EPA-AA-TEB-EF-8 6-01
The Effect of Fuel Volatility
on Controlled and Uncontrolled
Evaporative Emissions
by
Thomas L. Darlington
and
Celia Shin
Nay 1986
Test and Evaluation Branch
Emission Control Technology Division
Office of Air and Radiation
U.S. Environmental Protection Agency
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TABLE OF CONTENTS
l.0 Background
2.0 Basic Evaporative Emissions
2.1 1981 and later LDGVs
2.2 1978-80 LDGVs
2.3 Pre-1978 LDGVs
2.4 Other Vehicle Types and High Altitude Rates
3.0 Tampering Offsets
3.1 Discussion
3.2 Uncontrolled LDGV Emission Data
3.3 Other Vehicle Types and High Altitude Rates
4.0 Refueling Emissions
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1.0 BACKGROUND
EPA test data have shown that evaporative hot soak and
diurnal emissions are sensitive to fuel volatility. Since July
1984, EPA has tested nearly 300 in-use vehicles in the Emission
Factor (EF) program on three fuels of varying volatility.
Based upon these .data, equations for evaporative emissions
versus fuel volatility were developed. Values from these
equations were used in an EPA evaporative study which examined
the benefits of volatility and other controls.(1) The purpose
of this report is to summarize the results of the volatility
testing, and to further document the values that were used in
the aforementioned study.
Three types of evaporative emissions will be considered
in this study: basic evaporative emission rates, tampering
offsets, and refueling emissions. Basic evaporative emission
rates are the emissions estimated from nontampered post-1970
model year (i.e., "controlled") vehicles. These vehicles are
typically equipped with carbon-filled canister (or canisters)
to help collect fuel vapors.
Tampering offsets are the emission increases due to
evaporative system tampering. The offsets ace defined as the
difference between uncontrolled and controlled emissions.
Uncontrolled emissions were estimated from precontrolled
vehicles and vehicles with tampered evaporative systems.
Examples of evaporative system tampering are missing canister
and disconnected evaporative system hoses.
Refueling emissions occur when gasoline vapor in
vehicle's fuel tank is displaced by liquid fuel during a
refueling event. They also include spillage that occurs during
refueling. Since EPA is considering promulgating onboard
evaporative controls, refueling emissions are considered as
mobile source evaporative emissions. Refueling emissions vary
with fuel volatility, and the technique used to estimate
refueling emissions at different volatilities will be briefly
discussed.
This report primarily discusses data which were available
immediately prior to the April 16, 1985 emission factor
workshop, and were used in the EPA evaporative study released
in November 1985.(1) More data have become available since,
and these will be noted where necessary.
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2.0 BASIC EVAPORATIVE EMISSIONS
In discussing the basic evaporative emissions, the rates
for 1981 and later model year LDGVs with SHED 2.0 grams/test
standard will be described first, since the majority of the
fuel volatility related test data are from these vehicles.
There are less data available for the pre-1981 LDGV and other
vehicle types, therefore the emissions at different volatility
levels of these vehicles are derived in part from the 2 gram
vehicles. Shortly after the release of MOBILES, test data on
1978-80 LDGVs (SHED 6.0 grams/test standard) at three different
volatility levels became available from an American Petroleum
Institute (API) test program and report. (2) Presentation of
this model year group will be in section 2.2. Evaporative
emission rates for pre-1978 LDGVs and other vehicle types are
briefly presented in sections 2.3 and 2.4.
2.1 1981 and later LDGVs
The three fuels used in EPA's EF program are Indolene, a
commercial fuel that is representative of the summer Reid Vapor
Pressure (RVP) in Michigan cities, and a blend of these two
fuels. Their average fuel RVPs are 9.0, 11.7 and 10.4 psi,
respectively. All vehicles in this analysis were tested with
the commercial (the highest RVP) fuel first, blended fuel
second, and Indolene fuel last. This test sequence was based
on the idea that vehicles had been operated on approximately
11.5 psi fuel prior to arriving at EPA; therefore, the most
representative measurement of their in-use emissions would be
obtained by testing on commercial fuel first. (For further
discussion on test fuel order, please see reference 1.) The
test procedure used was essentially the same as listed in the
CFR, with two exceptions. One is that when vehicles were
received from their owners the gas caps were partially opened
to prevent saturation of the canister prior to testing. The
other exception is that all vehicles were tested with their own
gas caps, and externally mounted thermocouples were used to
measure tank diurnal temperatures.
Measurements of test fuel RVP were performed each week
from each of the four fuel dispensers (two dispensers are
designated for Indolene fuel, one for commercial fuel, and one
for the blend). All fuels were analyzed according to ASTM D323
procedure with two samples taken. An average of these two
samples was used as the fuel RVP level for the week from each
fuel dispenser. Monthly averages were then calculated for each
fuel and assigned to all vehicles tested in that month. (The
results from the two Indolene dispensers were averaged.) Table
1 presents a summary of the monthly averaged fuel RVP levels.
