Quote Originally Posted by SnowTh1ef View Post
I wan't to know how to do this
I'm sure there are write-ups floating around... it's actually pretty simple. You usually have an IAT sensor that changes timing slightly based on incoming air temperature. Basically, the IAT is just a resistor that naturally changes resistance with air temperature.

So, instead of using the IAT sensor, you run the wires to a potentiometer with close to the same resistance range as the IAT (this is a knob that changes resistance based on how far you turn it clockwise or counter-clockwise. So basically you're tricking the computer into thinking the temperature outside is warmer or colder based on where you have the knob turned.

Normally, the computer will only change timing a little bit based on temperature... so you change the IAT adder table for timing to be more drastic. For example, set your base tune (without IAT adder) to 15* of timing at WOT. Then scale your IAT adder table between +0 and +5 (or whatever range you need) degrees based on temperature.

So, then you go to the street/track/whatever with the knob set to give +0 timing. Do a run, and check for KR. If no KR, turn the knob enough to give you 1 more degree of timing... and so forth, until you knock, then you can turn the knob back.

I'm sure someone else can describe it more accurately and give more precise instructions, but that's the gist of it.