- DRAFT -
Air Conditioning Correction Factors in MOBILE6
Report Number M6.ACE.002
March 12,1998
John Koupal
Assessment & Modeling Division
U.S. EPA Office of Mobile Sources
1 ABSTRACT
Revised air conditioning exhaust emission correction factors are being proposed for MOBILE6.
The proposed factors are based on testing of 38 vehicles at two locations, using a test procedure
meant to simulate air conditioning emission response under extreme "real world" ambient
conditions. These factors are meant to predict emissions which would occur during full loading
of the air conditioning system, and will be scaled down in MOBILE6 according to ambient
conditions input by the user if appropriate. It was concluded that the data used in the
development of the proposed factors adequately represents real world conditions, based on the
results of a correlation vehicle tested at both test sites and a full environmental chamber. In
general, emissions were found to increase significantly with air conditioning operation, but under
some conditions HC and CO emissions decreased. For running emissions, speed-based
correction factors were developed separately for Light-Duty Vehicles (LDV's) and Light-Duty
Trucks (LDT's) for all pollutants; separate HC and CO corrections were also developed for high
emitters. Correction factors for start driving were also assessed.
2 INTRODUCTION
Recent studies conducted primarily as part of the Supplemental Federal Test Procedure (SFTP)
rulemaking development process indicate that vehicle fuel consumption and exhaust emissions
increase substantially when the air conditioner is in operation. As the traditional method for
accounting for the effects of air conditioner load - increasing dynamometer horsepower by 10% -
is not adequate for characterizing this emission increase, new certification test procedures aimed
at reducing emissions when the air conditioner is in operation were implemented as part of the
SFTP rule. Air conditioning correction factors are included as an optional element of MOBILES;
however, these factors are based on testing performed in the early 1970's and are considered so
outdated that the user is discouraged from using them in the MOBILE User's Guide. Given the
recent findings on air conditioning emissions, revised air conditioning correction factors are
M6. ACE.002 DRAFT Page 1
-------
clearly needed.
This report presents the "full-usage" air conditioning exhaust correction factors proposed for
MOBILE6. Full-usage correction factors are meant to represent the emission increase when the
A/C system is inducing full system load on the vehicle, as would occur under extreme ambient
(temperature, humidity and solar load) conditions. Since it not appropriate to apply these factors
to all ambient conditions, MOBILE6 will scale these factors down based on the ambient
conditions under which the model is being run (the development of appropriate scaling factors is
discussed in Report Number M6.ACE.001, "Air Conditioning Activity Effects in MOBILE6").
Discussion in this report includes the testing used to generate A/C emission data, correlation
between the two test sites and with expected real-world results, and the development of the full-
usage correction factors. It should be noted that the correction factors presented in this report
apply to vehicles which do not comply with the SFTP requirement. The treatment of air
conditioning correction factors for vehicles complying with the SFTP requirement will be
addressed in a separate report.
3 TESTING
3.1 Vehicles
The data used for this analysis was generated through testing performed at EPA's National
Vehicle and Fuel Emissions Laboratory and through an EPA contractor, Automotive Testing
Laboratories (ATL), in East Liberty, Ohio. 26 vehicles were tested at EPA and 12 were tested at
ATL, including one vehicle tested at both locations for correlation purposes (treated as two
separate vehicles for the purpose of this analysis). A list of the vehicles tested is contained in
Table 1. The sample consisted of 1990 and later vehicles categorized as follows: 24 cars /14
trucks, 32 Ported Fuel Injection (PFI) / 6 Throttle-Body Injection (TBI), and 28 Tier 0 / 10 Tier 1.
Each vehicle was designated either as a "normal" emitter or "high" emitter using the following
emission cutpoints over the Running LA41 : 0.8 g/mi HC, 15.0 g/mi CO and 2.0 g/mi NOx (the
cutpoints were applied independently for each pollutant, so that a vehicle could be a high emitter
for HC and a normal emitter for NOx). These cutpoints yielded five high emitters for HC, three
for CO and two for NOx.
3.2 Test Procedure
EPA's new air conditioning test procedure is based on use of a full environmental chamber at 95 °
F, 40% Relative Humidity and full solar load (850 Watts/Meter2). This type of facility was not
available to EPA at the time of testing, so use of a procedure which simulated these conditions
was required. A/C-on tests were conducted in a standard emission test cell at 95 ° F and 50
1 "Running LA4" emissions were derived from the combination of emissions from Bag 2 and a 505 cycle run
warmed-up (i.e. without a soak). More detail on this calculation can be found in MOBILE6 Report No.
