E PA-420-D-97-005
- Draft -
Determination of Start Emissions
. as a Function of Mileage and Soak Time
for 1981-1993 Model Year Light-Duty Vehicles
Report Number M6.STE.003
October, 1997
Ed Glover
Penny Carey
Phil Enns
David J. Brzezinski
U.S.EPA Assessment and Modeling Division
1.0 INTRODUCTION
MOBILE6 will allocate vehicle exhaust emissions to either those associated with engine start
(start emissions) or those associated with travel (running emissions). This split allows the separate
characterization of start and running emissions for correction factors such as fuel effects and ambient
temperature It also allows a more precise weighting of these two aspects of exhaust emissions for
particular situations such as morning commute, parking lots and freeways This document describes
the methodology used to calculate start emissions as a function of mileage and soak time for use in
MOBILE6. The results for model year 1981-1993 light-duty cars and light-duty trucks are presented.
The deterioration of running emissions will be addressed in a separate document (Report Number
M6.STE.004)
Section 2 describes the FTP data sources and the model year and technology groups which
are used. Section 3 describes the methodology and models for determining start emissions. It is
divided into three sub-sections The first sub-section describes the FTP cycle, the Hot505 cycle, and
defines the basic unit of start emissions. The second sub-section describes the analysis of start
emissions deterioration with mileage. The third sub-section describes the methodology used to
predict start emissions as a function of soak time Section 4 illustrates how start emissions will be
estimated in MOBILE6 as a function of both deterioration and soak time
2.0 DATA SOURCES USED
The datasets used to determine m-use deterioration are all based on FTP testing No IM240
data or data collected by a state I/M program were used. Three data sources were used: 1) the test
-.results from the EPA laboratory in Ann Arbor, Michigan, 2) the data received from AAMA

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(Amencan Automobile Manufacturers Association) based on testing conducted in Michigan and
Arizona, and 3) the API (American Petroleum Institute) data collected in Arizona. The model years
in the dataset range from 1981 through 1993, and contain both cars and trucks Table 1 gives a
breakdown by vehicle type, model year, and technology for the three datasets combined
In general, most of the 1990+ model year vehicle data were supplied by AAMA, and most
of the pre-1990 data were supplied by the EPA laboratory testing. The API sample is a relatively
small sample (99 cars and trucks) Its chief appeal is that the vehicles all have generally higher
mileage readings that the rest of the sample (all over 100,000 miles) The other general trend in the
data is toward PFI technology, and away from the others. This is seen in the 1990+ vehicles which
are predominately PFI with some TBI still present The 1981 - 1989 model years start with a high
percentage of carbureted and some open loop, but end with mostly TBI and PFI technology
Although not explicitly shown in the tables, new catalyst technology was phased slowly into the fleet
starting in the mid 1980's.
For analysis, the cars and trucks were placed into the model year/technology groups shown
below
MY Group / Technology Type
1990-93 PFI
1990-93 TBI
1986-89 FI
1986-89 CL Carb
1983-85 FI
1983-85 CL Carb
1981-82 FI
1981-82 CL Carb
1981+OPLP
The technology groups are closed-loop ported fuel injection (PFI), closed-loop throttle body injection
(TBI), closed-loop carbureted (CARB), and open loop (OPLP). FI refers to a combination of PFI
and TBI. These model year/technology grouping boundaries were selected in conjunction with the
FACA In-Use Deterioration Workgroup on the basis of changes in emission standards or the
development/refinement of new fuel metering or catalyst technologies It is assumed that as of 1990,
carbureted technology had negligible market share, and will not be modeled. Because of the
relatively large amount of 1990-93 fuel injected data, the category was split into PFI technology and
TBI technology for both cars and trucks. This produces separate deterioration functions based on
this fuel delivery technology and allows the modeling of the future penetration of PFI technology
into the in-use fleet
3.0 DETERMINATION OF START EMISSIONS

