75-7 AW
Evaluation of the Dresserator
Emission Control System
August 1974
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Mr Pollution Control
Environmental Protection Agency
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Background
The Environmental Protection Agency receives information about many
devices for which emission reduction or fuel economy improvement claims
are made. In some cases, both claims are made for a single device. In
most cases, these devices are being recommended or promoted for retrofit
to existing vehicles although some represent advanced systems for meeting
future standards.
The EPA is interested in evaluating the validity of the claims for
all such devices, because of the obvious benefits to the Nation of identifying
devices that live up to their claims. For that reason the EPA invites
proponents of such devices to provide to the EPA complete technical data
on the device's principle of operation, together with test data on the
device made by independent laboratories. In those cases in which review
by' EPA technical staff suggests that the data submitted holds promise
of confirming the claims made for the device, confirmatory tests of the
device are scheduled at the EPA Emissions Laboratory at Ann Arbor, Michigan.
The results of all such confirmatory test projects are set forth in a
series 'of Technology Assessment and Evaluation Reports, of which this report
is one.
The conclusions drawn from the EPA confirmatory tests are necessarily
of limited applicability. A complete evaluation of the effectiveness of
an emission control system in achieving its claimed performance improvements
on the many different types of vehicles that are in actual use requires a
much larger sample of test vehicles than is economically feasible in the
confirmatory test projects conducted by EPA. I/ For promising devices
it is necessary that more extensive test programs be carried out.
The conclusions from the EPA confirmatory tests can be considered
to be quantitatively valid only for the specific type of vehicle used in
the EPA confirmatory test program. Although it is reasonable to^extrapolate
the results from the EPA confirmatory test to other types of vehicles in
a directional or qualitative manner, i.e., to suggest that similar results
are likely to be achieved on other types of vehicles, tests of the device
on such other vehicles would be required to reliably quantify results on
other types of vehicles.
In summary, a device that lives up to its claims in the EPA confirmatory
test must be further tested according to protocols described in footnote I/,
to quantify its beneficial effects on a broad range of vehicles. A device
which when tested by EPA does not meet the claimed results would not appear
to be a worthwhile candidate for such further testing from the standpoint
of the likelihood of ultimately validating the claims made. However, a
definitive quantitative evaluation of its effectiveness on a broad range
of vehicle types would equally require further tests in accordance with
footnote I/.
I/ See Federal Register 38 FR 11334, 3/27/74, for a description of the
test protocols proposed for definitive evaluations of the effectiveness
of retrofit devices.
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The subject of this particular report is the Dresserator induction
system designed by Dresser Industries of Dallas, Texas. The Dresserator
is essentially a variable venturi, critical flow induction system with fuel
metering that allows operation of the engine at an air/fuel ratio of 18 to
18.5:1. This lean combustion offers the combination of low NOx emissions
(below 2 gpm) and increased economy. In addition, residual oxygen which
exists in the exhaust can be used to oxidize residual HC and CO. All
EPA tests were run on unleaded fuel, although either leaded or unleaded
fuel may be used with the Dresserator system.
Device and Vehicle Description
The Dresserator induction system includes a variable critical flow
venturi with fuel metering. At the point of minimum throat area, the
flow is designed to have sonic velocity, i.e., is "choked". Slightly
downstream of the throat, a region of supersonic flow exists. A shock
wave occurs at the point where the flow becomes subsonic. These phenomena
are said to cause better mixing and atomization of the fuel, which is
metered into the air stream above the throat area and is drawn through the
shock wave. The variable venturi design allows close control of the mass
flow of air by maintaining the throat area such that the flow is choked
over a wide range of engine operating speeds.
Two vehicles were delivered to the EPA for testing: a 1973 Chevrolet
Monte Carlo equipped with a 350 CID engine and an automatic transmission,
and a 1973 Ford Capri with a 159 CID engine and an automatic transmission.
The modified Monte Carlo had an Edelbrock single plane manifold,
a 1970 distributor with idle retard, no vacuum advance, no EGR and no
air pump. Other items are standard equipment.
