im in the process of getting another 4th gen and was curious what fuel pressure you guys with adjustable fpr's are running im running 36 on my car now but i might change it for the next car depending on this post

 

Why would you run it at anything other than stock? If you try to lean the A/F ratio by lowering the pressure (is your 36psi with or without the vacuum line connected?), the PCM will see the reduced flow and increase the pulse widths using the long term fuel corrections (BLM's). Since the BLM's are now "adding" fuel, when the PCM goes into power enrichment mode at WOT, it will use the inflated BLM's in Cell 15. In effect, you have changed nothing.

 

a guy at WS6.com got a peak of 12 horses on the dyno and an average of six across the band by lowering it to the mid 30's and also T.P.I.S. also says that you will be faster if you drop your fuel pressure down around there. call me stupid but i thought i felt it maybe not, anybody else have any suggestions

 

As the computer watches the sensors and learns, the changes are negated. The computer will adjust the injector pulse widths to meet the target air/fuel ratio, no matter what the pressure is.

 

There is no reason to alter FP on a stock or mildly modded 4th gen. AFPR is a waste of $$$ in those circumstances. If, for some reason, you want it richer or leaner the way to do it is to reprogram the PCM. Don't kid yourself.

Rich Krause

 

Actually, Kieth at WS6.com got 16.6HP by reducing the fuel pressure and leaning out the WOT A/F ratio. Apparently you saw that part, but didn't read the "NOTE:" below the dyno chart that explained how the PCM adjusted to the change and all the HP gain disappeared.

Gotta do more than look at the pictures.....