jon1440

2 Walbro 450 pumps. Both connected to a Y block. -8 coming out of Y block to fuel filter then to the back of one of the rails.

-8 is used through both rails, and -6 coming out the back of one into a boost ref. fuel pressure reg. Then I'm using the stock 3/8 feed line as my return back to the tank. The stock fuel filter has been removed.

I'm planning on running a pressure switch for the second pump. I am running 2 relays for the fuel pumps so that they run in parallel. I also upgraded the wiring to 10 gauge.

The pressure switch hasn't been installed yet, but my concern is when testing the second pump I notice a 15 psi fuel pressure increase. Ideally I'd think that I need to have the same pressure whether 1 or 2 pumps is on. I'm not sure how I could tune around this. Probably not.

I'm running 43.5 psi base pressure and when the second pump kicks on pressure jumps to 60 psi.

If I left it like this I'd be over fueling.

So should I just run both pumps on all the time and adjust it back down to 43.5 psi? And make a new tune for the new fuel pressure.

I had read many builds similar to this and I'm trying to figure out how they compensated for this.

03sierraslt

iTrader: (22)

Are you testing at idle or at wide open under a load? Is this setup going to be boosted? If so what’s the planned power and fuel?

Atomic

iTrader: (42)

At idle or off you arent using any fuel, but when you need the second pump at 3-4psi or whatever then youll be using some so the regulator wont have to bypass as much. What FPR are you using? The ideal solution is a bigger/better one that can handle the flow.

03sierraslt

iTrader: (22)

I bet the return line is a restriction before the regulator is.

jon1440

13129 Aeromotive is what I'm using. -6 inlets and bypass.

6.0ls, turbo, 80lb injectors. The injectors will probably be the next limiting thing. At idle with vacuum unhooked I have it set at 43.5 psi. I ground out the second pump and pressure jumps to just shy of 60 psi.

My plan is to run e85. Already have everything installed to do so.

03sierraslt

iTrader: (22)

That is a lot of fuel to try and bypass at idle. That is not a accurate indication of what’s going to happen under load