Thread: what FPR to run and walbro fuel pump ?

Car is running lean only at high rpms and full boost so wanted to check a few things.

1. Fuel pressure is at 43.5 at idle with vacuum disconnected, and since Im running 20 lbs of boost it should go to 63.5 with vacuum connected right.? (3 bar program).
2. Has anyone had problems running a walbro 255 lph fuel pump at 20 lbs off boost. It starts to go lean at 5k really quick on 20 lbs. Iv tried correcting it with a safc but no matter what I do it still goes lean at 5k. Car only goes lean when running more than 10 lbs of boost. Could the pump just slowly be going bad?

what is your fuel pressure when you disconnect your vaccum hose and what injectors are you running......might be maxing them out.

43.5 with vacuum disconnected, 72 lb msd injectors, turbo is a 2871r so they shouldn't be maxed out. I broke my FPR guage earlier in frustration so I got a new gauge on the way, Im going to run it inside the car to see what its doing at 20 lbs of boost. Just wondering if my idea of the FPR is right and if I should be running an HP pump instead of the LP

43.5 with vaccum disconnected is actually alittle low for the amount of boost you are running... thats about factory psi. i say shoot for 4 bar and see what happens, which should be close to 50-55 psi with vaccum disconnected at idle.

My u13 det is pretty much stock minus the intake, exhaust and running 12lbs of boost.....but my fuel pressure at idle is 36 psi with vaccum connected which is factory

Jwt told me that msd injectors don't like running more than 3 bar, its makes them function incorrectly, but I will try that and see what happens. I just wanted to make sure that I needed at least 63.5 at 20 psi of boost

I wish ya luck then.

I run 25lbs of boost and my fuel pressure is set to 3 bar with no signs of leaning out. It depends on what your ecu is set up for. I find that most tuners turn up fuel pressure to compensate for lack of injector but with 720's you should be good. I run 83lb injectors and I have no issues.

you have other problems then the injectors to worry about. If you had a tuneable ecu you could do some things but since you have a jwt your stuck with no tuning. 3bar with 72lb injectors is fine for that ammount of boost, does it just go lean out of nowhere or does something else happen before you go lean? The walboro is fine I know people that run those for a lot more boost than that.

I agree that you need to look elsewhere, other than at the injectors. If you have a JWT, you should be running rich if anything, as their tunes are conservative. If you put a STOCK fuel pressure regulator in, what do you see with the vacuum line disconnected and capped off? Should be around 44~46psi because the Walbro 255lph in tank will bump your base pressure 1~2psi.

From what I'm reading you're using the low pressure Walbro 255 pump. WRONG PUMP!
If you were carburated you'd be fine with the low pressure pump. You're not carburated!
You need the high pressure Walbro 255 pump.

Your understanding of the stock FPR seems to be correct from what I'm reading.
YES! You should be running the HP pump instead of the LP pump!