EPA-460/3-76-014
June 1976
INVESTIGATION
AND ASSESSMENT
OF LIGHT-DUTY-VEHICLE
EVAPORATIVE
EMISSION SOURCES
AND CONTROL
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
Ann Arbor, Michigan 48105
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This report is issued by the Environmental Protection Agency to report technical
data of interest to a limited number of readers. Copies are available free of
charge to Federal employees, current contractors and grantees, and nonprofit
organizations - as supplies permit - from the Air Pollution Technical Information
Center, Environmental Protection Agency, Research Triangle Park, North
Carolina 27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by Exxon
Research and Engineering Company, Linden, New Jersey 07036, in fulfillment
of Contract No. 68-03-2172. The contents of this report are reproduced herein
as received from Exxon Research and Engineering Company. The opinions,
findings, and conclusions expressed are those of the author and not necessarily
those of the Environmental Protection Agency. Mention of company or product
names is not to be considered as an endorsement by the Environmental Protection
Agency.
Publication No. EPA-460/3-76-014
11
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EPA-460/3-76-014
INVESTIGATION
AND ASSESSMENT
OF LIGHT-DUTY-VEHICLE
EVAPORATIVE
EMISSION SOURCES
AND CONTROL
by
1'..). Clarke
Exxon Research and Engineering (Company
P.O. Box 8
Linden, New Jersey 07036
Contract No. 68-03-2172
EPA Project Officer: R.E. Kruse
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Emission Control Technology Division
Ann Ardor, Michigan 48105
June 1976
U S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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TABLE OF CONTENTS
Page No.
I. INTRODUCTION 1
II. SUMMARY 1
III. EVAPORATIVE CONTROL APPROACHES IN CURRENT USE 3
A. Sources of Evaporative Emissions 3
B. Current Automotive Practice for
Control of Evaporative Emissions 6
1. Carburetor Evaporative Emission Control 6
2. Fuel Tank Evaporative Emission Control 6
3. Charcoal Canisters 6
4. Purge Systems 9
5. Summary of Techniques for
Evaporative Emission Control 9
C. Classification of Systems 10
D. Survey of Evaporative Control Systems 10
IV. MAGNITUDE AND SOURCE OF
EVAPORATIVE MISSIONS FROM CURRENT VEHICLES 13
A. Test Fleet and Test Method 13
1. Vehicles 13
2. Vehicle Preparation 13
3. SHED Procedure 16
4. Test Sequence 17
B. Evaporative Emissions from 1973-75 Cars 17
1. Total Evaporative Losses from Vehicles 17
2. Background Data 20
3. Evaporative Losses by Mode of Operation 20
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TABLE OF CONTENTS (CONTINUED)
Page No.
4. Evaporative Losses by Individual Sources ..... 20
a. Overflow from the
Carburetor Storage System .......... 20
b. Carburetor Leaks ............... 25
c. Overflow from the Charcoal Canister ..... 25
d. Other Losses ................. 25
V. MODIFICATION OF VEHICLES FOR
LOWER EVAPORATIVE EMISSIONS ............... 25
A. Hardware for Better Control
of Evaporative Emissions ............... 26
1. Air Cleaner Overflow ............... 26
2. Carbon Canister Overflow ............. 28
3. Carburetor Leaks ................. "
B. Vehicle Selection and Modification
1. Selection .................... 31
2. Current Emissions ................ 31
3. Individual Vehicle Modifications
for Improved Emission Control .......... 32
C. Emissions from Modified Vehicles ........... 50
1. Evaporative Emissions ........... .. . . 50
a. Total Evaporative Emissions ......... 50
b. Adjustment for Background Levels ....... 53
c. Loss by Mode of Operation .......... 53
2. Exhaust Emissions ................ 54
D. Conclusions from Vehicle Modification Work ..... 55
E. Estimated Costs, Effectiveness
and Durability of Modifications ........... 55
ii
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TABLE OF CONTENTS (CONTINUED)
Page No.
VI. EMISSION LEVELS OF MODIFIED VEHICLES
UNDER SEVERE TEST CONDITIONS 57
VI I. I1ALOCENATED HYDROCARBONS IN EVAPORATIVE EMISSIONS .... 58
iii
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I. INTRODUCTION
This report describes a study carried out by the Exxon Research
and Engineering Company for the EPA to assess the effectiveness of light
duty vehicle evaporative emission control systems.
KvaporntLve emissions from light duty vehicles have been con-
trolled nationwide beginning with the 1971 model year vehicle. The
emissions can be divided into two main categories: (1) carburetor
emissions, and (2) fuel tank emissions. A control level has been set by
EPA at 2.0 grams per test as measured by the "carbon trap" method. How-
ever, an improved measurement technique, the SHED method, has been
developed recently. (SHED test, Sealed Housing for Evaporative Deter-
minations, is SAE Recommended Practice J171a.) The new method has shown
that the "carbon trap" method underestimates vehicular evaporative emis-
sions. Because of this EPA has sought to conduct a study to determine the
performance of in-use evaporative control systems with the more accurate
SHED method. In addition, there is a considerable incentive to improve
the performance of current evaporative control systems. This is because
the exhaust hydrocarbon emissions have been reduced considerably in
recent years and consequently the evaporative hydrocarbons represent
an appreciable portion of total hydrocarbon emissions of a vehicle. This
program,undertaken by Exxon Research and Engineering Company,is a study
which addresses itself to the following facets of the vehicular evaporative
loss problem:
1. A survey and analysis of evaporative control systems on
current vehicles.
2. A study of the magnitude and source of evaporative emis-
sions from current vehicles using the SHED measurement
technique.
3. Modification of vehicles to demonstrate that performance
of evaporative control systems can be improved.
4. The effect of severe operating conditions on evaporative
losses from modified cars.
II. SUMMARY
In 1971, evaporative emission controls were imposed by EPA
on light duty vehicles. This was to limit the loss of hydrocarbons
evaporating from the fuel tank and carburetor of a vehicle. Recently,
EPA determined that the test compliance method, known as the "carbon trap"
method, underestimated evaporative emissions and a new test method has
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- 2 -
been proposed by EPA^ '. The new test method, known as the SHED method,
has shown that the evaporative emission controls in the field are less
effective than originally estimated and in the case of some critical
late model vehicles, evaporative emissions are of the same magnitude as
the exhaust hydrocarbon emission.
To define and deal with the problem at hand, a program has
been initiated at Exxon Research and Engineering Company with EPA
sponsorship. This program has assessed the effectiveness of current
Evaporative Control Systems (ECS) and has shown the feasibility of
various hardware approaches which control evaporative emissions to a
very low level. The performance of ECS's in current use was evaluated
using a cross section of 1973-75 cars with representative control
techniques. For this, the Sealed Housing Method for Evaporative
Determinations (SHED), SAE J171a procedure was used. (This involves
enclosing the vehicles in a shed and monitoring the hydrocarbon level
in the shed.). The average evaporative loss for a 20 car group was
8.7 grams/SHED test. The lowest loss was 0.5 gram and the highest was
30.6 grams.
The results of this study indicate that the bulk of the
evaporative losses occur during the hot soak phase of the SHED test,
and the source of emissions is the carburetor bowl. Current ECS's
appear effective in handling the diurnal loss from the fuel tank for
most vehicles. The major source of loss was overflow from the air
cleaner snorkel, indicating inadequate storage volume for carburetor hot
soak vapors reaching the air cleaner. Hydrocarbons also escaped from
poorly fitting seals and other leak sources. In some cases there was
significant overflow from the carbon canister.
Hardware was developed to improve ECS performance. Six
vehicles were modified to demonstrate the feasibility of improving
current systems. The modifications involved: (1) the venting of the
carburetor bowl to the canister to alleviate air cleaner overflow,
(2) utilization of larger carbon beds, (3) adaptation of increased purge
rates, and (4) sealing and capping of leak sources. These modifica-
tions were successful in lowering the evaporative emissions to
2.0 grams/SHED test or lower for each of the six modified vehicles.
The costs of the hardware used to accomplish this has been estimated
to vary from $2.00 to $25.00.
We have concluded from this work that it is feasible to
markedly improve the performance of current evaporative control systems.
(1) 41FR2022
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- 3 -
III. EVAPORATIVE CONTROL APPROACHES IN CURRENT USE
A. Sources of Evaporative Emissions
The evaporative emissions from a vehicle's fuel system can be
divided into two main categories, (1) carburetor emissions and (2) fuel
tank emissions. The evaporative emissions from the carburetor occur
primarily because of fuel boiling in the carburetor bowl and, to a
lesser extent, by diffusion across the hydrocarbon concentration gradients
at the carburetor vents. The first process occurs during the "hot soak"
period, that is when the heat from the engine is being dissipated to the
surroundings after shutdown. This causes the temperature of the fuel
in the carburetor bowl to rise over a period of about 30 minutes during
which time fuel boils in the carburetor bowl. Beyond this point the
carburetor slowly cools, the fuel stops boiling and the subsequent losses
are primarily due to a diffusion process. Most of the carburetor losses
occur during the rising temperature portion of the soak period.
The magnitude of carburetor hot soak losses is a function of the
increase in bowl gasoline temperature during the hot soak, the volume of
the bowl, and the fuel's volatility. Figure 1 is representative of opera-
tion on a gasoline with Reid Vapor Pressure (RVP) of 9 psi (62.1 kPa).
Typical losses are in the neighborhood of 10-15 grams for a carburetor bowl
gasoline temperature increase of 10 to 16°C (maximum temperature of 82 to
88°C). The band in Figure 1 spans the normal size range of carburetor
bowl volumes from 50 cc (lower curve) to 100 cc. The range of carburetor
bowl sizes found in the field is much larger than 50-100 cc's, and the
fuel volatility can vary significantly, thus the range of possible carbu-
retor hot soak losses is much larger.
Evaporative emissions from the fuel tank are primarily due to
two concurrent processes which cause an increase in the temperature of
the fuel in the tank. This rise in tank temperature can occur, (1) while
the vehicle is standing still due to variation in the ambient temperature
and the evaporation losses are then referred to as "diurnal losses", (2)
while the vehicle is operating, due to heat transfer from the exhaust
system to the fuel tank and the losses are then referred to as "running
losses". The magnitude of fuel tank diurnal losses is shown in
Figure 2. The abscissa is the maximum temperature reached during the
diurnal, normally 27.7°C in evaporative emission testing. Again we are
using the standard test fuel with a Reid Vapor Pressure of 9 psi (62.1 kPa).
For the normal range of fuel tank volumes, using the prescribed 40% fuel
fill, diurnal fuel tank losses vary from 10 to 25 grams or roughly 0.3 gram
per litre of fuel tank capacity. Diurnal cycles to higher temperatures
increase evaporative losses as shown.
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FIGURF 1
CARBURETOR HOT SOAK EVAPORATIVE EMISSIONS
ARE STRONGLY AFFECTED BY MAXIMUM BOWL TEMPERATURE DURING SOAK
STANDARD 9 RVP GASOLINE
65 75 85
MAXIMUM CARBURETOR BOWL TEMPERATURE DURING HOT SOAK, °C
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60
FIGURE 2
DIURNAL CYCLE EVAPORATIVE EMISSIONS
ARE STRONGLY AFFECTED BY AMBIENT TEMPERATURE RISE AND FUEL TANK VOLUME
2
O
M
CO
V)
M
H
50
STANDARD 9 RVP GASOLINE
INITAL GASOLINE TEMPERATURE, 15.5GC
VOLUME
OF TANK
95
Litres
40
S 30
20
10
75
55
35
MAXIMUM DIURNAL CYCLE TEMPERATURE, °C
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- 6 -
Running losses from most ECS equipped vehicles are not signif-
icant. If fuel tanks have non-vented caps and are vented to the intake
system, the vapors leaving the tank will be burned in the engine. Carbu-
retor bowls are vented to the carburetor air intake, allowing vapors to
be burned in the engine.
B. Current Automotive Practice for Control of Evaporative Emissions
In this section, the types of Evaporative Control Systems (ECS)
used by the automotive industry are reviewed.
1. Carburetor Evaporative Emission Control
The two types of carburetor losses are running losses and hot
soak losses. The running losses are controlled internally in the car-
buretor by venting from the carburetor bowl to the air intake of the car-
buretor via the balance tube (Figures 3 and 4), allowing carburetor running
vapors to be burned in the engine. This is the case because the pressure
in the intake is lower than that in the carburetor bowl when the vehicle
is running.
To control hot soak losses during engine shutdown, two basic
systems are used. The first is storage of the vapors in the induction
system during shutdown followed by eventual consumption in the engine
after start-up. The hydrocarbon vapors move from the bowl into the
carburetor intake through the balance tube and then into the carburetor
throat and air cleaner. Because hydrocarbons are denser than air, they
displace the air. Figure 3 shows a system of this type.
The second control system for hot soak losses uses both the
induction system and a charcoal canister to store vapors. A line from
the bowl to the canister diverts a portion of the vapors to this alter-
nate storage. This is illustrated in Figure 4. A carburetor vent valve
opens the line to the canister at idle and while shut down. At other
times, the line is closed. Vapors stored in the carbon canister are
ultimately purged by a portion of engine combustion air which is drawn
through the canister during operating modes.
2. Fuel Tank Evaporative Emission Control
Fuel tanks are designed as "closed" systems (non-vented fill
caps) which are connected to a vapor storage system through a vapor-liquid
separator. The vapor-liquid separator reduces system load by returning
condensed and entrained liquid to the tank. Three types of vapor storage
techniques are used: (1) charcoal canister, (2) engine crankcase, and
(3) an auxiliary tank.
