SDSB 79-16
Technical Report
A Study of One Gasoline-Fueled Engine Line
Comparing Emission Results Between 1969 Engines and 1979 Engines on
Three Test Procedures: the Heavy-Duty Transient Engine Test,
the Heavy-Duty 9-Mode Engine Test,
and the Light-Duty Truck Chassis Test
by
William B. Clemmens
and
Timothy P. Cox
July, 1979
NOTICE
Technical Reports do not necessarily represent final EPA decisions
or positions. They are intended to present technical analysis of
issues using data which are currently available. The purpose in
the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical develop-
ments which may form the basis for a final EPA decision, position
or regulatory action.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, Noise and Radiation
U.S. Environmental Protection Agency
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Table of Contents
Section Pflge
I. Summary *•
II. Test Procedure 2
III. Test Engines *
IV. Results 3
V. Conclusions *
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I. Summary
The 1977 Amendments to the Clean Air Act mandated EPA to set
new emission standards for heavy-duty (HD) vehicles or engines for
model years 1983 and 1985. These new standards were to represent a
percentage reduction "from the average of the actually measured
emission from heavy-duty gasoline-fueled vehicles or engines .
manufactured during the baseline model year." The baseline model
year was defined as the last model year in which engines were
uncontrolled with respect to a given pollutant. For the 1983 HC
and CO standards, the baseline model year (MY) is 1969. For the
1985 NOx standards, 1972 and 1973 have been determined to be the
baseline model years. (1972 was chosen to reflect the fact that
some 1973 models were already equipped with NOx controls).
EPA has initiated a testing program to determine these base-
line emission levels. This testing program includes multiple
transient tests on each baseline engine, during which emissions are
measured by the critical flow venturi constant volume sample
CFV-CVS technique. Additional testing on each engine includes the
current 9-mode certification procedure modified to use the CVS bag
procedure.
As part of the testing program, current technology heavy-duty
(HD) and light-duty truck (LDT) engines have also been tested. In
some cases these late model engines are direct descendents of the
1969 versions. Results from the first such family line tested
showed a striking contrast in emission results between the trans-
ient test and the current 9-mode test. This contrast was most
evident with carbon monoxide (CO) emissions. The later model year
engines from this particular engine line exhibit significantly
higher CO emissions not only over the transient test, but also when
compared to other current technology engines tested under the same
transient conditions. The contrast for HC emissions was not as
great. The HC emissions from the later versions of this engine
line were comparable to other current technology engines.
Interest in the CO contrast led to limited experimentation
with additional emission control hardware retrofitted to these
later model year engines. Data from these tests show that CO from
the modified engines was reduced by over 99 percent on the 9-mode
test relative to the average of essentially the same 1969 engines.
Yet, the emission levels mesured on the transient test from the
modified late model engines indicated only a 30-40 percent reduc-
tion (relative to their 1969 counterparts). The average of the
1969, 350 engines is similar to the estimated 1969 sales weighted
baseline. Therefore, the CO reduction from the sales weighted
baseline for the modified late model engines is in the same range
(35-43%). The 1977 Clean Air Act Amendments require a 90 percent
reduction of CO.
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The high level of CO emissions from these engines on the
transient test leads to the conclusion that these particular 1979
engines actually pollute at levels approaching uncontrolled levels
in the real world. Analysis of the brake specific fuel consumption
(BSFC) supports this conclusion (Table 6), if one assumes that
similar fuel rates with similar CO levels indicates a similar
degree of applied control technology.
The cause for the high CO emissions on the transient test
appears to be traceable to the particular type of carburetor (air
valve) used on the later model year engines. Since the carburetor
calibration and design are part of the emission control system, the
test data generated indicates that the relationship between emis-
sion reductions on the 9-mode and emission reductions in the real
world can be highly dependent on the emission control system used.
Certainly, for the engines tested, a reduction of CO emissions on
the 9-mode test resulted in little reduction on the transient test
procedure.
