injectors are too small

[shawnxj]

finally got it back together and drove it around tonight on the 30# injectors and it's much much better. still tuning but cruising speeds top me out at 70% duty cycle instead of the 90% the 24# gave me. that's 70 mph at 2000 rpm. i think if i swap in the 4.56's i have it might improve on it some but really the jeep does awesome with the 4.10's even on 35's. i'll probably swap in the 4.56's anyways since i'm thinking about picking up some 37's soon but that'll be after i move.......so ya i was right. i'm also picking up a walbro 255 from a buddy for cheap since i drop about a 1# of pressure at 4000 rpm and 4 #'s at 6000 rpms. i have my rpm limiter set at 5000 currently but i might bump it up eventually.

[shawnxj]

correction at 2000 rpm i'm running 65 mph not 70....not sure what i was thinking

[I6FAN]

correction at 2000 rpm i'm running 65 mph not 70....not sure what i was thinking

I caught that too....it says your running 4.88's in your signature??? What kind of tranny?

70% duty cycle instead of the 90% the 24# gave me. that's 70 mph at 2000 rpm.

Have you manually check/calculated what your duty cycle is to check against computer? What kind of A/F ratio are you seeing with your wide band?

[shawnxj]

haven't updated my sig. actually have 4.10's now. about to regear soon. as for my a/f i'm still tuning at the moment so it's all over the place but i'm slowly getting it dialed in. the ecu i'm running shows me what the engine load, fuel load, injector pulse width is at whatever rpm i'm running

[SilverXJ]

finally got it back together and drove it around tonight on the 30# injectors and it's much much better. still tuning but cruising speeds top me out at 70% duty cycle instead of the 90% the 24# gave me. that's 70 mph at 2000 rpm.

I'm still trying to understand how this is possible. I'm running the stock PCM, but at cruise that shouldn't matter much. At 70 mph I'm turning about 2250 RPM and the 25# injectors are only at 24% duty cycle. 74% max at WOT near redline.

[shawnxj]

no idea but i've put about 300 miles on it with the new injectors and it's night and day different. no more bucking/jumping around or anything it was doing before. i'm thinking about getting an aeromotive pump cause this stock 1 starts losing pressure at 4000 rpm's but anything under that and she runs just fine. i think i'm going to change out the 4.10's for 4.56's soon as i find a decent used set. curious to see if that helps any

[I6FAN]

Are you sure the exhaust leak is fixed? I was thinking of something that could give the o2 sensor an erroneous mixture, and then compensate by more fuel??? How about manifold vacuum...you did mention the guy was resurfacing the exhaust flange now maybe your not sealing the manifold correctly(?).

[shawnxj]

nope no more exhaust leak

[I6FAN]

How about manifold vacuum...you did mention the guy was resurfacing the exhaust flange now maybe your not sealing the manifold correctly(?).

Just to be clear, I am referring to the intake manifold here. Wondering if it could be sucking air....you did mention it got worse as the engine heated up.

[shawnxj]

nope the computer says the vacuum is fine and i put a machinist edge on the mounting surface and it was perfectly flat

[SilverXJ]

Could the injector timing be off? When are the injectors firing?

Have you had a chance to check your highway mileage?

[shawnxj]

right now it's set for batch so that shouldn't really make a difference but once i find the bug keeping me from switching to sequential it will be sequential

still trying to dial in my fuel curves for everything but highway has me at roughly 13mpg at the moment with 4.10's and 35's. think i can squeeze out another 1-2 mpg with a little more tuning

[SilverXJ]

I wonder if batch fire has anything to do with the high duty cycle

[shawnxj]

why would it?

[SilverXJ]

Its not as efficient at lower RPMS as sequential is.