3. Charcoal Canisters
The majority of ECS's use a charcoal canister to store the hydro-
carbon vapors emitted from the fuel tank. In most of these systems, the
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FIGURE 3
EVAPORATIVE EMISSION CONTROL SYSTEM
Air Cleaner
Carburetor
Bowl
Orifice
Liquid/Vapor
Separator
Press tire/ Vacuum
F j 1. l.e r Gas Cap
Tank Vent Line
Canister
o o
o o
LJ
Purge
Line
O
o o
O O O O O Q
o o o o o o
o o
o o o o
Filter
Fuel Tank
Activated
Charcoal
\
\_Purgu
urgt
Air
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- 8 -
FIGURE 4
EVAPORATIVE EMISSION CONTROL SYSTEM
Air Cleaner
Balance Tube
— Vent Valve
Bowl Vent
Line to Bed
Pressure/Vacuum
Filler Gas Cap
o o o o o o
o o o o o c
To PCV
Valve
Liquid/Vapor
Separator
Purge
Valve
Activated
Charcoal
Fuel Tank
Filter
Purge Air
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- 9 -
fuel tank vapors from both hot soak and running losses pass into the
canister. A few systems, however, use a control valve which allows run-
ning loss vapors to bypass the charcoal bed and move directly to the engine.
The charcoal canister system functions via an adsorption-
regeneration process. Hydrocarbon vapors are adsorbed on the surface of
the activated carbon for storage purposes. Later the vapors are desorbed
from the surface, by passing a portion of engine combustion air through
the charcoal bed. This regeneration, or purging process, is necessary
to restore the capacity of the bed for further hydrocarbon storage.
There are several types of carbon canisters in use. They may
be classified by the method of introducing purge air to the bed and by
the technique for the handling of running vapors. In most cases, purge
air enters the bed through the open bottom of the canister as illustrated
in Figure 3. A replaceable filter is used to prevent dust contamination.
A second type of canister in use has a sealed bottom with an air inlet
on top. In some canisters, running vapors as well as hot soak emissions
pass into the carbon bed. In others, a purge valve is used which allows
running vapors to bypass the carbon bed. An example of this type of
canister is illustrated in Figure 4.
4. Purge Systems
There are three general types of purge systems for regeneration
of carbon beds. These systems can purge to: (1) the air cleaner, (2) the
carburetor, and (3) the Positive Crankcase Ventilation valve (PCV). Units
purging to the air cleaner generally utilize the pressure drop through the
air cleaner and inlet system to draw purge air through the canister. One
system utilizes the velocity of the air in the air cleaner snorkel to pull
air through the carbon bed. Purging to the carburetor is the most popular
technique. An example of this is shown in Figure 3. A port at the idle
position is most often used so that at idle the purge rate will be very
low but will Increase as the throttle is opened. The third type of purge
is to the I'CV system. An example of this is shown in Figure 4. With this
system, a purge valve is used which permits only tank running vapors to
reach the engine at idle. As the throttle is opened from idle, engine
vacuum opens the purge valve on the canister so that both tank running
vapors and stored vapors in the bed are drawn into the engine via the purge
air stream.
5. Summary of Techniques for Evaporative Emission Control
, Induction system only
a. Carburetor Bowl •^
Emissions Tor ^^v.
Both induction system
and charcoal bed canister
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u T? i T i Charcoal bed
b. Fuel Tank
Emissions To; - Auxiliary Tank
Engine crankcase
^ Open or closed bottom
c . Carbon ^^ . ., , . . , ,
Canister: \AU Vap°rS enter the bed
Running vapors bypass bed
d. Carbon Canister
Purses To;
e. Other
C. Classification of Systems
Evaporative Control Systems have been divided into two general
categories: (1) those using a charcoal canister, and (2) those using a
system other than a charcoal canister for storage of fuel tank vapors. Over
98% of the 1973-1975 vehicle population utilize a charcoal canister. These
systems have been further typed according to carburetor storage and type of
canister purge. This is shown in Figure 5. Systems not using a charcoal
canister may use the engine crankcase or a small auxiliary tank for storage.
A further subdivision is by the style of canister. A descrip-
tion of the charcoal canisters used by each U.S. manufacturer is given
in Table I.
D. Survey of ECS's in Use
A cross section of about 120 vehicles from the 1973-1975 car
population has been used in this survey of evaporative control systems
in current use. In addition to describing the ECS, the fuel system com-
ponents which affect their function such as proximity of fuel tank to a
heat source such as muffler, and use of a fuel vapor return line to the
tank have also been surveyed. This survey covered all families of engines
from each U.S. manufacturer and the leading foreign-manufactured cars.
All told, this group is representative of at least 99% of the vehicles
in the 1973-1975 car population. The results from this survey are shown
in Appendix I.
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FIGURE 5
CLASSIFICATION OF EVAPORATIVE EMISSION CONTROL SYSTEMS
A. Systems Using Charcoal Canisters
Type Carburetor Storage
I
II
III
IV
V
VI
Induction
System
Only
Induction
System and
Canister
Type of Canister Purge
Carburetor
PCV
Air Cleaner
Carburetor
Air Cleaner
B. Systems Not Using Charcoal Canisters
VII
VIII
IX
Induction
System for
Carburetor
Vapors
Tank for Fuel Tank Vapor Storage
Crankcase for Fuel Tank Vapor Storage
Other Than Above
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TABLE I
Manufacturer
General Motors
Chrysler
Ford
American Motors
No.
1
2
3
4
1
2
3
1
2
CHARCOAL CANISTERS ON U.S. CARS
No. of
(purge
(purge
(purge
Tubes
2
3
3
valve)
4
valve)
3
4
valve)
2
2
3
2
3
Tube
Inlet
Tank
Tank
Carburetor Bowl
Tank
Tank
Carburetor Bowl
Tank
Carburetor Bowl
Tank
Carburetor Bowl
Tank
Tank
Tank
Carburetor Bowl
Tank
Tank
Designation
Outlet Other Remarks
Purge
Purge
Purge Vacuum for
Purge Valve
Purge Vacuum for
Purge Valve NJ
i
Purge Carburetor Bowl sometimes not used
Purge Vacuum for
Purge Valve
Purge 300 gms
Purge 500 gms
Purge 700 gms
Purge
Purge
Carburetor Bowl
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(!!)!•: AMD SOIJKCK OK
VK KMJSSJONS FROM CURRENT VKHJCLKS
This part of the program evaluated the effectiveness of the
evaporative control systems in current use on U.S. and imported cars.
A. Test Fleet and Test Method
1. Vehicles
The twenty vehicles selected for testing are described in
Table II. The criteria for their selection were: (1) to be representa-
tive of the control techniques in use, (2) to represent carburetor
designs and fuel tank volumes in the field, and (3) be a cross section
of the nation's 1973-1975 car population. All vehicles were at least
90 days old prior to the test date. The source of each vehicle is shown
in Table III. As far as possible, non-undercoated vehicles were used.
Prior to completion of the last phase of this program, it was necessary
to return Car No. 3 and replace it with Car No. 21 which was similar in
make, model and engine to its predecessor.
2. Vehicle Preparation
Each vehicle underwent a mechanical inspection and was tuned
to factory specifications in cases where the ignition system and
exhaust emissions were abnormal. For this, the ignition system was
checked by an electronic analyzer and the exhaust emissions by the
diagnostic procedure'-*-' developed by Exxon Research for tail pipe CO and
HC emissions at idle and 2500 rpm.
Other preparation involved thermocouple installations in the
carburetor bowl, the underhood area, and the fuel tank. The thermocouple
for underhood temperatures was located about four inches in front of the
carburetor bowl. In addition to the in-tank thermocouple required by
the SAE J171a test method, a skin type was attached to the outside of the
tank at the fuel-air interface. A new fuel tank was used for each vehicle.
Two lines were welded into the tank, a drain line and a line from the vapor
space in top of the tank. This latter line is for a transducer connection
to monitor fuel tank pressure during the diurnal and hot soak cycles. The
integrity of the fuel tank system was checked prior to the initiation of the
test.
(1) J. Panzer, "Idle Emissions Testing - Part II," SAE Paper 740133
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TABLE II
VEHICLES FOR SHED TESTS
(All Automatic Transmission
Car
Ho.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
36
17
IS
19
20
(1)
(2)
(3)
(4)
(5)
(6)
Displ.
Make Model Yr.
Ford LTD 75
Pontiac G.P. 75
Chrysler NYer 75
Ford Pinto 74
Chevrolet Nova 74
Chevrolet Impala 74
Plymouth Duster 73
Buick Le Sabre 75
Chevrolet Vega 75
Oldsmobile 98 74
AMC Hornet 74
Plymouth Fury III 73
Dodge Dart 74
Datsun 610 74
Mazda RX-4 74
Mercury Comet 74
Volvo 144 74
Ford Squire 75
VW Beetle 75
Mercury Monarch 75
Type of Evaporative Control
Canister has a purge control
Also uses a carbon canister
Fuel injection.
Litres
5.75
6.56
7.21
2.00
4.10
5.74
3.69
5.74
2.29
7.46
3.80
5.90
5.21
1.95
1.31
4.10
1.98
7.54
1.60
4.95
Cu. In.
351
400
440
122
250
350
225
350
140
455
232
360
318
119
80
250
121
460
97
302
No.
Cyl. -
8
8
8
4
6
8
6
8
4
8
6
8
8
4
Rotary
6
4
8
4
8
System (ECS) described in Figure
valve.
for fuel tank vapor storage.
No.
Venturis
2
4
i<
2
1
2
1
4
2
4
1
2
2
2
4
1
F.I. (4)
4
F.I. (4)
2
5.
Except #19)
Fuel
Litres
92
95
100
49
79
98
60
98
60
93
6A
98
60
52
64
60
60
79
40
73
Tank
Gals .
24
25
26.5
13 v
21
26
16
26
16
26
17
26
16
14
17
16
16
21
10.5
19
Carbon canister for fuel tank vapor storage.
Condenser tank for fuel tank vapor storage.
Air
CrmcU
Y
y
y
y
Y
Y
Y
V
Y
Y
Y
Y
Y
Y
Y
Y
N
Y
Vapor Return
Line?
Y
N
M
N
Y
Y
N
Y
Y
Y
Undercoated
N
N
Y
M
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
Y
N
Y
ECSV
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- 15 -
TABLE III
SOURCE OF VEHICLES
Car No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1.9
20
21
Make
Source
LTD
Pontiac
Chrysler
Pinto
Nova
Chevrolet
Duster
Buick
Vega
Olds
Hornet
Plymouth
Dart
Datsun
Mazda
Comet
Volvo
Ford
VW
Monarch
Chrysler
Leased
Leased
Leased
Leased
Private Owner
Private Owner
Private Owner
Private Owner
Private Owner
Private Owner
Private Owner
Private Owner
Private Owner
Private Owner
ERE Car
Private Owner
Private Owner
Private Owner
Leased
Leased
Private Owner
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3. SHED Procedure
Evaporative losses were measured using the Sealed Housing for
Evaporative Determinations (SHED) procedure as described in SAE Recommended
Practice J171a. This method employs an enclosure in which the vehicle is
placed during diurnal and hot soak phases of the test. Vapors escaping
from the vehicle are retained in the enclosure and the increase in the
hydrocarbon concentration of the atmosphere in the enclosure represents
the evaporative emissions.
Details for the SHED test are outlined in SAE J171a. These
were followed in this work with one or two exceptions such as for
preconditioning. Some of the operational steps for the test are covered
below:
Preconditioning:
The preconditioning procedure for this test was as follows:
(1) three consecutive LA-4(D cycles [7.5 mile (12.1 km) trips],
(2) shut down for 10 minutes, and (3) a fourth LA-4 cycle. This was
followed by an 11-16 hour soak at about 24°C.
Diurnal Cycle:
A one hour soak in the SHED during which the temperature of
the fuel in the tank is raised from 60 to 84°F (15.6 to 28.9°C). A
pressure transducer was used to monitor fuel tank pressure during the
diurnal cycle and the hot soak.
Federal Test Cycle:
The vehicle was quickly placed on the chassis dynamometer after
the diurnal cycle for an exhaust Federal Test Procedure. The dynamometer
had previously been warmed up with a different vehicle and the load set.
Hot Soak:
A one hour hot soak in the shed followed immediately after the
Federal cycle to complete the test.
The fuel for the SHED test was Indolene of 9.0 psi (62.1 kPa)
RVP. Inspections for this fuel are shown in Appendix II.
(1) 1972 Federal Test Procedure
-------
- 17 -
4. Test Sequence
The sequence of testing for each vehicle is outlined in the
diagram in Figure 6. Those vehicles which emitted less than 2 grams/
test were tested a second time by the SHED procedure to complete their
test cycle. All vehicles failing the 2 gram limit underwent a source
test to determine the location of the leaks. This was followed by two
tests to quantify the emissions from individual leak sources using the
technique described in Appendix III. A third quantifying test was made
in cases where there was an abnormal variance between the first two
tests. This was followed by a second SHED test to complete the testing
schedule. (Hot and cold background tests were also carried out on each
vehicle as per SAE J171a.)
B. Evaporative Emissions from 1973-75 Cars
1. Total Evaporative Losses from Vehicles
Total losses, as measured by the SHED procedure, varied from
a low 0.5 gram to a high of 30.6 grams for the 20 car group. The average
for the group was 8.7 grams. The range for the 20 cars is shown graphically
below:
TOTAL EVAPORATIVE LOSSES
20 Cars
30
201^-
Grams
Per
Tes t
10
Vehicles
-------
- 18 -
FIGURE 6
FLOW DIAGRAM OF TESTING PROCEDURE
BACKGROUND
TESTS
SHED
TEST
IF
Em. £ 2 Gr.
IF
Em. > 2 Gr.
SOURCE
LOCATION TEST
IF
Em. > 2 Gr.
