Still running rough, checked fuel pressure by coolant resevoir, showing over 100psi on key on position, and also in running mode..).. is this way too much? Not sure if anyone has any insite on what it should be..

 

Isn't the correct fuel pressure for a Turbo around 38psi?

100psi sounds way high unless you have some aftermarket mods with a matching DME or tune that expects/requires 100psi fuel pressure.

If the 100psi fuel pressure not intended then there is a fuel pressure regulator problem would be my guess, for obvious reasons.

Check that: not 38psi but 3.8 bar or 55psi is what my research tells me the 996 Turbo stock fuel pressure should be.

 

I have checked it on the dyno run when we were data logging and it should be right around 70 psi ..

 

You could have a plugged injector or an obstruction somewhere. I would say needs a full diagnostic to see. You don't want to start chasing a ghost.

Good luck

 

The reg should be able to handle that. but I agree with chasing ghosts.

 

A failed fuel pressure regulator will do that...

 

Pressure should be about 55lbs with the factory FPR.

A plugged injector would have nothing to do with over pressure issues as the injectors are only energized by the internal rail pressure they do not control / regulate pressure.


Likely culprit is the FPR. Pull your return line at your tank and see what comes out of that with the key on and engine running. NOTE if it is returning OK you will get a decent stream through that line. You will want to dicharge it into a fuel can or some other container so you do not get gas everywhere. No return or vary little means you likely have a bad FPR or an obstruction somewhere in the system. Huge return could me there is something going on with the pump, that is unlikely though seeing how when these pumps fail they gennerally under pressure not over pressure.

Is your fuel system stock???? Intank pump, FPR and return line?

Pressures of 100 PSI or more can blow the injectors out of the clips that locate them on the rails. It drivesthem down onto the injector ports on the engine. You might want to eyeball all the injectors to see that they are still located properly.

 

When my car was on Kelly Moss's dyno and it was data logged and Tony ,EPL, saw my injector duty at a high rate,,We then checked pressure off of the fuel filter and it was 70 psi at WOT until around 5500 then dropped to low 60's..So,then Tony said to add another pump to keep it up to 70psi to have the injector rate in a safe place and when I did it it was safe.
But my car is modified and uses 72 injectors with stock FPR .

 

the thing is the fuel pressure regulator has a vaccum port that raises or lower the fuel pressure depending on how the system is made but from your results, this mean that when the intake piping raises to 15 psi (1 BAR) the fuel pressure also raises by 1 bar. What this does is make sure that the injectors always push out the same pressure. If you have 1 bar of pressure in the manifold, the fuel pressure is raised by 1 bar so you always have 55 PSI of fuel going to the manifold. I don't know how the Porsche engine is made but usually, it also takes vacuum when low speed or idle is achieved, which means the engine is pulling on the fuel so you get in fact more fuel pressure going to the manifold. With the vaccum port attached, it lowers the fuel pressure so you still get the 55 PSI. It all depends on if the vacuum is taken before or after the throttle body. I suppose 55 PSI is with the engine off, not with the engine running?

So basically, it was correct for you to get 70 PSI under 1 bar of boost and it shoudl not drop. What this means is the the fuel system isn't big enough, either the feed lines or the fuel pump, which was probably your case.

In case of a too high pressure, i would vote for the fuel pressure regulator too. May have something in it or it might have failed if it is one of those crushed type 5 bar fpr.