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3.1 Background
3.1.1	Overview of the Federal Test Procedure (FTP)
The Federal Test Procedure (FTP) is a test cycle which is used to certify new vehicles to
emission performance standards (see 40 CFR Part 86, Subpart B, Section 86.144). The FTP consists
of a cold start segment (Bag 1), a hot stabilized segment (Bag 2), and a hot start segment (Bag 3)
Initially, the vehicle is stored for a minimum of 12 hours before testing to simulate a 12 hour
overnight soak period. The vehicle is then driven over the cold start segment, which lasts 505
seconds over a length of 3 59 miles, and the emissions collected as Bag 1 Bag 2 emissions are then
immediately collected from the hot stabilized segment, which lasts 867 seconds over a length of 3.91
miles After a 10 minute soak, the 505 seconds of the start segment is then repeated and the
emissions collected as Bag 3.
The FTP composite emission rate is a weighted combination of the three measured bags to
represent two trips The first trip is a cold start after a 12 hour soak, and the other is a hot start after
a 10 minute soak Each trip is a "LA4" cycle, which is a combination of the 505 cycle (either Bag
1 or Bag 3) and the Bag 2 cycle. In a typical FTP test, the Bag 2 is only measured once and the
results are used for both trips Since the 505 cycle is 3 59 miles long and the Bag 2 cycle is 3.91
miles long, each LA4 trip is 7.5 miles long. The cold start trip is weighted at 43% and the hot start
trip weighted 57% If the cold start trip is 43% of the driving, then the vehicle miles traveled (VMT)
in Bag 1 (containing the cold start) is
FTP Bag 1 VMT Weighting = 43% * ( 3 59 miles / 7 5 miles ) = 0 206
The hot start trip is 57% of driving, and the VMT weighting for Bag 3 (containing the hot start) is:
FTP Bag 3 VMT Weighting = 57% * ( 3 59 miles / 7.5 miles) = 0.273
The remaining VMT is from stabilized driving, represented by Bag 2. Since Bag 2 is used for both
the cold start and hot start trips, it uses VMT weighting from both.
FTP Bag 2 VMT Weighting = ( 43% + 57% ) * ( 3 91 miles / 7.5 miles ) = 0.521
The standard VMT weighting of the bags reported in grams per mile for the full FTP are:
FTP = (Bag 1 * 0.206) + (Bag 2 * 0.521) + (Bag 3 * 0.273)
where the fractions represent the amount of vehicle miles traveled within the three modes during the
FTP trip in grams per mile (g/mi).
3.1.2	Overview of the Hot Running 505 and Its Use

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The FTP testing method outlined above does not allow the precise separation of start and
running emissions, since Bags 1 and 3 contain both start and running emissions Bag 2 of the FTP
does not contain an engine start; however, the driving cycle used in the second bag is significantly
different from the cycle used for Bags 1 and 3 Thus, to estimate the amount of FTP emissions that
can be allocated to engine start, the concept of the Hot Running 505 (HR505) is needed.
The HR505 is an extra 505 cycle performed immediately following bag 3 of the FTP It uses
an identical driving cycle as the first and third bags of the FTP, but does not include an engine start
For more information, refer to the document "The Determination of Hot Running Emissions from
FTP Bag Emissions", report number M6 STE.002 With a HR505 emission result, it is possible to
compare the results obtained from the HR505 to the results from Bags 1 and 3 of the FTP to
determine the portions of Bags 1 and 3 attributable to start emissions following a 12 hour soak and
start emissions following a 10 minute soak, respectively
Since the HR505 has not historically been included in FTP test programs, a method of
estimating the HR505 was developed, as described in report M6 STE 002. Briefly, HR505
emissions were measured from a sample of 77 vehicles tested under EPA contract The results from
this vehicle sample were used to develop a correlation between the HR505 and FTP bag data This
correlation was then used to estimate HR505 results for the FTP dataset used for this analysis.
3.1.3 Basic Start Emission Rate
For MOBILE6, the basic unit of engine start emissions is defined as a start after a 12 hour
soak. The units for engine start emissions will be grams, instead of grams per mile, since start
emissions will not be allocated by vehicle miles traveled. The engine start basic emission rate can
be determined by subtracting the HR505 emission rate from the Bag 1 emission rate (in grams per
mile) using the nominal distance traveled in the 505 driving cycle.
Basic Start Emission Rate (grams) = [Bag l(g/mi) - HR505(g/mi)] * 3 59 miles
For illustration purposes, the average basic start emission rates (in grams) after a 12 hour
soak were calculated for each model year and are shown in Tables 2a and 2b
Start emissions after a 10 minute soak can also be estimated from the Bag 3 and HR505
emission rates, analogous to the basic start emission rate:
Start Emissions after 10 minute soak (grams) = [Bag 3(g/mi) - HR505(g/mi)] * 3 59 miles
The average start emissions after a 10 minute soak are also shown in Table 2a and 2b for each
model year

