hey about what fuel pressure do i need to be at? what are you heads n cam guys running with the vaccum off and on. i dont know if im having a fueling problem or what. my mods are in the sig.

 

What pressure did you tell madz28 you would be running? If that's what he tuned it for, that's where you need to set the "no vacuum" pressure. Typically its 43.5psi. But use whatever pressure you told him you were going to use, because that's the pressure he used to set the injector constants.

 

actualy i dont think i told him anything about fuel pressure. i didnt know you did that with tuning

 

Well, you have to consider FP when tuning. The "injector constant" Fred refers to is the flow rate of the injector, which will, of course, vary with the FP. The 4th gen PCM has no way to directly sense FP. It is accounted for by the injector constant. The stock FP is vacuum referenced, so that the fuel pressure always maintains the same difference between the manifold pressure and the line pressure and hence the flow rate is constant.

In general, you should leave the FP alone. FWIW, when I had my prior setup (over 700rwhp) I was using a stock FP regulator. My current setup has an adjustable regulator as a tuning aid.

Rich

 

I would think that any "mail order" tuner would have a real good questionaire that you need to fill out, so you could provide all the required info about your engine and all the mods. Injector size and fuel pressure are required info (along with a lot of other stuff) in order to do the tune.

 

Actually, I do have a order sheet which asks for injector size and brand. I tune for the stock 43.5 PSI unless otherwise specified.