I'm planning on installing a 12" x 33" 16 gallon spun aluminum fuel tank in my rail. My engine is injected, so of course it will be fed with a high pressure fuel pump and running a return line back to the tank.

My question is, does it make any difference where the return line routes the fuel back into the tank? The vendor I'm buying the tank from will add a return bung and says these are typically put in the top of the tank-- but he can't give me a technically sound reason why. I assume the fuel inside the return line is still at fairly high pressure and squirts back into the tank with a fair amount of force correct? Would it be better to position the return line in the bottom of the tank and therefore subdue this fuel stream somewhat?

For EFI you need a fuel tank with a sump at the bottom. It keeps the fuel pump from starving during hard movements. On mine. the return and the supply are in the sump.

I think Outback can weld a sump onto existing tanks and can sell you a new tank with the sump on it.

Here is the picture of the tank I bought ( from somewhere other than Outback because at the time I didnt know better):



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Im sure others that know way more than me will chime in to help!

Good luck!

What he said.The sump method is most prefered but not necessary.You can run line back to tank in any fashion you want,just make sure you dont run tank to low or you will suck air without the sump.

I'd recommend staying away from the spun aluminum tanks. Mine had a very nice sump in it, but was starting to really get dented in where the 2 straps held it down. So rather than risk a rupture and fire, I threw it away and replaced it with an RCI fuel cell from Summit.

It was 16 gal, cost less than $250, comes with a built in sump, fuel gauge sender (very accurate overall), return line and vent with a rollover valve and fuel filler with cap. If I do have a rollover, it's nice to know leaking fuel will not be a big issue.

I had the fuel filler cut and mounted up higher and a nice clear hose connects it. When we go on a ride, no sloshing out, no fuel dribbling or smell. I've also run it down faily low and it's never once lost suction (I have a fuel pressure gauge on the dash.)

What ever you do, make sure the tank has baffles or foam in it if you're going to fun fuel injection. One gulp of air will cause your engine to fall flat for a second of two... very aggravating.

Zilla

I'm guessing that a few decent size holes (1/2" or so) are drilled in the bottom of the tank prior to welding the sump housing in place correct? That way, it would help keep the sump full and be somewhat slosh resistant.

Does anyone know if my assumption here is correct? Guess I could call Outback tomorrow to verify.

I didnt think to look in the bottom other than to make sure I cleaned it out. I would think its mostly cutout, but I dont know.

Again, that pics not from Outback, but I know he added a sump to one of my friends existing tank.

I've known some fabricators to drill a bunch of holes, some to just drill out the bung to about 1/2" or so...and other that simply weld on the sump.

As long as the sump is big enough for the motor and the hole is big enough to feed the sump it's fine. The more surface the better the sump will do at keeping fuel near the pickup....but the more holes the easier it will be for it refill the sump as fuel sloshed around. Give a little here get a little there kind of deal.

The return can go just about anywhere. Some say returning it to the sump is a bad idea because the return fuel is warmer and you can end up heating the fuel enough to cause vapor lock that way....unless you're running your fuel lines along your exhaust though I doubt it would be an issue in a buggy. Most OEM setups (maybe all) return to the bottom of the tank to keep slashing to a minimum I assume.

return should go in the top of tank or as high as possible, return fuel can be slightly aerated, also returning in the tank bottom can cause fuel press. variations

If you do mount it on the top of the tank, that'll make the aeration worse. It'll be like a cow pissin' on a flat rock. The changes in fuel pressure is relative more to the temperature of the fuel and not return fuel placement location. The tank itself is kinda like a heat exchanger(a poor one though) with the surface area to get rid of some of the heat. Most all of the OEM stuff sends return fuel down a tube next to the pump but just directs the flow away from the pump pick-up itself.

Sunshine

When I set up my tank I consulted with a few builders and Dose (who did the motor).

The concensus was: sump on the bottom with -8 outlet pointing toward the rear of the car. This is based on the idea that during acceleration, you want the fuel pushed toward the outlet. We returned the fuel on the top with -6 line and placed the return bung directly above the outlet/sump. The idea being, keep the sump full. The key to keeping the fuel cool is in the size of line you use, the bigger the better--restriction=heat.

just my .02

Thanks for all the great feedback and ideas on this topic, as always, I really appreciate it.

I talked to the guys at Outback today and got their recommendation for installing the sump they sell. The sump should be positioned over the outlet bung on the bottom of the tank and a small hole drilled through the tank wall at each of the four corners where the sump intersects the tank. The fuel drains into the tank through the outlet bung, and the holes let any air trapped in the sump return to the tank.