M6.STE.002, "The Determination of Hot Running Emissions from FTP Bag Emissions"
M6. ACE.002 DRAFT Page 2
-------
grains/pound of humidity with standard cooling and the driver window down. The A/C system
was set according to the SFTP requirements; maximum A/C and blower setting with
recirculation mode if so equipped. Rather than attempting to represent a condition that would
actually occur in-use, this simulation is meant solely to induce the level of A/C system load on
the vehicle which would occur in the real world under extreme ambient conditions. Operating
with the driver window down and with standard cooling is meant to compensate for the lower
humidity level and lack of solar load inherent in the standard cell. This simulation method
showed adequate correlation with SFTP environmental cell conditions during the development of
the SFTP rulemaking2, and is a straightforward way to approximate real-world air conditioning
emissions using a standard cell setup. A/C-off tests were run in standard FTP ambient conditions
(75° F, 50 grains/pound humidity).
The vehicles were run in a warmed-up condition over EPA's facility-specific inventory cycles3,
ARB's Unified Cycle (the LA92), and the New York City Cycle one time each with the A/C on
and A/C off. A cold start ST014 cycle was also run in both conditions for the purpose of
assessing start A/C factors (information on all driving cycles used in this test program is shown
in Table 2). The EPA tests were run on a 48-inch electric dynamometer, while the ATL testing
used a twin 20-inch electric dynamometer; all tests were run without the 10% A/C load
adjustment factor typical to standard emission tests. Both bag and modal data were collected.
3.3 Overall Results
As with previous versions of the model, MOBILE6 will contain correction factors which
estimate the emission impact of changes in temperature. Emissions at temperatures higher than
75 ° F will be determined in the model first by applying a base temperature correction, then
applying the A/C correction factor appropriate for that temperature. A/C correction factors must
be developed separately from the baseline temperature corrections in order to avoid double-
counting temperature impacts. For this analysis, therefore, the A/C-off results were corrected
from the temperature the test was conducted (nominally 75 °, although minor variability is
common) to the A/C-on temperature (nominally 95 °) for each paired test. Since MOBILE6
temperature correction factors will not change from the MOBILES corrections, MOBILES
2 Results from a correlation program between this simulation and a full environmental chamber over a sample of six
Tier 1 vehicles can be found in AAMA/AIAM's comments to EPA on the proposed SFTP rulemaking (EPA Docket
No. A-92-64 ItemIV-D-10).
3 For detail on the development of EPA's facility-specific inventory cycles, see MOBILE6 Report No. M6.SPD.001,
"Development of Speed Correction Cycles"
4 ST01 is a 1.4 mile cycle developed to specifically characterize driving behavior following startup. The cycle was
developed from an in-use driving survey conducted in Baltimore, Spokane and Los Angeles as part of the SFTP
rulemaking process.
M6. ACE.002 DRAFT Page 3
-------
temperature corrections were used5. The Bag 2 corrections were used for all running tests, and
Bag 1 corrections were used for the cold start ST01 test6.
Once the temperature correction was applied, the A/C impact was analyzed by taking the ratio of
emissions with the A/C on to corrected emission levels with the A/C off results (referred to
throughout the report as the "A/C ratio"). This ratio was based not on each individual vehicle,
but on the average A/C on and A/C off levels over all vehicles for each driving cycle. Results of
this analysis on the running cycles over all vehicles are shown in Figures 1-4 for fuel
consumption, HC, CO and NOx; in these figures, the driving cycles are ordered from lowest
(NYCC) to highest (FWHS) average speed. Although a more detailed analysis is covered in
Section 5, these figures highlight some general trends that shape the development of running
correction factors:
Fuel Consumption and NOx: Increases in fuel consumption7 and NOx generally result from the
added load placed on the engine by the air conditioning system when the A/C compressor (which
is propelled by the engine) is engaged. Figures 1 and 2 show a consistent increase over all
cycles, with a strong dependency on average speed. In general A/C load is fairly constant over
all operation, so the relative additional load placed on the engine depends on the loading
condition of the engine itself. Larger relative increases in engine load due to air conditioning
occur at lower speeds, while at higher speeds the relative additional load placed on the engine by
the air conditioning system is smaller. This results in a decreasing A/C ratio as average cycle
speed increases.
