improved volumetric efficiency and performance, In particular at high speeds.
In other respects the Texaco recommendations on inlet valve dimensions and timing
were follows.
Valve lift/Inner seat diameter 281
Inner seat diameter/cylinder bore 38.5%
Inlet valve opening period 232°
The Inlet valve Inner seat diameter of 36.6 mm gives a mean inlet gas speed
of 68.8 m/s (226 ft/sec) at the rated speed of 67 rev/s. A high valve offset of
13 nun from the cylinder bore centre has been employed in order to make space for
the spark plug and fuel Injector layout.
Fuel Injector and Control System
The fuel Injector Is of the inward opening pintle type but with a flat
pintle sealing face as developed specifically for the TCCS system by Texaco. A
distributor type of fuel injection pump, again as used by Texaco, has been mounted
between the cylinder banks and Is gear driven from the front of the crankshaft.
22
-------
The fuel pipes are unavoidably long due to the position of the outboard Injectors.
Auxi1lary Drives
The camshaft, fuel Injection pump and Ignition distributor are gear driven
from the front of the crankshaft, the Ignition distributor having a separate skew
gear drive from the gear on the camshaft nose. Gear drives were chosen for
accuracy of timing over long periods combined with reliability and low noise. A
conventional skew gear driven oil pump is used.
Twin V-belts drive the alternator, water pump and hydraulic pump and a single
V*bel!t drives the air conditioning unit. Fig. 16 shows the Installation layout
of the above auxiliaries.
Category 2
(2) In-Llne 6, Turbocharged - TCCS Engine - Primary Emissions Target
Bore
Stroke
Bore/Stroke Ratio
Di splacement
Compression Ratio
Power
BMEP
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
Max. Cylinder Pressure
Con-rod
Distance between centres, L
L,
Ratio of L to crank throw (r), r
Cylinder bore spacing
Package
Engine length
96 mm
96 mm
1.0
1».16 L
9:1
96 kW
at 66.7 rev/s
6.9 bar
3.78 In
3.78 in
3
9.0 bar
at *»
298 Nm
15. U
23.1 kW/L
2520 m/s
71 bar
rev/s
25*» In
128 bhp
at 4000 rev/min
100 lbf/ln2
130 lbf/in2
at 2500 rev/min
210 Ibf.ft
151.1 mm
3.15
1.16 x cylinder bore
0.504 bhp/in
12.8 ft/min
1030 lbf/in'
5.95 in
3
981 mm
38.62 in
23
-------
height 610 mm 2^.0 In
width 578 mm 22.?6 in
box volume 0.3^6 m 12.2 ft
weight 260 kg 572 Ib
Predicted CVS-CH Results
Fuel Economy 17 miles/U.S. gallon
Fuel Consumption 13.8 L/100 km
HC ) 2.0/0.22 g/mile
) Baseline/Controlled
CO ) 10/1.5 g/mile
NO Controlled 0.8 g/mile
Estimated Noise 71 dBA
Predicted Performance, Economy, Emissions and Noise
This turbocharged engine was schemed to evaluate a power plant with a higher
specific power output than the previous naturally aspirated version. As a result
of turbocharging the engine swept volume required to achieve the same target per-
formance level is reduced from'S.** litre (330 In3) for the NA version to 1».16
litre (25^ In3).
A target of 8.95 bar BMEP at 2000 rev/min was adopted as the starting point
from which performance calculations were made. This condition implies a boost
density ratio of 1.27. A typical compressor curve was obtained from a turbocharger
manufacturer, and an empirical Ricardo relationship between boost pressure and
engine speed used to predict the boost density ratio over the remainder of the
engine speed range, Fig. 19.
The fuel pump discharge characteristics had to be tailored to prevent over-
loading the engine structure. A simple formula was derived for the maximum
cylinder pressure based on the constant volume cycle, where the values of the ratio
of specific heats for the gas were based on polynomials of gas temperature and
mixture strength. Air/fuel ratios were calculated for each engine speed above
2000 rev/min (also shown in Fig. 19), assuming that the maximum cylinder pressure
did not exceed that at 2000 rev/min. These calculations indicated that the fuel
delivery per injection should decrease by 33% in a linear manner between 2000 and
4000 rev/min. Fuel injection pumps do not follow this trend naturally, so a speed
modulated cut-off device would be required. An air/fuel ratio of 19:1 at 2000
rev/min, corresponding to Bosch smoke No. 2, was maintained. During engine
accelerations, the finite response time of the turbocharger could cause the air/fuel
ratio to drop below 19=1, and the engine would emit a higher smoke level.
L141 engine results were cross-plotted as indicated specific fuel consumption
against air/fuel ratio, and this relationship was assumed to be applicable to the
turbocharged version, see Fig. 20. Next, the appropriate fuel consumption was
obtained at the air/fuel ratio corresponding to each engine speed. Finally, IMEP
was calculated by the following formula:-
2k
-------
Density Ratio x Volumetric Efficiency
= Air Fuel Ratio x Indicated Specific Fuel Consumption
The friction levels of a typical European gasoline engine were used to
calculate the brake performance curves shown in Fig. 21. This was an optimistic
friction figure, since the maximum cylinder pressures were calculated to be about
15% above standard European gasoline engine practice, and about 30% above U.S.
gasoline engine practice.
Specific engine power at 23.6 kW/litre (.515 bhp/in ) is significantly
improved by comparison to the previous naturally aspirated engine together with
a lower estimated engine weight of 260 kg (572 Ib).
There Is a high dependence on oxidising catalysts to reduce the HC emissions
to the primary target of 0.^1 g/mile. Two catalysts fitted in series, downstream
of the turbocharger, will be necessary. The exhaust manifold is recommended to be
of fairly large volume, Insulated and with a low thermal Inertia. This type of
exhaust manifold should reduce exhaust gas heat losses and so assist the catalyst
oxidation efficiency. The CO emissions should be automatically controlled with the
above exhaust system.
A 10% rate of EGR is recommended during the light to medium loads encountered
during the CVS-CH test cycle in order to maintain sufficiently high exhaust
temperatures for catalyst operation, the EGR rate being modulated to zero rate at
full load. The NO emissions should be adequately low with these EGR rates.
x
The catalytic problem of maintaining the HC emissions to within the primary
target will be the critical emission durability factor, as for the previous con-
figuration. However, there should be no problems in maintaining the CO and NO
emission to within the respective target levels for a 25,000 mile period.
Design Notes (Figs. 22, 23. 2k)
This engine was designed to be highly boosted by turbocharging, resulting in
higher cylinder pressures than normally associated with gasoline engines and the
crankshaft was therefore made more rigid to cope with the higher loadings. Cylinder
spacing at 1.16 x cylinder bore was controlled by the casting core thickness of the
water jacket between bores.
It should be noted that the air filter has not been included in the engine
package size since in this case It would be more conveniently mounted on the vehicle
than on the engine. Fig. 22 shows the important engine package dimensions.
Cylinder Head and Manifold Arrangement
The fitting of a turbocharger made a uni-sided porting arrangement the most
convenient. High swirl (helical) Inlet ports are employed with a four stud
cylinder head pattern as the best solution for the porting layout. This also allows
more compact cylinder spacing than the previous TCCS V-8. Pushrods are on the
manifold side and spark plugs plus Injectors on the other side. The Injectors are
mounted with single bolt clamps and the spark plugs with screwed sleeves.
Combustion System and Breathing Considerations
The TCCS combustion system was employed as shown in Fig. 23. Combustion
chamber and valve proportions are substantially the same as recommended for the
25
-------
naturally aspirated engine, as is the Ignition system. The fuel injector and
spark plug specification and relative positions are also the same.
The compression ratio is
The high swirl Inlet ports mi
but these should still lie wi
times engine speed at t.d.c.
the Inlet valve diameter and
would be reduced to about 7,
the higher kinetic energy of
transient characteristics of
operation and exhaust manlfol
reduced from the naturally aspirated version to 9:1-
ght Increase the swirl levels with pressure boosting
thin the swirl levels stipulated by Texaco of 7 to 10
An alternative to this approach would be to reduce
Increase the exhaust valve diameter. The swirl level
but additional turbine boost could be achieved from
the exhaust gas. This approach could improve the
the turbocharger, but involves a difficult matching
d layout.
Fuel Injector and Control System
Fuel Injectors were identical to those for the naturally aspirated engine.
A 6-cyllnder version of the distributor type fuel injection pump is mounted
horizontally on the opposite side to the manifolds in a position to give the
shortest possible fuel pipe lengths.
Auxl1lary Drives
An Internal gear drive system is used to drive the camshaft, fuel Injection
pump and hydraulic pump. Conventional skew gear drives are used for the Ignition
distributor and oil pump. Vee-belt drives are used for the alternator, water
pump and air conditioning unit. Fig. 22 shows the Installation layout of the above
auxiliaries.
Category 2
(3) Rotary, 2 Bank - Curtiss-Wright Engine - Primary Emission Target
Generating Radius
Rotor Width
Eccentric! ty
Displacement
Compression Ratio
Power
BMEP
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Cylinder Pressure
122 mm
79 mm
18. 4 mm
5.5 L
8.5:1
97 kW
at 83 rev/s
6.3 bar
7.** bar
at 56 rev/s
214 Nm
17.4%
17-6 kW/L
42 bar
4.8 in
3.11 In
0.724 in
336 in3
130 bhp
at
91.5 lbf/i
107 Ibf/in
at
158 Ibf.ft
0.387 bhp/
609 Ibf/in
at 5000 rev/min
at 3360 rev/min
26
-------
Package
Engine length 523 mm 20.6 in
height 660 mm 26.0 in
width 695 mm 27-35 in
box volume 0.2^ rrT 8.5 ft3
weight - 150 kg 330 Ib
Predicted CVS-CH Results
Fuel Economy l^.O miles/U.S. gallon
Fuel Consumption 16.7^ L/100 km
HC ) 3.0/0.3 g/mile
) Baseline/Controlled
CO ) 15.0/0.8 g/mile
NO Controlled 1.0 g/mile
/\
Estimated noise 71.0 dBA
Predicted Performance. Economy, Emissions and Noise
Performance calculations were based on results obtained by Curtiss-Wright to
predict that a swept volume of 5.5 litre (336 In3), the swept volume being a total
of all rotor lobes, would be required In order to achieve the required target
performance.
The brake performance of this engine is ultimately limited by smoke emission,
however, Curt!ss-WrIght have not included smoke levels with their published power
curves. For this reason RIcardo limited the maximum bhp at each engine speed to
the smoke limits of Bosch No. 2.5 at 25 rev/s (1500 rev/mln) to Bosch No. 1.5 at
the rated speed of 83 rev/s (5000 rev/min). To make these calculations possible,
the ratio of smoke limited bhp divided by the bhp at the maximum economy point as
calculated for I.D.I, dlesel engines, was assumed to hold true for this engine.
Applying the smoke performance controlling factor to the published power output,
throughout the engine speed range of the CurtIss-Wrlght RC2-60U10 engine, enabled
the performance prediction to be made directly, see Fig. 25.
The engine specific power output, in terms of engine weight, Is excellent
compared with the naturally aspirated V-8 TCCS engine since the engine weight is
estimated at just 150 kg (330 Ib). Package size is also relatively small in
terms of volume.
It is worth noting that If the lobe sealing technology can be improved, a
better economy than that estimated could be achieved.
This engine version will produce higher baseline HC emissions, than the
previous TCCS configurations considered within category 2 and because of the low
exhaust gas temperatures It will be difficult to control both the HC and CO
emissions using catalysts without a specialised exhaust manifolding from the engine.
27
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The exhaust manifold must have a low thermal Inertia and also be very well In-
sulated throughout Its length In order to maintain the exhaust temperature high
enough for catalyst operation. The compact exhaust porting and close fitted
manifold and also the Inherent Inefficiency (I.e. internal EGR due to seal leakages)
will help In this respect. Two oxidation catalysts will be needed, fitted In
series and as close as possible to the exit from the exhaust manifold.
There is a high dependence on the catalysts to reduce the HC and CO emissions,
particularly the former emission, and maintaining the primary emission target for
a 25,000 mile period may prove difficult. No problems are envisaged In keeping to
within the NO target of 1.5 g/mile and the addition of EGR is not necessary,
/\
Design Notes
Design features follow conventional ^-stroke form having two-lobe epitrochoid
chambers and three-lobe rotors. The basic engine construction was based on Wankel
rotary combustion engine practice.
The Installation drawing, Fig. 26 indicates the important engine package
dimensions and the Cross and Longitudinal sectional drawings on Fig. 27 show
details of the engine construction and combustion system layout.
Manifold Arrangement
The exhaust manifold is bolted directly to the rotor housing, has low thermal
Inertia and Is well insulated to maintain high exhaust gas temperatures. The Inlet
manifold Is mounted directly above the exhaust manifold to suit peripheral
(radial) ports.
Combustion System and Breathing Considerations
The shape of the combustion chamber recess within each rotor flank follows
closely that proposed by Curtlss-WrIght. In plan view the recess Is asymmetrical,
there being a leading edge pocket on each side of the rotor. This type of recess
is known as a "beetle" type. In a section view the leading pockets of the recess
are deeper than at the trailing edge in'order to achieve the required time
distribution of air mass past the fixed fuel spray envelope.
Two pairs of closely coupled spark plugs and fuel injectors per rotor are
recommended. This arrangement should give thorough mixing and consistent firing
properties which will result in the best possible air utilisation. This Is normally
the critical aspect of the stratified charge rotary engine.
The location of the injector/spark plug intersection point Is 16.5° to the
epitrochoid minor axis in the opposite direction to rotor rotation. The included
angle between each injector and spark plug Is ^0° with Injectors In the trailing
posi tlon.
The spark plugs have a high heat range and conventional Wankel type electrodes.
They are sleeve mounted into the rotor housing, The Ignition system produces long
duration and high energy sparks and the distributor contains two rotors, each rotor
supplying the pair of spark plugs for a rotor bank.
The cavity into which both the electrodes and nozzle tip protrude has been
designed for minimum lost volume. Furthermore, the combined width of two cavities
per rotor has been kept small to prevent excessive by-pass leakage around the apex
seals.
28
-------
Peripheral (radial) inlet ports were preferred to side (axial) inlet ports
due to the comparative gains in volumetric efficiency. Performance will not be
lost at low speed/low power conditions by the normal effects of valve overlap
since fuel Injection occurs after the intake port closes.
The intake port was designed to close at 80° BTDC (rotor) and exhaust port to
open at 72° ATDC (rotor). These timings were fixed as design parameters for sat-
isfactory running. The other end timings were arranged for a minimum valve over-
lap period by making the ports narrow In the rotational sense.
Intake and exhaust ports are split into two passages within the rotor housing
by-a bridge piece giving column strength to the rotor housing. Each individual
port passage within the housing also reduces in area by about 20% in a direction
towards the engine In the Interests of stable flow characteristics.
Fuel Injector and Control System
The fuel Injector nozzles are flush mounted, the injection spray pattern
having mult! sprays with a restricted angle (shower head type) to prevent spray
Interference between the two adjacent Injectors. A distributor type of Injection
pump Injects Into two fuel lines, each line Is then divided for connection to the
two injectors per bank.
Dual Injectors per rotor bank were chosen so as to ensure satisfactory torque
output through the speed range.
Auxl1lary Drives
Fig. 26 shows the Installation layout of the auxiliaries. Fuel injection
pump and Ignition distributor are conveniently positioned close to the combustion
chamber. Both these units are driven by a toothed belt tensioned by a jockey
pulley. Toothed belts are light, inexpensive, accurate and quiet.
The alternator and water pump are driven by twin V belts and the air con-
ditioning unit by a single V belt. All the above drive systems are taken from the
front of the engine.
The oil pump Is driven by an internal gear system, the final drive also used
to drive the hydraulic pump which is external to the engine.
Detail Points
Eccentric Shaft Bearings - Bearing loadings were calculated to cover gas loads
only. The loading of the bearing.at the eccentric shaft/end rotor housing was
calculated at 373 bar (5^*00 Ibs/in2) as being equivalent to the maximum loading
with one bank firing neglecting the small effect of the second non-firing bank.
Bearing pressure of the eccentric shaft/rotor was 2kB bar (3600 Ibs/in2).
Conventional thin-walled bearing liners are proposed for the latter bearings. An
intermediate bearing within the dividing rotor housing was considered unnecessary
because of the high stiffness of the eccentric shaft.
Rotor - Material: cast Iron for good hot strength and low thermal expansion. I-beam
type internal structure with thin internal ribs gives only a small sacrifice of
weight In comparison to aluminium. Oil cooled.
29
-------
Apex seals - Designed like an I-beam (material containing about 50% C and 50% Al)
so gases can activate the seal laterally instantaneously and so reduce the time lag
for good sealing. There is normally a time lag between the increase in the com-
bustion chamber gas pressure and the gas pressure under the apex seal. It is
thought that this will result In less 'chatter1, higher combustion pressures,
lower fuel consumption and lower emissions than the conventional design of seals.
Oil is metered into the combustion chambers, to aid sealing, by its addition into
the gasoline at the fuel Injection pump. This oil should be ash-free to prevent
catalyst poisoning and minimise engine deposits.
Rotor Housing - Aluminium casting with chromium plated epitrochoid surfaces for
optimum wear and sealing properties with apex seals.
Rotor housing assembly is rigidly constrained by 15 through bolts. Rotor end
housings are also aluminium castings.
Water Circuit
The Water pump is mounted on the front rotor housing discharging coolant into
the multi-pass axial flow coolant system. The multi-pass forced coolant flow Is
matched to the circumferential variation of heat input, the initial cold water
passes are adjacent to the hottest regions, i.e. coincident to the firing/expansion
rotor position.
The internal ribbing structure of the rotor housings through which the coolant
flows, I.e. the ties between the Inner and outer shells, are also multi-directional
to reduce thermal distortions and over-stressing of the trochoid surface.
Category 2
(4) V-8, Turbocharged - TCCS Engine - Secondary Emission Target
lore
itroke
lore/Stroke Ratio
'I splacement
ompresslon Ratio
'ower
101 mm
92 mm
1 .08?
5.87 L
9:1
135 kW
3.96 in
3.64 in
358 In3
181 bhp
BMEP
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
at 66.7 rev/s
6.9 bar
9.0 bar
at 41 rev/s
423 Nm
19%
23.0 kW/L
12.3 m/s
at 4000 rev/min
100 Ibf/ln
131 lbf/in2
at 2450 rev/mln
312 Ibf.ft
0.506 bhp/ln'
2430 ft/mln
30
-------
Max. Cylinder Pressure
Con-rod
Distance between centres, L
Ratio of L to crank throw (r),
Cylinder bore spacing
Package
Engine length
height
width
box volume
weight
Predicted CVS-CH Results
Fue1 Economy
Fuel Consumption
HC )
) Baseline/Controlled
CO )
NO Controlled
x
Estimated Noise
71 bar
. mm
1030 Ibf/in
6 i n
r 3-3
1 .2 x cyl Inder bore
845
645 mm
630 mm
0.343 m3
286 kg
14 miles/U.S. gallon
16.74 L/100 km
4.5/0.25 g/mlle
12.0/1.0 g/mile
0.33 g/mlle
72.5 dBA
33.3 in
25.4 in
24.8 in
12.1 ft
630 Ib
3
Predicted Performance, Economy, Emissions and Noise
If a naturally aspirated TCCS engine were to meet the secondary N0x emission
target of 0.4 g/mlle with EGR and combustion retard, then an engine swept volume
greater than 7.4 litre (450 in3) would be required. An engine of this size would
be unacceptable on the grounds of weight and size. A turbocharged TCCS engine of
5.87 litre capacity was considered to be a more promising approach.