INDIVIDUAL
SOURCE TEST
(1)
INDIVIDUAL
SOURCE TEST'
IF
(1) # (2)
IF (1) = (2)
INDIVIDUAL
SOURCE TEST
(3)
SHED
TEST
SHED
TEST
IF
Em. < 2 Gr.
-------
- 19 -
In tliia program, the data ,-iro Cor the most pnrl ;in ;ivrr;ij',<' of
two SUED tests. The initial test may be slightly higher than the .second
SHED test because leaks in the air cleaner were sealed prior to the
second test (as part of the quantifying procedure). In cases where
there was a substantial difference between the two SHED tests, a third
was run and the three averaged for the vehicle. The total evaporative
loss was adjusted for vehicle background hydrocarbon levels. The
results for individual runs on each car are summarized in Appendix IV.
The table below shows total evaporative losses by make and
model in descending order from worst to best. No particular U.S. manu-
facturer appears to stand out from a good performance standpoint. A
Plymouth Duster was the best U.S. car, however, the Chrysler NYer is
one of the poorest for high evaporative losses. Some models from both
G.M. and Ford also are comparatively good and others fall in the poor
category. The best vehicle was a fuel injected VW Beetle with only 0.5
gram total evaporative loss. The other fuel injected vehicle in the
group, the Volvo, falls in the poorest half of the 20 car group.
Table IV
Total Evaporative Losses By Make and Model
Total Loss
Grams
30.6
17.3
17.1
10.9
10.7
10.6
9.5
9.3
7.5
7.5
6.7
6.6
6.0
5.8
5.3
4.1
2.8
2.8
1.5
0.5
Make
Model
Yr.
Ford
Mercury
Chrysler
Chevrolet
AMC
Mazda
Olds
Mercury
Volvo
Pontiac
Ford
Buick
Ford
Plymouth
Chevrolet
Chevrolet
Dodge
Datsun
Plymouth
VW
Country Squire
Comet
NYer
Nova
Hornet
RX-4
98
Monarch
144
G.P.
LTD
Le Sabre
Pinto
Fury III
Impala
Vega
Dart
610
Duster
Beetle
75
74
75
74
74
74
74
75
74
75
75
75
74
73
74
75
74
74
73
75
Car
No.
18
16
3
5
11
15
10
20
17
2
1
8
4
12
6
9
13
14
7
19
VI
III
IV
II
III
VII
I
III
IX
I
VI
I
III
IV
I
V
I
VIII
IV
IX
(1) ECS type described in Figure 5.
-------
- 20 -
No single type of ECS system appears to be superior to the
others in the above table. There are, however, desirable features from
individual ECS systems which will be discussed later.
2. Background Data
Evaporative losses from sources other than the fuel system are
generally small. Cold background data for U.S. vehicles fall in the
range of 0.0 to 0.2 grams per test. Hot backgrounds were higher ranging
for 0.0 to 0.7 grams per test. Table V and Appendix IV show individual
vehicle background data. The only car to have a high background from a
non-fuel oriented source was the 1975 VW, Car No. 19. The background
levels of this vehicle were 0.7 and 0.8 grams cold and hot respectively.
These do not appear to be the result of gasoline absorption from previous
spillage on the vehicle as was the case for several test cars. Both the
hot and the cold background tests were continued for 24 hours. The rate
of hydrocarbon emission did not diminish significantly during the 24 hour
periods. Comprehensive probing for the source of hydrocarbon emission
did not reveal any sources. Additional testing showed that essentially
all of the hydrocarbon was coming from the outside of the vehicle and only
a small fraction from the interior. This vehicle is at least 5-6 months
old. It appears that the paint may be the source of the emission.
3. Evaporative Losses by Mode of Operation (Test Cycle)
The bulk of the evaporative losses occur during the hot soak
mode of operation. Evaporative losses by mode of operation are shown in
Table VI. For the U.S. cars in this group, 83% of the evaporative loss
was experienced during the hot soak. This means that most U.S. cars
handle fuel tank vapors from the diurnal cycle satisfactorily in their
carbon canister storage system. The loss during the diurnal cycle for
70% of the U.S. cars was 10% or less of the total loss. For the re-
maining U.S. cars, diurnal losses were as high as 65% of the total loss.
Imported vehicles follow the same pattern as the U.S. car population.
4. Evaporative Losses by Individual Sources
a. Overflow from the Carburetor Storage System
Hydrocarbon vapors escaping from the air cleaner during the
hot soak are by far the largest contributor to evaporative losses. One
half of the hydrocarbon loss is by this route with vapors escaping from
the air cleaner snorkel. This indicates that the air cleaner and in-
duction system do not have sufficient capacity to store all of the vapors
emitted from the carburetor bowl during shut down. A summary of the con-
tribution from each source to the total emission for the cars is shown in
Table VII along with the mode of operation during which the loss occurs.
The source of losses for individual vehicles is summarized in Table VIII.
-------
- 21 -
TABLE V
EVAPORATIVE LOSSES ADJUSTED FOR BACKGROUND
Car
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Total Loss Before
Background Adjustment,
Grams
6.7
7.5
17.2
6.2
11.0
5.3
1.5
7.0
4.7
10.0
10.8
6.6
2.9
3.1
12.2
17.4
7.7
30.7
2.0
9.3
Background, Grams
Cold
__(D
-(1)
0.0
0.0
0.0
— (1)
—(1)
0.1
0.0
0.2
0.0
0.1
0.0
0.1
0.5(2)
0.0
0.1
0.0
0.7(3)
0.0
Total Loss
Adjusted for
Hot Background, Grams
— (1)
— (1)
0.1
0.2
0.1
— (1)
__(!)
0.3
0.6
0.3
0.1
0.7
0.1
0.2
l.l^2)
0.1
0.1
0.1
0.8(3)
0.0
6.7
7.5
17.1
6.0
10.9
5.3
1.5
6.6
4.1
9.5
10.7
5.8
2.8
2.8
10.6
17.3
7.5
30.6
0.5
9.3
(1) No background data for these cars. The results from the background
tests for Gars No. 1, 2, 6 and 7, which were the first four to be
tested for background, were very high due to gasoline spillage on
the front carpet. A fuel can had been used as an auxiliary fuel tank.
This took place after the SHED testing. Procedure changed after these
four cars.
(2) Evidence of gasoline spillage in the trunk prior to the SHED tests,
which would account for the high background.
(3) Appears to be coming from external enamel paint.
-------
- 22 -
TABLE VI
EVAPORATIVE LOSS BY MODE OF OPERATION
Car No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Total Loss,
Grains
6.7
7.5
17.1
6.0
10.9
5.3
1.5
6.6
4.1
9.5
10.7
5.8
2.8
2.8
10.6
17.3
7.5
30.6
0.5
9.3
% of Loss
Diurnal Cycle
50
5
45
30
2
10
-
10
5
5
5
65
5
35
0
0
60
5
-
20
Hot Soak
50
95
55
70
98
90
—
90
95
95
95
35
95
65
100
100
40
95
—
80
-------
- 23 -
TABLE VII
SUMMARY OF SOURCES OF EVAPORATIVE
LOSSES FROM 20 CAR GROUP
Location
1 - Air Cleaner
2 - Carburetor Leaks(2)
3 - Carbon Canister
4 - Carbon Canister
5 - Other
Mode
Hot Soak
Hot Soak
Diurnal
Hot Soak
Diurnal & H.S.
% of
Total Losses
50
25
10
10
5
(1) Snorkel - other leaks sealed before tests.
(2) Primarily from around accelerator pump shaft. Some smaller leaks
elsewhere.
-------
- 24 -
TABLE VIII
Car
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Total Loss,
Grams
6.7
7.5
17.1
6.0
10.9
5.3
1.5
6.6
4.1
9.5
10.7
5.8
2.8
2.8
10.6
17.3
7.5
30.6
0.5
9.3
SOURCES OF EVAPORATIVE LOSSES
Air
Diurnal
Cycle
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
15(2)
0.0
0.0
5
0.0
Cleaner
Hot
Soak
0.0
60
20(2)
65
45
95
70
90
75
40
0.0
60
0.0
100
85
50
20
I of Total
Carbon
Diurnal
Cycle
45
45(2)
30
0.0
0.0
0.0
0.0
0.0
0.0
35
0.0
—
0.0
0.0
0.0
Evaporative
Canister
Hot
Soak
45
20(2)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
35
0.0
—
0.0
0.0
10
Loss
Garb.
Leakage
0.0
25
10
0.0
50(3)
0.0
25
0.0
20
60
30
35
45
0.0
15
35(4)
65
SHED(^)
10
5
5
5
5
5
5
10
5
0.0
0.0
40(5)
0.0
0.0
10
5
0.0
25
20
0.0
50
(1) Hydrocarbon vapors not collected in quantifying test or otherwise accounted for.
(2) Estimated.
(3) This carburetor also externally vented upon slight pressure in bowl.
(4) Leakage from gas cap.
(5) Crankcase storage.
-------
- 25 -
The vehicles with the lowest loss from the air cleaner were
those utilizing both canister and air cleaner storage for vapors from
the carburetor bowl. These are Type IV-VI systems. Using the canister
to handle part of the hot soak load alleviates the overloading of the
air cleaner. However, unless the canister has sufficient working capa-
city to adsorb the added load, it in turn will overflow.
b. Carburetor Leaks
This is the second largest contributor to evaporative losses
and accounts for 25% of the total loss. For the most part, these leaks
occur in carburetors which do not utilize a diaphragm type of accelerator
pump (used in Ford Motor Company and some other carburetors). Sixty
percent of the cars tested had problems with hydrocarbon leakage around
the accelerator pump shaft where it passes through the air horn or body
of the carburetor. Car No. 5, in addition to leakage around the accel-
erator pump linkages, vented to the atmosphere with a slight pressure
buildup in the carburetor bowl.
c. Overflow from the Charcoal Canister
This is the third largest source of evaporative emissions with
10% occurring during the diurnal cycle and an additional 10% during the
hot soak. This indicates insufficient working capacity in the canister
of five of the twenty cars in the group. Vehicles with overflow during
the hot soak utilized the carbon bed to store carburetor bowl vapors as
well as fuel tank vapors.
d. Other Losses
Some hydrocarbon is lost from small leaks such as from the
ends of the throttle shaft as it passes through the carburetor body and
other places. Running losses during the Federal Cycle were not measured.
The most likely source of running vapors is venting through the gas cap
due to pressure build-up in the tank. Car No. 17 was the only vehicle to
have a significant pressure build-up in the fuel tank. It vented hydro-
carbon vapors through the gas cap during the diurnal cycle and hot soak
and probably during the Federal Cycle.
V. MODIFICATION OF VEHICLES FOR LOWER EVAPORATIVE EMISSIONS
The purpose of this phase of the program is to develop hardware
to give better control of emissions, select vehicles with typical or
representative sources of evaporative emissions, and then to modify the
vehicles to demonstrate the effectiveness of the new hardware.
-------
- 26 -
A. Hardware for Better Control of Evaporative Emissions
1. Air Cleaner Overflow
Five techniques to control air cleaner overflow during the
hot soak are shown as Controls No. 1 through 5 in Table IX and discussed
below:
Control No. 1 - Vent the Carburetor Bowl to the Canister
A portion of the hot soak emissions is directed to the carbon
canister for storage in lieu of the air cleaner. A valve in the carburetor
opens to vent the bowl to the canister during idle and shutdown. At other
times, the vent line is closed. Venting of the bowl to the canister is now
used in the ECS's of Vehicles No. 1, 3, 9, and 12. This modification
requires minimum flow resistance in the line to the canister, viz. line
should slope toward the canister and be of adequate size to handle the
vapor load. Undue resistance to flow results in excessive hydrocarbon
vapors entering the air cleaner via the carburetor bowl balance tubes.
This modification requires a larger storage capacity in the carbon canister
than ECS's with air cleaner storage only for hot soak emissions. The
canister must now accommodate both the hot soak and the diurnal emissions
at the same time.
Control No. 2 - Ventilating Engine Compartment with a Fan
•*
A fan is used to provide cool air to the engine compartment to lower
the temperature increase of the bowl during the hot soak. The lower bowl
temperature contributes to a decrease in hot soak emissions and lessens the
load on the storage system. The fan can be actuated by a thermal switch
through the ignition system. This will cool the engine compartment until
its temperature is lowered to the control point at which time the fan is
shut off.
Control No. 3 - Barrier at the Base of the Air Cleaner Snorkel
Hydrocarbon vapors are heavier than air and tend to preferentially
settle down. A barrier at the base of the snorkel deters the loss of emis-
sions out the snorkel.
Other controls to limit air cleaner overflow such as decreasing
carburetor bowl volume and use of louvers in the hood for ventilation are
suggested in Table IX. They were not included in this program.
-------
TABLE IX
METHODS FOR CONTROL OF EVAPORATIVE EMISSIONS
Control
No.
1*
2*
3*
4
5
6*
7*
8*
9*
10
11
12*
13
14*
15
Source
Air cleaner overflow
Air cleaner overflow
Air cleaner overflow
Air cleaner overflow
Air cleaner overflow
Canister overflow
Canister overflow
Canister overflow
Canister overflow
Canister overflow
Canister overflow
Canister overflow
Canister overflow
Carburetor leaks
Carburetor leaks
Description
Remarks
Vent carburetor bowl to canister.
Ventilating engine compartment with a
fan during hot soak.
Barrier at base of snorkel.
Decrease bowl working volume.
Louvers in hood for ventilation.
Increase size of carbon bed.
Increase purge rate.
Close bottom of canister and vent to
top of unit.
Control No. 2
Controls No. 4 and 5
Heat purge air.
Minimize heat input to fuel tank.
Shield tank from hot muffler, etc.
Minimize vapor space in the fuel tank.
Close spaces around shafts with boots,
caps, etc.