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3.2	Basic Start Deterioration with Mileage
This section describes the methodology used to estimate start emission deterioration, and
presents the basic deterioration rates versus mileage The basic start (1 e , following a 12 hour soak)
deterioration rates were obtained from simple linear regression of the Basic Start Emission Rate data
(expressed as grams) versus mileage. The results are shown in Tables 3a, 3b, and 3c. Table 3a
includes the deterioration rates for the fuel injected cars and Table 3b shows the rates for the fuel
injected trucks. Table 3c shows the deterioration rates for the closed-loop carbureted and open-loop
cars and trucks.
Separate deterioration rates were calculated for both cars and trucks, for each of the three
pollutants, and for each model year/technology group. The exception is the 1981-82 fuel injected
and closed-loop carbureted truck categories, which had zero data Because of the lack of 1981-82
FI and CL Carb truck data, the deterioration functions for the corresponding 1981 -82 car categories
were used. The effect of this substitution in the MOBILE6 model should be negligible due to the
scarcity of older model year fuel injected trucks in the in-use fleet.
Selected results from Table 3a (cars only) are also shown graphically in Figures 1 through
3 for HC, CO, and NOx for each model year/ technology group. For HC, the results are generally
as expected with the new model years having lower start emission levels and deterioration rates than
the older model years. However, comparing PFI and TBI for the 1990-93 cars shows TBI cars
having slightly lower emission levels than PFI cars. This is somewhat of an anomaly since it is
believed that PFI is a superior technology to TBI. However, both regressions were generally
statistically significant at least at a 90% confidence level, and further analysis of the sample using
scatter plots (not shown) revealed that the differences were not the result of outliers greatly
influencing the sample Thus, the 1990-93 TBI vehicles will be projected to have slightly lower HC
start emissions than the corresponding PFI vehicles.
Again for CO, the 1990-93 TBI category is slightly lower than the PFI category because of
a lower ZML. Also, in this case, the 1986-89 model year group has slightly lower CO emissions
than the 1990-93 PFI group. However, in this case, the deterioration rate is not statistically
significant for the TBI or 1986-89 model year groups Finally, the 1981-82 group is considerably
higher than the other two groups with CO emissions at the 100,000 mile level almost twice as high
as the other model year groups This is not unexpected since much of the 1981-82 fuel injection
technology was in early stages of development.
For NOx, the emission levels and deterioration rates for all model year groups are generally
the same The principal exception is the 1990-93 TBI group. For the 1990-93 TBI group, the
deterioration rate is similar to the others, but the intercept is considerably higher.
3.3	Start Emissions Versus Soak Time

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Start emissions will be a function of soak time so that MOBILE6 will be able to account for
the entire distribution of soak times observed in the fleet This ranges from a minimum soak time
of zero minutes up to a 12 hour soak period (720 minutes) Soak periods exceeding 12 hours will
be assumed to be the same as for a 12 hour soak.
To develop the relationship between start emissions and soak time, the FTP database was
used only to determine the engine start emissions after a 10 minute soak and a 12 hour (720 minute)
soak (these are the only data points available). To predict start emissions for the entire range of soak
duration, a model was developed from the two FTP points, and from testing done by California of
the effect of soak time on engine start emissions (see CARB report "Methodology for Calculating
and Redefining Cold and Hot Start Emissions")
The model which was developed uses the FTP start emission data from the two FTP soak
times to adjust the curves presented in the California report The start emission data points at 10
minutes and 720 minutes are derived from the FTP dataset described earlier and are a function of
pollutant, technology, model year group, and mileage. The California interpolation curves
(California Soak Function) is a function of pollutant and catalyst type.
Mathematically, the start emissions of a given pollutant (in grams) as a function of soak time
is shown as:
Start Emissions (@ soak time) = Basic Start Emissions (@ 12 hour soak) * Soak Function
where the Soak Function is a multiplicative factor used to calculate start emissions for other soak
times. The Soak Function is the grams for the soak time of interest divided by the grams for a soak
time of 12 hours. At a 12 hour (720 minute) soak time, the Soak Function is equal to 1.
Mathematically, the Soak Function is defined as.
Soak Function = California Soak Function * [Ratio+(l-Ratio)*((SoakTime-10)/(720-10))]
where
California Soak Function. The values developed by the California Air Resources Board to adjust
the start emissions for soak times other than 12 hours This is a function of soak time in minutes.
The coefficients for catalyst vehicles, non-catalyst vehicles, and electrically heated catalyst vehicles
are given in Table 4 The coefficients for catalyst-equipped vehicles are for the model
year/technology groups examined in this report For example, for HC on a catalyst equipped vehicle
at a soak time of 100 minutes, the value is
0 57130 + 0 00072*100 + (-1.76E-07)*(100)2 = 0 64154

