So if I understand this correctly as the weather gets colder the afr's will go leaner right? I would love to hear experiences with this happening on VIII's and IX's. I was tuned with outside air temps being 95 now recently an early cold front dropped the morning temps into the high 50's. I did a couple pulls this morning without logging and was noticing break up under full boost. I'm guessing I was going lean as I was at 12.1 before and thinking it probably went over 13 causing breakup.

 

I'm going to go out on a limb and say that fluctuation is more than just temp. The change in temp makes the air denser so your boost will fluctuate causing your car to run leaner because you're probably hitting load cells you were never tuned for. For instance...

After work at 90+ degrees and I hit 37.2ish lbs of boost, peak load 420 or so.
Before work it was 65 degrees, I hit almost 40 lbs of boost, peak load of 475.

Now for my tune it is mapped to load cell max of 500 which I'll surely pass when the temp drops lower so my tuner tunes all the load cells very similar for 400 on. For guys running smaller turbos hitting load cells in the center of your fuel map a lot of tuners hit a range of load cells in middle then as it gets to a higher load they don't touch them because your car doesn't hit them so they may be tuned leaner.

Likely the issue is this, not that it's the temp alone. Make sense? To help us address this we need your car info, mods, type of boost controller, air temp correction turned on, etc. Who tuned your car? Generally guys have a touch up tune for winter or just turn the boost down a tad bit to compensate.

 

Your map should have an Air Temp Correction table. If that is not setup correctly then you will have huge changes in your AFR as the temps change. I am on an AEM EMS, and that is one of the major tables to change if you want a car that runs well in all conditions.

 

mine goes lean in cold weather. i have been tweaking the afr table in the winter, but the correct fix is to tweak the air density table.