IAT corrections, 135* IAT vs 105* IAT
 

Couple of quick questions, I had my car tuned and the IAT's were around 130ish at the time.

I recently went to the track this past Friday and my car was running too lean, and i'm wondering if its due to the fact that IAT were in the low 100's (cool fall day).

Would love to hear some experiences.

Hondata S300, GT35R, C16 roughly 560whp.

I ended up having to add about 8-10% fuel to the boost columns in some sections to get the car out of the scary 12.6-12.7 AF range and down to the 11.8-12.0 range.

When the car was originally tuned a few months ago, it was going into the 12.20 range from 8-9k rpm... even that seemed a bit lean to me.

Thoughts?

Re: IAT corrections, 135* IAT vs 105* IAT
 

10% seems like a lot for just 30*F. But if it's consistent then I can't argue. You're doing the right thing by datalogging and tweaking the tune.

Re: IAT corrections, 135* IAT vs 105* IAT
 

Thanks Brian, I wouldn't even feel comfortable making the changes if it weren't for your help over the past year.

The track closes down here soon, so i'll be sure to have the tune cleaned up before next year.

Re: IAT corrections, 135* IAT vs 105* IAT
 

That does seem like a lot for a 30* difference. Maybe take a look at you IAT compensations table for high load and make sure your tuner didn't put some crazy value in there on accident. Better yet post a screen shot of the IAT compensation table. For some of the more experienced tuners to look at. For me I would like to see richer then 12.2 AFR up top if it was my car, but I like conservative timing and fuel numbers. I would target 11.5-11.8 AFR.

I did a really crude calculation for sea level air density and air at 100f is 5% denser than air at 130f. Humidity and elevation of course changes them further, and im sure being boosted makes that effect more noticable.

Re: IAT corrections, 135* IAT vs 105* IAT
 

is the car ever driven in closed loop? if so, it could be that fuel trims are being set due to the part throttle portions of the map being too rich and setting negative trim values.

also, when it was last tuned was it done only on a dyno? or also on the street/strip? dyno's can put incorrect loads on the car if not set up perfectly, which can have a pretty drastic effect on afr's.

Re: IAT corrections, 135* IAT vs 105* IAT
 

Chances are the IAT sensor is in a heat soaked area, and your real IAT is actually lower than 100f. My assumption on why it needed more fuel. You could also have a fuel delivery issue somewhere. Worth looking into.

I think you should contact the tuner and let them know what is up, and see what they suggest.