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Ratio This parameter is calculated by dividing the EPA ratio of start emissions at 10 minutes to start
emissions at 12 hours by the California Soak Function at 10 minutes. Mathematically, it is given by:
Ratio = (Start @10 minutes / Start @720 minutes) / California Soak Function @10 minutes
The numerator in the above equation (Start @10 minutes/ Start @720 minutes) was developed from
FTP data using the equations in Sections 3.1.3, and dividing the Start @10 minutes by the Start @
720 minutes. One value for each pollutant was developed that included all technologies and vehicle
types. These values, used in the numerator of the equation, are HC= 0 160, CO = 0.112, and NOx
= 0 204. The California Soak Function is the value obtained from the coefficients in Table 4 at a
10 minute soak point. The California Soak Function values at a 10 minute soak point for catalyst-
equipped vehicles, used in the denominator of the equation, are: HC=0.1209, CO=0 1147, and
NOx=0.3937. Therefore, the Ratios obtained are: HC=1 3234, CO=0.9718, and NOx=0 5182.
SoakTime: The time duration in minutes of the soak which is to be calculated (range zero minutes
to 720 minutes)
The operation of the multiplicative Soak Function is illustrated in Figures 4,5, and 6 for HC,
CO, and NOx respectively The Y-axis is the Soak Function (a unitless ratio) and the X-axis is the
soak time in minutes The California Soak Function is also shown for comparison.
For HC and NOx, the difference between the MOBILE6 soak function and the California
soak function will be moderate for soak times between 30 minutes and 600 minutes For CO, the
two soak functions are very similar.
4.0 START EMISSION RESULTS
Start emissions are both a function of vehicle deterioration represented by mileage, and
soak time. In previous sections the results were shown separately. In this section, examples of
the results are shown with both effects combined. For example, Figures 7 through 9 show the
HC, CO, and NOx start emissions as a function of soak time for three odometer levels (0,50,000,
and 100,000 miles) of 1990-93 PFI cars. For all three pollutants, the figures show low
deterioration rates as mileage is increased at short soak times, and larger but constant
deterioration rates at soak times after 120 minutes.
Shown below for illustration purposes is a sample calculation of start emissions. It
illustrates the equations shown in Section 3.
Example: Calculate HC start emissions at a soak time of 90 minutes for a 1991 model year
PFI-equipped car with 50,000 miles.

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Start Emissions (@90min) = Basic Start Emissions (@12hr) * Soak Function
From Table 3a:
Basic Start Emissions = 2.0163 + (0.0074/1000 miles) * 50,000 miles = 2.3863g
Soak Function = California Soak Funct * [Ratio+(l-Ratio)*((SoakTime-10)/(720-10))]
From Table 4, using the coefficients for catalyst-equipped vehicles:
California Soak Funct = 0 57130 + (0 00072)*(90) + (-1.76E-07)*(90)2 = 0 63467
Ratio = (Start@10min / Start@12hr) / California Soak Funct@10min
= 1 3234 for HC as given in Section 3 3
SoakTime - 90 minutes
Soak Function = 0 63467 * [1.3234 + (1-1 3234) * ((90-10) / (720-10))] = 0.81680
Start Emissions(@90min) = 2.3863 * 0.81680 = 1.9491 g HC

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Table 1
Distribution of Vehicles by Model Year and Technology*

Cars
Cars
Cars
Cars
Cars

Trucks
Trucks
Trucks
Trucks
Trucks
MYR
OPLP
CL
TBI
PFI
ALL
MYR
OPLP
CL
TBI
PFI
ALL