Out of the 166 vehicles tested up to the end of March
1985, two were found as tampered vehicles: one had a canister
missing (vehicle No. 5033), and one had vacuum lines
disconnected (vehicle No. 5124). To be consistent with the
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MOBILES analysis (3), these two tampered vehicles were excluded
from this sample. Table 2 is a summary of the sample
distributions of this nontampered three-fuel evaporative
emission data base stratified by model year and by
manufacturer. (By December 5, 1985, the sample size of this
data base had increased to 279 vehicles with the addition of 45
carbureted vehicles and 70 fuel-injected vehicles. One of
these was a tampered vehicle No. 5117 which had a
disconnected bowl vent line.)
Scatter plots of emissions versus fuel RVP are presented
in Figures 1 through 4. Average emissions are listed in Table
3. Several things can be summarized from these scatter plots
and averages:
a. Both hot soak and diurnal emission rates increase
with the increasing fuel volatility. This is true for both the
carbureted and fuel-injected vehicles.
b. Diurnal emissions on the average appear to be
more sensitive to the fuel volatility than hot soak emissions.
c. The emissions are more dispersed at higher RVP
fuels (especially diurnal). The distributions of emissions at
each fuel RVP level are not exactly normal.
d. On the average, carbureted vehicles have higher
hot soak and diurnal emissions than fuel-injected vehicles.
e. The diurnal emissions of ported fuel-injection
(PFI) and throttle body injection (TBI) are very similar, while
the hot soak emissions of the PFI vehicles are somewhat lower
than the TBI vehicles.
Curve fitting methods were used to express the
relationship between the evaporative emissions and fuel RVP.
The analyses were done for carbureted and fuel-injected
vehicles separately, because of their differences in average
emissions. Ported and throttle body injected vehicles were
combined because of their similarities in fuel control as
opposed to carburetion (i.e., the absence of float bowls and
bowl vent lines to the canisters). Since the distribution of
emissions at each fuel RVP were not normal, the first model
evaluated was a least squares regression through the natural
log of emissions. Derived equations had good correlation
coefficients, but they resulted poor predictions of emissions
at higher RVP levels. For this reason, other curve fitting
methods were explored, and derived equations were evaluated by
both the correlation coefficients and the proximity by which
they predicted the average emission levels at the three RVP
means (8.96, 10.39, and 11.74).
With these criteria in mind, second degree polynomials
were found to be best for both hot soak and diurnal emissions
of the carbureted vehicles. For the diurnal emissions of the
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fuel-injected vehicles, two equations were used: a linear
equation was fitted for low volatility fuels (RVP <10.4), and a
second degree polynomial curve was used for higher volatility
fuels (RVP equal to or greater than 10.4). This strategy of
using two piece curves was viewed as a temporary solution to
fit a relatively small sample. (On a later date, when 70 more
fuel-injected vehicles were added to this sample, a single
second degree polynomial equation was found to work for diurnal
emissions of the fuel-injected vehicles.) A linear equation
was used for the hot soak emissions of the fuel-injected
vehicles. Regression coefficients are summarized in Table 4.
Table 5 is a list of the predicted evaporative emissions
for RVP levels between 8.5 and 12.0, based upon the five
equations. Emission averages at the three RVP means are
indicated in parentheses for comparison. Since the
coefficients were derived from RVP values 8.8 to 11.9 (see
Table 1), predictions are valid only within these RVP ranges.
Figure 5 is a pictorial view of the relationship between
evaporative emissions and fuel volatility based upon these five
equations. The averages for the three fuels are also presented.
2.2 1978-80 LDGVS
Additional data have been made available since the
release of MOBILE3. This set of data came from a fuel
volatility study conducted at Automotive Testing Laboratories,
Inc., East Liberty, Ohio (ATL), through an API contract. (2) A
total of 40 vehicles covering model years 1978 through 1983
were tested with three volatility level fuels (9.0, 10.5, and
11.7) under randomized fuel sequences. (See reference 1 as to
why using a randomized fuel sequence could confound some of the
results.) Out of the sixteen 1978-80 vehicles, there was one
tampered vehicle: a 1980 Fairmont which had the evaporative
system totally disabled. Another vehicle, (1980 Sunbird) was
retested with its gas cap replaced. It was not certain whether
the high diurnal emissions from as-received tests on the
Sunbird were caused by a missing gas cap or a leaking gas cap.
For this reason, this vehicle was also excluded from the
sample. Table 6 presents the two excluded vehicles and the
average evaporative emissions of the nontampered vehicles.
