EPA-AA-TAEB 75-13
EVALUATION OF THE
SPECIAL FORMULA CENTRIFUGAL ADVANCE SPRINGS
December 1974
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Environmental Protection Agency
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The Special Formula Company of Minneapolis has developed a set of
centrifugal advance springs to replace the stock centrifugal advance
springs on 1974 General Motors cars. The Special Formula springs were
claimed to improve the fuel economy of 1974 GM cars without increasing
exhaust emissions to levels above the 1974 Federal emission standards.
Since test data supplied to the EPA by Special Formula supported their
claims of improved fuel economy and in addition indicated a substantial
reduction in exhaust emissions, a test program was set up to evaluate
the effects of the Special Formula springs.
Vehicle Description
The vehicle used for the evaluation was a 1974 Chevelle Malibu
Classic equipped with a 350 CID (5700 cc) engine. The car is described
in detail in the Vehicle Description table.
Test Program
The vehicle was tested in accordance with the 1972 Federal Test
Procedure (Federal Register, November 15, 1972, Volume 37, No0 221, Part
II) with the exception that the vehicle was warmed up prior to the actual
emission test. Fuel economy was measured over the LA4 and the EPA
Highway Cycle.
Prior to the start of emission testing the vehicle was adjusted
to manufacturer's specifications.
Two baseline emission and fuel economy tests were run with the
vehicle adjusted to manufacturer's specifications. The standard
centrifugal advance springs were then removed from the distributor and
the Special Formula springs installed. After installation of the
Special Formula springs the ignition timing was checked and found to
be unchanged from the baseline setting. Two more emission and fuel
economy tests were run on the vehicle. After completion of the emission
tests, the distributor curve was checked using both the standard
springs and Special Formula springs. The distributor curves are
shown Figure 1,
Test Results
Exhaust emission data, summarized below, shows that replacing the
standard centrifugal advance springs with the Special Formula springs
caused an increase in HC, CO and NOx emissions. Fuel economy over the
LA4 driving cycle was not changed by the use of the Special Formula
springs.
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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
fut ure s t andards.
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 wit.h 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
c-f 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 tq^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/'.
.!/ 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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25
20
-Special-lorinula-.
Standard Spiring
Manufacturers
Tolerance
500
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HOT START '72 FTP COMPOSITE MASS EMISSIONS
GRAMS PER MILE
(GRAMS PER KILOMETRE)
HC
CO
NOx
Baseline Avg. of 2 tests
Special Formula Springs
avg. of 2 tests
% Change
1.97
(1.22)
2.22
(1.38)
16.3
(10.1)
18.3
(11.4)
1.39
(0.86)
1.84
(1.14)
+13%
+12%
+32%
FUEL ECONOMY
(FUEL CONSUMPTION)
13.8 miles/gal.
(17.0 litres/100 km)
14.1 miles/gal.
(16.7 litres/100 km)
+2%
(-2%)
On the EPA Highway Cycle the Special Formula Springs had the effect
of substantially increasing the HC, CO and NOx emissions. Fuel economy
over the EPA Highway Cycle improved slightly.
EPA HIGHWAY CYCLE COMPOSITE MASS EMISSIONS
GRAMS PER MILE
, (GRAMS PER KILOMETRE)
FUEL ECONOMY
HC CO NOx (FUEL CONSUMPTION)
0.75
(0.47)
1.02
(0.63)
+36%
9.9
(6.2)
13.2
(8.2)
+33%
1.64
(1.02)
2.26
(1.40)
+38%
19.0 miles/gal.
(12.4 litres/100 km)
19.7 miles/gal.
(11.9 litres/100 km)
+4%
(-4%)
Baseline - avg. of 2 tests
Special Formula springs
% Change
The distributor curves (Figure 1) indicate that the Special Formula
springs substantially increase the degrees of centrifugal advance
(compared to the standard springs) at low and intermediate engine speeds.
Maximum obtainable centrifugal advance is not changed by the use of the
Special Formula springs.
Conclusions
The test results show that, on the car tested, replacing the standard
centrifugal advance springs with the Special Formula springs caused
only a slight improvement in highway fuel economy while causing a sign-
ificant increase in exhaust emissions.
These results cannot be extrapolated to other 1974 GM engines.
Testing of each engine family in the GM line would be necessary to fully
investigate the effects of the Special Formula springs.
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1974/Chevelle Malibu Classic
Emission control system - AIR/EGR, PCV
Engine
type 4 cycle, ohv, V-8, Otto Cycle
bore x stroke 4.0 x 3.48 in./101.6 x 88.4 mm
displacement 350 CID/5700 cc
compression, ratio 8.2:1
naxiuuh power @ rpm 145 bhp (? 3800/108 kw @ 3800
fuel metering 2 barrel carburetor
fuel requirement 91 RON unleaded
Drive: Train
transmission type .........3 speed automatic
final drive ratio . N.A.
Chassis
type body/frame, front engine, rear wheel drive
tire size G78-14
curb weight ............ 4060 lbs./1842 kg
inertia weight 4500 Ibs.
passenger capacity .... 5
Emission Control J5y stein
basic type AIR/EGR
EGR type hot, not proportional
rate N.A.
air injection . continuous, not modulated
size pump 19 CID/310 cc per revolution
drive ratio ..... 1.31 times engine speed
location . ..... exhaust ports
additional features
durability accumulated on system . . 12000 miles/7450 km
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TABLE I
TEST //
Baseline
16-6896
21-6921
Average
INDIVIDUAL BAG MASS EMISSIONS IN GRAMS PER MILE
HOT START '72 FTP
Hot Transient
HC
CO
C02
NOx
MPG
1.88 18.9 548. 1.83 15.2
2.25 17.0 1.82
2.07 18.0 548. 1.83 15.2
Special Formula Springs
21-6987 2.51 20.6 549. 2.46 15.1
21-7000 2.30 17.8 561. 2.61 14.9
Average 2.41 19.2 555. 2.54 15.0
HC
CO
Stabilized
C02
NOx
MPG
1.92 15.4 670. 1.06 12.7
1.84 14.1 .93
1.88 14.8 670. 1.0 12.7
2.08 18.6 628. 1.22 13.4
2.00 16.2 640. 1.17 13.2
2.04 17.4 634. 1.20 13.3
Hot '72 FTP Composite
HC CO C02 NOx MPG
1.90 17.1 612. 1.43 13.8
2.03 15.5 1.35
1.97 16.3 612. 1.39 13.8
2.29 19.6 590. 1.81 14.1
2.15 17.0 602. 1.86 14.0
2.22 18.3 596. 1.84 14.1
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TABLE II
EPA HIGHWAY CYCLE EMISSION AND FUEL ECONOMY
GRAMS/MILE
TEST # HC CO COo NOx MPG
Baseline
16-6896
21-6921
Average
0.
0.
0.
74
76
75
9.
10.
9.
3
5
9
448 o
454.
451.
1.69 19.1
1.58 18.8
1.64 19.0
Special Formula Springs
21-6987 1.01 13.7 431. 2.36 19.5
21-7000 1.02 12.6 423. 2.16 19.9
Average 1.02 13.2 427. 2.26 19.7
* US. GOVERNMENT PRINTING OFFICE: 1979- 651-112/ 0102
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