HC and CO: Although the changes in relative A/C loading (and hence fuel consumption)
mentioned above can also drive increases in HC and CO, more significant increases are usually
the result of fuel enrichment. Excess fuel enrichment can result from the added load placed on
the engine and/or fuel calibrations that simply add fuel because the air conditioning system is in
operation. Although not the case for every vehicle, the effects of this enrichment on emissions
(particularly CO) from the vehicles that do experience excess fuel enrichment are so large that
average fleet emissions are increased significantly. Figure 3 shows A/C ratio for HC; the ratio is
higher at the low and high ends of the speed range, but actually drops below 1.0 in the mid range.
One explanation of this is that increased combustion temperatures resulting from higher engine
load reduce HC emissions in some situations. Figure 4 shows higher ratios for CO but less
dependence on speed. This suggests the stronger role of vehicle calibration in driving the CO
5 The temperature corrections will be modified to accommodate the start/running split new to MOBILE6, but the
base corrections will not change. The start/running split has not be developed, so for this analysis the MOBILES
Bag corrections were applied.
6 MOBILES temperature correction factors can be found in "Compilation of Air Pollutant Emission Factors, Volume
II - Mobile Sources" (AP-42), Page H-24
Fuel consumption correction factors are presented in this report primarily because of the proposed treatment of CO
for vehicles complying with the SFTP requirement, to be discussed in a future report.
M6. ACE.002 DRAFT Page 4
-------
emission increase. One caveat of both the overall HC and CO results shown here is that they are
largely driven by the high emitters in the sample, which (as discussed in Section 5) had lower
A/C ratios. The HC and CO increases for normal emitters were found to be significantly larger
than those shown in Figures 3 and 4.
4 CORRELATION
Preliminary data presented at the October 1997 MOBILE6 workshop indicated a potential offset
between the results from vehicles tested at EPA and those tested at ATL8. A/C ratios from the
ATL sample were lower than EPA on average for fuel consumption and all three pollutants.
This raised a question about whether the simulation as conducted at ATL induced comparable
A/C system loading to the procedure as conducted at EPA. A related issue is whether loading
induced by the simulation as conducted at either site could be considered "full-usage", as defined
for the purpose of this analysis by the conditions used for the SFTP certification test (95 ° F, 40%
Relative Humidity, 850 W/m2 solar load). To investigate both issues, a correlation vehicle was
run over all test cycles using the simulation procedure at EPA and ATL, and on a subset of cycles
under the SFTP test conditions at GM's environmental chamber in Rochester, New York. This
vehicle was instrumented to monitor A/C compressor cycling and compressor pressures (high
and low side) on a real-time basis to gain a fuller sense of how the vehicle's A/C system was
loaded at each location.
Emission results for the four cycles tested at all three locations are shown in Table 3. There is
quite a bit of variability in the HC, CO and NOx results, making it difficult to discern any clear
trend. Judging from the large swings in each pollutant, it appears that the vehicle went into
enrichment sporadically between sites, resulting in a wide range of A/C ratio results across the
test matrix. Thus, it is difficult to draw conclusions from the emission data (and particularly the
A/C ratios) alone. The correlation analysis therefore focussed on fuel consumption (carbon) ratio
and compressor operation to determine whether a difference in the relative loading placed on the
vehicle between the three sites can be distinguished. The carbon ratio results in Table 3 show the
ATL results to be slightly lower than EPA for each cycle. However, the EPA and ATL carbon
ratios are higher than the GM ratio for three of the four cycles, and the three locations show
relatively consistent carbon ratios over the New York City, Unified and Arterial cycles. The
exception to the latter point is the High Speed Freeway cycle, for which the GM ratio (as well as
the A/C-on carbon levels) are significantly lower than EPA or ATL.
Table 4 contains compressor behavior data, expressed in terms of the compressor fraction (the
fraction of time the compressor in engaged during the test), and average high and low side
compressor pressures, on which compressor torque in based. The data indicate that a) the
compressor was engaged at all locations 97% or more of the time on each of the cycles, and b)
for the New York City, Unified and Arterial cycles a strong difference is not observed in the
compressor pressures. The exception again is the High Speed Freeway cycle, for which the GM
1 "A/C Effects in MOBILE6", presentation at the October 1997 MOBILE6 workshop
M6. ACE.002 DRAFT Page 5
-------
data shows significantly lower compressor pressures than ATL or EPA. From these data and the
fuel consumption results, it is apparent that the A/C system load on the high speed freeway cycle
in the full environmental cell was much less than that produced by the simulation at EPA or
ATL. The most plausible explanation for this is the use of a variable speed fan in the full
environmental cell, which would create a much higher airflow than produced by the standard
one-speed fan used on the simulation. Higher air flow across the vehicle's A/C system can
increase system efficiency, reducing relative load demand on the engine. This suggests that the
simulation could be overpredicting A/C loading (and hence emissions) at the higher speed levels;
however, this effect does not appear in the overall LA92 results, a cycle which also contains
significant high speed operation. Unfortunately sufficient data does not exist over high speed
operation with representative air flow to make a more full assessment; further research will be
needed to address this issue.
