Fueling & Injection - Fuel Return?




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dixonk
05-12-2007, 01:48 AM
At what point or power level should you run a fuel return line?


ChevyChad
05-12-2007, 01:28 PM
I would think anything over 500 rwhp

dixonk
05-12-2007, 03:30 PM
I'm at pretty much the identical power level as you and still don't have a fuel return. Just want to prepare myself for the new motor. Maybe you can explain to me the reasoning behind it?


ChevyChad
05-12-2007, 03:37 PM
LOL I guess I'm wrong then. I just said 500 because thats what I got away with on my stock engine and single line fuel system.

mikep2002
05-12-2007, 08:20 PM
At what point or power level should you run a fuel return line?
I cant believe you got the amount of power you stated on a stock fuel system or even if you had a Walbro/Ractronics kit. Thats impressive alone. I think at the point of moving up to a 408 with an F1 you gonna need a dedicated system that will run off a MAP sensor. Alot of the stand alone systems are kind of noisey. If you hook up the 2nd pump to run off of the MAP the second pump(external) will only come on when you go into boost. Basiclly my understanding is that it is set up like an alky kit and triggered by boost. You might want to talk to Nate over at Nasty to see if he can set you up. He seems to be a big fuel guy around here. If that doesn`t work there is a particular vendor on another well known forum who sells a kit.

dixonk
05-12-2007, 11:10 PM
Ya I need to give Nasty a call. Current setup is 2 Walbro 255's running to the fast fuel rails and a kenne bell boost a pump. Pressure stays at 60PSI consistently at 14 PSI of boost with 18 degrees of timing.

ChevyChad
05-13-2007, 08:57 AM
At 14 psi, your fuel should be at 72psi (58+14). That is why you need a boost referenced FPR. Not sure if they make a FPR that does not have a return on it.

dixonk
05-13-2007, 09:35 AM
Thanks for the great info

Gauge
05-14-2007, 12:21 PM
Pressure stays at 60PSI consistently at 14 PSI of boost with 18 degrees of timing.
I'm not trying to be a smartass here, I really think I might be lacking some fundamental understanding here... what does spark timing have to do with fuel consumption?

No Juice
05-16-2007, 07:04 AM
At 14 psi, your fuel should be at 72psi (58+14). That is why you need a boost referenced FPR. Not sure if they make a FPR that does not have a return on it.

Ok this maybe a dumb question but why do you need a boost referenced FPR? Why does the fuel pressure need to rise with boost? I'm a fuel noob.

Ryan K
05-16-2007, 08:05 AM
injectors work off of the differential pressure across the injector. As intake manifold pressure increases, the d/p goes down reducing the flow capability of the injector. SO to maximize what you are getting out of your particular injector the fuel pressure should rise at the same rate as the manifold. If you have 14 psi in the manifold and a rail pressure of 55 psi the injector is really only seeing a fuel pressure of 55-14=41psi.

No Juice
05-16-2007, 08:22 AM
makes sense

dixonk
05-16-2007, 09:22 AM
Great learning experience.