When I drag race I blow lots of black smoke on full throttle and stinks really bad but runs good at part throttle.

I have a 255l/ph Walbro pump and an adjustable regulator.
No computer tune yet but on the way.

Just wondering what you set it at.

Thanks RYAN

 

Its hard to change WOT fuel with an AFPR, except to make it richer. If you lower the fuel pressure, during closed loop operations the PCM will increase the long term fuel corrections to make up for the missing fuel. Then when you go WOT, the PCM will know it was "adding" fuel via the long term corrections (BLM's) and will use the BLM's in Cell 15 to fuel the engine.... no net change.

If you raise the pressure, you can richen and the PCM will not correct, but that is obviously not going to help you.

One possibility would be to wait until you are ready to race, and then drop the pressure, so the PCM can't make the correction. In order to know how low to go, you would have to know how rich you are currently running. Stock A/F ratio at WOT is typically around 11.7:1. If you wanted to get to 12.8:1, you would have to cut fuel about 8.6%. Lowering the "no vacuum" rail pressure from 43.5psi (stock) to 36.5psi would achieve that.

No substitute for a good tune, after heads & cam

 

Your biggest problem is your stock tune. IMO your car will run a whole lot better once the car is tuned for your mods. An AFPR is not going to do anything since the stock computer will compensate for an increase in fuel pressure.

 

Thanks guys for the reply

If I can't adjust the fuel pressure what should I leave it at for the tune ? Stock 43.5psi (with vacuum line off) or something different.

Thanks RYAN

 

The only reason you would want to deviate from stock pressure (43.5psi, no vacuum) would be if you were trying to squeeze a little extra capacity out of marginal injectors, and reduce duty cycle.

The person who does your tuning - if its a "mail order" tune" - will need to know the pressure you set it at, and the injector brand and flow rating, in order to do the tune.

 

Leave the fuel pressure at stock settings and allow everything to be controlled by the computer when it is retuned.