Use a diaphragm type accelerator pump
in lieu of the plunger type.
Less vapors generated because of lower
carburetor bowl temperatures.
Less vapors generated.
Less vapors generated.
Two canisters used in parallel.
Apply for ECS with carburetor bowls
vented to the canister.
For ECS's with vented bowls to the
canister.
Less vapors generated.
^Controls demonstrated in this program.
-------
- 28 -
2. Carbon Canister Overflow
Eight techniques are suggested for control of an overloaded
carbon canister. These are shown as Control 6 through 13 on Table IX
and described below:
Control No. 6 - Increase Size of Carbon Bed
This modification will increase the working capacity of the system.
(Working capacity is the maximum weight of hydrocarbon that can be handled
in the storage unit.) In many cases, it is not necessary to increase
purge rate to realize an increase in working capacity with a larger canister.
This is the case because, even though the purge flow rate is lower per unit
of charcoal with a larger bed, the average hydrocarbon loading on the
charcoal during the purge cycle is higher, resulting in more hydrocarbon
being removed from the canister.
Control No. 7 - Increase the Purge Rate
This technique will increase the working capacity of those canister
storage units which currently have low purge rates. ECS's which utilize
air cleaner purge systems, Type III and VI, generally have low purge volumes.
In many instances, it may be necessary to utilize carburetor or PCV purge
systems to raise the purge volume to the desired level.
Control No. 8 - Close the Bottom of Open Canisters
This would prevent seepage or migration of hydrocarbon from the
bottom of the open canister. A sketch of a cover with a vent pipe is shown
on the following page.
-------
- 29 -
CAP PREVENTS LOSS FROM BOTTOM OF CANISTER
Inlet Purge Air
G.M. Canister
Cap for Open Bottom
Controls No.10 through 13 in Table IX outline additional
controls to handle canister overflow. These controls were not used in
this program with exception of Control No. 12 which was applied to
Vehicle No. 17.
3. Carburetor Leaks
below:
Two controls are suggested for carburetor leaks as indicated
Control 14 - Use of Flexible Boot and Covers
Carburetor leaks around accelerator pump shafts can be
prevented by use of a flexible boot around the shaft to seal the opening.
In cases where a boot will not suffice, a cover such as the one shown in
Figure 7 can be used.
-------
- 30 -
FIGURE NO. 7
SKETCH OF A SEAL FOR CARTER GARB. LEAK. - CAR NO. 11
Garb. Body
Accel. Pump Shaft
Cover for Accel. Pump Shaft
Cover Design;
The two sides and bottom would be cast into the carburetor base.
Front side would be held in place with a snap clip.
-------
- 31 -
Control 15 - Use of a Diaphragm Type Accelerator Pump
Use of a diaphragm type accelerator pump such as on Ford
carburetors in lieu of the piston type on Rochester Products and
Carter units will prevent leakage. It will require retooling in most
cases.
B. Vehicle Selection and Modification
1. Selection
Six vehicles were selected from the 20 car group for ECS
modification. The evaporative emissions and ECS's of these vehicles
are representative of the 20 vehicle group. The vehicles are shown
below:
Table X
Vehicles for Modification
ECS
Car No.
1
2
3
11
15
17
Make
Ford
Pontiac
Chrysler
AMC
Mazda
Volvo
Year
75
75
75
74
74
74
Type
VI
I
IV
III
VII
IX
Purge
Air Cleaner
Carburetor
Carburetor
A.C. Snorkel
(1)
(2)
(1) Modified Type VII system.
(2) Fuel injected. Canister for tank vapors.
It was necessary to return Car No. 3 before completion of the
test. A vehicle of same make, model and year was obtained for completion
of the work. This is Vehicle No. 21 in the report.
2. Current Emissions
The following table summarizes the original evaporative
emissions of the vehicles selected to be modified:
-------
- 32 -
Table XI
Evaporative Emissions from Six Test Vehicles
Car
No.
1
2
3
11
15
17
21
SHED Test
Grams
Total
6.7
7.5
17.1
10.7
10.6
7.5
13.9
%
Diurnal
50
5
45
5
0
60
40
%
Hot Soak
50
95
55
95
100
40
60
Emission Source
Air
Cleaner Canister Carburetor
N
Y
Y
Y
Y
Y
Y
Slight
Y
N
N
N
Slight
Y
Y
Y
N
3. Individual Vehicle Modification
for Improved Emission Control
The most promising hardware based on engineering judgment
was installed on each test vehicle for the first modification. Addi-
tional modifications were then made as necessary to bring the SHED
test level to 2.0 grams or less. The modifications were prototype
in nature and not a finished hardware. For example, a manually operated
clamp on the carburetor vent line performed the job of the carburetor
vent valve. (Vent valves were on the factory carburetor for Vehicle No. 1,
3, and 9.) Also, the underhood fan was activated manually.
The primary goal of this work was to demonstrate an ECS system
modified to exhibit an emission level of 2.0 grams or less/SHED test.
However, no attempt was made to test the longevity of the modifications.
In addition, the modified systems were not optimized for best exhaust
emissions and/or for driveability. A description of the modifications
performed on each of the six vehicles is outlined in Tables XII to XVIII.
Table XII
Modification for Vehicle No. 1 - LTD
Component
Factory ECS
Modification
(1) Carbon canister
(2) Purge
(3) Carburetor
(4) Air cleaner
3 tube Ford (low pressure
drop)
Air cleaner
Leak around choke shaft
Leak sources at base of
snorkel and other fit-
tings
Replaced with 4 tube Vega
canister with purge con-
trol valve. Bottom of
canister capped.
Changed to PCV purge.
Cover fitted over leak
source(l).
Sealed with silicone
sealant.
(1) Sketch of cover in Figure 8.
-------
FIGURE NO.8
PROPOSED SEAL FOR CHOKE
ROD PASSAGE THROUGH AIR HORN
Cover - Clips
Over Walls to
Seal Shaft"
.Walls Cast Into
Air Horn to Form Seal
Choke Rod
-------
- 34 -
Comments;
A PCV purge was installed after flow tests had Indicated
that air cleaner only and an air cleaner-snorkel combination purge
were inadequate. This is discussed in Appendix V. The 4 tube Vega
canister was obtained from a 1974 model vehicle in daily service.
Photographs of these modifications are shown in Figures 9 and 10.
Table XIII
Modifications for Vehicle No. 2 - Pontiac
Component
Factory ECS
Modification
(1) Carbon canister Delco 2 tube
(2) Purge
(3) Carburetor
(4) Air cleaner
(5) Other
Carburetor
Small leak around accel-
erator pump shaft.
Small leaks
Replaced with 3 tube
Chrysler canister.
Bottom of unit capped.
No change.
Boot installed around
shaft. Carburetor
bowl vented to the carbon
canister.
Leak sources sealed with
silicone sealant.
Underhood fan installed
to ventilate underhood
and lower carburetor bowl
temperature during hot
soak.
Comments:
Uridorhood Tan used to demonstrate the feasibility of decreasing
hydrocarbon vapor generation in the carburetor bowl by lowering bowl
temperature. No modification of the carburetor purge is required
in this installation. See Figures 11 and 12 for details of this instal-
lation and also Appendix V.
After completion of tests with the above system, a Vega canister
was installed and tests were conducted without use of the underhood ventilating
fan. Results of the tests with this system were also less than 2 grams/test.
-------
I
UJ
FIGURE 9 COVER OVER CHOKE LINKAGE TO PREVENT HYDROCARBON LEAKAGE ON THE LTD
-------
- 9C -
-------
FIGURE 11 FAN FOR UNDERHOOD VENTILATION AND CARBURETOR MODIFICATION FOR THE PONTIAC
-------
OJ
00
FIGURE 12 CARBON CANISTER (3 TUBE) FOR THE PONTIAC
-------
- 39 -
Table XIV
Modifications for Vehicle No. 21 - Chrysler
Component
Factory ECS
(1) Carbon canister One 3 tube
(2) Purge
(3) Carburetor
(4) Air cleaner
Carburetor
Leak around accelerator
shaft.
Some small leaks
Modification
Two 3 tube canisters in
parallel were used.
Bottoms of canisters
capped.
No change.
Boot installed. Second
carburetor bowl venteu
directly to canister.
Sealed with silicone
sealant. Barrier installed
at base of snorkel.
Comments:
The large volume fuel tank and the large carburetor bowl volume
for this car generate too much hydrocarbon vapor for one standard size
canister to handle. (Purge volume is already high.) Consequently, two
canisters were utilized. In actual practice, it would be more feasible
to use one canister with a larger bed. It was necessary to vent the
second carburetor bowl directly to the canister because the balance tubes
between the bowls and the air cleaner permitted an excessive amount of
vapors to enter the air cleaner with a single vent. Details of this
modification are shown in Figures 13 and 14 and Appendix V.
Table XV
Modifications for Car No. 11 - Hornet
Component
Factory ECS
Modification
(1) Carbon canister 2 tube AMC
(2) Purge
(3) Carburetor
(4) Air cleaner
Air cleaner snorkel
Leak around accelerator
pump shaft linkage.
Several small leaks
Changed to a 4 tube Vega
with a purge control valve.
Bottom capped on canister.
Modified to a PCV system.
Cap installed over linkage.
Carburetor bowl vented to
canister.
Leaks sealed with sealant.
Barrier installed at the
base of the snorkel.
(1) See Figure 15.
-------
o
i
-------
TUT? /"TJTJVCT T7T5
-------
-p-
K)
FIGURE 15 CARBURETOR BOWL VENT AND COVER FOR ACCELERATOR PUMP LINKAGE FOR THE HORNET
-------
- 43 -
Comments:
Purge flow tests indicated insufficient flow rate from the
snorkel even with modifications to increase flow. The Vega canister
used here was obtained from a 1974 Vega which had been driven daily.
See details of this modification in Figures 15, 16, and 17 and
Appendix V.
Table XVI
Modifications for Car No. 15 - Mazda
Component
(1) Carbon canister
Factory ECS
Modifications
(2) Purge
(3) Carburetor
(4) Air cleaner
(5) Other
Comments:
Small carbon canister in
top of air cleaner for
diurnal cycle only.
Crankcase
Bowls vent to air
cleaner.
No change in the diurnal
ECS. Added a 4 tube Vega
canister for vapors from
the carburetor bowl.
Bottom of Vega canister
capped.
PCV line used for the
purge for Vega canister.
Each bowl individually
vented to the Vega
canister.
No change.
A fan was installed to
ventilate underhood during
hot soak.
This vehicle utilizes a small carbon canister on the top of the
air cleaner for storage of diurnal cycle vapors. No change was made in
this part of the original ECS. The (large volume) two bowl carburetor re-
quired separate vents with minimum resistance from each side to transfer
vapors into the canister. Even then, an underhood fan was used to cool the
carburetor bowl to retard the rate of hydrocarbon vapor release. Without
the fan, hydrocarbon vapors from the balance tubes and for drippage in
carburetor throat caused the SHED level to exceed the 2 gram level.
and 21.
For additional details, see Appendix V, and Figures 18, 19, 20,
-------
-O
-p-
FIGURE 16 CARBURETOR MOnTFTCATTOW AMH TAR RON
FOR TWP
-------
- 45 -
I
I
fe,
O
00
s
£•(
fe,
o
t)
00
s
I
p-(
^
^
M
«3
CJ
-------
-P-
I
-------
-------
I
CO
-------
- 50 -
Table XVII
Modifications for Vehicle No. 17 - Volvo
Component
Factory ECS
Modification
(1) Carbon canister Small one tube carbon
canister.
(2) Purge
(3) Carburetor
(4) Air cleaner
(5) Fuel tank
Intake manifold
None - fuel injected.
No leaks.
Uses an equalizing valve
regulating tank pressure
to about 1.0 psi
(6.9 kPa).
Changed to a 2 tube AMC
canister.
No change.
No change.
Pressure of equalizing
valve modified to 0.5 psi
(3.5 kPa). Baffle in-
stalled between fuel tank
and muffler.
Comments:
The factory canister was ineffective. (It did not change weight
during the test period.) Consequently the AMC canister was utilized. The
high fuel tank pressure resulting from the original equalizing valve
pressure of 1.0 psig caused hydrocarbon vapors to escape through the gas
cap and other fittings. The lower pressure for the modified equalizing
valve corrected this hydrocarbon loss.
For additional details, see Appendix V and Figures 22 and 23.
C. Emissions from Modified Vehicles
1. Evaporative Emissions
a. Total Evaporative Emissions
SHED test results for the six modified vehicles averaged
1.5 grams with a high of 1.9 and a low of 1.1 grams. These data are
an average of two or more tests and include vehicle background.
Individual car data are compared with unmodified results as follows:
-------
- 51 -
p
r3
o
o
t— I
H
H
o
M
Pi
<
u
1.1
o
i i
-------
OA1CA mi (TI3IRS
LO
I
-------
- 53 -
Table XVIII
Comparison of "Modified" Emissions
and "As Received"
Car Total Grams/SHED Test
No. Make Year Modified As Received
1 LTD 75 1.2 6.7
2 Pontiac 75 1.9 7.5
11 Hornet 74 1.2 10.8
15 Mazda 74 1.5 12.2
17 Volvo 74 1.1 7.7
21 Chrysler 75 1.9 14.0
b. Adjustment for Background Levels
The SHED data above were adjusted for background levels using the
background data from the initial SHED test work (Table V) with the excep-
tion of Car No. 15. Because of the exceptionally high initial background
for this vehicle, it was retested. Background adjustments are shown below:
Table XIX
Total Evaporative Losses Adjusted for.Background
Car Before Background Background, After Background
No. Make Adj., Grams Grams Adj., Grams
1 LTD 1.2 - 1.2
2 Pontiac 1.9 - 1.9
11 Hornet 1.2 0.1 1.1
15 Mazda 1.5 0.5 1.0
17 Volvo 1.1 0.2 0.9
21 Chrysler 1.9 0.1 1.8
c. Loss by Mode of Operation
The hot soak and diurnal losses for the modified vehicles are
shown in the following table.
