hey all, so basically heres whats going on- I was hoping for some insight from someone(s). basically first off, here is the setup/details-
-The car is a 2014 Chevy SS LS3 w/ LSA blower (stock, not ported) w/ 2.85" pulley (stock is 2.95"); LS9 cam; stock LS3 heads; Kooks 1 7/8" LTs
These SS cars have been confirmed via physically (by removing fuel pump) AND running VIN of ZL1 and SS sedan to check fuel pump module P/N's- they use the same fuel pump for sure.
Despite using the same fuel pump, they show different p/n for FPCM; however, IMO this should just be a matter of the SS sedan coming with all low, std, and high flow settings at 58 psi; where as the ZL1 comes with varying fuel pressure depending on conditions- mainly that it increases fuel psi under boost conditions (yes I know its not by boost, its by fuel flow lol- but it comes in DURING boost). SO my opinion is that's the only difference, hence tuning my FPCM to the same manner as the ZL1 FPCM data should produce the same results, by all logic....
SO Heres whats going on- we started noticing that at WOT, or at part throttle / high load / 5-7 psi boost (peak boost 9.5 psi) that the fuel pressure actually just immediately drops from the commanded 58 psi to exactly 50 psi, starting around 3750 rpm running up and up, yet it isn't exactly continuing to fall. as a speed shop specializing in LS setups, most with returnless OEM systems, ive seen my fair share of Walbro's running to their limit and watch the rail pressure steadily drop and continue to drop "in sync" with the increasing RPM. Yet THIS just jumps straight from 58 to 50 psi, like almost as if it was commanded, and as the RPMs climb, it just isn't falling further... So we commanded it 68 psi under "high flow" conditions, and logged commanded fuel PSI and actual PSI... SAME thing... it never even tries to raise to the 68, never goes over 60 even when I lowered the threshold for the highflow mode so it would command 68 psi under lighter conditions that seem impossible to be overcoming a ZL1 pump with the simple mods on the car, at 1-2 psi over stock boost... and we are talking 4k rpm here not 6600! so is there something im missing, is my SS sedan's FPCM just not able to accept these modified pressures? because from my professional experience, I cannot see this setup overwhelming the decent sized ZL1/V fuel pump setups, on 9 psi, at 4000 rpm. any help much appreciated.
Thanks,
John