P.1 

OAR Box 1818 

Prepped by Ollie Stewart 

Document Number: 

31) ll-D-4 

Docket Number: 

A-87-11 

Printed 11/6/2008 3:12:44 PM Sheet 31 of 79 
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VEHICLE ONBOARD REFUELING CONTROI 

API PUBLICATION NO. 4424 

HEALTH AND ENVIRONMENTAL SCIENCES DEPARTMENT 

MARCH 1986 

3 /'? 

<o. zv3 - . r. I T + • *> ~ ' - ''-"- - yy 

American Petroleum Institute 

1220 L Street, Northwest 

Washington, V.C. 20005 ri l 

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P.2 

i 

1 
PROGRAM OVERVIEW 

VEHICLE ONBOARD REFUELING CONTROL 

API Publication No. 4424 

INTRODUCTION 

This study is a supplement to the API onboard refueling 

program conducted in 1978.* It updates the earlier work by 

eguipping late model automobiles with onboard refueling vapor 

control systems, and verifying performance with gasoline more 

volatile than the norm of summertime commercial fuels. 

The 1978 API study outfitted four cars with refueling vapor 

control systems that consistently achieved over 96% control of 

refueling emissions. The current program, involving three cars, 

exceeded the"earlier results by attaining higher levels of 

control efficiencies. In addition, new safety components were 

developed, and the filling requirement was investigated to 

achieve simplification. 

RESULTS 

Refueling emission control efficiencies of 98+% were 

achieved on all vehicles under extreme summertime conditions of 

11.5 psi RVP gasoline dispensed at 88°F. 

Exhaust emissions were not affected by the onboard system on 

one car. Small increases in exhaust emissions of the other cars 

did not cause federal standards to be exceeded, except for carbon 

monoxide in the case of one car which did not meet that standard 

even before modification. These small increases could be 

eliminated through further optimization of the systems. 

Control of evaporative emissions was improved to the extent 

the present standard of 2.0 grams per test, prescribed for 9 psi 

RVP certification fuel, was met with a fuel of 11.5 psi RVP, a 

more volatile fuel than most commercial summer gasoline. 

No adverse effects on driveability were observed. 

The onboard systems are simple in design and construction, and 

should be readily adaptable to the usual automotive production 

methods. From the user's point of view, the act of refueling 

vehicles equipped with these systems should not be perceptibly 

different from refueling current vehicles. 

•"Onboard Control of Refueling Emissions, Demonstration of 

Feasibility", API Publication #4036, October, 1978. 
P.4 

PROGRAM FEATURES 

Three cars were studied: 

1. 1985 Buick Century with 3.8 liter V6 port fuel injected 

engine and 15.5 gallon fuel tank. 

2. 1985 Dodge 600 with 2.2 liter 4 cylinder throttle body fuel 

injected engine and 14 gallon fuel tank. 

3. 1984 Pontiac Parisienne with 5.5 liter V8 feed-back 

carbureted engine and 25 gallon fuel tank. 

The Pontiac was included in the study as an extreme case of 

potentially high refueling emissions. The large fuel tank, and 

short rear fillpipe on the vehicle, make it a more difficult 

tasks to achieve a high level of control efficiency. 

To prevent vapor loss during refueling, the system developed for 

the Buick has a liquid seal in the fillpipe provided by a 

U-shaped dip"in the pipe inside the fuel tank. Systems developed 

for the Dodge and Pontiac have no special sealing arrangements. 

They rely upon the flow of gasoline down the fillpipe to serve as 

a barrier to the escape of vapors out the production filler neck 

to the atmosphere. 

Two different safety valve alternatives were employed to close 

off the vapor line, and thus guard against fuel loss from the 

tank, should the car accidentally roll over. Also, fuel tank 

overfill prevention techniques that completely eliminate 

spit-back and spillage were developed. These systems are fully 

compatible with existing gasoline nozzles operating with 

automatic shut off. 

The EPA emissions test procedure proposed for onboard refueling 

controls was used in all cases. 

The following contractor reports present the details of this 

program. 
P.5 

DAN 86M-113 

ONBOARD CONTROL OF REFUELING EMISSIONS -

SYSTEM DEMONSTRATION ON A 1985 VEHICLE 

Report Prepared for the 

American Petroleum Institute 

Washington, D. C. 

By 

Mobil Research & Development Corporation 

Paulsboro, NJ 08066 

February 1986 

Prepared by: 

D. W. Lloyd 

W. J. Koehl 
P.6 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY 

INTRODUCTION 1 

Objective .... . 1 

Project Outline 2 

CHARACTERIZATION OF TEST VEHICLE BASELINE 2 

Test Vehicle 2 

Test Fuels 3 

Baseline Emissions and Test Methods 3 

- Exhaust and Evaporative Emissions 3 

Refueling Emissions .. . 4 

Tank Flow Characteristics 5 

ONBOARD SYSTEM DEVELOPMENT 6 

Carbon Canister 6 

Fillpipe Seal and Vapor/Liquid Separator Development .. . 6 

External Liquid Seal 7 

External Liquid Seal and Vapor/Liquid Separator ... . 8 

Internal Liquid Seal 8 

Production Fillpipe As Seal 8 

Mechanical Seal 9 

Vapor Vent/Rollover Valve 9 

Final Onboard System 10 

Installation oh Vehicle 10 

Refueling Emission Tests 10 

SELECTION OF CANISTER PURGE RATE 11 

FINAL SYSTEM TESTING - EPA PROPOSED CERTIFICATION TEST 12 

Effect of Fuel RVP on System Performance 13 

DISCUSSION 14 

Emission Control Performance 14 

Onboard System Design and Construction 15 

Fuel RVP Versus Canister Size 16 

Reducing Potential Emissions . . 17 

REFERENCES 18 

J 
P.7 

TABLE OF CONTENTS (CONTINUED) 

TABLES 

1 - Onboard Refueling Control System Test Car 

2 - Test Fuel Properties 

3 - Buick Century Baseline Emission Tests, Exhaust Emissions & 

Fuel Economy 

4 - Buick Century Baseline Emission Tests, Evaporative Emissions 

5 - Uncontrolled Refueling Emission Measurement Procedure 

6 - Buick Century Baseline Emission Tests, Uncontrolled Refueling 

Emissions 

7 - External Liquid Seal, Bench Tests 

8 - External Liquid Seal with Vapor/Liquid Separator, Bench Tests 

9 - Internal Liquid Seal with Vapor/Liquid Separator, Bench Tests 

10 - Production Fillpipe As Liquid Seal, Bench Tests 

11 - Mechanical Seal, Bench Tests 

12 r Refueling Tests with Complete Onboard System on Car 

13 .- Preliminary Canister Purging Experiments 

14 - Summary of Proposed EPA Certification Test Procedure 

15 - Final System Test Results - EPA Proposed Certification Test, 

Exhaust and Evaporative Emissions, 11.5 psi RVP Fuel 

16 - Purge Data - EPA Proposed Certification Test, 11.5 psi RVP 

Fuel 

17 - Refueling Test Results - EPA Proposed Certification Test, 

11.5 psi RVP Fuel 

18 - Final System Test Results - EPA Proposed Certification Test, 

Exhaust and Evaporative Emissions, 9.0 psi RVP Fuel 

19 - Final System Test Results - EPA Proposed Certification Test, 

Exhaust and Evaporative Emissions, 10.5 psi RVP Fuel 

20 - Purge Data - EPA Proposed Certification Test, 9.0 psi RVP Fuel 

21 - Purge Data - EPA Proposed Certification Test, 10.5 psi RVP Fuel 

22 - Refueling Test Results - EPA Proposed Certification Test, 10.5 

and 9.0 psi RVP Fuels 

23 - Effect of Test Fuel RVP on Canister Size 

24 - Potential Emissions Comparison 

FIGURES 

1 - Onboard Refueling Emission Control System 

2 - Buick Century Tank and Fillpipe - Production Configuration 

3 - Uncontrolled Refueling Emission Calculation 

4 - Bench Test Rig 

5 - Preliminary Onboard Canister, 8.0-Liter 

6 - Final Onboard Canister, 4.5-Llter 

7 - External Liquid Seal 

8 - External Liquid Seal with Vapor/Liquid Separator 

9 - Internal Liquid Seal 

10 - Mechanical Seal Bench Tests 

11 - Nozzle-Actuated Refueling Emissions Vapor Vent Valve 

12 - Onboard Fillpipe Assembly 

13 - Onboard Canister Mounted in Test Car 
P.8 

BCECUTIVE SUMMARY 

This report presents the findings of the Onboard Refueling Emission Control 

Project undertaken by Mobil Research and Development Corporation under 

contract to the American Petroleum Institute. Onboard refueling control 

technology has been successfully applied to a 1985 model vehicle meeting 

today's stringent exhaust and evaporative emission standards. Refueling 

emissions have been controlled with 98+% efficiency in tests with 9 to 

11.5 psi RVP fuel at 88°F. 

Applying the onboard refueling control system to the test vehicle—a 1985 

Buick Century with a 3.8 liter, fuel-injected V-6 engine, and a feedback 

controlled three-way exhaust emission catalyst—required the following 

modifications: (The system is shown schematically in Figure 1.) 

• The production 1.5-liter evaporative emission control canister was 

replaced by a 4.5-liter canister to collect both refueling vapors and 

evaporative emissions. The new canister of activated carbon was 

placed in the same underhood location as the production evaporative 

canister. 

• A liquid seal (similar to a sink trap) was placed in the tank fillpipe 

to. prevent escape of tank vapors during refueling. 

• The existing vapor vent line linking the tank to the canister was 

replaced by a larger line to accommodate the vapor flow during 

refueling without excessive back pressure. 

•. A vapor/liquid separator and a vapor vent valve were installed as an 

Integral part of the fillpipe without changing its location on the 

car. The vapor/liquid separator prevents passage of liquid fuel to 

the canister. The nozzle-actuated vapor vent valve, which is open 

only during refueling, is designed to satisfy the safety requirement 

for preventing fuel leakage in the event of a vehicle rollover 

accident. 

• The purge rate for the refueling canister was increased somewhat over 

that of the production evaporative control canister so that the 

canister could be regenerated sufficiently by driving between 

refuelings. This was done by using a larger flow control orifice. 

The onboard refueling emission control system was thoroughly tested according 

to a procedure proposed by the U.S. Environmental Protection Agency for 

possible use in certification testing of onboard systems. This testing 

showed that: 

• Refueling emissions were controlled with 98+% efficiency under severe 

test conditions using a typical 11.5 psi RVP gasoline dispensed at 

88°F and requiring automatic shutoff of a conventional nozzle when the 

tank is filled to capacity. 

• Control of evaporative emissions was improved to the extent that the 

present standard of 2.0 g/test prescribed for 9 psi RVP certification 

fuel was met with a fuel of 11.5 psi RVP, typical of commercial 

gasoline. 
_EL9 

EXECUTIVE SUMMARY (CONTINUED) 

• The refueling control canister can be purged faster than necessary to 

restore its capacity in the proposed EPA procedure and without any 

significant effect on exhaust emissions. 

In addition to meeting these performance goals, the system tested is 

compatible with existing gasoline dispensing nozzles and can be fueled at, at 

least, the same rate as the production vehicle. The system is simple in 

design and construction and should be readily adaptable to common automotive 

production methods and materials. No effects on vehicle driveability were 

observed. Durability testing was beyond the scope of the project, but none 

of the components present durability problems that have not been addressed in 

other automotive components. From the user's point of view, refueling a 

vehicle equipped with this onboard system should not be perceptibly different 

from refueling current vehicles. 

Finally, data are presented to show that test fuel volatility has a 

relatively small effect on required refueling canister size, and options are 

discussed for optimizing canister size through design changes that reduce the 

amount of vapor displaced from the tank. 
P.10 

ONBOARD CONTROL OF REFUELING EMISSIONS — 

SYSTEM DEMONSTRATION ON A 1985 VEHICLE 

INTRODUCTION 

ThlB report presents the findings of the Onboard Refueling Emission Control 

Project undertaken by Mobil Research and Development Corporation under 

contract to the American Petroleum Institute. 

Two technologies for controlling vehicle refueling emissions have been under 

consideration by the U.S. Environmental Protection Agency. They are the 

so-called Stage II vapor recovery at service stations and vehicle onboard 

controls. The feasibility of onboard controls was clearly demonstrated in a 

1978 program conducted for API by Atlantic Richfield Company, Exxon Research 

and Engineering Company, and Mobil Research and Development Corporation (1)*. 

Experience with Stage II technology in use in California and the District of 

Columbia shows that many customers have considerable difficulty in operating 

the equipment, and that the durability of the vapor capture components of the 

fuel dispensing nozzles is limited. The 1978 API program showed that onboard, 

systems require no modification of existing service station nozzles and can 

be unobtrusive to the user. Furthermore, studies (2, 3) have shown that 

onboard control of refueling emissions is more cost effective than Stage II 

technology when compared on an equal basis. 

The work reported here reinforces the 1978 API program by showing that 

onboard technology can be applied equally well to a car meeting more 

stringent 1985 exhaust and evaporative emission standards with the latest 

engine and emission control technology. The work also shows that an onboard 

refueling control system can Improve control of evaporative emissions. 

Objective 

The objective of this project was to equip a 1985 model car, representing 

up-to-date engine and emission control technology, with a fully operational 

onboard refueling emission control system meeting the following performance 

requirements: 

• 95% minimum recovery of refueling vapors when tested with 11.5 psi 

RVP gasoline at 88°F. 

• Compatibility with existing gasoline dispensing nozzles. 

• Fueling rate no less than the maximum rate at which the unmodified 

vehicle can be fueled. 

• No significant effect on exhaust emissions. 

• Evaporative emissions of 2.0 g/test maximum with 11.5 psi RVP fuel. 

• No significant effect on driveability. 

•Number in parentheses indicate references listed on page 18. 
P.11 

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Project Outline 

The work was divided into four major phases: 

1. Measuring baseline exhaust, evaporative and refueling emissions of 

the test vehicle and characterizing the flow behavior of the fuel 

tank during refueling. 

2. Designing and installing the refueling vapor collection system to 

include a carbon canister sized to handle vapor from an 11.5 psi RVP 

fuel at 88°F, a liquid seal to prevent escape of tank vapors through 

the filler neck, a vapor/liquid separator to prevent carryover of 

liquid fuel to the canister, and a vapor vent valve to satisfy 

safety requirements regarding fuel leakage In a vehicle rollover 

accident. The complete system is illustrated schematically in 

Figure 1. 

3. Developing a method of purging adsorbed fuel vapor from the canister 

during driving without affecting exhaust emissions or driveability. 

The purge rate is set to ensure ample canister capacity for 

controlling both refueling and evaporative emissions. 

4. Testing the complete vehicle to measure refueling emission control 

efficiency and demonstrate compliance with existing exhaust and 

evaporative emission standards according to EPA's proposed procedure. 

This report is organized according to these four phases of the project. 

CHARACTERIZATION OF TEST VEHICLE BASELINE 

The first part of this project Involved establishing a baseline for the test 

vehicle In its production configuration. This included measurement of 

exhaust emissions and fuel economy, evaporative emissions and uncontrolled 

refueling emissions, and characterization of the fuel tank and its flow 

behavior during refueling. 

Test Vehicle 

The test vehicle for this program, described in Table 1, is a 1985 Buick 

Century with a 3.8-liter V-6 engine and a four-speed automatic transmission. 

The engine is equipped with port fuel injection. The exhaust emission 

control system consists of a three-way catalyst with a feedback control 

system and exhaust gas recirculation (EGR). The evaporative emission control 

system consists of a 1.5-liter carbon canister containing approximately 400 

grams of activated carbon. 

The car's fuel tank, shown in Figure 2, has a 15.5-gallon capacity. The tank 

has a side-fill configuration with a fillneck approximately 40 inches in 

length (of which 12 inches is rubber tubing) and having an inside diameter of 

1-1/4 inches. Refueling vapors exit the tank through a second, smaller line 

(5/8-inch ID) running parallel to the fillneck. This line connects with the 
P.12 

- 3 -

fillneck just below the lead restrictor allowing vapors to vent to the 

atmosphere during refueling. A 0.048-inch diameter orifice in the top of the 

tank allows venting of the fuel tank when the system is closed (fuel cap 

on). This orifice is connected to the evaporative emission control canister 

through 1/4-inch tubing. To prevent spillage of fuel in the event of a 

vehicle rollover, the 1/4-inch vent line is bent into an antisiphoning 

"bow-tie" shape. 

Test Fuels 

Three test fuels with nominal RVP's of 9.0, 10.5, and 11.5 psi were used in 

this project. Typical test fuel properties are given in Table 2. Actual RVP 

values were generally within +0.3 psi of nominal values. Measured RVP 

values of test fuel samples taken at the time of a test are reported for 

baseline and final onboard system tests; otherwise, nominal values are used 

in this report. 

Baseline Emissions and Test Methods 

Baseline exhaust, evaporative, and refueling measurements were made after 

4,000 miles of break-in operation on a chassis dynamometer using a modified 

AMA durability driving cycle. 

Exhaust and Evaporative Emissions - The results of the baseline 

exhaust emission and fuel economy tests, conducted according to the Federal 

test procedure (4), are shown In Table 3. The data show that the car met the 

Federal standards for all three pollutants (HC, CO, NOx)on each of the 

three test fuels. 