-------
- 54 -
Table XX
Diurnal and Hot Soak Data
Car
No.
1
2
11
15
17
21
Make
LTD
Pontiac
Hornet
Mazda
Volvo
Chrysler
Year
75
75
74
74
74
75
Total
1.2
1.9
1.2
1.5
1.1
1.9
SHED, Grams
Diurnal
0.2
1.2
0.3
0.6
0.7
0.6
CD
Hot Soak
1.0
0.7
0.9
0.9
0.4
1.3
(1) Not adjusted for background.
2. Exhaust Emissions
Modifying the ECS caused some changes in the exhaust emissions
of the modified vehicles. The greatest change was in the CO levels. The
CO level: (1) decreased for the three vehicles with catalyst beds, (2) in-
creased for one vehicle, and (3) did not change for the remaining two
vehicles. Only minor changes in the HC and NOX levels were noticed. A
summary of the exhaust emissions data is shown below:
Table XXI
Exhaust Emissions - Modified Vs. As Received
Car
No.
1
2
21
11
15
17
Make
LTD
Pontiac
Chrysler
Hornet
Mazda
Volvo
Year
75
75
75
74
74
74
ECS
Modified
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Exhaust Emissions,
Grams/Mile(1)
CO
4.44
6.75
4.05
6.95
13.3
23.2
26.9
24.5
9.
11.
90
7
22.6
13.3
HC
0.52
0.54
0.68
0.80
1.10
2.32
1.51
1.50
1.82
2.11
1.24
0.91
NOX
1.87
1.62
1.36
1.31
1.83
1.98
1.13
1.24
0.65
0.88
1.58
2.15
(1) Average of two or more tests.
-------
- 55 -
This program was not of sufficient duration to identify the
factors causing the above changes. The changes might be due to:
Alteration in the Induction System
For each car, the canister was changed as the vehicle was modi-
fied. This could change the purge rate and, in turn, may affect manifold
vacuum. (There were no noticeable effects on driveability during the
Federal Procedure.) In the case of Car No. 1, 11, and 15, major changes
were made in the ECS.
Increase in ECS Hydrocarbon Levels
The improved ECS in each case requires the engine to handle a
greater amount of hydrocarbon from the storage systems. This might affect
the A/F ratio and subsequently exhaust emissions.
D. Conclusions from Vehicle Modification Work
The experience gained in modifying ECS systems can be summarized
as follows:
1. Larger carbon canisters (activated carbon) were required in
many cases.
2. Induction system containment of carburetor hot soak emis-
sions does not appear to be an adequate control for carbur-
etor emiss ions.
3. All air cleaner and carburetor leak sources must be eliminated.
4. Air cleaner and air cleaner snorkel purge systems are inad-
equate purge systems for a stricter control of evaporative
emissions .•
5. Under very severe underhood temperature conditions, it may
be necessary to minimize heat input to the carburetor by
mechanical means such as by an underhood fan.
E. Estimated Costs, Effectiveness,
and Durability of Modifications
We have estimated the costs for each of the modifications shown
in Table IX. Cost data are outlined in Table XXII. The basis for the
cost data has been estimated as manufacturer's cost times two. In the
case of carburetor modifications, the indicated figures were obtained
from Exxon's automotive consultant who is highly knowledgeable in this
field and has been associated with a major carburetor manufacturing
company before retirement. The cost of the fan was obtained from an
automotive manufacturer. In the case of carbon canisters, the cost
information was obtained from a major manufacturer of these devices.
-------
TABLE XXII
ESTIMATED COSTS, EFFECTIVENESS, AND DURABILITY OF MODIFICATIONS
Estimated
Modification
A. Air Cleaner Overflow:
Control No. 1 - Bowl vent to canister
Control No. 2 - Ventilate with fan
Control No. 3 - Barrier at base of snorkel
Control No. 4 - Smaller bowl
Control No. 5 - Ventilate with louvers
B. Canister Overflow:
Control No. 6 - Increase carbon bed 50%
Control No. 7 - Increase current purge
Control No. 8 - Close canister bottom
Control No. 9 - Control 2
Control No. 10 - Control 3
Control No. 11 - Heat purge air
Estimated Costsd)
$
0.50(D
17.00(2)
0.20
0.20(1)
0.0
4.00(3)
0.60CDC4)
0.20(1)
17.00(2)
0.20(D
0.50(D
Control No. 12 - Minimize heat input to fuel tank l.OO+C1)
Control No. 13 - Minimize tank vapor space
C. Carburetor Leaks:
Control No. 14 - Seal shafts with boot
Control No. 15 - Use diaphragm accel. pump
15.0(5)
0.30(D
i.ood)
(1) Basis for estimated cost in case of carburetor and ECS modifications is two
(2) Vehicle retail price estimate from an automotive manufacturer. Capacity -
(3) Cost increment based on cost information from a
(4) In cases where an existing canister is replaced
(5) Not a firm estimate.
Potential
Effectiveness
High
High
High
High
Low
High
High
High
High
High
Fair
High
Poor
High
High
Anticipated
Durability
Good
Good
Good
Good
Good
Good
Good
Good
Good
Good
Good
Good
Poor
Good
Good
times the cost to manufacturer.
100 CFM (47.2 dm3/S).
charcoal canister manufacturer.
by the Vega canister, cost
is $1.00.
-------
- 57 -
The estimated costs for the actual modifications for each of
the six vehicles are shown below. The costs vary from a low of $2.00
to a high of $25.20. The two vehicles with underhood fans, the Pontiac
and Mazda, have cost figures substantially above the other vehicles.
Following these tests, the Pontiac was equipped with a Vega canister to
replace the fan. Use of this canister also resulted in emissions less
than 2 grams/test. The cost figures shown in Table XXII were used in
estimating the modification price for each vehicle. Details for the
modification costs for each vehicle are given in Appendix VI.
Table XXIII
Estimated Costs of Modifications
Car Modification
No. Make Year Costs, $
1 LTD 75 2.00
2 Pontiac 75 18.30 or 2.30( '
11 Hornet 74 2.50
15 Mazda 74 25.20
17 Volvo 74 2.00
21 Chrysler 75 5
(1) $18.30 uses an underhood fan. $2.30 system uses
a Vega canister which eliminates the fan.
(2) Assumes one canister of larger than current
capacity would be used in lieu of two units as
per this work.
The potential effectiveness and durability of each of the
modifications is shown in Table XXII. In our opinion, most modifications
are expected to be effective with a good durability rating. The basis for
the ratings include personal judgment and field experience with modifica-
tions of similar nature. No longevity runs were performed as part of this
program.
VI. EMISSION LEVELS OF MODIFIED VEHICLES
UNDER SEVERE TEST CONDITIONS
The performance of two of the modified vehicles has been
evaluated under the severe test conditions of (1) use of a fuel of
higher RVP than Indolene, and (2) raising the maximum temperature of the
diurnal cycle. For this work, Vehicles No. 1 and 2 were selected.
Vehicle No. 2 was equipped with the underhood fan for these tests.
Test conditions were standard SHED with the exception of the higher
volatility fuel in one case and the higher temperature range for the
diurnal in the second case. For the high volatility fuel, butane was
added to Indolene to raise its RVP from 62.1 to 71.7 kPa (9.0 to
10.4 psi). Inspections for this fuel are given in Appendix II.
Standard Indolene was used for the high temperature diurnal cycle runs.
For these, the diurnal range was 15.6 to 35°C (60 to 95°F) in lieu of
the standard SHED range of 15.6 to 28.9°C (60 to 84°F).
-------
- 58 -
The results from this work indicate that Vehicle No. 2,
the Pontiac, had more reserve storage capacity after modification than
the LTD, Vehicle No. 1. The 1.4 psi (9.65 kPa) increase in RVP increased
SHED emissions 1.0 gram for the Pontiac and 4.5 grams for the LTD. Ex-
tending the diurnal cycle increased SHED losses 2.1 grams for the Pontiac
and 3.2 grams for the LTD. Data are summarized below and presented in
detail in Appendix VII and in Table XXIV.
Table XXIV
Higher Losses Under Severe Test Conditions
Increase Loss,
Grams/SHED Test
Car . High High Temp.
No. Make RVP Diurnal
1 LTD 4.5 3.2
2 Pontiac 1.0 2.1
The more severe test conditions described above did not
significantly affect exhaust emissions with these two vehicles, both
of which have catalytic reactors to control tailpipe emissions.
Exhaust emissions data are included in Appendices No. VII'and VIII.
VII. HALOGENATED HYDROCARBONS IN EVAPORATIVE EMISSIONS
A brief analytical study has been carried out to measure the
level of halogenated hydrocarbons in the evaporative emissions from
leaded fuels. Two halogenated hydrocarbons, ethylene dichloride and
ethylene dibromide,are part of the lead scavenger package of most leaded
gasolines. The concentration of these scavengers is about 0.1 wt. % of
a fuel containing about 3.0 ml/TEL per gallon. The ethylene dichloride is
present at twice the concentration level of the ethylene dibromide.
An exploratory analytical procedure was developed to measure the
scavenger level in the evaporative emissions of a vehicle. For this,
a gas chromatograph equipped with a sensitive microcoulometer detector
was used. The source of the evaporative emission was a full size car
hot soaking in a SHED for one hour. The fuel was a full boiling range
gasoline containing about 3.0 ml/TEL gallon as Motor Mix. The hydrocarbon
level in the SHED was 300 ppm C after the hot soak. The concentration of
ethylene dichloride in the SHED was 0.128 yg/1. This is about 0.1% of the
hydrocarbon value in the SHED. We detected but did not quantify the
ethylene dibromide. The boiling point for the ethylene dibromide is much
higher than the ethylene dichloride - 131.7°C vs. 83.7°C.
Because of the low level of scavengers in evaporative emissions,
it was decided not to conduct additional work in this area at this time.
-------
APPENDIX NO. 1-1
SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE CONTROL SYSTEMS
F = Full Size
I = Intermediate
C = Compact
Make Yr . Model
Ford 73
73
73
74
74
75
75
75
74
73
74
75
Mercury 73
74
74
75
75
73
I
F
F
I
F
I
F
I
C
C
C
I
F
F
I
I
C
I
Displ.
Litres
5.75
6.56
7.03
5.75
6.56
5.75
6.56
4.95
3.33
1.60
2.29
4.10
7.03
7.54
5.75
5.75
3.33
4.95
Canister Purge
# of 2 3 4 Purge Line To:
Bbls. Tube Tube Tube Valve? PCV Carb Air Cl.
4 / /
2 / /
4 / /
2 / /
2 / /
2 / /
2 / /
2 / /
1 / /
1 / /
2 / /
1 / /
4 / /
4 / /
2 / /
2 / /
2 / /
2 / /
Fuel Tank
Litres
85.2
85.2
85.2
83.3
83.3
90.8
90.8
85.2
49.2
41.6
49.2
90.8
83.3
83.3
100.3
100.3
49.2
85.2
Near
Exh. Line?
V
N
N
Y
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Vapor
Return
Line?
N
Y
Y
N
N
N
N
N
N
N
N
N
Y
Y
N
N
N
N
Type
III
III
III
III
III
VI
VI
HI
I
III
III
III
III
III
III
III
I
III
Ln
VD
Lincoln
75
7.54
100.3
N
VI
-------
APPENDIX NO. 1-2
SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE CONTROL SYSTEMS
F = Full Size
I = Intermediate
C - Compact
Make
Plymouth
or
Dodge
Chrysler
AMC
Yr.
73
75
75
74
74
73
73
75
74
75
74
73
73
75
75
74
- 74
Model
I
I
I
F
F
F
F
F
F
F
F
F
C
I
I
I
I
Displ
Litres
3.69
3.69
3.69
5.21
5.90
6.56
6.56
7.21
6.56
7.21
7.21
7.21
3.80
4.23
4.98
5.90
4.98
Canister Purge
# of 2 3 4 Purge Line To:
Bbls. Tube Tube Tube Valve? PCV Carb Air Cl.
1 / /
1 / /
1 / /
2 / /
4 / /
2 / /
4 / /
4 / /
4 / /
4 / /
4 / /
4 / /
1 / / /
1 / ' /
2 / /
4 / /
2 / /
Fuel Tank
Litres
60.6
60.6
60.6
60.6
79.5
79.5
79.5
79.5
73.5
98.0
98.0
98.0
39.7
60.6
94.6
92.7
64.3
Near
Exh. Line?
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Vapor
Return
Line?
N
-'
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Type
IV
IV
I
I
I
IV
IV
I
1
IV °
I
IV
IV
II .
VI
III
III
III
-------
APPENDIX NO. 1-3
SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE CONTROL
F = Full Size
I = Intermediate
C = Compact
Make
Chevrolet
Vega
Monza
Pontiac
Yr.
75
74
73
75
75
74
73
73
74
75
73
75
75
74
73
73
73
75
75
75
Model
C
I
I
F
F
F
F
F
F
C
C
C
C
F
I
F
F
F
F
F
Displ.
Litres
4.10
4.10
4.10
5.74
5.74
6.56
5.74
6.56
5.74
2.29
2.29
2.29
2.29
4.10
5.74
6.56
6.56
6.56
6.56
6.56
# of
Bbls.
1
1
1
2
4
4
4
2
2
2
1
2
2
1
2
2
4
4
4
2
Canister Purge
234 Purge Line To:
Tube Tube Tube Valve? PCV Garb Air Cl.
