BlackGMC

iTrader: (31)

So i have a question. I have a Fuelab adjustable FPR. It rises pound for pound with boost like it should. My question is should it decrease pound for pound with vacuum?

For example. I have a base pressure of 58psi. When i let off the throttle and coast while decelerating my boost gauge goes to -15 psi (vacuum) should my fuel pressure drop to 43 psi? Another example if it is -20psi should the fuel pressure drop to 38psi?

smokeshow

iTrader: (16)

Yep. That's why you put static flow rate in the IFR table and you're good to go

BlackGMC

iTrader: (31)

Ok so if it does not decrease like that in vacuum it means i have:

1. Vacuum leak
2. Broken FPR
3. Clogged return


My setup is a walbro 255, -8 feed and -6 return.

smokeshow

iTrader: (16)

Referenced to the intake manifold, not before the throttle right?

BlackGMC

iTrader: (31)

Yep referenced to the manifold after the TB. My pressure does not drop that much.

For example. Intake vacuum is -15psi the fuel pressure is like 48-50.

oakley6575

iTrader: (5)

How did you set fuel pressure? It should be set with the pump running and engine off.

I don't see mine drop pound for pound when in vacuum for some reason like you stated. It is close but anything after -10 or so, it doesn't move pound for pound like it should.

BlackGMC

iTrader: (31)

Everything i have read is you set the fpr with engine running and vacuum line removed. That is how i set mine.

oakley6575

iTrader: (5)

That doesn't make any sense to me if you are trying to set static fuel pressure. It's not static if vacuum is sucking on the injector.

BlackGMC

iTrader: (31)

straight from Aeromotive instructions...

http://aeromotiveinc.com/wp-content/...0109-0revG.pdf



Here is a video i found.
https://www.youtube.com/watch?v=c12jPdR2rJg

oakley6575

iTrader: (5)

that vid was pretty funny. Yea that doesn't make sense in my head but I guess Aeromotive knows what they are doing

I talked to Dave Steck a long while ago about this. He sees it the same way as me. Everything should be static in order to set the static pressure. He wrote an article for Injector Dynamics about it among other things, and I think its on their web page still. But I at least if the vacuum line is unplugged doing it your way, you shouldn't really see much difference between the two.