Exhaust gases cannot be re-cycled from or to any points between the engine
and turbocharger without affecting the mass flow and efficiency of the turbocharger.
The gases must be extracted downstream of the turbine and re-cycled upstream of
the compressor such that the compressor passes a mixture of exhaust gas and air,
whose properties are not significantly different from those of air alone. There-
fore, the standard procedures for estimating turbocharger engine performance were
applied and the calculated boost density variation throughout the engine speed
range Is shown In Fig. 28.
Since a gulp factor of unity occurs at the same engine speed as in the
previous turbocharged In-line 6 TCCS engine, the volumetric efficiency will be
the same. In addition, assuming that the ISFC and smoke limited air/fuel ratio
31
-------
are not affected by engine size, and that, the turbocharger can be linearly scaled
to a larger engine, specific performance will be Identical with the previous
turbocharged engine at Its optimum settings.
One final problem remained, that of estimating the performance reduction due
to EGR and combustion retard. The only available data published by Texaco concerns
rear wheel torque at one engine speed. For a naturally aspirated sub-compact car,
rear wheel torque was reduced by 31% as the engine was de-tuned from maximum
economy to 0.4 g/mlle NO . In a similar exercise, a turbocharged Ll^l engine in a
jeep suffered a 23% loss In torque. In the light of this information, it was
assumed that the turbocharged engine would experience a 31% torque loss over the
complete speed range, due to EGR and retard. Engine swept volume was increased by
k]% over the primary target engine, to compensate for this torque loss, resulting
in an engine size of 5.8? litre (358 In3).
A further requirement for this engine is that it should be capable of
following the CVS-CH driving cycle In the test car with the EGR operating.
Calculations showed that for typical vehicle gearing, the car required 36.A kW
(^9 bhp) at 22.5 rev/s (1350 rev/mln) to meet the maximum acceleration rate of
the CVS trace (at the 193 second point), within the specified tolerance. The
predicted engine met this requirement, Fig. 29. It is clear that road performance
at full throttle, when the EGR Is modulated to zero rate, will be more than
adequate.
Two catalysts fitted In series are recommended to control the HC and CO
emissions. High rates of EGR will be required probably in the region of 25% over
much of the engine load/speed range, reducing to about 11% EGR during the maximum
acceleration conditions met during the CVS-CH test. EGR will be modulated to
zero rate at full load.
The high rates of EGR will increase the engine HC emissions but this Increase
will be offset by the higher exhaust gas temperatures to give extra manifold
oxidation plus Improved catalyst efficiency. It is possible that the higher exhaust
gas temperatures could make a thermal reactor a feasible solution together with a
single catalyst. However, the lower cost of having two common exhaust system com-
ponents, i.e. two catalysts, has been preferred.
Catalyst efficiency and Its durability factor should be satisfactory for
25,000 mile periods with a reasonable safety margin.
The NO emission control by EGR to achieve 0.40 g/mlle Is the most critical
aspect since the flame formed NO Is not significantly reduced by EGR (Ref. Gl
Blumberg). There is therefore a certain minimum NO mass emission which increases
with engine capacity, and also the mass flow of air through the engine. This
point Is particularly critical for unthrottled engines.
Design Motes
Fig. 30 shows the Installation drawing which is similar, apart from Increases
In size and the addition of the turbocharger, to that of the naturally aspirated
V-8 TCCS engine.
The five cylinder head stud pattern was adopted as for the latter V-8, which
when combined with the proposed inlet ports gave cylinder centres at 1.2 x cylinder
bore.
32
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Manifold Arrangement
Cross flow porting was arranged as for the previous V-8 TCCS configuration
with inboard inlet manifolds and outboard exhaust manifolds. The best solution
for turbocharging was thought to be with a single turbocharger mounted at the rear
of the engine banks with the compressor outlet discharging directly Into the
centrally placed plenum chamber. Several other arrangements Involving both single
and dual turbochargers were considered, but all had disadvantages.
Combustion System and Breathing Considerations
Most of the non-dlmenslonal valve and camshaft dimensions were retained from
the previous engines, but the piston cup diameter was reduced to 50% of the bore.
This was considered to be justifiable because of the slightly larger bore size of
this engine. It was found that the previously proposed Ricardo helical port for
the TCCS engine then gave a higher swirl level than that which was strictly
necessary. However, average diesel helical ports would not give sufficient swirl
performance. Using rig swirl measurements from each of these port types, a
hypothetical port was derived with a performance mid-way between these types. This
port not only met the swirl requirements; but also allowed some latitude for
shorter stroke engines, which improved the volumetric efficiency. The important
engine breathing parameters were:-
Valve lift/Inner seat diameter 28%
Inner seat diameter/cylinder bore 38.5%
Inlet valve opening period 232°
Average co-efficient of flow for _
hypothetical port (Texaco definition)
Average non-dimensional rig swirl n
(Texaco definition)
Swirl at end of induction 3-2 x engine speed
Swirl at TDC 8.0 x engine speed
Unity gulp factor 5000 rev/min
Fuel Injector and Control System
As for previous V-8 TCCS engine configuration
Auxi1iary Drives
Follow those proposed for previous V-8 TCCS engine.
33
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ENGINE CONFIGURATIONS WITHIN CATEGORY 3
The MAN-FM combustion system was chosen for application to the configuration
study in view of Its economy potential combined with low exhaust emissions. Even
so, this system has not yet been developed for automotive applications.
One engine build, a V-8, 5.05 L, has been schemed to meet the primary
emission target but no engines were schemed for the secondary emission target.
To achieve the secondary emission target EGR would be necessary and insufficient
published data was available to establish the effectiveness of applying EGR, or
the penalties Involved.
Category 3
V-8, Naturally Aspirated - MAN-FM Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Di splacement
Compression Ratio
Power
BMEP
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
Max. Cylinder Pressure
Con-rod
Distance between centres, L
L,
Ratio of L to crank throw (r), r
Cylinder bore spacing
Package
Engine length
height
width
93 mm
93 mm
1.0
5.05 L
15:1
96 kW
at 66.7 rev/s
5.7 bar
7.4 bar
at 33 rev/s
298 Nm
24.6%
19-0 kW/L
12.4 m/s
70 bar
3.66 in
3.66 in
3
309 In
128 bhp
at 4000 rev/min
82.5 Ibf/ln
107 Ibf/ln2
at 1980 rev/min
219 Ibf.ft
0.414 bhp/in3
2440 ft/min
1015 lbf/in2
156 mm 6.14 in
3.36
1.2 x cyli nder bore
745 mm
643 mm
640 mm
29.3 in
25.3 in
25.2 In
34
-------
box volume 0.307 m3 10.8 ft3
weight 300 kg . 660 Ib
Predicted CVS-CH Results
Fuel Economy 19.0 miles/U.S. gallon
Fuel Consumption 12.3 L/100 km
HC ) 0.8/0.3 g/mile
) Baseline/Controlled
CO ) 8.0/0.8 g/mile
NO Control led 1.0 g/mile
/\
Estimated Noise 72 dBA
Predicted Performance, Economy, Emissions and Noise
The engine swept volume was calculated to be 5.05L (309 in ) to achieve the
target performance. Performance predictions were based on extrapolation of the
MAN published data on FM engines operating on gasoline.
Insufficient data was available to indicate the smoke limited performance
throughout the engine speed range and the full throttle air/fuel ratio was
therefore limited to 18.7 throughout the speed range; this corresponds to Bosch
No. 1 to No. 1.5. The published values of indicated specific fuel consumption,
based on the results from several FM engines, were therefore adjusted to give the
indicated specific air consumption when smoke limited.
The prediction of volumetric efficiency was not possible from published FM
data and had to be made by extrapolation of Ricardo 'in house1 information on
the performance of high swirl inlet ports in larger bore (truck size) engines.
Imep was calculated from the indicated specific air consumption and volumetric
efficiency, then brake performance was obtained by taking the friction levels shown
in Fig. 3.10 into account.
The estimated performance curve for this engine is shown in Fig. 31. Analysis
of typical FM test bed bsfc curves indicates that the estimated fuel consumption
of the test vehicle should be excellent during the CVS-CH emission test cycle. The
moderate CR of 15 also contributes to good economy.
A single oxidising catalyst must be fitted underneath the vehicle floor and
as close to the engine as possible. Low thermal inertia exhaust manifolds are
also recommended. Catalyst durability should not be problematic for a period of
25fOOO miles since the uncontrolled engine emissions of HC will be comparatively
low at about 0.8 g/mile. Furthermore there should not be a durability problem in
holding the NO emission to within the primary emission target since no EGR is
necessary.
Design Notes (Figs. 32. 33. 3*0
The choice of a bore/stroke ratio of 1 was made in the interests of com-
pactness since this was the highest bore/stroke ratio recommended by MAN.
Furthermore, from the design point of view it gave a compromise between noise,
35
-------
breathing and engine height.
The major dimensions, design and rigidity of the crankcase and crankshaft
lie between conventional gasoline and diesel engine practice since the maximum
cylinder pressures are higher than for gasoline engines but not quite at diesel
engine levels. Cylinder centres resulted at 1.2 x cylinder bore.
An overhead camshaft arrangement was considered to offer considerable
advantages over a pushrod design in terms of cylinder head simplicity and
available space within the head for locating the high swirl inlet port required
for this combustion system. The resulting complexity of the front end timing
and auxiliary equipment drives, together with the engine length penalties incurred,
were however considered unsuitable features for passenger car application. A
single camshaft and pushrod design was therefore adopted.
Cylinder Head and Manifold Arrangement
This was Cross-flow porting with an inboard inlet manifold and employing
high swirl type inlet ports. A four cylinder head stud pattern was considered
to give the best head layout.
Fuel injectors are placed on the inboard side together with pushrods and
inlet ports. Spark plugs and exhaust ports are placed on the outboard side.
The spark plugs are retained by the use of screwed sleeves and the injectors
via clamps.
Combustion System and Breathing Considerations
The combustion chamber bowl is located within the piston crown and is
offset from the bore centre by k.S mm (equivalent to 0.0^58 x cylinder bore).
The relative positions of the injector and spark plug are essentially to MAN
requirements on opposite sides of the piston bowl, see Fig. 33. Conventional
ignition equipment and long electrode spark plugs are used.
The inlet valve inner seat diameter is 38.5 mm, about k\ ,k% of the bore,
which gives a mean Inlet gas velocity of about 72 m/s (236 ft/sec) at the rated
speed.
Fuel Injector and Control System
The fuel Injector is a single hole type which is similar to that fitted
to direct injection diesel engines. It has a single offset spray directed at
the adjacent wall of the piston cavity. Ricardo have Installed the nozzle into
an Injector body of 17 mm diameter as in some recent diesel engine design practice.
A gear driven
at the front.
Auxi 1 iary Drives
rotary Injection pump is positioned between the engine banks
The camshaft, fuel injection pump and hydraulic pump are driven by an
internal gear system. Gear drives give good rel iabi 1 i ty and accuracy of timing
over long periods with low noise. The distributor is skew-gear driven off the
camshaft and Is mounted In the vee at the rear of the engine.
Twin V-belt drives are used for the alternator and water pump and a single
36
-------
V-b<;lt for the air conditioning unit. A conventional skew gear drive is used for
the oil pump.
37
-------
ENGINE CONFIGURATIONS WITHIN CATEGORY
The VW combustion system was chosen for application to the configuration study
since, at the time of writing, it was the only one which had been tested in multi-
cylinder form and for which performance results were available. More recently the
Porsche system has been tested in mul t i -cyl inder form, however performance data is
still not sufficient to warrant a configuration study.
The same engine V-8 configuration of 3-67L was schemed to achieve both the
primary and secondary emission targets. Low NO emissions were achieved from the
secondary engine by applying EGR.
Category ^
(1) V-8, Naturally Aspirated - VW Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Compression Ratio
Power
BMEP
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
Max. Cylinder Pressure
Con-rod
Distance between centres, L
86 mm
79 mm
1 .1
3.67 L
8.5:1
96.5 kW
at 75 rev/s
7.1 bar
7.8 bar
228 Nm
9.8%
26.3 kW/L
11.8 m/s
58.6 bar
1^8.8 mm
at 66 rev/s
3-39 in
3.11 in
22k in3
129 bhp
at ^500 rev/mln
103 lbf/in2
113 lbf/in2
at 3960 rev/mln
168 Ibf.ft
0.576 bhp/in:
2330 ft/min
850 lbf/in2
5.7 in
>- /
Ratio of L to crank throw (r), r 3-67
Cylinder bore spacing
Package
Engine length 763 mm
height 610 mm
width 610 mm
1.17 x cy1i nder bore
30.05 In
2*».0 in
2k.0 in
38
-------
box volume
weight
Predicted CVS-CH Results
Fuel Economy
Fuel Consumption
0.28J* m
250 kg
3
10.0 ft
550 Ib
3
HC )
) Baseline/Controlled
CO )
NO Controlled
x
Estimated Noise
16.5 miles/U.S. gallon
14.2 L/100 km
1.8/0.23 g/mile
8.0/0.8 g/mile
1.0 g/mile
73 dBA
Predicted Performance, Economy, Emissions and Noise
The engine swept volume necessary to achieve the target vehicle performance
was calculated to be 3-67L (224 In3). Performance prediction for the configurated
engine was made by extrapolation of the published data from the 4 cylinder VW
stratified charge engine.
The method adopted for the extrapolation of data from the original VW engine,
was first to determine the gulp, factor and volumetric efficiency. Then the
friction losses (assumed to be equivalent to a standard gasoline engine) were
added to the published bmep in order to obtain the imep. Finally, the ratio of
imep divided by volumetric efficiency was plotted against engine speed.
The proposed bore/stroke ratio of 1.1 is lower than the original VW engine
which has a bore/stroke ratio of 1.24, therefore the proposed engine bmep could
not; be the same as for the original VW engine. In this case Ricardo assumed that
the variation of the ratio imep/volumetric efficiency was the same for both engines
throughout the speed range. The proposed engine imep was then calculated, having
first predicted the volumetric efficiency by the gulp factor procedure. Brake
performance was finally obtained by subtracting the standard gasoline engine
friction losses. In order to arrive at the correct engine capacity and performance,
a step by step procedure had to be adopted, making, as the first step an
approximation of the capacity, then reiterating the calculation until the target
horse-power was achieved.
The estimated performance curve of this engine is shown in Fig. 35. It can be
seen that peak torque Is developed at a high engine speed, however in practice this
is not significant since the torque curve Is virtually flat between 40 rev/s and
67 rev/s.
To control the engine HC and CO emissions, a large oxidising catalyst is
recommended, so that a durability of at least 25,000 miles can be achieved. Low
thermal inertia exhaust manifolds are also recommended, leading to the catalyst
underneath the vehicle floor.
The engine emissions of NO will be within the primary target without EGR.
No special durability problems of NO control are envisaged.
39
-------
Design Notes (Figs. 36. 37. 38)
The choice of a bore/stroke ratio of 1.1 instead of the standard VW bore/stroke
ratio of 1.2^ was made because the smaller bore should give better combustion
(lower emissions) and adequate breathing without increasing engine height sig-
nificantly. Furthermore engine noise will be lower. A C.R. of 8.5:1 was used,
common to VW.
The engine lower end follows conventional gasoline engine practice as does the
cylinder bore spacing at 1.17 x cylinder bore which was controlled by the casting
core thickness of the water jacket between bores.
Cylinder Head and Manifold Arrangement
The inboard inlet manifold and outboard exhaust manifold give cross-flow
porting with a single throttle as for all previous V-8 configurations. To give
satisfactory spark plug and fuel injector accessibility, the pre-chamber had to be
positioned on the outboard side and not Inboard where otherwise it would be
preferred. The ports pre-chamber and pushrods could not all be accommodated on
one side. The fuel lines and spark plug wires are therefore unavoidably long and
also the fuel Injectors determine the engine width, Fig. 38. The exhaust ports
were unswept in order to reduce pre-heat to the fuel Injectors, see Fig. 37.
A four cylinder head stud pattern and conventional rocker gear have been used.
The cylinder head has been designed to employ the minimum number of machining
operations commensurate with the complexity of the VW system.
Combustion System and Breathing Considerations
The combustion system is based on the VW system with a pre-chamber volume of
about 2Q% of the total clearance volume. The throat area was calculated from the
relationship (see Part 2 of Report).
vol. pre-chamber _ (1 - F) = 7 cm
area throat (CR)Y~1
where F =vol. pre-chamber
clearance volume
The transverse plane on the cylInder bore centre runs through the centre of the
pre-chamber and Its throat. Fig. 37 shows the combustion chamber, spark plug and
Injector layout and relative positions which are identical to the VW system. The
pre-chamber Injector and spark plug are arranged in sequence in the flow direction
so that the spark plug receives a pre-prepared mixture.
In order not to overcool the combustion faces of the pre-chamber (critical for
HC emissions), a controlled amount of air cooling by means of fins has been used in
preference to water cooling.
The inlet valve inner seat diameter is 3^.1 mm or 39-6% of the bore. This
gives a mean inlet gas velocity at maximum speed (7^.5 rev/s) of 76 m/s.
Fuel Injector and Control System
A fully mechanical Injection pump supplies the fuelling necessary to both the
pre-chamber and inlet port Injectors. A camshaft operates the injection plungers
-------
and Is gear driven from the camshaft. The Injection pump Is based on the system
by Schafer fitted to the VW pre-chamber engine. It contains 12 cams operating 16
injector plungers and uses components from standard fuel injection equipment. The
pump shown Is basically an In-line pump but with offset injection lines to give
short length. A 90° V12 pump layout for even shorter length was investigated but
could not be Installed because of interference with the front of the inlet
manifolds.
Injectors for the pre-chamber are controlled separately, one per cam (8 cams
In total), whereas those for the Intake port are supplied In pairs from a single
cam (k cams In total).
Pre-chamber Injection quantities are fixed at 2 mm /stroke with an optimum end
of Injection stroke of 70 deg crank angle b.t.d.c. The fuel delivery into the
Intake port Is varied by a spatial cam having a pre-determined contour with the
parameters speed and load. A control box containing the spatial cam is fitted
adjacent to the front four intake port injection lines on the injection pump and the
fuelling delivery Is varied by means of the conventional helix 'cut off/rack
method. The spatial cam is positioned by engine speed and intake manifold
depression.
The nozzle Is a single hole type with an opening pressure of 25 bar, and
injects a spray with about 20° offset. Port injectors have the same opening
pressure and spray a cone envelope of fuel directly onto the back of the inlet
valve. A secondary Injector is included In the intake manifold for cold starts.
Auxiliary Drives (Fig. 36)
Camshaft, fuel injection pump and hydraulic pump are gear driven from the
front of the crankshaft. Twin V-belt drives are used for the alternator and water
pump and a single V-belt for the air-conditioning unit. A conventional skew gear
dr\ve Is used for the oil pump and the distributor is skew gear driven from a
gear on the camshaft nose.
