Spark overspeed

[Johndingess]

Can anyone explain the values an how they affect spark advance? I am new to this so please excuse the stupid question

[2xLS1]

If you are referring to idle adaptive spark overspeed and underspeed, if the idler rpm goes lower or higher that what is commanded in the idle speed table, that amount of timing is either added or subtracted, based on the amount of error, to the base timing amount to try and bring the actual idle speed to what is commanded. The logic being that more timing will raise the idle speed and less timing will lower it.

[Johndingess]

Thank you!