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Technical Report
Particulate Measurement - Vehicle Preconditioning
by
Eugene Danielson
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 developments which may form the basis
for a final EPA decision, positon 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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Abstract
A study has been made of the effects of different vehicle pre-
conditioning on particulate emissions from three light-duty diesel
automobiles. The results indicate that prior extreme operation of a
vehicle can affect the level of particulate emitted during measurements
by the Federal Test Procedure. However, one LA-4 driving cycle appears
to provide adequate preconditioning for most cases. The duration and
magnitude of the preconditioning effect varies among vehicles.
Introduction
In the measurement of emissions from motor vehicles a certain
amount of specified vehicle preconditioning operation has been found to
be desirable before the standard test is performed. This practice
lowers test variability and decreases the possibility of test results
being intentionally skewed by extreme operational patterns of the
vehicle immediately prior to official measurements. For these reasons
it is important that the sensitivity of particulate emission levels to
prior vehicle operational patterns be investigated during the develop-
ment of new test procedures for particulate measurements from light-duty
diesel vehicles. Preconditioning operation should be specified as
necessary.
Obj ective
The objectives of this study are:
1. To determine the sensitivity of light-duty diesel particulate
emissions to prior preconditioning operation, and
2. to determine the rate at which particulate emissions recover
from the influence of prior preconditioning operation.
Test Procedure
Table 1 lists the test sequence followed in this study. The basic
philosophy adhered to in choosing the preconditioning cycles was to
alternately expose the vehicles to different extremes in vehicle ope-
ration, measure the effect on particulate emissions, and observe the
rate at which each vehicle returned to a previously established baseline
level.
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Three available vehicles were selected. The first was an EPA owned
1975 Mercedes 300D diesel automobile for which the particulate baseline
was well defined. The second vehicle was a 1977 Cutlass Supreme auto-
mobile equipped with a 1978 prototype 350 CID diesel engine, and the
third vehicle was a 1978 Peugeot 504 diesel automobile. Particulate
baseline emission levels were affirmed for each vehicle before this test
series began.
The wide open throttle (WOT) cycle was by far the most severe
operation to which the vehicles were exposed. In this cycle wide open
throttle accelerations were made from idle to 50 mph followed by closed
throttle deceleration to 35 mph, then wide open throttle acceleration to
50 mph followed by closed throttle deceleration to idle. Five of these
sequences were considered as one full cycle. As evident in Table 1,
three WOT cycles were run on the Mercedes and the Oldsmobile with particulate
emissions being collected on each cycle. These vehicles were then
preconditioned with one LA-4 cycle followed by emission measurement over
the Federal Test Procedure (FTP). Attempts to perform the WOT tests on
the Peugeot were abandoned because of a fear of over stress on the
vehicle.
Following the WOT runs, six FTP tests were run alternately pre-
conditioning each vehicle with a "blowout" cycle or the New York City
(NYC) cycle. The intent in this portion of the study was to alternately
expose the vehicle to opposite extremes of preconditioning and observe
the influence on particulate emissions. At the end of the test sequence,
a final FTP was performed using one LA-4 for preconditioning to deter-
mine if the vehicle had return to its original baseline particulate
emission level.
The New York City cycle (also known as Sulfate-8) has an average
speed of 7.09 mph and a maximum speed of 27.7 mph. This cycle was
chosen to represent mild low speed operation with low exhaust flow rates
that would tend to accumulate particulate deposits in the engine and
exhaust system. Equilibrium conditions were expected to be shifted in
the opposite direction during the "blowout" cycle when it was assumed
that a relatively high volume of hot exhaust would essentially "blow"
particulates out. If trapped particulate was removed, a lower than
baseline level of particulate would be emitted during a following FTP
because the clean exhaust system would be accumulating part of the
particulate emitted by the engine. The blowout cycle chosen was a 50
mph steady cruise condition for 15 minutes with double dynamometer
loading and no auxiliary engine cooling fan.
Results
The results of this study are illustrated in Figures 1, 2, 3, and
4. The data presented in Figure 1 were collected while the vehicle
operated over the wide-open-throttle cycle. All of the data in Figures
2, 3, and 4 were taken on the LA-4 driving cycle as part of the FTP with
different preconditioning as defined in Table 1.
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Particulate emission decreased sharply during successive WOT cycle
runs (Figure 1) on the Oldsmobile and the Mercedes. WOT tests were not
run on the Peugeot. Particulate emissions from the FTP immediately
following the WOT runs (Figure 2) were almost identical to the baseline
for the Mercedes but the Oldsmobile FTP particulate level was signifi-
cantly lower than the previously baseline. The next six FTP tests with
alternate NYC and blowout preconditioning show random variation near the
baseline for the Mercedes and the Peugeot but the Oldsmobile data shows
a trend of approaching the baseline with successive tests. The final
FTP results (test #8) with LA-4 preconditioning were near the baseline
for all three vehicles.
Figure 3 data indicate that the impact of extreme preconditioning
operation on subsequent particulate measurements is greater on the cold
start test phase than on the hot start. Hot start particulate emission
trends are plotted in Figure 4 and are most similar to the weighted FTP
data in Figure 2.
