Flow for 0280-155-715 Injectors?

[nosigma]

These are the injectors I have in my engine. I run very lean over 3500 rpm (25:1). I have seen rating from 22 to 26 lbs at 43psi listed on the internet. Cam is Comp Cams 68-232-4. Head flow is 264cfm at 0.50 lift intake BUT I have a stock XJ throttle body right now. I think I need bigger injectors. MAP sensor voltage at 5.08 volts. Any suggestions for injectors or other fixes?

John

[SilverXJ]

What year/fuel pressure? They flow around 24.5 lb/hr @43.5 PSI.

[nosigma]

The engine is a 95 with the return line system. I have an adjustable FPR set at 50 lbs. I have an adjustable MAP sensor set to 5.08V. I use an innovate wide band system to monitor AFR. It Idles a touch rich (13.5:1) after warm up. Idle is near perfect when cold at 14.5:1 AFR. I was thinking about going to a bigger injector to try and solve the lean out problem, maybe 28lbs/hr at 43psi. Though I think this may make the idle even richer and ruin the cruise mixture. I could drop the fuel pressure to reduce idle richness, and raise the map voltage to try and fix the open throttle lean conditions.

Another alternative is to scrap the OBD1 system and go with a mega squirt so I can get good control over mixture and make best use of the wide band AFR. Someone must have successfully run the 68-232-4 cam in an OBD1 without going 25:1 lean at WOT.

John

[SilverXJ]

Being that it idles rich when warm and reading the O2 sensors it might be having problems controlling the injectors. I would try to dial back the pressure a bit and see what it does.

[Cheromaniac]

I run very lean over 3500 rpm (25:1).

Could your fuel pump be on its way out?

[SilverXJ]

I would definitely put a fuel pressure gauge and drive it to see what the fuel pressure does when you hit that 25:1. If the injectors were too small I would expect more like a number around 16 or 15:1 around WOT. 25:1 is very lean and I don't see slightly small injectors doing that. A fuel pump can be fine at idle and other RPMs, but when you really need the volume it will fall on its face. What doe sit feel like when you hit that 25:1 spot? I would expect that it feels like you hit a brick wall.