When running 720cc x 4 and a walbro is it needed to upgrade the fpr?

 

Unlikely. Remember the FPR works a bit like a turbo's wastegate. If it's too small you get too much fuel pressure because it can't get fuel out of the rail fast enough. It doesn't restrict fuel flow into the engine; quite the opposite. It needs to be replaced if you can't keep a constant pressure differential between the fuel rail and the manifold.

 

Well, I have read in other threads that the walbro over rates the PSI of the stock FPR. I guess the stock FPR is rated up to 45 psi.

 

Information reguarding Fuel pressure regulating is quite poor on the fourm. That or I am not looking hard enough.

 

Put it this way, you won't be sorry if you got a good FPR. It sounds like you're shooting for some good power with that setup, so why do things halfway?

 

I am looking for 290 ~ 300 at the wheel. I also want to stay away from maxing out the injectors

 

Could someone give an write-up or a quick walkthrough of how an aftermarket FPR is set up? Is the stock FPR bypassed? This is actually one thing Im quite unsure of..

 

 

You remove the stock FPR, and plumb the aftermarket FPR in its place. Not all that hard.

 

So when exactly is a FPR actually needed?, at what point of mods should you have one?

 

RETed had some illustration of a parallel fuel setup with an FPR. i'll have to post it when i get home (i think his site is down)

 

thats a good question.. i need to acquire some knowledge about FPR's myself cause i really dont even know why you need them.

don't they limit the fuel pressure at the fuel rail so too much/too little fuel doesnt get to the injectors?

 

Here's a good description of how a FPR works for anyone wanting to know.

- Cooper Lacy



(from the Megasquirt website)

 

I think with the walbros, so much fuel is pumped in that the spring is pegged.