Category k
(2) V-8, Naturally Aspirated - VW Engine - Secondary Emission Target
Engine Specification Identical To Previous VW Engine
Predicted CVS-CH Results
Fuel Economy 15.5 miles/U.S. gallon
Fuel Consumption 15.13 L/100 km
HC ) 2.5/0.28 g/mile
) Baseline/Controlled
CO ) 12.0/1.0 g/mile
NO- Controlled 0.35 g/mlle
X
Estimated Noise 73 dBA
1*1
-------
Predicted Performance, Economy, Emissions and Noise
The performance prediction was identical to that used for the previous VW
engine and the same engine build is proposed. Because this stratified charge
engine Inherently gives low NO emissions, it is unnecessary to penalise the
engine performance by the addition of EGR at the maximum loads of the CVS test.
The EGR is only used at part load conditions. The estimated performance curve is
shown in Fig. 35 as all the performance specifications are Identical to the previous
configuration.
Two oxidising catalysts fitted In series will be necessary to control the HC
and CO emissions and EGR to control the NO emissions. Emission control durability
should be satisfactory for intervals of at least 25,000 miles. The addition of
EGR causes a small penalty in Fuel consumption.
Since VW have not attempted to meet the secondary target with this combustion
system, the proposition that performance will not deteriorate is speculative.
Design Notes
Identical to previous VW V-8 configuration shown In Figs. 36, 37 and 38.
-------
ENGINE CONFIGURATIONS WITHIN CATEGORY 5
The most developed variant of the 3~valve stratified charge engine is the
Honda CVCC. It Is the only system in volume production for automotive applications
and was therefore the obvious choice for the configuration study. One engine build
has been schemed to meet the primary emission target:-
.(1) V-8, 1».28L, CVCC engine
Also, one engine build has been schemed to meet the secondary emission target :-
(2) V-8, 5.58L, CVCC engine
Category 5
(1) V-8, Naturally Aspirated - CVCC Engine - Primary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Compression Ratio
Powe r
BME;P
Max. BMEP
Max. Torque
Torque Back-up
Power/Unit Displacement
Max. Piston Speed
Max. Cylinder Pressure
Con-rod
Distance between centres, L
L .
Ratio of L to crank throw (r), r
Cylinder bore spacing
Package
Engine length 761 mm 29.96 in
height 660 mm 25.99 in
width 6^*2 mm 25.28 in
OQ „_
oo mm
88 mm
1.0
k.28 L
7.9=1
97.5 kW
at 73.5 rev/s
6.25 bar
7-9 bar
at 35 rev/s
268 Nm
26. If*
22.8 kW/L
12.9 m/s
58.6 bar
3.^6 in
3.^6 in
260 in3
130.5 bhp
at kkOQ rev/mi n
90.5 lbf/!n2
115 lbf/ln2
at 2100 rev/min
197 Ibf.ft
0.502 bhp/in3
25^*0 ft/min
850 lbf/in2
11*8.6 mm 5-85 in
3.38
1.22 x cy1inder bore
-------
Pred
Fuel
Fuel
HC
CO
N0x
box volume
weight
Icted CVS-CH Results
Economy
Consumption
Control led
Controlled
Control led
Estimated Noise
Pred
icted Performance, Economy,
0.322 m3 11. 4 ft3
250 kg 550 Ib
16.8 miles/U.S. gallon
13-95 L/100 km
0.2 g/mi le
2.7 g/mi le
1.3 g/mile
73 dBA
Emissions and Noise
The starting point for performance calculation was to calculate the ratio of
Imep to volumetric efficiency for the Honda, 1.5L CVCC engine, and a 5-73L CVCC
engine. Imep was calculated from the published bmep and an estimated fmep was
added. The friction losses of a standard gasoline engine were assumed, with a
small addition (.035 bar) for the extra valve gear.
A proposed V-8 engine of k.26l and bore/stroke ratio of 1 will achieve the
target brake performance. In the calculation, the ratio of imep to volumetric
efficiency Is kept equal to that of the Honda engine at the same piston speeds.
Volumetric efficiency of the proposed engine was predicted by the same method
as for the Honda engine and thus the imep was estimated. Brake performance was
therefore obtained using the same friction losses as above and Fig. 39 shows the
resulting power and torque curves.
A thermal reactor has been fitted in between the engine banks to give a
compact system which Is Ideal for exhaust treatment. The lowest exhaust
emissions from a V-8 3 valve engine have been obtained with this configuration
(see literature survey). Carburettor pre-heating, an inherent requisite of the
CVCC engine, is obtained by arrangement of the carburettor to sit on top of the
thermal reactor, see Fig. k2. No catalyst or EGR will be necessary for the
primary emission target.
Emissions durability of this vehicle should be acceptable for 50,000 miles
although It Is dependent on the physical integrity of the thermal reactor. Since
there is no catalyst, the engine fuel can be either leaded or a leaded gasoline.
Design Notes (Figs. *<0, k\, k2)
A bore/stroke ratio of 1 was chosen for the purpose of obtaining adequate
breathing without compromising engine height. The Honda CVCC engines use bore/
stroke ratio ranging from 0.85 to 1.15. A compression ratio of 7.9:1 is used,
common to the Honda engine.
The engine Installation drawing, Fig. ^0, shows the engine package. Cylinder
centres at 1.22 x cylinder bore were controlled by the cylinder head layout to
accommodate the extra valve and Its rocker gear. An overhead camshaft was also
-------
found to be necessary.
Combustion chamber geometry was based on the Honda conversions of their 1.5L
engine and one American V-8 engine, the Impala.
Cylinder Head Layout
A thermal reactor between the engine banks was chosen as the optimum position
for the V-8 configuration. This determined that the cylinder head porting should
be unl-sided with Inboard inlet and exhaust ports and also that the auxiliary
valve assembly/pre-chamber should be in the remaining space on the outboard side.
A cross drilling Is used to supply the mixture charge to the auxiliary chamber, as
indicated in Fig. *»1 .
An overhead camshaft was found to be the best solution to operate the required
valve gear of the CVCC system. Insufficient space was available for the con-
ventional inboard push rod arrangement due to the space occupied by having inboard
Inlet and exhaust ports. Two outboard camshafts with outboard push rods was one
alternative but the overhead camshaft was chosen for greater cylinder head
simplicity, reduced cylinder head width and with only a marginal sacrifice in
engine height.
The camshaft has three cam lobes per cylinder with rocker followers to each
of the three valves. The rockers operate on the valves via rollers which give low
side thrust, low wear and also lower engine height compared to the standard screw
type adjusters. Tappet clearances are adjusted by means of an eccentric adjustment
on the bearings of the rollers which can be locked in position.
Exhaust port liners have been fitted into the cylinder head for insulation in
the Interests of maintaining high exhaust gas temperatures.
Manifold Layout
The exhaust manifold assembly, designed as a thermal reactor, has a cast iron
outer shell with a stainless steel fabricated Inner construction, as shown in Fig.
42.
There Is a split line (now shown) in the cast iron shell to allow for
installation of the internal components. Exhaust gas from the engine is diverted
into the Inner concentric tube, the gases then flow towards the front of the engine,
out through an open end and finally are channelled to the rear exit through the
circular gap between the inner and outer steel shells.
The volume of the total thermal reactor Is greater than the engine displacement
and this should result In satisfactory exhaust gas residence time for HC and CO
oxidation when combined with the high gas temperatures.
The exhaust gas exit from the rear end of the reactor is angled to direct the
exhaust pipe for its passage between the rear of the left hand bank and the vehicle
bulkhead. Consideration of space and suitable Insulation because of the close
proximity to the bulkhead will have to be made to accommodate this proposed position
of the exhaust pipe to sweep over .the top of the left hand bank rocker cover.
Neither of these exhaust pipe arrangements have been indicated in the Installation
package size.
The carburettor supplies two different mixture charges, one a rich charge to
45
-------
the pre-chamber and the other a weak charge to the cylinder. A hot spot from the
Inner concentric shell of the thermal reactor ensures that both charges are
vaporised before dividing between the runners. Exhaust gas heats the und rside
of the manifold evaporative floor.
Combustion System and Breathing Considerations
The combustion system is based on the Honda CVCC engine. Pre-chamber volume
was arranged to be about 3% of the total clearance volume and the ratio of throat
area divided by pre-chamber volume was 0.1 cm"1. A thimble type of auxiliary chamber
unit is used, the outlet orifice of the thimble being the throat. The spark plug
is In a position to avoid direct fuel or charge Impingement.
Inlet ports are designed for high volumetric efficiency, there being no
necessity for organised swirl. The inlet valve inner seat diameter is 36.1 mm,
about k\% of the bore, which gives a mean inlet gas speed of 76.8 m/s at 73-5 rev/s.
Auxiliary Drives (Fig. 40)
Both overhead camshafts are driven by a single toothed belt, the back of which
Is poly-V form and Is used to drive the water pump. The water pump is mounted on
adjustable feet to the engine and Is used as the tensioner.
A single V-belt drives the air conditioning unit and a twin V-belt drives the
alternator and hydraulic pump. A chain from the crankshaft drives an intermediate
gear from which a skew driven shaft drives both the distributor and oil pump.
The complexity of the front end drive systems on this overhead camshaft engine
is apparent. The proposed arrangement is not definitive since there are several
feasible methods. Toothed belts for the camshafts are, however, considered the best
solution In comparison to chain or gear driven camshafts.
Category 5
(2) V-8, Naturally Aspirated__- CVCC Engine - Secondary Emission Target
Bore
Stroke
Bore/Stroke Ratio
Displacement
Compression Ratio
96 mm
96 mm
1.0
5-56 L
7-9:1
3.78
3.78
3^0 i
in
In
n3
Power
BMEP
Max. BMEP
Max. Torque
Torque Back-up
121 kW 162 bhp
at 66.7 rev/s at 4000 rev/min
6.5 bar 94.5 lbf/ln2
7.9 bar
at 33-5 rev/s
350 Nm
21.5%
115 lbf/ln
at 2000 rev/min
258 Ibf.ft
-------
V
Power/Unit Displacement
Max. Piston Speed
Max. Cylinder Pressure
Con-rod
Distance between centres, L
Ratio of L to crank throw (r), r
Cylinder bore spacing
Package
Engine length
height
width
box volume
weight
Predicted CVS-CH Results
Fuel Economy
Fuel Consumption
HC Controlled
CO Controlled
NO f Control led
Estimated Noise
21.8 kW/L
12.8 m/s
58.6 bar
0.1*76 bhp/ln
2520 ft/min
850 lbf/in2
6.39 in
3
162.2 mm
3.38
1.22 x cylinder bore
795 mm
675 mm
67^ mm
0.362 m3
273 kg 1
31-3 in
26.58 In
26.5 in
12.8 ft3
600 Ib
15 miles/U.S. gallon
15.63 L/100 km
0.37 g/mile
3.0 g/mile
0.37 g/mile
73 dBA
Predicted Performance. Economy. Emissions and Noise
Published data indicate that the amount of EGR necessary to achieve the
secondary NO target will produce an imep loss of about 15%. In order to offset
this torque foss and so maintain the prescribed performance levels, means that the
engine capacity must be Increased from that used for the primary target to 5.56L
(3''-»0 in^), I.e. a capacity increase of about 30%.
Performance predictions were made, assuming the addition of 11% proportional
EGR over the engine spectrum and at maximum load of the CVS-CH test, using the
same method as described for the primary target CVCC engine. The Imep of the Honda
engine was first reduced by 15% in order to obtain the new ratio of imep to
volumetric efficiency with the addition of EGR. The target power output of 96 kW
(128 bhp) was met, with EGR, at 66.7 rev/s.
In practice, EGR will be reduced to zero rate at full throttle and therefore
-------
the true power output will be that calculated without EGR. Performance curves
presented in Fig. ^3. show both conditions. Obviously the vehicle performance will
be more than adequate since the maximum power is 121 kW (162 bhp) at 66.7 rev/s.
Emission control Is achieved with an Inboard thermal reactor as for the
previous CVCC engine. EGR Is recycled Into the inlet system through a single pipe
downstream of the carburettor. The quantity of EGR necessary to achieve 0.;Al g/mlle
of NO is estimated to be 11% over the load range up to and including the maximum
load condition of the CVS-CH test. EGR can be modulated to zero rate for all load
conditions In excess of the latter.
It should be noted that because the HC and CO emissions are only marginally
within the secondary target due to the effects of EGR, it may prove necessary,
dependent on vehicle tests, for an oxidising catalyst to be fitted. However, no
cost allowance has been Included in this study to allow for this.
Emission durability of the HC and CO emissions will be difficult for periods
in excess of 25,000 miles. Again, like the previous engine, the physical integrity
of the thermal reactor Is critical.
Design Notes
The design Is Identical but Increased In size to the CVCC engine schemed to
meet the primary emission target. Only an Installation drawing, Fig. kk, is
therefore presented to allow an assessment.
-------
SUMMARY TABLE
GASOLIHE V8
GASOLINE IL6
PROCO V8
PROCO IL6
PROCO V8
TCCS V8
TCCS IL6
CM ROTAKY
TCCS v8
MA» FH V8
VW ¥8
vw va
cvcc v8
CVCC V8
DIESEL V8
CATEGORY
GASOLINE
GASOLINE
I
I
I
II
II
II
II
III
17
IT
V
V
EMISSION
TARGET
PRIMARY
PR 1 HART
PRIMARY
PHI HART
SECONDARY
PRIMARY
PRIMARY
PR 1 WAT
SECOKOART
PtIMItr
PRIMARY
ECONOARY
RIMRY
ECONOMY
PRINART
ENGINE SPECIFICATION
BORE
97
88
87
96
9*
95
96
101
93
86
86
88
96
88
STROKE
76
82
87
96
9*
95
96
92
93
79
79
88
96
»8
CONFIG-
URATION
NA
va
NA
IL6
NA
V8
HA
IL6
NA
MB
NA
v8
TC
IL6
! BANK
10TARY
TC
V8
NA
V8
NA
V8
NA
V8
NA
va
NA
va
"*
V8
DISPLACE-
MENT L
4.5
2.99
4.15
"..15
5.25
5.4
4.16
5.5
5.87
5.05
3.67
3.67
4.28
5.56
4.78
C.R.
11.0
11.0
11.0
10.0
9.0
8.5
9.0
15.0
8.5
8.5
7.9
7.9
20
PACWSE
LENGTH
HEIGHT
WIDTH
mn
BOX
VOUHC »J
NOT CONFIGURED
NOT CONFIGURED
770
995
800
82]
981
523
845
745
763
• 763
761
795
758
597
638
609
658
610
660
645
643
610
610
660
675
604
600
528
622
622
578
695
630
640
610
610
642
674
692
.275
1.335
.303
.337
.346
.24
.343
.307
.284
i.284
.322
.362
.320
WEIGHT
i-g
245
204
250
263
259
273
260
ISO
286
300
250
250
250
273
JJO
COST
S
595
598
741
664
827
811
827
667
985
756
(EFI 764)
844
(EFI 819)
899
600
670
701
PERFORMANCE
POWER kW
• t rev/ft
96
66.7
96
83.0
96
66.7
96-5
66.7
122
66.7
96
66.7
96
66.7
97
83
135
66.7
96
66.7
96.5
75
96.5
75
97.5
73.5
121
66.7
96
66.7
TORQUE Dm
• t rev/»
285
41.6
232
50
292
38
293
37
365
40
280
29
298
42
214
56
423
41
298
33
228
66
228
66
268
35
350
35.5
286
JJ.4
TORQUE
BACKUP t
25
20
19
26
!3
2)
15.4
17.4
19.0
24.6
9.8
9.8
26.4
21.5
24.0
VEHICLE PERFORMANCE
ECONOMY
n/USgil
16
17.4
18.7
18.4
16.5
17.0
17.0
14.0
14.0
19.0
16.5
15.5
16.8
15.0
11.0
CONSUMPTION
L/100 kin
14.6
13. 5
IZ.5
12.75
14.2
13.8
13.8
16.74
16.74
12.3
14.2
15.13
13.95
1S.6
11.0
HC CONTROL
HC BASE
0.2
1.8
0.2
1.8
0.15
1.0
0.15
1.0
0.25
2.5
0.3
2.5
0.22
2.0
0.3
3.0
0.25
4.5
0.3
0.8
0.23
1.8
0.28
2.5
0.2
0.37
0.46
CO CONTROL
CO BASE
1.0
30.0
1.0
30.0
1.0
8.0
0.8
8.0
0.8
12
1.5
10
1.5
10
0.8
IS
1.0
12.0
0.8
8.0
0.8
8.0
1.0
12.0
2.7
3.0
2.0
NOx
1.3
1.3
1.4
1.3
0.37
0.8
0.8
1.0
0.33
1.0
1.0
0.35
1.3
0.37
1.2
NOISE
USA
71
73
71
75
72.5
70.5
71
71
72.5
72
73
73
n
73
74
EMISSION CONTROL
CATALYST
1 EXH.
AIR IMJ.
1 EXH.
AIR INJ.
1
1
2
2
2
2
2
1
1
3
THERMAL
REACTOR
j
' X
EGR
X
«
X
X
X
X
X
X
X
X
-------
RICARDO CONSULTING ENGINEERS FIG. No. 1
DRG.No. D28875
BARE ENGINE
ENGINI
130-
120-
|
110-
!
!
100-
90.
c-
"80.
i
70-
60-
30 -
ESTIMATED PERFORMANCE CURVE FOR
0 97 x 76 mm V8 GASOLINE ENGINE
FOR PRIMARY EMISSION TARGET
A.I.T. 20°C
DATE- 11.9.75
J
s
BARO 760 mm Hg
• BUILD: CLOSE TOLERANCE SOPHISTICATED CARBURETTOR, MODULATED EGR,
AIR INJECTION OXIDATION CATALYST
inn ln
J \J\J
"80
- /
-70 f
-X
^f f\ 1
"60 •
CC.
§
Q.
-50
HO
• ?n *
• JU /
.?0
' BHEP
i
/
/
( POWER
<
^"
/
/
/
/
/
1
>
/
~r
NGINE SPE
/^
/
\
:D
> *"
\
\
10 20 30 40 rev/s 50 60 7
i 1 1 i i i
i_
(D
-O
- , -8-
Q.
0)
J3
^
*
i 8
I
1000 2000 3000 4000
• 140
•130
.120^
•^
-O
•110
•100
-90
D
|
rev/min
i
-------
RICARDO CONSULTING ENGINEERS '
ESTIMATED PERFORMANCE CURVE FOR
FIG. No. 2
DRG.No. D28876
DATE:- 1l-9-75
0 88 x 82 .mm 6 CYLINDER "EUROPEAN TYPE"
GASOLINE ENGINE FOR PRIMARY EMISSION TARGET '
,
BARE ENGINE ' A.I.T. 20°C BARO 7&0 mm Hg
BUILD: PETROL INJECTION, MODULATED EGR, AIR INJECTION, 'OXIDATION CATALYST
I
_ .1 r»« ' *n_
130-
120-
110-
100-
90-
80-
Q.
XI
70.
60.