The last two tests with nominal 11.5-psi RVP fuel differ from the earlier 

tests in the loading of the evaporative control canister prior to the 

preconditioning step of the Federal test procedure. The proposed EPA 

certification procedure for cars with onboard control systems (5, 6), which 

Is discussed in more detail later, requires loading the canister to 

breakthrough prior to the vehicle preconditioning. However, the current 

Federal vehicle emission test procedure does not specify the condition of the 

canister prior to preconditioning. The first three baseline emission tests 

with nominal 11.5-psi RVP fuel were conducted with only a partially loaded 

canister. To investigate the effects of a more fully loaded canister on the 

emissions of the vehicle in its production configuration, two tests were 

conducted with the canister loaded to breakthrough. These two tests showed 

higher levels of all three pollutants (HC, CO, NO-). In particular, CO 

increased from an average value of 2.2 g/mi with the partially loaded 

canister and 11.5 psi RVP fuel to 3.0 g/ml when the canister was loaded to 

breakthrough. Both sets of baseline data will be used later in evaluating 

the performance of the onboard system. 

In all of the baseline emission tests of Table 3, the canister was prepared 

by, first, purging to a constant base weight with air at 4 cubic feet per 

minute. Then it was loaded with gasoline vapor to the desired loading by 

drawing air through the headspace of an 18-gallon tank containing 

approximately 2 gallons of gasoline. The "partially loaded" canister had 
p.ia. 

- 4 -

been allowed to adsorb 20 g of fuel vapor. The loading to "breakthrough" was 

done according to the breakthrough criteria of EPA's proposed onboard test 

procedure (6, discussed later) using a hydrocarbon detector at the outlet of 

the canister. Breakthrough loading was 50 g. 

Baseline evaporative emission test results are shown in Table 4. These were 

obtained according to the Federal test procedure concurrently with the 

exhaust data above, using a partially loaded canister. The data show that 

the car met the 2.0 g/test evaporative standard on the 9.0-psi RVP test fuel, 

averaging 1.1 g/test. Evaporative emissions averaged 2.1 g/test on the 

10.5 psi fuel and 7.4 g/test on the 11.7-psi fuel. The mass of hydrocarbons 

adsorbed in the car's evaporative control canister is also shown in Table 4. 

Refueling Emissions - To establish a baseline for the onboard 

control system, the uncontrolled refueling emissions from the test vehicle 

were measured. Refueling emissions were measured in a SHED (Sealed Housing 

for Evaporative Determination; Model 7500, manufactured by Automotive 

Environmental Systems, Inc.) meeting EPA requirements for evaporative 

emission determinations (4), but with modifications to permit passage of a 

fuel delivery line into the SHED. A short length of 3/4-inch ID pipe was 

inserted through, and welded to, an aluminum plate which was bolted over an 

opening in a wall of the SHED. The plate was sealed to the wall with 

silicone sealant. Fuel delivery hose (3/4-inch Aeroquip hose) was connected 

to the pipe in the SHED wall and to the fuel conditioning cart (AESI Model 

FCC 7800) located outside the SHED. Inside the SHED a two-foot length of the 

same hose was fitted with an OPW 1A nozzle. 

Outside the SHED, a fuel dispensing pump and meter were positioned to 

minimize the hose length to the SHED wall. Fuel was recirculated 

continuously between the fuel conditioning cart and the dispensing pump to 

maintain the required fuel temperature throughout the system. All fuel lines 

were insulated. Recirculation was stopped just prior to actuating the fuel 

dispensing pump for a test. This system ensured that dispensed fuel 

temperature in the vehicle tank oh completion of refueling was within one 

degree (F) of the fuel temperature in the conditioning cart. 

The procedure used for measuring refueling emissions is outlined in Table 5. 

The test parameters, such as tank liquid temperature, dispensed fuel 

temperature and fill volume, were taken from EPA material presented at an 

October 1984 Workshop (5). The fuel tank was first filled to 10% of capacity 

with the specified test fuel. This fuel was then heated to 88 to 93°F 

keeping the tank vapor temperature within 6°F of the tank liquid. Two 

heating blankets (one on the bottom of the tank for heating the liquid and 

the second on the top for heating the tank vapor) were used for temperature 

control as described by EPA. When its temperature reached 88°F, the fuel was 

allowed to soak for a period of time to allow for saturation of the vapor 

space. The SHED was then closed and background hydrocarbon readings were 

taken every two minutes for ten minutes. The refueling was initiated at the 

end of the ten minutes, and the tank was filled to 95% of capacity by 

actuating the fuel pump located outside the SHED. After the refueling, SHED 

hydrocarbon readings were taken for ten minutes. 
- 5 -

Calculation of the uncontrolled refueling emissions from the above procedure 

involved plotting the last six minutes of background data taken before 

refueling and fitting a first order, least-squares line through these 

points. This line was then extrapolated out to the point in time ten minutes 

after refueling in order to estimate the contribution of the background 

emissions to the final SHED hydrocarbon reading. The difference between the 

final SHED hydrocarbon reading ten minutes after refueling and the 

extrapolated background reading at this same time was considered to be the 

actual refueling emissions. An example of this calculation is shown in 

Figure 3. 

This calculation method was used for measuring the uncontrolled refueling 

emissions because test experience indicated that a ten-minute period after 

refueling was required to ensure complete mixing and a stable response of the 

hydrocarbon instrument to the large quantity of hydrocarbon vapor released 

from the tank during the refueling. Using a shorter mixing time—for 

example, two minutes after refueling—would account for only approximately 

60% of the refueling emissions measured after 10 minutes. The extrapolation 

of the background reading was done to account for the emissions from the open 

fuel system after the refueling, but it made only a small difference 

(approximately 0.2 g/gal) in the final results. 

Results of the baseline uncontrolled refueling emissions are shown in 

Table 6. Emissions averaged 5.2 g/gal of dispensed fuel for the 9.0-psi fuel 

and 5.6 g/gal for the 10.5-psi fuel. Uncontrolled refueling emissions for 

the 11.5 psi fuel averaged 7.0 g/gal but results were more variable (ranging 

from 6.4 to 8.1 g/gal) than with the other two fuels. Variability can be 

attributed to the temperature differential between the tank liquid and the 

dispensed fuel (AT). The length of the soak period before refueling does 

not appear to have a significant effect on the amount of refueling emissions. 

Tank Flow Characteristics 

In addition to baseline emission data, information was also obtained 

concerning the operational characteristics of the vehicle fuel tank during 

refueling in the production configuration. This was done using a bench test 

rig on which the fuel tank and fillpipe were set up in the same configuration 

as on the car, as shown in Figure 4. The use of the bench rig made it easier 

to evaluate the operational characteristics of the fuel tank system. 

Placement of transparent lines in sections of the fillneck allowed 

information to be obtained about the operation of the nozzle shutoff 

mechanism. The automatic shutoff of the nozzle used (OPW 1A) is actuated by 

liquid blocking a venturi vent tube located near the end of the nozzle. 

Observations from several refuelings suggested that the nozzle shutoff was 

actuated by liquid being pushed up the tank vapor vent line (see Figure 2) 

and on to the end of the nozzle. Refueling tests also revealed that the flow 

rate of the dispensed fuel was limited to no more than 9.0 gal/min due to the 

restriction of vapor flow from the tank created by the lead restrictor. At 

dispensed fuel flow rates in the range of 8 to 9 gal/min, premature shutoff 

of the nozzle occurred frequently and was dependent on the position of the 

nozzle in the fillneck. 
P.15 

- 6 -

ONBOARD SYSTEM DEVELOPMENT 

Carbon Canister 

Development of an onboard control system first required the design of a 

carbon canister large enough to adsorb effectively the hydrocarbon vapor 

displaced from the tank. The canister used initially in the development of 

the onboard system was sized conservatively to ensure complete capture of 

vapors and to allow for accurate evaluation of other system components, 

particularly the fillpipe seal. The canister used for most of the onboard 

system development testing is shown in Figure 5. It was designed to have a 

carbon capacity of approximately 8 liters. This canister is a cylindrical, 

one-pass design with an open bottom very similar to the production 

evaporative canister. The canister was designed to use the same purge 

control solenoid valve as the production canister. The purge rate is 

controlled by an orifice that can be changed easily to study different 

rates. The canister was filled with approximately 2300 g of Westvaco 10 x 25 

activated carbon, the same type used in the production evaporative control 

canister. The Westvaco carbon has an apparent density of about 0.25 g/cc and 

a fresh working capacity of approximately 85 g/liter. 

The canister used in the final onboard system is shown in Figure 6. This 

smaller canister has a carbon capacity of approximately 4.5 liters and was 

sized based on data obtained with the 8-liter canister. This canister is a 

cubical, two-pass design with the vapor entry and exit both on the top of the 

canister. This type of design was used to increase the efficiency of the 

canister. The canister was filled with approximately 1300 g of Westvaco 10 x 

25 carbon. This canister also uses the production purge solenoid valve and 

can accommodate different size purge orifices. 

Both canisters were fabricated of materials readily available in a laboratory 

machine shop. The housing was made of aluminum sheet; the carbon was held in 

place with a plastic foam pad and wire mesh. The canister designs could be 

adapted to production by the same methods as current evaporative canisters. 

Fillpipe Seal and Vapor/Liquid Separator Development 

Two different sealing approaches were considered for blocking the escape of 

tank vapors from the fillpipe in the onboard system. Work in the 1978 API 

program (1) centered around using a mechanical seal (based on a common grease 

seal for a rotating shaft) as a means of sealing the fillneck during 

refueling. The nozzle spout fits snugly in the grease seal which is mounted 

in the fillpipe on top of the lead restrlctor. This seal was found to be 

very effective in controlling refueling emissions. More recently, the use of 

a liquid seal (similar to a sink trap) in the fillneck had been suggested by 

EPA (7) as a possible alternative to the mechanical seal. Advantages 

envisioned for the liquid seal included better durability and lower cost, 

both because of the absence of an elastomerlc seal that might be subject to 

wear. 

A vapor/liquid separator used in the tank vapor vent line in conjunction with 

a liquid seal is also described in this section. 
P.16 

- 7 -

External Liquid Seal - Development of the liquid seal was done using 

the bench test rig designed to duplicate exactly the vehicle's refueling 

system. Use of the bench rig made it easier to make and evaluate changes to 

the refueling system. The first liquid seal tests were conducted with a seal 

made from one-inch copper fittings. The seal was mounted outside the tank and 

replaced the rubber portion of the fillneck as shown in Figure 7. A 1/16-inch 

diameter drain hole in the bottom of the U-shaped trap was used to allow for 

pressure equalization between the tank and the top of the fillneck when the 

tank cap is in place. The existing tank vapor vent line was rerouted to the 

onboard canister. 

Initial refueling tests with the external liquid seal system revealed several 

operational differences from the production system. First, even though the 

refueling vapor vent line from the tank was not connected to the top area of 

the fillneck, the nozzle shutoff was successfully actuated by liquid backing 

up in the fillneck as the tank became full. Second, the system was able to 

accept somewhat higher flow rates than the production configuration. Finally, 

the effective liquid volume of the tank was increased by approximately 3/4 of 

a gallon. 

The sealing efficiency of the liquid seal was first tested by running the 

vapor vent line from the tank through the SHED wall and connecting it to the 

canister outside the SHED. With this test configuration, any refueling 

emissions measured in the SHED could be attributed to the seal alone. The 

procedure used for these refueling tests was essentially the same as for the 

uncontrolled refueling emission tests, with the exception of the calculation 

procedure. For these tests (and all other bench tests), the refueling 

emissions were taken to be the difference between the SHED hydrocarbon reading 

just prior to refueling and the reading two minutes after refueling, even 

though the reading had stabilized in much less time. 

Control efficiencies for all refueling tests in development of the onboard 

system were calculated using the baseline uncontrolled refueling emissions of 

the equivalent RVP fuel (e.g., 7.0 g/gal for an 11.5-psi RVP test'fuel) as a 

basis. This calculation procedure was used to avoid artificially increased 

control efficiencies for systems having higher potential emissions than the 

uncontrolled baseline case. Potential emissions are the total amount of 

hydrocarbon vapor emitted from the fuel tank during refueling (SHED 

hydrocarbon in grams + canister weight gain in grams). 

The results of the sealing efficiency tests for the external liquid seal are 

shown in Table 7. Control efficiencies for tests with both 9.0- and 11.5-psi 

fuels were 98 to 99% regardless of whether fueling was stopped at the 95% fill 

level or whether the nozzle was allowed to shut off automatically at the 100% 

level. No spitback was observed at automatic shutoff. The results of these 

tests also show that the potential emissions of the liquid seal system (8.5 

and 7.2 g/gal for the 11.5- and 9.0-psi fuels, respectively) were 

significantly higher than the uncontrolled refueling emission results (7.0 and 
P.17 

- 8 -

5.2 g/gal) on equivalent RVP fuels. This increase in potential emissions with 

the liquid seal system is attributed to the entrainment of air in the fuel in 

the fillpipe during refueling, which increases the amount of vapor displaced 

to the canister. 

External Liquid Seal and Vapor/Liquid Separator - The results of the 

Initial liquid seal tests were encouraging enough to justify further 

development of the system. One problem that was observed in the testing was 

the splashing of liquid in the vapor vent line as the tank pressure Increased 

just prior to nozzle shutoff. To prevent this liquid from being carried to 

the canister, a vapor/liquid separator (or surge tank) was placed in the vapor 

vent line at the level of the top of the fillpipe, as shown in Figure 8. 

Surge tanks made from one-quart and one-pint cans were fitted with 1/2-inch ID 

inlet and outlet lines offset to increase separation efficiency. 

Refueling tests with this system showed that the surge tank provided excellent 

vapor/liquid separation. Liquid that entered the vapor vent line accumulated 

in the surge tank, allowing the fuel tank back pressure to increase as needed 

to shut off the nozzle. After nozzle shutoff, liquid that had accumulated in 

the surge tank drained back into the tank. 

The result's of several refueling tests done to evaluate the effect of the 

surge tank on the overall system performance are presented in Table 8; for 

these tests, the canister was located in the SHED. The results show control 

efficiencies above 99% with the 11.5-psi fuel with both the pint and quart 

surge tanks. These tests were conducted at a fill rate of 9.5 gal/min with 

automatic nozzle shutoff; no spitback of fuel was observed at shutoff. 

Internal Liquid Seal - Further testing of liquid seals was done using 

a seal designed to fit in the tank at the end of the production fillneck, as 

shown in Figure 9. This internal liquid seal, also called a J-tube (7), is 

also made from one-inch copper fittings and has the same 1/16-inch drain hole 

as the external seal for pressure equalization when the tank cap is in place. 

The two-inch spacing between the Internal seal and the floor of the tank 

resulted from use of available one-inch fittings; it is not a critical 

dimension. Refueling tests conducted with the Internal liquid seal are 

presented in Table 9. Tests were carried out with both the one-quart surge 

tank and the one-pint surge tank. The data show control efficiencies for this 

configuration at 99.5% and above with the 11.5-psi fuel regardless of the fuel 

flow rate or surge tank used. The data also show that the potential emissions 

for the internal liquid seal system are greater than those of the external 

seal system. Potential emissions with the internal seal averaged 8.9 g/gal 

with the one-quart surge tank and 8.5 g/gal with the one-pint surge tank 

versus 8.3 and 8.1 g/gal with the external seal. In all tests, the tank was 

filled to automatic shutoff and no incidences of spitback were observed. 

Production Fillpipe As Seal - Observations from many refueling tests 

with transparent tubing in the fillpipe revealed that the fillpipe was largely 

filled with liquid. To explore whether the liquid in an unmodified fillneck 

might act as a vapor seal, several refueling tests were conducted using the 

production fillpipe with the vapor vent line and vapor/liquid separator from 

the liquid seal systems described above. The results of these tests, presented 
P.18 

- 9 -

in Table 10, show that the unmodified fillpipe could seal with greater than 

99% efficiency when fueling was stopped at the 95% level, but that spitback 

occurred when the tank was filled to automatic shutoff. 

Mechanical Seal - Development of an onboard system using a mechanical 

seal was de-emphasized due to success with the liquid seal system. However, 

to compare the potential emissions of a mechanical seal system to those of the 

liquid seal system, several tests were conducted in which a mechanical 

fillpipe seal was simulated by using a Stage II nozzle with its vapor vent 

plugged. A diagram of the bench rig configuration used for these tests is 

shown in Figure 10. The vent line to the carbon canister was attached by 

means of a 1/2-inch ID "tee" at the highest point in the production vent 

line. The results of these tests, presented in Table 11, show that the 

potential emissions of the mechanical seal system are up to 31% less 

(approximately 5.8 g/gal) with 11.5 psi RVP fuel than those of the liquid seal 

systems (approximately 8.1 and 8.5 g/gal for the external and internal seals, 

respectively, with the smaller surge tank). The potential emissions of the 

mechanical seal system are also less than the uncontrolled refueling emissions 

(7.0 g/gal with 11.5 psi RVP fuel) from the production configuration. This 

difference is attributed to the mechanical seal's preventing air from entering 

the fillneck- during refueling and becoming entrained in the liquid. Any 

entrained air is displaced to the canister, carrying along additional 

hydrocarbon vapor. The large difference observed In potential emissions 

suggests that there is a tradeoff possible in the two sealing approaches 

between the greater canister capacity required to contain the potential 

emissions from a liquid seal and the greater complexity of a mechanical seal. 

