FPR/pump questions.

a friend of mine is swaping a VR4 vg63 into his old hatch mirage, and wants to run a walbro 255 fuel pump. he tells me the pump will be getting 13.4 volts, and is confused about how high his fuel pressure will be. i told him that the FPR should sort out any issues with high fuel pressure because that is it's job

basically i'm wondering if he'll need an aftermarket adjustable FPR like a sard for this. he's gonna run a T04E so he'll be needing plenty of fuel.

under what circumstances does somebody need an aftermarket FPR? when the engine needs more fuel OR when the pump is giving more fuel???

when you get a highter pressure or highter flowing fuel pump an adjustable FPR is HIGHLY recommended

its purely a question of flow of the FPR. If the fuel pump has too much flow for the return line on the FPR, then the pressure will climb

if the feed line to the FPR is too restrictive, then the fuel pump will be limited by that, which will make it work harder for no added benefit

The question I'd be asking is, does it *need* more flow? a 255 is a popular pump for forced induction. If that is why he's installing it, he needs a boost-happy FPR anyway, but you'd want a higher flow FPR IMO

I put a Walbro 255 pump on my turbo car and had no problems with the GM FPR. The return line was 5/16 dia., I think. My only objection with the pump was that it was a bit noisy when cold. The upper pressure limit for the pump was about 105 PSI (the blocked line test). I only ran it at about 80 PSI, with a rising rate regulator, so there was plenty of flow volume.
As an aside, my OEM pump would run about 45 PSI at atmospheric, and about 55 PSI at 10 lbs boost. Since the pump wasn't capable of going over 60 PSI (the blocked line test again), a higher pressure pump was necessary.

just because a pump is capable of acheiving a dead head psi, doesn't mean it'll flow anything at that psi. Gotta be careful on that