50-
^o-
30-
1
^m
•go
_ftn /
/
m,~tr\
-/U
J^
/• -
3 i
3 POWER - C
jv
nltO
_-jn
•5V
•A
0 2(
1
_>
/
/
L
r
> . 3
I
\
BMEP
•
/
/
POWER
0 *»C
1
^^
•
/
/
•
'
•>s
/
/
ENGINE SP
50 rev/s I
1 •
\ .
/*.
.»
ED
07
1
^^
X:
"^
• •
)
) 5
i
r— —
9"
• 8-
•. ra°
\ t
o.
. 0)
•Q7.
7
6
0 .. 9
»
1000 2000 • 3000 *»000 5000
rev/ml n
- mo
• 130
• 120
-------
RICAROO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
0 87 x 87 mm V8 CONFIGURATION - CATEGORY 1
BARE ENGINE
A.I.T. 20C
FIG. No. 3
DRG.No. D28877
DATE:- 11.9.75
BARO 760 mm Hg
PRIMARY EMISSION TARGET PROCO COMBUSTION SYSTEM
MOO-
10-
1*0
30
2000
3000
14000
UO
rev/mln
-------
tfTORMJUC PUHP
NrfKTERPUMP
TASK I CONflGORATIOM S1UPY
V* PORD^PRQCQ'
LyrxKra* ncmy>
XHR CONDfTlONING UNIT
BOPt en «i.*i
STROKE B7«vm
BMP ^tf H\^
BMtP tMbor £ «-7 rtv/»
6 9 bar m 3Af«v/«
P M*X tb S toor
CM*CITY 4is
BOX VOL -275 »O
tST N^IGKT (SO Kg
BORE 34S CM>,
STOOKt 3*5T UNITS
BMP |28 »•*«•• rpm.
-------
VIEW ON CYLINDER SECTION A A
HEAD FACE
PLAN VEW
E.PA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASK n CONFIGURATION STUDY CATEgORY It
V6 FORD 'PROCQ' SYSTEM
CYLINDER HEAD LAYOUT
PRIMARY EMISSION "TXRC3ET
T)
3111/2
-------
FIG.
E.PA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASK: n CONFIGURATION STUDY CATEGORY I
va FOBD ' PROCO' S/STEM
CROSS SECTION ARRANGEMENT
PRIMARY EMISSION TARGET.
-------
RICARDO CONSULTING ENGINEERS
FIG. No. 7
DRG.No. D28878
DATE:- 11.9.75
ESTIMATED PERFORMANCE CURVE FOR
g 96 x 96 mm IN-LINE 6 CONFIGURATION - CATE.GORY 1
HARE ENGINE A.I.T. 20°C BARO 760 mm Hg
PRIMARY EMISSION TARGET PROCO COMBUSTION SYSTEM
r100
130-
120 .-
30-
1000
2000
3000
4000
10-i
cs
rev/min
-------
HYDRAULIC
PUMP
BORt <* o v- S.I.UN\TS
STROKt .
BHP KtV.V ««7r«v/«
BHtP fcttbar «(f/rtv/*
ta»r • 57 rav/t
P
CAf*CJT> 415
BOX VOL »\im»
EST 'WEK5HT 9b» Hf
IM IW«* • MM r«n
BMVOL
or WEMMT
STTVW1ED OVsRSL PHOB1CT
g OBMBGURKnON SlUOy CKHOOPCf I
IN-UHLt.
P
CD
3111/7
-------
FIG. S.
EPA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASkl n CONFIGURATION STUDY CATEGORY 1
IN-LINE
FORD'PROCO' SYSTEM
CBOSS- SECTIONAL ^ARRANGEMENT
PRIMACY EMISSION TABGET
3111/5
-------
RICARDO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
FIG. No. 10
DRG.No. D288?9
•DATE- l1-9-75
g 91* x 9*> mm V8 CONFIGURATION - CATEGORY 1
BARE ENGINEA.I.T. 20°CBARO 760 mm Hg
SECONDARY EMISSION TARGET PROCQ
170-
: PERFORMANCE WITH 15% EGR
1000
2060
rev/mi n
-------
HYDRAULIC PUMP
ALTERNATOR -
EPA. LJCMT Dinv SnWIFIED CH*O(f. HRQOECT
TA>3K g CPNFIOJBATIOM «UDv QMTQOHY 1
ve
c
S////3
-------
RICARDO CONSULTING ENGINEERS
MAXIMUM POWER OPERATING CONDITIONS FOR
LU1 TCCS ENGINES AT TWO SMOKE LEVELS
NATURALLY ASPIRATED
$ TOYOTA DATA ON LH»1 BOSCH SMOKE NO. k
$ TEXACO " ........ NO. 1»
M it N0. 2i-2
FIG. NO. 12
DRG. No. P28880
DATE:- 12.9.75
0
it n ii
60
10
ENGINE SPEED rev/s
-------
RICARDC
10 -|
9 -
8 -
7-
6-
i_
JC.
•
Q.
± 5-
J3
k~
3"
2-
ID
) CONSULTING ENGINEERS
INDICATED SPECIFIC AIR CONSUMPTION FOR
L141 TCCS ENGINES AT TWO SMOKE LEVELS
NATURALLY ASPIRATED
© TOYOTA DATA ON Ll4l BOSCH SMOKE NO. 4
® TEXACO " " NO. 4
Q ". " . " " ll " NO. 2i-2
1 ND 1 CATED
SPECIFIC AIR
CONSUMPTION
•5500 I
• 5000
•i»500
-4000
i_
j:
•
^ _
•3000 .-^f
^v
O)
-2000
- 1 000
®v
"N
-
100
•
X
fi
0
i
>3»
^^— (
rev/mln
2000
l
FIG. No. 13
DRG No. D28881
DATE:- 12.9.75
V.
— -A
^
•
30
Q)
00 ,
•
---•
.40
1 1 i i ' i
0 JO 20 30 40 50 60
ENGINE SPEED rev/s
DO
1
-------
RICARDO CONSULTING ENGINEERS FIG. No. 14
MOTORING FRICTION OF L141 TCCS ENGINES DRG . No. D28882
DATE:- 15.9.75
O ENGINE NO. 1
(£ ENGINE NO. 2
® ENGINE NO. 3
50-
4o-
30-
c
4-
_Q
1
Q.
UJ
U.
20 -
\
10-
0
[-3.5
•3.0
•2.5
•2.0
(0
-Q
•1.5
*
-1.0
•0.5
10
/
/
<
^^"c
•»
(
00 15
1
/
/
Q
5 ^
)
)
00 20(
L
/
X
..
x x c
) (
7 V
rev/mtn
)0 25
1
.
/
4
^A
s \
$
\
)
oo 30
/
4
s
s
)
\
00 35(
i
/
/
s
)0 40
1
III III
10 20 30 40 50 60
DO
ENGINE SPEED - rev/s
-------
RICARDO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
FIG. No. 15
DRG.No.
DATE;- 1l-9.75
0 95 x 95 mm NATURALLY ASPIRATED V8 CONFIGURATION - CATEGORY 2
BARE ENGINE
A.I.T. 20°C
BARO 760 mm Hg
PRIMARY EMISSION TARGET TCCS COMBUSTION SYSTEM
rioo
10-1
130-
120-
30-
• 130
120
-110 ^
100
90
'80
2000
rev/min
3000
4000
-------
823
KXPRAULIC PUMP-
ALTERNA.TOR
S/////2
W - - &I.UNHS
arena » »-.
•HP HfcHV ««*>W»
•HEP 3 » hw *«»»f»y/»
»*
BOK VOL 337 „»
ESTVCWMT
-------
SECTION B-B
SECTION AA
VIEW ON CYUNDER
HEAD FACE
E.PA. LIGHT OUT> STRATIFIED CMAROf PROJECT
T/VbK H CONFIGURATION STUDY
V8 IMAOVJRAa.V
CYLINDER HEAP "DRG-.
-------
FIG. 18
E.PA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASK H CONFIGUgATION STUDY CATEGORY H
NATURALLY ASPIRATED TEXACO TCCS SYSTEM
PRIMARY EMISSION TARGET
CROSS SECTIONAL ARRANGEMENT
3111/1O
-------
RICARDO CONSULTING ENGINEERS
FIG No 19
DRG.No. D2888A
DATE- 15.9.75
CALCULATED VARIATION IN BOOST DENSITY RATIO AND
AIR FUEL RATIO FOR THE CONFIGURATED TURBOCHARGED TCCS ENGINE
PRIMARY EMISSION TARGET
30 -
25
20
15
10
20
t
1000
ENGINE SPEED - rev/s
30 4p 50
i
1
60
70
2000
3000
1»000
rev/min
1.6
1.2 H
LU
O
1.0
-------
RICARDO CONSULTING ENGINEERS
FIG. No. 20
DRG.No. D28885
DATE:- 15-3-75
RELATIONSHIP BETWEEN INDICATED FUEL CONSUMPTION
AND AIR FUEL RATIO FOR A TCCS ENGINE
ZSO-T0-'*6-
270-
260.
250-
.c
13
^ 230H
en
220'
210-
200-
190-
-C
•
Q.
-0.38-
0.36-
-0.32-
UQ.30—
10 15 20
25 30
A/F RATIO
35
-------
RICARIDO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
0 96 x 96 mm TURBOCHARGED IN-LINE 6 CONFIGURATION - CATEGORY 2
FIG. No. 21
DRG.No. D28886
DATE:- 15.9.75
BARE ENGINE
A.I.T. 20 C
PRIMARY EMISSION TARGET
BARO 760 mm Hg
TCCS COMBUSTION SYSTEM
100
130 ?!
120 -
110
100 -
90 '
80 -'
CL
_c:
.c
70 -
60 -
50 -
30
ENGINE SPEED - rev/s
kO 50
1000
3000
rev/mi n
4000
140
.130
120
110
100
•90
-------
HTWOJLIC
PUMP
FUEL IMTECnON PUHP
3*£ -4 Bta HOU5INC
71 0 bar
CAFWCJTV 4 It lits.t
BOX VDL
EST. WEIGHT HOfc*
EPrX LIGHT DUTY 9fTTWTinED CHKROe PROJECT
•WOK D CONnCURATION S1\KH CATEGORY I
-------
SECTION 3-B
DLAN VIEW
SECTION A-A
VIEW ON CYLINDER
HEAD FACE
ZIII/14
E.PA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TKSK n CONFIGURATION STUP/ cxitcow/ c
IN-LIML fa. TURBOCK^RGCD TCCS
CYLINDER HEMS DftS
E.MISS1QNI "ffsRCLT
TN>
-------
FIQ.Z4.
£PA LIGHT DUTY STRATIFIED CHARGE PROJECT.
TASK \i CONFIGURATION STUDY CATEGORY 77.
IN-UNE e TUR&OCHA.RGED TCCS
CROSS- SECT/OMAL ARRAN6EMFNT.
PRlMARY EMISSION TARGZT.
311 I
-------
RICAROO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
2 BANK ROTARY ENGINE - CATEGORY 2
FIG. No. 25
DRG. No. D28887
DATE:- 15.9.75
BARE ENGINE
A.I.T. 20C
BARO 760 mm Hg
PRIMARY EMISSION TARGET CURTISS WRIGHT COMBUSTION SYSTEM
. 100
10-
130-
120-
110-
100-
30
1000
2000
3000
rev/min
.140
5000
-------
3U//20
EPA LIGHT DUTY STRATJFtZD CHARGE PROJECT.
TASK H CONFIGURATION STUDY CATEGORYJ/.
ROTARY.
DRG.
PRIMARY
IVJ
-------
EPA LIGHT DUTY STffAT/S/fD CHARGE
TASK I/ CONF/6URATION STU&Y CATEGORY Jj.
2 BANK ROTARY.
C/^O^S <* LOH&tfcfDlNAL 3GCT/OMAL A RRANff£MSA/7
PRIMARY £Mt-S-**CN TA
-------
RICARDO CONSULTING ENGINEERS
FIG. No. 28
DRG.No. D28888
DATE;- 15,9.75
CALCULATED VARIATION OF BOOST DENSITY RATIO FOR
CONFIGURATED TURBOCHARGED TCCS ENGINE
SECONDARY EMISSION TARGET
1.6
1.4
o
Q.
<
>-
I-
l/>
1.2
1.0
ENGINE SPEED - reWs
20 30 40 50
-I 1—
1000
2000 3000
rev/min
60
70
4000
-------
RICARDO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
9 101 x 9Z nwn V8 TURBOCHARGED CONFIGURATION - CATEGORY 2
BARE ENGINE A.I.T. 20°C BARO 760 mm Hg
SECONDARY EMISSION TARGET TCCS COMBUSTION SYSTEM
180.
FIG. No 29
DRG.No.D28889
DATE:- '5.9.75
PERFORMANCE WITH 1U EGR
AND COMBUSTION RETARD
1000
-------
HCRAUUC PUMP-
AUCTNATOR
BOX HOUSING
E.PA. LIGHT DUTY STRATIFIED CHAB<3E PROJECT
TASK H CONFIGURATION STUDY CATEGORY II
Vg> TURBO CHARGED TCCS SYSTEM
INSTA LL ATION DR.G.
SECONDARY EMISSION
BORE ICX-- S.LUNITS
STROKE: 92 m«>
BMP IS5 KW atHim/*
BMET> *4 bar <>>«-Tr«v/«
9O Wr o> 41 rtvH
7IOb«r
5Q7 Litres
BOK VOL -»*3m»
EST WCICHT 2*6 A,
•HP
•TCP
P H*X
I2-I cuft
63O •>
O
-------
RICAROO CONSULTING ENGINEERS
FIG. No. 31
DRG.No.
DATE;- 15-9-75
ESTIMATED PERFORMANCE CURVE FOR
0 93 x 93 mm V8 CONFIGURATION - CATEGORY 3
BARE ENGINE A.I.T. 20°C BARO 760 mm Hg
PRIMARY EMISSION TARGET MAN-FM COMBUSTION SYSTEM
130-
120-
110-
100 -
90-
80 -
CL
ii 70
60 •
50
30
"100
90
80
70
60
_*
50 '
O
Q.
1000
POWER
ENGINE SPEED - rev/S
30 liO 50
BMEP
/
\
10.
60
I
2000
3000
4000
u
TO
J3
8.
o.
UJ
7-
.130
- 1 20
110
- 100
P90
80
I
rev/mi n
-------
147-3
49O
ALTERNATOR &A.E "4
BELL HOUSING
712-9 .
28-O4"
FUEL INJECTION
PUMP
29 34"
3111/22
32O
320
WATER PUMP
HYDRAULIC PUMP
STARTEB
MOTOR
V6 N/A -MAN. FM SYSTEM
INSTALLATION 0»tt.
PRIMARY B*tt»OM T>M%aiT
UWT
5.1. UNIT*
•OAt 9B««.
STHOKI 95 •.
RMAX.
CAmOTY 3-Ot
•OK VOL. O3O7
»•*•«.
07
ao* OA
•OK VOL. » 6 eu.fi.
-------
PLAN VIEW
SECTION A-A
VIEW ON CYLINDER
HEAD GAS FACE
3111/3O
E.PA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASK n CONFIGURATION STUDY CATEGORY IE
V8 NATURALLY ASPIRATED M.A.N. FM SYSTEM
PRIMARY EMISSION TARGET
CYLINDER HEAD DRG.
IV
01
-------
FIG. 34
E.RA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASK H CONFIGURATION STUDY CATEGORY nt
VQ NATURALLY ASPIRATED M.A.N. FM SYSTEM
PRIMARY EMISSION TARGET
CROSS SECTIONAL ARRANGEMENT
3111/71A
-------
RICARDO CONSULTING ENGINEERS
FIG. No. 35
DRG.No. D28891
DATE:- 15.9.75
ESTIMATED PERFORMANCE CURVE FOR
0 86 x 79 mm NATURALLY ASPIRATED V8 CONFIGURATION - CATEGORY 4
BARE ENGINE A.I.T. 20°C BARO 760 mm Hg
PRIMARY AND SECONDARY EMISSION TARGET VW COMBUSTION SYSTEM
100 . . , , , 1 10 «,
Q.
JC
-Q
130
120
110 -
100
90
80
70
60
50
30
• 90
- 80
- 70
-^
I
o
Q.
50
- 30
20
1.0
JOOO
BMEP
POWER
rev/s
5P
60
-140
120
tvl
110 .E
100
•90
80
I
2000 3000
ENGINE SPEED - rev/min
4000
4500
-------
HVDRAUJC PUMP
O.LTEHNA3PR
STARTER MOTOR
L AIR CONDITIONING
UNIT
FUEL INJECTION
PUMP
vDIA.
SI. IMT5
BORE
STROKE
BHP 9i-S KW c 75 W»
BME.P 7-1 bur rtv/»
P HAX 56-«. bar
CAPACITY 3-UT ULrc*
BOX VOL. -aa^-m*
EST. WEIGHT
BORE 3-39" OlA,
STROKE 3H" UNITS
BHP 121 d> 450O rp.m.
BMEP 103 Ib/in*
-------
PLAN VEW
SECTION A A
VIEW ON CYLINDER
HEAD F»CE
E.RA. LIGHT DUTY STRATIFIED CHARGE PROJECT
TASK n CONFIGURATION STUDY CATEGORY IT
V8 VW SYSTEM
CYLINDER HEAD DRG.
PRIMACY AND SECONDARY EMISSION TARGET
T
3111/24
-------
EPA LIGHT DUTY 57RATIFIED CHARGE PROJECT.
T4SH U CONFI6URAT10N STUDY CATEGORY]$.
V8. V.W. SYSTEM.
C ROSS - 3£C T/ONAL ARRAN6EMENT.
PRIMARY A/VD SECONDARY EMISSION
S////23
-------
RICARDO CONSULTING ENGINEERS
FIG. No. 39
DRG.No. D28892
DATE;- 15-9-75
ESTIMATED PERFORMANCE CURVE FOR
0 88 x 88 mm V8 CONFIGURATION - CATEGORY 5
BARE ENGINE
A.I.T. 20C
BARO 760 mm Hg
PRIMARY EMISSION TARGET HONDA CVCC COMBUSTION SYSTEM
130
120 -
110 -
100
90-
80
70
60-
50-
30
100
•80
'70
o
Q-
•50
rkQ
^
20
<
10*00
BMEP
POWER
30
_*
rev/s
kO 50
60
_J_
2000 3000
ENGINE SPEED - rev/min
70
i
9-1
8.
7H
6.
130
CV)
• 1 20 .5
. 110
100
.90
80
i
-------
S»iTER PUMP
ALTERNATOR
L
STARTER MOTOR
PUMP
BORE
STROKE
&H.P
•» 7Mrcv/»
79 b.r
P MAX. SO C Ur
CAp»crry 4-ae
•OX VOL. 322-,'
IMS
lAL
ItO 5 •> 4400 r.pm
•.HEP 1Mlb/M> «4400r.(k«.
115 lb/.n> o>2lOOr.(i«.
»WkX. 65O Ib/M*
OMXTTV 24000
•WXOL u4 «.jt
EST VtXXT 3OO Ib
E.RA. LIGHT DUTY STRATIFIED CHARGE. PROJECT
TASK a CONFIGURATION STUDY CATEGOeY V
V6 CVCC SYSTEM
3f11/2&
INSTALLATION PRO.
PRIMARY EMISSION TARGET.