With the mechanical seal, the canister capacity could be reduced as much as 

31%. 

Vapor Vent/Rollover Valve 

Federal motor vehicle safety standards require that vehicle fuel systems be 

designed to restrict leakage in the event of a rollover accident. In the 

production fuel tank of the test car used in this project, this requirement is 

met by means of a restrictive orifice (0.048 inch) In the tank vent which 

leads to the evaporative emission control canister. In addition to this 

orifice, the 1/4-inch vent line to the canister is arranged in an antlsiphonlng 

"bow-tie" shape. To control leakage from the larger vent line needed in an 

onboard refueling emission control system, positive closure of the vent line 

would be most effective. This could be done by a valve that Is normally open 

and closes only in a rollover situation, or by a valve that is normally closed 

and opens only for refueling. The latter approach was selected for this 

project. Normal venting of the tank is maintained through the restrictive 

orifice and the antlsiphonlng "bow tie." This production 1/4-inch vent line 

is connected to the larger refueling vent line to carry nonrefueling tank 

vapors to the canister. 

The nozzle-actuated vapor vent valve, designed and tested to provide positive 

closure of the refueling vent line at all times other than during refueling, 

Is shown in Figure 11. The valve is mounted on the top of the fillneck just 

below the lead restrictor and is opened by the insertion of the nozzle, 

causing the lead restrictor door to raise the valve plunger. A spring is used 

to keep the valve seated when the nozzle is not Inserted, and a diaphragm is 

J 
P.19 

-10 -

used to seal the mechanical linkage between the fillneck and the valve. The 

valve is located in the refueling vent line downstream of the vapor/liquid 

separator. The valve was tested in numerous refueling tests and found to 

operate effectively. 

Final Onboard System 

Installation on Vehicle - Development of the components for the 

onboard system revealed that the internal liquid seal system with the nozzle 

actuated vapor vent valve was the simplest and most effective onboard system. 

This system, which also Included the use of a one-pint vapor/liquid separator, 

a 5/8-inch ID vapor line and a 4.5-liter carbon canister, was installed on the 

test vehicle. The complete system Is illustrated schematically in Figure 1. 

Installation of the internal liquid seal fabricated from available one-inch 

copper fittings required that the tank level-sensing float be rotated 180° on 

its mounting arm so that the seal would not obstruct movement of the float. 

Some cutting of internal tank baffles also was necessary. The vapor vent 

valve and the vapor/liquid separator (surge tank) were mounted on the fillpipe 

so that the assembly could be installed as a unit. This assembly was 

installed in available space behind the left rear quarter panel at the normal 

fillpipe location, as shown in Figure 12. The canister was placed in the 

engine compartment in the same location as the production evaporative 

canister, as shown in Figure 13. The original 1/4-inch tank vent line was 

connected to the larger 5/8-inch vapor vent line downstream of the vapor vent 

valve adjacent to the tank, allowing the tank to vent in its normal manner. 

Refueling Emission Tests - After installation of the complete onboard 

system on the test vehicle, several refueling tests were conducted to verify 

its performance. These tests were conducted using the test parameters in 

EPA's July 1985 Draft Recommended Test Procedure (6). These parameters are 

very similar to the test parameters used for the onboard system development 

work which were based on EPA's October 1984 Workshop (5), with a few 

exceptions. First, the recommended range for the temperature differential 

between the tank liquid and the dispensed fuel is 2 to 5°F in the newer 

procedure instead of 0 to 5°F. Second, the tank vapor temperature is to be 

kept within 3°F of the tank liquid, rather than within 6°F. Finally, as 

prescribed in the Draft Recommended Procedure, the final SHED hydrocarbon 

readings were taken 60 seconds (+5 seconds) after the end of the refueling. 

This was sufficient time for a stabilized reading. 

The results of the refueling tests with the complete onboard system installed 

on the car are presented in Table 12. The results show that the system 

controlled refueling emissions with an average of 98.5% efficiency. Potential 

emissions for the car system were lower than the potential emissions of the 

system tested on the bench rig. Some of this difference may be attributed to 

the different test parameters used. The bench tests were carried out using 

A T's of 0°F which represents a more severe condition than the A T of 2°F 

used in these tests. Some of the decrease in potential emissions may also be 

attributed to differences In the back pressure characteristics of the vapor 

vent valve and the 4.5-liter canister relative to those of the bench rig. 

These tests were conducted with automatic nozzle shutoff at the 100% fill 

level with no evidence of spitback on shutoff. The maximum rate at which the 
P.20 

- 11 -

car could be fueled without premature shutoff of the automatic nozzle with the 

onboard system in place was determined to be 9.0 gal/min. Even though flow 

rates of up to 9.7 gal/min (the maximum flow rate of the fuel dispensing cart) 

were obtained on the bench rig with the 8-liter canister, the 4.5-liter 

canister restricted the flow to 9.0 gal/min. This flow rate is, however, 

equivalent to the maximum flow rate obtainable with the production 

configuration. The effective tank volume (total capacity of tank when filled 

to automatic shutoff) for the final onboard system was 15.6 gallons, a 

difference of 0.1 gallon from the production configuration. 

SELECTION OF CANISTER PURGE RATE 

The ability of the vehicle to purge the onboard canister sufficiently to allow 

for effective control of the subsequent refueling, without affecting exhaust 

emissions, is an important aspect of the onboard system. Purging of the 

production evaporative canister is controlled by a solenoid valve, which is 

actuated by the engine Electronic Control Module (ECM). The ECM allows the 

canister to-purge when all of the following conditions are met: (1) the 

engine has been running for more than one minute, (2) the coolant temperature 

is above 80°C, (3) the vehicle speed is above 5 mph, and (4) the throttle is 

off idle. 

The purge rate of the production canister is controlled by a 0.040-inch 

orifice located in the top of the canister. This purge rate is designed to 

provide adequate canister capacity in the evaporative emission phases of the 

Federal test procedure. For example, the canister loading in the diurnal 

portion of the evaporative emission test was about 19 g with 9 psi RVP fuel 

(Table 4). Purging this quantity of hydrocarbons in the exhaust portion of 

the test is equivalent to an average purge rate of about 2 g/ml (19 g/11 ml). 

Purging refueling emissions from an 11.5 psi fuel will require a higher purge 

rate. For example, the minimum increase in purge rate to consume refueling 

emissions would be about 0.5 g/mi (canister loading of 8 g/gal [Table 12] 

divided by fuel economy of 18 mpg [Table 3]). 

As the first step in adapting the car's production purge system to handle 

refueling emissions, several tests were conducted with the 4.5-liter onboard 

canister to evaluate the ability of the feedback control system to compensate 

for increased purge rates and to determine the maximum purge rate that the 

system could accept without affecting exhaust emissions. These tests were 

conducted using the earlier EPA proposed certification procedure (5) for 

onboard systems and a 12-psi RVP test fuel. As prescribed in the earlier 

procedure, the canister was loaded to saturation, that is, to constant 

canister weight, prior to the preconditioning. Orifices ranging from 3/64 to 

9/64 inches were used in the onboard canister to vary the rate of purge. The 

ECM-actuated solenoid valve controlled the purge timing as in the production 

system. 

The exhaust and evaporative emission results for these tests, along with the 

canister weight change data for the various portions of the test, are 

presented in Table 13. The results show a wide variation in the CO emissions 
P.21 

- 12 -

of the vehicle with the 5/64-, 7/64- and 9/64-inch orifices for essentially 

the same amount of hydrocarbon purged during the exhaust emission portion of 

the test. Results at the highest purge rates (7/64- and 9/64-inch orifices) 

are not significantly different from baseline data obtained with the 

evaporative canister loaded to breakthrough—that is, in a condition 

comparable to that of the larger onboard refueling control canister. Results 

at the lowest purge rate (3/64-inch orifice) are equivalent to the baseline 

data with a partially loaded evaporative canister—that is, in a condition 

equivalent to present certification testing practices. The 3/64-inch orifice 

was selected for further testing to confirm whether it would allow adequate 

purging of the canister to meet the evaporative and refueling control 

requirements of the proposed test procedure. The 3/64-inch orifice (0.047 

inch) is about 38% larger in area than the production 0.040-Inch purge control 

orifice. 

FINAL SYSTEM TESTING - EPA PROPOSED CERTIFICATION TEST 

The final step in the development of the onboard control system was to test 

the complete-vehicle according to EPA's proposed certification test procedure 

(6) to evaluate the ability of the system to control refueling emissions 

without affecting exhaust emissions. These tests were conducted using the 

vehicle onboard system described earlier and the 3/64-inch purge control 

orifice. 

The proposed EPA test procedure for certifying onboard test vehicles is based 

on the current certification procedure, but with additional parts added to 

evaluate the effectiveness of the onboard system. A summary of the proposed 

procedure is shown In Table 14. The test is started by testing the refueling 

emission control efficiency, or the capacity, of the onboard system. The 

vehicle is refueled (10 to 100% fill) with an 11.5-psi RVP test fuel at 88°F 

while in the SHED. The procedure used for measuring the refueling emissions 

here is the same as that described in an earlier section for testing the 

complete vehicle onboard system. Additional refuelings are then conducted on 

the car until the canister reaches breakthrough. EPA defines breakthrough as 

a three-fold increase in SHED hydrocarbon concentration in one minute. The 

vehicle is then preconditioned and the present certification procedure 

performed as usual. 

Following the hot soak portion of the test, the vehicle Is run through a 

series of drivedown cycles, each consisting of an LA-4 driving cycle and a 

one-hour hot soak, until the fuel tank level reaches 10% (the vehicle starts 

the test at 40% of tank capacity). The vehicle is then refueled to 40% of 

capacity—actually a 30% refueling—using the standard refueling procedure. 

The purpose of this operation is to test the adequacy of the canister purge by 

refueling with a volume of fuel equivalent to that consumed in driving. 

The exhaust and evaporative emission test results using this proposed 

procedure and 11.5-psi RVP test fuel are presented in Table 15. Two tests 
P.22 

- 13 -

were conducted with the onboard canister loaded to breakthrough as proposed by 

EPA,. A third test was conducted with the onboard canister loaded to 

saturation. The exhaust emission results show that HC and N0X emissions 

were equivalent to the baseline data for a partially loaded evaporative 

canister in all three tests. In one of these tests, CO emissions were higher 

than the baseline for a partially loaded evaporative canister, but lower than 

the baseline for an evaporative canister loaded to breakthrough, as the 

refueling canister was. Statistical analysis of the test data indicate, 

however, that the differences among all of the CO emissions values are not 

significant at the 95% confidence level. 

The evaporative emission results for all three tests were within the 2.0 g/test 

standard specified for a 9-psi test fuel. Evaporative emissions for the two 

tests in which the canister was loaded to breakthrough were 1.2 and 1.3 g/test, 

respectively. Evaporative emissions for the saturated canister test measured 

2.0 g/test. The three tests combined had an average evaporative emissions 

level of 1.5 g/test, a 78% reduction from the average of the baseline values. 

These results provide confirmation that onboard control systems do have the 

ability to control excess evaporative emissions from fuels representative of 

commercial volatility levels. 

Data showing the purge characteristics of the onboard canister during the 

entire test sequence are presented in Table 16 for all three tests. The table 

shows the canister weight change for each of the test segments and the 

cumulative purge for the entire test. The preconditioning purged roughly the 

same amount of hydrocarbon as was gained by the canister during the diurnal. 

The contraction of the tank vapor space overnight due to the cooling of the 

test fuel caused several grams of hydrocarbon to be drawn back into the tank. 

The purge rate was high enough that fewer than the six drivedown cycles driven 

In the tests would have been sufficient to prepare the canister for the 30% 

fueling (11 drivedown cycles would be required to drive down the tank to 

10%). At the end of the sixth cycle, the cumulative amounts of hydrocarbon 

purged were 84, 109 and 142 grams for the three tests, respectively. This is 

considerably more canister purge than is necessary to control the approximately 

40 grams of refueling emissions from the 30% fill test. In the case of Tests 2 

and 3, the cumulative purge after six drivedown sets represents almost enough 

hydrocarbon capacity to allow for another complete (10 to 100%) refueling. 

The results of the initial refueling capacity tests and the final 30% fill 

tests are presented in Table 17. Control efficiencies for the three 30% fill 

tests averaged 98.7% and were equivalent to the refueling capacity test 

results which averaged 98.6%. These results illustrate the ability of the 

onboard system to regenerate the carbon canister in approximately half the 

time required by the certification procedure, without significantly affecting 

exhaust emissions. 

Effect of Fuel RVP on System Performance 

To Investigate the effect of test fuel RVP on the performance of the onboard 

system, several tests were run according to the proposed onboard certification 
P.23 

- 14 -

procedure with nominal 9.0- and 10.5-psi RVP fuels. Two tests were conducted 

on each fuel; however, the drivedown (6 LA-4's and hot soaks) was completed in 

only one of the two tests. 

The exhaust and evaporative emission results for the 9.0- and 10.5-psi RVP 

fuels are shown in Tables 18 and 19, respectively. The results of the 

baseline tests are shown for comparison. With 9-psi RVP test fuels, emissions 

of HC and CO showed no significant difference at the 95% confidence level when 

compared with the baseline data, while N0X emissions showed a slight 

increase. Exhaust HC, CO and N0X results with the 10.5-psi RVP fuel were 

not significantly different from the baseline data, also at the 95% confidence 

level. 

Evaporative emission results for the onboard system were identical for the 

9.0- and 10.5-psi RVP fuels, both averaging 0.85 g/test. These results 

represent approximately a 25% reduction in evaporative emissions with the 

9.0-psi RVP fuel and a 60% reduction with the 10.5-psi RVP fuel, compared to 

the baseline data. 

The canister purge data for the 9.0- and 10.5-psi RVP fuel tests are presented 

in Tables 20 and 21, respectively. The data show again that the hydrocarbon 

purge rate is sufficient to purge the canister in much less driving than that 

specified in the proposed certification procedure. With the 9.0-psi RVP fuel, 

the cumulative purge of the canister at the end of the sixth drivedown cycle 

(approximately 18% of the tank capacity consumed) was 94 grams. This 

represents approximately the potential emissions from a complete (10 to 100%) 

refueling. With the 10.5-psi RVP fuel, a net purge of 113 grams was recorded 

at the end of the sixth drivedown cycle. 

The results of the refueling capacity tests and the 30% fill tests for both 

the 9.0- and 10.5-psl RVP tests are shown in Table 22. The control 

efficiencies for the refueling capacity tests averaged 98.6% for both fuels. 

The control efficiency of the 30% fill test was 97.9% with the 9.0-psi RVP 

fuel and 98.2% with the higher RVP fuel. Potential emissions of the 30% fill 

tests were lower than those of the corresponding refueling capacity tests. 

This may have resulted from weathering of the tank fuel during the test 

sequence. 

DISCUSSION 

Emission Control Performance 

The data presented in this report clearly demonstrate that a high level of 

control of refueling emissions is feasible with an onboard system. Control 

efficiency greater than 98% was achieved consistently using test fuel with an 

RVP of 11.5 psi to represent the volatility of gasolines in the marketplace in 

summertime. These results were obtained using a common service station nozzle 

operating with automatic shutoff; no spitback occurred. 

In addition to controlling refueling emissions, the onboard system improved 

control of evaporative emissions to the extent that the present standard of 

2.0 g/test prescribed for a 9-psi RVP test fuel was met with fuel of 11.5-psi 

RVP. 
- 15 -

Furthermore, there was no significant interaction of the system with exhaust 

emissions or fuel economy. There was no evidence of any effect on 

driveability in the driving that was done in the program, although no 

driveability evaluation using standardized test methods was possible in the 

time available. No significant effect on driveability would be expected in 

view of the feedback air-fuel ratio control system on the test vehicle and the 

absence of an effect on exhaust emissions at the canister purge rate selected. 

Onboard System Design and Construction 

The onboard refueling emission control system tested is simple in design and 

construction. It should be readily adaptable to common automotive production 

methods and materials, and all components can be packaged in the test vehicle 

without any structural changes. The refueling canister tested had a carbon 

capacity of 4.5 liters (1300 g of Westvaco 10 x 25 activated carbon) compared 

to the production evaporative canister of 1.5 liters (400 g of the same 

carbon). The refueling canister was mounted in the same underhood location as 

the evaporative canister without having to relocate any other parts. The 

canister is patterned on production evaporative canister designs and could be 

manufactured' by the same molding methods. 

The vapor vent line to the canister was made of 5/8-inch ID tubing to minimize 

back pressure at the vapor flow rates encountered during refueling. This line 

could be fabricated from steel tubing of the same type as is used for the 

1/4-inch line of the production evaporative emission control system. Further 

system optimization may allow a refueling vapor vent line diameter smaller 

than 5/8 inch, and locating the canister closer to the fuel tank would reduce 

the length of line required. 

