JetMech442

iTrader: (1)

My Setup
LS1b, EFILIVE
Injectors: PN 12554271, 97-98 ls1 injectors, rated at 28.5lbs/hr @ 58psi
Non Vaccuum referenced-walbro pump with vette filter regulator.
Equation for Scaling
Q2 = Q2*(SQRT(P2/P1)).
Where Q1 = 28 lbs/hr.
P1 = 58 psi.
P2 = 58+vacuum_psi.
The injector table goes up to a max of 11.6 psi vacuum.

Question
My issue is that my mail order tune starts at 28 lbs/hr and only goes up to 29 @11.6 vacuum. My calcs show it should go up to 31.2 lbs/hr@11.6.

IS there something I’m missing here(like experience that my mail order tuner has)?
Does fuel pressure normally drop from 58 at WOT by a few psi?

I could really use some guidance here, anything you guys have would be helpful. Thanks.

JetMech442

iTrader: (1)

Okay, just to follow up with what I've learned....

Below is a graph of injector flow vs manifold vacuum as is found in the LS1b OS under {B4001} Inejctor Flow Rate. The left side of the X axis depicts atmosphere(WOT-ish) and the right hand side is high vacuum.

Everything I've read says the injectors are rated at 28.5 lbs/hr @ 58 psi. For some reason, the 98 camaro tune I downloaded starts at 28.7 lbs/hr. Not sure why, but I'm going to use these values since I trust GM knows better than I do. At least the camaro/calculation lines trend together with a small offset, wheras the mail order line doesn't seem correct at all.

Either way, I'll start with the camaro values. My fuel pressure gage at the rail only says 56 psi, so I'll modify it to reflect that before I begin Calc.Vet tuning. Hope this helps someone.

LSX Power Tuning

iTrader: (4)

I would just use the stock gm data for the injectors.