71
O
-------
VIEW ON CYLINDER SECTION A A
HEAD FACE
PLAN VIEW
EPA LIGHT DUTY" STRATIFIED CHARGE PROJECT.
TASK II CONFIGURATION STUDY CATEGORY V
V8. c.v.c.c. SYSTEM.
CYL/MDER HEAD LAYOU7.
PRIMARY £M 1331 ON TARGET.
-------
FIG. 42.
EPA LIGHT DUTV STffATlFllD CHARffC PROJJKT.
TASK H COH FIGURATION STUDY CATEGORY V^.
VQ. c. v.cc.
CROSS-
PRlMAKY £M/SSfON
3111/26
-------
RICARDO CONSULTING ENGINEERS
ESTIMATED PERFORMANCE CURVE FOR
0 96 x 96 mm V8 CONFIGURATION - CATEGORY 5
BARE ENGINE A.I.T. 20°C BARO 760 mm Hg
SECONDARY EMISSION TARGET HONDA CVCC COMBUSTION SYSTEM
1-130-
FIG No A3
URG No D28893
DATE - 11.9.75
170-
40
rev/mi n
3000
AOOO
-------
_795
MR CONDITIONING UNIT
EPA U&HT PUTT STRATIFIED CHARGE PROJECT
TASK II CONFIGURATION STUP? CATEGQRy V
V8 C.VC.C. SV5TE.M
INSTAUATION PRG
SEOJNOARY E.HI95ION TAPfcLT
L HYDRAUUC POMP
SrJ —ALTERNATOR
BORE 9tm,
STROKE 9fcmm
B. H. P 121 KW ao «.(. 7 r«v/»
B.M.E.P fSb.
7 9 bar oJ 33 5 rev,
P MAX. 58-6. b.c
CAROCITV 556 litre*
BOK %0- 3M ^'
ESTWEIGMT 27S Kg
BORE
STROKE
B.HP
&ME.P
78 " UNJiTS
.2 as 4OOOrp«i.
co 4000 rp..
115 lb/'«J a) r*
PMAX. 83O Ib/.r,'
CAPACITY 34O c i.o
BOX VOL 128 ^.{t
ESr WD&HT oOO Ib
S111/29
-------
A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
SECTION H
COST STUDY
-------
COST ANALYSIS
Since the literature survey contained little information on production costs
for the various stratified charge engine, an in-house cost estimate was made for
each of the engines designed in the configuration study. The input information
for the analysis was obtained from two principle sources.
1. Information supplied to Ricardo on a confidential basis by a number of
European manufacturers of automotive vehicles and associated components
including fuel Injection equipment, carburettors etc. This information was
broken down Into costs of major engine mechanical components such as block
pistons, crankshaft, flywheels, cylinder heads etc.
2. Information contained In two surveys by NAS in May, 1973 and September, 197**
(Ref. 6.32) covering the cost of emission control components. In some cases,
the figures from these two references were adjusted to take account of
Inflation.
In deriving the engine costs, no attempt was made to adjust the figures from
projected sales. It was simply assumed that equal numbers of the alternative
engines were being produced, and that the rate of production was of the order of
50,000 units/year.
The reasons behind the choice of the individual figures are given below.
1. I tern 1 - ^4. The cost of the engine assembly was basically determined by the
engine size, although add!tions were added to the CVCC engine to account for
the extra valve gear and camshafts.
2. Item 1 *» and 5- For many of the engines, the fuelling equipment is a major
item. The injection pump for each of the engines was considered to have
equal production costs, with a small reduction for 6 cylinder engines, and an
increase for boost control on the turbocharged engines. The injection equip-
ment cost of the VW engine was particularly high due to the 12 plunger layout
and 16 injectors. Some allowance was made for an alternative arrangement
using a completely electronic system. The carburettors of the CVCC engine
were considered to be 30% more .expensive than those of the gasoline engine,
and the IL-6 gasoline engine was fitted with electronic fuel injection.
3. An allowance was also made for control equipment on the throttled fuel
Injected engines, since the throttle must be linked with the fuel injection
pump, as well as a signal for engine speed, from the distributor. In many
cases, these I terns must also be linked to the EGR valve.
4. I tern 8. Since direct injection stratified charge engines appear to function
better with long duration, or multi-strike sparks, an allowance was included
for transistorised Ignition on these engines.
5. I tern 6. The cost of exhaust catalysts was determined by the .amount of control
required e.g. the cost of catalysts for the secondary target TCCS engine was
twice as high as that for the primary target MAN-FM, reflecting the large
difference In baseline HC emissions. Surprisingly, the cost of the thermal
reactor for the CVCC engines emerged as more expensive than a catalyst.
6. I tern 9- At the secondary emission target the exhaust gas recirculated to the
Inlet of the engines, must be modulated according to the engine air flow, and
often it must also be cooled, to reduce the air displacement and heating
effects in the engine.
-------
7. I tern 10. Other emission control items such as evaporative controls, PCV
valves, Intake heaters, dleseling solenoids etc., were costed separately and
added together. The fuel Injected engines had considerable advantages In this
area.
8. I tern II. An air pump was Included on the gasoline engine.
9. Item 13. A turbocharger was Included on two TCCS engines.
Four of the engines considered were similar to those costed by NAS in their
January, 1973 report. The comparison of results is:-
Ricardo NAS
Estimate Estimate Ratio
1975 % 1972 %
Gasoline V-8 595 320 1.86
Primary CVCC 600 300 2.0
IDI Diesel 701 3^3 2.0A
Rotary 667 (with carburettor 2Jk 2.^2 (2.0k)
560)
The rotary engine estimates were not directly comparable, as the Ricardo con-
figuration had fuel Injection. The figure in brackets Is an alteration to include
a carburettor rather than fuel Injection for comparison purposes.
The ratio of estimates Is consistent among the different engines, but the
ratio of 2 between the two estimates is rather high. Some of the difference can
be accounted to Inflation, and the remainder is due to the higher Ricardo estimate
for the basic engine assembly.
50
-------
STRATIFIED CHARG6 ENGINE . FEASIBILITY STUDY
BAR CHART SHOWING ESTIMATED MANUFACTURING COST BREAKDOWN POD THE VARIOUS POWER PLANTS - U.S. DOLLARS
POWER PLANT-
V-8 GASOLINE
IL6 GASOLINE
PROCO V-8
PBOCO IL-4
P«OCO V-B
TCCS V-»
TCCS IL-6 T/C
CURTIS WRIGHT ROTARY
TCCS V-« T/C
M.A.N. P.M. V-a
V.W. V-«
V.W. V-a
CVCC V-a
cvcc v-«
DIESCLV-a
1. CYLINDER BLOCK
2. CON-RODS, CRANKSHAFT, VALVI
GEAR, FLYW HEEL, ETC.
3. PISTONS
4. CYLINDER HEAD(S)
5. CONTROL GEAR BETWEEN EGS,
THROTTLE, DISTRIBUTOR AND
INJECTION PUMP
6. MANIFOLDS & HEATING PIPEWORK EFE.
7. EXHAUST REACTOR AND/OR CATALYST
a. IGNITION DISTRIBUTOR, COIL, PLUGS
9. EGI VALVE AND PIPEWORK
10. OTHER EMISSION CONTROL GEAR: EVAP
CONTROL, P.C.V. INTAKE HEATER,
TRANSMISSION CONTROLLED SPARK,
SPARK ADVANCE CONTROL, ANTI
DIESEUNG SOLENOID, ETC. ETC.
11. AIR PUMP
U. STARTER MOTOR, ALTERNATOR
VACUUM PUMP, HYDRAULIC PUMP
13. TURBOCHARGER
14. CARBURETTOR AND/OR INJECTION
PUMP, PRIMARY INJECTORS,
SECONDARY INJECTORS
1 1 2 I 3 I t I 8 1 7 I a I 9 1 10 1 11 1 12 1 U 1
1 1
1 1 2 I 3 I 4 161 7 1 8 1 9
1 1
> 1
1
1
1
10 1 11 1 12 1 U
1
Z 1 3 1 4 I 5 161 7 1 8 191 10 1 12 1
1
1 1
14 1
Z 1 3 I 4 | 5 161 7 | » I9IUI 1Z 1 14 1
Z 111*15
2 1 1 I 4 1 S
61 1 1 8 1 9 1101 « 1
14 1
61 7 II 1 9H01 II 1 14 I
I 1 2 1 1 I * 1 S |6| 7 1 8 191 10
1
1 . 2 • 3 • *
1 1
1
61 7 1 a 1 10 I
IZ I 11 I 14
1
Z 1 14 1
1 I Z 1 3 1 t 1 5 1 6 1 7 1 » 1 ' 1 10 1 12 1
1
i
[
I
11 1 14
1 1 Z 1 3 1 4 161 7 1 « 1 12 1 U 1
1 1
1 1 . Z III*
1
1
S 161 7 1 • 1101 12 1 14 1
1
1 I .2 1 J 1 4 1 » 161 7 1 91 9 1101 12 I 14
1 1
1 ' 1
1 1 Z 1 J 1 4 161 7 1 B I 10 1 IZ 1 U
1
11 2 1
|
1 1 2
|
1 4 Itl 7 I 8 I 9 [ 10 I 12 1 U 1
I 1
1 I 4 Id U 1 U
1
,
L-3 -
f ^ U _ ,
//
REDUCED
ELECTRO!
COST FOR
•IIC F.I.E.
1
j 100 200 300 400 500 600 TOO 800 900 tOC
-------
A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
SECTION I
POWER PLANT RATING
-------
POWER PLANT RATING
SUMMARY
The quantitative comparison of different power plants was one of the major aims
of the study. This section describes the rating methodology Which was developed,
how it was applied to the potentially viable power plants and the results of that
application.
The rating methodology involves the identification of performance aspects or
requirements for a power plant. Each aspect Is given a weighting indicating Its
relative importance. Each power plant is then given a 'rating' indicating how
well it met the requirements of each performance aspect. Multiplication of each
'rating' by the appropriate 'weighting' and summation of the products then gives a
numerical 'overall rating1. Comparison of the 'overall ratings' allows the power
plants to be compared on a numerical basis.
The individual ratings for each performance aspect for each power plant are
listed and the reasons for these ratings are discussed.
The 'overall ratings' indicate that the rating achieved by the conventional
gasoline engines at primary emission levels can be closely approached by two
stratified charge systems (PROCO and CVCC). The remaining contenders can be con-
sidered contenders all achieving varying degrees of viability.
Of the engines configured for the secondary emissions targets, the Honda
CVCC combustion system emerged as the best, closely followed by Ford PROCO and
VW..
51
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POWER PLANT RATING
INTRODUCTION
In order to provide a quantitative assessment of the relative merits of the
various power plants selected, the major aim of the study was to rate the per-
formance aspects of each power plant. The methodology already developed for the
light duty diesel engine study was considered suitable for this application. By
the use of the existing methodology a direct comparison between the assessment
of the existing power plants and those rated in the earlier survey was possible.
Those aspects which render a particular power plant viable or not for a light duty
application were also identified and quantified. Furthermore the methodology
allows an assessment of changes in a particular area as well as highlighting areas
worthy of effort to make a particular configuration more suitable for use in a
given environment.
Approach of Rating System
The fitness of any power plant for a given duty is a combination of the
excellence with which it meets various performance aspects or requirements and the
relative importance of those individual aspects. The application of any rating
system must thus involve five stages:-
(1) Identification of performance aspects.
(2) Estimation of relative importance of those aspects.
(3) Estimation of how well a particular power plant meets a performance aspect.
CO Assessment of overall merit of that power plant.
(5) Comparison with overall merit of other power plants.
Performance Aspects
The methodology employed in the light duty diesel engine study established
twenty-six performance aspects by which each power plant was rated. Each of these
performance aspects was Individually weighted as a measure of Its relative
importance; the final score being the product of the rating and the weighting. For
the current study the same performance aspects and weightings were employed
The performance aspects are listed in the following table together with the
weighting factors.
Aspect Weighting
1 Smoke k.kQ
2 Particulates 2.U
3 Odour /I./48
*» N0-x 3.92
5 HC 3.99
6 CO 3.61
52
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Aspect Weighting
7 S02 3.*»8
8 HC reactivity 1.83
9 Evaporative Emissions 1.60
10 Miscellaneous Emissions 0.98
11 Noise (Drive-by) 6.32
12 Package volume 2.61
13 Package weight 2.59
1 b Fuel economy 12.20
15 Fuel cost 5-^0
16 Vehicle first cost *4.65
17 Maintenance cost ^.35
18 Startability ^.85
19 Hot drlveabi 1 i ty 4.1»8
20 Cold driveability 3-52
21 Torque rise 1.98
22 Durability *4.80
23 Heat loss 2.18
2*» Fire risk 3-55
25 Idling noise 3.83
26 Vibration and torque recoil 2.18
In some of these areas, estimates on the performance of the various engines
had been made in the configuration study, and the results are summarised in the
summary table of that section.
How Well a Performance Aspect or Requirement is Met
It is necessary that a rating scale be devised so that a quantitative assess-
ment of how well a particular power plant meets a given performance aspect can be
made. The above list of performance aspects shows that although some aspects could
be quickly assessed In a numerical fashion, many others are essentially qualitative
and any rating scale should be able to cover all aspects.
As expected, some difficulty was experienced in relating a purely subjective
Impression to a 1Inear quant!tatlve scale, but after some consideration the
53
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following system was adopted as giving the numerical scale easily relatable
subjective key points. The numbers without definition are an interpolation of the
surrounding merit definitions.
Merit Rating Scale
0 Totally unacceptable
2
3
i*
5
6
7
8
9
10
Assessment of Overall Merit
Bad
Poor
Acceptabl e
Good
Best practi
Perfect
of the Power
cal
Plant
The rating system evolved allows an immediate quantitative assessment of the
overall merit of the power plant and this is accomplished by multiplying each
aspect 'rating1 by its appropriate 'weighting' and summing all the products.
With a total weighting of 100 and a merit scale of 0-10 as above the maximum
possible Is 1000.
The relative merit of various power plants can be assessed immediately by
comparing their total scores, the power plant with the highest score being the
best. An idea of the absolute merit of the power plants can also be obtained If
the score Is divided by 100 and the quotient related to the above rating scale,
e.g. a score of 1000/100 = 10 Is a 'perfect' power plant. A score of 500/100 = 5
is an 'acceptable' power plant.
Use of the Rating System In the Study
In order to apply the rating system to the power plants considered in this
study a committee was used to assess the various ratings. The committee consisted
of four experienced members of Rlcardo staff and great care was taken to ensure
that the committee had no bias to either diesel, gasoline or any of the stratified
charge configurations considered In this study. The power plants considered were
those described in the 'engine configuration' section of the report with the
addition of the two gasoline engines and the IDI diesel engine described briefly
In that section. The engines considered are listed below, together with the
categories In which they are divided and their respective emission targetst-
Englne Category Emission Target
1 V-8 'American' Gasoline - primary
2 IL-6 'European' Gasoline - primary
3 PROCO V-8 I primary
b PROCO IL-6 I primary
5 PROCO V-8 I secondary
-------
Engine Category Emission Target
6 TCCS V-8 I I primary
7 TCCS IL-6 T/C .11 primary
8 Curtiss-Wright Rotary II primary
9 TCCS V-8'T/C II secondary
10 MAN-FM V-8 III primary
11 VW V-8 IV primary
12 VW V-8 IV secondary
13 CVCC V-8 V primary
14 CVCC V-8 V secondary
15 IDI Diesel V-8 - primary
Each of the power plants above were considered for the emission targets shown
and In some cases the secondary target was also considered. The quantity of
exhaust pollutants for the two target levels are shown below measured according
to the CVS-CH test procedure:-
Primary Targets
HC 0.41 g/mile
CO 3.4 g/mile
NO 1.5 g/mile
Secondary Targets
HC 0.41 g/mile
CO 3.4 g/mile
NO 0.4 g/m!le
X
Results of Rating Assessment
The following rating assessment is sub-divided into 26 sections each corres-
ponding to the 26 performance aspects of the rating system. The score allocated
to each of the 15 power plants Is shown in a summary table in each section together
with the weighted rating.
Each section also contains brief notes on the derivation of the various scores.
A complete score table is shown at the end of this section.
55
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Smoke (V/eightlng 1».1*8)
EngIne
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURT ISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Secondary
Pr imary
Secondary
Primary
Score
9
9
8.5
8.5
8.5
6
5.5
6
5.5
6
8.5
8.5
9
9
6
Rating
1*0.32
1*0.32
38.08
38.08
38.08
26.88
21*.62
26.88
21*. 6k
26.88
38.08
38.08
40.32
1*0.32
26.88
The absolute smoke limit at which an engine is limited varies considerably
from country to country and even between manufacturers, some simply complying
with legislative requirements and others aiming for significantly lower levels.
For passenger car use, maximum smoke levels must be selected on an aesthetic basis
in order to avoid public criticism. From European experience, Rlcardo would
recommend that maximum steady state smoke levels of 5-8% opacity should be aimed
for. The combination of these low smoke levels with the high power/weight ratio
of the vehicle should result in the exhaust being at least acceptable from the
candidate power plants. However, the stratified charge engines vary from category
to category in their smoke limited performance.
In rating the conventional gasoline engines with a score of 9 (the best
practical), It was considered that no significant quantity of smoke was emitted:
this also being applicable to the CVCC engines in category V, where the fuel supply
is carburetted. The PROCO engines have low smoke levels due to the early fuel
injection (Score 8.5). Similarly the VW engines were rated good (8,5). The TCCS,
MAN-FM and Rotary engines were considered to have similar smoke characteristics to
the diesel engine and were rated accordingly; the two turbocharged TCCS engines
being down graded i a point due to the need to employ boost controlled fuel
Injection pumps.
2. Particulates (Weighting 2.11*)
Eng ine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
Emission Target
Primary
Primary
Primary
P r i ma ry
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Score
7
7
6.5
6.5
6.5
3
3
3
3
3
7
Rating
11*.98
11*. 98
13-91
13.91
13-91
6.1*2
6.1*2
6.1*2
6.1*2
6.1*2
11*.98
56
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Engine Emission Target Score Rating
VW V-8 Secondary 7 I1*. 98
CVCC V-8 Primary 7 I1*. 98
CVCC V-8 Secondary 7 IMS
DIESEL V-8 Primary 2 4.28
Current data Is still Insufficient to come to a final conclusion concerning
this topic. With a lack of standards to judge by the convent lonal gasol ine engine
running on lead free fuel must be considered good; worthy of seven points, and the
dlesel, with levels of 10 times as high, was considered bad, with a score of two
points. With the limited data available, Ricardo feel confident to predict the
stratified charge engine particulate levels In terms of those already known. It
was considered therefore that the VW and CVCC engines would have similar levels to
those of the conventional gasoline engines as they have similar combustion
characteristics (Score 7), and the TCCS, MAN-FM and Rotary engines approach the
level of the diesel (Score 3). There Is some evidence to indicate that the PROCO
particulate levels may be twice that of the conventional gasoline engine; but still
good (Score 6.5).
If particulate levels are to be the subject of legislation, the lower rated
engines would need after treatment in the form of particulate filters and in this
area further work would have to be carried out.
