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How much pressure in FuelRail while idling? Adj FPR

MadDog_945

MadDog_945

Våga Vägra 8V
Joined
Apr 25, 2006
Location
Lower Saxony
Yesterday i was told something i heard the first time.. from a guy who certainly knows what hes talking about...


So.. i bought this knockoff aeromotive FPR.. how to setup pressure?

My thinking was: i have a factory 3bar one.. so start engine and put it to 3bar minus intakepressure (about -0.55barVAC) so it should be 2,54bar in idle... but i was told its wrong..


It should have 3 bar in idle...?? A little world broke together for me when i was told this?
 
that's probably about right. with the vacuum line hooked up, it drops fuel pressure at idle. with no vacuum line hooked up, it should sit right around 3bar (or ~ 44psi +-).
 
3 bar with vacuum hose to fuel pressure regulator disconnected and plugged. This is what I read it should be.
 
So its running engine -> unplug hose -> set to 3bar -> done ?


thats what i did.. but thats wrong... in a way? meh.. im confused now...
 
MadDog_945 said:
So its running engine -> unplug hose -> set to 3bar -> done ?


thats what i did.. but thats wrong... in a way? meh.. im confused now...
Click to expand...

no thats not wrong. The pressure regulator compensates for vac/boost. in the case of a LH 2.4 Volvo the fuel pressure difference over an injector is 3 bar in stock form. with 1 bar boost the fuel rail will be at 4 bar. at heavy engine braking and close to .8 bar vacuum the fuel pressure will be 2.2 bar. That is, when set at 3 bar with the vacuum hose connected.
 
Get the engine to a warm idle; unplug the vacuum line from the regulator and cover the end with your thumb or a piece of tape; set your fuel pressure to 3.0 bar (gauge) +/- 0.2 bar; then hook the vacuum line back up and it should drop down into the 2.5 bar range (a bit higher if you have an aftermarket cam that reduces vacuum at idle). That's what everyone and the greenbook is saying -- except for triebwerk.
 
M.H. Yount said:
Get the engine to a warm idle; unplug the vacuum line from the regulator and cover the end with your thumb or a piece of tape; set your fuel pressure to 3.0 bar (gauge) +/- 0.2 bar; then hook the vacuum line back up and it should drop down into the 2.5 bar range (a bit higher if you have an aftermarket cam that reduces vacuum at idle). That's what everyone and the greenbook is saying -- except for triebwerk.
Click to expand...

This is what I was going to suggest^
 
why your all tripping hard. The engine does not need to be running plugged or warmed up to set fuel pressure.

All you need is to have the fuel pump running. then set it and leave it alone.
 
burstcurse said:
why your all tripping hard. The engine does not need to be running plugged or warmed up to set fuel pressure.

All you need is to have the fuel pump running. then set it and leave it alone.
Click to expand...

The fuel pressure needs to be checked both with the vacuum hose connected to and disconnected from the fuel pressure regulator.
 
You need to check it with vacuum on once you've set it guys; so you might as well set it under the conditions it will see when it's running. And while it may not generate a big difference, the regulator is going to behave a bit differently at 200F than it will at 80F.

You don't have to have the engine running to set base timing either -- but if you've got a timing light, you're better off using it to set the timing with the car running. Same deal with fuel pressure. You don't have to have it running -- but it's a better standard procedure.
 
my experience is this, i bought a bosch adjustable fpr designed to run on the Buick Grand National, i had to turn the pressure way down, it sits at maybe 1.5 bar at idle, just about 20 psi, i'm running 36lb pontiac GTP V6 injectors and tlao chips, car comes up on boost fine and fuel pressure increases accordingly and the car speeds along at 11:1 a/f, the computer will compensate the pulse of the injectors to attain the correct a/f ratio, i'm makin 205hp 237lb/tq so no worries if you're running lh 2.4
 
Pump(s) probably make a bit more pressure at ~14V then they do at ~12V I would think, so probably *most accurate* to set everything with the car running, no?
 
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