The center divider of the Capri manifold was removed in the plenum
area only. The stock cam was exchanged for one with slightly less overlap,
reducing internal EGR. It presently has no EGR or vacuum advance. En-
larged and lagged (insulated) exhaust manifolds were installed. Other
items are standard equipment.
Both cars were equipped with the Model 2 Dresserator, which uses
a low pressure fuel-feed system, and a cold start compensation system
with varying fuel pressure which acts for 120 to 190 seconds after a
cold start. The Dresserator inductors use neither a conventional
choke nor accelerator pump.
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Test Program
Emission tests were performed as directed in the 1972 Federal Test
Procedure (FTP) and the 1975 FTP (Federal Register, Vol. 37, No. 221,
Part II, November 15, 1972). In addition, the Federal Highway Driving
Cycle was run on each vehicle to determine highway fuel economy.
Two 1975 FTP's and one Highway Cycle were run on the Monte Carlo.
Two 1975 FTP's and two Highway Cycles were run on the Capri with the
ignition timing set at 8° BTDC. The timing on the Capri was then advanced 3°
(to 11° BTDC) and a hot start 1972 FTP and Highway Cycle were run.
Advancing the ignition timing on the Capri was expected to increase
fuel economy and raise the hydrocarbon emissions slightly.
Test Results
Both vehicles achieved 1975 interim emissions levels (see Tables I
and II). The Capri in fact was well within the California interim levels
of .9 gpm HC, 9.0 gpm CO and 2.0 gpm N0x« With the timing set at +8°
(before TDC), the Capri produced less than half the allowable (Federal)
HC, CO and NOx- Advancing the timing 3° resulted in a 10% increase in
both LA4 and highway fuel economy, while HC emissions increased by 50%.
However, HC emissions were still less than 1.0 gpm. The Monte Carlo
ran at less than two-thirds the permissible levels for HC, CO and N0x«
NOx emissions from both vehicles were below the 1977 level of
2.0 gpm. Neither vehicle met the 1977 HC and CO levels of 0.41 and 3.4
gpm, respectively.
The values for the "Hot '72 FTP" in Table I, to study the effects
of advancing the timing, were calculated from the second and third
parts of the '75 FTP.
Fuel economy for both vehicles was good. The '72 FTP fuel economy/
fuel consumption values listed in Tables I and II (calculated using the data
from the first and second parts of the '75 FTP) are seen to be better than
the values from the certification tests of the comparable 1973 models.
No significant driveability problems were encountered.
Conclusions
The Dresserator induction system has been shown to be capable of
achieving the 1975 interim emission standards on two vehicles, one
representing the compact car class, and the other the intermediate class.
It is particularly significant that this was done without the use of con-
ventional emission controls such as oxidation catalysts, and without
penalizing fuel economy (compared to the baseline vehicles).
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At this time, there has been no attempt to establish durability
of the Dresserator. However, durability should not be a problem since
the Dresserator does not cause any high temperatures in the fuel-air
induction system.
If no difficulties arise in attempting to mass produce the unit,
it may prove to be a successful method of controlling emissions from
internal combustion engines to the statutory levels.
It is our technical judgment that the use of oxidizing catalytic
converters in conjunction with the Dresserator should be investigated,
since such a combination appears to have potential for further optimiza-
tion of fuel economy and emissions. This judgment is based on the fact
that the Dresserator-equipped cars achieved relatively good fuel economy
even with spark retard for HC control. Another attractive area of
investigation, in our opinion, is the combination of the Dresserator
with a lean thermal reactor. Since the exhaust from a Dresserator-
equipped car, when operated at A/F ratios of 18 to 19:1, contains 4 to
5% oxygen homogeneously mixed at the exhaust temperature, it is ideally
suited to further cleanup in catalytic or thermal reactors without
requiring air pumps.
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TABLE I
1973 Capri
159 CIO
Test
'75 FTP
'75 FTP
+8°
Mass emissions in
grams per mile
(grama per kilometre)
Urban
Fuel Economy, miles/gal.