The sample size of these API data is considered
insufficient in developing emission rates through a curve
fitting approach. To express the relationship between
emissions and fuel volatility, the 1981+ carbureted curves were
fitted through the 1978-80 averages at 9.0 and 11.7 RVP fuels
with the following equation:
&7S-IO.RVP* = E7«_»0,9.0 + AE?-«0.C11.7-t.0>
*(AE,,,(X-«.o)/AE$1.111.7-9.0)) (1)
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where
E7i-to.RVp« = Emission level in grams at RVP = x for
1978-80 vehicles
E7«-»0 9.0 = Emission level in grams at 9.0 RVP for
1978-80 vehicles
AE7i-,0. - Emission difference from 11.7 to
9.0 for 1978-80 vehicles
AEcr, cx-9.0) = Emission difference from RVP=x to 9.0
for 1981+ carbureted vehicles
AE,i,(ii.7-9.o> = Emission difference from 11.7 to 9.0
for 1981+ carbureted vehicles.
With this equation and emission rates from Tables 5 and 6, the
1978-80 hot soak and diurnal emissions at various volatility
levels can be easily calculated. For example, at 10.5 psi the
predicted emissions are 2.91 grams for hot soak and 8.89 grams
for diurnal. The average emissions of the actual data from
1978-80 vehicles (from Table 6) at 10.5 psi were 2.25 grams for
hot soak and 10.11 grams for diurnal. The estimated emissions
for 1978-80 LDGVs are plotted in Figures 6 and 7.
2.3 Pre-1978 LDGVs
Evaporative emission data at 11.5 psi fuel for pre-1978
LDGVs were very limited.(3) To estimate their emission levels
at various volatilities, the same technique described in
Section 2.2 was used. The pre-1978 emission averages at 9.0
and 11.5 RVP fuels were obtained from the MOBILES evaporative
report (3) and are presented in Table 7.
For pre-1971 LDGVs (with no evaporative emission standard),
changes in emissions from any RVP fuel to Indolene fuel are
calculated through a linear interpolation between the two
measured RVP levels. The equation used is similar to that of
the previous section (equation 1), except that the emission
differences from 2 gram carbureted vehicles are replaced by
the volatility changes.
where
!>P r - 7 1 , RVP x Epr«-71. 9.O +
AEpr..7i.cii.B-i.o>*((x-9.0)/2.5) (2)
.-71.9.0= Emission level in grams at 9.0 RVP for
pre-1971 vehicles
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8
AEFr.-7i. = Emission difference from 11.5
; to 9.0 for pre-1971 vehicles
x = Fuel RVP.
For model year 1971 and 1972-77 LDGVs, emissions are
estimated by equation 1 with emission rates from Tables 7 and
5. Evaporative emissions at various volatility levels for
pre-1978 model year vehicles are also plotted in Figures 6 and
7.
2.4 Other Vehicle Types and High Altitude Rates
-The evaporative emissions of light duty gasoline truck
class one (LDGTls) and 1979 and later light duty gasoline truck
class two (LDGT2s) at various volatilities are the same as
LDGVs. For pre-1979 LDGT2s and pre-1985 heavy duty gasoline
vehicles (HDGVs), it is assumed that evaporative emissions vary
linearly with fuel RVPs between 9.0 and 11.5 psi. For 1985 and
later HDGVs, emissions at different volatilities are obtained
from fitting the 1981 and later carbureted curves through 9.0
and 11.5 psi emission rates. These 9.0 and 11.5 RVP rates for
pre-1979 LDGT2s and HDGVs are listed in the MOBILES evaporative
report. (3)
The high altitude emission rates are derived from low
altitude emissions in a manner consistent with the methods
described in the MOBILES evaporative report.(3) This report
used several altitude factors to adjust the emissions at low
altitude to high altitude emissions.
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3.0 TAMPERING OFFSETS
3.1 Discussion
The MOBILES program estimates the fraction of vehicles
that are tampered and nontampered, their corresponding emission
levels, and combines them to obtain the overall fleet
emissions. Consequently, to properly account for fleet
emissions at different volatility levels, there is a need to
estimate how the emissions of tampered vehicles change with
fuel volatility.
Emissions from tampered vehicles are estimated in MOBILES
by tampering offsets, which are the increases in emissions that
vehicles experience from their baseline state when they are
tampered. For evaporative emissions, the baseline state is
represented by the in-use emissions at different volatilities
that were presented in the previous sections of this report.
To estimate the tampering offsets at different volatilities, it
is necessary to know the "uncontrolled" emissions of the
different vehicle types and model years over a range of
volatilities. The tampering offsets can then be estimated by
the difference in "uncontrolled" and "controlled" emissions at
different volatilities.
Tampered items affecting evaporative emissions that were
included in MOBILE3 were disconnected evaporative system hoses
and missing canisters.(3) The incidence rates for these items
were taken from EPA's 1982 Tampering Survey. (4) Since the time
MOBILES was issued, fuel cap removal and misrouted evaporative
hoses have also been found to be more prevalent in the
Tampering Surveys than in EPA's emission factors testing.
Therefore, both hot soak and diurnal emissions must be
estimated for all four tampered conditions.
