Less fuel pressure = Better performance

[undefined0000]

Can someone explain this to me? I had mine turned up to 51psi because of major leaks I had and never bothered to change it back. Now I turned it back down and it feels as though its performing better. ALSO. Should there be a check valve on the line going to the A FPR, or does it need the boost going into it?

 

[LandSpeed-DSM]

Assuming there are not other issues at play.. You were probably running pig rich.

The FPR needs a dedicated source from the plenum.

 

[undefined0000]

I've got some smaller boost leaks, but ok. So no check valve is needed? I just have a hose right off of the plenum going to it.

 

[Colt4G63 also]

No never put a check valve between the AFPR and the plenum. The AFPR needs to see manifold pressure, high and low.

 

[undefined0000]

No never put a check valve between the AFPR and the plenum. The AFPR needs to see manifold pressure, high and low.

Ok, thanks for the clarification. Just trying to get my vacuum situation worked out. With bypassing the stock solenoid, I wasn't sure.

 

[EMX5636]

The stock solenoid blocks vacuum under start up and some other conditions to increase fuel pressure and add fuel until the engine warms up.

 

[undefined0000]

The stock solenoid blocks vacuum under start up and some other conditions to increase fuel pressure and add fuel until the engine warms up.

Makes sense. I did notice that after turning it down, it studders a bit right after starting up and takes about 7 cranks to start or so

 

[JusMX141]

Can someone explain this to me? I had mine turned up to 51psi because of major leaks I had and never bothered to change it back. Now I turned it back down and it feels as though its performing better.

Stock injectors are flow-rated at stock fuel pressures. Take an injector that flows 450cc @ 37psi and crank it up to 51psi, suddenly you have a 550cc injector. The ECU cannot take this additional fuel into consideration because it assumes you're running stock fuel pressures all the time.

ALSO. Should there be a check valve on the line going to the A FPR, or does it need the boost going into it?

You need a pressure/vacuum source from the intake manifold going to the pressure regulator. The regulator is designed to lower pressure at idle speed when the engine on vacuum, then raise pressure at a 1:1 ratio with every pound of boost you're running. In other words, if the pressure regulator doesn't have a signal line going to it and it runs a constant 37psi, you'll blow shit up from being too lean as soon as you hit boost.

 

[undefined0000]

Stock injectors are flow-rated at stock fuel pressures. Take an injector that flows 450cc @ 37psi and crank it up to 51psi, suddenly you have a 550cc injector. The ECU cannot take this additional fuel into consideration because it assumes you're running stock fuel pressures all the time.

You need a pressure/vacuum source from the intake manifold going to the pressure regulator. The regulator is designed to lower pressure at idle speed when the engine on vacuum, then raise pressure at a 1:1 ratio with every pound of boost you're running. In other words, if the pressure regulator doesn't have a signal line going to it and it runs a constant 37psi, you'll blow shit up from being too lean as soon as you hit boost.

Thanks for that. I cranked it up when I initially got the car because I bought it with the worst intake manifold job ever. I figured that would help the afrs until I could replace it and never turned it back.

Thanks for explaining how the dynamics of the regulator worked. it was like magic for me.