Modifications at the fuel tank and fillpipe are the liquid seal, the 

vapor/liquid separator or surge tank; and the nozzle-actuated vapor vent 

valve. In the tank of the test car, minor modifications were made to the 

level-sensing float and to some baffles to accommodate the liquid seal 

.fabricated from available plumbing fittings. In production, the seal could be 

formed as an extension of the fillpipe penetration through the tank wall and 

could be shaped to fit available space so that no other modifications would be 

needed. Alternatively, the test of the sealing ability of the production 

fillpipe (Table 10) shows that it may not be necessary to make any changes at 

the tank end, if the flow characteristics of the fillpipe at shutoff can be 

modified to prevent spitback. 

The vapor/liquid separator, or surge tank, in the vapor vent line and the 

vapor vent valve were designed to be mounted on the fillpipe and to fit in 

available space between the left rear quarter panel and the trunk side wall at 

the normal fillpipe location. These components could be manufactured as a 

subassembly that would be installed in the vehicle in the same way as the 

production fillpipe. This subassembly would be connected to the existing tank 

fill and vent fittings. 

The nozzle-actuated vapor vent valve is designed to satisfy the safety 

requirement for preventing fuel leakage from the tank in the event of a 

vehicle rollover accident. It does this by keeping the refueling vent line 

closed at all times other than during refueling. This arrangement maintains 

normal tank.venting and its associated rollover protection. 
- 16 -

The vapor/liquid separator protects the carbon canister from liquid fuel that 

might otherwise be carried along by the vapor during refueling. The system as 

tested on the bench rig also prevented liquid fuel from flooding the canister 

in a simulated nozzle shutoff failure. In this test, fuel overflowed from the 

fillpipe, as it would from a production fillpipe, without generating enough 

back pressure to force it to the canister. This behavior of the system would 

be sensitive to vapor flow geometry on any particular vehicle. If necessary, 

a float valve could be Included in the vapor/liquid separator to provide 

further protection against possible canister flooding. 

With the system tested, filling of the tank ended in a normal manner. Nozzle 

shutoff was automatic and without spitback. The tank level at shutoff was 

within 0.1 gal of the nominal capacity. Overfilling the tank is not possible 

in a practical situation because the refueling vapor vent becomes blocked by 

liquid, leaving only the production 0.048-inch orifice in the tank top for 

further slow venting. 

The only change from the production vehicle that was necessary for purging the 

refueling control canister was to increase the size of the purge control 

orifice; the -area of the orifice was increased about 38%. 

Durability testing was not possible in the time available for this project; 

however, the.system described should not present any new or unique durability 

problems. All of the components are based on design concepts that have been 

proven in the past and can be manufactured from common automotive materials* 

The carbon canister is an enlargement of present evaporative control 

canisters. The vapor/liquid separator could be manufactured from sheet metal 

or molded of plastic. The only moving parts are in the vapor vent valve, 

which is kept closed by a spring and opened by nozzle insertion. This valve 

also might be formed from sheet metal or molded of a suitable plastic. The 

diaphragm separating the valve from the fillpipe (Figure 10) could be designed 

in various ways, for example as a bellows-type boot of fuel-resistant 

elastomer. The material could be the same as that proven In fuel pump 

diaphragms. 

Fuel RVP Versus Canister Size 

The data reported above show that test fuel RVP affects the canister capacity 

required to contain refueling and evaporative emissions. The mass of vapor 

displaced from the tank in the prescribed 100% fueling test is the controlling 

factor. Evaporative emissions are less important than refueling emissions for 

canister sizing because the canister is loaded to breakthrough prior to the 

evaporative portion of the test procedure and the purge rate during 

preconditioning determines whether sufficient capacity will be available for 

the diurnal emission test. Capacity required for refueling emissions Is 

dictated by potential emissions. Potential emissions and related canister 

sizes at the three fuel RVP levels tested are summarized In Table 23. 

Reducing RVP from 11.5 to 10.5 psi reduces potential emissions only 12% and 

reduces required canister size proportionately from the 4.5 liters of carbon 

tested to an estimated 4.0 liters. Table 23 also shows that control 

efficiency was not affected by test fuel RVP. 
P.26 

- 17 -

Reducing Potential Emissions 

As stated above, the size of the carbon canister required is determined by the 

amount of potential emissions. At a given fuel RVP level, factors such as the 

type of fillpipe seal used—whether liquid or mechanical—and the design of 

the vapor/liquid separator Influence the amount of potential emissions from a 

particular onboard system design. 

Although the onboard system development work for this project centered around 

the use of a liquid seal, the testing conducted with a mechanical seal showed 

that there is a large difference in the potential emissions of the two sealing 

systems. A summary of the potential emissions of these two sealing systems is 

presented In Table 24. The data show that the potential emissions of the 

mechanical seal system are approximately 31% lower than those of the liquid 

seal system. Based on the lower potential emissions, it is estimated that the 

required canister size for a mechanical system would be approximately 3.1 

liters. Potential emissions are lower because the mechanical seal prevents 

air from entering the fillneck and becoming entrained in the dispensed fuel, 

thus reducing the amount of vapor displaced to the canister. 

The difference in potential emissions suggests that there is a tradeoff 

possible between the two sealing approaches. The lower potential emissions of 

the mechanical seal would allow a smaller canister than that required with the 

liquid seal; however, the mechanical seal itself is more complex and it 

requires additional components. Because the mechanical seal physically seals 

the fuel tank, a pressure-relief valve would be required to prevent excessive 

pressure buildup in the tank in the event of a nozzle shutoff failure or a 

blockage of the vapor path to the canister. The liquid seal, with its "sink 

trap" design, serves as its own pressure-relief valve, because tank pressure 

can never be greater than the "head" of liquid In the fillpipe. Any greater 

pressurization of the tank will cause the fillpipe to overflow as It can in 

fueling current vehicles. Also in the event of a nozzle shutoff failure, a 

check valve in the vapor line would be needed with the mechanical seal to 

prevent flooding of the canister. " 

Development testing has also shown that other design aspects of the onboard 

system can have an effect on the amount of potential emissions. For example, 

a reduction in potential emissions of approximately 0.4 g/gal was seen with 

the Internal liquid seal system when the one-quart surge tank was replaced by 

the one-pint surge tank (Table 9). Furthermore, limited testing suggests that 

reductions in the potential emissions of the liquid seal system can be 

obtained by recycling tank vapor into the fillpipe in the region of turbulent 

flow where air entrainment occurs. This causes saturated vapor to be 

entrained in place of fresh air and reduces the amount of additional 

hydrocarbon vaporized. Evidence of potential emission reduction through vapor 

recycling can also be found in comparing potential emissions from baseline and 

liquid seal tests. Turbulence and vapor entrainment are observed in both 

cases. The lower emissions in the baseline case indicate that some of the 

entrained vapor Is recycled tank vapor instead of fresh air; recycling does 

not occur with the liquid seal because the vent line Is not connected to the 

fillpipe. The baseline emissions are lower because less air is Introduced; 

and since the recycled vapor is already saturated with hydrocarbons, further 

vaporization is reduced. 

2722H 
P.27 

- 18 -

REFERENCES 

1. On-board Control of Vehicle Refueling Emissions, Demonstration of 

Feasibility, Publication No. 4306, American Petroleum Institute, October 

1978. 

2. Cost comparison for Stage II and On-board Control of Refueling Emissions, 

American Petroleum Institute, January 1984. 

3. Evaluation of Air Pollution Regulatory Strategies for Gasoline Marketing 

Industry, EPA-450/3-84-012a, U. S. Environmental Protection Agency, July 

1984. 

4. Code of Federal Regulations, Part 86, Federal Register, Vol. 24, No. 124, 

June 28, 1977. 

5. Onboard Control of Refueling Emissions, Test Procedure Development and 

Preliminary Baseline Test Results, Workshop, U. S. Environmental 

Protection Agency, October 17, 1984. 

6. Draft Recommended Test Procedure for the Measurement of Refueling 

Emissions, Technical Report, EPA-AA-SDSB-85-5, U. S. Environmental 

Protection Agency, July 1985. 

7. Recent Developments in EPA's Program to Evaluate Onboard Control of 

Refueling Emissions, U. S. EPA/API Briefing, February 4, 1985. 
P.28 

Table 1 

Onboard Refueling Control System Test Car 

1985 Buick Century 

Engine: 3.8 Liter V-6, Multipoint Fuel Injection 

Transmission: Automatic 4-Speed, Front-Wheel Drive 

EPA Inertia Weight: 3,250 lb 

Emissions Certification: 1985 U.S. 

Emission Control System: 

Exhaust: 3-Way Catalyst with Closed Loop 

Electronic Control of Air/Fuel 

Ratio and EGR (EGR + 3 CL) 

Evaporative: 1.5 liter Carbon Canister (400 g of activated carbon) 

Fuel Tank Capacity: 15.5 gal 

2722H/24 
Table 2 

Nominal RVP, psi 

Actual RVP, psi 

Distillation, °F at 

IBP 

10% 

20% 

30% 

50% 

90% 

EP 

Test Fuel Properties 

9.0 

9.3 

88 

123 

152 

184 

227 

316 

378 

10.5 

10.5 

86 

118 

146 

180 

226 

318 

385 

11.5 

11.7 

84 

113 

141 

177 

226 

317 

376 

Specific Gravity 0.7450 0.7417 0.7401 

Wt. Fraction Carbon 0.8653 0.8648 0.8621 

Octane 

R+M 

2

 mln « 91 91 91 

2722H-25 
P.30 

Table 3 

Buick Century Baseline Emission Tests^ 

Exhaust Emissions and Fuel Economy 

Test Fuel Exhaust 

RVP, psi HC 

Partially Loaded Evaporative Canister2 

8.6 0.15 

9.1 0.14 

10.6 0.16 

10.2 0.14 

11.4 0.17 

11.2 0.15 

12.2 0.20 

Evaporative Canister at Breakthrough3 

11.5 0.19 

11.8 0.24 

Federal Standard 

Emissions, 

CO 

2.00 

1.62 

1.85 

1.86 

2.44 

2.01 

2.24 

2.90 

3.10 

g/mi 

NO*. 

0.34 

0.31 

0.36 

0.36 

0.37 

0.36 

0.35 

0.39 

0.45 

City Fuel 

Economy, mpg 

18.7 

18.6 

18.9 

18.8 

18.8 

18.5 

17.6 

18.1 

17.7 

8.7 - 9.2 0.41 3.4 1.0 

1. Vehicle mileage approximately 4,000 miles. 

2. Hydrocarbon loading is 20 g over purged weight. 

3. Hydrocarbon loading is 50 g over purged weight; vehicle mileage 

approximately 6200 miles. 

2722H/26 
P.31 

Table 4 

Buick Century Baseline Emission Tests! 

Evaporative Emissions 

Test Fuel 

RVP, 

8.6 

9.1 

10.6 

10.2 

11.4 

11.2 

12.2 

J?si • . 

Federal Standard 

Diurnal 

0.72 

0.82 

1.69 

1.47 

6.13 

4.47 

3.61 

Hot Soak 

0.36 

0.36 

0.44 

0.66 

2.18 

1.93 

1.93 

Total 

1.1 

1.2 

2.1 

2.1 

8.3 

6.4 

5.5 

Diurnal 

19.5 

18.7 

25.7 

24.9 

29.0 

28.2 

28.5 

xgnt v»ain, g 

Hot Soak 

8.4 

7.8 

11.1 

12.3 

16.6 

15.5 

12.1 

8.7-9.2 2.0 

1. Vehicle mileage approximately 4,000 miles. 

2722H/27 
P.32 

Table 5 

Uncontrolled Refueling Emission Measurement Procedure1 

1. Drain fuel tank and fill to 10% of capacity (1.5 gal in 15.5-gal tank) 

with test fuel at 88°F. 

2. After vapor temperature reaches at least 82°F, allow fuel to soak at 88 

to 93°F for desired soak period with the fuel cap on and the evaporative 

control canister hooked up. Keep tank vapor temperature within + 6°F of 

liquid. 

3. At end of soak period, remove cap and place nozzle in fillneck at the 

desired flow setting. Weigh evaporative canister and replace. 

4. Close SHED door and record background HC readings every 2 minutes for 

10 minutes, keeping tank liquid at 88 to 93°F. 

5. Operate fuel pump outside SHED to fill tank to approximately 95% level 

(13.0 gal added to initial 1.5 gal in 15.5-gal tank) with fuel at 88°F + 

2°F. 

6. Measure SHED HC concentration every 2 minutes for 10 minutes after end 

of refueling. 

1. Based on (5). 

2722H/28 
Table 6 

Buick Century Baseline Emission Tests1 

Uncontrolled Refueling Emissions2 

Nominal 

Fuel 

RVP, psi 

9.0 

9.0 

9.0 

Avg. 

10.5 

10.5 

Avg. 

11.5 

11.5 

11.5 

11.5 

11.5 

Avg. 

Refueling 

Emissions, 

g/gal 

5.3 

5.3 

5.0 

5.2 

5.5 

5.8 

5.6 

7.0 

6.6 

6.4 

8.1 

6.9 

7.0 

Soak 

Time, 

min 

15 

100 

15 

60 

65 

15 

15 

15 

60 

60 

Canister Weight 

Gain, Soak/Test, 

8 

— /2.2 

15.7/2.0 

— /3.3 

25.4/1.9 

18.6/2.0 

— /2.7 

— /2.2 

— /2.2 

10.5/2.5 

— /2.6 

Tank 

Liquid 

88 

87 

91 

88 

89 

88 

92 

92 

88 

88 

Fuel Temperature, °F 

Tank 

Vapor 

83 

84 

86 

86 

87 

87 

85 

84 

87 

87 

Dispensed 

89 

88 

88 

86 

89 

90 

89 

89 

88 

88 

A T3 

-1 

-1 

+3 

+2 

0 

-2 

+3 

+3 

0 

0 

1. Vehicle mileage approximately 4,000 miles. 

2. Dispensed Fuel Flow Rate - 8.5 g gal/min, Fill - 10-95% (13.0 gal) 

for all tests. 

3. AT - Tank Liquid Temp. - Dispensed Fuel Temp. 

2722H/29 
Table 7 

External Liquid Seal, Bench Tests 

Nominal 

Fuel 

RVP, psi 

9.0 

9.0 

9.0 

9.0 

11.5 

11.5 

Fill Level1 

% 

95 

95 

100 

100 

95 

95 

Control 

Efficiency, %2 

99.2 

99.1 

98.3 

98.4 

98.6 

99.2 

Actual 

Emissions, 

0.04 

0.05 

0.09 

0.09 

0.10 

0.05 

g/gal 

Potentia 

Emissions, 

7.0 

7.4 

7.0 

7.3 

8.1 

8.8 

il 

g/gal 

Fuel Temp, 

Dispensed 

88 

88 

89 

88 

88 

88 

°F 

A ^ 

0 

0 

-2 

0 

+1 

0 

1. Fill level represents % of tank capacity; 100% corresponds to automatic nozzle shutoff 

with approx. 14 gal. dispensed on top of initial 10% fill of 1.5 gal. 

Dispensed Fuel Flow Rate -8.5 gal/min for all tests. 

2. Seal only; canister outside SHED. 

3. AT - Tank Liquid Temp - Dispensed Fuel Temp. 

2722H/30 
Nominal 

Fuel 

RVP, psi 

11.5* 

11.5* 

11.55 

11.55 

External Liquid 

Control 

Efficiency, %2 

99.3 

99.3 

99.7 

99.6 

Table 8 

Seal with Vapor/Liquid Separator, Bench 

Actual Potential 

Emissions, g/gal Emissions, g/gal 

0.05 8.3 

0.05 8.3 

0.02 8.1 

0.03 8.0 

Tests1 

Fuel Temp, 

Dispensed 

88 

88 

88 

88 

°F 

A TJ 

-1 

0 

0 

-1 

1. Dispensed Fuel Flow Rate - 9.5 gal/min and Fill - 10 to 100% for all tests. 

2. Seal and canister. 

3. A T - Tank Liquid Temp - Dispensed Fuel Temp. 

4. One-quart cylindrical vapor/liquid separator. 

5. One-pint rectangular vapor/liquid separator. 

2722H/31 

co 

cn 
Nominal 

Fuel 

RVP, psi 

11.53 

11.53 

11.53 

11.53 

11.5* 

11.5* 

Table 9 

Internal Liquid Seal with Vapor/Liquid Separator, Bench Tests1 

Fill Rate Control 

gal/min Efficiency, % 

5.8 99.7 

8.5 99.7 

9.6 99.5 

9.6 99.6 

9.7 99.6 

9.6 99.7 

Actual 

Emissions, g/gal 

0.02 

0.02 

0.04 

0.03 

0.03 

0.02 

Potential 

Emissions, g/gal 

8.9 

8.6 

9.2 

8.8 

8.4 

8.5 

Fuel Temp, °F 

Dispensed A Tz 

88 0 

88 -1 

88 0 

88 0 

88 0 

88 -1 

1. Fill - 10 to 100% for all tests. 

2. AT - Tank Liquid Temp - Dispensed Fuel Temp. 

3. One-quart cylindrical vapor/liquid separator. 

4. One-pint rectangular vapor/liquid separator. 

2722H/32 

CO 
Table 10 

Production Fillpipe As Liquid Seal, Bench Tests1 

Nominal 

Fuel Fill Rate, Fill, Control Actual Potential Fuel Temp, °F 

RVP, psi gal/min % Efficiency, %2 Emissions, g/gal Emissions, g/gal Dispensed A T-* 

11.5 9.5 95 99.9 0.01 9.5 88 0 

11.5 9.5 100 Spitback - 9.2 88 0 

11.5 9.2 100 Spitback - 9.1 88 0 

1. Test system had one-quart cylindrical vapor/liquid separator. 

2. Seal only; canister outside SHED. 

3. AT - Tank Liquid Temp. - Dispensed Fuel Temp. 

2722H/33 
Table 11 

Mechanical Seal, Bench tests1 

Nominal 

Fuel Fill Rate, Control Actual Potential Fuel Temp. °F 

Efficiency, %2 RVP, psi gal/min Emissions, g/gal Emissions, g/gal Dispensed A T3~ 

11.5 

11.5 

11.5 

11.5 

9.5 

9.5 

9.5 

9.5 

99.8 

99.9 

99.9 

99.9 

0.01 

0.01 

0.01 

0.01 

5.8 

5.8 

6.0 

5.7 

89 

89 

88 

88 

-1 

-1 

0 

-1 

1. Stage II nozzle with vapor line plugged. Fill - 10 to 100% for all tests. 

2. Seal and canister. 

3. AT - Tank Liquid Temp - Dispensed Fuel Temp. 

2722H/34 
Test Fuel 

RVP, psi 

11.5 

11.4 

11.5 

11.6 

Fill Rate, 

gal/min 

9.0 

9.1 

8.9 

9.0 

Refueling Tests 

Control 

Efficiency, % 

98.7 

98.4 

98.5 

98.6 

Table 12 

with Complete Onboard 

Actual 

Emissions, g/gal 

0.09 

0.11 

0.11 

0.10 

System on Car1 

Potential 

Emissions, g/gal 

8.0 

7.5 

8.1 

7.8 

Fuel Temp, 

Dispensed 

88 

88 

88 

88 

°F 

AT^ 

2 

2 

2 

2 

1. 4.5-liter canister, vapor vent valve of Figure 10, 100% fill to automatic shutoff, 

approx. 14.0 gal dispensed on top of initial 10% fill of 1.5 gal. 

