75-23 AH
Evaluation of the Ethyl Turbulent Flow Manifold
Lean Mixture Induction System
as Applied to a BMW Two-Litre Automobile
May 1975
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Environmental Protection-Agency
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Background
For many years, Ethyl Corporation engineers have conducted research into
engine operation at lean air-fuel ratios. They were interested in lean-
mixture combustion because of the inherently low emissions and good fuel
economy that are possible with a properly controlled lean engine. Some of
their recent research efforts have been to demonstrate the potential of
lean-mixture control techniques to meet the future emissions standards of
the European Economic Community.
Part of the recent work at Ethyl has been with vehicles that use
small high-performance engines, on which significant reductions in emissJi."»s
have been achieved. The Emission Control Technology Division, consi~-t
types of vehicles that are in actual use requires a much larger saraplr
of test vehicles than is economically feasible in the evaluation test
projects conducted by EPA. For promising systems it is necessary that
more extensive test programs be carried out.
The conclusions from this EPA evaluation test can be considered
to be quantitatively valid only for the specific test car used.
However, it is reasonable to extrapolate the results from the EPA. .
test to other types of vehicles in a directional or qualitative manner,
i.e.-, to suggest that similar results are likely to be achieved on
other types of vehicles.
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Vehicle Description
The vehicle tested was a BMW 2002 with a four cylinder, 121.3 cubic
inch (1988 cc), overhead cam engine and a 3-speed automatic transmission.
The standard induction system was replaced by an Ethyl Turbulent Flow
Manifold (TFM). (The car is described in detail on the following page.)
The Ethyl TFM is a lean combustion system. The carburetor and intake
manifold incorporate a number of modifications to improve the homogeneity
of the fuel-air mixture without fuel economy or performance penalties.
The manifold (Figure 1) is a BMW 2002 intake manifold modified to
improve the quality of the fuel-air mixture. The original Solex car-
buretor was replaced by a Holley carburetor (Model 5200) that was re
calibrated to deliver the proper lean fuel-air mixture. The primary
section was modified to improve fuel atomization at low air flow rater
The essential features of the TFM are the long mixing tube below
the primary yenturi, the change of flow direction in the mixing box,
and the secondary venturi bypass. The long mixing tube allows the
fuel-air mixture downstream of the throttle to become more un.1 for;p,
Changing the flow direction increases turbulence which Improves «>ie
mixture quality and causes large fuel droplets to fall onto the mixiug
box floor, where they are vaporized before reentering the stream.
The secondary flow bypasses the mixing box in order to minimize pumping
losses, thus minimizing losses in volumetric efficiency.
On this vehicle, Ethyl's efforts were directed toward reducing
the vehicle's HC and CO emissions without a fuel economy or performance
penalty. NOx levels were to be maintained near the levels of the
original vehicle.
The techniques used by Ethyl have resulted in reduced poillnt it
emissions (except NOx) without exhaust gas recirculation (EGK) or air in-
jection. (The stock 1973 BMW 2002 is equipped with EGR; the 1975
models have EGR, air injection and a rich" thermal reactor)
Test Procedures
Exhaust emission tests were conducted according to the 1975 Feder?'1
Test Procedure ('75 FTP), described in the Federal Register of
November 15, 1972, except that no evaporative emissions tests were
conducted. In addition the vehicle was tested for emissions and fuel
economy using the EPA Highway Cycle. Since the current model of this
vehicle has increased in weight, the testing was conducted at both
weights.
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1973 BMW 2002
Emission control system - Ethyl Lean Mixture System
Engine
type A stroke Otto cycle, SOHC, A cyl. in-line
bore x stroke 3.50 x 3.15 in./88.9 x 80 mm
displacement 121.3 CID/1988 cc
compression ratio . '. 8.5:1
maximum power @ rpm . 103 b'hp (SAE)/76.8 kW @ 5200 RPM*
fuel metering single_ 2 barrel..carburetor
fuel requirement x~. . . . regular leaded (per Ethyl Corp.)
tested with 100 RON leaded ludoltiic 30
Drive Train
transmission type 3 speed automatic
final drive ratio . 3.64:1
Chassis ' .
unitized body/frame, front engine,
type rear wheel drive
tire size 165 HR 13
curb weight 2285 lbs./1036 kg
inertia weight . . 2500/2750.pounds
passenger capacity ........ 4
Emission Control System
;
basic type lean combustion (mixture) system -
(Turbulent Flow Manifold)
distributor standard BMW unit, mechanical
advance only
*durability accumulated on system . 3000 miles
31,000 miles on vehicle ami • ugi •
* Information supplied by Ethyl Corporation.