/ Y /
/ Y /
/ Y /
/ N /
/ N /
/ N /
/ N /
/ Y /
/ N /
/ Y /
/ Y /
/ N /
/ N /
/ N /
/ N /
/ N /
/ N /
Y v
Y v
/ /
Fuel Tank
Litres
79.5
79.5
83.3
83.3
83.3
98.4
98.4
98.4
83.3
60.6
41.6
70.0
70.0
95
95
95
95
95
95
95
Near
Exh. Line?
Y
Y
N
N
N
N
N
N
N
Y
Y
Y
Y
N
N
Y
N
N
N
N
Y
Y
X
Y
X
Y
Y
N
N
N
N
Y
Y
Y
Y
Y
II
II
II
I
I
I
IV
II
I
IV
II
I
I
I
I
I
I
I
I
IV
-------
APPENDIX NO. 1-4
SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE CONTROL SYSTEMS
F = Full Size
I = Intermediate
C = Compact
Displ.
Make
Cadillac
Olds
Buick
Yr.
73
75
73
73
74
75
75
74
75
75
73
73
73
75
75
Model
F
F
I
F
I
I
F
F
I
I
F
I
F
F
I
Litres
7
8
5
7
4
5
7
5
4
5
7
5
5
5
3
.74
.20
.71
.46
.10
.74
.46
.74
.29
.74
.46
.74
.74
.74
.80
Purge
Fuel
if of 2 3 4 Purge Line To:
Tank
Near
Bbls. Tube Tube Tube Valve? PCV Carb Air Cl. Litres Exh. Line?
4 /
4 vx
4 /
4 /
1 / v
4 /
4 /
2 /
2 /
4 /
4 /
2 /
4 /
4 / y
1 /
/ 102
v 104
/ 83
/ 79
f / 79
/ 83
/ 98
/ 83
/ 91
/ 98
/ 98
/ 83
/ 98
' / 98
/ 98
.3
.5
.5
.3
.4
.3
.0
.4
.4
.3
.4
.4
.4
N
N
N
N
Y
N
N
N
N
N
N
N
N
N
N
Vapor
Return
Line?
N
Y
N
Y
N
N
Y
Y
Y
Y
Y
Y
Y
Y
N
Type
I
IV
I
I
II
IV
IV
III
I
I
I
I
III
II
I
I
NJ
-------
APPENDIX NO. 1-5
SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE EMISSION CONTROLS
Purge Fuel Tank
Make
VW
Fiat
Opel
Mitsubishi
Peugeot
Volvo
Datsun
British
Ley land
Toyota
Audi
BMW
Honda
Yr.
73
75
75
75
75
74
75
73
74
74
75
74
75
74
75
74
75
Model
Bug
Bug
Rab.
1800
1300
Manta
Colt
504
I
210
MG
Displ.
Litres
1.5
1.6
1.5
1.8
1.3
1.9
2.0
1.97
1.98
2.1
1.8
2.6
2.6
1.5
1.5
2.0
1.5
7? of
Bbls.
1
1
1
1
1
1
2
2
F.I.
2
2
2
2
2
2
2
2
234 Purge Line To:
Tube Tube Tube Valve? PCV Garb Air Cl. Litres
/ / 40 . 1
/ / 40 . 1
/ /
/ / 45
/ /
/ /
/ / 59.8
Crankcase Storage / 43.9
/ / 53
/ / 45
/ / 45
/ / 45
/ / 45
/ / 72
/ / 41.7
Near
Exh. Line?
N
N
N
N
N
Y
N
N
N
N
N
Y
Y
N
Vapcr
Returr.
Line:
N
N
Y
Y
N
Y
N
N
N
N
N
N
N
III
I
-
Ill
I
I
VIII
II
II
II
III
III
I
I
Mazda
Mercedes-Benz
A condenser tank in trunk collects and condenses
tank vapors. Excess vapor from condenser tank
goes to PCV valve then to atmosphere. Carburetor
vapors stored in induction system.
A compensating tank and a combination valve
fiVfifpTn rondemsfi vanors and store excess in the
-------
APPENDIX NO. 1-6
SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE EMISSION CONTROLS
Purge Fuel Tank
Make
Ford
Inter-
national
Yr.
75
74
73
74
Model
F250
FIDO
Travail
Travail
Displ. // of
Litres Bbls.
4.92 1
3.93 1
5.65
6.56
234 Purge Line To:
Tube Tube Tube Valve? PCV Carb Air Cl. Litres
/ ' / 72.5
/ / 72.5
/ / 79.5
/ / 79.5
Near
Exh. Line?
N
N
N
N
Vapor
Return
Line?
N
N
N
N
Type
III
III
V
V
Dodge
75 Van
87.1
N
N
V
Chevrolet, Dodge, Plymouth and Ford light trucks same as cars.
-------
- 65 -
APPENDIX II
Inspections
Reid Vapor Pressure
(2)
Distillation
for ind. D 4- L
IBP
5
10
15
20
30
40
50
90
FBP
Temp.
VOLATILITY INSPECTIONS FOR
TEST FUELS
Indolene
Unmodified Cars
62.1 kPa
(9.0 psi)
36.1°C (97°F)
48.9°C (120°F)
55.6°C (132°F)
62.8°C (145°F)
69.4°C (157°F)
82.2°C (180°F)
93.9°C (201°F)
105. 0°C (221°F)
158. 9°C (318°F)
211. 7°C (413°F)
Modified Cars
62.1 kPa
(9.0 psi)
33.3°C (92°I
46.7°C (116°I
54.4°C (130°I
62.8°C (145°I
70.6°C (159°I
86.1°C (187°I
97.8°C (208°I
105. 6°C (222°I
161. 7°C (323°t
206. 1°C (403°P
High
Fuel
71.7 kPa
(10.4 psi)
31.1'C (88°F)
43.3°C (110°F)
52.2°C (126°F)
61.1°C (142V)
70.0°C (158°r)
86.
97.
105.6°C (222°F)
161.7°C (323°F)
206.1°C (403°F)
1°C (187°F)
8°C (208°F)
(1) This fuel prepared for the wok presented in part VI of this report.
(2) ASTM Designation D-86.
-------
- 66 -
APPENDIX III
PROCEDURE FOR QUANTIFYING EVAPORATIVE LOSSES
The procedure for quantifying losses involves collecting the
vapors and adsorbing them on activated carbon. This is carried out in
such a manner as to minimize the disturbance of the flow of hydrocarbon
from the leak source. Vapors are drawn into the collector at a care-
fully controlled flow rate. They pass through a dryer and then into
the carbon bed. Non-adsorbed sample is returned to the shed. Provi-
sion is made to check the sample leaving the carbon bed for the presence
of non-adsorbed vapors. A sketch of the equipment is shown in Figure I.
The flow rate in the collector is critical. Too high a rate
will lead to excessive losses from the leak source. Too low a rate
will allow vapors to escape into the shed. The range of operable rates
is 2.5 to 25 cfh. (71 to 710 L/h). The low rate is effective for 1.0
g/hr or less and the higher rate for 10+ g/hr. The collector flow rate
is matched to the source loss rate. If the F.I.D. trace for a hot soak
shows a high loss rate for the first fifteen minutes of a run followed
by a low loss rate the remainder of the soak, the collector flow rate
is set high for 15 minutes and then lowered.
For most vehicles, the collection equipment can be installed
prior to the run so as to minimize the length of time the hood is open
during a run. Small leaks in the air cleaner are sealed before the test,
The carbon for the collector is activated, non-polar carbon
of 10-20 mesh. It is dried prior to use. Volume of carbon is varied
with the amount of vapor to be collected.
-------
Vehicle
Canister
(Open Bottom)
- 67 -
APPENDIX III
FIGURE I
EQUIPMENT FOR QUANTIFYING EVAPORATIVE LEAKS
Equipment
Flexible
Tubing
Drierite
Dryer
Flow to
Rotameter
Vapor
Collectoi
From Vapor
Collector
Rotameter
In
Pump
Controls
SHED
I
-------
APPENDIX IV
TABLE I
SUMMARY OF EVAPORATIVE EMISSION DATA
Test
1) SHED #2
2) Quantifying #1
3) Quantifying #2
4) Quantifying #3
5) SHED #3
Make:
Year:
No.:
Ford LTD
75
1
Displ. cu. in./Litre: 351/5.75
No. Cyl.: .8
No. Venturis: 2
Diurnal, Grams
Loss From
SHED A.C.
2.66
0.12
0.08
0 . 18
4.21
Canister
__
3.06
1.27<2>
4.01
—
Other
— —
—
—
Hot Soak, Grams
SHED
3.56
0.48
0.48
1.50
2.90
A.C.
—
0.0
0.0
0.82
__
Loss From
Canister
__
2.94
0.92(2)
3.42
__
Other
__
—
—
__
Background
Total Grams
Grams Cold Hot
6.22
6.60
2.75
9.93
7.11
Remarks
0.74<1)1.39(1)
(2)
(3)
en
I
(1) High background due to fuel contamination on floor carpet. A fuel can had been placed on the floor of the vehicle
as an auxiliary fuel tank after SHED Test #3. Spillage from this can occurred some time prior to the background
test which was run after the SHED testing.
(2) Heated air tube from exhaust manifold inadvertently closed off at air cleaner snorkel during this run. Postulated
that the increase in pressure drop in the air cleaner purged the canister to a greater extent than for a normal run.
(3) Flow rates to collector hydrocarbon beds too high for this run. This tends to pull vapors from air cleaner and
canister.
-------
APPENDIX IV
TABLE II
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Pontiac
Year: 75_
No.: _2
Displ. cu. in./Litre: 400/6.56
Diurnal, Grams
(1)
(2)
(3)
(4)
(5)
Test
SHED #1
SHED #2
Quantifying
Quantifying
Quantifying
SHED A.C.
#1
#2
#3
0
0
0
0
0
.41
.37
.46
.41
.20 0.22
Loss From
Canister
__
—
0.20
0.45
0.19
Hot Soak, Grams
Other SHED A.C.
6
7
— — 1
1
1
.83
.40
.77(2)
.95(2)
.61<2>
—
3.62
4.60
4.80
Loss From
Canister Other
— — «_
— __
__0) 1>77(2)
0.23 1.95(2)
0.35 1.61(2)
Total
Grams
7.24
7.77
6.05
7.64
7.37
Background
Grams
Cold Hot Remarks
0.50(1) 0.84(1)
(1) Results from the background tests very high. A fuel can had been used in the vehicle after the SHED testing. Spillage
from this can contributed to high background test which was run after the SHED testing.
(2) Carburetor leak around accelerator pump shaft. Vapors escaped to the SHED because the leak is unaccessible from a
quantifying standpoint.
(3) Collector for hydrocarbon inadvertently omitted.
-------
APPENDIX IV
TABLE III
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Chrysler NYer
Year: _75_
No. : 3_
Displ. cu. in./Litre: 440/7.21
No. Cyl.: j3
No. Venturis: 4
Diurnal, Grams
Test
(1) Quantifying #1
(2) Quantifying #2
(3) Quantifying #3
(4) SHED #2
(5) SHED #3
SHED
0.08
0.32
0.17
7.30
8.63
A.C.
0.0
0.0
0.0
—
—
Loss From
Canister Other
6.46
3.50
3.88
—
—
Hot Soak, Grams
Loss From
SHED A.C. Canister Other
2.10(1) 0.0(2)
1.34(1) 0.32<2)
CD (2)
2.01V 0.0
10.63
7.76
0.0(2) 2.10(1
0.0(2) 1.34(1
0.0(2) 2.01(1
—
—
Background
Total Grams
Grams Cold Hot Remarks
5 8.64( 0.03 0.13
•> 5.48<2>
•> 6.06<2>
17.93
16.39
o
I
(1) Carburetor leak - vapors escape from around carburetor accelerator pump shaft as it passes through the air horn.
Vapors escape to the shed because the leak is unaccessible from a quantifying standpoint.
(2) Carburetor bowl maximum temperature during the hot soak is 15 to 20°F (-9.4 to -6.7°C) lower for quantifying runs
than regular SHED tests. This is because hood must be raised to attach hydrocarbon collection equipment when
quantifying; consequently, less hydrocarbon is lost from the carburetor bowl.
-------
APPENDIX IV
TABLE IV
SUMMARY OF EVAPORATIVE EMISSION DATA
Make:
Year:
No. :
Pinto
_74
4
Displ. cu. in./Litre: 122/2.0
No. Cyl.: _4
No. Venturis: 2
Diurnal, Grams
(1)
(2)
(3)
(4)
(5)
Test
SHED #1
SHED #2
Quantifying //I
Quantifying #2
SHED #3
SHED
2.31
1.50
0.16
0.33
1.82
A.C.
__
—
0.0
0.0
__
Loss From
Canister
__
—
0.50
0.0
-.—
Other
__
—
—
—
^_
Hot Soak, Grams
Loss From
SHED A.C. Canister Other
4.62
3.95
0.34
0.32
4.39
Background
Total Grams
Grams Cold Hot Remarks
6.93
5.45
1.0
0.65
6.21
0.0 0.16
(1) Carburetor bowl maximum temperatures are 8 to 12°F (-13.3 to -11.1°C) lower for quantifying runs than for bHLU tests.
This is due to heat loss from engine compartment when hood is raised to attach collection equipment for quantifying
runs.