The uncontrolled evaporative emission rates used to
quantify the tampering effects are based on SHED testing of
vehicles with removed canisters and/or fuel caps. It is
currently assumed that misrouted or disconnected hoses
eventually cause the same effect as a missing canister or fuel
cap, since they can cause the canister to become saturated and
incapable of holding additional fuel vapor. This might not be
precisely correct, because the fuel tank pressure is probably
somewhat higher with a saturated canister than a removed one,
which could result in lower emissions.
It is also assumed that fuel cap removal has no effect on
the hot soak emissions of carbureted vehicles, since the
primary source of hot soak emissions in carbureted vehicles is
the float bowl. However, for fuel-injected vehicles the
primary source of hot soak emissions is thought to be fuel in
the tank which is heated by a recirculating fuel system and
exhaust system. Therefore, fuel cap removal is assumed to
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10
result in uncontrolled hot soak emissions in fuel injected
vehicles. A number of other assumptions were made in deriving
the emission rates, most of which are described in a separate
EPA report. (See reference 1, page 2-59.) The remainder of
this section will describe the data used to obtain uncontrolled
emissions at two fuel volatilities (9.0 and 11.5 psi), and how
the emissions are estimated at intermediate volatilities.
3.2 Uncontrolled LDGV Emission Data
The uncontrolled evaporative emission rates for different
vehicle types and model years at low altitude are shown in
Tables 8 and 9. These rates are based in part on the vehicle
test results presented in Table 10. The emission rates are
shown at 9.0 and 11.5 psi for both disconnects and fuel cap
removal.
The pre-1971 uncontrolled and controlled emission rates
are identical. For 1971, the uncontroled emissions are assumed
to be the same as pre-1971, with the exception that there is no
hot soak effect of fuel cap removal. The diurnal rates for
1972-1977 are based on the averages of the two vehicles in this
standard group shown in Table 10. These two vehicles
experienced lower diurnal rates than the pre-1971 vehicles,
which could be attributed to improvements in tank configuration
and placement relative to the exhaust system, and tank
downsizing. The average hot soak emission rates of these two
vehicles, 17.97 grams, are higher than the pre-1971 vehicles.
It is difficult to determine whether the hot soak emissions of
all 1972-77 vehicles would be similarly higher than the
pre-1971 vehicles. Rather than base the emissions of 1972-77
vehicles on the results of two vehicles, it was decided to use
the pre-1971 hot soak emission rate of 14.67 grams for
uncontrolled hot soak emissions of 1972-77 LDGVs.
The uncontrolled emissions for 1978-80 and 1981+
carbureted vehicles and unontrolled hot soak emissions for
fuel-injected vehicles came from the vehicles in these two
standard groups listed in Table 10. There was one 1982
fuel-injected vehicle tested with a missing gas cap; its
results are also shown in Table 10. The diurnal emissions of
this fuel-injected vehicle were similar enough to the
carbureted vehicles that we decided to use the diurnal
emissions of the 1981+ carbureted vehicles for both missing
canisters and gas caps on fuel-injected vehicles. The hot soak
emissions of this vehicle, however, were used as the hot soak
emissions of all tampered fuel-injected vehicles. EPA is
conducting additional testing of fuel-injected vehicles in
tampered conditions to augment these data. Preliminary results
indicate that this fuel-injected vehicle is very representative
of the fleet.
At fuel volatilities between 9.0 and 11.5 psi, it is
assumed that uncontrolled hot soak and diurnal emissions
increase linearly with increasing RVP. Data on one vehicle
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11
(No. 5033) with a missing canister tested in the emission
factor program which supports linearity is shown in Figure 8.
Tampering offsets estimated as the difference in
uncontrolled and controlled emissions at varying RVPs are
shown for the different LDGV model year groups in Figures
9-12. Generaly, hot soak and diurnal tampering offsets
increase with increasing RVP, since uncontrolled emissions are
increasing faster (with RVP) than controlled emissions. At
higher RVPs, however, uncontrolled and controlled emissions
should increase (with RVP) at the same rate, leading to a
constant tampering offset. This is what the diurnal emissions
appear to be doing in Figures 10-12. The reduction of the
tampering offset for diurnal emissions at higher RVPs of
1972-77 vehicles (Figure 9) is an artifact of the quadratic
expression for controlled emissions fitted through the 1972-77
data, which has controlled emissions at higher RVPs (i.e.,
between 10.5 psi and 11.5 psi) increasing faster than
uncontrolled emissions. This quadratic expression is probably
not valid above 11.5 psi.
