This table adds or removes ignition timing based on intake air temperature. A positive number advances timing by that many degrees, and a negative number retards it. It's often mapped against engine load too, and it can go up to three dimensions, so you can make the correction depend on more than one condition.
Why it matters
Hotter intake air raises cylinder temperatures and makes detonation more likely, especially under boost. Cooler, denser air is more forgiving. A good air temp correction pulls timing when the charge is hot and high load, and leaves it alone at light load, where knock is rarely a problem.
How we set it up
- Put air temperature on one axis and load (MAP or similar) on the other.
- Leave zero in the temperature range where the base map was tuned.
- Add retard in the hot, high load corner, and start conservative. Refine it from logs with knock control running.
- Be cautious adding advance in cold air. Confirm any gain on the dyno first.
This correction is only as good as the reading. Mount the intake air temperature sensor after the intercooler where it sees the real charge temperature.
Other ignition corrections: coolant temp, gear and the corrections overview.