The inclusion of an engine from a 1979 LDT in the testing
program generated some interesting data. Based on the very high
emission levels from this engine, one concludes that emission
levels are quite sensitive to load (avg. power). The current LDT
compliance procedure tests LDTs at a weight approximately equal to
empty weight. The emission sensitivity of this particular LDT,
and, LDTs in general, to load is of concern only if the LDT com-
pliance procedure does not load the vehicles in a representative
manner.
II. Test Procedure
The program test schedule consisted of approximately three
cold start transient tests per engine (reference Federal Register,
Vol. 44, No. 31, February 13, 1979; Proposed Gaseous Emission
Regulations - 1983 and Later Model Year Heavy-Duty Engines, Subpart
N). In one case (1979, 350-CID) only two tests were run on the
engine due to time constraints.
Bag samples from a CFV type CVS of approximately 1500 SCFM
were used to collect emissions. One deviation from the Proposed
Rules involved collecting a separate bag sample for each of the
four segments that make up the test cycle. The Proposed Rules
use only one bag sample for the entire cycle. The change was made
for the purpose of collecting additional data on the baseline
engines.
In addition to the transient tests, one to three hot-start
9-mode tests (reference 40 CFR 86, Subpart D) were run on each
engine. The 9-mode test cycle was modified so that the CVS tech-
nique could be used to sample emissions. The modifications in-
cluded lengthening the cycle modes from one minute to five
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minutes Co obtain a sufficient bag sample. Also, only one cycle
(9-tnodes) was run instead of the usual two cycles (18 modes). This
was done to keep the length of the test as short as possible. Data
from the CVS 9-mode agrees well with data obtained by the Subpart D
test procedure (see Table 2).
In one case, a late model current technology engine was
obtained with the engine in a light-duty truck (LDT) chassis.
Three LDT Federal Emissions Chassis tests were performed on this
engine/vehicle prior to removing the engine.
III. Test Engines
Some of the late model engines tested were, for all practical
purposes, direct descendents (i.e., essentially the same engine) of
1969 engines. One 1979 heavy-duty engine and one 1979 light-duty
truck engine, with the exception of emission control devices,
closely resembled two 1969 350-CID engines (Table 1). The LDT
engine was obtained in a van-style chassis.
The certified configuration of the 1979 350-CID heavy-duty
engine included parameter calibrations (i.e., engine mod), and AIR,
but no EGR. The certified configuration of the 1979 400-CID
light-duty truck engine included parameter calibrations, EGR, EFE,
and a 260 cubic inch pellet-type oxidation catalyst (OC).
The 1979 400-CID light-duty truck engine was tested before the
1979 350-CID heavy-duty engine, but after the two 1969 engines had
been tested. The light-duty truck was the first catalyst engine
tested at EPA on the transient cycle. The extremely high CO data
on the 400-CID engine compared to the 1969 engines led to some
limited emission control system modifications on both the 1979
400-CID light-duty truck engine and the 1979 350-CID heavy-duty
engine. The only modifications to the 400-CID engine was the
addition of an AIR system (Table 1). The 350-CID heavy-duty engine
modifications consisted of the addition of the 260 cubic-inch
catalyst from the 400-CID engine (Table 1), and the use of unleaded
fuel. No other adjustments of engine parameters or calibrations
were attempted. Table 1 lists the engines and the various config-
urations tested.
IV. Results
A comparison of mean test results between the 1969 350-CID
engines tested and the 1979 engines in the certified configuration
is shown in Table 2. The transient CO results from the later model
year engines are quite high. Possibly of equal concern, however,
is the relationship of the transient CO results to the 9-mode
results between the four engines. The contrast between the test
procedures is even more graphically demonstrated in Table 3, which
shows the effect of the emission control system modifications on
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the 1979 engines. The modified control systems virtually elimi-
nated both CO and HC emissions on the Q-modnl tent . Yrt . on tho
transient test, the modified systems showed only a marginal
improvement in CO emissions. The modified control system did,
however, show a fairly significant reduction in transient HC
emissions.
