Help designing EFi fuel system

[Randy Folsom]

Randy

Do you have good in tank baffles / trapdoors and possibly foam to stop fuel sloshing?
I did not and from around half tank down under braking for a corner / intersection etc I could hear the Facit red top hammering as it sucked air. This was normal road driving, on track from perhaps 3/4 tank it would suck air under really heavy braking

Facit could handle the running dry

High pressure pumps do mot handle being dry and the vanes are damaged in a couple of seconds when running dry and the pressure supply drops off.

Ian

I welded in baffles about 5” in front of the back of the tank. I cut out the rear tank recess plates to fit the baffles. I replaced the tops of the recesses with 1/4” plate. The thicker plate allows me to screw the pump hangers and fuel level senders directly to the tanks. The pieces laying on top of the tank are the baffle, 1/4” cover plate, rear mounting block, and front mounting tab. C7 Corvettes use a simple bucket attached to the bottom of the hanger. That won’t work well because the tanks on the RCR40 don’t have flat bottoms.

 

[Brian]

I'm going to be the turd in the punchbowl.

Use Rob's schematic, but return all fuel to tank A, ditch the valve.

Use an electronic solution to power the B tank's low pressure pump when tank B has more fuel than A, tank A low pressure fuel other wise.

 

[Randy Folsom]

I'm going to be the turd in the punchbowl.

Use Rob's schematic, but return all fuel to tank A, ditch the valve.

Use an electronic solution to power the B tank's low pressure pump when tank B has more fuel than A, tank A low pressure fuel other wise.

There are advantages keeping the systems separate such as using one tank for race gas and the other for pump gas, back up fuel system, reserve tank, or simply leaving one tank empty.

My personal preference is to use a valve to direct the return. The valve is wired such that activation of a pump also sets the valve direction.

Amazon.com

 

[joe]

Is there a reason that the system has to be so complicated (lots of parts)? I'm planning on running an Aeromotive in-tank pump in the driver's tank in a return-style fashion to my Borla 8-stack with a flexible fuel line linking the passenger tank to the driver's. I;m not even sure I'll run 2 fuel level sending units.

 

[Randy Folsom]

Lots of good reasons for keeping the tanks separate (see earlier comments), but if none apply to you then connecting the tanks can certainly make for a simpler fuel system.

The challenges are avoiding up hill runs and not exposing the tubing to road hazards. The connection should use, or at least incorporate, some flexible hose to avoid stress on the joints.

The best routing I seen that relies on gravity is to run the connection tube from the backs of the tanks, through the beer coolers, then all the way back to the cross member under the transaxle. This routing meets the above criteria and the tank bungs don’t interfere with tank insertion/removal. It’s a bit long, but gasoline really doesn’t care about how long the tube is as long is it is big enough. It may require using a small battery such as a Lithium Antigravity or raising the battery, or relocating the battery to the front.

Another option is a direct shot along the bottom of the firewall/bulkhead but then the coolant tubes, brake lines, AC hoses, etc. need to be raised up and there may not be enough room to do that.

 

[Paul Proefrock]

I bored thru the walls of the sponsons so I can connect the two tanks with a 16AN line. The line itself, runs at the front of the engine opening and I can squeeze it below the tubes running thru the spline. I put a Stainless Steel sheet metal guard under and behind it to protect it. A 16AN line will equalize the fuel level in less than two seconds. Solves all kinds of issues for an EFI system.

 

[Randy Folsom]

I bored thru the walls of the sponsons so I can connect the two tanks with a 16AN line. The line itself, runs at the front of the engine opening and I can squeeze it below the tubes running thru the spline. I put a Stainless Steel sheet metal guard under and behind it to protect it. A 16AN line will equalize the fuel level in less than two seconds. Solves all kinds of issues for an EFI system.

I might just go ahead and do the same. Especially if I can use a 12v AC compressor mounted in the frunk. That would provide plenty of room to raise the coolant tubes, brake lines, etc. Since, I already purchased all the pieces for both sides, I’ll just have a backup fuel pump, but I will be able to eliminate the switched return system.

 

[Paul Proefrock]

I plan to run the Aeromotive Phantom 340 system on the driver's side. It has performed flawlessly for me in my last two cobras. Still undecided whether to put the level sensor on the passenger side or the driver side. The Phantom system has a surge tank but I have added baffles to the tanks also. Tanks are divided into three sections to counter any surging when cornering or braking.

 

[Paul Proefrock]

Randy, in one of our texting threads, there are pictures of mine and Steve's (Kiwi) sponson drilling. We chose to go across the front of the opening, under the spline opening. This is a picture from my drilling procedure.

A 16AN line will tuck under the spine opening quite nicely. The holes are not easy to bore but can be done. I have more pictures on my website, 65shlb.com.

Don Pirre chose to come out the back of the tank and run a line back and around the front of the horseshoe. Steve has some concerns about it being able to transfer fuel and not airlock, but I must defer to him, he's the plumber who knows this stuff.

 

[Neil]

Randy, in one of our texting threads, there are pictures of mine and Steve's (Kiwi) sponson drilling. We chose to go across the front of the opening, under the spline opening. This is a picture from my drilling procedure.
View attachment 149819
A 16AN line will tuck under the spine opening quite nicely. The holes are not easy to bore but can be done. I have more pictures on my website, 65shlb.com.

Don Pirre chose to come out the back of the tank and run a line back and around the front of the horseshoe. Steve has some concerns about it being able to transfer fuel and not airlock, but I must defer to him, he's the plumber who knows this stuff.

Nice weld beads.

