77-21 CH
Evaluation of Eccono-Jets
Air Bleed Idle Screws
March 1978
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
systems which appear to offer potential for emission reduction or fuel
economy improvement compared to conventional engines and vehicles.
EPA's Emission Control Technology Division is interested in evaluating
all such systems, because of the obvious benefits to the Nation from the
identification of systems that can reduce emissions, improve fuel economy,
or both. EPA invites developers of such systems to provide complete
technical data on the system's principle of operation, together with
available test data on the system. In those cases for which review by
EPA technical staff suggests that the data available shows promise,
attempts are made to schedule confirmatory tests at the EPA Motor Vehi-
cle Emission Laboratory at Ann Arbor, Michigan. The results of all such
test projects are set forth in a series of Technology Assessment and
Evaluation Reports, of which this report is one.
Eccono-Jets are replacement idle mixture screws that are marketed by
Eccono Corporation of Detroit, Michigan. Tests of Eccono-Jets conducted
at Olson Labs showed that use of Eccono-Jets resulted in significant
reduction of HC and CO emissions. On the basis of this data, EPA decided
to conduct confirmatory tests.
The conclusions drawn from the EPA evaluation tests are necessarily of
limited applicability. A complete evaluation of the effectiveness of an
emission control system in achieving performance improvements on the
many different types of vehicles that are in actual use requires a much
larger sample of test vehicles than is economically feasible in the
evaluation test projects conducted by EPA. For promising systems it is
necessary that more extensive test programs be carried out.
The conclusions from the EPA evaluation test can be considered to be
quantitatively valid only for the specific test car used; however, it is
reasonable to extrapolate the results from the EPA test to other types
of vehicles in a directional manner, i.e., to suggest that similar
results are likely to be achieved on other types of vehicles.
Device Description
Eccono-Jets are idle mixture screws designed as aftermarket replacements
for the standard idle mixture screws supplied with carbureted gasoline
engines. Eccono-Jets differ from standard mixture screws in that Eccono-
Jets have a hole bored through the length of the screw allowing air from
the engine compartment to bleed directly into the carburetor throat
through the idle fuel port (see Figure 1). The driving force for this
air flow is the differential between ambient atmospheric pressure (in
the engine compartment) and manifold vacuum (in the carburetor throat).
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The following benefits are claimed by the manufacturer:
-Increased fuel economy for all operating conditions
-Decreased exhaust emissions
-Decreased starting time, particularly in cold weather
-Improved performance and driveability
-Decreased carbon buildup inside engine
Installation of Eccono-Jets was performed according to the instructions
that came with them. This meant setting the screws at 1/2 turn out
from a fully bottomed position. Since this resulted in an increased
idle speed, the idle speed was then adjusted to the specifications of
the vehicle manufacturer.
Test Procedure
Exhaust emission tests were conducted according to the 1977 Federal Test
Procedure (FTP), described in the Federal Register of June 28, 1977, and
the EPA Highway Fuel Economy Test (HFET), described in the Federal
Register of September 10, 1976. Steady state and Federal Short Cycle
tests were also conducted. Evaporative emissions were not tested.
Prior to baseline testing, the vehicle, described in Table 1, was tuned
to Chevrolet's specifications for ignition timing, idle speed and spark
plug gap. One spark plug lead was found to be defective and was re-
placed. Compression in all cylinders was also checked and found to be
within specification.
The vehicle was tested in three different conditions:
1) Baseline
2) With Eccono-Jets
3) After 500 miles with Eccono-Jets
Duplicate tests of each type (FTP, HFET, steady states, Federal Short
Cycle) were conducted at each test condition, except for the baselines,
when only one set of steady states was conducted. The accumulation of
500 miles consisted of 400 miles AMA durability on a test track and 100
miles of highway driving to and from the test track.