CARB





CARB



81
367
657
15
29
1068
81
124



124
82
71
71
74
8
224
82
45



45
83
63
57
127
62
309
83
8
3


11
84
5
30
46
35
116
84
26
22

1
49
85
24
74
56
66
220
85
33
30
13
6
82
86
7
34
60
92
193
86
14
9
23
41
87
87
1
17
76
106
200
87


6
4
10
88

15
69
113
197
88




0
89

22
38
103
163
89




0
90


160
250
410
90


144
1
145
91


91
426
517
91


141
144
285
92


57
347
404
92


92
92
184
93


29
366
395
93


90
93
183
ALL
538
977
898
2003
4416
ALL
250
64
509
382
1205
No entry indicates no data available for that model year/technology type
in the FTP dataset used for this analysis

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Table 2a
Mean Start and FTP Emission Levels by Model Year for Light-Duty Cars*
Basic start (after 12 hour soak)


grams

MYR
HC
CO
NOx
81
4 002
46.419
1.373
82
2.445
36.378
1 237
83
2.399
26.112
1.264
84
2.950
34 827
1.190
85
3 468
30.353
1.204
86
2.526
26.639
1 432
87
2.712
20 030
1.376
88
2.831
19.716
1 419
89
2.254
18.610
1 434
90
2 169
18.677
1.930
91
2.183
19.494
1.443
92
2.271
18 878
1 645
93
2.312
21.030
1 801
Start (after 10 min soak)	Composite FTP


grams



grams/mile

MYR
HC
CO
NOx
MYR
HC
CO
NOx
81
0.610
5.115
0.041
81
0 706
9.667
0.897
82
0.373
4.843
-0.045
82
0 789
8318
0 872
83
0.400
3 827
0 150
83
0.431
5.073
0.806
84
0 513
3.418
0 047
84
0 756
9.968
0 893
85
0.506
4.737
0.095
85
0.533
6.935
0.770
86
0.298
2.082
0.241
86
0 926
10 432
0 713
87
0 597
2 104
0 170
87
0.656
8.366
0.790
88
0 406
1.147
0.223
88
0 406
4.574
0 668
89
0.379
2.524
0.216
89
0311
3 911
0.652
90
0.332
2219
0611
90
0.274
3.614
0.633
91
0 275
2.132
0.530
91
0 237
3.145
0 525
92
0 304
2.595
0.485
92
0.267
4 328
0.508
93
0.310
2 564
0.392
93
0 225
2.551
0 466
* In some isolated instances, a negative number for a start emissions estimate was obtained. This is possible when the simulated
HR505 value is greater than the Bag 1 or Bag 2 value from the FTP.

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Table 2b
Mean Start and FTP Emission Levels by Model Year for Light-DutyTrucks*
Basic start (after 12 hour soak)	Start (after 10 min soak)	Composite FTP


grams



grams



grams/mile

MYR
HC
CO
NOx
MYR
HC
CO
NOx
MYR
HC
CO
NOx
81
7.342
107 501
1 055
81
1.212
14.211
0 385
81
1 275
18.158
1 752
82
7 909
116 584
-0.119
82
1 489
14.189
0.006
82
1.732
16.774
1.732
83
6 537
104.817
0.796
83
1 577
18.657
-0.209
83
1.361
13 226
1.436
84
5 219
95.893
0.299
84
1 098
20.057
0.004
84
0 802
10.633
1 405
85
4 766
84 621
0 457
85
0.854
7 742
0 102
85
1 281
14.465
1.388
86
3 752
41.196
0.729
86
0 607
2 148
0.128
86
0.823
8.789
1.057
87
3.352
26.635
1 266
87
0 566
1.433
0.017
87
0 401
4 610
0 605
88



88



88



89



89



89



90
4 705
45 331
4 683
90
0.930
7 037
0 765
90
0 800
9 510
0 885
91
3 521
41 128
2 761
91
0 878
7.129
0.519
91



92
3 656
41 446
3 054
92
0 654
5.746
0 656
92



93
3 644
40.557
2.736
93
0.589
4.634 •
- 0.676
93
0 420
5 363
0 847
* No FTP data are available for 1988 and 1989 model year light-duty trucks.
In some isolated instances, a negative number for a start emissions estimate was obtained This is possible when the simulated
HR505 value is greater than the Bag 1 or Bag 2 value from the FTP.

