kirschman

I'm building a 355 LE2 heads and cam with a little juice. Going with the bbk 58tb and #30 svo's. Having it dyno tuned. So i'm guessing I'll need it for that, not sure I've heard its not necessary, help me out!!

Injuneer

You "tune" using the tables in the PCM, not an AFPR. There is no "tuning" value in an AFPR. Your stock FPR will hold the required 43.5psi differential pressure between the fuel rails and the intake plenum. You don't need anything else. You tell the tuner you have the stock FPR, and he tunes accordingly.

An AFPR is useful if you want to run your injectors at higher than stock pressure, to increase their flow capacity. But your tuner would have to know that pressure, in order to tune the fuel correctly.

kirschman

Thanks Fred. So what your saying in a nutshell is, its not a necessity?

Injuneer

Agreed. No need for anything other than stock fuel pressure, in general. There are some advantages to running a higher pressure, but they don't relate to tuning, they relate to injector duty cycle, and the reduction of minor pressure variations, in setups that run wide ranges of load, and have ECU's with high resoluion drivers that can control the injectors under those wide variations. My setup runs at 58psi, and it has to be able to control the injectors under normal street driving, and also when they are flowing the fuel for a 300-shot of dry nitrous, obviously not running on a stock PCM.