Results 1 to 7 of 7

Thread: Idle underspeed/overspeed timing question

  1. #1

    Idle underspeed/overspeed timing question

    I noticed my idle overspeed and underspeed timing changes when viewed in vcm scanner when the ac is on. It sounds great idling etc with the ac on but when you turn it off i noticed it?s not getting as much timing or retard and sounds different. Is there somewhere to change this? Why would the ac being on affect the timing at idle to be more agressive in the overspeed/underspeed? Sorry for the newb questions, i?ve been working on my own tune for a few weeks now (2007 LS2 A6 C6). I?ll post the tune here if anyone can check it out for me? Thanks in advance! Only mods are K&N drop ins, cat and muffler delete. Longtubes going on here shortly?

  2. #2
    Senior Tuner
    Join Date
    Nov 2006
    Location
    North Carolina
    Posts
    4,831
    The extra load from A/C is enough to change the sound at an idle.

    This doesn't sound like a problem
    [email protected] - [email protected]
    Email tuning!!!, Mail order, Dyno tuning, Performance Parts, Electric Fan Kits, 4l80e swap harnesses, 6l80 -> 4l80e conversion harnesses, Installs

  3. #3
    Tuning Addict edcmat-l1's Avatar
    Join Date
    Aug 2006
    Location
    5BA8
    Posts
    5,447
    Tune and data log if you're looking for help. It's in the stickies. No one can tell anything from a cool story.

    EFI specialist
    Advanced diagnostics, tuning, emissions
    HPtuners dealer and tech support
    email=[email protected]

  4. #4
    I did data log and i?m seeing much less timing advance and retard at idle underspeed/overspeed with the ac off. Thats why I?m trying to figure out what causes that.

  5. #5
    Senior Tuner
    Join Date
    Nov 2017
    Posts
    2,758
    Quote Originally Posted by Corvettechris86 View Post
    I did data log and i?m seeing much less timing advance and retard at idle underspeed/overspeed with the ac off. Thats why I?m trying to figure out what causes that.
    Post the tune and log, on here, so it can be reviewed.

  6. #6
    Tuning Addict edcmat-l1's Avatar
    Join Date
    Aug 2006
    Location
    5BA8
    Posts
    5,447
    Quote Originally Posted by Corvettechris86 View Post
    I did data log and i?m seeing much less timing advance and retard at idle underspeed/overspeed with the ac off. Thats why I?m trying to figure out what causes that.
    Ok then try to figure it out yourself if you don't want anyone else to look at it.

    EFI specialist
    Advanced diagnostics, tuning, emissions
    HPtuners dealer and tech support
    email=[email protected]

  7. #7
    Senior Tuner
    Join Date
    Jun 2004
    Location
    405
    Posts
    3,217
    Because with the extra AC compressor load at idle it will require more timing adjustment to keep the idle stable. It is not a problem and it's just doing what it needs to do to idle.