For some reason my car feels like it pulls better top end with the A/C on. I know I'm getting false knock above 4000rpm (datamaster). I haven't had a chance to check but is it possible it's not sensing knock with the A/C on? The car also sounds different with the the air on. Am I crazy or is the A/C affecting timing?

 

my inital thought would be that the bearings in the AC clutch are bad... they may be rattling and causing false knock readings, but when the AC is on, the clutch is grabbing the compressor, so the bearings arnt rattling....

just a idea..

 

AC on adds timing there is a table in the PCM for AC on timing vs. temperature, so if your AC is on but the clutch isn't engaging because its broken or its just not putting a big load on your engine maybe cuz you have under drive pulleys or something you'll benifit from the extra timing, but remember, when you got to WOT AC automatically turns off anyways so it shouldn't cause it.

Matt.

 

What I meant was since the A/C is on maybe the computer isn't pulling the timing out. Somehow the knock sensor is desensatized. I know the car definitely sounds different.