I need more info on how it works and it's effect on tuning.

 

Think of it as a coolant temp sensor. The intake air temperature sensor is mounted to the air duct housing. The sensor detects intake air temperature and transmits a signal to the PCM. The temperature-sensing unit uses a thermistor that is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in response to the temperature rise. When the air temp is cold the IAT tells the PCM to richen up the fuel and the opposite is true. Some aftermarket companies sell a special IAT that has a fixed reading or resistance of 37 degrees that tricks the PCM to stay in a rich mode because it is seeing the air temp as 37 degrees even if the actual temp is higher like a 100 degrees.

 

How does Knock and the iat relate?

 

If I understand this right, why would you want to excessfuly richen the mixture beyond the PCM's ability. Would that reduce potential power?

 

IAT is used differently in speed-density vs. MAF.

In speed density, air density is inversely proportional to absolute air temperature, so a reduced air temp increases the air density, the increased density increases the ECM's calculated mass air flow rate, and since the ECM wants to maintain a specific A/F ratio, it has to add more fuel to go with the extra air. It doesn't "richen" the mixture... it helps tell the ECM that it needs to add more fuel mass to match the increased air mass.

Putting a fixed value (equivalent to low temperature) resistor in the IAT for a speed-density system will really screw it up. Yes, it will cause the mixture intially to be "richer", but in closed loop the O2 sensors pick that up and the ECM cuts the BLM's to reduce the fuel and the A/F ratio returns to where its supposed to be. Then you enter power enrichment mode, and the ECM will revert to 128 BLM's and will in fact richen the WOT mixture. On an LT1 with stock programming, that's bad, because its already programmed too rich from the factory. With the 3rd Gens, there might be some gain, but I don't know how rich or lean their stock WOT tuning is.

In an MAF setup, the IAT is not used to make any density calculations (unless the MAF sensor fails and the PCM defaults to speed density) so its sort of just collecting data. In OBD-II, the PCM runs diagnostic checks comparing the MAF readings to the mass air flow calculated using speed-density to do a rationality check, but this is a crude comparison, setting P0101 if the low flow MAF readings differ from the speed-density calculation by more than 40%, or 25% at high MAF flow.

There appears to be some hidden tables that may add 3deg of spard advance as long as the IAT readings are within a "normal" range, and that 3deg seems to disappear at higher IAT readings. I know in my aftermarket ECU setup, we adjust ignition timing for both coolant temps and IAT. Increasing inlet air temp increases the tendancy to detonate.