[Joshinator99]

Originally Posted by KingLT1

Today I finished up tuning my brothers C7Z M7. It's a Heads/Cam 11.1 compression LT4 with Maggie 2300. Catless headers and Cordes 5" intake.

Fuel system mods:

FIC +30 Injectors
LPE HPFP
Stock low side with JMS

Currently running E61

I am commanding 2500psi rail pressure & .82 Lambda AFR. 20-21 degrees of timing.

@ 13.5psi, Injector pulse widths are only 5.4ms, rail pressure 2400psi, low side does taper down to 50psi @ 6800rpm.

I was surprised how lowering the rail pressure from 2900 to 2400 took some strain off the low side being it would only tolerate E40 before. This did increase the Injector pulse widths from 5.0 to 5.4ms but that is still plenty of headroom.

He is going to swap in the ZR1 low side pump and we are going to try for E70.

Just wanted to share this info for those looking at fueling options. These FIC's are super easy to tune and the car drives no different then it did with the factory stuff.

Not cheap by any means but if you are looking at sticking with strictly DI for fueling then these are worth looking at for sure.

Great info! My brother is running the XDI +60 injectors and that same premise was promised by XDI (bigger injectors can run lower pressure, allowing more headroom). Unfortunately, it didn’t really work that way. When the high pressure was dropped to allow more HPFP headroom, power dropped off with it. They really wanted the 2900 psi which the LT4 HPFP with cam couldn’t do.