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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                                                              12

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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                                                              14
                            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

-------
                                                              15
                            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.

-------
                                                               16
                            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

-------
                                                              17
                            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.

-------
                                                            18
                           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

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