From the fuel consumption and compressor data it was concluded for the purposes of this study
that despite observed emission differences between ATL and EPA, the vehicles were adequately
loaded at both sites to represent full-usage conditions. Therefore, no vehicles will be excluded
from the analysis and the emission results from the dataset will be used directly (i.e. with no
scaling) to develop the full-usage correction factors.
5 RUNNING CORRECTION FACTORS
The development of running correction factors requires analysis of what vehicle groupings merit
separate treatment. The factors considered were: vehicle class (i.e. cars vs. trucks), emission
standard, emitter class and technology (i.e. fuel injection). In addition, average cycle speed and
facility type were investigated. Simple factorial Analysis of Variance (ANOVA) was used for
initial screening of each factor, followed by a more detailed analysis to determine the appropriate
stratifications given sample size and technical merit. A discussion of this investigation follows
for each pollutant.
5.1 NOx
ANOVA was performed over the entire vehicle sample with NOx ratio as the dependent versus
speed, facility , technology, class and emitter class; significance results are shown in Table 5.
Using a significance level of 0.05 as a cutoff, the variables considered for further analysis were
speed, technology, class and emitter level. Each are discussed below:
Speed: As discussed in Section 3, the relative load placed on the engine by the air conditioner is
high at lower average speeds and low at higher speeds. As shown in Figure 2, the NOx A/C ratio
tracks this trend as well. As this trend is consistent across vehicles and a technical basis exists
for it, NOx correction factors will be expressed as a function of speed.
Class: A distinct difference in NOx A/C ratio between vehicles and trucks was observed. As
shown in Figures 5 and 6, the ratio for fuel consumption and NOx is lower for trucks,
M6. ACE.002 DRAFT Page 6
-------
particularly at the lower speed ranges. The basis for this is that in general the demand placed on
a more powerful truck engine by the A/C system is relatively small compared to a similar load
placed on a passenger car engine. In addition, lower cabin volumes on some trucks could reduce
A/C demand (although the recent proliferation of sport utilities and minivans would seem to
counteract this). Based on this observation, separate NOx correction factors will be developed
for LDV sand LDT's.
A second question is whether LDT classes should be subdivided. Graphical analysis of NOx
ratio with trucks broken down into the MOBILES definition of trucks (LDT1 up to 6000 GVW,
LDT2 up to 8500 GVW) do indicate a possible difference between the truck classes; LDTl's are
more similar to LDV's, while LDT2's are much lower. However, because the LDT2 results are
based on a sample of only four trucks, for sample robustness the truck classes will not be
subdivided. Since MOBILE6 will switch from the MOBILES truck definition to the more
subdivided certification truck classes (LDT1 through 4), the "LDV" equation will be applied to
LDV's and certification LDTl's, and the "LDT" equation will be applied to certification LDT2's,
3's and 4's (this will be applied as a general rule for HC and CO also).
Technology: Since all of the vehicles tested were equipped with a 3-way catalyst, the technology
breakdown in terms of MOBILE stratification relates to whether the vehicles was equipped with
throttle-body fuel injection (TBI) or ported fuel injection (PFI). Although ANOVA results show
significance, the sample size of TBI's is small and there is a strong interaction with vehicle class.
A technical basis for why NOx emission increase would be different between TBI and PFI is not
apparent. In the interest of sample robustness and concern with the potential error introduced by
developing separate factors for fuel injection based on limited data, NOx correction factors will
not be subdivided based on technology.
Emitter Class: Subdividing factors by emitter class is attractive because a) it is reasonable to
expect that vehicles with very high baseline emissions would see less relative increase due to
A/C operation, and b) averaging emissions from high emitters with normal emitters would
strongly impact overall sample average and ratio calculations for normal emitters. However,
there were only two NOx high emitters in the sample (one LDV and one LDT), and the behavior
of each was drastically different; the truck tracked the behavior of normal emitters, while the
vehicle showed little A/C impact across the speed range. Because of the small sample size and
disparity in response of the two high emitters, it was decided not to break out factors by emitter
class for NOx.
