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OAR Box 1830 

Prepped by Ollie Stewart 

Document Number: 

163) IV-C-130 

Docket Number: 

A-87-11 

Printed 11/13/2008 7:21:00 AM Sheet 163 of 232 
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| A r* UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

l-SS-ir/ ANN ARBOR. MICHIGAN 48105 

OFFICE OF 

AIR AND FIADIATION 

SL; ' 2 1 1988 

Mr. James E. Pasek 

Auto Emission Control 

Environmental Activities Staff 

General Motors Corporation 

• 30400 Mound Road 

Warren, MI 48090-9015 

Dear Mr. Pasek: 

Thank you for the briefing of September 16, 1988 on your 

evaluation of General Motors' simplified onboard refueling 

control system patterned after the system designed by EPA. As 

we have indicated on previous occasions, EPA is most interested 

in evaluations of this concept. This letter is intended to 

confirm some of the observations which we made during the 

briefing as well as to pass on some specific questions which 

remain unanswered following your presentation. 

Perhaps most importantly, it became increasingly clear to 

us as your briefing progressed that the hardware which you 

evaluated performs significantly different from our equipment. 

This can be seen, for example, in your testing of fill quality 

and, of partial fill performance. According to your 

presentation, fill quality was degraded due to frequent 

premature shutoffs and the occurrence of spitback. 

Additionally, you found a significant loss of control for 

partial fill operations. As we discussed with you, neither of 

these two problems have occurred with our hardware. A very 

high quality fill, significantly improved over even the stock 

fuel tank, has been characteristic of our design. As for 

partial fills, we have conducted partial fill testing and found 

that our system works well, unlike yours. Therefore, it 

appears that the GM system is different from the EPA system and 

that results from your testing, while instructive, can not be 

taken to apply to our design. 

We were not able to determine the cause of the poor 

performance of the GM design based upon the limited information 

in your presentation. There are several differences between 
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your hardware and ours, including the placement of the valve, 

hose routing, and canister design. All of these factors affect 

the operating backpressure in the tank during refueling, and 

must be chosen so as to give satisfactory fill performance. It 

appears that you have used sizing parameters selected by EPA 

without adjustment for the hardware differences between the two 

systems. 

In order to speed the resolution of the problems with your 

system, we request that you provide your hardware to us for 

some comparison testing. This would involve some parallel 

tests on both systems to more clearly establish the differences 

in performance between the two. We believe this to be the most 

rapid way of resolving the questions surrounding your 

hardware. Given GM's concerns about the performance of simple 

designs such as ours, you should also find such testing 

valuable. 

Other results presented in your briefing indicated that 

you encountered liquid carryover from the vapor vent/rollover 

valve under various vehicle maneuvering tests. As we 

discussed, after your modifications of the valve, you did no 

testing to determine how well the hand-modified float was able 

to seal the vent opening. Lacking this information, it is 

impossible to determine whether the fuel carryover is a 

ch'aracteristic of your particular design, or whether the valve 

was simply leaking. Nor did you evaluate any solutions, which 

may be as simple as extending the length of the valve barrel to 

provide fuel drainback capability. 

In your presentation, you also made the statement that the 

EPA system can generate 20 times more running loss vapors than 

do pressurized tanks. This statement is misleading, implying 

as it does that the comparison is with the current stock 

version of this system. In fact, to develop this result, you 

modified the stock vehicle and equipped it with a tank pressure 

control valve which pressurized the tank and suppressed vapor 

generation to about l/10th of the stock configuration. 

Compared to the stock car, the EPA design (assuming your 

results in this case to be valid for our design) produced about 

twice the amount of vapors. 

As I noted above, there were a number of unanswered 

questions resulting from your briefing on the General Motors 

onboard system. These questions are included as an attachment 

to this letter. I would appreciate your prompt response to 

these questions so that we can complete our analysis of your 

results. 

I also believe it is important to respond to a matter 

raised in your recent letter of September 15, 1988 responding 
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to my request for a technical briefing on your onboard hardware 

evaluation. In your letter you raised the concern that my use 

of the word "critique" implied that we were approaching our 

analysis with "a predisposition to either discredit or ignore 

General Motors data regardless of its merit." This concern is 

disturbing, given that I have repeatedly emphasized to you in 

previous phone conversations that our interest in a technical 

briefing was premised on the fact that EPA has an obligation to 

objectively evaluate any information or data that relates to 

our deliberations. It is for this reason alone that I 

requested a detailed technical briefing from GM. I assure you 

that your concerns are unfounded and that we will certainly 

evaluate your data on their merit. We have made similar 

briefing requests to other manufacturers and they have 

responded favorably. 

Thank you once again for your presentation. I look 

forward to hearing from you about the loan of your equipment 

for testing and receiving your response to our remaining 

questions. 

Sincerely yours, 

Chester J. France, Chief 

Standards Development and Support Branch 

Enclosure 

ac: Richard Wilson, EPA 

Charles Gray, EPA 

Samuel Leonard, GM 

Docket A-85-21 

Docket A-87-11 

6394W 
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Followup Questions to General Motors' 

Onboard Hardware Briefing 

Partial fill test procedure 

How was nominal capacity defined and what was its 

value 

Provide data on grams emitted per test rather than 

grams per gallon 

Describe topping off procedure including number of 

shutoffs, etc. 

Identify tests where spitback occurred, and when in 

the test it happened 

Identify fill rates for all tests 

Vehicle maneuvering tests 

Identify specific tests performed 

Provide details of the geometry of the installed 

onboard system showing all line grades and lengths 

from the control valve to the canister 

Provide the same details on the liquid loss test 

configuration. 

Estimate the volume of liquid lost as well as its 

weight 

Provide any data you have evaluating the basic 

performance of the float and seal mechanism in the 

modified valve. 

Hot driving under load 

Provide data on ambient temperatures for all tests 

Describe the road route in detail including average 

driving speeds 

Describe vehicle preparation prior to test including 

any driving 

Indicate which portions of the road route were 

driven for each test and exact mileage and times 

Based upon past GM experience with these routes or 

portions of routes, describe the expected effects on 

fuel tank temperature rise above ambient 

Describe the sample collection equipment, including 

all components and physical layout 

Identify tank operating pressure with the tank 

pressure control valve installed 

How does this system control fuel spurting if the 

fuel cap is removed from a fuel tank when hot? 

Identify typical tank operating pressures under 

similar ambient conditions for the tank without the 

tank pressure control valve 

Fill Quality 

Describe specific fill quality tests performed 

Provide quantitative results 

Provide similar data for the stock fuel tank