2. A T - Tank Liquid Temp - Dispensed Fuel Temp. 

2722H/35 
Table 13 

Preliminary Canister Purging Experiments 

4.5-Liter Canister, 12.2 RVP Test, fuel 

4.5L Canister 

Purge 

Orifice, in1 

9/64 

9/64 

7/64 

7/64 

5/64 

5/64 

3/64 

3/64 

Baseline Average 

Partial Loading-* 

Breakthrough Loading3 

Exhaust 

HC 

0.28 

0.24 

0.21 

0.21 

0.21 

0.17 

0.16 

0.15 

0.17 

0.22 

Emissions, 

CO 

2.77 

3.65 

2.41 

3.14 

3.06 

3.15 

2.21 

2.27 

2.23 

3.00 

g/ml 

NOx 

0.42 

0.29 

0.33 

0.35 

0.35 

0.35 

0.35 

0.33 

0.36 

0.42 

Canister Weight Change During 

Federal TeBt 

Preconditioning Diurnal 

-67 

-64 

-68 

-73 

-57 

-47 

-44 

-25 

1 

-21 

+28 

+28 

+28 

+29 

+28 

+34 

+31 

+28 

+28 

+26 

Procedure 

Exhaust 

-52 

-55 

-53 

-52 

-52 

-62 

-43 

-33 

-16 

-26 

. g 

Hot Soak 

+18 

+19 

+19 

+14 

+15 

+13 

+12 

+13 

+15 

+9 

Net 

-73 

-72 

-74 

-82 

-66 

-62 

-44 

-17 

+28 

-12 

1. All tests with saturated 4.5-liter canister. 

2. 20 g loading of production evaporative canister. 

3. 50 g loading of production evaporative canister. 

2722H/36 
P.41 

Table 14 

Summary of Proposed EPA Certification Test Procedure1 

1. Drain fuel tank and fill to 10% of capacity with test fuel. After 

stabilizing temperatures and obtaining initial SHED HC readings, fuel to 

automatic nozzle shutoff at 100% of tank capacity with 11.5-psi RVP fuel 

at 88 + 2°F. Tank liquid must be between 90-93°F. Obtain final SHED HC 

readings and calculate refueling emissions. 

2. Drain tank and perform additional 10 to 100% refuelings under the same 

conditions until canister breakthrough is reached. (Breakthrough, as 

defined by EPA, is a factor of 3 increase in SHED HC concentration in 

one minute.) 

3. Precondition car using standard LA-4 cycle. 

4. Soak overnight. 

5. Drain and fill tank to 40% with 55°F fuel with onboard canister 

disconnected. 

6. Conduct diurnal heat build (60-84°F in 1 hour). 

7. Conduct cold-start, cold-transient and hot-start exhaust emission tests. 

8. Conduct hot soak test. 

9. Drivedown to 10% of tank capacity using a series of LA-4 driving cycles 

each followed by a 1-hour hot soak. 

10. Refuel car to 40% of tank capacity to test adequacy of purge. Procedures 

as in Step 1. 

1. Based on (6). 

2722H/37 
Table 15 

Final System Test Results - EPA Proposed Certification Test1 

Exhaust and Evaporative Emissions, 11.5 psi RVP Fuel 

Test 

Number 

1 

2 

3 

Test 

RVP, 

11, 

11. 

11, 

Fuel 

psi 

.7 

.5 

.5 

Average 

Canister 

Loadin « » * 

224 

217 

281 

1. 3/64* 

11.4 

11.2 

12.2 

11.5 

11.8 

purge orifice 

o o o 

CM CM CM 

50 

50 

• 

Exhaust Emissions. 

HC 

0.17 

0.15 

0.20 

0.19 

0.24 

CO 

City Fuel 

Economy, mpg 

Evaporative Emissions, g/Test 

Diurnal Hot Soak Total 

Baseline Data 

2.44 

2.01 

2.24 

2.90 

3.10 

0.37 

0.36 

0.35 

0.39 

0.45 

18.8 

18.6 

17.6 

18.0 

17.7 

0.76 

0.69 

1.30 

0.45 

0.61 

0.72 

6.13 

4.47 

3.61 

2.18 

1.93 

1.93 

1.2 

1.3 

2.0 

1.5 

8.3 

6.4 

5.5 

2722H/38 
Table 16 

Purge Data - EPA Proposed Certification Test 

11.5-psi RVP Fuel, 3/64" Purge Orifice 

Test 1 Test 2 Test 3 

Loading 

Preconditioning 

Overnight 

Diurnal 

Exhaust Test 

Hot Soak 

Drivedown Cycle1 

1 

2 

3 

4 

5 

6 

Net Canister 

Wt. Change, g 

+224 

-23 

-5 

+30 

-32 

+11 

-23 

-13 

-9 

-7 

-5 

-8 

Cumulative 

Purge, g 

23 

28 

-2 

30 

19 

42 

55 

64 

71 

76 

84 

Net Canister 

Wt. Change, g 

+217 

-28 

-11 

+27 

-33 

+19 

-32 

-15 

-13 

-11 

-10 

-2 

Cumulative 

Purge, 

28 

39 

12 

45 

26 

58 

73 

86 

97 

107 

109 

6 

Net 

Wt. 

Canister 

Change, g 

281 

-34 

-10 

+28 

-43 

+16 

-40 

-15 

-15 

-11 

-10 

-8 

Cumulative 

Purge, g 

34 

44 

16 

59 

43 

83 

98 

113 

124 

134 

142 

1. Each drivedown cycle is one LA-4 driving cycle plus a one-hour hot soak. 

2722H/39 

iCo 
Test 

Number 

Refueling 

Test 

Capacity 

30% Fill 

Capacity 

30% Fill 

Capacity 

30% Fill 

Table 17 

Refueling Test Results - EPA Proposed Certification Test1 

11.5 psi RVP Fuel 

RVP. psi 

11.7 

11.5 

11.5 

Fill Rate, 

gal/min 

8.0 

8.0 

8.6 

6.5 

8.0 

7.9 

Control 

Efficiency, % 

98.5 

98.5 

98.6 

98.6 

98.7 

99.0 

Actual 

Emissions, 

0.10 

0.10 

0.10 

0.10 

0.09 

0.07 

g/gal 

Potential 

Emissions, g/gal 

8.4 

8.3 

7.9 

8.3 

8.3 

Fuel Temp. 

Dispensed 

88 

88 

88 

88 

88 

88 

, °F 

AT* 

-I 

-l 

0 

-1 

-1 

0 

1. 3/64" Purge Orifice. 

2. A T - Tank Liquid Temp - Dispensed Fuel Temp. 

2722H/40 
Table 18 

Final System Test Results - EPA Proposed,Certification Test1 

Exhaust and Evaporative Emissions, 9.0 psi RVP Fuel 

Test Test Fuel Canister Exhaust Emissions, g/mi City Fuel Evaporative Emissions, g/Test 

Number RVP, psi Loading, g HC CO NOx Economy, mpg Diurnal Hot Soak Total 

6 

7 

8.8 

8.9 

Average 

162 

166 

0.13 

0.20 

0.17 

1.34 

2.04 

1.69 

0.39 

0.40 

0.40 

17.7 

18.4 

18.1 

0.33 

0.48 

0.40 

0.48 

0.7 

1.0 

0.85 

1. 3/64" Purge Orifice. 

2722H/41 

Baseline Data 

8.6 

9.1 

20 

20 

0.15 

0.14 

2.00 

1.62 

0.34 

0.31 

18.7 

18.6 

0.72 

0.82 

0.36 

0.36 

1.1 

1.2 
Table 19 

Final System Test Results - EPA Proposed Certification Test1 

Exhaust and Evaporative Emissions, 10.5 psi RVP Fuel 

Test 

Number 

4 

5 

Test Fuel 

RVP. psi 

10.3 

10.4 

Average 

Canister 

Loading, g 

202 

197 

Exhaust Emissions, g/mi 

HC CO NOx 

0.16 

0.19 

0.18 

1.65 

2.34 

2.00 

0 

0 

0 

Baseline 

.32 

.38 

.35 

Data 

City Fuel 

Economy, mpg 

18.0 

18.3 

18.2 

Evaporative Emissions, g/Test 

Diurnal Hot Soak Total 

0.42 

0.40 

0.48 

0.41 

0.9 

0.8 

0.85 

10.6 

10.2 

20 

20 

0.16 

0.14 

1.85 

1.86 

0.36 

0.36 

18.9 

18.8 

1.69 

1.47 

0.44 

0.66 

2.1 

2.1 

1. 3/64" Purge Orifice. 

2722H/42 
P.47 

Table 20 

Purge Data - EPA Proposed Certification Test 

9.0-psi RVP Fuel, 3/64" Purge Orifice 

Test 6 Test 7 

,. 

Loading 

Preconditioning 

Overnight 

Diurnal 

Exhaust Test 

Hot Soak 

Drivedown 

1 

2 

3 

4 

5 

6 

Net Canister 

Wt. Change, g 

+162 

-28 

-7 

+14 

-24 

+4 

N.A. 

Cumulative 

Purge, g 

-

28 

35 

21 

45 

41 

N.A. 

Net 

Wt. 

Canister 

Change, g 

+166 

-26 

-4 

+14 

-26 

+5 

-18 

-11 

-10 

-7 

-7 

-4 

Cumulative 

Purge, g 

-

26 

30 

16 

42 

37 

55 

66 

76 

83 

90 

94 

2722H/43 
P.48 

Table 21 

Purge Data - EPA Proposed Certification Test 

10.5-psi RVP Fuel, 3/64" Purge Orifice 

Test 4 Test 5 

. 

Loading 

Preconditioning 

Overnight 

Diurnal 

Exhaust Test 

Hot Soak 

Drivedown 

1 

2 

3 

4 

5 

6 

Net 

Wt. 

Canister 

Change, g 

+202 

-45 

-7 

+20 

-28 

+6 

N.A. 

-

Cumulative 

Purge, g 

_ 

45 

52 

32 

60 

54 

N.A. 

, 

Net Canister 

Wt. Change, g 

+197 

-39 

-10 

+21 

-30 

+6 

-21 

-12 

-11 

-7 

-7 

-3 

Cumulative 

Purge, g 

— 

39 

49 

28 

58 

52 

73 

85 

96 

103 

110 

113 

2722H/44 
Table 22 

Refueling Test Results - EPA Proposed Certification Test1 

10.5 and 9.0 psi RVP Fuels 

Test Refueling Test Fuel Fill Rate, Control Actual Potential Fuel Temp., °F 

Number Test RVP, psi gal/min Efficiency, % Emissions, g/gal Emissions, g/gal Dispensed A T^ 

4 

5 

6 

7 

Capacity 

Capacity 

30% Fill 

Capacity 

Capacity 

30% Fill 

10.3 

10.4 

8.8 

8.9 

8.0 

8.1 

7.9 

8.0 

7.0 

7.9 

98.7 

98.4 

97.9 

98.6 

98.6 

98.2 

0.07 

0.09 

0.12 

0.07 

0.07 

0.09 

7.2 

7.4 

6.9 

5.9 

6.0 

5.5 

88 

88 

89 

88 

88 

88 

+1 

-1 

0 

0 

0 

1. 3/64" Purge Orifice 

2. A T - Tank Liquid Temp - Dispensed Fuel Temp. 

2722H/45 
Table 23 

Fuel RVP, psi 

11.5 

10.5 

9.0 

Effect of Test Fuel RVP 

Potential Refueling Emissions 

g/gal % Reduction 

8.3 Base 

7.3 12 

6.0 28 

on Canister Size 

Canister Size 

for 15.5 gal Fuel Tank 

2 

Liters Grams 

4.5 - Tested - 1300 

4.0 - Estimated - 1150 

3.2 - Estimated - 925 

Avg. Control 

Efficiency, % 

98.6 

98.6 

98.6 

1. Hydrocarbon vapor displaced from fuel tank; average of two or three tests. 

2. Westvaco 10x25 activated carbon. 

2722H/46 

cn 

o 
P.51 

Table 24 

Potential Emissions Comparison1 

System 

Internal Liquid Seal 

Mechanical Seal 

Uncontrolled Baseline 

Average Potential 

Emissions, g/^al 

8.5 

5.8 

7.0 

Percent Decrease 

Relative to Liquid Seal 

31 

Canister Size, 

Liters of Carbon 

4.5 Tested 

3.1 Estimated2 

1. Based on bench tests with 11.5 psi fuel. 

2. Estimate based on using Westvaco 10 x 25 carbon. 

2722H/47 
Figure 1 

ONBOARD REFUELING EMISSION CONTROL SYSTEM 

Vapors Purged 

to Engine 

During Driving 

Solenoid 

Valve and 

3

/M" Orifice 

Control 

Purging 

%" Vapor Line 

Production Vent and —»4 

Rollover Protection 

Vapor/Liquid 

Separator 

4.5 Liter 

Carbon Canister 

Traps Vapors 

Nozzle-Actuated 

^ Vapor Vent 

" Valve 

Liquid Seal in Fillpipe 

Prevents Escape of Vapors 

Ul 
Figure 2 

BUICK CENTURY FUEL TANK AND FILLPIPE 

PRODUCTION CONFIGURATION 

Fuel Sending Unit - ^ 

and Vent Orifice \ 

Nozzle 

Spout 

i2y2" 
Figure 3 

UNCONTROLLED REFUELING EMISSION CALCULATION 

tn 

E 

2 

a 

a 

Ui x 

Refueling + 

Background 

Emissions 

Refueling 

Background 

Emissions 

Net Refueling 

Emissions 

—i— 

8 12 16 20 24 

Time, Minutes 

28 

cn 
Figure 4 

BENCH TEST RIG 

Photo shows fuel tank and production fillpipe in the 

same orientation as on the car. 
P.56 

Figure 5 

PRELIMINARY ONBOARD CANISTER 

&0 LITERS OF CARBON 

Tank Vapor Inlet h

1

*'-! 

'/«" VA" \ \ Purge Outlet 
Figure 6 

FINAL ONBOARD CANISTER 

4 £ LITERS OF CARBON 

Solenoid -.— 

Support T tf 

Top

 1,/«' Gas Inlet, %" 0 0 

Solenoid 

Support 

1 tf 

Space 

Modified Swagelok Plastic 

Bulkhead Union Foam 

Baffle 

*y 

Vi" x Vi" 

Viton Gasket 

2" 

Cover Plate 

6Vi"-

r 

7y2" 
Figure 7 

EXTERNAL LIQUID SEAL 

Vapor to Canister 

I Dotted Line Shows 

Production Configuration 

Drain 
Figure 8 

EXTERNAL LIQUID SEAL 

WITH VAPOR/LIQUID SEPARATOR 

Vapor to Canister 

Vapor/Liquid 

Separator. 
Figure 9 

INTERNAL LIQUID SEAL 

(J-TUBE) 

Vapor f 

to Canister? 

y^ 

Vapor/Liquid 

Separator 

P 
Figure 10 

MECHANICAL SEAL BENCH 

Vapor 

to 

Canister 

Stage II Nozzle 

Used as Seal 

b> 
Figure 11 

NOZZLE-ACTUATED REFUEUNG EMISSIONS VAPOR VENT VALVE 

Vapor to 

Canister 

Vapor from 

Vapor/Liquid Separator 

r'c"~*<~""~~S"tock r — 

.Door 

H 

TT 

-Nozzle 

"^j -
Figure 12 

ONBOARD FILLPIPE ASSEMBLY 

Fillpipe with vapor vent valve and one-pint vapor/liquid separator 

mounted in space be&ween left rear quarter panel and trunk sktewaJI. 

