Engine Coolant Temperature Correction, Turbo

Fig. 43 Coolant Temperature Correction For Ignition:

Under certain conditions, the ignition timing advance curve must be altered to maintain good driveability, and low emissions. Driving under normal cold running conditions, (coolant temperature below 5°C/41°F, and intake manifold pressure below 1.0 bar/0 in. vacuum), the air/fuel mixture takes longer to burn completely. The coolant temperature sensor is used to signal the control unit to advance the ignition timing from the normal timing map to compensate for cold running, Fig. 43.
When the intake manifold pressure is over 1.0 bar (above 0 psi boost), the air temperature sensor is used to signal ignition timing compensation.