What the table does
Your main ignition map is tuned at normal operating temperature. The Coolant Temp Correction table adjusts that timing when the engine is colder or hotter. Each cell is a number of degrees: positive values add advance, negative values take it away. It's on by default, and it can be mapped in up to three dimensions, so most tuners use coolant temperature on one axis and engine load on the other.
Why you'd use it
- Cold engine: a cold engine burns fuel more slowly, so a little extra advance can help it run cleanly and warm up faster.
- Hot engine: heat makes an engine more prone to knock, so pulling timing as coolant temperature climbs past normal is a sensible safety margin, especially under load.
Mapping against load lets you keep light-load cruise timing while pulling more under boost or full throttle, where detonation does the most damage.
How we approach it
Leave the normal operating range at zero so the main map is what's being used most of the time. Make changes in small steps, and confirm with logs and knock monitoring rather than by ear. Be most careful on the hot side: that's where the table protects the engine.
Related tables work the same way for other inputs, including air temperature, gear and fuel composition. See also post start ignition correction.
