IROC R/T

A mechanic at work has been working on a 1993 trans am that has been modified. It has a Powerdyne supercharger,headers, bigger TB, aftermarket distributer and maybe a few other things. We really don't know what has all been done to the car but it does not appear to have more than listed although it does have an adjustable fuel pressure regulator and a secondary pump that sits outside of the tank. What should the fuel pressure be set at? I think it would depend on the amount of boost? From what I can tell the powerdyne unit makes 4.5 PSI but the other mechanic is saying 7PSI( no boost guage). It is setting off troubles codes for being lean. Does this thing need bigger injectors? The other guy said he has the fuel pressure maxed out at 46PSI. Also the car does not run as it should. Anyhelp to get pointed in the right direction will be appreciated. thanks

IllusionalTA

iTrader: (9)

no way the fpr is maxed at 46psi.. let alone on a blown car w/ a ext. pump.. unless it's restricted.. has the fpr been checked to be good? i can see it being lean as 46psi ain't nearly enough for a f/i motor.. try bumping it upto 55psi if you can... see how that work's out for ya..

Hardtop94

iTrader: (14)

does the car have the fmu for the blower mine is mounted on the driver side valve cover, 4 dia round guy with vacuum lines that adds more fuel to compensate for the extra air from the blower, mine actually runs quite rich

IROC R/T

By maxed out I mean this as high a pressure he can adjust it to as it will not build more pressure than this.


"does the car have the fmu for the blower mine is mounted on the driver side valve cover, 4 dia round guy with vacuum lines that adds more fuel to compensate for the extra air from the blower, mine actually runs quite rich"

Hey! now were getting somewhere. Yes this car has this unit also- I am really wondering if there is any vacuum getting to that unit? I am thinking their was a vacuum line teed to the distributer to keep it dry in their? I will try to get him to get the customer back in to check this out. And thanks to both you guy's for responding.

harvickgm

iTrader: (10)

ok... first... you dont tune with the fuel pressure... the fuel pressure should be set to stock or whatever the tuner recommends... but it should be set to 43.5psi and a tune with it... if its running lean... maybe the fuel pumps are not pumping enough... check the pressures again... and maybe there lies a problem else where with injectors/O2's/MAF... many things...

IROC R/T

Thanks! this is more info I need. Was not sure how this system compensated for the extra fuel needed for the increased air. I am thinking Hardtop in his post found my problem. Injectors seem to be working fine but do they provide enough fuel? Does it need bigger injectors? If so must the computer be recalibrated? I am a little confused as one is telling me I need more pressure and another is telling me I need less? Also the O2 sensors are operating correctly. Does the 93 have a MAF?

flame

iTrader: (13)

I'm no expert on FI but I'll try and help you understand. The stock fuel pump in the tank supplies the fuel normaly. Having the pressure regulator on the rail set at 46 is fine. As the boost builds the FMU increases fuel pressure to force more fuel through the injectors. The inline pump will come on when boosting to increase the fuel flow. The 93 doesn't use a MAF system. When it goes into boost does the fuel pressure increase?