The proposed NOx running correction factor equations were developed by taking a quadratic
regression over the sample average ratio of each cycle versus speed for vehicles and trucks. This
curve form is favored because it fits data trends well without abnormal behavior at the low and
high ends of the speed range. As shown in Figure 6, this results in a curve which dips to a
minimum level around 45-55 mph before turning upward at the high end. The option of using a
straight average based on the high speed results above 40 mph was considered rather than using
the upward curve form. However, because both the NOx (for trucks) and fuel consumption data
M6. ACE.002 DRAFT Page 7
-------
suggests that directionally an upward trend it correct, the equation form will be applied as fitted.
The coefficients are shown in Table 6. Because the LDT curve surpasses the LDV curve in the
high speed range, the LDT equation will be set equal to the LDV curve at the point of
intersection (roughly 57 mph); occurrence of a higher LDT A/C ratio is judged to be an artifact of
curve extrapolation, and will be addressed in this manner as a general rule.
5.2 NMHC
ANOVA results for NMHC indicate significance to the 0.05 level for speed, technology, class
and emission standard (Table 5). Splitting by technology was ruled out, again for small sample
size and interaction with vehicle class. Graphical analysis of NMHC ratio by standard class
indicated that the observed difference was likely driven by a large disparity between average Tier
0 and Tier 1 ratios on a limited number of cycles, with no consistency as to which standard class
had the higher ratio. The majority of cycles showed no observable offset in ratios between the
standard classes; for this reason, it was decided not to pursue standard class as an additional
stratification.
For sample robustness, class will be divided into LDV and LDT in a similar manner as NOx.
Figure 7 shows NMHC ratio versus average cycle speed for normal emitters in both classes, fit
with a quadratic curve form. For both classes the data indicate higher ratios at the low and high
ends with a dip in the middle. For trucks, the NMHC ratio is less than 1.0 in the mid range. This
phenomena is consistent across many vehicles, likely the result of improved combustion due to
higher combustion temperatures and/or catalyst oxidation due to shifts in air fuel ratio (for cases
when enrichment is not introduced with A/C).
Although emitter category did not show significance to the 0.05 level, graphical analysis shows a
significant drop in NMHC ratio for high emitters versus normal emitters, based on a sample of
five high emitting vehicles (Figure 8). The technical basis for this observation is that it is more
likely that HC high emitters are operating with enrichment and/or very low catalyst efficiency
without air conditioning. There is less opportunity for emissions to increase significantly when
the air conditioning system is operating, since added enrichment or drops in conversion
efficiency with the A/C on won't have the same relative impact. Because of the observed
difference and technical basis behind the difference, high emitters will be model separately from
normal emitters for NMHC.
The proposed NMHC correction factors were developed by vehicle class and emitter class by
fitting a quadratic function to the sample averages by average speed (shown in Figures 7 and 8);
the proposed coefficients are shown in Table 6. The low end of the normal emitter LDT curve is
higher than the LDV curve, an artifact of extrapolation. The LDT model will therefore be set to
equal to the LDV model between 0 mph and the point of intersection (approximately 8 mph).
M6. ACE.002 DRAFT Page 8
-------
5.3 CO
ANOVA results for CO ratio do not indicate significance for any of the parameters of interest.
However, vehicle class becomes significant below the 0.05 level when the two MOBILES-based
LDT classes are split. Graphical analysis indicated a distinct trend for each class (LDV,
MOBILES LDT1 and LDT2). The LDT1 ratio is consistently less than the LDV ratio, while the
LDT2 is also generally lower but somewhat erratic. For sample robustness, a single LDT
equation was again developed. As shown in Figure 9, there is a marked difference in CO ratio
between the two classes.
Although emitter class was not significant in the ANOVA result, CO emission levels for high
emitters were so large and the CO ratio for these vehicles so much smaller than normals that
separate treatment was judged to be necessary. Two LDT high emitter and one LDV high
emitter were included in the sample. Because all had similar CO ratio behavior they were
combined into a single high emitter equation form (Figure 10). The proposed coefficients for CO
are found in Table 6.
6 START CORRECTION FACTORS
A primary change between MOBILE6 and MOBILES is the separation of FTP-based emissions
into start and running components. This change draws a distinction between start emissions and
emissions over start driving. Running emissions will represent not only emissions over warmed-
up operation, but the baseline emissions inherent in start driving; start emissions will be defined
as the incremental emission increase above this baseline which occurs during start driving. Total
emissions over start driving, therefore, will be comprised of the baseline running emissions plus
incremental start emissions. In terms of air conditioning correction factors, the running
correction factors developed in Section 5 will carry over to start driving to the extent that start
driving emissions are comprised of the baseline running component. The pertinent issue for start
air conditioning correction factors is therefore whether an A/C impact exists on the incremental
start component as well.
