I had to go and put the car on the dyno again at the weekend as I had changed my coils which had been dodgy for a while. I had fiddled with the FPR to check for a fuel leak but set this back to 40psi static before going. First run the car was way short on fuel mid range onwards with the biggest shortage being somehwere around 4k-6k. I watched the gauge on the FPR during a run and it starts at around 20psi on low rpm then builds to just over 60psi with throttle open then as the revs build the guage starts to drop again back to around 40psi where it holds and if anything just before you lift at full chat it will start to rise a touch over 40psi. I am wondering if my misfire I thought was coils may partly have been fuel although the plugs were plenty dark when I swapped them out and I know for a fact the coils were dicky as it was eating plugs!
Car is running 850s all round, FSE FPR, a bosch style pump, and 15psi boost. I remember that the fuel pressure tended to drop off full chat when it was first tuned a while ago but not so much as this. In the end we set the base pressure to 47psi to compensate and now it fuels fine if not a touch rich for safety. (still behaves the same pressure wise)
Any thoughts would be grat.

Thank you
Lee

 

Any takers on this one please guys?

Cheers
Lee

 

It sounds like you may have a flow issue. You probably already know that the FPR should change one psi of fuel pressure for each psi of boost or vacuum.

Pressure at idle =28 psi (20 in.Hg or –10 psi)
Pressure at idle vacuum line removed = 38 psi
Pressure at 10 psi boost = 48 psi

Fuel filter clogged? Pick-up sock dirty?

Barry

 

Cheers for the thoughts Barry, I have got a new filter and Sock when I fitted the new pump.. Going to try a new FPR this week as I heard a lot of people with similar problems running FSE regulators. Got a bit of a bad rep so it seems! Rate of change of pressure does depend on the FPR rate.. ie. if it was 1:1 you would be correct but I am pretty sure the FSE is like 1.2 or something and clearly does not work the same under vac that is does at pressure! A right mess!

Cheers
Lee