-------
APPENDIX IV
Test SHED
(1) SHED #1 0.39
(2) SHED #2 0.58
(3) Quantifying #1 0.15
New Carburetor Installed
(4) SHED #3 0.28
(5) Quantifying #2 0.25
(6) Quantifying #3 0.28
(7) SHED #4 0.25
TABLE V
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Nova
Year: 74
No.: 5
Displ. cu. in. /Litre: 250/4.1
No. Cyl. : 6
No. Venturis: _ _1
Diurnal, Grams Hot Soak, Grams Background
Loss From Loss From Total Grams
A.C. Canister Other SHED A.C. Canister Other Grams Cold Hot
- 15.10 - 15.49 0.0 0.11
11.40 - 11-98
0.43 0.32 - ' 6.95<2> 0.71 0.13 6.95(2) 8.67<3)
10.04 - 10.32
0.56 - 5.96(2) 1.11 0.0 5.96<2) 7.88(4)
2.20 - 5.60<2) 5.81(A) 1.82 5.60(2) 15. 71<4>
11.35 - - - 11.60
•
Remarks
(1)
(2)
(2)
(1) Carburetor to intake manifold bolts tightened after this run.
(2) Carburetor leaks - the carburetor bowl is vented to the atmosphere upon slight pressure increase in the bowl. Other
leaks occurred around the accelerator pump shaft. Unable to Quantify carburetor leaks consequently, vapors enter shed.
(3) Hot soak losses lower on quantifying runs 1 and 2 than SHED tests because of lower maximum carburetor bowl tempera-
tures. Raising the hood to attach the vapor collection equipment lowered bowl temperature 20°F (-6.7°C).
(4) For this run, vapors from the external vent were collected along with vapors from air cleaner snorkel. The collecting
system pulled HC from the bowl due to too high a flow rate.
-------
APPENDIX IV
TABLE VI
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Chevrolet Impala
Year: 74
No . : 6
Displ. cu.
No. Cyl. :
in. /Litre: 350/5.74
8
No. Venturis: 2
(1)
(2)
(3)
(4)
(5)
Test
SHED #1
SHED #2
Quantifying #1
Quantifying #2
SHED #3
Diurnal, Grams
Loss From
SHED A.C. Canister Other
0.28 -
0.82 -
0.11 - 2.97(2)
0.21 - 2.80(2)
0.41 -
Hot Soak, Grams
Loss From
SHED A.C. Canister Other
4.69 -
4.09 -
0.56 7.36(2) 1.71(2)
0.52 7.70(2) 1.61(2) -
5.56 -
Background
Total Grams
Grams Cold Hot Remarks
4.97 (1) (1)
4.91
12.71(2)
12.84<2>
5.97
(1) Background tests for this car were extremely high because of fuel spillage on carpet floor. A fuel can had been
used as an auxiliary fuel tank after SHED Test #3. Background tests (3+ grams hot and cold) were run after SHED
testing.
(2) Collection system pulled vapors from the canister and air cleaner snorkel during the quantifying runs due to too
high a flow rate.
-------
APPENDIX IV
Test
(1) SHED #1
(2) SHED #2
TABLE VII
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Plymouth Duster
Year: 74
No.: 7_
Displ. cu. in./Litre: 225/3.69
No. Cyl.: 6_
1
No. Venturis:
Diurnal, Grains
Loss From
SHED A.C. Canister Other
0.50
0.44
SHED
0.73
1.32
Hot Soak, Grains
Loss From
A.C. Canister Other
Total
Grams
1.23
1.76
Background
Grams
Cold Hot
Remarks
0.66^ 0.73(1)
JS
I
(1) Background results are abnormally high because of gasoline spillage on carpet floor of vehicle from a fuel car.
after completion of SHED tests and before running the background tests.
-------
APPENDIX IV
Test
(1) SHED #1
(2) Quantifying #1
(3) Quantifying #2
(4) Quantifying #3
(5) SHED #2
TABLE VIII
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Buick LeSabre
Year: 75
No.: 8
Displ. cu. in. /Litre: 350/5.74
Diurnal, Grams Hot Soak, Grams Background
Loss From Loss From Total Grams
SHED A.C. Canister Other SHED A.C. Canister Other Grams Cold Hot Remarks
0.90 - 5.16 - 6.06 0.06 0.29
0.20 - 1.88(1) - 1.40(2)6.52(1) 2.13(1) 1.40(2) 12.13(1) '
0.33 - 1.68(1) - 2.58(2)3.39 0.49 2.58(2) 8.47(1) i
0.21 - 1.56(2)4.57 0.0 1.56(2) 6.02
0.57 - 7.34 - 7.98
(1) Hydrocarbon collecting equipment rate too high. Some HC drawn from canister and air cleaner.
(2) Carburetor leak - carburetor accelerator pump shaft and collar on air horn a very loose fit. No feasible way to trap
this leak.
-------
APPENDIX IV
TABLE IX
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Vega
Year: 75
No.: 9_
Displ. cu. in./Litre: 140/2.29
(1)
(2)
(3)
(4)
(5)
Test
SHED #1
Quantifying #1
Quantifying #2
Quantifying #3
SHED #2
Diurn
SHED A.C.
0.
0.
0.
0.
0.
33
23
18
30
21
al, Grams
Loss From
Hot Soak, Grams
Loss From
Canister Other SHED A.C. Canister Other
3.
0.
0.
o.
5.
49 -
45 7.17(1)
50 0.25(2)
35 0.16(2)
46 -
Background
Total Grams
Grams Cold Hot Remarks
3.82 0.0 0.57
7.85<1'2)
0.93(2)
0.81<2>
5.67
(1) Vapor collection rate too high in this case.
(2) Carburetor bowl temperatures are 15 to 20°F (-9.4 to -6.7°C) lower for quantifying runs than for SHED tests.
was partially open to accommodate vapor collection equipment.
CN
I
Hood
-------
APPENDIX IV
TABLE X
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Olds "98"
Year: 73
No.: 10
Displ. cu. in./Litre: 455/7.46
Diurnal, Grams
Hot Soak, Grams
Background
(1)
(2)
(3)
(4)
Test
SHED //I
Quantifying #1
Quantifying #2
SHED #2
Loss From Loss From Total Grams
SHED A.C. Canister Other SHED A.C. Canister Other Grams Cold Hot Remarks
0.49 - 9.11 - 9.60 0.15 0.31
0.41 - 1.69^ 6.92 0.0 1.69^ 9.02
0.25 - 1.67(1) 6.78 0.0 1.67(1) 8.70
0.43 - 9.98 - 10.41
(1) Carburetor leak around accelerator pump shaft. Vapors escaped to the shed because the leak is unaccessible from
a quantifying standpoint.
-------
APPENDIX IV
Test SHED
(1) SHED #1 0.20
Carburetor" to air cleaner
(2) SHED n 0.73
(3) Quantifying #1 0.13
(4) Quantifying #2 0.12
(5) Quantifying #3 0.18
(6) SHED #3 0.22
TABLE XI
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Hornet
Year: 74
No . : 11
Displ. cu. in. /Litre: 232/3.80
Diurnal, Grams Hot Soak, Grams Background
Loss From Loss From Total Grams
A.C. Canister Other SHED A.C. Canister Other Grams Cold Hot Remarks
- - - 12.33 - 12.53 0.0 0.11
gasket replaced. Original one cracked and leaking.
- - - 10.11 - 10.84
6.73(1)19.10<2) - 6.73(1) 25.96(2)
6.52(1) 4.57 - 6.52(1) 11.21
6.95(1) 4.23 - 6.95(1) 11.36
- - - 10.54 - 10.76
I
00
(1) Carburetor leak around accelerator pump shaft. Vapors escaped to shed as leak is unaccessible from a quantifying
standpoint.
(2) Flow of hydrocarbon vapors to collector too high.
-------
APPENDIX IV
TABLE XII
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Plymouth Fury III
Year: 73
No.: 12
Displ. cu. In./Litre: 360/5.90
Diurnal, Grams
Hot Soak, Grams
(1)
(2)
(3)
(4)
Test
SHED #1
Quantifying //I
Quantifying #2
SHED #2
SHED A.C.
4.61
1.31
0.86
3.50
Loss From
Canister Other
-
2.70
1.45<2> -
_ _
Loss From
SHED A.C. Canister Other
2.79 -
2.00(1) 0.0 2.41 2.00(1)
1.70(1) 0.0 1.65(2) ^0(1)
2.26 -
Total
Grams
7.40
8.42
5.63(2)
5.76<3)
Background
Grams
Grams Cold Hot Remarks
0.07 0.66
(1) Carburetor leak around accelerator pump shaft. This loss inaccessible from a quantifying standpoint.
(2) Run No. 3, Quantifying Run #2 is 3.0 grams lower than Quantifying Run No. 1 because the charcoal canister adsorbed
3.0 grams more for the second run. The hydrocarbon level in the canister decreased from Run #1 to Run #2.
(3) The total loss for SHED Test 2 is less than for SHED Test 1 because the working capacity of the canister has increased
during this series of tests. This is indicated by lower canister weights for SHED Test 2 than 1.
-------
APPENDIX IV
TABLE XIII
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Dart
Year: 74
No.: 13
Displ. cu. in./Litre: 318/5.21
Diurnal, Grams
Hot Soak, Grams
Background
Loss From Loss From
(1)
(2)
(3)
(4)
Test
SHED #1
Quantifying #1
Quantifying #2
SHED #2
SHED A.C. Canister
0.16
0.13
0.29
0.18
Other SHED A.C. Canister Other
2.85
1.33*1) 1.82
1.30(1) 1.57
2.57
-
1.33^
1.30^
-
Total Grams
Grams Cold Hot Remarks
3.01 0.0 0.11
3.28
3.16
2.75
00
o
(1) Carburetor leak - hydrocarbon leak around accelerator pump shaft.
-------
APPENDIX IV
TABLE XIV
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Datsun
Year: 74
No.: 14
Diurnal, Grams
Hot Soak, Grams
Test
(1) SHED //I
(2) Quantifying #1
(3) Quantifying #2
(4) SHED #2
1.25
0.53
0.79
0.90
Loss From
SHED A.C. Canister Other
0.0
0.58
SHED
2.19
1.57
1.21
1.80
Loss From
A.C. Canister Other
0.0
0.0
Total
Grams
3.44
2.10
2.58
2.70
Background
Grams
Cold Hot Remarks
0.11 0.20
i
oo
-------
APPENDIX IV
TABLE XV
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Mazda
Year: 74
No.: 15
Displ. cu. in./Litre: Rotary
Diurnal, Grams Hot Soak, Grams Background
Loss From Loss From Total Grams
CD
(2)
(3)
(4)
Test
SHED #1
Quantifying #1
Quantifying $2
SHED -72
SHED A.C.
0.54
1.36
0.51
0.86
Canister Other SHED A.C. Canister
11.56
1.36(2) 7.79(3) _
1.13(2) 7.60(3) -
11.44
Other Grams Cold Hot
12.10 0.46(1) 1.10(]
1.36(2) 10.5l(3)
1.13(2) 9.24(3)
12.30
Remarks
-)
i
oo
N5
(1) Evidence of gasoline spillage in the trunk prior to this work. This would account for high background.
(2) Carburetor leaks.
(3) Carburetor bowl temperatures 12-15°F (-11.1 to -9.4°C) lower for quantifying runs than SHED tests because hood
was partially open during the hot soak to accommodate the collection equipment.
-------
APPENDIX IV
TABLE XVI
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Comet
Year: 74
No.: 16
Displ. cu. in./Litre: 250/4.10
Diurnal, Grams
Hot Soak, Grams
Background
Loss From Loss From Total Grams
(1)
(2)
(3)
(4)
(5)
Test
SHED #1
Quantifying #1
Quantifying #2
SHED #2
SEED #3
SHED A.C. Canister
0.21
0.16
0.50
2.120) _
0.17
Other SHED A.C. Canister Other Grams Cold Hot Re-arks
20.33 - 20.54 0.0 0.12
2.65(1) 11.44 - 2.65(1) I4.2s(2) i
0
14.49 - 17.6l(2)
14.08 - 14.25(2)
(1) Carburetor leak around accelerator pump shaft. Inaccessible from a quantifying standpoint.
(2) Several openings in the air cleaner sealed after SHED Test #2 which accounts for the lower total emissions for
these runs than SHED 7/1.
(3) Tank drain disconnect fitting leaking during diurnal cycle.
-------
APPENDIX IV
Test
(1) SHED #1
(2) Quantifying #1
(3) Quantifying #2
(4) SHED #2
(5) SHED #3
TABLE XVII
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Volvo
Year: 74
No,: 17
Displ. cu. in. /Litre: 121/1.98
Diurnal, Grams Hot Soak, Grams
Loss From Loss From
SHED A.C. Canister Gas Cap SHED A.C. Canister
6.54 - 4.97
2.89 0.37 0.19 1.34 ^ 1.63 1.87 0.0
0.77 0.60 0.32 2.33(1) 1.24 3.77 0.30
4.87 - 3.84
4.49 - 2.62
Gas Cap
0.40<1}
1.17(1>
Background
Total Grams
Grams Cold Hot
Remarks
11.51 0.09
(2)
0.12
8.69
i
00
10.50
8.31
(2)
<2>
(1) Fuel tank pressure builds up quickly to 1.0+ psig during diurnal cycle and is relieved through the fill cap or
any other fittings that may leak temporarily. Fuel tank pressure is 1.0+ psi (6.9+ kPa) at beginning of the
hot soak also. Tank temperature increases 9-10°F (-15.0 to -14.4°C) during Federal cycle.
(2) After SHED test //I (before Quantifying #1 run), the clamps for the flexible portion of the fill pipe were tightened
to eliminate a leak. Consequently, subsequent runs are lower in total evaporative emissions.