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Table 3a
Basic Start Deterioration with Mileage for Light-Duty FI Cars*



Sample
Coefficients
ZML Confidence Level
Det Confidence Level
Significance
Pollutant
MY Group
Tech
Size
ZML
Det
Lower
Upper
Lower
Upper
ZML
Det
HC
1990-93
PFI
1389
2 016
0 0074
1 885
2 148
0 0042
0 0105
0 000
0 000
HC
1990-93
TBI
337
1 835
0 0041
1 635
2 035
0 0000
0 00856
0 000
0 074
HC
1986-89
FI
657
2 145
0 0067
1 856
2 433
0 0029
0 0104
0 000
0 001
HC
1983-85
FI
392
2 476
00119
1 500
3 451
0 0000
0 0299
0 000
0 191
HC
1981-82
FI
126
2 435
0 0133
1 859
3 011
0 0022
0 0244
0 000
0 019



Sample
Coefficients
ZML Confidence Level
Det Confidence Level
Significance
Pollutant
MY Group
Tech
Size
ZML
Det
Lower
Upper
Lower
Upper
ZML
Det
CO
1990-93
PFI
1389
17 987
0 0572
16 292
19 682
0 0169
0 0975
0 000
0 005
CO
1990-93
TBI
337
15 649
0 0376
9 360
21 938
0 0000
0 1782
0 000
0 599
CO
1986-89
FI
657
19 443
0 0071
15 713
23 174
0 0000
0 0553
0 000
0 772
CO
1983-85
FI
392
23 378
0 0720
16 360
30 396
0 0000
0 201
0 000
0 274
CO
1981-82
FI
126
23 311
0 3489
10 345
36 275
0 0989
0 5989
0 000
0 007



Sample
Coefficients
ZML Confidence Level
Det Confidence Level
Significance
Pollutant
MY Group
Tech
Size
ZML
Det
Lower
Upper
Lower
Upper
ZML
Det
NOx
1990-93
PFI
1389
1 484
0 0020
1 381
1 588
0 0000
0 00448
0 000
0 107
NOx
1990-93
TBI
337
2 142
0 0020
1 854
2 431
0 0000
0 0085
0 000
0 541
NOx
1986-89
FI
657
1 268
0 0023
1 090
1 445
0 0000
0 0046
0 000
0 050
NOx
1983-85
FI
392
1 333
0 0028
1 119
1 545
0 0000
0 00676
0 000
0 155
NOx
1981-82
FI
126
1 679
0 0000
1 229
2 129
0 0000
0 0021
0 000
0 134
* The basic unit of engine start emissions is defined as a start after a 12 hour soak
ZML and Det are the regression coefficients for the zero mile level (intercept) and the deterioration rate (slope) per one thousand miles, respectively
The confidence levels shown are the upper and lower 95% confidence intervals Significance values less than 0 05 are considered statistically significant at
the 95% confidence level

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Table 3b
Basic Start Deterioration with Mileage for Light-Duty FI Trucks*



Sample
Coefficients
ZML Confidence Level
Det Confidence Level
Significance
Pollutant
MY Group
Tech
Size
ZML
Det
Lower
Upper
Lower
Upper
ZML
Det
HC
1990-93
PFI
330
2 709
0 0000
2 482
3 308
0 0000
0 00432
0 000
0 334
HC
1990-93
TBI
467
4 112
0 0118
3 809
4 416
0 0046
0 0188
0 000
0 001
HC
1986-89
FI
74
2 312
0 0221
1 330
3 295
0 0052
0 0369
0 000
0 010
HC
1983-85
FI
20
0 834
0 0387
0 000
6 827
0 0000
0 104
0 773
0 227
HC
1981-82
FI
**
2 435
0 0133
1 859
3 011
0 0022
0 0244
0 000
0 019



