Resolved 1G fuel pressure?

[TC Mueller]

Whats a decent ammount of fuel pressure for an aftermarket fpr? right now my fuel pump is a 255 with soon to be 550 injectors. HELP!

 

[DGajre777]

You need to set your AFPR to base FPR. On a 1G, I believe it is 37psi on a 1G Turbo and 43psi on a 2G Turbo. A good FPR should raise fuel pressure on a 1:1 ratio to boost. So at 20 psi, your fuel pressure gauge should read 57psi.

 

[TC Mueller]

I dont understand what your saying with this ratio.

 

[GSX26]

First off, he's saying set it to factory base fuel pressure. 37 psi in your case. Then, your afpr should be a 1:1 ratio with your boost pressure. So if you are at 0 psi, the fuel pressure should be at 37 psi. 5 pounds of boost, and the fuel pressure should be at 42. For every one pound of boost increase, there should be one pound of fuel pressure increase.

EDIT: Also, don't forget that the 37 psi is at idle with vaccum hose off. It will be lower than that when you have everything hooked up because of vaccum.

 

[TC Mueller]

Ohh ok. Thanks for explaining it in retard words.

 

[steve]

We always talk about base fuel pressures when we discuss setting the regulator. That's the fuel pressure before corrections for manifold pressure. The ECU is programmed with the assumption that the fuel injectors spray the same amount of fuel per unit time no matter what is going on in the intake manifold. The FPR takes case of this by changing the actual fuel pressure = Base Pressure + Manifold Pressure. Since off boost the manifold is usually under vacuum (Negative pressure) the actual fuel pressure goes down while under boost the pressure goes up to maintain the same difference in pressure between the fuel rain and the pintle end of the injector. If we didn't do this the injectors would have the fuel sucked out of them under vacuum when they opened and dribble out under boost. If the manifold presure was high enough and equaled the fuel pressure the injector could fire and no fuel would come out

As long as your prepared to tune for it you can run different base fuel pressures than stock but it's easiest to leave it alone and just correct for the difference in size between and deadtime of the two injectors.

Steve