-------
Test
(1) SHED //I
(2) Quantifying ill
(3) Quantifying #2
(4) SHED //2
(5) SHED #3
SHED
3.70
0.51
0.50
0.56
1.07
APPENDIX IV
TABLE XVIII
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Ford
Year: 75
No . : 18
Displ. cu. in. /Litre: 460/7.54
Diurnal, Grams Hot Soak, Grams
Loss Fro;?. Loss From
A.C. Canister Other SHED A.C. Canister Other
31.15 -
2.23 - 14.04(2) 4.90 2.13 14. 04<2)
15.29^2) 4.38 0.98 15.29(2>
- 25.75 -
29.84 -
Background
Total Grams
Grams Cold Hot
34.85CD 0.0 0.13
23.81
21.15
26,31
30.91
I
00
(1) Losses higher for this run than subsequent runs because of leaks in the air cleaner. These were sealed for quantifyiv
and later SHED tests,
(2) Carburetor leaks - vapors escape around the linkage for the choke plate and bowl vent to the canister,
-------
APPENDIX IV
TABLE XIX
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: VW
Year: 75
No.: 19
Displ. cu. in./Litre: 97/1.6 (Fuel Injected)
Diurnal, Grams
Hot Soak, Grams
(1)
(2)
(3)
Test
SHED #1
SHED #2
SHED #3
Loss From
SHED A.C. Canister Other
0.56 -
1.15 -
0.41 -
SHED A.C.
1.43
1.46
1.14
Loss From
Canister Other
-
^ — .
Background
Total Grams
Grams Cold Hot Remarks
1.99 0.69(1) 0.80(1)
2.61
1.55
I
oo
(1) To verify the high background levels for this car, emissions were monitored for 24 hours. For both hot and cold
background tests, the rate of hydrocarbon emission had not diminished significantly after 24 hours. Further
testing showed that essentially all of the hydrocarbon was being emitted from the outside of the vehicle.
-------
APPENDIX IV
TABLE XX
SUMMARY OF EVAPORATIVE EMISSION DATA
Make: Monarch
Year: 75
No.: 20
Displ. cu. in./Litre: 302/4.95
(1)
(2)
(3)
(4)
(5)
Test
SHED #1
Quantifying #1
Quantifying #2
SHED #2
SHED #3
Diurnal, Grams
Loss From
SHED A.C. Canister Other
4.41 -
0.38 - 2.28
0.35 - 1.34
0.91 -
1.09 -
Hot Soak, Grams
Loss From
SHED A.C. Canister Other
6.30 - - -
3.94(1) 1.86 - 3.94(1)
3.26(1) 2.48 - 3.26(1)
8.62 -
6.51 -
Background^
Total Grams
Grams Cold Hot Remarks
10.71 0.0 0.0
8.46
7.43 !
9.53
7.60
(1) Carburetor leak around choke plate linkage.
-------
APPENDIX V
TABLE I
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make: Ford "LTD"
Year: 75
No.: 1_
Displ. cu. in./Litre: 351/5.75
Evap. Emissions,
Modifications g/SHED Test Remarks
I.a. Purge from inside air cleaner element.
b. Barrier in air cleaner at base of snorkel. 6.1
c. Choke shaft passage sealed.
II. Steps a, b, c
d. Air horn to body gasket modified to allow more bowl 9.6
vapors to be stored in air cleaner.
IlI.e. Purge to air cleaner snorkel as well as air cleaner.
Measurements were made of purge rates for both an air cleaner and a snorkel purge system. Next, a curve
of grams removed from canister vs. total purge volume was made. From these data it was estimated that a
combination air cleaner-snorkel purge system would remove 13 to 15 grams from the canister during the SHED
preconditioning period (4-LA-4s). This is not an adequate system because the combined diurnal and hot soak
input to the canister is about 23 grams for the modified vehicle. Consequently, a PCV purge system was installed
using a 1974 Vega canister which had been in daily usage up to this time.
IV. PCV purge with Vega canister. The bottom of the 1.3
canister is capped. An unmodified carburetor body 1.2
to air horn gasket used along with modifications
b and c above.
-------
APPENDIX V
TABLE II
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make: Pontiac
Year: 75
No. : 2_
Displ. cu. in./Litre: 400/6.56
Modifications
I.a. Vented carb. bowl to canister.
b. Sealed leak around accel. pump shaft.
II. Steps a and b
c. Restriction in line from bowl to canister.
III. Steps a, b, c
d. Underhood ventilated with a fan.
e. Bottom on canister
Evap. Emissions,
g/SHED Test
10.5 (diurnal)
3.4
1.6
2.5
1.7
Remarks
Canister dried up before run.
Fan lowers carb. bowl temp.
about 30°F (-1.1°C).
CO
VO
-------
APPENDIX V
TABLE III
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Displ. cu. in./Litre: 440/7.21
Modifications
I.a. Underhood ventilated with fan.
b. Garb, bowl volume lowered
c. Barrier installed at base of a.c. snorkel.
d. Accel, pump shaft leak sealed.
Evap. Emissions,
g/SHED Test
10.8 (diurnal)
12.0 (diurnal)
Remarks
Fan only lowered c.b. temp.
5-15°F. Not blowing directly
at carburetor.
II. At this point it was determined that one canister would not have sufficient capacity to handle total evap.
emissions. With a single canister, preconditioning removes 36-40 grams from a fully charged canister. The
last LA-4 removes only 1 to 2 grams. Combined diurnal and hot soak losses are 50 grams. A Chrysler canister
from a 1975 vehicle in daily usage was used as a second canister.
e.
f.
g-
Two canisters installed in parallel. ]
Second carb. bowl vented directly to canisters, t
Bottom installed on canisters. /
Steps b, c, and d above also used ]
2.1
2.5
(D
(D
o
i
(1) Exhaust emission data were very erratic. Inasmuch as this vehicle had to be returned to the rental agency, a
second car will be obtained for further tests.
-------
APPENDIX V
TABLE IV
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make:
Year
No.: 21
Chrysler
75
Displ. cu. in./Litre: 440/7.21
Modifications
I Original ECS
Original ECS
Evap. Emissions,
g/SHED Test
13.4
14.6
Remarks
Diurnal - 6.3 g, H.S. - 7.1 g
Diurnal - 4.4 g, H.S. - 10.2 g
II Modified ECS:
(a) Two canisters in parallel used
(b) Second carb. bowl vented directly to canister
(c) Bottom on each canister
(d) Barrier at base of snorkel
(e) Accel, pump shaft leak sealed
1.9
2.0
-------
APPENDIX V
TABLE V
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make: Hornet
Year: 74
No.: 11
Displ. cu. in./Litre: 232/3.80
Modifications
I.a. Garb, bowl vented to the canister.
b. Accel, pump shaft leak sealed.
II. Steps a and b above - restriction in line from carb.
bowl to canister.
c. Barrier installed in air cleaner at base of snorkel.
III. Steps a, b, c above
d. Bottom of canister closed.
IV. ECS modified to a PCV purge system using a 1974 Vega
canister. Steps a, b, c, and d above also continued.
Evap. Emissions,
g/SHED Test
3.9
3.1
2.5
1.2
1.3
Remarks
NJ
I
-------
APPENDIX V
TABLE VI
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Step
I
II
III
IV
Make: Mazda
Year: 74 '
No.: 15
Modifications
Displ. Cu In./Litre: 80/1.31 (Rotary)
Evap. Emissions
g/SHED Test
Remarks
Both carburetor bowls vented to 4.8, 3.8
a 3 tube canister (Chrysler).
Purge is through existing purge
line to PCV. Original ECS used
for diurnal.
Next, the modifications indicated below were tested.
SHED test exceeded 2.0 grams.
Hydrocarbon vapors escaping from
snorkel.
In each case, the hydrocarbon level from the
1. Canister moved outside of engine compartment to a cooler environment.
2. Canister dried up on vacuum pump prior to diurnal and hot soak.
3. Air cleaner canister closed off and 3 tube canister used for both diurnal and hot soak.
At this point, additional source determination tests indicated hydrocarbon vapors emanating from
carburetor throat due to fuel drippage. To alleviate pressure in the carburetor bowl, a fan
installed to lower bowl temperature by ventilating the underhood engine compartment.
U)
I
Modifications for Step I.
Underhood fan to ventilate
underhood.
2.8
At this point, the 3 tube canister was changed to a 4 tube Vega with a purge control valve. (Used
canister from 1974 Vega.) High diurnal losses in above runs due to tank vapors passing into engine
crankcase, then through PCV purge line into 3 tube canister. Vapors then moved out of the canister
into the carburetor bowl and air cleaner through the vent line from the bowl to the canister. The
purge control valve prevents this migration of vapors into the carburetor bowl and air cleaner.
Modifications for Step I with
exception of replacing 3 tube
canister with a 4 tube unit.
1.8, 1.3
Fan to ventilate underhood.
-------
APPENDIX V
TABLE VII
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make: Volvo
Year: 74
No.: 17
Displ. cu. in./Litre: 121/1.98
Modifications
I.a. Equalizing valve modified so as to relieve fuel tank
pressure at 0.5 psig.
b. Baffle installed between fuel tank and muffler.
c. American Motors canister used.
Evap. Emissions,
g/SHED Test
0.4
1.7
Remarks
CO and HC exhaust levels
higher with modified ECS,
-------
- 95 -
APPENDIX VI
ESTIMATED COSTS FOR VEHICLE MODIFICATIONS
Car
No.
1
Make
LTD
Modification
Canister replacement(1)
Seal-carb. leak
Barrier-snorkel base
Air cleaner sealing
Canister bottom cap
Total
Cost $
$ 1.00
0.30
0.20
0.30
0.20
$ 2.00
1'ont Ino
Bowl vent to canister
Sp.-il-r.-irb. I o.ik
CJIH (HI »T hoi 1 om r.ip
Mr r I c.inrr HIM I I ity.
Kan
$ 0.50
0.30
0. /><)
(I. 10
17,00(1 .00) (
$J8.
21
Chrysler
Canister replacement (3
Canister bottom caps
Bowl vent to canister
Barrier-snorkel base
Seal-carb. leak
Air cleaner sealing
Total
$ 4.00
0.40
0.50
0.20
0.30
0.30
$ 5.70
11
Hornet
Canister replacement
Seal-carb. leak
Bowl vent to canister
Air cleaner sealing
Canister bottom cap
Barrier-snorkel base
(4)
Total
$ 1.00
0.30
0.50
0.30
0.20
0.20
$ 2.50
15
Mazda
17
Volvo
Bowl vent to canister (two) $ 1.00
Canister 7.00
Fan 17.00
Canister bottom cap 0.20
Total $25.20
Canister Replacement/5) $ 1.00
Baffle between tank
and muffler 1.00
Total $ 2.00
(1) Price difference between 3 tube and A tube canister.
(2) Numbers in parenthesis are costs associated with the Vega canister
system.
(3) Price difference between original 3 tube canister and 3 tube with
50% larger capacity.
(4) Price difference between 2 tube and 4 tube canister.
(5) Price difference between 1 tube and 2 tube canister.
-------
- 96 -
APPENDIX VII
HIGH RVP FUEL IN SHED TEST
Fuel RVP: 71.7 kPa (10.4 psi)
I SHED Results
SHED Test, Grams
Car No. Make Total Diurnal
1 LTD 6.2 2.6
5.2 2.1
2 Pontiac 4.4 3.2
2.1 0.9
2.3 1.3
II Exhaust Emission Data
Grams /Mile ^
Car No. Make CO HC
1 • LTD 5.19 0.46
2 Pontiac 4.69 0.76
Hot Soak
3.6
3.1
1.2
1.2
1.0
NO
1.
1.
2L_
45
16
(1) Average of two tests.
-------
- 97 -
APPENDIX VIII
HIGH TEMPERATURE DIURNAL SHED TEST DATA
Diurnal Cycle: 15.6 - 35°C (60-95°F)
1 SUED Results
Car No.
Make
LTD
Pontiac
SHED Test, Grams
Total
4.8
4.0
4.2
3.7
Diurnal
1.9
2.3
3.2
2.4
Hot Soak
2.9
1.7
1.0
1.3
II Exhaust Emission Data
Car No.
1
• 2
Make
LTD
Pontiac
Grams/Mile
CO
5.28
3.83
HC
0.44
0.88
NOX
1.95
1.19
(1) Average of two tests.
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 "I I'OHI NO
KPA-460/3-76-014
/I I I II t /. M, vjfj TITLE
Investigation and Assessment of Light Duty Vehicle
Evaporative Emission Sources and Control
7 AUTHOH(S)
P. J. Clarke
9 PtRFORMING ORGANIZATION NAME AND ADDRESS
Exxon Research and Engineering Company
P. 0. Box 8
Linden, New Jersey
12 SPONSOHING AGLNCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Water Programs
Mobile Source Air Pollution Control
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
May 1976 (Approved)
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
1O. PROGRAM ELEMENT NO.
11. CONTRACTAS&SfclflXttfl.
68-03-2172
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
To be presented in the form of an APCA paper in June 1976 (Portland meeting).
16. ABSTRACT
"*' • -~,
This study has assessed the effectiveness of current Evapbrative Control Systems
(ECS) and has shown the feasibility of various hardware approaches which control
evaporative emissions to a very low level.
The performance of ECS's in current use was evaluated by using the Sealed
Housing for Evaporative Determinations (SHED) procedure on twenty 1973-75 cars with
representative control systems. The measured emissions ranged from 0.5 to 30.6 grams
per test, and the twenty car average was 8.7 grams per test.
Hardware was then developed to improve ECS performance. Six production vehicles
were modified to demonstrate the feasibility of improving current systems. These
modifications were successful in lowering the evaporative emissions to less than 2.0
grams per test for each of the six modified vehicles. This six car group consisted
of vehicles manufactured by General Motors, Ford, Chrysler, American Motors, Volvo
and Mazda; and the costs of required hardware has been estimated at $2, $2, $6, $2,
$2, and $25, respectively.
17.
a
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution
Motor Vehicles
Hydrocarbons
Air Pollution Control Equipment
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Held/Group
Evaporative Emissions
Light Duty Vehicle
Emission Control
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
20. SECURITY CLASS (Thispage)
21 NO. OF PAGES
-100
EPA Form 2220-1 (9-73)
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