 

[Randy Folsom]

Randy, in one of our texting threads, there are pictures of mine and Steve's (Kiwi) sponson drilling. We chose to go across the front of the opening, under the spline opening. This is a picture from my drilling procedure.
View attachment 149819
A 16AN line will tuck under the spine opening quite nicely. The holes are not easy to bore but can be done. I have more pictures on my website, 65shlb.com.

Don Pirre chose to come out the back of the tank and run a line back and around the front of the horseshoe. Steve has some concerns about it being able to transfer fuel and not airlock, but I must defer to him, he's the plumber who knows this stuff.

Paul, Thx much for the guidance. Fortunately, I haven’t made so much progress. Still plenty of opportunity to make changes. Cheers, Randy

 

[Jean-Marc]

I bored thru the walls of the sponsons so I can connect the two tanks with a 16AN line. The line itself, runs at the front of the engine opening and I can squeeze it below the tubes running thru the spline. I put a Stainless Steel sheet metal guard under and behind it to protect it. A 16AN line will equalize the fuel level in less than two seconds. Solves all kinds of issues for an EFI system.

Paul, for ra simple road use, it is the best solution, but for the few that will use their car on a race track, keep the 2 tanks separated is very important because it change a lot the balance oft he car depending of the weigt of gas per tank and its allows you to compensate the weight of the driver. But I agree it is very far away of most of our concern.

 

[Walter]

I agree with Jean-Mark, however, why not do it the right way even for public road use? In case one scavenge pump fails you have a back-up. I mainly use the driver's side tank and use the other for a reserve ...

 

[Brian]

One huge difference between carb world and EFI world.

A carb (or 4 Webers) has half a pint of gas in the carb if there's a short interruption in fuel pressure. With EFI, the second the pump intake gulps a bubble of air, you lose fuel pressure and delivery and the engine falls on it's face. And if you pull off on the shoulder or stop at a redlight facing downhill and all of the fuel runs to the far tank, you're dead in the water until you can push the car back into a nose up position.

Supposedly the mats help, but they can only do so much when high and dry. At a bare minimum with EFI, I would have 2 pumps, one in each tank with Y and check valves so you can get fuel pressure unless you're committed to never going below 1/4 tank.

 

[Randy Folsom]

One huge difference between carb world and EFI world.

A carb (or 4 Webers) has half a pint of gas in the carb if there's a short interruption in fuel pressure. With EFI, the second the pump intake gulps a bubble of air, you lose fuel pressure and delivery and the engine falls on it's face. And if you pull off on the shoulder or stop at a redlight facing downhill and all of the fuel runs to the far tank, you're dead in the water until you can push the car back into a nose up position.

Supposedly the mats help, but they can only do so much when high and dry. At a bare minimum with EFI, I would have 2 pumps, one in each tank with Y and check valves so you can get fuel pressure unless you're committed to never going below 1/4 tank.

Regarding downhill situations, baffles will only help for a few seconds. I am guessing a decent sized swirl pot could help. I wasn’t going to put one in, but definitely rethinking that.

 

[Paul Proefrock]

One huge difference between carb world and EFI world.

A carb (or 4 Webers) has half a pint of gas in the carb if there's a short interruption in fuel pressure. With EFI, the second the pump intake gulps a bubble of air, you lose fuel pressure and delivery and the engine falls on it's face. And if you pull off on the shoulder or stop at a redlight facing downhill and all of the fuel runs to the far tank, you're dead in the water until you can push the car back into a nose up position.

Supposedly the mats help, but they can only do so much when high and dry. At a bare minimum with EFI, I would have 2 pumps, one in each tank with Y and check valves so you can get fuel pressure unless you're committed to never going below 1/4 tank.

Brian, between the baffles I am adding and the reservoir system that comes with an Aeromotive Stealth system, these points become a non-issue.

 

[Jerry Irwin]

Regarding downhill situations, baffles will only help for a few seconds. I am guessing a decent sized swirl pot could help. I wasn’t going to put one in, but definitely rethinking that.

With ANY efi always use a swirl pot.........
HP Vane pumps fail very quickly if starved of fuel...
Jerry

 

[Brian]

With less than a 1/4 tank of gas, stopped at a red light facing downhill, how long will that little bit of foam keep the pump intake covered when it's high and dry?

OEM's all have about 40oz container the pump sits in, and a bleed that feeds a venturi pump that keeps that vessel with the pump in it full to the brim.

Couldn't find a good image, but there's a rubber flapper to let fuel in when the pump is off and you fill the tank, but the main supply is a venturi pump fed by bypass regulator's bleed.

And the GT40's tank geometry really works against us on this being so shallow and long. Works for us under power, but braking and downhill, not so much.

So yea, all OEMs have a swirl pot you didn't know about.

 

[Randy Folsom]

With less than a 1/4 tank of gas, stopped at a red light facing downhill, how long will that little bit of foam keep the pump intake covered when it's high and dry?

OEM's all have about 40oz container the pump sits in, and a bleed that feeds a venturi pump that keeps that vessel with the pump in it full to the brim.

View attachment 149852

Couldn't find a good image, but there's a rubber flapper to let fuel in when the pump is off and you fill the tank, but the main supply is a venturi pump fed by bypass regulator's bleed.

And the GT40's tank geometry really works against us on this being so shallow and long. Works for us under power, but braking and downhill, not so much.

So yea, all OEMs have a swirl pot you didn't know about.

My in-tank pumps came with buckets, but the buckets don’t sit on the floor of the tanks, so I placed baffles just a few inches in front of the pumps. My calibrated eyeball says the fuel capacity is about the same. I do have concerns that I made the drain holes a bit too large. I need to test to see how fast they drain compared to the buckets that came with.

 

[Ian Anderson]

I am surprised that nobody is mentioning hydramat.

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