76-24 ALW
An Evaluation of the Landrum Mini-Garbs Air-Bleed
June 1976
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Environmental Protection Agency
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Background
The Environmental Protection Agency receives information about many
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. \l 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 extra-
polate the results from the EPA confirmatory test to other types of
vehicles in a directional 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
_!/, 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 \J .
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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Data submitted to the EPA indicated that an air-bleed device known
as the Landrum Mini-Garb could cause a reduction in exhaust emissions
and improve fuel economy. Consequently, an EPA confirmatory test
program was set up to investigate the effects of the Landrum Mini-Garbs
on exhaust emissions and fuel economy.
Test Vehicle and Device Description
The vehicle used for the test program was a 1970 Chevrolet Bel-Air
powered by a 350 cu in. V-8 and equipped with an automatic transmission.
A listing of vehir.le statistics is given on the Vehicle Description
sheet at the end of this report.
The conventional approach (for carburetor equipped vehicles) to
controlling idle air-fuel ratio is to regulate fuel delivery by means of
a needle valve (usually referred to as the idle mixture adjustment
screw). The Landrum Mini-Garb is an air-bleed device that replaces the
idle mixture adjustment screw in the carburetor.
The Mini-Garb is a screw with an air passageway drilled longitudinally
through the entire length of the screw. The diameter of the air passage-
way is sized to regulate the amount of air bled through the Mini-Garb.
When the Mini-Garb is installed in the carburetor, the needle valve
orifice is encompassed by one end of the Mini-Garb. Therefore, any
flow through the needle valve orifice must pass through the Mini-Garb.
Four small diameter holes are drilled through the wall of the Mini-Garb
near the end that encompasses the needle valve orifice. Fuel that
formerly passed tnrough the idle mixture adjustment needle valve enters
the Mini-Garb through the four drilled holes. The fuel, together with
air entering the exposed end of the Mini-Garb, then passes through the
needle valve orifice.
The test vehicle used for this program is equipped with a two-
barrel carburetor. A Mini-Garb was installed in place of the idle
mixture screw for eacV carburetor venturi. Supplied with the Mini-Garbs
was a short length of flexible tubing that was connected between the
protruding ends of the Mini-Garbs. An opening covered with a wire mesh
for filtering the air passing into the Mini-Garbs is located in the
middle of the tube.
Test Program
Exhaust emission tests were conducted in accordance with the 1975
Federal Test Procedure ('75 FTP). Exhaust emissions and fuel economy
were also measured during the EPA Highway Fuel Economy Test (HFET) and
at several steady state speeds.
Initially, the test vehicle was adjusted according to the manufacturer's
tune-up specifications. Baseline tests were then conducted, and included
duplicate tests according to the '75 FTP and HFET, and one set of steady
states.
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After completion of the baseline tests, the Mini-Garbs were installed
as directed in the accompanying instructions. Testing again included
the '75 FTP and HFET, and one set of steady states.
Test Results
The effects of the Mini-Garbs on exhaust emissions and fuel economy
are illustrated in the following tables:
1975 Federal Test Procedure
mass emissions in
grams per mile
(grams per kilometer)
Baseline - Avg.
of 2 tests
Mini-Garbs avg.
of 2 tests
HC
CO
NOx
2.14
(1.33)
1.98
(1.23)
37.5
(23.3)
25.4
(15.8)
3.99
(2.48)
4.07
(2.53)
Fuel Economy
(Fuel Consumption)
12.4 miles/gal
(19.0 liters/100 km)
12.7 miles/gal
(18.6 liters/100 km)
% change
from baseline
-7%
-32%
+2%
+2%
(-2%)
Baseline - avg.
of 2 tests
Mini-Garbs - avg.
of 2 tests
% change
from baseline
Highway Fuel Economy Test
mass emissions in
grams per mile
(grams per kilometer)
HC
1.32
(0.82)
1.31
(0.81)
-1%
CO
22.3
(13.9)
14.5
(9.0)
-35%
NOx
4.99
(3.10)
5.23
(3.25)
+5%
Fuel Economy
(Fuel Consumption)
13.7 miles/gal
(12.7 liters/100 km)
13.8 miles/gal
(12.5 liters/100 km)
+1%
(-2%)
The effects of the Mini-Garbs on exhaust emissions are due to mixture
enleanment caused by air bled into the idle circuit through the Mini-Carbs.
This is evidenced by the decrease in HC and CO emissions, and che increase
in NOx emissions.
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The change in fuel economy accompanying installation of the Mini-Garbs
is less than normal test variability and is not significant.
The wire mesh intended to filter air passing into the Min:-Garbs is
too coarse to be effective. The size of the mesh openings is ;ibout the
same as that of common window screen. Sand and dust can easily pass
through the filter and into the idle circuit of the carburetor.
Details of all exhaust emissions and fuel economy tests are presented
in Tables I-IV.
Conclusions
1. The Mini-Garbs appreciably reduced carbon monoxide emissions
from the test vehicle. A small decrease in unburned hydrocarbon emissions
and a small increase in oxide of nitrogen emissions also occurred.
2. The effect of the Mini-Garbs on fuel economy was not significant.
3. Ingestion of poorly filtered air through the Mini-Garbs may
have an adverse effect on the engine and carburetor durability.
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Table I
1975 Federal Test Procedure
mass emissions in
grams per mile
(grams per kilometer)
miles/gal.
