Why?
Race Director
Joined: Oct 2004
Posts: 12,860
Likes: 4,661
No, IAT is a separate parameter. The ECM has programming that says in effect, "When the AC is running, retard ignition timing by X degrees." This is to help minimize pinging. It has an unintended side effect of causing the engine to produce less horsepower.
You can easily test it. Run your AC from the staging lanes all the way through to the finish line.
Now run your AC in the staging lanes all the way up to the burnout box. Turn your AC off, do your burnout and make your run. Note the difference in ET and mph.
You can easily test it. Run your AC from the staging lanes all the way through to the finish line.
Now run your AC in the staging lanes all the way up to the burnout box. Turn your AC off, do your burnout and make your run. Note the difference in ET and mph.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Good thing someone brought some tech otherwise this thread should be in general.
The PCM doesn't pull timing just because the AC is on. Anyone who has looked at the tunes know's it doesn't.
I did tune mine to go off with TPS (something like 40% or 50% maybe, can't recall) as an experiment but reverted it because the only difference I noticed was the higher interior heat.
The PCM doesn't pull timing just because the AC is on. Anyone who has looked at the tunes know's it doesn't.
I did tune mine to go off with TPS (something like 40% or 50% maybe, can't recall) as an experiment but reverted it because the only difference I noticed was the higher interior heat.
Last edited by lionelhutz; Sep 3, 2020 at 04:39 PM.
Safety Car
Joined: Feb 1999
Posts: 4,043
Likes: 342
From: Central NJ
On a serious note, when you guys are out and pounding on the SC, do you tend to shut the AC or just leave it on...I get this uneasy feeling that leaving the AC on is not too favorable, but that could just be in my head....You know the whole extra AC belt coming into play and additional pulley load overall...
Melting Slicks
Joined: Mar 2018
Posts: 2,502
Likes: 187
From: California
! It’s all stock 
I leave my a/c on .the belts squeaks a bit when activated but when it’s warm after a few turns it’s all good ........Pounding on the S/C Nah I drive with inspiration ..
It’s not favorable because of heat build up in the engine compartment...venting might work and a vara would clear it up some what ...enough ....that would be my remedy.
Last edited by Speedy007; Sep 3, 2020 at 05:25 PM.