Sample
Coefficients
ZML Confidence Level
Det Confidence Level
Significance
Pollutant
MY Group
Tech
Size
ZML
Det
Lower
Upper
Lower
Upper
ZML
Det
CO
1990-93
PFI
330
32 237
0 0223
26 950
37 524
0 0000
0 1308
0 000
0 687
CO
1990-93
TBI
467
42 204
0 1490
37 695
46 712
0 0438
0 2536
0 000
0 006
CO
1986-89
FI
74
16 314
0 2145
2 427
30 200
0 0000
0 439
0 022
0 061
CO
1983-85
FI
20
4 421
0 2844
0 000
57 334
0 0000
0 858
0 863
0 311
CO
1981-82
FI
**
23 311
0 3489
10 345
36 275
0 0989
0 5989
0 000
0 007



Sample
Coefficients
ZML Confidence Level
Det Confidence Level
Significance
Pollutant
MY Group
Tech
Size
ZML
Det
Lower
Upper
Lower
Upper
ZML
Det
NOx
1990-93
PFI
330
1 411
0 0000
1 366
1 958
0 0000
0 0004
0 000
0 067
NOx
1990-93
TBI
467
4 293
0 0033
3 836
4 750
0 0000
0 0139
0 000
0 548
NOx
1986-89
FI
74
1 245
0 0000
0 800
1 691
0 0000
0 00288
0 000
0 235
NOx
1983-85
FI
20
1 754
0 0000
0 000
3 529
0 0000
0 0060
0 052
0 166
NOx
1981-82
FI
**
1 679
0 0000
1 229
2 129
0 0000
0 0021
0 000
0 134
* The basic unit of engine start emissions is defined as a start after a 12 hour soak ZML and Det are the regression coefficients for the zero mile level
(intercept) and the deterioration rate (slope) per one thousand miles, respectively The confidence levels shown are the upper and lower 95% confidence
intervals Significance values less than 0 05 are considered statistically significant at the 95% confidence level
** Due to lack of data for the 1981 -82 FI truck category, the deterioration functions for the 1981 -82 Fl cars were used to represent this category

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Table 3c
Basic Start Deterioration with Mileage for Light-Duty Open Loop and Closed Loop Carbureted Vehicles*
Cars	Trucks
Pollutant
MY Group
Tech
Number
ZML
Det
Pollutant
MY Group
Tech
Number
ZML
Det
HC
1990-93
CL Carb



HC
1990-93
CL Carb



HC
1986-89
CL Carb
88
1 532
0 017
HC
1986-89
CL Carb
9
6 480
0 000
HC
1983-85
CL Carb
161
0 486
0 070
HC
1983-85
CL Carb
54
1 338
0 072
HC
1981-82
CL Carb
728
2 825
0 046
HC
1981-82
CL Carb
**
2 825
0 046
HC
1981 +
OPLP
538
1 194
0 044
HC
1981 +
OPLP
250
6 469
0 008
Pollutant
MY Group
Tech
Number
ZML
Det
Pollutant
MY Group
Tech
Number
ZML
Det
CO
1990-93
CL Carb



CO
1990-93
CL Carb



CO
1986-89
CL Carb
88
24 300
0 089
CO
1986-89
CL Carb
9
4 111
1 415
CO
1983-85
CL Carb
161
19 495
0 496
CO
1983-85
CL Carb
54
56 604
0 830
CO
1981-82
CL Carb
728
30 953
0 483
CO
1981-82
CL Carb
**
30 953
0 483
CO
1981 +
OPLP
536
19 350
0 582
CO
1981 +
OPLP
250
96 418
0 231
Pollutant
MY Group
Tech
Number
ZML
Det
Pollutant
MY Group
Tech
Number
ZML
Det
NOx
1990-93
CL Carb



NOx
1990-93
CL Carb



NOx
1986-89
CL Carb
88
1 377
0 000
NOx
1986-89
CL Carb
9
0 700
0 000
NOx
1983-85
CL Carb
161
1 189
0 000
NOx
1983-85
CL Carb
54
0 700
0 000
NOx
1981-82
CL Carb
728
1 684
0 000
NOx
1981-82
CL Carb
**
1 684
0 000
NOx
1981 +
OPLP
538
0 704
0 000
NOx
1981 +
OPLP
250
0 753
0 000
* The basic unit of engine start emissions is defined as a start after a 12 hour soak ZML and Det are the regression coefficients for the zero mile level
(intercept) and the deterioration rate (slope) per one thousand miles, respectively The confidence levels shown are the upper and lower 95% confidence
intervals Significance values less than 0 05 are considered statistically significant at the 95% confidence level
** Due to lack of data for the 1981-82 CL Carb truck category, the deterioration functions for the 1981-82 CL Carb cars were used to represent this category

