roastin240

iTrader: (13)

Running N/A my AFR is rock solid 12.8 AFR. When I roll into my 100 shot, my AFR leans out to ~13.8 and slowly (window switch 3K - 6K) richens up until I am at about 11.5 - 12.0 AFR a little bit before the window.

I need to hook up a fuel pressure gauge and duct tape it to the windsheild to verify...but I am thinking the initial fuel demands are not met (fuel solenoid open and fuel pressure drops) by my fuel pump and then it catches up and regains pressure (58psi), producing ~12:1 AFR which would mean this is the realistic AFR it is jetted at given constant FP.

Walbro 255lph (not hot wired)
Stock S10 fuel line
Stock LS1 fuel rail (97-98 return style with vacuum reference)
Stock LS1 28.8 lb injectors
Fuel feed to solenoid off schrader valve on fuel rail

1. Im going to check FP. If it dips when I hit the window, I will try hotwiring it to 13.5V. That will give ~15-20% more flow based on the charts I have seen.

2. Obviously a larger fuel feed would be good.

3. Worse case, drop FP, drop in larger injectors and re-calibrate. Fuel pump will flow a bit more at 3 bar rather than 4 bar. Not looking to go with a different pump.

Anything else I should look for? Thanks

roastin240

iTrader: (13)

To add to that, the recommended ZEX jets (I understand this is a safe starting point) are:

N - 0.046
F - 0.028

I am running a 0.020 and its rich still.

I am wondering if the IAT retard box I built is dumping more fuel through the injectors. I tell the PCM it is running at like 240 deg F. However my PCM is a 99, and there are not accessible fuel enrichment tables w/ respect to IAT in HPTuners. I need to hook up my 2000 PCM and see if this is different.

93camaro_zzz

iTrader: (13)

I think you are on the right track. Check the fuel pressure. Do you know what base pressure you are running? But (1) 255 pump should be enough for a 100 shot. Especially if you are stock H/C.

NitrousExpress

iTrader: (4)

Fuel pump would be the first suspect for me. Let me know what you come up with after watching the fuel pressure gauge.

Good luck.

-Garrett

FEAR LS

iTrader: (8)

Return style fuel system? If it's stock LS, then it's not. More than likely air is getting trapped and causing the lean spike. Just a suggestion.

GIMPY02

the lean spike could also be from the fuel lines going from the fuel rail to solenoids and solenoid to plate are to long. Remember ur fuel is coming out at 58psi. Nitrous comes out at whatever ur bottle pressure is at which should be 950psi. I run just a 255 with no hotwire kit when I shortened my fuel lines on my old kit the lean spike went away and it didn't hesitate at all. I spray 200 now with no problems

roastin240

iTrader: (13)

It is return style, and yes it is stock LS rails. The 97-98 Corvette had return style rails and operated at 58psi with a vacuum reference to the regulator, like all return systems do.


I also thought about line length and the fuel delay. 58 psi versus 1000psi, ya they will get there at different times. Line from the rail to solenoid is ~30 inches long. Then solenoid to fogger nozzle for both nitrous and fuel are about 24 inches long.

FEAR LS

iTrader: (8)

LOL, Had to hit me with the only LS rail that's return style. Touche'

Slipped my mind due to its rarity.