Vapor/liquid separator is removed in left-hand photograph to show 

vapor vent valve. View is from wheel well with spush guard removed. 
Figure 13 

ONBOARD CANISTER MOUNTED IN TEST CAR 

Photograph shows onboard canister mounted in place of 

production evaporative canister in right front corner of 

engine compartment. A diagonal corner brace that passes 

over the canister was removed for the photograph. 
P.65 

Onboard Control of Refueling Emissions 

A Report to the American Petroleum Institute 

Washington, D.C. 

January 1986 

Exxon Research and Engineering Company 

Linden, New Jersey 
P.66 

CONTENTS 

TABLE OF CONTENTS i 

LIST OF TABLES i i 

LIST OF ILLUSTRATIONS iii 

EXECUTIVE SUMMARY 1 

INTRODUCTION 3 

RESEARCH OBJECTIVES 4 

PROGRAM OUTLINE 5 

Vehicles 5 

Onboard System Design. 8 

Overall Design 8 

Charcoal Canister Design .8 

Vapor-Liquid Separator and Vapor Lines 10 

Fillneck Vapor Seal .10 

Purge System 11 

Test Procedure 11 

Fuels 15 

RESULTS 16 

Refueling Emissions 16 

Effect of Auto-Shutoff 1 6 

Effect of Rollover/Overfill Valves... 20 

Effect of Canister Size ...20 

Tailpipe Regulated Emissions .......23 

Evaporative Emissions .26 

Canister Purge Drivedown . .26 

Effect of Dispensing Flow Rate .26 

APPENDIX 29 
P.67 

LIST OF ILLUSTRATIONS 

Figure 1 Principal Elements 6 

Charcoal Canister 7 

Figure 3 Combination Valve .....9 

Figure 4 Test Procedure 13 

Figure 5 Dodge Refueling Emissions 17 

Figure 6 Pontiac Refueling Emissions. ...18 

Figure 7^ Effect of Canister Size on Refueling Emissions 21 

Figure-8. Effect of RVP on Evaporative Emissions .24 

Figure 9 Dodge Average Canister Performance 27 

Figure 10 Pontiac Average Canister Performance........ .28 

ii 
P.68 

LIST OF TABLES 

Table 1 Test Vehicles 5 

Table 2 Test Parameters 12 

Table 3 RVP of Test Fuels 15 

Table 4 Effect of Auto-Shutoff 19 

Table 5 Refueling Emissions with Combination Valve 20 

Table 6 Regulated Tailpipe Emissions 22 

Table 7 Evaporative Emissions ...25 

APPENDIX 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Table 

Al 

A2 * 

A3 

A4 

A5. 

A6 

A7 

A8 

A9 

AIO 

AH 

A12 

Dodge Purge Flow Rates 30 

Pontiac Purge Flow Rates 31 

RVP of Test Fuels .32 

Test Fuel Inspections. .33 

Baseline Refueling Emissions.... ...34 

Dodge Refueling Emissions 35 

Pontiac Refueling Emissions 36 

Effect of Canister Size..... 37 

Dodge Baseline Regulated Emissions 38 

Dodge Regulated Emissions 39 

Pontiac Baseline Regulated Emissions.......... 40 

Pontiac Regulated Emissions .41 

ii 
P.69 

EXECUTIVE SUMMARY 

This report presents the findings of the Onboard Control of Refueling Emissions Project undertaken by Exxon Research 

and Engineering Co. (ERE) under contract to the American Petroleum Institute. Onboard refueling control technology has been 

successfully applied to two vehicles, a 1985 Dodge 600 and a 1984 

Pontiac Parisienne, meeting stringent exhaust and evaporative 

emissions standards. Refueling emissions have been controlled 

with 98+% efficiency without a vapor seal in tests with 11.8 RVP 

fuel at 88°F. 

The Dodge was designed as a one canister system to 

handle both the evaporative and refueling emissions. The Pontiac 

was designed as a two canister system. The production evaporative 

canister was retained to only handle the evaporative emissions 

from the carburetor. The refueling canister was designed to 

handle both the refueling emissions and the evaporative emissions 

from the tank. The design size of the Dodge refueling canister 

was 3.5 liters for a 14 gallon fuel tank while the the Pontiac 

used a 7:5-liter canister for a 25 gallon fuel tank. 

The elements of the Onboard system for controlling refueling emissions were constructed out of components similar to 

those found in current automobile evaporative control systems. 

In both vehicles the production fillpipe was used with the vapor 

vent rerouted to the Onboard canister. The entire system was designed for minimum pressure drop so that a mechanical or liquid 

vapor seal is not necessary. The flow of fuel into the tank provides enough pressure head to force the tank vapors into the 

canister. The new vapor vent li.ne was relocated to remove entrained droplets and prevent spitback. A combination vaporliquid separator, overfill shutoff valve, and rollover shutoff 

valve located between the fuel tank and the canister removed any 

remaining entrained droplets. 

Both Onboard vehicles were thoroughly tested according 

to a draft procedure proposed by the U. S. Environmental Protection Agency. The following conclusions are drawn from this testing. 

1. Refueling emissions were controlled with 98+$efficiency under 

severe test conditions using an 11.8 RVP gasoline dispensed 

at 88°F at flow rates of 4 to 11 gpm without a vapor seal. 

2. There is no effect on the operation of an automatic gasoline 

dispensing nozzle and no spitback was observed. 

3. The control of evaporative emissions was improved to the 

extent that the present standard of 2 grams/test prescribed 

for a 9 RVP fuel was met with a fuel of 11.8 RVP. 
P.70 

- 2 

4. A comparison of the tailpipe regulated emissions from the 

production and the Onboard vehicles.shows that for the 

Pontiac there is a numerically small but statistically significient increase in HC and N0„ emissions but a numerically 

large and statistically significient decrease in CO 

emissions. The Dodge met the 9 RVP tailpipe regulated emissions on an 11.8 RVP fuel. There was a numerically small but 

statistically significient increase in HC and N0X emissions. 

Both the production and Onboard Pontiac met HC and N0X standards but not the CO standard on the 11.8 RVP fuel. The 

" Onboard vehicle met the CO standard on the 9 RVP fuel. 

5. The Onboard canister can be purged faster than is necessary 

to restore its capacity using the production purge system for 

the production evaporative canister. 

Data is also presented relating canister size to refueling emissions and the effect of dispensing rate. Durability 

testing and diagnostics are beyond the scope of the project. 

However» none of the components of the Onboard system present 

durability-problems that have not been addressed in current 

evaporative control systems. 

Finally, from a customer's viewpoint, since no vapor 

seal was used, vehicles equipped with the Onboard system should 

not be perceptibly different from current production vehicles. 
P.71 

- 3 -

INTRODUCTION 

Emissions of hydrocarbon vapors from vehicles during 

refueling operations can be controlled either by Stage II systems 

at the gasoline dispensing facilities or by an Onboard charcoal 

system in the vehicle itself. Stage II systems are in-place in 

California and Washington, DC. The Onboard System was demonstrated by Exxon and Mobil with four 1978 vehicles in 1978 contracts with API (1). Recently, EPA has again stated their intention to make a decision in 1985 on the issue of controlling refueling emissions. 

There have been three major criticisms of onboard control of refueling emissions and the 1978 API test program. They 

are: . 

1. The complexity of and test time required for the proposed 

test procedure. 

2. The inability to control refueling emissions with gasolines 

at high RVP while maintaining control of tailpipe emissions. 

3. API's 1978 demonstration vehicles are not representative of 

today's technology, particularly with regard to the fuel 

system and emission control technology. 

This report covers the work performed to confirm the 

feasibility of onboard control with modern high technology 

vehicles. 

API Report No. 4308 Oct 1978 

"Onboard Control of Vehicle Refuleing Emissions" 
P.72 

4 -

RESEARCH OBJECTIVES 

The objectives of this project were: 

1. To confirm the feasibility and effectiveness of onboard 

technology with today's high technology vehicles with modern 

fuel systems on gasolines of high volatility without any 

debits in exhaust emissions or driveability, 

2. To determine the feasibility of the proposed EPA test 

procedure and suggest possible improvements; and 

3. To confirm onboard's potential for controlling excess 

evaporative emissions on gasolines of high volatility. 
P.73 

PROGRAM OUTLINE 

Vehicles 

Two late model vehicles representative of 1987 vehicle 

technology were equipped with onboard control systems. Although 

the trend of future vehicles is toward fuel injection because of 

exhaust emission control and vehicle driveability, a carbureted 

vehicle represents a worst case since a carburetor is less flexible in its fuel metering. Therefore, one carbureted vehicle and 

one throttle body fuel injected (TBI) vehicle were chosen (see 

Table 1). Based on preliminary EPA data, the Pontiac, with a 

large tank and a short rear fillpipe, will probably have the 

highest level of refueling emissions. 

Table 1 

TEST VEHICLES 

Vehicle No. 1 Vehicle No. 2 

Make Dodge Pontiac 

Model 600 Parisienne 

Year 1985 1984 

Cylinders 4 8 

Displacement 2.2 1 5.0 1 

Gas Tank 14 gal. 25 gal. 

Fill Point Side Rear 

Fuel System TBI 4 bbl Feedback 
FIGURE 1 

PRINCIPAL ELEMENTS OF 

ENHANCED ON-BOARD SYSTEM 

. Standard 

Fillpipe 

With Vent 

Rerouted to 

Cannister 

Rollover Shutoff 

Overfill/Shutoff 

Entrained 

Liquid 

Separator 

Purged 

HC Vapors 

To Engine 

HC 

Vapors 

• 

i 

Enlarged 

Charcoal 

Cannister 
- 8 -

• 

» Onboard System Design 

Overall Design 

The principal elements of an enhanced onboard system to 

control refueling and evaporative emissions are shown in 

Figure 1. The standard fillpipe is used with the vapor vent 

rerouted to the onboard canister. The new vapor vent is located 

opposite to the fillpipe in order to remove entrained droplets. 

To reduce entrained droplets further, a vapor-liquid separator is 

positioned between the tank and the canister. The new oversized 

vapor line leads to the charcoal canister located either in the 

engine compartment or the trunk. The entire system is designed 

for minimum pressure drop so that a mechanical or liquid (such as 

a "J" tube) vapor seal is not necessary. The system is discussed 

further in the following paragraphs. 

Charcoal Canister Design 

'The design of the charcoal canister was based on ERE's 

1978 work. It is a two-pass metal container with a closed bottom 

and a top vent as shown in Figure 2. The canisters have an L/D 

ratio of 2.5. This was estimated in the 1978 study to provide an 

optimal length-to-diameter ratio: too short a path length would 

result in a loss of working capacity and too long a path length 

would cause a high pressure drop across the canister during refueling. 

The Dodge was designed as a one canister system. The 

production evaporative canister was replaced by the refueling 

canister. The refueling canister was designed to handle not only 

the refueling emissions but also the diurnal and hot soak evaporative emissions. The Pontiac was designed as a two canister 

system. This was by choice i.e., to demonstrate the effectiveness 

of both systems. It could have been designed as a one canister 

system just as easily. The production evaporative canister was 

retained to handle the evaporative emissions from the carburetor. 

The refueling canister handled all the evaporative emissions from 

the fuel tank. 

The canisters were loaded with 6x1 6 mesh Calgon BPLF3 

activated charcoal. This carbon was used in the 1978 study and is 

currently being used in many evaporative control canisters. 

Calgon BPL-F3 has a fresh butane adsorption capacity of 68 grams/ 

liter with an apparent density of 0.35 grams/cc. In order to account for possible degradation in the initial working capacity 

with age, increased loading due to air entrainment, and to provide a safety margin, 30 grams/liter was chosen as the design 

working capacity. 

In the 1978 study, a working capacity of 25 to 35 grams 

butane was used. Therefore, based on fuel tank volume and the 

baseline refueling emissions for the 12 RVP fuel, two canisters 

were constructed, a nominal 3.5 liters (1) and a nominal 7.5 L, 
P.76 

- 7 -

FIGURE i 

CHARCOAL CANISTER 

PURGE CONNECTION 

WIRE MESH 

REFUELING PURGE 

VAPORS VAPORS 

FUEL TANK 

CONNECTION 

METAL 

DIVIDER 

PERFORATED 

METAL 

GLASS WOOL 

VENT 

GLASSWOOL 

METAL 

DIVIDER 

INSULATINGSHEET 

CHARCOAL 
P.77 

9 -

EifiUBEJ r 

COMBINATION VALVE 

.4- 1.0. 

ROLLOVER SHUTOFF 

1/2- OlA SS BALL 

1 1/9' OVERFILL SHUTOFF 

sA*A»ATA*A*A*AVATATA*ATA*ATATA»ATA*A*A-

•A*ATA*A*ATANTAN.TATA*A*ATA*AT*VATAT»T. 

A^ATATATATAVATA^ATATATATATATAVATATAn,'A; 

yAVA»A^ATATATA^A,»A,»iTA^ATA»A»A'A'»ATA''AT 

ATATAVATATATATAVATA^AVATATAVATATATAVATA' 

.TATAVAVAVAVATAVA^ATA^ATA^ATATATATATATAT. 

A^ATAVATA»ATA»ATA'»ATA^AVAWAVATAVAV_r» 

>A,»ATATATA^A'*A'»A^ATATA,»A'»A'»A'»A,rA'AVAVA; 

A^^ATA'UTA''A,»A^ATATATATA%,TA''AnTA'»ATA: 

A*ATA*A*A*A*A*A*A*ATATA'rA*A»A*ATA'»A'»A'*A: 

.TAVAWATATAWAWAWAWAWAWA'VA''' . 

A^ATATA'»,A'rATATATATATATA'»ATA''A'»ATATA'lrA^AAVATAVATATAVATAVATATAVATATAVAVATAVATATA' 

.•A^AVAVATA^A^A'»ATATATATATATATATATATATAT; 

A^A'A»A''A^A'A'A''A'TA^ATA'A'»A'»A1UTA^AVA^A' 

S.S MESH 

VAPOR LIQUID 

SEPARATOR 

KXXXX)(X)(X)Q()()QQ()QQ(X)C iliilllllll1 
10 -

for the 14 gallon Dodge and the 25 gallon Pontiac respectively. 

In addition, a 5 1 canister used in the 1978 study refueling 

study and in other ERE programs was used in both the Dodge and 

the Pontiac to investigate the effect of canister size. 

Vapor-Liquid .Separator and Vapor Lines 

The vapor line from the tank to the canister was 3/4 

inch I.D. Buna N Weatherhead H10012 fuel line hose. The diameter 

was chosen to minimize the pressure drop in the system. The production vapor line from the tank to the evaporative canister was 

plugged. The new 3/4 inch vapor line remained open to the tank 

and canister during all operations. 

A vapor-liquid separator was placed ahead of the canister in the vapor line at the level of the fillpipe. Preliminary experiments indicated that some entrained droplets could 

travel up the vapor line. The vapor-liquid separator insures that 

only vapor reaches the charcoal canister. (Any liquid absorbed 

on the charcoal would reduce its effectiveness.) Most of the 

data was; collected using a vapor-liquid separator constructed 

from a pint can filled with steel mesh. Toward the end of the 

project, a combination vapor-liquid separator, rollover valve, 

and overfill valve was constructed as shown in Figure 3- The 

volume of the vapor-liquid separator was one pint. The rollover 

valve was simply a 1/2 inch steel ball. The overfill valve was a 

float constructed from a tank gage float from a General Motors 

fuel pick-up assembly. Crude bench tests indicated that the 

rollover ball valve held in the 180 degree position. 

The line to the canister was placed in the vapor dome 

of the tank. In the Dodge, since the vapor dome extends across 

the entire rear portion of the tank, the line to the canister was 

placed on the opposite side of the tank from the fillpipe to 

reduce entrained droplets. In the Pontiac, the production 

fillpipe directs the liquid onto a secondary baffle protecting 

the sending unit. To reduce entrained droplets created by this 

baffle, the secondary baffle was removed, the fillpipe extended 

and aimed downward away from the sending unit. The fillpipe 

therefore became a submerged fill at about mid-fill. In the 

Dodge, the fillpipe becomes submerged at about 95$. The vapor 

line to the canister was placed in the vapor dome which also 

housed the sending unit. 

Fillneck Vapor Seal 

The fillpipes and fillnecks with the lead nozzle 

restrictor for both vehicles were standard production without any 

nozzle or fillpipe seals. However, the production vent lines were 

plugged inside the tank but remained in place. The new vapor 

lines to the canister provided the exit route for the vapors 

generated during refueling. With the low pressure drop design of 

the canister and vapor line, no seal at the fillneck was 

needed. The flow of fuel into the tank provides enough pressure 
P.79 

- 11 

head to force the tank vapors into the canister. In addition, air 

is aspirated into the tank slightly, increasing the canister 

loading and preventing any vapor release out the fillpipe. 

