When the second pump kicks in under boost, did you see a big jump in fuel pressure? did you have to make any adjustments in the tune?

 

you shouldnt see a jump in fuel pressure b/c the fuel pressure regulator will keep the fuel pressure at 45psi or so unless you have a aftermarket one set higher or if its got a boost reference. Pretty much all you get is more volume. the tune should stay the same unless you have messed with settings to compensate for a lean condition due to not having enough fuel do to too small of a pump.

 

Currently running a 2 walbro 255lph intank pumps with KB voltage spike on pump #1. My app is a 97ss LT1 383 D1 FI. Both pumps are on all the time with the option to turn off pump #2 by switch. A boost ref regulator returns fuel to the tank via. 3/8 (-6an) line. For WOT, the regulator will spike fuel rail pressure from 43psi to 49psi when manifold pressure is @ 5psi. I used a Dynojet WB O2 unit to dial in the correct afr in WOT PEvs. rpm closed loop mode. It helped alot. The stock fuel system is gone. Mod with -8an fuel feed. Hope this helps. B.

 

I usually see about a 3psi increase in pressure when I turn the 2nd pump on