Table 4 provides a perspective of the emission levels of the
1979 engines as a percentage of emission reduction from the average
of the parent 1969 engines. Both the light-duty truck and the
heavy-duty late model engines in their modified configurations
showed over a 99% reduction in CO on the 9-mode test. But, on the
transient test, only a 35-43 percent reduction (Table 5) in CO
emissions is realized when compared to the estimated 1983 standards
(based on engines tested as of March 15, 1979). The HC levels on
the transient test did, however, show a significant reduction
(Table 5) from the estimated baseline. The certified config-
urations showed a 75-82 percent reduction while the modified
versions ranged from 82-92 percent reduction.
Table 6 lists the average brake specific fuel consumption
(BSFC) over the individual test segments as determined by the
carbon balance method. The BSFC values between the certified
configuration and the modified configurations of both the 350- and
400-CID engines vary more than would be desirable. However, it
should be recognized that these measurements are taken over a very
short time span (approximately 300 seconds). Because of the short
measurement time, slight differences in the measured values tend to
be magnified.
The general trends of the data, however, are interesting.
For instance, the heavy-duty 1979 350-CID 4-barrel engine tends to
show better or equivalent fuel economy on the cold-start NYNF
(non-freeway) segment than the 1969 350 2-barrel engine, but poorer
fuel economy on the hot-start NYNF segment and both LAF (freeway)
segments. The 1979 LOT (400-CID 4-barrel) engine, on the other
hand, tends to show better fuel economy than the 1969 engines for
all segments except the LAF segment where the 1969 and 1979 engines
are nearly comparable. The exact meaning of these trends is still
uncertain. Hopefully, additional data from other engines tested in
the program will more clearly indicate fuel economy effects of the
marginal CO control of the late model engines. The data does,
however, tend to inicate that previous claims about substantial
fuel economy penalties associated with more stringent 9-mode
standards (i.e., 1979 HD Interim) may be misleading in terms of
real-world fuel economy.
Earlier it was mentioned that the 400-CID light-duty truck
engine was obtained in a light-duty chassis. Both EPA and the
manufacturer ran several light-duty truck chassis tests on this
vehicle (21.0 roadload HP). The results in grams per mile are
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found in Table 7. Of interest are the grams per mile derived from
the heavy-duty transient test, also shown in Table 7. Distance
traveled (miles) on the heavy-duty test are derived by multiplying
the average speed \J for each segment by the time spent within the
segment. Grams per mile are then determined by substituting miles
traveled for BHP-HR in the standard cold/hot emission calculation.
V. Conclusions
The first conclusion to be drawn from the test data is that
all configurations of the late model engines in this engine line
exhibit emission levels approaching uncontrolled levels of CO on
the transient test. These levels are of concern, especially when
comparing this engine line to other late model engines without
catalysts (Table 8). These other engines exhibit only about 50
percent of the CO emissions from the 350/400-CID engine line.
Several potential causes for the high CO levels can be hypo-
thesized. First, the late model 350/400-CID engines use an "air
valve" type 4-barrel carburetor, which has an auxiliary butterfly
valve operated by air velocity. The other late model engines
(Table 8) use a more conventional 4-barrel carburetor. It can be
hypothesized that under transient heavy loads, the mixture control
and distribution of the "air valve" carburetor's secondary circuit
or possibly the overall control of the secondary circuit may not be
as good as the secondary circuit in the conventional carburetor.
Evidence supporting this hypothesis can be found by comparing the
transient and 9-mode CO test results of the 1979 350-CID heavy-duty
engine in the certified configuration (Table 2) to the results of
the other current technology engines (Table 8). The 9-mode CO
results of the 350-CID engine are slightly lower than the CO levels
of other engines. Yet, when these engines are exercised trans-
iently, as in the real world, over the transient test cycle, the CO
of the 350-CID engine becomes nearly double that of the other
engines. This pattern of high CO appears to be followed by the LOT
400-CID engine (Table 2) which also has an "air valve" (Table 3)
carburetor.