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Test Results
Individual test results appear in Tables 3, 4, and 5. Table 2 gives a
comparison between average results of baseline (standard mixture screws)
and final (after 500 miles with Eccono-Jets) test conditions. In gene-
ral, use of Eccono-Jets resulted in unchanged or increased emission
levels. In particular, their use resulted in the following:
-Increased HC emissions for all test procedures except the HFET and
idle in neutral which showed insignificant and 50% reductions respectively
-Unchanged or increased CO emissions for all tests
-Increased NOx emissions for the FTP, Federal Short Cycle, steady states
at 30 mph and idle
-Decreased NOx emissions for the HFET, steady states at 20, 40, 50 mph
Changes in average fuel economy were small for most tests. The HFET and
20 mph steady state showed very slight increases in fuel economy with
the use of Eccono-Jets (approximately 2%). Fuel economies for the FTP,
40 and 50 mph tests were effectively unchanged with less than 1% difference
between baseline and final test averages. Test procedures indicating
decreased fuel economy as a result of Eccono-Jets were the Federal Short
Cycle (approximately 7%), idle in neutral (13%), and idle in drive (30%).
The 30 mph steady state test showed an increase in fuel economy of 19%.
Conclusions
Although a few EPA tests of Eccono-Jets showed improvements in either
fuel economy or emissions, the official emissions test, the FTP, indicated
that use of Eccono-Jets resulted in increased emissions with no change
in fuel economy, while the HFET showed a very slight increase in fuel
economy (2%). This leads to the conclusion that there is neither a
general increase in fuel economy nor a decrease in emissions associated
with the replacement of standard idle mixture screws with Eccono-Jets.
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Eccono-Jets
Standard Idle Mixture Screw
Figure 1
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5
Table 1
TEST VEHICLE DESCRIPTION
Chassis model year/make - 1976 Chevrolet Impala
Emission control system - EGR, oxidation catalyst
Engine
type V-8, OHV
hore x stroke 3.875 x 3.48 in. (98.4 x 88.4 mm)
displacement 350 cu. in. (5380 cc)
compression ratio 8.5
maximum power @ rpm 145 hp @ 3800 rpm (108 kW)
fuel metering Carburetor, 2V
fuel requirement Unleaded regular, tested with-,
Indolene HO
Drive Train
transmission type Automatic 3-speed
final drive ratio 2.73
Chassis
type Sedan, 2 door
tire size HR 78 x 15
curb weight 4370 Ib.
inertia weight 4500 Ib.
passenger capacity six
Emission Control System
basic type Exhaust gas recirculation,
oxidation catalyst
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Table 2
Comparison of Baseline and Final Test Averages
Test
Procedure
FTP
HFET
Federal
Short Cycle
Steady State
20 mph
30 mph
40 mph
50 mph
Idle Neutral
Idle Drive
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
HC
CO
NOx
F.E.
(g/mi)
(g/mi)
(g/mi)
(mpg)
(g/hr)
(g/hr)
(g/hr)
(gal/hr)
Baseline
.60
11.9
1.82
13.5
.08
1.4
2.32
19.3
.15
.8
1.10
17.5
.06
0.0
.58
18.9
.09
0.0
.32
20.2
.05
0.0
.61
21.1
.04
0.0
1.44
20.9
3.00
0.0
2.28
.63
1.08
0.0
3.00
0.54
500 Miles
With Jets
.67
13.9
1.91
13.4
