Fuel Tank Surge Swirl Pots

[Rick Iverson]

Gents;

I was thinking about this. Gregg Rice had a fuel swirl pot for sale, designed to prevent fuel starvation under low fuel conditions, especially during high-G cornering, rapid acceleration, and hard braking (the usual suspects).

• is this practical for our applications;
• if so, how large should the external fuel reservoir be, 0.25l, 0.50l......(small is good);
• maximum fuel pressure the FF, FC carburation can handle?

I have done some homework, and this is EASY to fabricate. But the question the begs to be answered, much ado about nothing?

[TimH]

The more fuel I carry the less lead I need...

[EricP]

I think there are better options internal to the cell. Be it flaps, valves, those Holley fuel mats (what I use) or those specialized snowmobile fuel pickups. I know a few people have built fairly sophisticated internal surge boxes or tanks that appear to work well.

the biggest issue I have with an external “pot” is you need (at least what I understand) two pumps. That doesn’t fit my KISS rule.

[problemchild]

I don't think it is necessary for a carbureted car, unless you are trying to get by with a super small cell. The float bowl bleeds out air in the line by design.

With the fuel injected application, the injection system needs a constant FP (45 psi on the HPD FIT). My KISS rule is don't mess with an older fuel cell that does not leak, so I was trying to avoid cutting up my cell to put in a fuel pump. I could not get that to work with an external pump (on 3 different cars) until I started using the swirl pot. I, quite frankly, prefer external pumps, even two, to internal pumps, which often require a days work to service (at the worst times).

[Jerry Kehoe]

On my original Can-Am car I installed Hilborn FI and quickly found out that the Hilborn pumps needed to have a positive head of fuel to keep the system working because if the pump picked up air it had to go through the whole system to get constant fuel flow to the nozzles. It was advised to make a make up tank filled by an electric pump where all of the return lines returned to this tank and it was vented to the main tank to keep a full supply to the Hilborn pump. Kinsler makes one of these that is pretty fancy and expensive but they are not hard to make and I have had no problems and in addition when the fuel level in the main tank is low it helps maintain a positive flow as it is always filled. With carbs and float bowls this is not much of a problem unless your pump really runs out of supply but for FI it is critical for the same reason. To get the theory go to Kinsler's website and it is explained in a detailed manner ( for a constant flow FI system) but the thought remains. Kinsler calls it a Vapor Separator Tank (VST) in their catalog. I don't use the pressurised valve as I have -6 line going in with no pressure from the electric pump and -6 going back to the tank which works fine.

[DaveW]

I made a fuel collector can which fits inside my fuel cell. It's small enough to be inserted through the 4" dia access hole in the back of the cell. It works quite well, with no fuel starvation down to 1/2 gallon remaining. The basis is an octagonal can ~5" tall and 3.5" across with a 2" tall fence that piles the sloshing fuel up against the can. It uses 1/32" thick Viton sheet for the flap valves which let the fuel in and keeps it there. The Zetec fuel return is plumbed into the container. There is a filter at the end of the tube that goes to the fuel pump.

If you want photos (too many to post here), PM with your email and I'll send them to you.

[fitfan]

following...

i'm building a duratec fuel injected formula car (street legal single seater, not a race car), will be fabricating a fuel cell so have a blank slate... was initially thinking just a high pressure pump, but noe thinking that might not be the best solution.

[problemchild]

following...

i'm building a duratec fuel injected formula car (street legal single seater, not a race car), will be fabricating a fuel cell so have a blank slate... was initially thinking just a high pressure pump, but noe thinking that might not be the best solution.

Sticking the fuel pump in the bottom of a 7 gallon cell will pick up 85-90 % of the fuel before getting FP fluctuations in the most aggressive of driving. As you develop your internal baffle system, as Dave describes, and are available from numerous sources, that % value increases. I would love to sell you my hardware, but it does not sound necessary for your application. Whether on a track day, or on the road, just put fuel in it 10 miles sooner.

[fitfan]

Sticking the fuel pump in the bottom of a 7 gallon cell will pick up 85-90 % of the fuel before getting FP fluctuations in the most aggressive of driving. As you develop your internal baffle system, as Dave describes, and are available from numerous sources, that % value increases. I would love to sell you my hardware, but it does not sound necessary for your application. Whether on a track day, or on the road, just put fuel in it 10 miles sooner.

Thanks,
i know the cosworth injection is high pressure. and i don't want any risks with that powerplant. i have some room for a swirlpot and that just seems easier in a number of ways. total fuel (cell) capacity will be an issue as a street car, lots of gaps between fuel stations in big sur or inland for example ( hoping i can get close to 8gal when we fab that up). all that gets me to thinking a low pressure pump pressure warning light on the dash before the swirl pot depletes would be prudent. its not forced induction... but still cant be good to be sputtering out looking for a place to pull over. anyways - the concern is when due to the limited milage per tank gets to the 90% mark.

along with your thoughts are also (i have to check) i believe i can do a pocket on the bottom of the fuel cell, if so that might make an internal baffle box a simple fit.

[ExKartracer]

Back in the Stone Age, I built an ASR with parts out of Dan Gurney's AAR shop. I had a low pressure tank fed by an electrical pump that fed the Kinsler fuel injection. All well and good till a hot summer day at Riverside Raceway in Calif that was hot enough to vaporize the fuel on its return to the low pressure tank. I was racing in a regional/national against Tom Foster at the time. Problem first occurred in practice. I warned him about the problem and he avoided me when it happened in the race. Installed a cooler fed by air under the car to solve the problem.

[Jerry Kehoe]

Thats why all the fuel in my system kept circulating back to the main tank and the return from the main pill was far enough away from any major source of heat to vaporize the fuel. You may remember the guys from Electromotive that gave me the idea to create the tank originally at Laguna at the first Can Am when I ran the car the first time where it farted and popped from turn 4 to exiting turn 9 where the pump got fed fuel again after picking up the air when the fuel ran forward in the low tanks when getting on the brakes at 4. Without those guys who knows how long it would have taken to figure the problem out!

[924RACR]

Back in the Stone Age, I built an ASR with parts out of Dan Gurney's AAR shop. I had a low pressure tank fed by an electrical pump that fed the Kinsler fuel injection.

Very similar to my setup; Facet low-pressure pump to pull from the main cell to the surge tank (made from a small-capacity fuel cell), high pressure feed pump to the regulator, with return to the surge tank only (not the main cell - return to the main cell is only via a top overflow port). Regulator of course supplies to the rail, but it's a returnless system, with the regulator by the surge tank, away from the heat. Filters of course before both pumps. The low pressure "lift' pump is usually sucking air (and yammering away) when I come in (it has plastic pump elements that are designed to run dry without seizing), and there can be as little as 1/2 gal in the surge tank (actually as low as I've had the courage to run it)... works pretty well..