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

 

Definitely need to investigate and figure out what is wrong... I've never heard of an FSE FPR, but a quick google search states that it is not actually a 1:1 regulator. I would stick to a 1:1 regulator to ensure constant differential pressure.

 

Thanks for the reply buddy. I think they are 1:2 but wouldn't swear. No one mentionwed tis being an issue before so thanks for the advise. Also I have thought about this some more. Hoping someone can confirm and clear up...

When you set the static pressure you are supposed do it with the engine off right? And then ground the Fuel Pump so it keeps the pressure in the system and adjust to 40psi or chosen base pressure.
Hopefully I have got that bit correct to start with.?!

Now the vac/pressure line connected to the FPR connects after the throttle so at idle this is seeing vacuum which in turn would make the fuel pressure at idle lower. Your static pressure would then not be reached until the throttle is open and boost gauge reading 0. then after that as the boost rises so does the fuel pressure. Why mine drops again and then appears to go back up a bit that's another story? Tried a couple of pumps that should flow the juice all the same.

I guess the issue of pressure drop on closed throttle will be magnified on a rising rate type FPR?

Are SARD FPR's any good. I saw some for sale on ebay for a good price. says they are genuine too.

Cheers
Lee