3. Odour (Weight ing 4.
Engine Emission Target Score Rating
V-8 GASOLINE Primary 6 26.88
IL-6 GASOLINE Primary 6 26.88
PROCO V-8 Primary 6 26.88
PROCO IL-6 Primary 6 26.88
PROCO V-8 Secondary . 6 26.88
TCCS V-8 Primary 4.5 20.16
TCCS IL-6 T/C Primary 4.5 20.16
CURTISS-WRIGHT ROTARY Primary 4.0 17-92
TCCS V-8 T/C Secondary 4.5 20.16
MAN-FM V-8 Primary 3-0 13-44
VW V-8 Primary 5.0 22.4
VW V-8 Secondary 5-0 22.4
CVCC V-8 Primary 6.0 26.88
CVCC V-8 Secondary 6.0 26.88
DIESEL V-8 Primary 4.0 17-92
It was generally agreed that the conventional gasoline power plants are good
from the point of view of odour but were down graded 1 point to 6 on the grounds
that with a cold engine and using catalyst, some problems arose. The PROCO engines
were reported to be good on odour and were awarded the same score as were the CVCC
engines. The diesel engine is known to be relatively poor in this respect and was
awarded 4 points. The MAN-FM power plant, known to have an odour problem, was
awarded 3 points. The VW engines were considered to be acceptable (5 points)
although little data was available and the TCCS were rated marginally better than
the diesel at 4.5 points. The Rotary engine Is also known to have an odour problem
(awarded 4 points) due to poor scavenging of end spaces and poor surface to
volume ratio.
57
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N0x(Weighting 3-92)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURT1SS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
Pr imary
Secondary
Primary
Secondary
Primary
Score
5
5
5
5
5
6
6
7
5
7
7
5
5
5
5
Rati ng
19.6
19
19
,6
.6
19.6
19.6
23.52
23.52
27. M
19.60
27. M
27.M
19.6
19.
19.
.6
.6
19.6
With this performance aspect and with all the others Involving legislative
requirements it was assumed that all the power plants selected for rating could
at least achieve the levels required by such legislation. Where the legal require-
ments were just met, with or without treatment, an acceptable rating was scored
and if any margin was available, with or without aid, an additional one or two
points were awarded. Thus the score table shows the majority of the power plants
being able to achieve the 1.5 g/mile NO level during the CVS-CH cycle with a
score of 5 points, the remainder of the engines having a better score. All the
power plants entered for the secondary level of NO (.^ g/mile) achieved a merit
rating of 5 points.
5. HC(Weighting 3-99)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Pr imary
Primary
Primary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
Score
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
Rating
19-95
19-95
19.95
19.95
19.95
19.95
19-95
19-95
19.95
19.95
19.95
19.95
19-95
19.95
19.95
In this performance aspect all the power plants were considered capable of
achieving an acceptable level of HC during the CVS-CH cycle. No particular engine
stood out as superior to the rest so all achieved a merit rating of 5 points.
58
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6. CO Weighting 3-61)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
PrImary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
Score
5
5
5
5
5
5
5
5
5
5
5
5
5
5
6
Rating
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
18.05
21.66
Here again all the engines were expected to achieve an acceptable level of CO
with the diesel awarded an extra point because of its ability to achieve low levels
without treatment
7. S02(Weighting 3-*8)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
Diesel V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
Score
5
5
5
5
5
5
5
5
5
5
5
5
5
5
2
Rating
17. *
17.*
17-*
17-*
17.*
17.*
17.*
17-*
17.*
17.*
17.*
17.*
17.*
17.*
6.96
This pollutant is totally dependent on the sulphur content of the fuel and the
amount of fuel being burnt. In assessing the diesel for S02 It was assumed that
the sulphur content of U.S. light distillate (DF 1) is similar to that found in
Europe (I.e. 0.2 - 0.5%). In theory the sulphur can be completely extracted from
the fuel but economic considerations have ruled this out to date. The sulphur
content of gasoline is very low (<0.1%) and as no legislation exists all the
gasoline powered engines were rated as acceptable (5 points) and the diesel rated
as bad (2 points).
59
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8. HC Reactivity (Weighting 1.83)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Secondary
Pr Imary
Secondary
Primary
Score
5
5
7
7
7
7
7
7
7
7
5
5
5
5
7
Rating
9.15
9.15
12.81
,81
.81
.81
.81
.81
.81
.81
12,
12,
12.
12,
12.
12.
12.
9.15
9.15
9.15
9.15
12.81
This subject is an important aspect of HC emissions and it has been demon-
strated that HC reactivity from the conventional gasoline engine is 10 times
higher than from the diesel. Thus it was assumed that all the power plants with
gasoline engine characteristics, i.e. VW, CVCC and the two conventional engines
should be awarded 5 points as acceptable and the remainder having diesel com-
bustion characteristics to some degree should merit an award of 7 points.
9. Evaporative Emissions(Weight Ing 1.60)
Engine
V-8 Gasoline
IL-6 Gasoline
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
Score
5.0
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.0
5.0
7.0
Rating
8.00
8.80
8.80
8.80
8.80
8.80
8.80
8.80
8.80
8.80
8.80
8.80
8.00
8.00
11.2
With modern control systems using carbon filter/storage canisters, gasoline Is
an acceptable and practical fuel, which when considered in relation to the power
plants having carburettors warrants them 5 points. The power plants using
gasoline Injection, i.e. all but the CVCC and V-8 conventional gasoline, were each
awarded an extra £ point as It was considered an injection system could achieve
a slightly lower evaporation loss level.
Mid distillates such as used In high speed diesel engines would suffer only
marginal evaporative losses and must merit a good rating (Score 7).
60
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10, Miscellaneous Emissions(Weighting 0.98)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 5 M .
IL-6 GASOLINE Primary 5 4.9
PROCO V-8 Primary 5 4.9
PROCO IL-6 Primary 5 4.9
PROCO V-8 Secondary 5 4.9
TCCS V-8 Primary 5 4.9
TCCS IL-6 T/C Primary 5 4.9
CURTISS-WRIGHT ROTARY Primary 5 4.9
TCCS V-8 T/C Secondary 5 4.9
MAN-FM V-8 Primary 5 4.9
VW V-8 Primary 5 4.9
VW V-8 Secondary 5 4.9
CVCC V-8 Primary 5 4.9
CVCC V-8 Secondary 5 4.9
DIESEL V-8 Primary 5 4.9
At the time of writing of the study none of the power plants was regarded as
producing major quantities of any pollutants other than those already considered
so that all were rated as equal and acceptable.
11. Noise (Orive-by)( Weighting 6.32)
The noise level of a particular engine is largely dependent on the cylinder
bore size, the rotational speed and the rate of cylinder pressure rise. A 1590 kg
passenger car powered by a conventional V-8 gasoline engine can achieve a drive-by
noise level of 71 dB(A) measured at 50 ft. This level was rated good and awarded
seven merit points. The table below shows predicted noise levels for a similar
vehicle powered by the remaining power plants, assessed in relation to the above
parameters together with the merit rating and weighted score.
Engine Emission Target Predicted Score Rating
Vehicle Noise
dBA
V-8 GASOLINE Primary 71 7 44.24
IL-6 GASOLINE Primary 73 6.5 41.08
PROCO V-8 Primary 71 7 44.24
PROCO IL-6 Primary 75 5 3-1.60
PROCO V-8 Secondary 72.5 6.5 41.08
TCCS V-8 Primary 70.5 7.5 47.4
TCCS IL-6 T/C Primary 71 7 44.24
CURTISS-WRIGHT ROTARY Primary 71 7 44.24
TCCS V-8 T/C Secondary 72.5 6.5 41.08
MAN-FM V-8 Primary 72 7 kk.2k
VW V-8 Primary 73 6.5 M.08
VW V-8 Secondary 73 6.5 ^K08
CVCC V-8 - Primary 73 6.5 41.08
CVCC V-8 Secondary 73 6.5 41.08
DIESEL V-8 Primary Ik 5-5 3^.76
Changes to engine configuration such as more advanced crank-case design may
modify these predictions and the power plants having the most severe noise problem
ans likely to benefit most from such modification.
61
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12. Package Volume(Weighting 2.61)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 7 18.2?
IL-6 GASOLINE Primary 7 18.27
PROCO V-8 Primary 7 18.27
PROCO IL-6 Primary 5 13.05
PROCO V-8 Secondary 6 15.66
TCCS V-8 Primary 5 13.05
TCCS IL-6 T/C Primary *» 10.*»*4
CURT ISS-WRIGHT ROTARY Primary 9 23.1*9
TCCS V-8 T/C Secondary *4.5 11-75
MAN-FM V-8 Primary 6 15.66
VW V-8 Primary 7 18.27
VW V-8 Secondary 7 18.27
CVCC V-8 Primary 6 15.66
CVCC V-8 Secondary *t.5 11.75
DIESEL V-8 Primary 5-5 I1*.36
Box volumes as calculated during the configuration phase of the study are
1i sted below:-
3 3
Engine Emission Target ft m
PROCO V-8 Primary 9-7 .275
PROCO IL-6 Primary 11.9 -337
PROCO V-8 Secondary 10.7 .303
TCCS V-8 Primary 11.9 .337
TCCS IL-6 T/C Primary 12.2 .3*46
CURTISS-WRIGHT ROTARY Primary 8.5 .2k
TCCS V-8 T/C Secondary 12.1 .3*43
MAN-FM V-8 Primary 10.83 .307
VW V-8 ' Primary 10.0 .28**
VW V-8 Secondary 10.0 .28*4
CVCC V-8 Primary 11.*» .322
CVCC V-8 Secondary 12.8 .362
DIESEL V-8 Primary 11.3 .320
All are given merit ratings according to their calculated box volumes based on
a rating of good for the conventional gasoline engines. Taken into account In the
rating was the length of the six cylinder In-line engines as this was believed to
be important to safety regulations.
13. Package Welght(WelghtIng 2.59)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 6 15.5*4
IL-6 GASOLINE Primary 7 18.13
PROCO V-8 Primary 6 15.5k
PROCO IL-6 Primary 6 15.5*4
PROCO V-8 Secondary 6 15.5*4
TCCS V-8 Primary 5-5 1*4.25
TCCS IL-6 T/C Primary 6 15.5*4
CURTISS-WRIGHT ROTARY Primary 8 20.72
62
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Engine Emission Target Score Rating
TCCS V-8 T/C Secondary 5 12.95
MAN-FM V-8 Primary 5 12.95
VW V-8 Primary 6 15. 51*
VW V-8 Secondary 6 15.5*»
CVCC V-8 Primary 6 15. 5^
CVCC V-8 Secondary 5.5 1**.25
DIESEL V-8 Primary 4.5 11 .66
The following table shows the estimated weight for each of the power plants
considered In this study. If the six-cylinder European type gasoline engine is
considered to have a rating of good (Score 7) all the remainder, apart from the
rotary engine, bear a weight penalty and were thus accorded lower scores.
1 b . kg .
V-8 GASOLINE 5^0
IL-6 GASOLINE ^50 204
PROCO V-8 551 250
PROCO IL-6 580 263
PROCO V-8 Secondary 571 259
TCCS V-8 602 273
TCCS IL-6 T/C 573 260
ROTARY 330 150
TCCS V-8 T/C Secondary 631 286
MAN-FM V-8 662 300
VW V-8 550 250
VW V-8 Secondary 550 250
CVCC V-8 550 250
CVCC V-8 Secondary 602 273
DIESEL 700 320
14. Fuel Economy (Weighting 12.2)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 6.5 79-3
IL-6 GASOLINE Primary 7 85.4
PROCO V-8 Primary 7-5 91.5
PROCO IL-6 Primary 7.5 91.5
PROCO V-8 - Secondary 6.5 79-3
TCCS V-8 Primary 7.0 85. 4
TCCS IL-6 T/C Primary 7-0 85. 4
CURTISS-WRIGHT ROTARY Primary 5-5 67.!
TCCS V-8 T/C Secondary 5-5 67.!
MAN-FM V-8 Primary 7-5 91-5
VW V-8 Primary 6.5 79-3
VW V-8 Secondary 6.0 73.2
CVCC V-8 Primary 6,5 79.3
CVCC V-8 Secondary 6.0 73.2
DIESEL V-8 Primary 8.5 103.7
This section was considered the most important and was awarded the highest
weighting factor. The definitions of the various fuel consumption ratings were
changed from the previous dlesel survey to the scale shown below as it was con-
63
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sidered that 25 mpg, rated 9 points in the earlier study, was impossible to
achieve, with gasoline as the fuel.
Fuel Economy mpg. 1/100 km Rating
0 (totally unacceptable)
5.25 ^.81 1
2 (bad)
8.75 26.89 3
k (poor)
13.125 17.92 5 (acceptable)
6
17.5 13.M» 7 (good)
8
21.87 10.76 9 (best practical)
10 (perfect)
Predicted fuel economy levels for a 1590 kg passenger car were based on
estimated and measured fuel consumptions from each of the power plants. The six
cylinder European gasoline engine, with injected fuel, was given a good rating
(7 points) and several of the stratified charge systems were rated as good or
better. The dlesel was considered to be almost 'best practical1 and awarded 8i
points. Of course, the diesel engine had an advantage in this respect since the
fuel economies are rated on a volumetric basis, and dlesel fuel has a higher
specific gravity. A full list of the estimated fuel consumption and economy levels
obtainable during the CVS-CH test cycle are as follows:-
1/100 km mpg
V-8 GASOLINE lif.6 16
IL-6 GASOLINE 13.5 17'.*»
PROCO V-8 12.5 18.7
PROCO IL-6 12.75 18.*»
PROCO V-8 Secondary H».2 16.5
TCCS V-8 13.8 17.0
TCCS IL-6 T/C 13.8 17.0
ROTARY 16.75 1^.0
TCCS V-8 T/C Secondary 16.75 1^.0
MAN-FM V-8 12.3 19-0
VW V-8 \k.2 16.5
VW V-8 Secondary 15.13 15-5
CVCC V-8 13.95 16.8
CVCC V-8 Secondary 15.6 15.0
DIESEL V-8 11.0 21 .0
15. Fuel Cost (Weighting 5.*»0)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 5 27.0
IL-6 GASOLINE Primary 5 27.0
PROCO V-8 Primary 5 27.0
PROCO IL-6 Primary 5 27.0
PROCO V-8 Secondary 5 27.0
TCCS V-8 Primary 5 27.0
TCCS IL-6 T/C Primary 5 27.0
-------
Engine
Emission Target
Score
Rating
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Primary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
5
5
5
5
5
5
5
6
27.0
27.0
27.0
27.0
27.0
27.0
27.0
32.4
In spite of the trend towards higher fuel costs it was assumed that the
situation for all the power plants employing gasoline as fuel must rate as
acceptable. All these engines were required to run on lead free fuel to preserve
catalyst life, with the exception of the CVCC engine which, having thermal
reactors, could tolerate leaded fuel. This factor however, was not considered
to constitute a measurable advantage to the CVCC power plants. The diesel engine
was awarded 1 extra point (Score 6) as the light distillate fuel (DF 1) has a
currently lower price at the pump although this may always be subject to
artificial manipulation by taxation.
16. Vehicle First Cost(Weight!ng 4.65)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
P r i ma ry
Secondary
Primary
Primary
Pr imary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
Score
6
6
4.5
5.5
4.0
4.0
4.0
5.0
2.5
4.5
3.5
3.0
6.0
5.0
5.0
Rating
27.9
27.9
20.93
25.57
18.6
.6
.6
18.
18.
23.25
11.63
20.93
16.28
13-95
27.90
23.25
23.25
It Is estimated that for a conventional V-8 powered passenger car the power
plant is responsible for 25% of the total vehicle cost and the first cost of such
a vehicle was rated as better than acceptable (Score 6). For this aspect the man-
ufacturing cost of each power plant was estimated and rated accordingly. The
following table shows the cost estimates for each engine and It can be seen that
apart from the primary target of the CVCC all the power plants Incur a cost penalty
in relation to the conventional gasoline engines; the TCCS secondary engine and
the two VW engines being between 40 and 6$% more expensive.
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
Manufacturing Cost
% 595
598
741
664
65
-------
PROCO V-8 Secondary
TCCS V-8
TCCS IL-6 T/C
ROTARY
TCCS V-8 T/C Secondary
MAN-FM V-8
VW V-8
VW V-8 Secondary
CVCC V-8
CVCC V-8 Secondary
DIESEL V-8
Manufacturing Cost
% 827
811
827
667
985
756
844 *
899 *
600
670
701
* Deduct approx. % 80 for electronic fuel injection.
The merit rating for costs was based on the following:-
Cost % Score
1000
900
800
700
600
500
1*00
17. Maintenance Cost( Weight ing 4.35 )
0
1
2 (bad)
3
4 (poor)
5 (acceptable)
7
8
9
10
(good)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Secondary
Primary
Secondary
Primary
Score
5
5
4.5
4.5
,0
.0
3-
3.
3-0
2.5
3.0
4.0
4.0
3.0
6.0
5.5
6.0
Rati ng
21.75
21.75
19.57
19-57
13.05
13-05
13.05
10.88
13.05
17.40
17-40
13-05
26.10
23.93
26.10
Maintenance costs for conventional gasoline engines are regarded as satis-
factory and experience suggests that the diesel should be better and was rated
one point higher (Score 6). The remaining stratified charge engines were rated less
than acceptable mainly because of the high cost of catalytic exhaust systems, the
66
-------
exceptions being the CVCC engines which were rated as better than the conventional
gasolIne.
The rotary engine was rated particularly lowly (2.5 points) because apart from
catalysts It was considered the engine may require more than average mechanical
attention.
18. Startabllity(Welghting 4.85)
Eng ine
V-8 GASOLINE
IL.6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
Primary
P rI ma ry
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
P r i ma ry
Primary
Secondary
Primary
Secondary
Primary
Score
7
7
7
7
7
8
8
5
8
7
6
6
6.5
6.5
5
Rati ng
33.95
33-95
33.95
33.95
33.95
38.80
38.80
24.25
38.80
33.95
29.10
29.10
31.53
31.53
24.25
With the ability to start instantaneously under most environmental conditions
experienced In America the conventional gasoline engines should merit a very high
rating but the hot starting of low emissions vehicles can be poor, and Is not
likely to Improve substantially beyond today's levels. However both versions of
the conventional engines were rated good and awarded seven points. At the other
end of the range the diesel was rated only as acceptable, largely due to the delay
in cold starting due to the heater plug lead time required, and the rotary engine,
known to be a sometimes doubtful starter, was also rated acceptable. VW and CVCC
engines were rated just below the conventional engines and the TCCS engines were
rated very good (Score 8).
19- Hot Drlveabillty(Weighting 4.48)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
P r i ma ry
Primary
P r i ma ry
Primary
Secondary
P r i ma ry
Primary
P rI ma ry
Secondary
Primary
Primary
Secondary
P r i ma ry
Secondary
P r i ma ry
Score
8
8
8
8
8
8
7
7
7
8
8
8
7
5
7
Rating
35.84
35.84
35.84
35.84
35.84
35.84
31.36
31.36
31.36
35.84
35.84
35.84
31.36
22.40
31.36
67
-------
Hot driveabllity of the conventional gasoline engines was rated at 8 points;
better than good, almost best practical, and all but one of the remaining power
plants was rated as good or better. The exception was the CVCC secondary emissions
target engine which, because of a high degree of EGR required, was considered to be
just acceptable (Score 5).
