951Porschiste

The new LR fuel rail that I installed came with a Fuelab adjustable fuel pressure regulator. I am also using a VDO 60 psi pressure gauge screwed into the FPR. The instructions that came with the FPR were to adjust the fuel pressure by running just the fuel pump and without the vacuum line in. I have Promax/Scivision MAF chips and their recommendation is to run a 3bar FPR. So, I adjusted the fuel pressure to 43. 5 psi which is the equivalent of 3 bar. When I turn on the engine and let it idle the needle reads a nice 43.5 psi. However, when I open up the throttle the pressure reading goes up to almost 50 psi.
Question:
Does a 3 bar FPR mean that the maximum fuel pressure will be 3 bar or does it only refer to the minimum fuel pressure?

OriginalSterm

3 bar is the differential across the orifice of the injector

951Porschiste

So that is a measure of the pressure drop as fuel is sprayed out of the injector and into the combustion chamber?

Does that mean that I should adjust the fuel pressure such that on part open throttle the pressure gauge should read 43.5 psi (3 bar)?

OriginalSterm

set 3 bar with the vacuum line disconnected, this is static pressure. with the vacuum line connected, you should read something less than 3 bar at idle (whatever your idle vacuum is). with the vacuum line connected, you should also read your current boost level plus 3 bar (if boost is 15 psi, you should read 3 bar + 15 psi).

this maintains the pressure drop across the seat of the injector at all times.

KuHL 951

Most AFPR and OE Bosch are rising rate FPR's that will increase pressure to compensate for the FP drop under load, That's how they are supposed to work. Yours seems to be doing fine.

951Porschiste

Thanks a million guys. That is basically what I did. I initially did set it at 43.5 psi without the vaccum line. There actually is a small pressure drop once the vacuum is on. Then it goes up as the throttle opens and boost increases.