Data required to make this assessment based on the methodology used in the development of
base start and running emission factors9 were not gathered as part of the air conditioning test
program. An assessment was therefore made by analyzing the ratio for each pollutant over a cold
start ST01 run with the A/C on and off, shown for relevant stratifications in Table 7. The NOx
and fuel consumption results indicate there is an increase over start driving due to air
conditioning, but smaller (by 13% for LDV's, 7% for LDT's) than the impact over running
operation at the average speed of the ST02 cycle (20.2 mph). It is presumed from this result that
the NOx ratio observed over ST01 is attributable solely to the baseline running component, with
no A/C-related increase occurring on the start increment. The cold start NOx ratio is not
9 This methodology referred to is the separation of FTP emissions into Start and Running components as described in
MOBILE6 Report No. M6.STE.002, "The Determination of Hot Running Emissions from FTP Bag Emissions"
M6. ACE.002 DRAFT Page 9
-------
substantially lower than the corresponding running NOx ratio presumably because the difference
between cold start and warmed-up NOx emissions is relatively small (hence the contribution of
the running component to overall NOx start emissions is large). Based on this presumption, a
NOx correction factor for the incremental start component is not proposed for MOBILE6.
HC and CO results vary somewhat, particularly across emitter class. However, for the most part
the ratios are closer to one than for the running correction factors. Cold start HC and CO
emissions are dominated by emissions incurred by startup enrichment, and the drop in A/C ratios
for both pollutants between running and cold start is attributed to this. Under cold start
enrichment the air-fuel ratio will likely not change due to air conditioner operation and/or
increased engine load, so increased HC or CO emissions are not expected over the start
component. It is therefore proposed that no A/C correction factor be applied to the HC or CO
start components.
It is important to note that although air conditioning correction factors are not proposed for the
start components of any pollutant, air conditioning emissions over start driving will be estimated
by MOBILE6. Because the running correction factors are carried over to start driving, they will
be applied to the extent running emissions contribute to overall start emissions. This will be true
for all starts, including those following "intermediate" soak durations in which the engine and/or
catalyst are partially warmed up. For the most part, the contribution of running emissions (and
hence the influence of the running air conditioning correction factors) will become greater as the
soak duration shortens.
7 ACKNOWLEDGMENTS
Several individuals contributed considerable time and resources to gathering and analyzing the
data presented here. Carl Fulper, Carl Scarbro, Dave Boshenek and Manish Patel of OMS
designed and implemented the test program and developed the attendant dataset. Steve Baldus
and Kevin Cullen of GM made GM's environmental chamber available and coordinated testing
