Step Corrective Advance Angle

The final step in determining optimum or final spark advance angle is calculation of corrective advance angle. Input sensors used in corrective advance angle calculations are:

• Engine Water Temperature (THW)

• Electronically Controlled Transmission (ECT)

The biggest advantage of ECU controlled spark advance is the system's ability to adjust timing for all possible variables in the ideal advance angle equation. The corrective advance angle calculation accomplishes this by fine tuning the advance angle for changes in coolant temperature, engine detonation, transmission shift status, altitude, accessory status, and other variables.

• ECU advances spark angle for cold engine operation and retards for over-temperature conditions.

• ECU retards spark angle when detonation is detected.

• ECU advances spark angle for high altitude operation (models equipped with HAC sensor).

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