3.3 Other Vehicle Types and High Altitude Rates
The uncontrolled emission rates of LDGTls and 1979 and
later LDGT2s at varying RVPs are identical to the LOGVs. For
pre-1979 LOGT2s and pre-1985 HDGVs, it is assumed that the
uncontrolled evaporative emission rates vary linearly with RVP
between 9.0 and 11.5 psi. The 9.0 and 11.5 psi emission rates
for these vehicles are listed in the MOBILES evaporative
report.(3) For 1985 and later HDGVs, the uncontrolled
evaporative emission rates for 9.0 and 11.5 psi fuel were
derived from the 1981 and later LDGV carbureted rates. The
methodology is the same as the controlled evaporative
emissions which is also described in the HOBILE3 evaporative
report.(3)
For high altitude, it is assumed that the uncontrolled
emission rates in most cases are equal to the low altitude
uncontrolled rates multiplied by an altitude factor of 1.3.(3)
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4.0 REFUELING EMISSIONS
The" methodology for estimating refueling emissions in
grams per mile from emissions in grams per gallon and fuel
economies of the various classes of gasoline powered vehicles
is discussed in a separate report.(5) The refueling emissions
presented herein and used in the EPA evaporative study (1) are
based on 6 grams/gallon at 11.5 psi (including spillage) and
4.8 grams/gallon at 9.0 psi. A linear relationship is assumed
between- the refueling emissions and fuel volatility to derive
emissions at intermediate volatility levels. Refueling
emissions in grams/mile for the four gasoline powered vehicle
classes are shown in Table 11.
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13
References
"Study of Gasoline Volatility and Hydrocarbon Emissions
from Motor Vehicles", November 1985, Standards Development
and Support Branch, Office of Air and Radiation,
Environmental Protection Agency, EPA-AA-SDSB-85-5.
"A Study of Factors Influencing the Evaporative Emissions
from In-Use Automobiles", API Publication 4406, April 1985.
"Evaporative HC Emissions for MOBILES", August 1984, Test
and Evaluation Branch, Office of Mobile Sources,
Environmental Protection Agency, EPA-AA-TEB-EF-85-1.
"Motor Vehicle Tampering Survey T- 1982", March 1982, Field
Operations and Support Division, Office of Mobile Sources,
Environmental Protection Agency, EPA-330/1-82-001.
"Refueling Emissions from Uncontroled Vehicles", July
1985, Standards Development and Support Branch, Office of
Air and Radiation, Environmental Protection Agency,
EPA-AA-SDSB-85-6.
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Table 1
Summary of Average Fuel RVP
in EF Three-Fueled Data Base
March 29, 1985
Test Date No. of Average Fuel RVP (psi)
(Month/Year) Vehicles Indolene Blend Commercial
08-84 23 8.8 10.4 11.7
09-84 21 8.8 10.3 11.7
10-84 32 8.9 10.4 11.6'
11-84 14 9.0 10.4 11.7
12-84 13 9.1 10.4 11.8
01-85 24 9.1 10.5 11.8
02-85 24 9.1 10.4 11.9
03-85 13 9.0 10.3 11.8
AVERAGE 8.96 10.39 11.74
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Table 2
Summary of Three-Fueled Evaporative Data Base
from EF Program: Nontampered Vehicles,
March 29, 1985
Category
Model Year
1981
1982
1983
Manufacturer
6M
Ford
Toyota
Nissan
Chrysler
AMC
Honda
Volkswagen of Germany
Fuji
Renault
Toyo Kogyo
Mitsubishi
Audi
Volkswagen of America
TOTAL
All
91
19
54
47
28
26
22
17
10
3
3
2
2
1
1
1
1
164
Sample size
Carbureted Fuel-Injected*
79
4
26
32
26
13
14
17
0
3
0
2
0
1
1
0
0
109
12 (10)
15
28 (18)
15
2
13 (13)
8 ( 8)
0
10
0
3 ( 3)
0
2 ( 2)
0
0
1 ( 1)
55 (28)
* Numbers of ported fuel injected vehicles are indicated in
parentheses.
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Table 3
Summary of Average Evaporative Emissions
of Nontampered 2.0 Gram Vehicles,
March 29, 1985
Engine Type
Carbureted
Fuel-Injected
PPI*
TBI**
N
109
55
28
27
Average
Miles
55,050
45,922
44,204
47,704
Fuel
RVP
9.0
10.4
11.7
9.0
10.4
11.7
9.0
10.4
11.7
9.0
10.4
11.7
Averacre Emissions (a/test)
Hot Soak
2.33
2.93
4.05
0.93
1.38
1.92
0.63
0.80
1.10
1.25
1.97
2.77
Diurnal
2.36
4.92
10.14
1.21
2.23
6.48
1.19
2.05
6.42
1.23
2.42
6.54
Total
4.69
7.85
14.19
2.14
3.61
8.40
1.82
2.85
7.52
2.48
4.39
9.31
*Ported Fuel-Injection
**Throttle Body Injection
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Table 4
Regression Coefficients
For 1981+ Light-Duty Vehicles
March 29, 1985
Coefficients*
Engine Type
Carbureted
Fuel-Injected
Emissions
Hot Soak
Diurnal
Hot Soak
Diurnal**
Constant
14.1630
42.1720
-2.4817
-4.9468
84.5950
A
-2.82200
-9.98890
0.37520
0.68815
-17.87500
B
0.16733
0.61782
0.0
0.0
0.95632
* Emissions - Constant + A*RVP + B*RVP*RVP.