Purge System 

The canisters are purged with air in the direction 

opposite to the adsorption of hydrocarbons (countercurrent). The 

purge control system, including purge control valves, purge 

control orifice, purge pipes, etc , were standard production for 

both vehicles. For the Dodge, the purge control valve is built 

into the production evaporative canister. It was removed from the 

evaporative canister and installed inline to the refueling 

canister which was located in the engine compartment. In the 

Pontiac, a tee with balancing orifices was placed in the normal 

production purge line. The production vapor line from the tank 

to the production evaporative canister was used as the purge line 

to the refueling canister mounted in the trunk. 

.As can be seen in Tables A1 and A2, the purge rates for 

the Dodge averaged 1.4 1pm and for the Pontiac 8.8 1pm over one 

LA-4 driving cycle with 7.8 1pm purging the refueling canister 

and 1.0 1pm purging the production ECS canister. The Dodge TBI 

fuel delivery system operated well below where additional purge 

would cause loss of control of air-fuel ratio. At 50 mph, the 

purge rate was 5.3 1pm. Loss of control occurred at 16.1 1pm of 

pure butane. This was not the case for the carbureted Pontiac. 

Loss of control of the air-fuel ratio occurred at 18 1pm of pure 

butane and the purge rate is 18 1pm at 50 mph. With a saturated 

canister, the purge stream initially will have a high concentration of hydrocarbons. Any loss of control in the air-fuel 

ratio could then result in increased exhaust emissions. 

Test Procedure 

The test procedure used to measure the refueling and 

tailpipe emissions was based on the draft procedure presented by 

the EPA at their Oct. 17, 1984 workshop on "ONBOARD CONTROL OF 

REFUELING EMISSIONS", "TEST PROCEDURE DEVELOPMENT AND PRELIMINARY 

BASELINE TEST RESULTS" held in Ann Arbor, Michigan. This draft 

procedure utilizes the basic SHED test equipment for measuring HC 

evaporative emissions. The refueling is conducted inside the 

SHED under specified test conditions. 

The test procedure is relatively straight forward. The 

test fuel is heated to test temperature in a Horiba fuel conditioning cart. The fuel is then recirculated through the dispensing pump, Tokheim Model 785-MC-PR, up to the SHED wall and back 

to the Horiba fuel cart. The vehicle's tank is heated by a blanket to test temperature. When the test conditions have stabilized, the OPW automatic nozzle is placed in the fillpipe on the 

high setting after dispensing 3 gallons of heated fuel into a 

drum. The SHED door is closed and a background HC reading is 

taken format least three minutes. After the refueling, a stabil-
P.80 

-12 -

i.zed HC reading was taken. It normally took between 3 to 4 minutes even with an extra explosion proof fan providing additional 

air circulation. The FID HC reading was continuously recorded. 

The difference between the two HC readings determined the refueling emissions. Since no mechanical seal was used on the fillpipe, the conservative approach of not time extrapolating the 

background was used. This also counted the emissions from the 

nozzle just being in the fillpipe. The specified test conditions 

are given in Table 2 below. 

Table 2 

TEST PARAMETERS 

Parameter EPA ERE EPA(new) 

Dispensed,Fuel Temp., deg F 88+/-2 88+/-1 88+/-2 

Temp. Differential, deg F 

(Tank - Dispensed) 

max. + 5 average 0 +2 to +5 

range +/-2 

Level Prior to Fill, % tank 10 10 10 

Filling Rate, gpm 7 to 11 6 to 10.5 8 to 10 

Fill, % tank 10 to 95 10 to 95 10 to autoshutoff 

The placement of the refueling emissions test in the 

current Federal Test Procedure (FTP) is shown in Figure 4 and 

outlined below. 

1. The test begins with the refueling capacity test. In this 

test, the vehicle is refueled inside the SHED from 10$ of 

tank volume to 95$ of tank volume. The target parameters are 

88°F dispensed fuel temperature and a 0°F delta T. Since 

preconditioning of the canister was not specified by EPA but 

only stated as "EPA assumes vehicles will be driven in a 

representative manner until (the) fuel level reaches 10 

percent", the canister was purged on a bench rig until the 

weight was such that breakthrough would occur during the 

second refueling. This was not a dry canister condition. A 

dry condition would have resulted in requiring three to four 

refuelings for breakthrough to occur at 10 gpm. Saturation 

would require more. This resulted in savings in both time 

and test fuel. 
- 13 -

Finure 4 

P.81 

Invlroitnw-ntal Protection Agency 9M.130-7I 

run DRAIN t mi 

I 

DVNO miCONOlDONINC 

I 

CCHO SOAK PARKING 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

L . 

r* 

i 

i 

I 

I 

FUtllNG 

• ORAIN 

• 40% tU 

I 

DIURNAl MIAt IUIID 

• MAT run-1 HOUR 

• 40l4*f 

IVAP. UST 

NOT RtO 

OIURNAl 

INClOSURt 

TISt 

T333I 

COID START f XHAUST TIST 

} 

} 

I HOUR MAX 

1 MIN. MAX. 

Refueling Capacity Test 

Saturate canister 

(Two full refuelines; 

1st one is 

95%fill test) 

> »? 36 HOURS 

(no mo., lo* 

dittrlt) 

Disconnect canister 

Reconnect 

IVA T HSt 

NOT 

•IRFORMfD 

HC RUNNING 

IOSSIS-AS RIO 

} 0-1 HOUR 

i r 

HOT START I XHAUST TIS1 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

HOI SOAK 

INCIOSURI 

TtST 

CNO 

} 

} 

10 MIN 

7 MIN. MAX 

Figure I/ I is "in SIOUINCI 

Refueling Purge Test 

Sequential IA-4c end 

hot socks 

(Drive down to 10?) 

30% fill test 

53-124 O-li503 
14 -

If only refueling emissions were to be determined, the 

test ended here, otherwise it continued. 

2. After the capacity test, additional refuelings were conducted 

until breakthrough occurred. Breakthrough was determined by 

observing the obvious sharp increase in the SHED HC 

concentration vs time recorder trace. The refueling then 

continued until the tank was full. These additional 

refuelings were conducted from an empty tank. The SHED HC 

concentration at the end was usually greater than 100 ppm C6 

or about 1.3 grams per gallon (g/g). EPA's criterion of a 3 

fold change in HC concentration to indicate breakthrough is 

unrealistic. The hydrocarbon concentration increasing 

smoothly from a background of 1 ppm to a final value of 3 ppm 

does not indicate breakthrough. The hydrocarbon concentration increasing from a background of 10 ppm to a final value 

of 30 ppm may indicate breakthrough. It is our experience 

that breakthrough is indicated by an obvious sharp increase 

in concentration after a period of only minimal increase. A 

recorder is very helpful. 

3. The normal FTP tests for diurnal, tailpipe, and hot soak 

emissions were then performed including the overnight soak. 

The refueling canister was disconnected during the filling 

and draining of the 40$ tank fill required for the normal 

FTP. It was connected for the soak and FTP. 

4. The refueling purge test was then conducted. This consisted 

of driving sequential LA-4's and hot soaks until the tank 

volume was 10$. The hot soak for the Dodge was one hour and 

for the Pontiac 10 minutes. Since the running time for the 

Dodge was about 18 hours, it required two shift a day 

operation. The vehicle soaked with the canister plugged for 

the third shift. The drivedown was conducted in the 

Controlled Temperature Room with proper air flow over the 

vehicle. Without proper air flow as on a normal Clayton 

dynamometer, excess heating of the fuel tank could occur and 

bias the results. The tank temperatures on both vehicles 

matched those obtained on the road. After reaching 10$ of 

tank volume, the refueling emissions for a a 10$ to 40$ 

refueling were measured. 

In Aug 22, 1985, EPA published a revised draft test 

procedure for the measurement of refueling emissions. The 

main differences from the above draft test procedure was the 

change in the refueling capacity test (item 1) from 10 to 95$ 

to 10$ to auto-shutoff of the automatic nozzle with a minimum 

of 85$ fill. Therefore, at the end of this study, a limited 

number of tests were conducted to auto-shutoff of the nozzle. 

The tests were conducted in a randomized order to 

reduce any test order effect. 
P.83 

- 15 

Fuels 

Since previous studies (2,3) have shown that refueling 

emissions correlate with only the RVP of the test fuel and not 

any D-86 distillation points, the test fuels for this program 

were blends of Indolene and butane. Two different batches of 

Indolene were used. The inspections of the test fuels taken from 

the fuel conditioning cart just before the tests are given in 

Tables A3 and A4, and the RVP of the two blends is summarized 

below. 

avg. 

std. dev... 

N 

9 

Batch 1 

8.87 

0.24 

27 

RVP 

RVP 

Batch 2 

9.55 

0.18 

14 

Table 3 

of Test Fuels 

10.5 RVP 

Batch 1 Batch 

10.45 10.94 

0.19 0.24 

18 11 

2 

12 RVP 

Batch IBatch 2 

11.63 11.83 

0.20 0.30 

25 24 

2 "An Experimental Study of Vehicle Refueling Emissions" 

Hochhauser and Campion, SAE Paper No. 760307, Feb. 1976 

3 "A Study of Variables that Effect the Amount of Vapor Emitted 

During the Refueling of Automobiles" API Report No. CEA-21, 

May,,1975 
P.84 

16 -

RESULTS 

Refueling Emissions 

98+$ control of refueling emissions was achieved with 

both the one and two canister onboard systems. The data is 

summarized in Figures 5 and 6. The baseline refueling emissions 

are given in Table A5, while the controlled refueling emissions 

are given in Tables A6 and A7. On both the 9 and 10.5 RVP fuels, 

the Dodge averaged 0.04 g/g or 99.3$ control. The Pontiac 

averaged 0.07 g/g or 98.9$ control on the 9 RVP fuel and 0.10 g/g 

or 98.8$ control on the 10.5 RVP fuel. Since the degree of 

control with the 9 and 10.5 RVP fuels was high and the variation 

between runs approached the limits of measurement, more runs were 

conducted with the 12 RVP fuel. With the 12 RVP fuel, the Dodge 

averaged 0.09 g/g or 98.8$ control and the Pontiac averaged 0.16 

g/g or 98.4$ control. (The percent control is based on baseline 

refueling emissions and not on the loading on the canister which 

was higher.) 

Effect of: Auto-Shutoff 

In the latest version of the test procedure, EPA 

changed the refueling from 10$ to 95$ to 10$ to auto-shutoff of 

the nozzle. As can be seen in Table 4, there is no effect of 

fueling to autoshut off with both vehicles. The Dodge averaged 

0.09 g/g while the Pontiac averaged 0.18 g/g. 

No spitback was noticed in the eight plus runs. 

Spitback would not be expected if spitback is caused by a 

temporary higher than normal pressure in the fuel tank at the end 

of the fill. This temporary high pressure could be caused by 

covering the vapor exit line-with liquid gasoline at the end of 

the fill. Without a low pressure drop exit path, the rising 

liquid level and the force of the incoming liquid would increase 

the pressure in the tank. Then when the nozzle is shut off, the 

pressure in the tank is relieved by "spitting" back out the 

fillpipe. The vapor line could be covered with liquid if it 

exited the tank on the side of the tank near the full tank liquid 

level or inside the fillpipe as with the Pontiac. Since the 

vapor line in both onboard vehicles exit the tank from the top of 

the vapor dome, the vapor line cannot become covered with fuel. 

The vapor line to the canister was located in the dome, 

therefore, to both reduce entrained droplets and to reduce any 

probability of spitback occurring. 

It should be mentioned that it was possible to fill the 

production Pontiac's tank with 29 gallons or 116$ at 

auto-shutoff. Therefore, the 113$ shown in Table 4 was expected. 
Figure 5 

^ 

O* 

nndge 600 Refueling Emissions 

10-

9-

m 

8-

7-

6-

6 

4 -

3-

2-

1 

0 

EZ2 Production 

CZI On-Board Control 

• 

12.0 

I

oo 

u. 
Flgur* 6 

Pontiac Refueling Emissions 

10-

9-

8-

7-

6-

V7Z\ Production 

I—| On-Board Control 

CO 

I 
0671-T-GSM 

TABLE a 

FFFFtT OF AIITO SHUT-OFF 

12 RVP 

CAR. 

44 

10 - 95Z HILL 

fi/G. 

0.09 98.8 79 

99 

100 

100 

100 

97 

Z 

z 

z 

z 

z 

z 

ML 

0.01 

0.04 

0.03 

0.35 

0.08 

0.09 

0.13 

99.9 

99.5 

99.6 

95.6 

99.0 

39*& 

98.9 

1.6 

JD88 

88 

89 

88 

89 

88 

AVERAGE 

SX 

JL 

0 

-1 

0 

0 

-2 

-1 

£HL 

8.2 

9.5 

9.6 

10.8 

9.9 

I 

103 0.16 98.4 113 

113 

Z 

z 

0.15 

JL2& 

98.5 

SL1 

88 

87 

0 

1 

10.1 

10.2 

0.18 

0.04 

98.2 

0.4 

AVERAGE 

SX 

loo 

*H 
P.88 

20 

Effect of Rollover/Overfill Valves 

As can be seen in Table 5, the addition of the 

combination vapor-liquid -separator, rollover valve, and overfill 

valve did not adversely affect the refueling emissions of the 

Dodge. Without the combination valve the refueling emissions 

averaged 0.09 gpg and with the valve 0.02 gpg. Since the 

combination valve was designed for minimum pressure drop, this 

was expected. It also did not affect automatic nozzle shutoff. 

REFUELING 

Without 

GPG $ 

Table 5 

EMISSIONS WITH COMBINATION VALVE 

(10 to 95$) 

GPG 

0.01 

0.03 

With 

$ TD DT 

99.8 88 4 

99.6 89 -1 

GPM 

10.0 

9.7 

average 0.09 98.8 0.02 99.7 

Effect of Canister Size 

The effect of canister size on the refueling emissions 

was briefly studied on both vehicles. The data is presented in 

Table A8 and is summarized in Figure 7. As can be seen from 

Figure 7, and as is expected;, the refueling emissions may be a 

function of the size of the canister expressed as liters of 

charcoal per gallon of tank volume. The slightly oversized 5 1. 

canister for the Dodge, 0.36 liters of charcoal per gallon of 

tank volume gave 98.8$ or 0.09 gpg. The slightly undersized 5 1 

canister for the Pontiac, 0.20 1/gal, averaged 96.9$ or 0.30 gpg 

although it varied from 94.5$ to 98.2$. Considering the limited 

number of tests, and the variation in results experienced (99.8$ 

to 97.7$ for the Dodge), care should be taken in applying this 

relationship. 

There is a trade-off between canister size, cost, and 

operability. The mechanical seal approach may allow the use of a 

smaller canister but adds the complexity and expense of the 

mechanical seal and pressure relief. The liquid seal is less 

complicated and expensive than the mechanical seal but requires a 

slightly larger canister. The no seal approach does require a 

slightly larger canister but has no other additional cost. It 

also has the advantage of not changing the customer's perception 

of refueling. 
FIGURE 7 

Effect of Canister Size on Refueling Emissions 

12 RVP 

0.3 A 

c 

.o 

c*v 

E 

CO 

C 

.2 

<0 

jn 

D) O.H 

0.2 H 

0.0-f 

I 

ro 

—r~ 

0.2 

—r~ 

0.3 

—r" 

0.4 

Liters of Charcoal per Gallon Tank Volume 

I

oo 

(O 
TABLE 6 

REGULATED TAILPIPE EMISSIONS 

» between numbers denotes statistically significant at 90$ confidence level 

Do Igo 

Base 1Ine 

Controlled 

Pont 1ac 

Baseline 

Controlled 

9 RVP 

2.285 

2.377 

3.424 

2.732 

C0^g/m 

10.5 RVP 

2.235 

2.823 

» H.333 » 

« 

* 3.570 

12 RVP 

2.580 

3.200 

5.398 

* 

3-647 

9 RVP 

0.126 

II 

0.157 

0.231 

0.254 

HC, g/m 

10. 5 RVP 

0.10 2 

« 

0.167 

0.23 1 * 

» 

0.30 2 

12 RVP 

0.134 

« 

0.159 

0.282 

» 

0.335 * 

9 RVP 

0.614 

« 

0.70 3 

0.51 2 

tt 

0.578 

N0xt g/m 

10. 5 RVP 

0.60 1 

tt 

0.68 6 

0.51 1 

II 

0.65 2 

12 ftVP 

0.67 2 

0.71 1 

0.48 0 

« 

0.64 4 

i 

ro 

ro 

i 
P.91 

23 -

Tailpipe Regulated Emissions 

The data on the regulated tailpipe emissions is 

summarized in Table 6. More detailed data is given in Tables A9, 

A10, A11, and A12. The Dodge met the 9 RVP tailpipe regulated 

emissions on a 11.8 RVP fuel. Both the production and Onboard 

Pontiac met HC and N0X standards but not the CO standard on the 

11.8 RVP fuel. The Onboard vehicle met the CO standard on the 9 

RVP fuel. 