HC CO CO? NO, (Fuel Consuaption. litres/100 tan)
19.2 mpg
(12.3 litres/100 km)
17.5 mpg
(13.4 litres/100 km)
0.57 5.29 471 1.16
(0.35) (3.29) (293) (0.72)
0.60 5.72 500 1.35
(0.37) (3.55) (311) (0.84)
Average 0.59 5.50 486 1.25
(0.36) (3.42) (302) (0.78)
18.4 opg
(12.9 litres/100 km)
Highway
Fuel Economy, miles/gal.
(Fuel Consumption.litres/100 km),
24.2 mpg
(9.7 litres/100 km)
24.4 mpg
(9.6 litres/100 km)
24.3 mpg
(9.7 litres/100 km)
'75 Interim
Standards
1.5 15.0
(0.93) (9.32)
3.1
(1.93)
'72 FTP +8° 0.77 8.13 481 1.39
(0.48) (5.05) (299) (0.86)
•72 FTP +8" 0.87 8.79 514 1.62
(0.54) (5.46) (319) (1.01)
17.9 mpg
(13.1 litres/100 km)
16.7 mpg
(14.1 litres/100 km)
Average 0.82 8.46 498 1.51 17.3 mpg
(0.51) (5.26) (309) (0.94) (13.6 litres/100 km)
Hot '72 FTP +8°
Hot '72 FTP +8°
Average
0.40 3.40 486 1.15
(0.25) (2.11) (302) (0.71)
0.41 3.28 452 0.89
(0.25) (2.04) (281) (0.62)
0.41 3.34 469 1.07
(0.25) (2.08) (293) (0.67)
18.0 mpg
(13.1 litres/100 km)
19.4 mpg
(12.1 litres/100 km)
18.7 mpg
(12.6 litres/100 km)
Hot '72 FTP +11° 0.62 3.43 426 1.27 20.6 mpg
(0.39) (2.13) (265) (0.79) (11.4 litres/100 km)
27.0 mpg
(8.T litres/100 km)
Note: '72 FTP values calculated from Bags 1 and 2 of '75 FTP; Hot '72 FTP values calculated
from Bags 2 and 3 of '75 FTP.
'72 FTP
1973 Certification Values
(1973 Capri, 159 CID, Automatic)
2.7 38 2.8 15.4 mpg
(1.68) (23.6) (1.74) (15.3 litres/100 km)
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TABLE II
1973 Monte Carlo
350 CID
Mass Emissions In
grams per mile
(grams per kilometre)
Urban
Test HC
'75 FTP 1.12
(0.70)
'75 FTP 1.13
{0.70)
Average 1 . 13
(0.70)
'75 Inter in 1.5
Standards (0.93)
'72 FTP 1.26
(0.78)
'72 FTP 1.18
(0.73)
Average 1 . 22
(0.76)
!72 FTP 2.7
(1.68)
CO
5.35
(3.33)
4.88
(3.03)
5.11
(3.18)
15.0
(9.32)
6.07
(3.77)
5.52
(3.43)
5.80
(3.60)
20.0
(12.4)
C02
720
(447)
660
(410)
690
(429)
738
(459)
674
(419)
706
(439)
(1973
NO*
1.77
(1.10)
1.34
(0.83)
1.55
(0.97)
3.1
(1.93)
2.05
(1.27)
1.47 '
(0.91)
1.76
(1.09)
1973
Chevrolet
2.4
(1.49)
Fuel Economy, miles/gal.
(Fuel Consumption, litres/100 km)
12.4 mpg
(19.0 litres/100 km)
13-. 4 mpg
(17.6 litres/100 km)
12.9 mpg
(18.3 litres/100 km)
11.8 mpg
(19.9 litres/100 km)
12.9 mpg
(18.2 litres/100 km)
12.4 mpg
(19.1 litres/100 km)
r
Certification Values
Monte Carlo, 350-2V, Automatic)
12.0 mpg
(19.6 litres/100 km)
Highway
Fuel Economy, miles/gal.
(Fuel Consumption, litres/IPO km)
20.3 mpg
(12.6 litres/100 km)
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