Supercharged guys please help

[cobra1923]

I've never been a big fan of FMU personally... at low boost, you should be able to troubleshoot / survive with an Adj FP regulator and 19Lbs injectors. If it runs better without the FMU, then it's either hooked up backwards or it's just too much fuel pressure at the wrong time. If you're worried about AFRs (you should be), you can fine tune your FMU to spike the fuel pressure a little later and a little less... or just go with bigger injectors/MAF and ditch the FMU.

 

[raistlin77]

I've never been a big fan of FMU personally... at low boost, you should be able to troubleshoot / survive with an Adj FP regulator and 19Lbs injectors. If it runs better without the FMU, then it's either hooked up backwards or it's just too much fuel pressure at the wrong time. If you're worried about AFRs (you should be), you can fine tune your FMU to spike the fuel pressure a little later and a little less... or just go with bigger injectors/MAF and ditch the FMU.

At this point i will try anything!

 

[90FoxBdy]

Do you have a fuel pressure gauge? How does your fuel pressure act while revving? Does your a/f go rich or lean. Check your fuel lines as they come from the frame rail into the engine bay. The plastic hose pinches very easily especially with the passanger side mount superchargers. The inlet usually pushes against the fuel rails causing them to pinch.

 

[raistlin77]

Do you have a fuel pressure gauge? How does your fuel pressure act while revving? Does your a/f go rich or lean. Check your fuel lines as they come from the frame rail into the engine bay. The plastic hose pinches very easily especially with the passanger side mount superchargers. The inlet usually pushes against the fuel rails causing them to pinch.

Just checked those items did not see anything pinched. Fuel pressure seems constant. It increases with the revs. Fuel pressure without vacuum showing 40psi. I think my next step is to remove the supercharger

 

[89llx]

could be the vac lines under the upper intake, the ones you can-not see, get a mirror

 

[raistlin77]

Thank to everyone for there suggestion Finally figured what was causing it

 

[jrichker]

Thank to everyone for there suggestion Finally figured what was causing it

For the benefit of all the rest of us, tell us what you found.

 

[raistlin77]

Sorry for the lack of info on my last post, i was in a rush to go driving
I had a feeling my problem was related to the supercharger building pressure in the outlet tube at closed throttle. The IAC was having trouble finding its happy spot to control idle with the throttle closing suddenly. I installed a Bosch bypass valve and now it runs like it should. I did a lot of research on bypass valves with superchargers and suggest anyone installing a supercharger (doesn't matter what boost level) to put one in.

 

[Rick 91GT]

That doesnt make sense.....they dont work that way.

 

[raistlin77]

That doesnt make sense.....they dont work that way.[/


I believe it works because there is to much pressure in the discharge tube and the iac has trouble compensating with positive pressure. In a n/a engine the iac doesn't see positive pressure.