I have seen the FP changing 
from 35 psi at low RPM to 50 psi at high boost?

 

Hi Buly,

 

What you describe here is exactly how it's supposed to work, and whether you believe it or not, it's making your tuning life easier.  Here's why...

 

Think about how a fuel injector works.  The fuel rail has a high pressure in it, and the intake end of the injector is in a lower pressure area.  To actuate the injector, all you're doing is opening it.  The rate of fuel flow is controlled by the difference between the pressure in the fuel rail, and the pressure in your intake.  

 

As you can see, if you were to set your fuel pressure at a fixed point, then run lots of boost, there would be very little flow across the injector, because the differential pressure would be low.  This will make your injector appear to get smaller as boost increases, and eventually you will go lean.  Recall also that lean + boost = rebuild :-(

 

The whole idea of the rising rate fuel pressure regulator is to keep the differential pressure close to the same, so the injector flows the same rate of fuel regardless of the MAP.  This makes it easier for the engine computer to control idle to max boost mixtures.

 

Cheers,

Rusty (Stopped to eat in Greenville AL in George's honor today <g>)