20. Cold Driveabllity (Weighting 3.52)
Engine Emission Target Score Rating
V-8 GASOLINE Primary k 14.08
IL-6 GASOLINE Primary 6 21.12
PROCO V-8 Primary 7 24.64
PROCO IL-6 Primary 7 24.64
PROCO V-8 Secondary 7 24.64
TCCS V-8 Primary 7 24.64
TCCS IL-6 T/C Primary 6 21.12
CURTISS-WRIGHT ROTARY Primary 6 21.12
TCCS V-8 T/C Secondary 6 21.12
MAN-FM V-8 Primary 7 24.64
VW V-8 Primary 7 24.64
VW V-8 Secondary 7 24.64
CVCC V-8 Primary 4 14.08
CVCC V-8 Secondary 4 14.08
DIESEL V-8 Primary 7 24.64
With flat spots due to carburation problems at cold temperatures the V-8
conventional gasoline engine was regarded as poor (4 points). With gasoline
Injection the remaining power plants were rated up to good (scoring 6 or 7) with a
rating of good for the diesel engine. The two CVCC candidates, being carburetted,
were rated as poor for the same reasons as the conventional gasoline engine.
21. Torque Back-up (Weighting 1.98)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 7 13.86
IL-6 GASOLINE Primary 6.5 12.87
PROCO V-8 Primary 6.5 12.87
PROCO IL-6 Primary 7 13.86
PROCO V-8 Secondary 5 9-90
TCCS V-8 Primary 7 13.86
TCCS IL-6 T/C Primary 5.5 10.89
CURTISS-WRIGHT ROTARY Primary 6 11.88
TCCS V-8 T/C Secondary 6.5 12.87
MAN-FM V-8 Primary 7 13.86
VW V-8 Primary 4 7.92
VW V-8 Secondary 4 7-92
CVCC V-8 Primary 7 13.86
CVCC V-8 Secondary 6.5 12.87
DIESEL V-8 Primary 7 13.86
All the power plants varied in the amount of torque back-up available. Those
cons.idered good (7 points) having 25% torque back-up, were the V-8 conventional
gasoline engine, the PROCO IL-6, TCCS and CVCC primary V-8 engines, the MAN-FM and
the diesel engine. Marginally inferior were the IL-6 gasoline, PROCO V-8 primary;
68
-------
TCCS and CVCC secondary engines each having about 20% torque backrup (Score 6.5).
The remainder were satisfactory or better with the exception of the VW engines
which have a curious torque curve with less than 10% back-up and were consequently
rated poor with a score of 4.
22. Durability (Weighting 4.80)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 5 2k.Q
IL-6 GASOLINE Primary 5 24.0
PROCO V-8 Primary 4.5 21.60
PROCO IL-6 Primary 4.5 21.60
PROCO V-8 Secondary 3 14.40
TCCS V-8 Primary 3 14.40
TCCS IL-6 T/C Primary 3 14.40
CURTISS-WRIGHT ROTARY Primary 2.5 12.00
TCCS V-8 T/C Secondary 2.5 . 12.00
MAN-FM V-8 Primary 4.5 21.60
VW V-8 Primary 4 19.20
VW V-8 Secondary 3 14.40
CVCC V-8 Primary 7 33-60
CVCC V-8 Secondary 6.5 31.20
DIESEL V-8 Primary 7 33-60
Apart from reservations concerning the Rotary engine It was considered that
all the power plants could achieve 100,000 miles mechanically without difficulty.
However, the limitation was expected to be in the catalytic exhaust systems.
Although attempts to Improve catalyst life have so far not been particularly
successful the durability of the conventional gasoline engines was considered
to be acceptable. On this basis the remaining engines were judged with the diesel
and CVCC power plants achieving the highest rating as no catalysts are involved.
The remaining power plants all received lower than acceptable ratings, according
to the severity of the demand on the catalysts. The TCCS secondary emissions
engine and the Rotary engine only rated a score of 2.5 points due to mechanical
as well as other doubts.
23- Heat Loss (Weighting 2.18)
!
Engine Emission Target Score Rating
V-8 GASOLINE Primary 7 ' '' 15.26
IL-6 GASOLINE Primary 7 15-26
PROCO V-8 Primary 7 15-26
PROCO IL-6 Primary 7 15-26
PROCO V-8 Secondary 7 15.26
TCCS V-8 Primary 5 10.90
TCCS IL-6 T/C Primary 5 10-90
CURTISS-WRIGHT ROTARY Primary 6 13.08
TCCS V-8 T/C Secondary 7 15.26
MAN-FM V-8 Primary 5 10.90
VW V-8 Primary 7 15.26
VW V-8 Secondary 7 15.26
CVCC V-8 Primary 6 13.08
CVCC V-8 Secondary 6 13.08
DIESEL V-8 Primary 5 10-90
69
-------
For this aspect, the vehicle configuration for the various power plants was
assumed to contain an adequate cooling system allowing for the Increased coolant
heat losses for some of the engines at full load. It is know, for instance, that
the diesel engine may reject 25% more heat to the radiator than the equivalent
gasoline engine and that some of the stratified charge engines will also have a
higher full load heat rejection than conventional gasoline engines. The rating
in this section, therefore, was mainly concerned with light load and idle heat
rejection to enable the vehicle Interior heating to be accomplished satisfactorily.
In this respect all the power plants were awarded 'good1 ratings except for
the diesel, the two primary TCCS engine and the MAN-FM engine, all known to have
heat losses at Idle. These latter engines were however considered satisfactory
and awarded 5 points.
low
2k. Fire Risk (Weighting 3-55)
Engine
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL V-8
Emission Target
P r i ma r y
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Primary
P r i ma ry
Secondary
Primary
Secondary
Primary
Score
5
5
5
5
5
5
5
5
5
5
5
5
4.5
4.5
6
Rating
17.
17.
17.
17.
17.
17.
17.
17.
17.
17.
17.
17,
15.
15.
75
75
75
75
75
75
75
75
75
75
75
75
98
98
21.30
Apart from the diesel engine all the power plants considered in this survey use
gasoline fuel which, due to its high volatility, can contribute to fire risk. It
was assumed for the purposes of this rating system that most of these gasoline
powered vehicles would rate as acceptable. However, the CVCC engines, with their
high heat capacity thermal reactors might contribute a marginally higher risk and
were therefore down-graded i a point to k.$. The diesel engine was given one more
point (Score 6) as the relatively low volatility of the fuel was considered to
contain a lower degree of risk.
25. Idling Noise (Weighting 3.83)
Engi ne
V-8 GASOLINE
IL-6 GASOLINE
PROCO V-8
PROCO IL-6
PROCO V-8
TCCS V-8
TCCS IL-6 T/C
CURTISS-WRIGHT ROTARY
TCCS V-8 T/C
Emission Target
Primary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Secondary
Score
8
8
5.5
5
5
5
5
7
4.5
Rati ng
30
30
21
19
19
19
19
26
,6k
.64
.07
,15
,15
,15
,15
,81
17.24
70
-------
Engine Emission Target Score Rating
MAN-FM V-8 Primary 5 19-15
VW V-8 Primary 6 22.98
VW V-8 Secondary 6 22.98
CVCC V-8 Primary 8 30.6*»
CVCC V-8 Secondary 8 30.6k
DIESEL V-8 Primary k 15-32
Idle noise of the conventional gasoline engine is low in terms of both
objectionabl11ty and overall noise level and must approach the best practical level
that a power plant can achieve. The CVCC engine, having similar combustion
characteristics at idle, must also rate highly. All score 8 points. At the
other end of the scale, the dlesel, although not excessively high in noise level,
produces a harsh unpleasant sound and was rated 'poor1 at k points.
The stratified charge engines employing direct injection (PROCO, TCCS and
MAN-FM) were all rated more or less acceptable. Although the combustion
characteristics were considered similar to the dlesel a combination of lower
pressures and smoother cylinder pressure diagrams generally allowed i to 1£ points
higher rating.
Of the remaining power plants the rotary was considered good (Score 7) and
the VW engines less than good (6 points).
26. Vibration and Torque Recoil (Weighting 2.18)
Engine Emission Target Score Rating
V-8 GASOLINE Primary 8 I?-1*1*
IL-6 GASOLINE Primary 7-5 16.35
PROCO V-8 Primary 6.5 U.17
PROCO I.L-6 Primary 6 13-08
PROCO V-8 Secondary 6.5 I1*. 17
TCCS V-8 Primary 6 13.08
TCCS IL-6 T/C Primary 5-5 11-99
CURT ISS-WRIGHT ROTARY Primary 7-5 16.35
TCCS V-8 T/C Secondary 6 13.08
MAN-FM V-8 Primary 5 10.9
VW V-8 Primary 8 17-^
VW V-8 Secondary 8 17.M
CVCC V-8 Primary 8 17.^
CVCC V-8 Secondary 8 17.kk
DIESEL V-8 Primary 6 13.08
The aspect of vibration and torque recoil is undoubtedly a major contributor
to the feel or refinement of a vehicle.
A V-8 power plant having similar combustion characteristics to a conventional
gasoline engine should be quiet enough as to make the user unaware of any
reciprocating motion. In this respect it was considered that the VW and CVCC
power plants were equal to the conventional V-8 gasoline engine and rated at 8
points being almost the best practical. Only marginally Inferior (Score 7.5) were
the IL-6 gasoline and Rotary engines.
The direct Injection engines, including the dlesel, were all rated lower,
71
-------
but better than acceptable, due to running unthrottled and having slightly rougher
torque characteristics.
1. Smoke
2. Particulates
3. Odour
4. NO
5. HC
6. CO
7. SO
8. HC Reactivity
9. Evap. Emissions
10. Misc. Emissions
11. Noise (Drive-by)
12. Package Volume
13. Package Weight
14. Fuel Economy
15. Fuel Cost
16. Vehicle First Cost
17. Maintenance Cost
18. Startability
19. Hot Driveability
20. Cold Driveability
21. Torque Back-up
22. Durability
23. Heat Loss
24. Fire Risk
25. Idling Noise
26. Torque Recoil
FINAL RATINGS FOR EACH ASPECT
0
A*
9
7
6
5
5
5
5
5
5
7
7
e
6.5
5
6
5
7
8
4
7
5
7
5
8
8
/
**
9
7
6
5
5
5
5
5 B
5
6.5
7
7
7
5
6
5
7
8
6
6.5
5
7
5
8
7.5
./
$
8.5
6.5
6
5
5
5
5
B B
5
7
7
6
7.5
5
4.5
4.5
7
8
7
6.5
4.5
7
5
5.5
6.5
•9 (
' 4?
8.5
6.5
6
5
5
5
5
B B
5
5
5
6
6.5
5
5.5
4.5
7
8
7
7
4.5
7
5
5
6
^
1 4?
8.5
6.5
6
5
5
5
5
B B
5
6.5
6
6
7
5
4
3
7
8
7
5
3
7
5
5
6.5
•9
\°°
6
3
4.5
6
5
5
5
B B
5
7.5
5
55
7
5
4
3
8
8
7
7
3
5
5
5
6
> c
55
3
4.5
6
5
5
5
B B
5
7
4
6
55
5
4
3
8
7
6
5.5
3
5
5
5
5.5
r \(
*>
? $
6
3
4
7
5
5
5
B B
5
7
9
8
5.5
5
5
2.5
5
7
6
6
2.5
6
5
7
7.5
V
* e<
£
5.5
3
45
5
5
5
5
BB
5
6.5
4.5
5
7.5
5
2.5
3
8
7
6
6.5
2.5
7
5
4.5
6
^ \C
' *
6
3
3
7
5
5
5
BB
5
7
6
5
6.5
5
4.5
4
7
8
7
7
4.5
5
5
5
6
;/
/
8.5
7
5
7
5
5
5
BB
5
6.5
7
6
6
5
3.5
4
6
8
7
4
4
7
5
6
8
-------
RESULTS
The product of the rating and the weighting for each performance aspect was
summed for each power plant and the results are shown In the table below:-
Encilne Final Score Primary Target Secondary Target
(to nearest whole Position Position
number)
V-8 GASOLINE 616 2
IL-6 GASOLINE 627 1
PROCO V-8 615 3
PROCO IL-6 599 5
PROCO V-8 576 2
TCCS V-8 566 9
TCCS IL-6 T/C 5*»7 11
CUFTISS-WRIGHT ROTARY 552 10
TCCS V-8 T/C 517 b •
MAM-FM V-8 571* 8
VW V-8 586 6
VW V-8 561 3
CVCC V-8 613 k •
CVCC V-8 583 1
DIESEL V-8 581 7 *
* Not strictly comparable due to different fuel,
These results are revealing In that they indicate how small the relative
differences are between the power plants. With the rating methodology employed a
power plant rated as acceptable in each of the performance aspects would achieve
a score of 500 but If a zero were to occur In any score, that power plant must be
rejected whatever Its final total. As none of the candidates rate zero in any of
the performance aspects and all achieved a total score in excess of 500, all must
be considered as viable alternatives.
The highest scoring power plant, the conventional European type IL-6 gasoline
engine scored approximately 20% more points than the lowest, the TCCS secondary
emissions engine. Of particular interest is the score attained by the PROCO primary
emissions engine which attained a similar rating to the conventional V-8 gasoline
engine. With a slightly lower total score than the PROCO V-8 engine, came the CVCC
primary engine followed by the PROCO IL-6. The position of the IDI dlesel in the
table is not directly comparable with the other power plants since the fuel is
different from the other power plants, but was included in the rating, so that a
comparison could be made with the previous dlesel survey.
Of the candidates for the secondary emissions target (O.k g/mile NO ) the
CVCC and PROCO engines were awarded greatest merit. However, by the definition of
this methodology, none of the other combustion systems could be completely ruled
out.
CONCLUSIONS
The rating methodology evolved has allowed the different power plants to be
compared on a numerical basis. Its application to the fifteen candidate power
plants selected for appraisal has resulted In them all being proved viable for the
proposed 3500 Ib vehicle to some degree.
73
-------
The most suitable engines, those with the highest total score, were the con-
ventional gasoline engines and the PROCO V-8 primary emissions stratified charge
engine, which came second to the IL-6 gasoline engine.
For the secondary emissions target the CVCC secondary engine achieved the
highest score followed by the PROCO secondary engine.
-------
A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
SECTION J
DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS
FOR FUTURE WORK
-------
DISCUSSIONS AND RECOMMENDATIONS
GENERAL DISCUSSION
The unthrottled stratified charge engine has been sought throughout this
century as the epitome for fuel economy. The advent of exhaust emission legis-
lation increased the fervour of the search and, indeed, Improvements In economy
with unthrottled engines have been demonstrated. Conversely, the exhaust emission
legislation has also condemned the unthrottled stratified charge engine, due to Its
inherent characteristics of emitting high HC emissions In spite of the low CO and
NO emissions. This survey has Indicated that the hydrocarbon emissions at low
loads cannot be avoided, due to the quenching of some of the air and fuel mixture
by the cylinder walls and the low gas temperatures during combustion. A catalyst
is needed to remove the emissions in the exhaust system, but even here there are
problems. Since the exhaust temperature Is low, the catalyst efficiency Is lower
than in a conventional gasoline engine.
The only practical approach to reducing HC emissions from stratified charge
engines is to throttle the induced air, so that the mixture, in the cylinder has an
air fuel ratio of around 1? to 20. In this region, In-cylinder formation of HC
emissions is reduced to a minimum, exhaust temperatures are relatively high, and
there is sufficient oxygen in the exhaust gas so that further oxidation of the
HC can be completed in the exhaust system. This approach has been followed In
Ford PROCO, Honda CVCC, VW and Porsche engines. The only exception among the
principal stratified charge developments has been Texaco TCCS and MAN-FM, where
unthrottled operation has been maintained under most conditions. The TCCS engines
have high HC emissions and the high degree of exhaust treatment which is required
to meet emission targets Is a direct result of this decision. HC emissions of the
MAN-FM are good, but this engine has not reached the stage of an automotive
application.
The direct injection stratified charge engines such as PROCO, TCCS and MAN-FM
appear to have the greatest potential for low fuel consumption. The higher gas
velocities which occur during the combustion in divided chamber engines (CVCC, VW,
Porsche, etc.) lead to higher heat transfer and some loss in fuel economy. The
need to throttle most of the engines for HC control has also Involved an economy
sacrifice. The end result is that the fuel economy advantage of the best D.I.
engine (i.e. PROCO) over the good gasoline engines is relatively small. The TCCS
engines do not emerge as the best In fuel economy due to various trade-offs In
meeting the HC standard. Exhaust gas reelrculation Is used, partially to reduce
NO and partially to increase exhaust temperatures and aid in HC control. The
divided chamber engines have fuel economies similar, or slightly worse than the
best conventional gasoline engines. Category IV engines (e.g. VW and Porsche) are
at a relatively early stage of development, and some small Increase in economy
may still be possible. However, category V engines (e.g. Honda CVCC) are unlikely
to improve on the economy of good gasoline engines if thermal reactors are used to
control HC and CO. It Is important to realise that the energy In the fuel can only
be used once, either as output work due to better fuel economy, or else as exhaust
energy to help control HC and CO emissions, BUT NOT BOTH. If a stratified charge
engine emerges In the future, which can give better economy than a good gasoline
engine, then it will almost certainly not use a thermal reactor for exhaust control,
and a catalyst is the only alternative. This Is disappointing, as the durability
of thermal reactors Is better than that of catalysts, and likely to remain so.
The question must Inevitably be raised: Can any stratified charge engine meet
O.'H g/mile HC without catalytic reactors, while Improving on the economy of the
existing good gasoline engines? The answer which emerges from this survey is : No,
and there does not appear to be any likelihood of such an engine emerging If it Is
75
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based on an a spark Ignition combustion process. As compression ratio increases,
and moves towards compression ignition, the HC problem does reduce to some extent,
but the level of 0.^1 g/mile HC is still unattainable. The good results from
MAN-FM In this respect are probably related to the higher CR compared to all
the other engines surveyed.
The nitrogen oxide emissions of stratified charge engines are universally
lower than for conventional gasoline engines. The divided chamber engines in
categories IV and V can often achieve the primary targets (I.e. 1.5 g/mile)
without EGR. The direct injection engines have varied performance in this respect,
TCCS and MAN-FM having low NO , but PROCO being substantially higher. The
particularly attractive feature of stratified charge engines is their ability to
meet the secondary emission target of O.k g/mile NO . PROCO, TCCS and Honda CVCC
have all demonstrated this ability In a vehicle, but the quantities of EGR required
have involved considerable losses in performance and drlveabi1ity, and in the case
of TCCS and CVCC, an additional large economy sacrifice. The PROCO, due to its
inherent fast burning, has only a small loss In economy at the secondary target.
Perhaps the most significant conclusion to emerge from this survey Is the practical
and theoretical advantages of Category IV engines (e.g. VW and Porsch) at low NO
levels. VW and Porsche have both demonstrated NO levels below 1 gm/mile without
EGR. The secondary targets could probably be achieved with lower penalties in
performance and driveabllity than engines in other categories. At the moment, the
greatest problem of the VW and Porsche engines is mechanical complexity, due to
the requirement for two injection systems, one for port injection and the other for
pre-chamber injection. However, this survey has revealed certain alternatives
which, with development, might reduce the Injection system cost, such as the
Schlamann rubber pump and the Bonner pumpless injector. Meeting the secondary
emission targets will almost certainly lead to further reliance on catalysts to
remove HC and CO.
