Dual tank EFI set up?

[Jonnyt]

Evening Guys,

My very first post so please be gentle!!

I've just taken delivery of a Tornado GT40 kit so I have lots of shiny bits in the garage. But...

The dual tanks are set up for carbs and I want to go for EFI on this build (351W producing 500BHP at the wheels). I was talking to my engine builder and we got chatting about the fuel system and the tanks which as all of you will know is one of the very first things to instal so if there are additional fittings to have welded in then I need to do it now.

I've spent a lot of time on the forums and intend to do a build log, but as a starter I was wondering if anyone has come up with a way of plumbing the system to avoid a switching valve (like a Polack). I'd like to avoid that to firstly avoid the inevitable disaster when I don't notice the guage and secondly I assume it causes something of an imbalance in the car if you empty one tank at a time. Would a simple balancing pipe between the bottom of each tank work or does it need to be more complicated?

Many thanks,

Jon

 

[Jim Albright]

Fran Managed to install a crossover for my Lola with EFI.

 

[Jim Albright]

 

[Brian]

I've seen it claimed repeatedly that a balance tube is all that's required. I disagree, doubly so with EFI.

I'm planing a surge tank and 2 pumps (one in each tank) to feed the surge tank, and likely a microprocessor reading the fuel levels to jockey between or maybe both pumps.

Another option is a venturi pump to shuttle the fuel from the secondary to the primary tank. Truth is, the 10 gallons or so will only be 68 lbs of fuel. Less of an imbalance that your ass in only one side of the car.

 

[Brian]

This was recently discussed.

Fuel tank and pump setup with return style regulator.

I have been researching and don't see a good option for using a return style regulator going into 2 fuel tanks. The only electric valve I can find uses plastic barb fittings. I found a few marine and aircraft valves, but I don't really like the thought of having to turn a lever, nor the way it...

www.gt40s.com

 

[Udo]

All, I also use a surge tank (or catch tank), and started with two 5 bar pumps directly behind the two tanks. Worked well, the high pressure made the return line from the surge tank to the main tanks work. I exchanged the pumps by Facets, since more robust, but the system pressure was too small, so the return only worked into the tank close to the surge tank. An installed crossover between the two main tanks works half way, but if I drive a long time, it‘s not fully balancing the two tanks. Five bar pumps (take care that the do not run dry) are the better option. I use the Borla Eightstack EFI, by the way.

 

[Joe]

Im also running a crossover line with single pump. Fuel senders in each tank for fuel level.Clean look and simple.427w borla stack injection. Car not on road yet but when tested crossover line, tanks leveled off as they should.

 

[Jonnyt]

Many thanks for the replies guys.

All interesting comments and the comment about the cross over / balance pipe not working over distance and presumably a harsh driving environment (track for instance). That pipe is also really quite difficult to fit in the chassis that I have but not impossible.

One solution I'm thinking at the moment is to have an accurate gauge in each tank to toggle between the two when one drops by 25% say to keep the balance of the car (even though I take the point about the size of my ass!!).

Any other thoughts very welcome and I'll update this thread when I have a shooting solution!!

Best wishes,

Jon

 

[Bill Kearley]

To avoid the challenge of a cross over line big enough to do the job, I will be changing what I have to running 2 pumps, 2 filters and 2 regulators and return the fuel to the tank from witch it came. This allows the use of one sending unit and no switching of tanks.

 

[Jonnyt]

I thought about that Bill but doesn't that mean that you'll be relying on the delivery pumps being pretty spot on (which I understand they are unlikely to be) to ensure even delivery of fuel to each fuel rail?

 

[Shaun]

On my setup I had two LP fuel pumps feeding a swirl pot then HP to the fuel rail, my tanks had a bottom outlet for LP and a top for swirl pot return, I added a diverter valve linked to the chosen pump so when the Left pump is feeding the swirl pot the left tank gets the surplus fuel back and ditto for the Right, I think a cross balance pipe from memory was a tad hard to fit but can be done of course, Mick at SGT recommended my setup and thus far it seems fine, I guess the only issue is the diverter valve is another point of failure but EFi does give a bit more of a headache than a carb setup that's for sure!!

 

[Brian]

Another question, if you're running 2 regulators, are you also running 2 independent rails? If 2 regulators feed one set of rails, one regulator will invariably be set to some minuscule fraction of imbalance meaning only under full demand will they be bypassing the same volume of fuel. Another possible pitfall if you run 2 rails, one starves and the other masks it enough to damage your engine with lean mixture on one side.

 

[Brian]

Shaun brings up another point. An EFI engine can never have a short momentary loss of fuel pressure like a carb engine can easily handle. Some sort of swirl pot is essential in my opinion. Will it run without one, sure. But when you're down to the last 1/4 tank and brake or turn hard, you'll uncover they pump's intake and bad things happen.

 

[Jonnyt]

One solution to resolve the balance issue with the car that I've thought of is to have the switching of the Pollack automatically controlled so say when 25% of tank 1 has been drained, it triggers the swap over to tank 2, when that has lost 25% it switches back etc.

Agreed re: running two pumps and two rails - I think there is a high possibility of variation in fuel flows particularly in a low fuel scenario which risks pretty serious damage to the engine.

 

[Brian]

I had a simpler fuel balancing scheme in mind

2 tanks with 2 pumps, swirl pot with HP pump(s).

Main tank pump to swirl pot, and return from swirl pot to main tank
Secondary tank to swirl pot, no return.

The fuel pump in the secondary tank will run intermittently, whenever it has more fuel than the primary. What it sends to the swirl pot will overflow to the primary tank.

The up side, no valves. Down side, I'll have to pooge a controller that will read the 2 fuel senders and switch the secondary tank pump when it has less fuel than primary. Also in this controller I was planning to sum the fuel senders to a single gauge, and maybe add a momentary switch to check Main and Secondary individually.

 

[Rick]

Below is what my builder, J&L fabrication came up with. 3/4” crossover line, single fuel sender, running through the below single pump set up to feed Inglese EFI. We are we week or so away from running it.

 

[JP Verweij]

My 50cnts, swirl pot is essential and makes EFI plumbing a lot easier. Two lp pumps to the swirl pot (two tanks, two senders, two anti drain back valves) Swirl pot acts as a backup when switching tanks.
If its looks you're after and don't like the swirl pot, go carbs. Doesn't make a difference in peak horsepower only in partial throttle.

 

[Bill Kearley]

Properly balanced fuel pressure regulators will give no problems. Holley fuel mats are an asset at low fuel levels.

 

[Jim Albright]

Below is what my builder, J&L fabrication came up with. 3/4” crossover line, single fuel sender, running through the below single pump set up to feed Inglese EFI. We are we week or so away from running it.
View attachment 126744

Please let us know how it works out as I am also running Inglese 8 stack injection

 

[Brian Kissel]

I’m very interested as well. I’m currently planning a Hilborn EFI.

Regards Brian