Geoffrey

When I originally built the car, I installed a Fuel Safe 17 gallon fuel cell which was ordered stock with no modifications. I have been having issues with the tank uncovering the pickup under hard braking. At 8 gallons of fuel left, I get a low fuel pressure warning on my dash, only under braking as the fuel moves to the front of the tank and uncovers the pickup (stock tank location). At 7 gallons left, the car runs lean upon application of the throttle after braking. So, basically I can use only 9 or 10 gallons out of the 17 in the tank. Hardly enough for a race environment.

This year I decided to fix the problem. I purchased a surge tank which is nothing more than a square box with 3 check *****. It allows fuel to flow into the surge tank, but not out. I then installed a -8 bulkhead fitting and plumbed it to the blukhead fitting that exits the tank in the bottom (stock tank location) and then to the external fuel pump (stock location). In addition, I added two smaller pumps (from an RS Spyder), one in the bottom of the tank near the outlet, and one in the front of the tank. The purpose of these pumps are to "lift" the fuel into the surge tank to keep it full. This should allow me to run the tank practically dry.

Tomorrow night, I'll wire the pumps through a sealed connector on the top of the tank and then run the wires to the fuel pump relay. This should work out nicely.

deep_uv

Pretty cool, Geoffrey. Are the 2 smaller filler pumps for redundancy, fill speed or both?

Tom W

It looks like the surge tank will be located internal to the existing cell. Why not place it externally and add a gallon or so to the total capacity of the fuel system? I ask because we are trying to decide the approach to take - I've had a problem with starvation after hard turns (with plenty of gas left in the tank).

Geoffrey

The Fuel Safe 964 tank has a design that is limited to retrofitting into the stock location. The center of the tank is higher than the outside and the "well" where the fuel is drawn from, similar to the stock tank design, due to the raised trunk floor (to clear the C4 front diff). The surge tank therefore, is placed higher than other parts of the cell. When running with lots of fuel, this isn't a problem because the checkballs will keep the fuel in the surge tank, but when the fuel level is low, there needs to be another way to get the fuel into the surge tank. This is the purpose of the low pressure "lift" pumps. I installed 2 because one is needed for the well in the rear of the tank, and one is needed in the front of the tank. If I had 3 pumps, I would have installed one in each corner in the front, but I only have 2. I'll wire it for 3.

Tom, are you using the same 17 gallon tank? I didn't really consider the external tank because of space and complexity issues. I don't really want 2 fuel cells in the car, both of which would need bladder replacement every 3-5 years. My tank really needs to be replaced, and when I do next year, I'm going to design one that has a larger capacity but fits in the stock location. This exercise is to see what needs to be done to solve the fuel delivery problem before designing and building a new tank.

pat056

Keep us posted, please. You might remember my Thread on fuel starvation issues. I think I'm closer to solving the problem and will know 2-9-08 when I return to the track. I've heard good and bad opinions about every solution I know possible to this problem...guess it's like elbows everyone got one.
I'm looking at going back to the original set-up in my car which would be from a 12 gallon cell to a 27 gallon. I decided to only introduce 1 variable at a time i.e. I'm solving my pick-up problem 1st, then tackling the new fuel cell w/a retrofit pick-up set-up. Sounds like you're doing the same.
Good luck!

Geoffrey

While I was doing this I remembered your thread, but couldn't remember who was asking, so I posted this thread in hopes that you'd see it.

pat056

When are you on the track next? ever come to CMP, VIR, Rd. Atlanta for NASA events? Will you be at RA for PCA?

Geoffrey

I will be a scrut at RA this year, so not racing it. I'll be at the Mid Ohio club race racing and I will probably go to the BMW VIR club race and drive with the school there.

Tom W

Geoffrey, yes 17 gallon version. I was talking to Rich about the way they had it set up in the car they used in the 25 hour race. They had an external tank that used a second fuel pump (an when the cell went dry, the first pump was shut off and they knew that they had to pit in the next 2 laps). At this point I'm examining the options as I have a few weeks before it would be going in.

FLA997

Geoffrey is a genious....thats incredible!

Geoffrey

Not really. I haven't done anything that hasn't been done in the past

Geoffrey

I finished the wiring and installation of the pumps in the tank. So, what holds the pumps in place? They are held in place by just the foam and the lines are ziptied together so there is limited movement of the pumps themselves. It is important to ensure the pumps don't bounce up and pump air because the'll burn out after awhile.

The first picture is the assembled fuel cell with the foam cut away for the surge tank below and the lines and pumps. Notice the electrical connections for the two pumps.

The second picture shows the electrical connections. I wired bought a 6 pin connector to have a spare lead should I decide to install a third pump, or move the main fuel pump inside the tank when I do the cusom tank next year. The wire covering is a viton covering made to be submersed in the fuel. The connectors are already fuel proof except for the rubber grommets the wires go through, so the rubber was removed so it wouldn't swell. The wire is 20ga wire and capable of 10 amps of current. The pumps draw only 6 amps of current when running (I tested them with my oscilloscope and current probe).

The third picture is simply the external connector which I'll connect to the car wire harness that I still have to make. I'll leave the top off until I put fuel in the tank and remove the center foam to check the operation of the pumps before final assembly.

Alan G.

EASY, he can't afford a new helmet!