Some of the stratified charge engines reviewed bear similar characteristics
to the diesel, particularly those In categories II and III (TCCS and MAN-FM) and
some in category IV. The full load performance of these engines is limited by
the onset of smoke, and the difference with the diesel engine Is principally in
the ability to operate on gasoline as a fuel. Partlculate emissions from these
engines are higher than the conventional gasoline engines.
Some types of stratified charge engines have high noise levels, but this
problem may occur in different regions of the power spectrum. If the charge
stratification Is arranged by air motion, i.e. by directed ports such as PROCO, or
medium sized swirl chambers, then full load noise is usually relatively high. The
air motion causes higher turbulence levels than in the gasoline engine, and the
mixture burns at an excessive speed. The TCCS and MAN-FM engines are an exception
to this rule, as the combustion rate is controlled, either directly or Indirectly
by the rate of fuel injection. Engines with small pre-chambers (around 10%) such
as Porsche and Honda have lower full load noise levels, as the gas velocities and
turbulence at the beginning of combustion are little greater than In the conventional
gasoline engine. While the unthrottled engines such as MAN-FM and TCCS have low
noise levels at full load, Idling noise is usually higher than the gasoline engine.
This may mean that idling noise Is controlled mainly by maximum cylinder pressure
rather than rate of pressure rise. Typical maximum cylinder pressures would be
20 bar for an unthrottled engine and only 7 bar for an engine throttled to an air
fuel ratio of 15. Noise from Injection equipment, may also be significant during
idling.
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Alternative Engines
Two-stroke stratified charge engines have been studied under Category VII,
and though some have made distinct Improvements In emissions with respect to
the conventional 2 stroke, they still do not equal their *» stroke counterparts.
Many of these studies have centred on the piston ported engine, where the control
of the air movement is difficult. A more promising arrangement Is one similar to
Helntz using unlflow 2 stroke, with a poppet valve as one port, and the piston
controlling the ports in the liner, as the other. Arranging charge stratification
within this type of engine Is less difficult, although the basic problem of high
HC, associated with stratified charge engines is still not solved. In addition,
the: mechanical complexity of the engine is Increased. The only advantage compared
to a ^ stroke engine is a reduction in overall engine size.
The two piston Kushul engine is an interesting development, and the reported
fuel consumption results are exceptionally good. This area might warrant further
study.
In view of the fundamental problem of HC emissions with stratified charge
engines, uncovered by this survey, some alternative to stratified charge should be
sought. The source of the HC formation Is linked with spark ignition of the
mixture In the cylinder. The flame initiated at the plug Is easily doused by very
lean mixtures, leaving the unburnt fuels to be released as HC. Therefore combustion
which Is controlled by a flame front must be avoided. The only two recognised
methods of causing combustion In engines are by a compression or spark ignition,
and the problem associated with compression Ignition are well known. The clear
Indication from this survey is that other methods of causing combustion In engines
should be studied. The most obvious alternative would be to catalyse the air fuel
mixture. If the mixture were passed through a catalyst during combustion, then
HC emissions would be completely removed. At the end of the compression stroke
the: gas pressure and temperature are more favourable for oxidation than in an
exhaust system. Furthermore, stratification would not be required as a homogeneous
lean mixture of any mixture strength could be oxidised. The engine load could be
simply regulated by the amount of fuel admitted to the engine. A possible
arrangement for catalysed combustion Is shown in Fig. Dl. The induced air has an
Imparted swirl of 2 times engine speed. This swirl level is accelerated into the
piston cup at tdc. The top of the cup is enclosed by a catalysed wire mesh with
a further surface bisecting the cup. At tdc, fuel is injected through a two hole
noz:zle Into the swirling air below the wire mesh, and is then swept through the
bis.ectlng mesh and burnt. During the expansion and exhaust strokes the burnt
mixture coming from the cup Into the remainder of the cylinder must pass through
the: mesh on the top of the piston. Therefore HC emissions are controlled. The
mesh might also need to be pre-heated before starting the engine. This idea has
not: received a detailed feasibility study, and Is simply included here in an
attempt to promote Ideas for alternatives to spark ignition.
Other Results of Survey
Some general comments can be made regarding the review of mathematical models
In each category. While the number of models was large, the actual experimental
data on which the models were based was extremely limited. The most critical
area In this respect was heat transfer to the cylinder walls. This has a funda-
mental effect on fuel consumption, performance and NO emissions. Many of the
models completely Ignored heat transfer, while othersXused the empirical relations
established by V/oschni, Annand and Eichelberg on diesel and gasoline engines. It
is very doubtful if these relations can be applied, in view of the different gas
77
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densities, compositions, and velocities In stratified charge engines. It Is
suggested that further combustion photography work and Instantaneous heat transfer
experiments should be conducted so that reliable empirical results can be
established and so justify the complexity of the computer simulations which are
already developed. Droplet formation and evaporation from Injectors Is another
area where experimental data is missing.
Discussion on Application to Motorcycles
Existing two stroke motorcycle engines will experience great difficulty in
achieving the target emission levels. At present many four stroke engines are also
outside the target, although this is the result of over-enrichment of the
carburettor, to give good performance and driveabl11ty. If a small loss In
acceleration is accepted, the carburettor mixture strength of the motorcycle
engine can be set leaner, and the emission targets can be achieved with ease.
Ricardo tests have shown that this approach can also Increase fuel economy by up
to 50%. Therefore, It is not practical to consider stratified charge versions of
motorcycle engines at these emission targets, since the extra mechanical complexity
is not justified. The four stroke motorcycle engine must work through the same
evolutionary process as that of the car engine in the period of the later 1960's
and early 1970's, I.e. better manufacturing tolerances on carburettor settings and
Ignition timings, resulting In engine operation at higher air/fuel ratios.
Eventually, as motorcycle emission levels become more severe, stratified charge
engines must be considered. The only practical arrangements would be the Honda
CVCC process for cylinder sizes greater than 200 cc and the Kushul process for the
flat four arrangement (probably above 750 cc).
Results of Rating Methodology
The stratified charge combustion systems which were considered to be viable
power plants were configured, and the various aspects of the performance were
estimated. Finally, the engines were rated by a scoring technique based on all
aspects of the engine and vehicle performance. The results are shown below:-
Eng ine
GASOLINE V-8
GASOLINE IL-6
PROCO V-8
PROCO IL-6
PROCO Vr8
TCCS V-8
TCCS IL-6
TCCS V-8
CURTISS-WRIGHT
MAN-FM V-8
VW V-8
VW V-8
CVCC V-8
CVCC V-8
DIESEL
Primary target
Primary target
Secondary target
Primary target
Primary target
Secondary target
Primary target
Primary target
Primary target
Secondary target
Primary target
Secondary target
Primary target
Points
616
627
615
599
576
566
Posi tion
552
517
586
561
613
583
581
Primary
2
1
3
5-
9
10
11
8
6
7
Secondary
3
1
The results from the first k engines were very close, and raised many questions,
particularly with regard to the weighting of each aspect of vehicle performance.
78
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Any alterations of the weighting can significantly affect the overall result. A
number of comments are listed below.
1. Each of the components of the legislated exhaust emissions (i.e. HC, CO, NO )
were marked either 5 or 6 (i.e. acceptable) as the configurated engine was
estimated to meet the target at low mileage. In addition, the weighting of
each of the exhaust emission components was 3-99, 3-61, 3-92 respectively.
However, the durability of the emission control equipment and the engine was
only given a total weighting of *».80. Since the durability of catalysts is
the critical factor in many of the configurated engines, an increase In the
weighting of this aspect would significantly Improve the position of the
CVCC engines.
2. The engines configured are at various stages of development. The complex
mechanical fuel injection equipment of the VW engine might be considerably
simplified in the future.
3. The weighting figures generally display a concern with environmental issues
such as exhaust emissions and energy utilisation, with a relatively lower
weighting on vehicle first cost. Automotive manufacturers would probably
consider vehicle first cost to be of critical importance,
k. Market penetration and amortization of production plant costs have not been
considered in the engine cost analysis. Such an approach would probably
give the conventional gasoline engine an advantage over alternatives.
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GENERAL CONCLUSIONS
This survey has revealed a basic limitation of unthrottled stratified charge
engines, in that hydrocarbon emission levels are always very high. These
levels can be reduced by throttling the engine, but they are usually still
greater than the conventional gasoline engine. There are two primary methods
for HC control. Fuel economy can be sacrificed to increase the exhaust
temperature and aid HC oxidation In the exhaust. Alternatively, reliance
can be placed on catalytic reactors, although even here there will be some
economy pena1ty.
A new method of engine combustion is needed, besides spark or compression
Ignition, which will be satisfactory In oxidising lean air fuel mixtures,
and will avoid the formation of unburnt hydrocarbons.
Carbon monoxide emissions from stratified charge engines are universally low,
although In CVS tests they are usually above the primary target of 3.^ g/mile.
NO emissions vary, depending on the stratification.
(NO emissions at an air fuel ratio of 16)
Rating of Categories
Homogeneous charge gasoline engine
Category 6
Category 1
Category 2 and 3
Category 5
Category k
Example
IFF
PROCO
TCCS
CVCC
VW
Highest
Lowest
Exhaust diluent engines may give even lower levels of NO, but at the expense
of economy.,
5. The best possible fuel economy from a reciprocating I.e. engine is attained
by completely unthrottled operation and control of engine power by fuel flow
alone. None of the engines reviewed has reached the fuel economy levels which
are theoretically attainable, due to high heat transfer losses caused by
charge agitation and movement during combustion, and matching problems of air
swirl and fuel Injection over the speed and load range. Furthermore, the best
economy figures attained have been further compromised by modifications of
the engine operating parameters such as the introduction of throttling to
reduce HC emissions. The fuel economy figures reviewed In this survey have
been relatively disappointing. Only the direct injection engines have shown
any improvement over baseline conventional gasoline engines. These baseline
engines were chosen to be representative of good current engines, rather than
average examples.
6. The specific torque output (i.e. BMEP) of a naturally aspirated stratified
charge engine at the primary emission target will always be lower than
conventional gasoline engines, unless the stratified charge engine Is fitted
with an air pump and exhaust oxidation device. Without exception air pumps
are avoided on stratified charge engines, and the minimum air fuel ratio of
80
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the engines Is arranged to be leaner than stolchlometric. The maximum
specific torques recorded from the naturally aspirated engine in this survey
was around 8.5 bar. Many engines could not attain this figure, particularly
those where fuel injection was occurring In the region of 50 - 0° BTDC at
full load. Under these conditions, the maximum specific torque of the engine
Is limited by the onset of smoke. The actual smoke characteristics depend
on the combustion principle. These engines also have higher particulate
emissions than conventional gasoline engines.
7. A multi-fuel capability is usually displayed by stratified charge engines
which resemble the diesel, and where the combustion is being controlled mainly
by the rate of fuel Injection. Carburetted stratified charge engines have no
multi-fuel capability In the accepted sense.
8. The mechanical complexity and cost of a stratified charge engine is completely
governed by the combustion principle. In general these engines are more
expensive than the gasoline engine even when meeting the same emission targets.
The production costs of stratified charge engines may vary from a few percent
to twice the level of the gasoline engine.
9- Engine size and weight Is influenced by the combustion system. .The only
rotary stratified charge engine reviewed, I.e. Curtiss-Wright, had a
considerable advantage in this respect. However, the rotary stratified
charge engine, at Its present stage of development,-suffers from all the same
problems as the rotary gasoline engine, i.e. poor fuel consumption and very
high HC emissions.
10. Full load noise Is governed by the maximum rate of pressure rise, the actual
shape of the pressure diagram and the maximum cylinder pressure.
Generally the actual noise level Is governed by the category:-
FulI Load Noise Levels in Comparison to the Gasoline Engine
Category Noise
1 Higher
2 Similar
3 Similar
k Higher If pre-chamber size above 10% of clearance
volume. Otherwise similar
5 Similar if stratification maintained at full load.
If mixture enriched combustion becomes harsher.
6 Similar
7 Depends on type
11. Noise under idling and low load conditions is highest with unthrottled engines.
12. Startablltty of most of the engines reviewed was good, although some of the
engines with in-cyllnder injection alone,required the addition of fuel into the
81
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main Induction system during starting at very low temperatures.
13. When the coolant is cold, driveability of engines with in-cylinder fuel
Injection Is better than with carburetted engines.
]k. Turbocharglng Is only attractive for unthrottled engines.
15. Stratified charge versions of motorcycle engines are not economically
attractive at the motorcycle emission target, but the Honda and Kushul
processes may be practical for lower emission levels.
16. Engines from categories 1 to 5 were configured and rated by a jury under
26 topic areas. The overall result of the rating was that the Ford PROCO
and Honda CVCC engines were possible alternatives to the gasoline engine at
the primary emission target, and that these engines, together with the VW
engine, were viable power plants at the secondary target. However, in
achieving the secondary targets there will almost always be severe sacrifices
in specific power output, driveability and fuel economy. Only the Ford PROCO
system could meet the secondary target without a significant reduction in
fuel economy. The performance of the VW system at the secondary targets is
not proven.
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GENERAL RECOMMENDATIONS
1. The scavenged pre-chamber engine (e.g. Honda CVCC) should continue to
receive study as an Interim measure to achieve the primary emission target.
Although It has demonstrated the ability to meet the secondary target, it
may not prove to be a satisfactory power plant in the long term, due to poor
fuel economy and drlveabi11ty. This process may also be practical for
motorcycles with cylinder sizes above 200 cc.
2. The Ford PROCO emerged high in the rating study and although catalyst
durabi11ty,first cost and noise problems exist, It has some attractive
features. Notably the secondary emission targets have been demonstrated
with virtually no loss in fuel economy compared to existing gasoline engines.
Therefore, continuity of production could be achieved as the emission levels
were reduced.
3. As the engine with the lowest exhaust emissions and best test bed fuel
consumption of any reviewed In this survey, the MAN-FM should be applied
to an automotive vehicle, so that a direct comparison can be made with other
stratified charge engines. The multi-fuel capability of this engine may
also prove useful in other applications.
1». The Porsche and VW engines should receive further study as configurations
most likely to achieve the secondary emission targets without sacrifice In
durability or engine performance.
5. Further investigation of the Kushul engine is recommended.
6. Research groups should be encouraged to study alternative methods for
Initiating combustion, besides compression and spark ignition. The basic
premise that unthrottled engines, operating at moderate compression ratios
could give better utilisation of energy than existing i.e. engines, Is sound.
The exhaust emission limitations associated with existing stratified charge
engines is related to the method of combustion, i.e. Initiating the combustion
with a spark and relying on flame propagation to oxidise all the fuel.
7- In the event that alternative methods of Initiating and controlling combustion
are not successful, the problem of HC formation in spark Ignited stratified
charge engines should receive a fundamental study. This should include the
source of HC emissions, and possible methods of control, both in-cyllnder
and in the exhaust system. It may be that the formation mechanism in single
chamber and divided chamber engines will be different.
8. Understanding of combustion and heat transfer In stratified charge engines is
rather limited. Further experimental studies by combustion photography,
instantaneous heat transfer measurements and fuel injection droplet
characteristics would establish empirical relations, and help in the form-
ulation of complex mathematical models. Existing models are of limited use,
due to out-moded and non-applicable empirical relations.
83
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ACKNOWLEDGEMENTS
Ricardo would like to acknowledge the assistance and information given in
the preparation of this report, by the following Companies:
Ford
Texaco
Curtlss-Wright
MAN
British Leyland
84
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ttlCABDO CONSULTING ENGINEERS
PROPOSED ALTERNATIVE APPROACH FOR
COMBUSTION INITIATION IN BECIgQCATlNG
INTEBNAL COMBUSTION ENGINE
5. 6220
12-Sept '75
FIG. D.1
CATALYSED GRID
FORMING CAP FOR
PISTON BOWL
1 HOLE FUEL
INJECTOR
BISECT/NG CATALYSED GCID
-------
A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
SECTION K
GLOSSARY OF TERMS
-------
Some of the terms mentioned In the text of this report may not be familiar
to the reader, so the following glossary has been compiled.
CVS-CH 1975 cold/hot start Federal test procedure using
CVS equipment.
Dl Direct Injection
EFI Electronic fuel injection
EGR Exhaust gas reelrculation
IDI Indirect Injection (i.e. into a pre-chamber)
mbt Ignition spark at minimum advance for best torque
mpg Fuel economy In miles per U.S. gallon
NA Naturally aspirated
RON Fuel Research octane number
T/C Turbocharged
85
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-JJ60/3-74-011A
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE ANDSUBTITLE
A STUDY OF STRATIFIED CHARGE FOR LIGHT
DUTY POWER PLANTS
5. REPORT DATE
OCTOBER
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
RICARDO £ CO.
8. PERFORMING ORGANIZATION REPORT NO.
DP
9. PERFORMING ORG'\NIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
RICARDO & CO. ENGINEERS (1927) LTD.,
BRIDGE WORKS, SHOREHAM-BY-SEA,. SUSSEX, BN*» 5FG,
ENGLAND.
11. CONTRACT/GRANT NO.
68-03-0375 "
12. SPONSORING AGENCY NAME AND ADDRESS
ENVIRONMENTAL PROTECTION AGENCY, OFFICE OR AIR &
WATER PROGRAMS, OFFICE OF MOBILE SOURCE AIR
POLLUTION CONTROL, EMISSION CONTROL TECHNOLOGY
DIVISION, ANN ARBOR, MICHIGAN **8l05
13. TYPE OF REPORT AND PERIOD COVERED
FINAL REPORT
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The objectives of this project were to determine the acceptability of various
types of stratified charge engines as potential power plants for light duty
vehicles and motorcycles In America. The light duty vehicle considered was a 4/5
seat compact sedan with good acceleration capabilities and exhaust emissions below
a primary target of 0.41 g/mile HC, 3.k g/mile CO, 1.5 g/mlle NO . A secondary
target of 0.41 g/mlle HC, 3-4 g/mlle CO and 0.4 g/mlle NO was afso considered.
A literature survey was undertaken, comparing stratified charge engines with
examples of good conventional gasoline and diesel engines. While some stratified
charge engines had exhaust emission or fuel economy advantages, there were always
sacrifices In other areas.
Eleven engines were configured, four of which were specifically directed to-
wards the secondary emission targets. A method of rating the engines was derived,
and the design concepts were compared with two gasoline engines by a jury panel.
The overall result was that the Ford PROCO and Honda CVCC combustion processes
were serious contenders to the gasoline engine at the primary emission target, and
that both of these systems, together with the VW combustion process, might be
suitable at the secondary targets.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
EXHAUST EMISSIONS
STRATIFIED CHARGE ENGINES
POWER PLANT RATING METHODOLOGY
ENGINE DESIGN
LITERATURE REVIEW
LIGHT DUTY VEHICLES
LIGHT DUTY ENGINE
GASOLINE/STRATIFIED CHARd
COMPARISON
EMISSION CONTROLS
FUEL ECONOMY
13. DISTRIBUTION STATEMENT
RELEASE UNLIMITED
EPA Form 2220-1 (9-73)
86
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
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