at that facility. Janet Kremer of OMS assisted in coordinating testing at GM and analyzed
correlation vehicle results.
M6.ACE.002 DRAFT Page 10
-------
Table 1 - Vehicle Sample
Site
ATL
ATL
ATL
ATL
ATL
ATL
ATL
ATL
ATL
ATL
ATL
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
BOTH
Year
91
91
91
91
91
93
93
93
93
90
93
92
96
92
92
94
96
92
96
92
96
90
90
94
96
94
94
94
92
94
90
92
96
94
96
90
96
Vehicle
CHEVROLET CAVALIER
FORD ECONOLINE 150
FORD ESCORT
PLYMOUTH VOYAGER
CHEVROLET ASTRO VAN
CHEVROLET CORSICA
CHEVROLET S10
TOYOTA CAMRY
HONDA ACCORD
NISSAN MAXIMA
EAGLE SUMMIT
TOYOTA COROLLA
HONDA ACCORD
SATURN SL
CHEVROLET BERETTA
FORD F150
FORD F150
MAZDA PROTEGE
CHEVROLET LUMINA
CHEVROLET CAVALIER
FORD RANGER
JEEP CHEROKEE
CHEVROLET SUBURBAN
CHRYSLER LHS
HONDA CIVIC
CHEVROLET ASTRO VAN
SATURN SL
HYUNDAI ELAN
CHEVROLET LUMINA VAN
FORD ESCORT
PLYMOUTH VOYAGER
CHEVROLET LUMINA
FORD EXPLORER
PONTIAC TRANSPORT
TOYOTA CAMRY
DODGE DYNASTY
PONTIAC GRAND PRIX
Class
LDV
LDT2
LDV
LDT1
LDT1
LDV
LDT1
LDV
LDV
LDV
LDV
LDV
LDV
LDV
LDV
LDT2
LDT2
LDV
LDV
LDV
LDT1
LDT1
LDT2
LDV
LDV
LDT1
LDV
LDV
LDT1
LDV
LDT1
LDV
LDT1
LDT1
LDV
LDV
LDV
Fuel
TBI
PFI
PFI
TBI
TBI
PFI
TBI
PFI
PFI
PFI
PFI
PFI
PFI
TBI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
TBI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
PFI
Std
TierO
TierO
TierO
TierO
TierO
TierO
TierO
TierO
TierO
TierO
TierO
TierO
Tierl
TierO
TierO
TierO
Tierl
TierO
Tierl
TierO
Tierl
TierO
TierO
TierO
Tierl
TierO
TierO
TierO
TierO
Tierl
TierO
TierO
Tierl
Tierl
Tierl
TierO
Tierl
Emit*
N/N/N
H/H/N
H/N/H
N/N/N
H/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
H/H/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
H/H/H
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
N/N/N
*HC/CO/NOx
M6.ACE.002 DRAFT
-------
Table 2 - Test Cycles
Cycle
NYCC
LOCL
ARTE
ARTC
ARTA
FWYG
FWYF
FWYE
FWYD
FWAC
FWHS
RAMP
AREA
LA92
ST01
Description
New York City Cycle
Local Roadways
Arterial Level Of Service E-F
Arterial LOS C-D
Arterial LOS A-B
Freeway LOS G
Freeway LOS F
Freeway LOS E
Freeway LOS D
Freeway LOS A-C
Freeway High Speed
Freeway Ramp
Non-Freeway Area-Wide
California "Unified" Cycle
Start Cycle
Distance
(miles)
1.18
7.24
1.62
3.35
5.06
1.42
2.28
3.85
5.95
8.54
10.70
2.56
7.25
9.81
1.39
Average
Speed
(mph)
7.1
12.9
11.6
19.2
24.7
13.1
18.6
30.5
52.9
59.7
63.2
34.7
19.4
24.6
20.2
Max
Speed
(mph)
21.1
38.3
39.9
49.5
58.9
35.7
49.9
63.0
70.6
73.1
74.7
60.2
52.3
67.2
41.0
Max
Accel
(mph/sec)
6.0
3.7
5.8
5.7
5.0
3.8
6.9
5.3
2.3
3.4
2.7
5.7
6.4
6.9
5.1
M6.ACE.002 DRAFT
-------
Table 3 - Correlation Vehicle Emission Results (g/mi)
NYCC
LA92
FWHS
ARTC
ATL
EPA
GM
ATL
EPA
GM
ATL
EPA
GM
ATL
EPA
GM
NMHC
Off
0.07
0.07
0.06
0.04
0.02
0.04
0.08
0.05
0.02
0.04
0.03
0.01
On
0.67
0.07
0.07
0.10
0.02
0.03
1.32
1.33
0.03
0.04
0.05
0.03
Ratio
9.39
1.03
1.25
2.76
0.94
0.61
15.72
24.23
1.75
1.11
1.48
2.83
CO
Off
1.36
0.98
0.60
0.39
0.15
0.54
2.82
4.63
0.82
1.70
1.41
0.33
On
4.34
3.32
7.71
7.92
0.53
1.83
100.04
112.24
2.41
1.41
3.00
2.99
Ratio
3.19
3.39
12.94
20.35
3.52
3.37
35.47
24.26
2.94
0.83
2.13
9.15
NOx
Off
0.03
0.11
0.11
0.38
0.38
0.67
0.25
0.22
0.30
0.11
0.13
0.19
On
0.33
0.25
0.28
0.21
0.51
1.04
0.03
0.00
0.62
0.16
0.28
0.37
Ratio
10.20
2.15
2.52
0.55
1.34
1.55
0.12
0.01
2.05
1.48
2.14
1.94
Carbon
Off
214.1
208.6
217.8
