This is a buddies truck who's tune I'm trying to help him un****. Amidst many issues, one weird thing is that every time the throttle is lifted, whether it being from full load or partial, the AFR will peg itself as rich as possible and slooowly creep back to commanded AFR. Any ideas what's causing this?

Truck is:
2006 Silverado HD 6.0 (stock motor)
Turbo that is supposed to be at 8lbs of boost
TAC module on the throttle (possibly part of the issue?)
Otherwise stock truck with the exception of the exhaust.

 

Nobody is hitting 8lbs of boost on stock fuel injectors, so I would make sure that the data entered for the injectors in it matches them and the rest of the fuel system before even speculating about anything else.
edit--I see it has an EFI COS. Lucky for you HPT mapped those a while back.

 

It does have injectors, my bad I forgot to add those to the list of mods. 80# Siemens is all I have. I went searching around and *finally* found injector data that matches what's in the tables in the tune. So AFAIK the injector data is correct.

And yes, tuning this has been a small headache due to the EFI OS. I'd overwrite it with an HPTuners OS however i'm concerned about the TAC module and having issues trying to get that properly tuned if I do (and the last thing I want is to accidentally brick his truck)

 

Yeah, it's the SD 80s. Those injectors are absolutely TERRIBLE down in the lower pulse widths, completely non-linear response below 1.7 ms and virtually impossible to flow match. On top of that your injector data is wrong, but putting in the "correct" data isn't going to fix the problems anyways. Put a modern injector in there from ID, FIC, etc and be amazed.

 

Ill pass that along. Thanks!

 

I see you have already dropped the minimum fuel milligrams under the transient tab. Try zeroing that out and see if it changes anything.

 

if the cylinders are getting filled with fuel under load the throttle is then shut , it should go rich... then trickle back to commanded

 

I had something like this in my C5 (NA) and making the DFCO settings more aggressive helped some.

That didn't solve it completely though so I'm going to be keeping an eye on this thread.

And the first thing I'm gonna try is reducing the minimum pulse widths to zero. Thanks for that tip.

 

It's already set low enough to hit the minimum on those injectors so that shouldn't fix anything at this point. It's just a combination of those injectors, the data being used, etc. The SD 60s were such a good injector for the time, and then they screwed it all up with the 80s.

 

I'm sure you're right, but when his buddy doesn't want to pay for good injectors and asks "have you tried everything", that is one of those "tried everythings". I know what you mean about the SD60s. The ones I put in my GTO back in 2005 came out a couple of years ago for FIC 1000s. I flow tested the 60s before selling them, and they were within about 6% of each other. They were not a matched set when I bought them.