Intake Air Temp (IAT)¶
The temperature of the air entering the engine. Hot air is thinner, so it carries less mass — and it changes the knock picture.
What it is¶
The IAT sensor measures the temperature of the air entering the engine. Where coolant temperature describes the engine's metal, IAT describes the charge — and air temperature directly sets air density.
Why it matters¶
- Charge density — in the speed-density equation, air mass scales inversely with IAT. Hot air carries less mass, so it needs less fuel. A heat-soaked engine (high IAT) that ignores this will run rich.
- Knock — hotter intake air raises combustion temperature and lowers the knock limit, so it also nudges timing. This matters a lot under forced induction, where compression heats the charge — which is exactly why intercoolers exist.
How to tune it¶
IAT is an input the speed-density math already accounts for. What you manage is heat: an intercooler lowers IAT under boost, buying back air mass and knock margin.
Rule of thumb
If fuelling and knock both drift the same way as the engine bay heat-soaks, suspect IAT — it affects density and the knock limit together.
In the game¶
The IAT reading feeds the air-mass calculation and the knock model continuously. Watch it rise on a boosted engine, and fall when an intercooler is fitted.