Returning fuel to the tank
 

Hello and Happy Thanksgiving,

I am returning my fuel back to a 90 gallon tank after the pressure regulator. This is an EFI setup with approx. 55 psi fuel pressure. Does this return fuel need to go thru a pickup tube (dumping fuel at bottom of tank) or is it OK to simply dump it into the tank thru one of the bungs at the top of the tank? I have an extra pickup tube that can be used for this if needed but at the time of rigging I didn’t think it was necessary so I removed it. Now I am second guessing myself as my concern could be possible aeration of the fuel as it dumps in at the top. Probably overthinking this but wanted to get some opinions from more experienced folks.

Thanks

Gas can go back high or low, doesn't matter

Ideally you want to add the return to the pickup to not cause aeration when running low fuel level. You can get a fuel fill return adapter or return return at the filter head. I believe high pressure From the top of the tank into fuel might be the worse case scenario.

On my 28 cig I built a hose splice the had a fitting in it that I returned my fuel into the Fuel tank fill hose. I had no bungs on the tank I’ve never had an issue with my 650hp blown small blocks

Not to disagree with the Fuelab vid, but as they said, there using mineral spirits which does foam more then gas. Also note the amount of fuel being returned is quite a lot in 2 of the 3 set ups. If there is a high volume pump (something like aeromotive a1000) then maybe. The pressure going back to the tank is low once it leaves the reg.

I have MPI using a 40 psi pump and the return goes back to the return to tank fitting which is near the top and have had no issues. Even ran out of fuel one time because of fuel gauge issue, and noticed nothing until the motor started dying (was heading to fuel dock on plane)

I`ve been dumping the return next to the the intake for years .
With EFI I`m running a 2 stage Holley pump. second stage only comes in after 3# of boost.
No need to run the fuel pump at full power while at idle etc


https://cimg6.ibsrv.net/gimg/www.off...12440d2c47.jpg

Thanks guys. Appreciate the input.

‘Running an a1000 pump so I am returning a lot of fuel I suspect as this is a moderately built 502 mag.

I am heading to the boat shortly to check how I plumbed it. I just looked for my original pickups and only found 1 which means I may have actually plumbed the return through a pickup tube and have forgotten that fact. I had to make a new supply pickup so I had two left over pickups in total. I think either way I am probably OK, but I have really easy access so I will plumb the return thru the pickup and send the fuel to the bottom of tank if it’s not already done that way.

Hope fuel doesn't get to hot with the a1000

what efi are you running that requires 55# of pressure

It was dyno tuned with the same fuel delivery setup (a1000 with return) and that is where the tuner set it. It is basically the stock 502 fuel rail and injectors with #7 opened up. I also thought that was crazy high pressure as the old fuel setup was around 38 psi. I eliminated cool fuel setup, etc..

What are the drawbacks to too much fuel pressure?

Dodge,

How could this be determined? I had similar concerns by going to this big of a pump.

the trend in injection has been 55-58 psi like the returnless systems out there nowadays. With the newer style injectors they work really well with the higher base pressures.

Stock 502 MPI is around 41-43 lbs,

He's running a stock 502 MPI

As a follow up, I checked my return plumbing setup and I am returning the fuel thru a pickup.

Heat builds every time something is under pressure. Even Aeromotive has mentioned it may need a cooler depending on how much fuel is actually used. So if your not using most of the fuel running WOT it just keeps bypassing more warm fuel. Over time it "could" get to warm and start causing issues with fuel burn. What those issues would be I'm not sure and would just be guessing, no expert here. My guess would be fuel may start to burn before the spark ignites it, then there is preignition.

My motor dyno was at 530hp using Merc cool fuel module. Running higher fuel pressure would figure shorter ON times then lets say 40 psi

Note: could use a smaller pump and same reg to just push less GPH. Same pressure but less volume

I'm using an Aeromotive 1000 pump on a carbed procharger set up. I run the return fuel through a 2 x 9 inch cooler on the way back to the tank. works just fine. returns to the top of the tank and just pisses down into the tank.
Just an FYI

I used to run Aeromotive 1000's with a controller that varied voltage to the pump depending on rpm. I recently set up new motors again using 1000's but adjusted pump output again based on rpm. Kind of a PIA but I believe it is easier on the pump and keeps fuel temps down. Used with Kinsler injection and carburation. In all cases returning fuel to tank. Never have had a pump or controller fail. Good stuff!

Guess I just miss the reasoning, but why use a 1000 when a smaller pump will provide everything needed?

I believe a normal pump operates at a constant speed when it gets 12+ volts. So at idle, it may be pumping at a rate exceeding what you require at idle, creating excess pressure and subsequently heat. However, at WOT you may need that flow capacity. Some pumps provide a controller that allows you to reduce the current flow to the pump at lower rpm or loads when you don't need the fuel flow but are able to increase their flow capacity at WOT or higher load demands.

I understand that part, my questions comes from so many use the pump that in no way have the HP which needs that much flow. At best they may use 1/2 of what it can supply

Because its cool AD......:lolhit:.....and I agree, why spend 400 + for a A-1000 when a 130 dollar Holley will work in this case, maybe the OP gotta smokin deal on Aeromotive

The A-1000 leaves room to grow. If returning the fuel to the tank the pump nor the fuel is going to build any significant heat.