I've got a comptech supercharger that I've been tweeking the AFRs using a VAFC and UEGO. I'm curious how you "master tuners" out there tune the car for the changing weather conditions. A 20 degree change in temperature seems to change the AFR readings up to 0.5. Should I just tune in cold weather and let it run a little rich when it's hot out?

 

Tune to the safe side - my car tends to run leaner when it is cooler and richer when it is warmer. So set your AFR so that it is always safe - nothing wrong with being a little rich when the temps are higher.

I use an IAT correction map (EMU) to control it a little. My IAT's can swing 40-50F in the same day, this can result in a 1.5 to 1.8 point swing in my AFR's without the IAT correction map. I now have it dialed in so that it runs 11.8 when ambient temps are 60 to 85, and around 11.5 from 85 to 100. Over 100F I run it at 11.1

 

thats the easy way to do it ... tune it to 11.5 when its cold and you will be fine when its cold . I actually used to enjoy tuning with my son , doing runs and such.

 

"advanced tuners" use advanced software, not a VAFC


With something like the AEM system, you can tune via engine load so temperatures factor into the load but since you tuned for it, you never have to retune for temperature change.

 

Thanks for confirming what I suspected. It was a real surprise for me to see the wide variance in AFRs.

I knew it was only time before the flames started for using the VAFC but I've been very pleased with it so far. It's certainly better than just using comptech's FPR. I can't wait to get a before and after dyno. I had 2 problem areas with the stock comptech kit tuning wise. I was really rich from 5200 to 6000, and from 7800 to 9000. Those areas were running right around a 10.0 (or lower) AFR. I also had a huge kick as Vtec engaged, gaining 50hp in a 300 RPM range. With the VAFC I've leaned out the problem areas and lowered my vtec point. I've almost completely eliminated the "kick", presumably gaining some significant HP between 5000 and 6000 rpms (we shall see). I'm also hoping/expecting to gain some peak HP at the top of the rev range, for bragging rights you know

Thanks again for the comments. I'll post a comparison once I get it on the dyno, assuming I don't blow it up first

 

Good luck,You wont.
And are you at Stock Boost?

 

Yeah, stock boost, 5psi