RedlineMan

Hey;

My FI fuel return is where it is because that is where it was before. It did occur to me to move it to the surge, but I really assumed that the return to the tank was not that great, particularly with a WOT. In theory I agree with your surmize, but in practice I'm not sure it makes a big difference. We'll see.

The only significant pressure in the system is after the Bosch pump. The Holley pump is only 7psi. Whatever pressure it takes to move the fuel from main to surge, and then the overfill from surge back to main is all that exists. Since it is an open vent system, I'm assuming that pressure is not that great, perhaps no more or even less than 7psi. Good question?

Given such low pressure, and the open venting, I don't see where the returns stand to fight eachother for supremacy. It's like two eye droppers dumping into the ocean as I see it. Unless the tank was completely full and effectively hydrolocked in terms of venting, then there may be a problem. In fact, I just thought of that. Hmmm... Well, it won't be overfull for long anyway...

Perhaps one of the reasons my old setup did not work is that the surge collector inside the tank is only one-directional. In other words, it only picks up from the right side, and is placed against the left rear side of the cell. I assumed that this would work fine; the fuel sloshes in, then is trapped by the gravity weighted hinged trap doors. Sounds good, eh? Well... it didn't work out that way. Rule of thumb - always be prepared for your "well-thought-out" designs to fail.

Jay Gratton

Bob has a Porsche? I know of the Jeep and the Audi that he loves oh so much, but I didn't know he had a Porsche. Besides, he wouldn't have time to work on a car even if he had one because he is always working on mine and Matt's!

tinman944

John, what size cell did you start out with?

RedlineMan

It's only 12g. That is all that would fit where I wanted it to go.

Like I've said, if I had it all to do over again...

tinman944

how long does 12 gal last you. it should go 20 minutes ..or are you doing enduros also?I thought you where Just a DE guy.

RedlineMan

Hey;

I think it would have easily gone 30-40 minutes if I could have gotten all the fuel out. It would still read 1/8-1/4 after sputtering on track. Sometimes we have combined groups at the end of the day where we can get 45 minute sessions. Sometimes seems that I'm having my most fun when it starts to fizzle, like last year at VIR! Grrrrr......

In any event, it's no fun to lose power in the middle of a fast turn.

tinman944

I have gone back and forth on the idea of just building a tank.
First hold up was I was not sure how many gallons to make it.
Second has always been fear of an accident and splitting a seam on a home built tank.
I have thought of building the tank then send it off to ALT and have a bladder installed .

RedlineMan

Hmmm...

If I had an early (pre 964) 911, I'd be leary of racing without a cell. The front ends are extremely flimsy. I don't see it as nearly the issue in a 944. The tank is pretty well protected.

It's a bundle of snakes, man.

tinman944

You are right about the 911.
at this point I really have no choice.there is nothing back there now to mount the stock one to so I might as well just build an aluminum tank and get it over with.The amount of time that I have been on here lately I could have it done by now.

RedlineMan

If you spend more time thinking, you usually spend less time building. This counts as thinking.

tinman944

LOL

kurt M

....untill the seat you make does not fit! Doh! Would it be easer to purchase an off the shelf bladder and build your tank to it? i ask as i have a standard type cube cell in hand but am not 100% happy with it,(as I am about most off the shelf stuff) I am looking at ways to improve the fit and move the location rearward in the front of a 70s 911. The front end is getting cut hard so made to fit stock location is not needed. Is there prior art on this? what kind of costs are incured in having a co. make a bladder to your in house built cell?

tinman944

944's are a little harder to fit an off the shelf tank. as you can see John fit a 12 gallon tank in his 944 quite nicely.
they make a saddle type tank for 944 but it is 18-22 gallons (I think) I want something that will have enough fuel to run 30 minutes.
and I want it to fit where the weight is needed.

RedlineMan

Around you... or through the door opening?

If you price the generic soft bladder cell from ATL or Fuel Safe at $500-1000, you might imagine anything custom will be prohibitive. Factor in that these bladders have a limited life span... Nah, didn't want to go there myself.

tinman944

Have you ever asked about a custom bladder John.
I did years ago ...have no Idea what the cost would be today.
Yes it is a costley consumable