split fuel tank design?

Well, my next project on the wagon is an IRS. The current fuel tank is vertically mounted behind the rear axle and will have to be modified to fit the IRS.

So, I was thinking of making a setup like the IRS donor car has. A split tank mounted under the rear seats. My concern is the pickup/sump setup and I'm pretty much clueless. I need something that will work under 1G plus cornering, and it's an EFI car.

I need to get out to a JY and check out the stock t-bird setup- it might be swappable!

thanks for the help!

My 318ti uses something similar. The driveshaft goes through a tunnel in the tank, virtually making it two seperate tanks when under half full.

To deal with this, both sides of the tank have a pickup (only one pump though)

I have an E30 and it has the very problem you are worried about. I think pretty much all cars with that kind of tank arrangement have it. I used to just try to live with it, keep the fuel level above 1/3. But now that the car is heavily boosted, starving it on the track is not an option.

I thought getting a fuel cell was going to be the simplest and most obvious solution. Nope. Most fuel cells aren't even baffled properly (with a flappy door box around the pickup). The ones that are, are the ALMS, NASCAR spec levels, that cost like 6 grand.

I talked to some other racers with big boost. They said the trick is a swirl pot - a relatively small container that is much taller than it is wide. This way, it needs to be nearly empty for the pickup at the bottom to be dry. This pot should be fed by a low pressure, high volume transfer pump from the main tank, and the high pressure pump should pick up from the swirl pot. Then the rail return would go into the swirl pot, and swirl pot overflow back into the main tank. The guys said that you can run the car down to fumes and never starve.

I got a nice bonus having an E30, since the early cars got a high volume transfer pump in the tank and a high pressure pump outside of it. The later cars got a high pressure pump in the tank, and a fuel level sender in the other side of the tank. In their infinite wisdom, BMW made the mounting crown of the pump and level sensor the same. So I got me a late model tank, two transfer pumps into each half of the tank, which feed the swirl pot in the trunk. The car isn't done yet so I can't definitively say it works but I'm confident that it will.

Even if you don't have the luxury of an OEMish solution, the aftermarket low pressure transfer pumps are quite cheap. If you decide to go this route, I recommend this swirl pot that I got. Very well made and you will never be able to get it made for this price in the USA.

http://www.cxracing.com/mm5/merchant.mvc?Screen=PROD&Store_Code=CXR&Product_Code=FST01-86610

Got mine off ebay for 70 bucks:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_rdc=1&item=110622452429&ru=http%3A%2F%2Fshop.ebay.com%3A80%2F%3F_from%3DR40%26_trksid%3Dp3692.m570.l1313%26_nkw%3D110622452429%26_sacat%3DSee-All-Categories%26_fvi%3D1&viewitem=

hmm, interesting. Thanks!

My car starves around 1/4 tank as is. I have to run 1/2 tank or more to keep it from starving on the track.

My DD is a 96 Active ti, and was also wondering what the setup was in that- now I know!

I also forgot I have a spare protege tank in my shed...That's a split tank also.

On a side note: the more I work on the ti, the more I really hate that Ford.

Subaru's have split tanks too. . . at least my 97 Outback has one.

My Esprit Turbo has 2 tanks. The tank with the pickup has a pot a little shorter than a 1 lb coffee can sticking out the bottom. The in-tank fuel pump picks up there. It won't fuel starve at extreme cornering, even if all the gas sloshes over to the other tank. The two tanks are connected together by about a 1" line plus a vent at the top, so the fuel moves quite fast. You can fill both tanks from one side.

I did what I call a "poor man's sump" on Dr.Linda's Megasquirted Sportster. I bought a large metal canister fuel filter with hose barbs on it. I put it under the gas tank so the primary fuel pump (gravity) fills it, and it feeds the EFI fuel pump. It holds about a cup or so. She's never had a fuel starve incident. I read that stock EFI Sportsters can have fuel starve events with low tanks and cornering.