I'm trying to get an idea as to what size fuel tank I need for my 914/3.2? If a typical race lasts 15-20 minutes (& I'm not sure that is accurate) how much fuel will I use? Will a 10 gallon tank be big enough? What size r u guys using? Thanks for the info!

we run a lot smaller motor, but with heavy jets and use a ton of fuel for a 2.0/906 motor...

is your set up factory fuel injection ?

so we use about 4-5 gallons in a 20 minute session
we run a 15 gallon cell so we can do enduro's
not much extra weight if you don't fill the tank

the local race shop recommends 10gallon cells for 4 cylinders and 12-15 for 6 cylinders

This is very dependent on the track you are running, percentage of WFO, and track speed. We vary between about 7 mpg down to about 5mpg with a stock 3 liter motor. Takes anywhere from about 5 gallons to 8 for a 20 minute session on average.

I have been using about 5 gallons per 20 minute session with my 3.2, stock FI and a chip but I am slow and WOT is not often.

Knowing what little I do at this point, take time to study how people have located and mounted theirs to keep it low and back as far as possible. Guessing at 6mpg, a ten gallon tank will give 60 miles, and depending on lots of things that should be about 50 minutes or so.
Trick is to be able to scavenge the last of the fuel. I think the best bet would be the 10 gal tank coupled with a 2gal surge tank. Get professional help on this.....its a plumbing maze and double the safety considerations for shutting both pumps off in an accident.

You're guess of 50 minutes for 60 miles is off. That is dependent on average speed at the track. At NHMS, average lap speed is around 72, at Watkins Glen it is 87, Lime Rock is Mont Tremblant is 77. But that doesn't tell the whole story - it really comes down to throttle position and time at wide open throttle.

Brant's suggestion is good provided you can use all the space in the cell.

My well developed 2.7 uses about one litre per minute of track time. A litre is roughly the same as your quart.

Thanks guys I think I'm going to go with a 10 gallon tank initially and will evaluate where to go from there.