Turbo TBSS WOT Tuning

[JGoodin86]

I am having some trouble tuning my turbo TBSS. Everything was going good. I was tuned on 8 psi and everything was working fine. I go make some passes and all it wants to do is lean out and pop out of the exhaust. Like shotgun loud. This tune was good enough to make some good power and now it sucks. I am thinking it is my fuel pressure regulator or something. No matter how much fuel I add to the be table it always goes lean. My setup is 80lb siemen deka injectors, dual walbros, -8 feed and stock feed as return, 4.8L motor with LS2 cam, single 78mm turbo, 2.5 bar sd enhancement.

I am thinking it has to be something mechanical and no in the tune, because no matter how much fuel I give it, it doesn't richen up. Attached is my tune and logs.

Thanks,

Jacob

[schpenxel]

Where exactly does the stumble happen?

Why is there no wideband in the logs?

Are you measuring fuel pressure? It does sound like it could be a mechanical issue if increasing fuel, via whatever method, isn't doing anything

Measure fuel pressure.

Why are you not logging knock at least?

Also, just did a quick comparison to my own tune and your boost VE table is WAYYY lower than mine. Like 25% if not more, and mine has been lowered because I added meth injection. How much fuel have you added and where are you adding it?

[JGoodin86]

Stumble starts at around 138-143kpa. Wideband is logged through ac pressure switch. I don't have any knock sensors. I have a guage on my regulator but I can't see it while I am driving. Can you send me a picture of your table so I have a general idea of what it is supposed to look like. It was working well a week or so ago. And on 3psi it is fine. Only when it hits about 5-6psi it starts to stumble

[MikeOD]

Based on your narrowbands, you're pretty lean, but your injector duty cycle is never very high.

Get something on that can log fuel pressure, and go from there. Your PE table looks lean...I'd set that to 1.176 at lower RPM (before the turbo can spool, and then 1.33 at higher RPM...then until you get a better handle on fueling, set the BE table there too...that's a target of 0.75 lambda (11.0 on pump gas). Start then then go...usually turbo cars are a disaster between the dyno and the street...especially if you did it on an inertia dyno and not a load bearing dyno...enough fuel on an inertia dyno is never enough on the street/track, and enough fuel on the street/track looks stupidly rich on an inertia dyno.

I'd also remove your PE delay...set the RPM to 500, lower the PE enable throttle a good deal too.

[MikeOD]

You also have a problem with your VE tables...your boost VE table is actually lower than your regular VE table at 105 KPA...it's really just starting to approach the same VE at 138-143 KPA...that's not good. The 105 KPA rows in both tables should have identical numbers in them...in some cases your boost VE table is a LOT lower (15-20% less fuel the moment it crosses into the boost table).

[schpenxel]

You also have a problem with your VE tables...your boost VE table is actually lower than your regular VE table at 105 KPA...it's really just starting to approach the same VE at 138-143 KPA...that's not good. The 105 KPA rows in both tables should have identical numbers in them...in some cases your boost VE table is a LOT lower (15-20% less fuel the moment it crosses into the boost table).

I noticed that too, forgot to post it.. very strange looking. The only way I've ever seen anything like that is if you have methanol coming on right there and are tuning AFR lambda including meth. Doubt that's it though. Too early for meth.

Agree.. start with taking whatever is in the 105kpa VE column and putting that in the 105kpa of the boost VE. Then try to smooth the higher cells out from there. It shouldn't go down though unless you have a specific reason for it to like methanol injection kicking in.