Discussion
Of the three vehicles studied, only the Oldsmobile was significantly
disturbed by the extreme preconditioning operation. The Mercedes arid
the Peugeot were influenced, as evidenced by their particulate emission
variation outside of normal baseline deviations (Figure 2), but the
effects were smaller than expected considering the severity of the
preconditioning operation and the possibility of particulate accumu-
lation in the engine and exhaust system. Even after the most extreme
WOT operation the Mercedes came back to baseline particulate emissions
on the next FTP test with only one LA-4 for preconditioning. Certainly
the Mercedes or the Peugeot show no preconditioning effects that indicate
a high emission sensitivity that will likely cause emission measurement
problems if one LA-4 preconditioning cycle is used.
The Oldsmobile did not come back to the baseline on the next test
after the WOT operation. One interpretation of the Oldsmobile results
shown in Figure 2 would be that particulate materials were cleaned from
the exhaust system by the WOT operation and that equilibrium was being
re-established during the subsequent eight tests. Final post-study
particulate emissions were back to the original baseline level. It is
also possible that the severe WOT operation has an internal effect on
the engine and influences particulate emissions through some phenomenon
occurring in the combustion chamber. This is less likely than the
exhaust system deposition theory.
Preconditioning effects were larger for all vehicles during the
cold start portion of the test procedure than during the hot start,
possibly because the cold start operation serves as a type of preconditioning
operation for the following hot start.
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It is reasonable to expect varying influence of preconditioning on
particulate emissions from vehicles with different designs of engines,
exhaust systems, and ultimately, particulate emission control systems.
Such effects are difficult to predict but particulate collectors such as
trap oxidizers may show peculiar preconditioning influences and future
studies of the type reported here may be necessary as new control
technology comes into use.
Conclusions
It is concluded from the results of this study that:
1. The degree to which light-duty diesel particulate emissions
are influenced by prior extreme vehicle operation varies among vehicles.
2. Particulate emissions during the cold phase of the test
procedure are influenced more by preconditioning operation than are hot
emissions.
3. Two out of the three vehicles tested recovered quickly from
preconditioning influences and one LA-4 driving cycle is considered to
provide adequate preconditioning for particulate measurement procedures.
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Mercedes 300D
Table I
Test Sequence
Oldsmobile 350D
Peugeot 504D
WOT* WOT*
WOT* WOT*
WOT* WOT* ~—
LA-4 LA-4
FTP* FTP*
NYC NYC NYC
FTP* FTP* FTP*
Blowout Blowout Blowout
FTP* FTP* FTP*
NYC NYC NYC
FTP* FTP* FTP*
Blowout Blowout Blowout
FTP* - FTP* FTP*
NYC NYC NYC
FTP* FTP* FTP*
Blowout Blowout Blowout
FTP* FTP* FTP*
LA-4 LA-4 LA-4
FTP*(Post study check) FTP*(Post study check) FTP*(Post study check)
*Cycles during which particulate material was collected (i.e.,
sample cycle). All other cycles listed are preconditioned cycles,
The dashed lines indicate the minimum 12 hour soak periods.
WOT - Wide Open Throttle
LA-4 - Los Angeles #4
FTP - Federal Test Procedure
NYC - New York City
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FIGURE 1
Preconditioning Study
WOT Particulate Emissions
5.0
4.0
3.0
2.0
1.0
Oldsmobile 350D
Mercedes 300D
Test Sequence
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1.2.-
FIGURE 2
Preconditioning Study
Weighted FTP Particulate Emissions
to
c
o
-r4
to
to
•H
Q)
JJ
rH
3
O
tfl
p-l
l.OJ
Oldsmobile Baseline
0.6
0.4
0.2
Peugeot Baseline
r
Mercedes Baseline
u
Symbol
A
D
O
Vehicle
Peugeot 504D
Mercedes 300D
Oldsmobile 35OD
NOTE: Symbols are after WOT and before preconditioning testing. Half-filled
symbols have NY cycle preconditioning. Open symbols have BO cycle
preconditioning, and filled symbols are after preconditioning testing.
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6
Test Sequence
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1.2 -
FIGURE 3
Preconditioning Study
Cold Start Particulate Emissions
IiA-4, Bags 1 and 2
Oldsmobile Baseline
Peugeot Baseline
0.4
Mercedes Baseline
0.2 .
Symbol
A
D
o
Vehicle
Peugeot 504D
Mercedes 300D
Oldsmobile 35OD
NOTE: Symbols are after WOT and before preconditioning testing. Half-filled
symbols have.NY cycle preconditioning, Open symbols have BO cycle
preconditioning, and filled symbols have after preconditioning testing.
4 5
Test Sequence
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1.2
FIGURE 4
Preconditioning Study
Hot Start Particulate _Emissions
LA-4, Bags 3 and 4
1.0
Oldsmobile Baseline
0.8 L
0.6 '-
0.4
Peugeot Baseline
Mercedes Baseline—*
Symbol Vehicle
A Peugeot 504D
0.2 F D Mercedes 300D
<£> Oldsmobile 350D
NOTE: Symbols are after WOT and before preconditioning testing. Half-filled
symbols have NY cycle preconditioning, open symbols have BO cycle
preconditioning, and filled symbols are after preconditioning testing.
3
Test Sequence
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