As shown in Table 6, there are varying responses to RVP 

and to the addition of the refueling canister. The tailpipe 

emissions of both the production and modified Dodge exhibited 

little response to RVP. Comparing the production vehicle and the 

onboard vehicle, there is a numerically small but statistically 

significient increase in HC and N0X emissions (at the 90$ 

confidence level). CO emissions had too much variation to be 

statistically significient. The Pontiac was different. The CO 

and HC tailpipe emissions of both the production and modified 

Pontiac exhibited a response to RVP. The CO emissions increase 

with increasing RVP. However, the levels for the onboard Pontiac 

are lower. . Comparing the production vehicle and the onboard 

vehicle, there is a numerically small but statistically 

significant increase in HC and NO„ emissions but a large and 

statistically significient DECREASE in CO emissions. 

The varying response to RVP probably reflects the 

different fuel systems: throttle body fuel injection vs 

carburetion. In other API sponsored studies (4), fuel injected 

vehicles exhibited less response to RVP than carbureted vehicles. 

The decrease in CO for the Pontiac with the onboard canister 

reflects the increased HC adsorption capability as will be seen 

later in the evaporative emissions. At this time, no reason is 

known for the increased N0X emissions. 

No attempt was made to modify the purge schedules 

since this would require reprograming the control "chip". Since 

the production purge rate did adequately purge the canister, it 

was not changed. It may be possible to obtain better emissions 

with the purge logic optimized for the larger canisters, 

especially with the Pontiac. As discussed earlier, the purge 

stream in the Pontiac, if all hydrocarbons, would result in a 

loss of air-fuel ratio control. 

API Report No. 4406 April 1985 

" Study of Factors Influencing Evaporative Emissions From 

In-Use Automobiles" 
Figure 8 

Effect of RVP on Evaporative Emissions 

for Production and On-Board Vehicles 

12-t 

tn 

E 

VI 

C 

in 

I ' 

I* 

Uj 

10-

8-

6-

Legend 

GS9 On-Board 

CZ) Production 

Dodge Pontiac 

9 RVP 

JBQ 

Ooaae 

ro 

\STANDARD\ 

_ 

Dodge Pontiac 

10.5 RVP 

Dodge Pontiac 

12 RVP 

} 
r* 

IJJ TABL 

CO 

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P.94 

- 26 

Evaporative Emissions 

The data on the evaporative emissions is summarized 

in Figure 8 and Table 7. More detailed data is given in Tables 

A9, A10, A11, and and A12. As shown in Table 7, there are 

varying responses to RVP and to the addition of the refueling 

canister but the addition brought both vehicles into compliance 

with a 2 g/T target on the 12 RVP fuel. On the production 

vehicles designed for 9 RVP, the Dodge was higher than 2 g/T on 

the 12 RVP fuel and the Pontiac was higher on the 10.5 RVP 

fuel; This demonstrates the ability of the onboard system to 

control excess evaporative emissions. 

For both vehicles, the addition of the refueling 

canister decreased the evaporative emissions (statistically 

significant at 90$). Although the hot soak emissions for both 

vehicles tended to have a a numerically small but statistically 

significant increase, this was overwhelmed by the large decrease 

in the diurnal evaporative emissions. 

• The production vehicles exhibited a strong response to 

RVP. The onboard vehicles did not. This is to be expected when 

the canister has enough capacity. Any RVP effect should appear 

only when breakthrough occurs. 

Canister Purge Drivedown 

The last portion of the draft test procedure is the 

refueling purge test. The average canister performance during 

the drivedown is given in Figures 9 and 10. The data indicate 

that if the purge system can remove enough hydrocarbons to handle 

the diurnal, then it will be able to handle the 10 to 40$ 

refueling long before the 30$ fuel is consumed. By calculation, 

it takes 12 to 15 LA-4's to consume 30$ of the tank capacity. By 

3 to 4 LA-4's, the production purge system has removed enough 

hydrocarbons to adsorb the 30$ refueling emissions. 

The Pontiac with the canister closer to the tank in the 

trunk has higher loadings during the overnight soak and diurnal 

tests (see Figures 9 and 10). The Dodge with the canister in the 

engine compartment had much lower loadings taking the smaller 

fuel tank into account. It is felt that further gains could be 

made with the Pontiac if the vehicle were converted to a one 

canister system. 

Effect of Dispensing Flow Rate 

The refueling emissions of the Dodge improved with 

increasing fuel dispensing rate. As the flow rate increased by 

one gpm, the refueling emissions decreased 0.03 gpg (97$ 

confidence-12 RVP fuel only). The Pontiac showed no dependence 

of the refueling emissions with fuel dispensing rate. 
FIGURE 9 

100 

E 

o> 

o 

i . 

o 

X I 

< 

Cl 

XI 

< 

Average Canister Performance 

Dodge 

tf)(ONCOO»O^M at. at* a*. :*.:*• . «- -*L «— 

ro 

•co 

Icn 
oooooooooooo o 

I • I I I • I . I I I • I I I I I I I 

CD 

CZ 

82 -

9 6 d 
P.97 

- 29 -

APPENDIX 
TABLE A-l 

PURGE FLOW RATES 

DODGL 

STEADY STATE AT 25 MPH 

35 MPH 

50 MPH 

.ACTUAL 

0.90, 0.92, 0.77 

3.82, 3.77 

5.38, 5.30 

LOSS OF A/F COHTROL 

6.2 L/M 

10.8 L/M 

16.1 L/H 

co o 

AVERAGE OVER LA-4 1.2, 1.4, 1.4 L/M 

CO 

oo 
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in oo oo 

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555 

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C/5 
- 32 

P.100 

TABLE A-3 

N 

Avg 

' 9 

Sx 

q DUD 

7 

8.90 

9.09 

8.88 

8.99 

9.10 

8.97 

8.85 

8.90 

8.77 

9.10 

8.35 

8.96 

9.26 

9.20 

8.92 

8.58 

8.61 

8.73 

8.77 

8.83 

8.74 

8.80 

8.42 

8.42 

9.04 

9.04 

9.16 

27 

8.87 

0.24 

RVP 1 DF TEST FUELS 

10.5 RVP 

10.42 

10.33 

10.64 

10.73 

10.40 

10.37 

10.62 

10.36 

10.52 

Batch 1 

10.45 

10.74 

10.12 

10.33 

10.67 

10.14 

10.23 

10.41 

10.63 

18 

.10.45 

0.19 

Batch 2 

11.37 

11.46 

11.58 

11.62 

11.69 

11.56 

11.65 

11.67 

11.76 

12.05 

11.33 

11.68 

11.18 

-

12 RVP 

11.44 

11.44 

11.90 

11.72 

11.69 

11.69 

11.86 

11.56 

11.74 

11.85 

11.82 

11.44 

25 

11.63 

0.20 

N 

Avg 

sy 

9.67 

9.48 

9.50 

9.48 

9.67 

9.50 

9.98 

9.57 

9.66 

9.34 

9.55 

9.25 

9.64 

9.37 

14 

9.55 

0.18 

10.68 

10.89 

11.04 

10.68 

10.89 

11.04 

11.33 

11.33 

11.05 

10.67 

10.72 

11 

10.94 

n

 24 

11.74 

12.11 

12.19 

11.64 

11.62 

11.56 

11.62 

11.77 

11.62 

11.56 

11.39 

11.60 

11.72 

12.11 

12.19 

12.02 

24 

11.83 

0.30 

11.64 

11.74 

12.37 

11.54 

12.26 

12.49 

11.97 

11.68 
P.1 

" ' • •>- i 

-

HOHINAL RVP 

BATCH NO. 

IPB 

T 5Z EVAP °P 

T 10ZEVAPOP 

T 20Z EVAP °F 

T 30Z EVAP °F 

T 40Z EVAP °P 

T 50Z EVAP °P 

T 60Z EVAP °P 

T 70Z EVAP °P 

T 80Z EVAP °P 

T 90Z EVAP °P 

T 95Z EVAP °F 

FBP 

GRAVIPf, LBS/GAL 

- 3 3 • 

TAW f A-4 

TPSTPtlfi mspfCTiONS 

9 

1 

86 

113 

134 

172 

200 

216 

228 

238 

258 

276 

320 

349 

394 

6.181 

9 

2 

90 

111 

130 

167 

196 

215 

228 

237 

253 

276 

320 

349 

392 

6.148 

1SL1 

1 

83 

104 

122 

159 

192 

212 

226 

237 

250 

274 

315 

345 

395 

6.154 

2 

81 

108 

129 

166 

196 

215 

228 

238 

253 

276 

320 

349 

388 

6.122 

12 

1 

80 

100 

114 

156 

190 

211 

223 

234 

248 

270 

311 

347 

392 

6.129 

12 

2 

77 

97 

113 

156 

191 

212 

228 

236 

250 

274 

315 

344 

393 

6.100 
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TABLE A-6 

REFUELING EMISSIONS 

DQDGL 

9 RVP In. D I GEB. 10.5 RVP I& D I GEfl. 12 RVP I& D I GEfl. 

GZGAL Z GZGAL Z fiZGAL Z 

0.04 99.3 88 0 7.5 0.06 99.1 89 -1 6.6 0.24 97.0 89 1 6.3 

0.04 99.3 88 0 7.4 0.04 99.4 89 0 9.7 0.08 99.0 88 0 6.1 

0.03 99.5 88 0 9.7 0.18 97.7 88 0 6.5 

0.14 98.2 89 -1 4.4 

AVG 0.04 99.3 0.04 99.3 0.09 98.8 

SX 0.00 0.0 Q.02 0.2 0.07 1.1 

. 

CO 

cn 

0.03 99.6 87 1 9.5 

0.03 99.6 88 0 10.3 

0.01 99.8 88 4 10.0 

0.03 99.6 89 -1 9.7 

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TABLE A-8 

• 

JttHIOL 

44 

44 

103 

103 

VOLUME 

5 

3 1/2 

7 1/2 

5 

EFFECT OF CANISTER SIZE ON REFUELING EMISSIONS 

12 RVP 

LITERS OF CHARCOAL 

PER GALLON TANK YQUfflE 

0.36 

0.25 

0.30 

0.20 

• 

G/G 

0.09 

0.12 

0.21 

0.11 

0.15 

0.19 

0.16 

0.04 

0.16 

0.53 

0.19 

0.17 

0.30 

0.20 

% 

98.8 

98.5 

97.3 

98.6 

98.0 

97. G 

98.0 

0.6 

98.4 

94.5 

98.0 

98.2 

96.9 

2.1 

la DI 

• 

GPM 

AVERAGE OF 8 RUNS 

88 0 

88 0 

89 -1 

88 -1 

89 -2 

AVERAGE 

SX 

10.1 

9.5 

10.3 

10.1 

10.1 i 

i 

AVERAGE OF 10 RUNS 

88 2 

89 0 

88 1 

AVERAGE 

SX 

9.4 

9.8 

10.3 
0377-V-GSM 

TABLE A-9 

AVERAGE 

SX 

CO 

G/M 

1.910 

1.863 

2.831 

2.531 

2.285 

0.18 

• Stall 

HC 

G/M 

0.135 

0.103 

0.119» 

0.110 

0.126 

0.02 

at start 

9 RVP 

NOx 

G/M 

0.593 

0.607 -

0.616 

0.611 

0.611 

0.02 

DIURNAL 

G/T 

0.13 

0.50 

0.11 

0.22 

0.32 

0.18 

- not included 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.17 

0.13 

0.17 

0.17 

0.16 

0.02 

in averc 

TOTAL 

G/T 

0.30 

0.63 

0.61 

0.39 

0.18 

0.16 

ige. 

CO 

G/M 

1.911 

2.755 

2.039, 

2.235 

0.15 

BASELINE REGULATED EMISSIONS 

HC 

G/M 

0.117 

0.111 

0.017 

0.102 

0.05 

DODGE . 

(2K MILES) 

10.5 

NOx 

G/M 

0.616 

0.612 

0.515 

0.601 

0.05 

RVP 

DIURNAL 

G/T 

0.33 

0.62 

0.80 

0.58 

0.21 

• 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.17 

0.18 

0.15 

0.17 

0.02 

TOTAL 

G/T 

0.50 

0.80 

0.95 

0.75 

0.23 

CO 

G/M 

2.010 

3-380 

2.350 

2.580 

0.71 

HC 

G/M 

0.121 

0.159 

0.120 

0.131 

0.02 

12 

NOx 

G/M 

0.638 

0.615 

0.732 

0.672 

0.05 

RVP 

DIURNAL 

G/T 

3.95 

2.35 

0.65 

2.32 

1.65 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.25 

0.21 

0.18 

0.22 

0.01 

TOTAL 

G/T 

1.20 

2.59 ' 

0.83 to 

00 

2.51 

1.69 

cn 
0377-V-GSM 

TABLE A-10 

REGULATED EMISSIONS 

DODGE 

5L RCS 

9 RVP 10.5 RVP 12 RVP 

AVERAGE 

SX 

CO 

G/M 

2.251 

2,030 

2.817 

2.377 

0.12 

HC 

G/M 

0.131 

0.112 

0.191 

0.157 

0.03 

NOx 

G/M 

0.665 

0.728 

0.716 

0.703 

0.033 

DIURNAL 

G/T 

0.66 

0.31 

0.55 

0.51 

0.18 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.39 

0.31 

0.35 

0.35 

0.01 

TOTAL 

G/T 

1.05 

0.62 

0.90 

0.86 

0.22 

CO 

G/M 

2.183 

3.163 

2.823 

0.181 

HC 

G/M 

0.161 

0.173 

0.167 

0.008 

NOx 

G/M 

0.617 

0.751 

0.686 

0.097 

DIURNAL 

G/T 

0.26 

0.31 

0.30 

.06 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.26 

0.31 

0.30 

0.06 

TOTAL 

G/T 

0.52 

0.68 

0.60 

0.11 

CO 

G/M 

3.211 

3.187 

3.200 

0.019 

HC 

G/M 

0.139 

0.178 

0.159 

0.028 

NOx 

G/M 

0.717 

0.705 

0.711 

0.008 

DIURNAL 

G/T 

1.06 

0.23 

0.61 

0.59 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.19 

0.25 

0.22 

0.01 

TOTAL 

G/T 

1.25 

0.18 

0.86 

0.51 

i 

1 

CO 

4 
Si 

< 

ft. 

o 

a 

g 

a. i

d 

n 

z b 

si 3= CO 

d d i n CTV oo f - CM CM 

OK OK m ro 

O"" t—vO C— 

rovo in o 

r- COCM i-H 

ON 00 VO OK 

3-K133-

ooo o 

oo\o o 

OK O iH i n 

vo COCM o 

C— ON OK OK 

mm o ro 

in a- in in 

d o d d 

CM3-

00 Q CM O O o 00 . -

OK O 

roo in3.67 o 2.70 o in 

i n o o o 

t^o > 

rHVO 

m c M in o o d 

in o> mo o 

roroo -=x 

CM CM CM CM 

CD CD CD CD 

OOCM CM O O O 

8S 

-co m'CM 

• 00 C-- OK 

• in ON CM 

rot

m 

-

COCM 

O 

a. c

> 

c 

z o 

II o 

r— OK t*~ Ov CO 

VO VO CM O O 

r* r* ,H «- CM 00 

vo oo crv cr> in 

KIST mo in 

o o o L d • H i-ioo CM i n 

HlMOOCd S •H <H O O rinvo moo oo H o t— in o in in-3- in in d o o d o 

m .-

t— ro «- o CM t - vo CM d d 

.- r o 

r- CM CM .- m in o d d 

in ooo ro o 

in iH CM ro m 

H CM CM CM m 

o o o d o 

rovo CM O O O 

c-

r o 

O 

vOCONO--

O CM r-HOO 0> 

CM in Ov r-v o 

rn roro CM r o 

CMiT m o AVERAGE SX 

"w -"!-"j-»vr;Tg.. '.• ••"•.•• 
0377-V-GSM 

TABLE A-12 

REGULATED EMISSIONS 

PONTIAC 103 

7.5L RCS (ECS)" .' 

9 RVP 10.5 RVP ' 12 RVP 

AVERAGE 

SX 

CO 

G/M 

2.936 

2.528 

2.732 

0.288 

HC 

G/M 

0.272 

0.236 

0.251 

0.025 

NOx 

G/M 

0.615 

0.511 

0.578 

0.052 

• 

DIURNAL 

G/T 

0.82 

0.50 

0.66 

0.23 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.97 

0.95 

0.96 

0.01 

TOTAL 

G/T 

1.79 

1.15 

1.62 

0.21 

CO 

G/M 

3.567 

3-573 

3-570 

0.001 

HC 

G/M 

0.305 

0.299 

0.302 

0.001 

NOx 

G/M 

0.661 

0.612 

0.652 

0.13 

DIURNAL 

G/T 

0.51 

0.66 

0.59 

0.11 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.73 

1.03 

0.88 

0.21 

TOTAL 

G/T 

1.21 

1.69 

1.17 

0.32 

CO 

G/M 

3-391 

3.101 

1.115 

3.617 

0.131 

HC 

G/M 

0.369 

0.320 

0.317 

0.335 

0.029 

NOx 

G/M 

0.623 

0.632 

0.676 

0.611 

0.028 

DIURNAL 

G/T 

0.55 

0.99 

0.65 

0.73 

0.23 

EVAP 

G/T 

HOT 

SOAK 

G/T 

0.80 

1.08 

1.03 

0.97 

0.15 

TOTAL 

G/T 

1.35 

2.07 

1.68 

1.70 

0.36 

T l 

CO