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Table 4
Coefficients for Adjusting Engine Start Emissions for Soak Time
(from "Methodology for Calculating and Redefining Cold and Hot Start Emissions", CARB)
Non-Catalyst Vehicles

HC Curve 1
HC Curve 2
CO Curve 1
CO Curve 2
NOX Curve
1
NOX Curve
2
Constant
0 38067
0 43628
0 43803
-0 08541
1 31568
2 48061
minutes
-0 00163
0 00078
-0 00998
0 00303
0 02752
-0 00018
minutes2
6 64E-05
0
7 01E-05
-2 11E-06
-0 00015
-2 6E-06
domain(min)
0-52
53-720
0-119
120-720
0-119
120-720

Catalyst Equipped Vehicles

HC Curve 1
HC Curve 2
CO Curve 1
CO Curve 2
NOx Curve 1
NOx Curve 2
Constant
0
0 57130
0
0 70641
0 11796
1 12983
minutes
0 01272
0 00072
0 01195
0 00033
0 02967
2 21 E-05
minutes2
-6 30E-05
-1 76E-07
-4 76E-05
1 00E-07
-0 00021
-3 04E-07
domain(min)
0-89
90-720
0-116
117-720
0-61
62-720

Electrically Heated Catalyst Equipped Vehicles

HC Curve 1
HC Curve 2
CO Curve 1
CO Curve 2
NOx Curve I
NOx Curve 2
Constant (a)
0
0 50641
0
0 44733
1 05017
1 37178
minutes (b)
0 00561
0 00069
0 00707
0 00162
0 00362
0 00027
minutes2 (c)
-5 09E-06
0
-1 33E-05
-1 18E-06
-5 57E-06
-1 09E-06
domain(min)
0-117
118-720
0-107
108-720
0-113
114-720
California Soak Function = a + b * minutes + c * minutes2
(where minutes is time since last engine operation (1 e , soak time))
The Soak Function is the grams per soak time 1 divided by the grams per overnight soak (720 minutes or 12 hours)

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Figure 1
HC Basic Start Emissions for Fl Cars by Model Year Group
Mileage (in thousands)
—~—90-93 PFI
-¦—90-93 TBI
_o_ 86-89 Fl
83-85 Fl
, 81-87 Fl

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Figure 2
CO Basic Start Emissions for Fl Cars by Model Year Group
Mileage (in thousands)
—~—90-93 PFI
90-93 TBI
86-89 Fl
	±	83-85 Fl
81-82 Fl

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Figure 3
NOx Basic Start Emissions for Fl Cars by Model Year Group
Mileage (in thousands)
—~—90-93 PFI
-¦—90-93 TBI
86-89 Fl
83-85 Fl
81-82 Fl

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1.00
0 90
0 80
0 70
0 60
0 50
0 40
0 30
0 20
0 10
0 00
Figure 4
HC Soak Function vs Soak Time for 1981+ Vehicles
I0 180 240 300 360 420 480 540 600 660 72
Soak Time (in Minutes)

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1 00
0 90
0 80
0 70
0 60
0 50
0 40
0.30
0 20
0 10
0 00
Figure 5
CO Soak Function vs Soak Time for 1981+ Vehicles
60 120 180 240 300 360 420 480
Soak Time (in Minutes)
540 600 660 72

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Figure 6
NOx Soak Function vs Soak Time for 1981+ Vehicles
60 120 180 240 300 360 420 480
Soak Time (in Minutes)
540 600 660 720
California
NOx Soak Func

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Figure 7
HC Start Emissions vs Soak Time for 1990-93 PFI Cars
Soak Time (in Minutes)
0 miles
	50 miles
	100 miles

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25 0
Figure 8
CO Start Emissions vs Soak Time for 1990-93 PFI Cars
60 120 180 240 300 360 420 480
Soak Time (in Minutes)
540
.0 miles
.50 miles
. 100 miles
600 660
720

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2 00
1 80
1 60
1 40
1 20
1 00
0 80
0 60
0 40
0 20
0 00
Figure 9
NOx Start Emissions vs Soak Time for 1990-93 PFI Cars
180 240 300 360 420 480 540 600 660
Soak Time (in Minutes)

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