** Use linear form (with B coefficient =0.0) if RVP <10.4, and
quadratic form if RVP ^10.4.
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Table 5
Predicted Evaporative Emissions*
On 1981+ Nontampered Vehicles
March 29, 1985
ruei
RVP
8.5
8.6
8.7
8.8
8.9
9.0
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.9
10.0
10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
11.0
11.1
11.2
11.3
11.4
11.5
11.6
11.7
11.8
11.9
12.0
FINJ
0.71
0.75
0.78
0.82
0.86
0.90( 0.
0.93
0.97
1.01
1.05
1.08
1.12
1.16
1.20
1.23
1.27
1.31
1.35
1.38
1.42( 1.
1.46
1.50
1.53
1.57
1.61
1.65
1.68
1.72
1.76
1.80
1.83
1.87
1.91( 1.
1.95
1.98
2.02
ou<
93)
38)
92)
GARB
2.27
2.27
2.28
2.29
2.30
2.32( 2.33)
2.34
2.36
2.39
2.42
2.46
2.49
2.53
2.58
2.63
2.68
2.73
2.79
2.85
2.91( 2.93)
2.98
3.05
3.13
3.20
3.28
3.37
3.46
3.55
3.64
3.74
3.84
3.94
4.05( 4.05)
4.16
4.28
4.39
FINJ
0.90
0.97
1.04
1.11
1.18
1.25(
1.32
1.38
1.45
1.52
1.59
1.66
1.73
1.80
1.87
1.93
2.00
2.07
2.14
2.21(
2.34
2.57
2.82
3.09
3.38
3.68
4.01
4.36
4.72
5.10
5.51
5.93
6.37(
6.83
7.31
7.80
1SXUJ
1.21)
2.23)
6.48)
Diurnal
GARB
1.90
1.96
2.03
2.11
2.21
2.32( 2.36)
2.43
2.57
2.71
2.87
3.04
3.22
3.41
3.62
3.83
4.06
4.31
4.56
4.83
5.11( 4.92)
5.40
5.71
6.02
6.35
6.70
7.05
7.42
7.80
8.19
8.59
9.01
9.43
9.88(10.14)
10.33
10.79
11.27
* Emission averages are indicated in parentheses for
comparison.
-------
19
Table 6
Summary of Average Evaporative Emissions
of 6.0 gram Vehicles1
Category
1980 Fairmont2
1980 Sunbird3
Nontampered Vehicles4
Fuel
RVP
9.0
10.5
11.7
9.0
10.5
11.7
9.0
10.5
11.7
Average
Hot Soak
17.55
19.54
25.83
2.74
3.56
7.45
2.44
2.25
3.35
Emissions (g/test)
Diurnal
17.39
19.55
24.84
15.31
20.37
25.51
5.16
10.11
15.92
Total
34.94
39.10
50.67
18.05
23.93
32.96
7.60
12.36
19.27
"A Study of Factors Influencing the Evaporative Emissions
from In-Use Automobiles," API Publication 4406, April 1985.
A high mileage (81,979 miles) vehicle with its evaporative
system totally disabled.
As-received results from a high mileage (80,125 miles)
vehicle which was later retested with its gas cap replaced.
Based on the remaining 14 nontampered vehicles, with aver-
age mileage of 44,467.
-------
20
Table 7
Emission Rates for 11.5 and 9.0 RVP Fuels
for Pre-1978 LDGVs*
MYR Group
Pre-1971
1971
1972-77
Hot Soak Diurnal
9.0 Fuel 11.5 Fuel 9.0 Fuel 11.5 Fuel
14.67
10.91
8.27
22.45
16.15
12.32
26.08
16.28
8.98
47.99
38.58
23.53
* "Evaporative HC Emissions for MOBILES", August 1984, Test and
Evaluation Branch, Office of Mobile Sources, Environmental
Protection Agency, EPA-AA-TEB-EF-85-01.
-------
21
Table 8
Uncontrolled Evaporative Emissions (grams/test)
LDGVs and LDGTls
MY GROUP
Pre-1971
1971
1972-77
1978-80
1981+
Garb
1981+
Finj
9.0
HS
14.67
14.67
14.67
13.29
10.36
4.93
U1S
Fuel
26
26
20
16
14
14
conra
DI
.08
.08
.90
.32
.95
.95
sets
11.5
HS
22.45
22.45
22.45
18.50
17.47
11.59
Fuel
D
47.
47.
35.
25.
25.
25.
I
99
99
45
71
71
71
9.0
HS
14.67
10.91
8.27
2.32
2.32
4.93
UOA
Fuel
D
26.
26.
20.
16.
14.