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Primary
Venturi
Adapter
Plate
Primary
Mixing
Tube
Secondary Venturi
'
Mixing Box F>cit
Conditioning
Chamber
Coolant Jacket
Conditioning Chamber
Cover
Coolant Jacket Cover
Figure 1. Turbulent Flow
Intake Manifold for BMW
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Ethyl's development and testing on this vehicle was conducted
using a test inertia weight (IW) of 2500 pounds (1134 kg). However,
the 1975 BMW 2002 with automatic transmission was certified at 2750
pounds (1247 kg). Therefore, to allow comparison of the EPA test results
with Ethyl's data and with certification results, the vehicle was tested
at both weights. To permit comparison with Ethyl's results, tests were
conducted using an IW of 2500 pounds with a road load setting of 9.4
horsepower (7.0 kW) at 50 miles per hour (80.5 km/hr). And, to permit
comparison with certification results, tests were conducted using an
IW of 2750 pounds with a road load setting of 9.9 horsepower (7.4 kW)
at 50 miles per hour. For comparison with certification data on the
baseline (stock 1973) car, mass emissions have also been calculated by
the 1972 FTP from the two tests at 2500 Ibs.
Two '75 FTP's and two EPA Highway Cycles were run at each inertia
weight. No calibration changes were made to the vehicle to adjust
for these different vehicle test weights.
For this vehicle, Ethyl specified a regular leaded gasoline, basing
this requirement on their own chassis dynamometer octane rating n£ 9,?
Research Octane Number (RON). The fuel used for the tests reported
herein was Indolene 30, a standard leaded (3.0 gm/gal) test fuel of
100 RON.
Test Results
Exhaust emissions data, summarized below, showed that the Ethyl
test car, using the TFM, achieved the levels of the 1975 Federal
emissions standards at low mileage, but did not meet the stricter
California standards. Detailed test results appear in the appendix to
this report.
'75 FTP Composite Mass Emissions
grams per mile
(grams per kilometre)
Fuel Economy
HC CO NOx (Fuel Consumption)
Ethyl BMW 2002 1.08 6.20 2.85 25.1 miles/gal
2500 pounds (.67) (3.85) (1.77) (9.4 litres/100 km)
Average of 2 tests
Ethyl BMW 2002 1.20 8.57 2.79 24.6 miles/gal
2750 pounds (.75) (5.32) (1.73) (9.6 litres/100 km)
Average of 2 tests
Certification Values .26 6.60 1.11 20.4 miles/gal
1975 BMW 2002 (.16) (4.10) (.69) (11.6 litres/100 km)
2750 Ibs. Automatic
Transmission
1975 Federal Standards 1.5 15.0 3.1
1975 California
Standards 0.9 9.0 2.0
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On the EPA Highway Cycle the results were:
EPA Highway Cycle Mass Emissions
grams per mile
(grams per kilometre)
,HC
CO
NOx
Ethyl BMW 2002
2500 pounds
Average of 2 tests
Ethyl BMW 2002
2750 pounds
Average of 2 tests
Certification Values
1975 BMW 2002
2750 Ibs., Automatic
Transmission
.33 3.33 2.07
(.21) (2.07) (1.28)
.41 3.47 2.32
(.25) (2.15) (1.44)
.02 .95 1.16
(.01) (.59) (.72)
Fuel Economy
(Fuel Consumption)
30.8 miles/gal
(7.6 litres/100 km)
30.9 miles/gal
(7.6 litres/100 km)
28.9 miles/gal
(8.1 litres/100 km)
A comparison of fuel economy values shows that the Ethyl BMW (at
2750 Ibs.) delivered better fuel economy than the '75 BMW tested for
certification. The Ethyl car's fuel economy was 21% better on the
'75 FTP and 7% better on the Highway Cycle. Not only was the Ethyl
BMW better in fuel economy that the '75 BMW, it was better than all
other'75 models in the 2750 pound 1W class.
To compare the Ethyl car with a "baseline" car, '72 FTP mass
emissions were calculated using the data from the two 75 FTP's that
were run at 2500 Ibs. inertia weight. The "baseline" car was
considered to be the car tested for 1973 model year certification.
(The 1972 FTP was used for certification in model years 1972 through
1974). Results are summarized below.
Ethyl BMW 2002
2500-pounds
average of 2 tests
Certification Values
1973 BMW 2002
2500 Ibs., Automatic
Transmission
1972 FTP Mass Emissions
grams per mile
(grams per kilometre)
HC
CO
1.29 9.37
(.80) (5.82)
2.1 27
(1.3) (17)
NOx
2.90
(1.80)
1.5
(.9)
Fuel Economy
(Fuel Consumption)
24.0 miles/gal
(9.8 litres/100 km)
21.8 miles/gal
(10.8 litres/100 km)
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Emissions of HC and CO from the Ethyl car were considerably lower
than those from the '73 certification BMW, but NOx emissions were 93%
higher. Fuel economy of the Ethyl car was 10% better.
