IAC: what is diff between min steps & temp hysteresis?

[TheMonkey]

both these variables seem to determine what size bites that the IAC valve should take.

what's the distinction?

i understand how the variables work, but is there a reason to have both?

[grippo]

They do 2 separate things. The min step is there because some people have trouble moving 1 step at a time - the motor may or may not execute it. But if you only move when you have accumulated say 4 steps, then the motor moves properly.

The hysteresis variable is there to prevent the motor constantly switching back and forth. When you reach a temperature, it won't move in the other direction unless the temp drops by more than say 5 deg. That way noise won't cause it to be constatntly moving +/- 1 step and wearing the motor.

[TheMonkey]

okay, thanks Al.

i was thinking that hysteresis was also like a 'bite size'. so that if you had it set to 5*, that IAC would only move whenever temps moved by 5* chunks even if it was steady in the same direction.

but, it sounds like hysteresis determines how large of a temp reversal it needs to be, and the min steps is how large the chunk size needs to be in any direction.

IF in a certain IAC step table with a straight line, 10 steps = 5*, and you set hysteresis to 1*, and min step size to 10.... would that effectively set hysteresis to 5* (even though it's programmed as 1*)?

[grippo]

IF in a certain IAC step table with a straight line, 10 steps = 5*, and you set hysteresis to 1*, and min step size to 10.... would that effectively set hysteresis to 5* (even though it's programmed as 1*)?

Yes.