Another possible cause for the high CO on the late model
350- and 400-CID engines could be lack of sufficient air flow
capacity in the AIR system. The lack of oxygen is certainly a
factor in the CO reduction on the 9-mode for the modified 400-CID
catalyst-equipped LOT engine (Table 3). But, further investigation
\J EPA Technical Report, "Selection of Transient Cycles for
Heavy-Duty Vehicles," HDV 78-02, June, 1978.
21 Federal Register, Vol. 44, No. 31, February 13, 1979 Proposed
Gaseous Emission Regulations - 1983 and Later Model Year Heavy-Duty
Engines, Subpart N, §86.1344.
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shows Chat both the 1979 350-CID HD engine and the AIR system added
to the 400-CID engine are nearly identical (pump calibration,
diverter valve, calibration, and pulley ratio) to the AIR system on
the 1979 454-CID engine. Yet, the 454-CID engine exhibits less
than half the level of CO (Table 8) emitted by the 350- and 400-
CID engines. It seems unlikely that this AIR system could supply
sufficient air flow for a 454-CID engine and not supply sufficient
air flow for a 350- or 400-CID engine. Therefore, lack of air
flow, although not totally discounted, does not appear to be a
major factor in the high CO levels.
In contrast to the CO reductions shown on the transient test,
HC reductions tended to be rather significant (60-90%). However,
even though the transient HC reductions tended to be significant,
the 9-mode test still overestimated the transient emission reduc-
tions by 10-30%.
Another point of interest about the data from this engine line
is that correlation for both HC and CO between the transient test
and the 9-mode test can be obtained. Unfortunately, this correla-
tion (Table 9) is not meaningful in an engineering context. It is
true for this engine line that lower HC and CO emissions on the
9-mode procedure produce lower transient emission results. But for
instance, even when the 9-mode CO emissions are totally eliminated
(i.e., intercept = 0), the correlation line would predict over 100
g/bhp-hr of CO.on the transient test (Table 10). At the estimated
90 percent reduction standard of 1.3 g/BHP-hr HC and 15.6 g/BHP-hr
CO, both of the predicted 9-mode values (HC and CO) would be
negative, -0.7 g/BHP-hr HC, and -268 g/bhp-hr CO, totally meaning-
less numbers. Therefore, it can be said for this engine line in
the configurations tested, there is no 9-mode HC or CO result that
would correlate to a 90% reduction in real world emissions.
A final point worthy of discussion is the relation of the
derived grams per mile on the HD transient test to the grams per
mile of the LOT tests (Table 8). While it is recognized that the
heavy-duty test does load the engine more than the LOT test, the
test data almost indicates that for power levels at some point
above the loads imposed during the LOT test procedure, the 1979 LOT
engine is nearly uncontrolled for CO emissions.
Two facts bear on the impact on ambient air quality by LDTs:
1) the apparent sensitivity of the LDTs to load; and 2) the
Federal Emission Compliance Procedure tests LDTs at a weight
approximately equal to empty weight. If the compliance procedure
loads LDTs in a representative manner, then the sensitivity to load
is of little concern. However, if the compliance procedure does
not load the vehicles in a manner representing in-use loading, then
the emission sensitivity to load becomes a very real concern.
Based on the potential adverse air quality impact if the latter
case is true, the authors think the representativeness of the LOT
test loads should be reexamined.
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Table 1
Description of Engines Tested
Engine #
BLT8
BLT11
CTE6
PCTE6*
CTE3
PCTE3**
MY
1969
1969
1979
1979
1979
1979
CID
350
350
350
350
400
400
USE HP
HD 180
HD 166
HD 136
MOD 136
LOT 183
MOD 179
RPM
3798
3609
3198
3198
3742
3579
AECD
None
None
Air
Air
EGR/OC/EFE
EGR/OC/EFE
Notes:
AIR = air injection system.
