I have been fighting this issue on both my old motor and this motor. When I drop the hammer from a roll (auto car), the car goes immediately lean (like 15-16:1) then drops down to 11.5 and I sometimes get 1-2* of KR following that event. Mind you this is with no boost built yet, basically shoots lean, then slight KR during the lag. I've tried playing with transient fueling and tip-in KR, but haven't made much head way with it. Anyone else seeing this?

 

Sounds like late PE being applied. Have you messed with the MAP threshold to apply PE or any of the other parameters? Does it happen regardless of the starting RPM?

 

PE comes in and the AFR basically goes opposite at first.

This is an older log that shows what is happening.

 

Transient fueling is your friend, play with it more.

 

VE table? What's PE apply ratio? Is it a SD 2/3 bar setup? You're probably seeing load on the street unlike the load on the dyno.

 

my question is does the msec of the injectors follow the lean spike or are they steady. i d just make sure I'm not chasing a wide band problem since its been 2 different motors and I'm assuming 2 different tunes

 

I agree with above, transient fueling. Pe is comannding 11.5, but hasnt taken over yet. I would mess with transient fueling.

 

transient or a bad ve table cell.. but my transienT is stock and I have no issues.

 

Need to know more about the tune like was asked. SD only? It looks like late PE apply. What happens if you floor it from a lower RPM?

 

I have PE come in around 80kpa, then be around 120kpa, but thats just me.

 

what size injectors? I know my 80s took some playing with to get lean tip-in to go away.

 

I've played with it a little, didn't see any difference in the lean spike whatsoever. Guess I gotta tweak it some more.

I forget the actual ratio, I am at work so I'll have to check when I get back home. It is commanding 11.54 so I'd assume the ratio is ~1.27. Car was tuned on the street and at the track, never been on a dyno. Doesn't do this when I am at the track, only from a punch.

Will have to check the msec of the injectors when it does this, don't have my logs here at work. I can't help but think it is possibly a WB issue, but the tune is the same between the two motors. Was running a stock LQ9 long block until #7 gave up and now running a forged 370 so the tune up didn't take much tweaking.

I've tried everything I can think of to get rid of it via the VE table such as adding fuel in the cells right around 100kpa, or the cells it hits on the way to the lean spike but that is just a band aide and doesn't really work or deal with every possible scenario.

OLSD, 3 bar OS. My PE entry is actually pretty aggressive, again, I don't have access to my logs or tunes here at work though so I'll have to post back.

Are you increasing the ratio under BE vs. just PE? I will have to see how my PE entry is setup right now, I believe it is pretty aggressive though. I don't remember off the top of my head how the entry is set up but the rate is maxed out.

These are resized LS3 injectors from FIC, 80lb @ 3bar (92 @ 4bar), running them at 3 bar currently. Had FIC provide me with the injector tables for both 3 and 4 bar, but wondering if I am seeing some issues since I am running them at a lower base fuel pressure then these cars see stock. I wonder if the transient tables would be affected by this lower base fuel pressure.

 

I go to around 12.5 from 80-120kpa, then 11.5 from 120+. The pcm will use the richer of the two for fueling.

 

Ah, good idea. I assume this aids in getting the turbo up to speed?

 

sounds like a fuel pressure issue

 

It may slightly, but I mainly did it so my mileage wouldnt absolutely suck while only in 1 or 2lbs of boost.