EFI regulator plumbing

[EFI69Cam]

In a normal EFI fuel system fuel is pumped through the rails then into the regulator. It seems to me that the fuel pressure could be regulated then sent to the rails, and if the regulator was mounted in the engine compartment vacuum reference could be maintained.

I want to not circulate fuel over the hot engine.

Are there any reasons not to plumb this way?

[DeltaT]

The problem then is that the pressure is not regulated at the point of variable demand. You would simulate a 'deadhead' regulator setup with all the expensive plumbing of a correct setup. With your setup WOT injector pressures at the injectors farthest away could vary a lot from the "regulated" side of the regulator.

How would you connect the rails? To the bypass or as 2 deadhead stubs off the regulator or 1 balanced (loop) stub?

I am dealing with the heated fuel issue right now. It's not killing me but even after adding a pump controller (.5 pump speed <1850rpm) and using a B&M cooler as a return-line fuel cooler the pump is quite warm at the end of a 1-hour drive in 68 degree weather. I did route the return, with some insulation on it, right over the tranny, and I'm thinking of rerouting it down the other side frame rail. Also I plan to do some more insulation on the fuel lines around the motor. I wonder if anodizing the fuel rails black made things worse...

Jim

[camcojb]

you can bypass the fuel before the rails without issue. Been doing it for years. My new systems bypass at the tank, but even if you want to be closer to the engine it works fine.

I do this to prevent heating the fuel returning to the tank.

Jody

[DeltaT]

You've had no problems with a deadhead setup? Haven't you been doing some boost, too?

Jim

[EFI69Cam]

you can bypass the fuel before the rails without issue. Been doing it for years. My new systems bypass at the tank, but even if you want to be closer to the engine it works fine.

I do this to prevent heating the fuel returning to the tank.

Jody

I had thought about that. My concern is loosing the vacuum reference for the regulator. Is this a concern with the Accel gen 7? Part of the global config is to tell it if its a "returnless" system or not.

[camcojb]

I had thought about that. My concern is loosing the vacuum reference for the regulator. Is this a concern with the Accel gen 7? Part of the global config is to tell it if its a "returnless" system or not.

You can still run a line to the regulator if you want; I never did and had no issues. I ran that setup on my Procharged 540 at 16 psi, ran fine.

https://static1.pt-content.com/images/pt/2006/09/zl1motor3-1.jpg

[John McIntire]

Jody, I am still debating on plumbing my fuel system like this. I can see everyones concerns and appreciate everyones tried and true experiences from the Power Tour.
Now with you running a boosted application, with no reference, I'm really confused! Did you just crank the pressure up to 59/60 pounds so that when you ran full boost, the fuel was there? I'm just running N/A and would I just set my pressure to 43PSI?
Now what about air in the line? I'm worried about priming the system upon initial start up. Where does the air go? will it just be "injected", or is there really no need to worry about that?
I plan on also running Aeromotives Pump Speed Controller to cut down on the heat also. Will this complicate things? I dont think I really understand how that device works. I don't understand how it can still supply the correct PSI while regulating the voltage.
Just a few questions! Thanks for any input and the help you provided so far!

[EFI69Cam]

You can still run a line to the regulator if you want; I never did and had no issues. I ran that setup on my Procharged 540 at 16 psi, ran fine.

https://static1.pt-content.com/images/pt/2006/09/zl1motor3-1.jpg

Do you trust the ECM to compute the pressure/flow relationship properly? I'd think there are scads of variables (the LS1 has the IFR table for this) that would make computing it on the fly with unknown injectors tricky.

Also the only returnless factory system I've seen is the one on the LS1, that one has a dampener. Do I need one?

Thanks for your advice. I think I will mount the regulator by the tank and run one line up to the engine.

[Fuelie Fan]

Haha didn't we just have this conv a few weeks ago? Do a search, there's a long thread on this subject

[EFI69Cam]

Haha didn't we just have this conv a few weeks ago? Do a search, there's a long thread on this subject

Yes there was, sort of. I read that thread and it raised more questions for me than it answered.

[DeltaT]

Jody,

Have you ever logged rail fuel pressure using your technique? I'd be curious how much the pressure actually dropped at WOT. I suspect you're tuning around some amount of pressure drop.

Jim

[parsonsj]

I read that thread and it raised more questions for me than it answered.
I can see why. It seems there are several ways to accomplish the goal of keeping adequate fuel pressure to the injectors, and some of us are optimizing one thing (more consistent fuel pressure) over another (adding unnecessary heat to the fuel and fuel tank). Others are optimizing on keeping the fuel as cool as possible, since eventually heat in the fuel will affect the car.

My take is that neither is perfect; you just need to see if one method works for you. Jody has as much experience as anybody with long trips on highly modified cars, so his recommendations merit consideration especially if you plan on taking your vehicle on long trips.

Others have lots of experience with drag racing or EFI tuning (not me for either), so their experience merits consideration as well.

As for me, I'm running the classic drag racing setup with the pump feeding (at full speed) both fuel rails then having the regulater return excess fuel to the tank. I've driven my car up to an hour at a time, with no ill effects, though there is some marginal heat added to the return line (as felt by touch). Without instrumentation, and detailed scientific experiments, I don't know if I'm going to have a problem or not. More to come once I get more seat time.

And that's the end: there is no easy, one size fits all perfect answer for everybody.

jp

[camcojb]

Jody,

Have you ever logged rail fuel pressure using your technique? I'd be curious how much the pressure actually dropped at WOT. I suspect you're tuning around some amount of pressure drop.

Jim

A fuel pressure gauge is in most of my cars. With the regulator out back I don't remember seeing any drop, as that would be an issue.

Jody