.07
1.7
1.62
19.7
.22
2.1
1.22
16.3
.59
8.9
.38
19.2
.44
8.7
.63
24.1
.08
0.1
.57
21.2
.05
0.0
1.40
21.0
1.44
0.5
4.32
.71
1.16
0.2
9.96
0.70
% Change
+ 12
+ 17
+ 4.9
- 0.7
- 13
+ 21
- 30
+ 2.1
+ 47
+163
+ 11
- 6.9
+883
+ infinite
- 34
+ 1.6
+389
+ infinite
+ 97
+ 19
+ 60
+ infinite
- 6.6
+ 0.5
+ 25
0
- 2.8
+ 0.5
- 52
+ infinite
+ 89
- 13
+ 7.4
+ infinite
+232
- 30
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Table 3
Baseline Tests
Test #
78-5059
78-5065
78-5060
78-6079
78-5063
78-5061
78-5061
78-5062
78-5062
78-5061
79-0064
Test
Bag 1
Bag 2
Bag 3
FTP
Bag 1
Bag 2
Bag 3
FTP
HFET
HFET
Fed. Short Cycles
Steady States
20 mph
30 mph
40 mph
50 mph
Idle Neutral
Idle Drive
HC
(gram/mi)
1.73
0.25
0.47
0.61
1.60
0.27
0.46
0.59
0.08
0.07
0.15
0.06
0.09
0.05
0.04
(gram/hr)
3.00
1.08
CO
(gram/mi)
37.3
3.8
7.7
11.8
34.8
4.8
8.3
11.9
0.9
1.8
0.8
0.0
0.0
0.0
0.0
(gram/hr)
0.0
0.0
NOx
(gram/mi)
2.82
1.29
3.83
1.87
2.73
1.13
2.22
1.76
2.43
2.21
1.10
0.58
0.32
0.61
1.44
(gram/hr)
2.28
3.00
Fuel Econoi
(mi/gal)
12.4
13.0
15.3
13.4
12.8
13.0
15.2
13.5
19.1
19.5
17.5
18.9
20.2
21.1
20.9
(gal/hr)
0.63
0.54
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Table 4
Eccono-Jets Installed
Test #
78-5053
78-5071
78-5066
78-5072
78-5069
78-5075
78-5067
78-5073
78-5067
78-5074
78-5068
78-5074
78-5068
78-5074
HC
Test (gram/mi)
Bag 1
Bag 2
Bag 3
FTP
Bag 1
Bag 2
Bag 3
FTP
HFET
HFET
Fed. Short Cycles
it ti it
Steady States
20 mph
20 mph
30 mph
30 mph
40 mph
40 mph
50 mph
50 mph
1.63
0.19
0.42
0.55
1.73
0.24
0.34
0.57
0.06
0.06
0.13
0.14
0.06
0.06
0.06
0.06
0.05
0.06
0.03
0.03
CO
(gram/mi).
36.1
3.9
5.8
11.0
38.1
3.7
3.9
10.8
0.8
0.6
0.8
0.7
0.0
0.00
0.0
0.0
0.0
0.0
0.0
0.0
NOx
(gram/ml)
2.71
1.13
2.41
1.81
2.55
1.14
3.66
1.74
2.63
2.27
1.24
1.16
0.63
0.64
0.95
0.79
0.74
0.62
1.72
1.33
78-5067
78-5073
78-5068
78-5073
Idle
Neutral
Idle
Drive
(gram/hr)
2.01
1.32
0.48
1.08
(gram/hr)
0.0
0.2
0.0
1.2
(gram/hr)
2.84
2.40
4.92
4.92
Fuel Economy
(mi/gal)
12.8
13.2
15.2
13.6
12.9
13.4
-15.6
13.8
18.6
19.7
16.2
16.6
18.7
18.9
23.6
24.3
20.4
21.5
19.9
21.3
(gal/hr)
0.62
0.61
0.60
0.60
oo
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Table 5
After 500 Miles With Eccono-Jets Installed
Test #
78-6345
78-5076
78-6344
78-5064
78-5055
78-6346
78-6343
78-5058
78-5070
78-5056
78-5070
78-5056
78-5070
78-5056
HC
Test (gram/mi)
Bag 1
Bag 2
Bag 3
FTP
Bag 1
Bag 2
Bag 3
FTP
HFET
HFET
Fed. Short Cycle*
it ii it *
Steady States
20 mph
20 mph
30 mph
30 mph
40 mph
40 mph
50 mph
50 mph
1.88
0.41
0.39
0.71
1.77
0.31
0.38
0.63
0.08
0.06
0.23
0.21
0.31
0.48
0.73
0.14
0.07
0.08
0.04
0.05
CO
(gram/ mi)
33.6
11.2
7.7
14.9
34.5
8.3
7.1
13.4
1.5
1.9
1.7
2.4
8.8
7.7
10.5
6.8
0.1
0.1
0.0
0.0
NOx
(gram/mi)
2.94
1.30
2.44
1.95
2.93
1.23
2.31
1.87
2.30
0.93
1.20
1.23
0.34
0.37
0.69
0.56
0.58
0.55
1.44
1.35
78-6343
78-5058
78-6343
78-5058
Idle
Neutral
Idle
Drive
(gram/hr)
1.32
1.68
0.96
0.96
(gram/hr)
0.4
0.0
0.0
0.0
(gram/hr)
3.84
4.44
10.32
10.08
Fuel Economy
(mi/gal)
12.9
12.8
15.2
13.4
12.7
12.9
15.3
13.4
19.4
19.9
16.0
16.6
19.4
19.2
24.2
23.9
21.2
21.1
20.9
21.0
(gal/hr)
0.70
0.73
0.71
0.68
vo
* Eccono-Jets set approximately 1/16 turn leaner than recommended.
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