14.
v»«
I
08
08
90
32
95
95
p KtHUU>
11.5
HS
22.45
16.15
12.32
3.79
3.79
11.59
fea
Fuel
01
47.99
47.99
35.45
25.11
25.71
25.71
-------
22
MY GROUP
LD6T2
Pre-1979
1979+
Table 9
Uncontrolled Evaporative Emissions (grams/test)
LDGT2s and HDGVs
D i sconnect s
9.0 Fuel 11.5 Fuel
Fuel Cap Removed
9.0 Fuel 11.5 Fuel
HS
DI
HS
DI
HS
DI
HS
DI
18.08 42.33 27.66 77.89 18.08 42.33 27.66 77.89
Same as LDGVs, LDOTls
HDGV
Pre-1985 18.08 42.33 27.66 77.89 18.08 42.33 27.66 77.89
1985+
14.67 26.08 23.31 39.87 3.69 26.08 6.03 39.87
-------
23
Table 10
Evaporative Emissions (grams/test) of Vehicles
Used to Develop Uncontrolled Emissions
MYR Group MYR
Make
9.0 Fuel
HS Diurnal
11.5 Fuel
HS Diurnal
Ref
1972-77
1974
1975
Average
Buick
Chevrolet
15.95
19.95
17.97
22.46
19.33
20.90
27.32
34.86
36.59
34.31
31.09 35.45
1
1
1978-80
1981+
Carb
1981+
Finj
1979
1979
1980
Average
1983
1983
1981
1 OBI
A7OA
1982
1981
1981
Average
1982
Ford Pinto
Cutlass
Fairmont
Olds'
Reliant
Cutlass
M 9 1 { Hi i
naiiDU
Ford EXP
Fairmont
Mustang
Pont 6000
9
12
17
13
7
11
7
1 1
LA
7
10
15
10
4
.73
.60
.55
.29
.41
.22
.34
TO
/ w
.00
.89
.95
.36
.93
10
21
17
16
19
10
18
I Q
17
14
10
10
14
16
.25
.33
.39
.32
.12
.97
.81
ei
. DA
.81
.73
.70
.95
.69
12.
17.
25.
18.
13.
20.
10.
20.
20.
17.
11.
18
48
83
50
79
66
87
52
74
47
59
15
35
24
25
32
18
'
24
23
15
25
25
.16
.53
.84
.11
.98
.52
.16
.11
.31
.71
.01
1
1
2
1
1,
3
5
4
4
4
"Effect of Evaporative Canister Removal and Reid Vapor
Pressure on Hydrocarbon Evaporative Emission", William N.
Pidgeon, September 1984, EPA-AA-TEB-84-04 . These tests
utilized a shortened (10-minute) preconditioning period.
"A Study of Factors Influencing the Evaporative Emissions
from In-Use Automobiles", API Publication 4406, April 1985.
Results from EPA's testing of two 1981 vehicles, memo from
Thomas Penninga to Charles L. Gray, May 10, 1983.
Results from EPA's Emission Factor Testing (vehicle Nos.
4095, 4097, and 4273). Vehicles have either canister or gas
cap missing.
Vehicle No. 5033 from EPA's three-fueled data base.
vehicle has its canister missing.
This
-------
Table 11
Emission Losses Due to Refueling
Low Altitude Region
24
MYR
LDGV
9.00 11.50
LDGT1
9.00 11.50
LDGT2
9.00 11.50
HDGV
9.00 11.50
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
0.378
0.378
0.390
0.387
0.393
0.393
0.356
0.322
0.308
0.282
0.279
0.241
0.225
0.217
0.217
0.212
0.207
0.203
0.200
0.198
0.195
0.192
0.189
0.185
0.183
0.180
0.177
0.174
0.171
0.169
0.167
0.165
0.472
0.472
0.488
0.484
0.492
0.492
0.444
0.403
0.385
0.353
0.349
0.302
0.282
0.271
0.271
0.265
0.259
0.253
0.250
0.247
0.244
0.240
0.236
0.232
0.228
0.226
0.221
0.217
0.214
0.211
0.208
0.206
0.432
0.432
0.449
0.444
0.453
0.453
0.403
0.390
0.361
0.369
0.381
0.304
0.284
0.279
0.274
0.274
0.271
0.268
0.265
0.262
0.261
0.258
0.255
0.254
0.253
0.253
0.250
0.246
0.244
0.239
0.236
0.233
0.541
0.541
0.561
0.556
0.566
0.566
0.504
0.488
0.451
0.462
0.476
0.380
0.355
0.349
0.343
0.343
0.339
0.335
0.331
0.328
0.326
0.323
0.319
0.317
0.316
0.316
0.313
0.308
0.305
0.299
0.296
0.291
