L86 lean until reaching a solid operating temperature

[Dominatorstang]

2017 Sierra L86, 8L90, BTR Stg2 cam, catless longtubes.

I had noticed my fuel trims were much further off on a cold start, but had not focused on it too much because I had not finished dialing my VVE in. Yesterday I spent a long time and lots of fuel on the highway with different gears and speeds, and many stops and writes to get things dialed in.

The next morning I start the truck and it is commanding over 20% positive fuel trims. This is with the MAF disabled, where yesterday my VVE was within 1-2% on the majority and under 5% for the rest.
latest VVE.hpt

This afternoon I logged towing 4-5k pounds for a short drive from a cold start. With it running lean.
drive to petro with trailer.hpl

Here is a log about 30min in on the tow, once everything was up to temperature for a while. The fuel trims are back closer to where they were with tuning yesterday.
down sized vve towing from home to disney dam.hpl


I will try in the morning for a log with MAF on a cold start vs good and warm. Maybe it will help narrow down the cause? Anyone have any thoughts of what I can check?

[pisces_0]

I assume your EVAP solenoid is hooked up and functional?

I've seen EVAP cycles throw STFT way out of whack temporarily.

[Dominatorstang]

I know exactly what you mean. So for that reason, some time ago I unhooked the EVAP connector, plugged port, and disabled all DTC's for it.

[Dominatorstang]

Here is the MAF only log from this morning just moving around the driveway with the trailer still on it. Adding 10-15% fuel for most all.
cold start MAF.hpl

Here is a piece of the MAF log from towing yesterday when pulling in to the drive and moving trailer around too. It was reading much closer and even pulling a little fuel at times.
warm log MAF.hpl

[GHuggins]

You'll need to retune your fueling after making these changes. Also, I don't see how that VVE can be right. It's got a lot of steep walls and unusual dips unless it's just going off of an unusual multiplier somewhere. VVE should always kind of represent airflow into the motor almost exactly like a dyno graph...

[Dominatorstang]

Thank you Ghuggins, those looks like some pretty nice changes and I would not have guessed where to start with them. I did see what you are saying about my VVE on the 3D model, and will keep that in mind.

So the changes you made,
-I noticed some are for the 02 sensors to maybe narrow down the swing and fine tune further for location in long tubes?
-Then Open loop changes which I had noticed my open loop and closed loop fueling % error’s were a few percent or more off from each other. Maybe helps that part?
-And then the flow rate multiplier for injector tip temperature looks like probably a big player?

On my old logs I had been logging injector tip temp and intake valve temp, but took them off a while back when reducing how many channels I was logging. I now have added those back for logging. Any others you suggest I should add while I am at it?

[GHuggins]

I also made some changes to cat warmup injection timing modifier to hopefully get a fuller burn to better go along with that injection timing table. Let me know how it does.

As far as logging goes - the newer platforms like these have some pretty good comm rates, so doesn't hurt to log as much as you can.

[Dominatorstang]

I seen the cat warmup change, but did not know what to think of it since I had most my cat stuff disabled.

Yesterday I had lowered the SOI by 10 points (vs stock) in the idle area to get the more efficient burn like you recommended I try some time ago. I then finished fine tuning the idle area VVE and MAF while normal operating temperature. And tried to better adjust the VVE areas in the places I can not log.

Today I pulled in the changes you posted and did a quick log while the engine was still nice and warm and then one with it cooled. Both are just a quick idle with A/C on and off and then 1000 rpm idle with A/C on and off. It does look like it may have started bringing things closer. At least in the idle area it is around 5% off now. Tomorrow I will have a log with a cold and warm drive to better compare.

updated with Ghuggins updates for temperature.hpt
warm idle and high idle with temp corrections.hpl
cold idle and high idle with temp corrections.hpl

[GHuggins]

You can chase the unicorn by tweaking things another percent or two - may not even be a bad idea to get it down to 2 or 3%, but if it's within 5% I'm not sure I would worry if it's just when cold - that's if it goes back correct when at temp...

[Dominatorstang]

A log on the street did show me it is certainly going the right way. I am now logging a chart setup to match injector flow rate density multiplier using fuel trims and then multiplying them by -1 to invert the positive/negative values. Then multiplying by % half in the tune file.

Thanks for showing me this GHuggins. Also thanks for fixing my cat warmup table to match the SOI table, I did finally notice it was still in play.

[GHuggins]

Not a problem. Glad it worked out for you.