Nationals and fuel cell

[CSatterley]

I' m there is some difference between events and tracks, but can you make it through a National using a 4 gallon fuel cell.

[FV80]

Generally yes - but you'll have to fill to the top in a few cases (Runoffs at Elkhart being one of them) to be sure. That leads to fuel "expulsion" when the driver sits on the tank ( as many do) and it spills out into the driver's suit
4.5 would do nicely, but I don't know of any between 4 and 5 gals. In most cases, 3.5 will do the races. Just depends on how close you want to play it. Personally, I have a 'fiver' . and have not yet had to fill it "to the top".
Steve

[cendiv37]

3.5 gallons is my typical fill for a race at RA. I've run many races at RA and have never needed 4 gallons to finish. I figure about .2 gal/lap usage then add a bit just for security (or in years of yore, to make weight!). My tank holds just over 4 gallons without taking into account compression when you sit in the car.

As the saying goes, "Your mileage may vary"
In this case, literally...

[brian]

I have a very small tank, 3.6 and ran out once on the cool off lap at RA but it was due to a leaking vent line. Generally I usually end up with a little bit left and always fill the tank to the top. Which reminds me, as a tech person I would flunk a fuel cell that would leak if squeezed or inverted. Steve, what's with that on your cell? Is the cap loose?

[SR Racing]

I have never heard of anyone using more than 3+ in a National, but depending upon your cell design it is possible you could get to the hairy edge and lose fuel pick-up in a long high-g corner.

The initial FST test car with 1600 and 80+ HP ran out of gas on the parade lap in a race one time using a 4 gal tank. The 1600 V.E. is about the same as a 1200 so it should use about 25% more fuel than an FV. We are now all using 5 gal cells and running regionals, but never seem to use more than about 3+ gallons in a session. I really don't think 4 gal would be a problem in an FV in most all cases. (BTW, We usually top our FST off, cause we need the ballast. )

[FV80]

Brian,
*I* don't have that problem, but I've heard that others do (Donnie Isley had it during the Runoffs). The protective shell around my bladder is adequate to keep me from compressing the bladder to any degree, but I've seen some that weren't. As to how the fuel gets into someone's suit, I'm not sure - it's never happened to me and I don't intend to let it happen - possibly the vent tube does not exit the car properly? I have no idea...

As for fuel cell size ... I agree with most that I hardly ever use more than 3 gallons in a race or even a long 30 minute test session. HOWEVER, I have no particular desire to have the engine die out on the track and have to be towed in due to loss of fuel from the pickup. I can fit a 5 gal cell into my car, it costs about the same as a 4 gal cell and I see NO reason to take chances. It also allows me to "play" with ballast a bit if I'm running close on the weekend's (sometimes unpredictable) scales by adding a bit more fuel rather than having to find a place to put more ballast. Interestingly, at the Runoffs this year, my car suddenly weighed almost 15 pounds more than it had weighed all year. It was VERY tempting to take 15 pounds of ballast out of the car ... but I was chicken! I could see it going back to 'norm' if I happened to end up in impound. It's truly amazing to me how much difference there is from track to track on supposedly CERTIFIED scales...

Steve

[brian]

thanks for the update Steve, I didn't think you'd run a car like that. I've seen a lot of cars puke fuel out at the beginning of sessions and it's due to the absence of a check valve. All cells must have a check valve in the vent line to prevent spillage. A cell should hold fuel upside down for obvious reasons. Back in the day before cells, I had a tank loose it's cap during a flip and completely soaked me. Within 30 seconds of the accident, I was standing behind the flagging station draped in a red flag. Not a pretty sight, nor were the blisters from the fuel.

[Gdog]

What kind of vent valves are you guys running ? I am using this roll over valve which fits inside of my vent tube .[ external image ]
It will expell liquid if the cell is filled to the brim but will not leak when turned upside down . I have been behind cars losing fuel on the initial laps of a race and suspect that this is the type of vent used.

Also I am curious what most people use for a pickup inside the cell .

[brian]

I recommend that the vent line be long enough to rise above the cell then loop down to the frame rail. Some folks run the vent line up and around the roll bar. That will prevent low pressure leaking past the vent line.

[MCRacer]

Our local scrutineer had me use the "loop" that Brian mentioned and use a PCV valve at the end of the tube.

Mike