Returnless PWM fuel system.

Anyone here running a returnless fuel system in a boosted application??

Turns out I can pwm the pump via ecu.

Seems very simple. No regulator, no return line. The Megasquirt will use MAP to raise control pressure. I have a fuel pressure sender on the rail. 

Simples? Or am I missing something? 

Heat soak? 

Seems simple enough, I think you might need a different style pump though, probably best to grab one from a returnless stock application.

Robbie said:

Seems simple enough, I think you might need a different style pump though, probably best to grab one from a returnless stock application.

I contacted aeromotive to ask that very question but no answer as yet...

Not entirely on topic but I ran a returnless internally (fixed) regulated pump on my turbo efi Fiat and quite liked how it turned out.  It really simplified the plumbing.  

I however was only running one and later two injectors so any benefit to a rising fuel pressure was minimal.

Jumper K Balls said:

Not entirely on topic but I ran a returnless internally (fixed) regulated pump on my turbo efi Fiat and quite liked how it turned out.  It really simplified the plumbing.  

 

I however was only running one and later two injectors so any benefit to a rising fuel pressure was minimal.

On topic enough- it's a heck a lot easier to do that, and calibrate that system than try to calibrate the fuel pump controller to add one more layer of control.  Constant 65psi at the rail is pretty easy to deal with.  It's how OEM's have been doing it for a long time.

The RAV4 had a returnless system.  I forget the spec, but I think it was about 55 PSI.  There was a regulator in the circuit.  It was in the tank, with the "return" line being maybe an inch or so long.  I took out the regulator and replaced the pump with a big high flow Walbro and plumbed in the return line from the regulator on the new motor.

While the idea of doing software PWM control of the fuel pump to set the fuel pressure is somewhat appealing at an intellectual level, I don't think I'd got there.  For one, tuning PID systems is enough of a PITA when it comes to relatively non-engine-destroying things like boost level (you can always get out of the throttle) or idle control.  Doing it for fuel pressure?  *shudder*.  For another, you need a solid state relay on the pump, and from what I've heard from people who've tried it, it's both noisy and hard on the pump. 

Most factory "returnless" systems use a normal style of regulator, and have a small loop that includes the filter.  They just don't send the fuel all the way up to the engine bay and then back, in order to avoid heating it up.

Ford did electronic control of the fuel pump for the longest time.  No return line, no regulator.

I noted with interest that the newer Econolines are returnless, and have a fuel pump control module, but it is non feedback.  There IS no fuel pressure sensor.  So there has to be a regulator in the pump and the control module is just running open loop to run the pump a bit more than necessary but not full bore.

That was fun trying to fit a pressure tester on.  Driving a van with no doghouse when it's way below freezing sucks.  I really missed being able to check out fuel pressure by looking at a scantool.

I just installed a returnless system in my Fiesta out of a Focus SVT. It uses a fuel pump driver module that’s controlled by the pcm, the Focus’ intank pump, inertia switch, and a fuel rail pressure sensor. It was super easy to plumb, only  one line from the tank to the engine with a filter inline. I don’t see why you couldn’t use a similar setup if you could control the fpdm with your pcm.

Can I ask without derailing this thread?  Would this work while converting my 75 Stingray from carbed SBC to LT1 to avoid having to run a second line to the front of the car? 

In reply to vwcorvette :

Certainly as long as there is enough pressure and volume.

In reply to Saron81 :

Yeah the ms3 pro has this all covered as far as control goes. If the pump can be PWM all I need is a solid state relay. 

Could get complicated if the systems run parallel in open loop. Regulator sets pressure mechanically at lower duty cycle and it can be fine tuned via pump. 

In reply to vwcorvette :

This is kinda what I'm doing too. Carb to efi. 

In reply to codrus :

If it was gonna be a task I'd rather not do it but it seems rather straight forward. Close loop with a fuel pressure sensor.