Test #
Baseline
77-2310
77-2307
Average
Landrum Mini-Garbs
77-2251
77-2291
Average
HC
2.12
(1.32)
2.15
(1.34)
2.14
(1.33)
installed
2.22
(1.38)
1.73
(1.08)
1.98
(1.23)
CO
36.9
(22.9)
38.1
(23.7)
37.5
(23.3)
24.8
(15.4)
26.0
(16.2)
25.4
(15.8)
co2
653.
(406.)
648.
(403.)
651.
(405.)
660.
(410.)
647.
(402.)
654.
(406.)
NOx 1
4.12
(2.56)
3.86
(2.40)
3.99
(2.48)
4.13
(2.56)
4.00
(2.49)
4.07
(2.53)
[liters/10
12.4
(19.0)
12.4
(19.0)
12.4
(19.0)
12.6
(18.7)
12.8
(18.4)
12.7
(18.6)
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Test #
Baseline
77-2310
77-2307
Bag 1:
HC CO
Table II
175 FTP individual bag emissions in
grams per mile
Cold Transient Bag 2: Stabilized
CO, NOx mpg HC CO C0? NOx mpg
Bag 3: Hot Transient
HC CO CO. NOx mpg
3.07 81.1 646. 4.76 11.3 1.88 25.6 687. 3.26 12.1 1.87 25.3 592. 5.28 13.9
3.13 82.0 630. 4.38 11.5 1.93 26.7 685. 3.02 12.1 1.85 26.8 593. 5.08 13.8
Landrum Mini-Garbs installed
77-2251 2.96 64.5 665. 4.82 11.4 1.94 13.6 691. 3.21 12.4 2.18 16.2 600. 5.37 14.0
77-2291 2.97 63.8 652. 4.53 11.6 0.99 16.5 673. 3.12 12.6 2.22 15.6 591. 5.29 14.2
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Table III
Highway Fuel Economy Test
mass emissions in
grams per mile
(grams per kilometer)
miles/gal.
Test #
Baseline
77-2311
77-2308
Average
Landrum Mini-Garbs
77-2252
77-2292
Average
HC
1.28
(0.80)
1.35
(0.84)
1.32
(0.82)
installed
1.34
(0.83)
1.27
(0.79)
1.31
(0.81)
CO
20.1
(12.5)
24.5
(15.2)
22.3
(13.9)
15.7
(9.8)
13.2
(8.2)
14.5
(9.0)
co2
439.
(273.)
435.
(271.)
437.
(272.)
447.
(278.)
441.
(274.)
444.
(276.)
NOx
5.17
(3.21)
4.80
(2.98)
4.99
(3.10)
5.25
(3.26)
5.20
(3.23)
5.23
(3.25)
(liters/10
18.7
(12.6)
18.6
(12.7)
18.7
(12.7)
18.6
(12.6)
19.0
(12.3)
18.8
(12.5)
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Baseline
Idle (300 sees.)
15 mph (24 kph)
30 mph (48 kph)
45 mph (72 kph)
60 mph (97 kph)
Table IV
Steady State
mass emissions in
grams per mile
(grams per kilometer)
HC
CO
CO,
NOx
miles/gal.
(liters/100 km)
1.35 gms 2.4 gms 564 gins 0.60 gms
0.99
(0.61)
1.03
(0.64)
1.08
(0.67)
0.96
(0.60)
13.9
(8.6)
8.8
(5.5)
21.8
(13.6)
19.0
(11.8)
649.
(403.)
372.
(231.)
385.
(239.)
447.
(278.)
0.70
(0.44)
1.93
(1.20)
3.26
(2.03)
5.16
(3.21)
13.2
(17.9)
22.8
(10.3)
21.0
(11.2)
18.5
(12.7)
Landrum Mini-Carbs installed
Idle (300 sees.)
15 mph (24 kph)
30 mph (48 kph)
45 mph (72 kph)
60 mph (97 kph)
1.30 gms 2.0 gms 553. gms 0.42 gms
0.71
(0.44)
0.93
(0.58)
1.02
(0.64)
0.85
(0.53)
3.5
(2.2)
2.2
(1.4)
18.5
(11.5)
12.3
(7.6)
663.
(412.)
372.
(231.)
387.
(241.)
462.
(287.)
0.69
(0.43)
1.84
(1.14)
3.37
(2.10)
4.61
(2.87)
13.2
(17.8)
23.5
(10.0)
21.1
(11.1)
18.3
(12.8)
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1970 Chevrolet Bel-Air
Emission control system - Engine Modifications
Engine
type "..-.. 4 stroke, Otto cycle, V-8, ohv
bore x stroke 4.00 x 3.48 in./101.6 x 88.4 mm
displacement .......... 350 cu in./5737 cc
compression ratio . 9.0:1
maximum power at rpm 250 bhp/187 kW @ 4800 rpm
fuel metering 2 barrel carburetor
fuel requirement regular leaded
Drive Train
transmission type 3 speed automatic
final drive ratio 2.75:1
Chassis
type front engine, rear wheel drive
tire size . , GR 70x15
curb weight 4210 lbs./1910 kg
inertia weight 4500 Ib.
passenger capacity 6
Emission Control System
basic type engine modifications
durability accumulated on system 22000 mi./35400 km
* US. GOVERNMENT PRINTING OFFICE: 1979- 651-112/0118
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