Certain driveability problems were noted on the Ethyl BMW. When
the vehicle was driven on the road as part of the test preparation and
to check driveability, moderate surge was evident. However during a
similar check at the conclusion of testing, only slight surge was noted.
During three of the four cold start 75 FTP's the vehicle stalled.
Investigating the surge problem after this EPA test program, Ethyl
engineers found that the surge was due to liquid fuel which collected
in vacuum supply passages in the special carburetor adapter plate, and
then was pulled into the air stream at sporadic intervals, causing a
surge in engine power. A simple modification to the adapter plate
provides ventilation to those passages, preventing a buildup of fuel.
Subsequent driveability evaluations by EPA engineers confirmed that the
earlier surge problem was solved.
Conclusions
The Ethyl BMW equipped with the Turbulent Flow Manifold met the
emissions levels required by the 1975 Federal Standards with a minimum
of emission control devices. The fuel economy of the Ethyl BMW was
improved over not only the current (1975 model) BMW 2002 and the base--
line (1973 model) vehicle, but also all other 1975 models in the 2750
pound IW class.
The Ethyl BMW has shown that a car without a catalyst can meet
the 1975 Federal standards and deliver excellent fuel economy. It is
the technical judgment of EPA personnel that the car has demonstrated
low enough emissions from the engine to permit it to meet emission
levels of 0.41 HC, 3.4 CO, and 2.0 NOx with the addition of a cataJvst
or other exhaust aftertreatment device to the system. Although the
spark timing schedule of the engine is advanced compared to the stock
schedule, EPA personnel feel that the car can probably be operated
with customer acceptability on 91 RON fuel, leaded or unleaded (BMW
specifies either fuel for the car), since neither the compression
ratio (8.5:1) nor the combustion chamber was changed. We feel that
the use of an oxidizing catalytic converter or a lean thermal reactor
in conjunction with the TFM would be a fruitful area of investigation,
since such combinations appear to have potential for further reductions
in HC and CO emissions and possibly fuel economy gains as well. Pro-
portional EGR could be used to reduce NOx formation without affecting
fuel economy.
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Ethyl Corporation personnel are continuing development of the
TFM system; it is presently installed on intermediate and full size
cars in addition to the BMW. The EPA plans to test those cars in the
near future.
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BAG 1 COLD TRANSIENT
Table A-l
'75 FTP Mass Emissions
grams per mile
BAG 2 HOT STABILIZED
BAG 3 HOT TRANSIENT
TEST NUMBER
. 19-8245
16-8298
19-8278
16-8325
INERTIA
WEIGHT HC
2500
2500
2750
2750
1.68
1.55
1.88
1.92
CO
17.41
13.71
21.25
23.03
co2
361
372
371
367
NOx
3.35
3.66
3.45
3.22
FUEL
ECONOMY
MPG
22.5
22.3
21.6
21.7
HC
1.00
.96
1.04
1.02
CO
3.90
3.47
4.11
5.24
co2
331
347
346
342
NOx
2.26
2.42
2.35
2.32
FUEL
ECONOMY
MPG
26.1
25.0
24.9
25.1
HC
.85
.86
.95
1.02
CO
3.97
3.90
5.10
6.43
co2
313
329
328
320
FUEL
ECONOMY
NOx MPG
3.09
3.53
3.30
3.18
27.6
26.3
26.2
26.6
TEST NUMBER
19-8245
16-8298 •
19-8278
16-8325
Table Ib
'75 FTP Composite Mass Emissions
grams per mile
INERTIA WEIGHT
2500
2500
2750
2750
HC
CO
CO,,
1.10 6.70 332
.1.06 5.70
1.19 7.91
Io21 9.22
NOx
FUEL ECONOMY
MPG
f.
332
347
346
341
2.71
2.98
2.84
2.74
25.6
24.7
24.5
24.7
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Table A-2
EPA Highway Cycle Mass Emissions
grams per mile
FUEL ECONOMY
TEST NUMBER
19-8245
16-8298
. 19-8278
16-8325
INERTIA WEIGHT
2500
2500
2750
2750
HC
.33
.33
.39
.43
CO
3.09
3.56
3.50
3.43
co2
273
290
286
275
NOx
1.95
2.18
2.13
2.50
MPG
31.8
29.9
30.3
31.5
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