Lean idle w/ higher IAT temps

[SSpdDmon]

Anyone know how to manipulate the Charge Temp Blending (or any other table) to richen the AFR as intake temps rise at prolonged idle? (this is for an open-loop tuned car)

[vetteboy2k]

Look at your A0014 if your using a custom operating system, and increase the VE multiplier as the IAT's get hotter

[oztracktuning]

This effect is caused by the IAT reporting a heat soaked temperature and the pcm causing less fuel to be put in to mix with what is in reality much colder air.

The best fix is to move the IAT to a less heat soaked position.

The blending just pads it out with a more stable number.
But the actual leaning out will be right through the rpm range until the actual IAT sensor more accurately matched the true intake air temp.

[Highlander]

Do you think this is a problem on the vette???? it seems to me its in a very good position....

[oztracktuning]

If you log as much as i have in open loop you would see the data very clearly. The issue makes cars lean at launch at drags and rich at the end. If the IAT was further forward it would be possible to get more steady afrs. I am certain of this and will be doing it soon.

[superls1]

If you log as much as i have in open loop you would see the data very clearly. The issue makes cars lean at launch at drags and rich at the end. If the IAT was further forward it would be possible to get more steady afrs. I am certain of this and will be doing it soon.

I can understand the lean at start due to heat soak concept, buy why does it cause them to be rich at the end? In fact, I would say this is the opposite of what many people report as their experience. I have seen numerous threads/debates regarding why cars go lean on the top end. There a fairly recent discussion here: http://ls1tech.com/forums/showthread.php?t=530395

[SSpdDmon]

This effect is caused by the IAT reporting a heat soaked temperature and the pcm causing less fuel to be put in to mix with what is in reality much colder air.

The best fix is to move the IAT to a less heat soaked position.

The blending just pads it out with a more stable number.
But the actual leaning out will be right through the rpm range until the actual IAT sensor more accurately matched the true intake air temp.
Anyone ever prove whether or not this was the solution to the problem of leaner AFRs as temps rise? I've been thinking of going to an open-loop tune for better part throttle performance and don't want to worry about 17:1 AFRs when the IATs jump from 60*F to 100*F.

[Dirk Diggler]

Is timing being pulled when you see these heat soaked conditions? You will see if you 0 out the IAT spark table there wont be that much of a change in your fueling read by the WB

[SSpdDmon]

My IAT tables (still stock) don't pull timing until you hit .22grams/cyl of airflow. True, pulling timing significantly can alter AFRs some. But, that has to be a significant change in spark and it typically richens AFRs. For example, when the trans shifts and TQ MGT pulls timing down to 3*, my AFR will drop from 14.5:1 to 14:1. The kind of lean AFRs being refered to in this thread are more along the lines of 17:1 and 18:1.

[Dirk Diggler]

Ive seen cars drop -2* of timing on the dyno and start reading 2% leaner when in actuality it wasnt IAT over 120*. As a test my bens were dialed in with a current timing table. After driving to work I flashed a tune with -2 across the whole board and noticed all my 1.00 changed to 1.04 which would equate to about 15.2:1

Also because of the staging lanes I have 0'd out some of my IAT table. The reduction in timing was enough to cause the car to perform terrible going through the 60' until the IAT started dropping enough where i was getting full advance back

[Bruce Melton]

I was at the track last night and I could not keep up the tune as the heavy rain soaked air blew off and drier warmer came in.
On the way home it would not even consider idling.
I want my MAF back.

[SSpdDmon]

Interesting. I watched the timing on the ride home and nothing was being held back, which is what I believed to be the case all along. So, I'm not losing timing.

Some food for thought though...

I dropped the Charge Temp Blending table a lot. I let the car sit for 15 minutes or so in order for the IATs to go from ~75 to ~105 and ECTs from ~195 to ~210. The whole time, I only saw AFR reach 15.1:1. I'm going to drop it some more and see if I can keep it even closer. Right now I have about 82% out of the 1st cell and 45% out of the last with a linear fill inbetween. I'll keep everyone posted on what I see.

[TAQuickness]

If you can get to a custom OS A0014 makes short work of the drifting IAT's

[SSpdDmon]

I'm too cheap to fork up the extra $150

[TAQuickness]

I'm too cheap to fork up the extra $150

Sorry to hear that. You'd really like OS5

[TAQuickness]

you can't beat this with a stick!
http://www.forum.efilive.com/showthread.php?t=3416