115.3
110.1
216.8
88.2
82.7
82.0
120.0
116.7
120.2
On
281.6
275.4
283.5
138.7
133.0
267.2
120.7
120.0
85.9
145.3
144.4
144.5
Ratio
1.31
1.32
1.30
1.20
1.21
1.23
1.37
1.45
1.05
1.21
1.24
1.20
Table 4 - Correlation Vehicle Compressor Behavior
NYCC
LA92
FWHS
ARTC
ATL
EPA
GM
ATL
EPA
GM
ATL
EPA
GM
ATL
EPA
GM
Compressor
Fraction
1.00
0.99
0.97
0.99
0.97
0.99
1.00
0.99
1.02
1.00
0.98
0.99
Average High
Pressure (lb/in2 )
311.5
306.4
320.9
334.2
339.4
312.1
361.1
367.3
264.8
310.7
315.3
310.8
Average Low
Pressure (lb/in2 )
49.7
58.1
44.5
48.2
57.9
40.3
43.7
50.3
34.3
46.4
54.7
39.0
M6.ACE.002 DRAFT
-------
Table 5 - ANOVA results for A/C Ratio (Significance by Factor)
Factor
Speed
Facility
Technology
Standard
Emitter
Class
Fuel
0.000
0.057
0.000
0.000
n/a
0.000
NOx
0.000
0.067
0.018
0.616
0.019
0.003
NMHC
0.004
0.104
0.023
0.041
0.076
0.000
CO
0.526
0.672
0.287
0.678
0.131
0.015*
* MOBS LDT1 & 2 split
Table 6 - Full-Usage A/C Emission Factor Equations
(Equations apply to Running operation unless otherwise indicated)
Emission Factor = Constant + a*(Speed) + b*(Speed2)
Pollutant/Class/Emitter
Fuel/LDV/All
Fuel/LDT/All
NOx/LDV/All
NOx/LDT/All
NMHC/LDV/Low
NMHC/LDT/Low
NMHC/All/High
CO/LDV/Low
CO/LDT/Low
CO/All/High
Constant
1.34
1.27
2.04
1.66
1.70
2.07
1.37
2.59
2.21
1.41
a
-0.006134
-0.004939
-0.032641
-0.022284
-0.027339
-0.076717
-0.024791
-0.026773
-0.067114
-0.017942
b
0.000053
0.000048
0.000299
0.000236
0.000575
0.001193
0.000286
0.006090
0.001058
0.000165
R2
0.92
0.78
0.80
0.68
0.44
0.26
0.58
0.25
0.33
0.54
Comment
CertLDV/LDTl*
CertLDT2/3/4*
LDT= LDV > 57 mph
LDT=LDV< 8 mph
*applies to HC,CO,NOx as well
M6.ACE.002 DRAFT
-------
Table 7 - Cold Start ST01 A/C Ratios
(average cycle speed = 20.2 mph)
Fuel
NOx
NMHC
CO
LDV
Normal
1.17
1.24
0.96
0.95
High
n/a
n/a
1.29
1.60
LDT
Normal
1.13
1.19
1.05
1.17
High
n/a
n/a
0.97
0.99
M6.ACE.002 DRAFT
-------
Figure 1 - Fuel Ratio by Cycle (sample average)
O
Q.
CO
O
O
"CD
1.30i
1.28
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10
\ \
\ \ \
\ \ \ \ \
Figure 2 - NOx Ratio by Cycle (sample average)
1.80i
o
1.70"
1.60"-
1.40"-
1.30'--
1.20'--
1.10"-
1.00
\ \ ^ \ \. \
\ \ \ \ \
M6.ACE.002 DRAFT
-------
Figure 3 - HC Ratio by Cycle (sample average)
1.60i
1.50"
1.40"
•° 1.30"-
O 1.20 + -
<
I 1.1
1.00 + -
•80
^ -^» <^ X> X> -«.. -«. X_ -«. X> Xl_ X> X>
% \ ^ % v^ \ \ % \ \ \ \ \
Figure 4 - CO Ratio by Cycle (sample average)
2.00-
1.80"
O
to 1.60 +
O
8 1-40+"
1.20'--
1.00
\ \ ^ \ \. \
\ \ \ \ \
M6.ACE.002 DRAFT
-------
Figure 5 - Fuel Ratio by Vehicle Class
1.35
1.30'-
1.25--
1.20--
O
o
'
o
O
"CD
.=5 1.15"
1.10
Class
D LOT
LDV
10 20 30 40 50 60 70
Average Cycle Speed (mph)
Figure 6 - NOx Ratio by Vehicle Class
O
LDV
10 20 30 40 50 60 70
Average Cycle Speed (mph)
M6.ACE.002 DRAFT
-------
Figure 7 - Normal Emitter NMHC Ratio by Vehicle Class
20 30 40 50
Average Cycle Speed (mph)
60
Class
LOT
LDV
70
Figure 8 - High Emitter NMHC Ratio by Vehicle Class
10 20 30 40 50 60
Average Cycle Speed (mph)
M6.ACE.002 DRAFT
-------
Figure 9 - Normal Emitter CO Ratio by Vehicle Class
4.
10
20 30 40 50
Average Cycle Speed
60
Class
LOT
LDV
70
Figure 10 - High Emitter CO Ratio for All Classes
10 20 30 40 50
Average Cycle Speed (mph)
M6.ACE.002 DRAFT
-------
M6.ACE.002 DRAFT
------- |