0.432
0.432
0.449
0.444
0.453
0.453
0.403
0.390
0.361
0.369
0.381
0.304
0.284
0.279
0.274
0.274
0.271
0.268
0.265
0.262
0.261
0.258
0.255
0.254
0.253
0.253
0.250
0.246
0.244
0.239
0.236
0.233
0.541
0.541
0.561
0.556
0.566
0.566
0.504
0.488
0.451
0.462
0.476
0.380
0.355
0.349
0.343
0.343
0.339
0.335
0.331
0.328
0.326
0.323
0.319
0.317
0.316
0.316
0.313
0.308
0.305
0.299
0.296
0.291
0.744
0.744
0.789
0.842
0.787
0.738
0.694
0.705
0.670
0.620
0.595
0.549
0.528
0.508
0.482
0.480
0.480
0.479
0.478
0.474
0.471
0.468
0.465
0.461
0.452
0.448
0.445
0.441
0.442
0.439
0.436
0.433
0.930
0.930
0.987
1.053
0.984
0.923
0.867
0.881
0.838
0.775
0.743
0.686
0.660
0.635
0.603
0.599
0.599
0.598
0.597
0.592
0.589
0.585
0.581
0.576
0.566
0.560
0.556
0.551
0.552
0.548
0.545
0.542
-------
25
FIGURE 1
FIGURES
Data from 1981+ Carbureted Vehicles
29-
^
'A
M
B
j8
42, 19-
71
| 10-
Cd
9-
4
^ 4
A A
AA A^ ^
4 A
^4 A iAA
A|A /**
A AA A|A a*
ii i J
30 30 -
29 33-
/] M
20 S ^. 20-
a
1
9-
Dhim.il Rmi«nnT^f v* Ri«l RVP
Data from 1981+ Carbureted Vehicles
444
A A«4
&IS
i &i
A AA A A4
A ^A
44 44 A^*
A A ^ A||A
AV 4* &A4
aJL jj||
ifi "^
r 30 30
29 29-
!/> ~V)
I i
1342. 4J 19-
S t*
2 °
10 a a 10-
II
3 9-
0 n-
Diumul Fmi^frions ^^ F\iitl RVP
Data from 1981+ fuel-Injected Vehicles
A
Ai
A
A A^A
A
44
4 AA
44 A AA
A A* 4A&
A AS AA"
A A B4A
ii« m J
29
|
i
19 4J
en
§
10 a
1
9
.
FUei RVP (psi)
89 9 99 10 10.9 11 11.9 13
Fuel RVP (psi)
-------
FIGURES
12
10-
co
CO
6
cti
co
g
8-
6-
w 4-
r-t
6
2-
Evaporative Emissions vs. Riel RVP
1981+ Model Year Vehicles
Dlurnal
Carbureted
Diurnal
Iuel-Iq)ected
Hot Soak
Carbureted
Hot Soak
fuel-Injected
12
-10
CO
-8
a
cO
w
a
o
U4
-2
8.5 9 9.5 10 10.5 11
Riel RVP (psi)
11.5
12
O\
-------
27
25
CO
20-
co
S 15
CO
I 10
CO
CO
5-
55
50
45
4°
2 30
co 25
I 20
CO
£ 15
W
10
5
0
FIGURE6
Hot Soak Emissions vs. Fuel RVP
Pre-1981 Model Year Vehicles
Pr«-1971
1971
972-77
1978-80
CO
20
CO
15 g
CO
-I
CO
CO
-5
8.5 9 9.5 10 10.5 11 11.5
Riel RVP (psi)
FIGURE?
Diurnal Emissions vs. Fuel RVP
Pre-1981 Model Year Vehicles
12
Pre-1971
1972-77
1978-80
55
8.5
9
9.5
10 10.5
RVP
-50
-45
-40
-35
-30
25
-20
-15
-10
5
0
co
CO
S
£
S3,
CO
§
CO
CO
11
11.5 12
-------
FIGURE 8
30
25-
w
20-
6
cd
15-
w
O
W inj
co 10 H
~
6
w
5-
Evaporative Emissions vs. Riel RVP
from Tampered Vehicle #5033
8.5
I
9
liurnal
Hot Soak
9.5 10 10.5 11
Riel RVP (psi)
11.5
12
30
-25
CO
r20
8
CO
a
m w
10 w
6
w
N)
oo
-------
25
~* 20
6 is
i
VI
§ ,0
FIGURE 9
Tampering Offsets vs. Fuel RVP
19T72--77 Model tear Vehicles
S 5 9 9.5 10 10.5 11 115 12
Riel RVP (psi)
23
29
20
15 g g IS
<« (0
& 4
-10 i a
to
FIGURE 10
tempering Offsets vs. Fuel RVP
1978-80 Model tear Vehicles
Okirnal
85 9 95 10 10.5 11
Fuel RVP (psi)
11.5 13
15 fi
to
2
5
25
20-
S 15-
£
VI
§ ,o
5-
FIGURE 11
Tampering Offsets vs. Fuel RVP
19814- Carbureted Vehicles
Okxnol
Hal Soak
85 9 95 10 105 11
Fuel RVP (psi)
115 12
25
15 g
2 fi
il o.
6 is-
VI
2 10
v>
FIGURE 13
Tampering Offsets vs. Riel RVP
198H- Fuel-Injected Vehicles
Olurnol
Hot Sook
85 9 95 10 10.5 II
Fuel RVP (psi)
115 12
-29
-10
------- |