FPR for NA or FI

Originally Posted by Stazi 11/16/05 10:06 AM

On my returnless setup, there is probably less chance of heaving one cylinder leaner than another due to a dead head setup in the fuel rail, but for return-style rails, I bet money that the last injector before the pressure reg is a smidge leaner than the first injector on the rail - this is because unless the FPR clamps shut under boost (thus creating a dead head) the allowed fuel flow out of the rail will cause the pressure at the last injector to be lower than the first - there' no way around that - otherwise you defy fluid dynamics and physics. I.e. you have to have a low and high pressure variation to cause the fuel to flow into the rail and out again.

Originally Posted by warmonger 11/16/05 07:10 PM

Stazi, well that makes sense when you explain it like that. But in my case the FPR diaphragm recieves positive boost pressure so it should be clamping it shut.

That also reminds me that injector pressure would be reduced by the boost pressure present in the intake.

I wonder if it balances out. The FPR keeps fuel pressure a rock steady 55psi without boost under WOT. If it adds 10psi boost to both the diaphragm and the intake system, does it balance out and still inject at 55psi?