EFE = early fuel evaporation system.
EGR = exhaust gas recirculation system.
OC = oxidation catalyst.
MOD
OC
AIR
CARBURETOR
2 Barrel
2 Barrel
4 Barrel
4 Barrel
4 Barrel
4 Barrel
GOVN
Yes
Yes
No
No
No
No
* Same engine as CTE6
** Same engine as CTE3
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Table 2
Comparison of 1969 Engine Emission Results to Emissions Results of
1979 Engines in Their Certified Configurations (Grams/BHP-HR)
Engine #
BLT8
BLT11
CTE6
CTE3
Manufacturer
MY
1969
1969
1979
1979
CID USE
350 HD
350 HD
350 HD
400 LDT
Transient 9-Mode
HC CO NOx HC CO NOx
9.57 169.70 4.70 11.05* 182.50* 3.68*
6.21 126.13 5.36 7.25 131.47 4.21
3.14 118.07 6.23 .79 14.62 7.83
2.21 131.81 2.32 .81 45.91 2.59
Results**
oo
i
CTE6
1979
350
HD
.770
13.17
5.89
* CT mode determined from BLT11
** Raw emission measurements per 40 CFR 86, Subpart D
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Table 3
Effect of Modifications to 1979 Engines (Grams/BHP-HR)
Engine # MY CID USE
Certified Configuration
CTE6 1979 350 HD
CTE3 1979 400 LOT
Modified Configuration
PCTE6* 1979 350 MOD
PCTE3** 1979 400 MOD
Transient 9-Mode
HC CO NOx HC CO NOx
3.14 118.07 6.23 .79 14.62 7.83
2.21 131.80 2.32 .81 45.91 2.59
2.29 89.57 5.96 .21 .18 7.42
1.00 99.24 2.38 .06 2.46 2.76
* Same engine as CTE6
** Same engine as CTE3
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Table 4
Brake Specific Emission Reductions
as a Percentage of Average 1969 350-CID Emissions
Engine #
I. Average
BLT8
BLT11
AVERAGE
MY CID
Transient
USE BSHC BSCO BSNOx
9-Mode
BSHC BSCO BSNOx
1969 Emission Levels (g/BHP-HR)
1969 350
1969 350
II. Certified Configuration
CTE6
CTE3
III. Modified
PCTE6**
PCTE3***
1979 350
1979 400
Configuration
1979 350
1979 400
HD 9.57 169.70 4.90
HD 6.21 126.13 5.36
7.89 147.92 5.13
(% Reduction)
HD 60.2% 20.2% -21.4%
LOT 72.0% 10.9% 54.8%
(% Reduction)
HD 71.0% 39.4% -16.2%
LOT 87.3% 32.9% 53.6%
11.05* 182.50* 3.68*
7.25 136.47 4.18
9.15 156.99 3.93
91.4% 90.7% -99.2%
91.2% 70.8% 34.1%
97.7% 99.9% -88.8%
99.3% 98.4% 29.8%
* CT mode determined from BLT11
** Same engine as CTE6
*** Same engine as CTE3
o
i
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Table 5
Brake Specific Emission Reductions as a Percentage
of the 1969 Baseline***
Engine #
MY
CID
USE
BSHC
Transient
BSCO
NOx
I. 1969 Baseline*** (g/BHP/HR)
Estimated 1983 Standard*** (g/BHP/HP)
(i.e., 90% reduction of baseline HC and CO levels)
12.96
1.30
156.03
15.60
6.14
II. Certified Configuration (% Reduction)
CTE6 1979 350 HD
CTE3 1979 400 LOT
75.8
82.9
24.3
15.5
III. Modified Configuration (% Reduction)
PCTE6* 1979 350 HD
PCTE3** 1979 400 LDT
82.3
92.3
42.6
36.4
* Same engine as CTE6
** Same engine as CTE3
*** Based on engines tested as of 3/15/79 (approximately 75% of the 1969 market represented)
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Table 6
Average Brake Specific Fuel Consumption (Ib/BHP-HR) Over the Transient Cycle
Engine No.
BLT8
BLT11
CTE6
PCTE6*
CTE3
PCTE3**
MY
1969
1969
1979
1979
1979
1979
Composite
CID USE BSFC
350 HD .659
350 HD .613
350 HD .723
350 MOD .838
400 LOT .636
400 MOD .687
Cold Start
NYNF LANF
1..317 .736
1.743 1.026
1.488 769
1.309 .773
.921 .678
.912 .722
LAF
.595
.517
.722
.663
.582
.633
NYNF
.819
.860
.994
.988
.692
.763
NYNF
.937
.807
1.054
1.055
.806
.863
Hot Start
LANF
.702
.732
.760
.788
.699
.761
LAF
.589
.532
.635
.853
.585
.646
NYNF
.873
.731
.805
.832
.598
.663
* Same engine as CTE6
** SAme engine as CTE3
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Table 7
Comparison Betweeen LDT Chassis Test Emissions (g/mile)
and HP Transient Engine Test Emissions (g/mile)
No. of
Engine # MY CID Use Tests HC CO NOx MPG
CTE3 1979 400 LDT
MFC LDT Chassis Test 3 .61 13.87 1.58 10.63*
EPA LDT Chassis Test 3 .73 15.30 1.47 11.20*
EPA HD Engine Test 3 4.09 243.60 4.28 5.28**
CTE6 1979 350 HD
EPA HD Engine Test 2 4.64 174.52 9.19 5.55**
BLT11 1969 350 HD
EPA HD Engine Test 3 9.25 189.08 8.02 6.40**
BLT8 1969 350 HD
EPA HD Engine Test 3 16.41 290.79 8.40 5.43**
* LDT city fuel consumption
** HD composite fuel economy
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Table 8
Emission Results from Late. Model Engines Tested to Date (1/5/79)
(g/BHP-HR)
Engine #
CTE1
CTE2
CTE4
MY
1977
1979
1978
CID
391
454
404
USE
Cal. HD
HD
Cal. HD
HC
2.81
2.26
3.98
Transient
CO
59.02
48.69
54.56
NOx
6.71
6.92
5.01
9-Mode
HC CO
— —
.39 17.33
.63 18.07
NOx
—
7.38
5.00
1969 Baseline* (g/BHP-HR)
Estimated 1983 Standard* (i.e., 90%
reduction of baseline HC and CO levels)
12.96 156.03
1.30 15.60
* Based on engines tested as of 3/15/79 (approximately 75% of the 1969 market represented)
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Table 9
Linear Regression of Transient and 9-Mode BSCO Emissions
Transient 9-Mode Transient 9-Mode
Engine No. MY CID Use HC (y) HC (x) CO (y) CO (x)
BLT8 1969 350 HD 9.57 11.05 169.70 182.50
BLT11 1969 350 HD 6.21 7.25 126.13 131.47
CTE3 1979 350 HD 2.21 0.81 118.07 14.39
PCTE3 1979 350 MOD 1.00 0.06 89.57 185
CTE6 1979 400 LOT 3.14 0.79 131.81 45.94
PCTE6 1979 400 MOD 2.29 0.21 99.24 2.46
Linear Regression: y = mx + b HC CO
Slope (ra) 0.6793 0.322
Intercept (b) 1.7865 102.1713
r2 = 0.9647 0.7644
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Table 10
Emissions Projected from Linear Regression
(g/BHP-HR)
Transient
HC CO
9-Mode
HC CO
90% Reduction from Baseline 1.3*
Zero 9-Mode Emissions
1.3*
1.786
15.6*
102.17
-0.7161
0
-268.60
0
* Based on engines tested as of March 15, 1979.
* US. GOVERNMENT PRINTING OFFICE: 1979- 650-029/0015
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