IGNITION TIMING AND CONTROL FOR CURRENT CARRYING TIME



Ignition timing is pre-set according to engine driving conditions. Compensations are made according to pre-set values depending on conditions such as engine coolant temperature, battery voltage etc. to decide optimum ignition timing. Primary current connect/disconnect signal is sent to the power transistor to control ignition timing. Ignition is done in sequence of cylinders 1, 3, 4, 2.
System Configuration Diagram


1. Ignition power control


Based on the crankshaft position sensor signal and camshaft position sensor signal, engine-ECU decides the ignition cylinder, calculates the ignition timing and sends the ignition coil primary current connect/disconnect signal to the power transistor of each cylinder in the ignition sequence.



2. Spark-advance control and current carrying time control



[During start]


Engine-ECU initiates ignition at fixed ignition timing (5° BTDC) synchronized with the crankshaft position sensor signal.

[During normal operation]


After determining the basic spark-advance based on the intake air volume and engine speed, engine-ECU makes compensations based on input from various sensors to control the optimum spark-advance and current carrying time.

List of main compensations for spark-advance control and current carrying time control
Compensations
Content
Intake air temperature compensation
Compensation is made according to intake air temperature. The higher the intake air temperature the greater the delay in ignition timing.
Engine coolant temperature compensation
Compensation is made according to engine coolant temperature. The lower the engine coolant temperature the greater the advance in ignition timing.
Knocking compensation
Compensation is made according to generation of knocking. The greater the knocking the greater the delay in ignition timing.
Stable idle compensation
Compensation is made according to change in idle speed. In case engine speed becomes lower than target speed, ignition timing is advanced.
Delay compensation when changing shift
During change of shift, sparking is delayed compared to normal ignition timing to reduce engine output torque and absorb the shock of the shift change.
Battery voltage compensation
Compensation is made depending on battery voltage. The lower the battery voltage the greater the current carrying time and when battery voltage is high current carrying time is shortened.

[Control for checking ignition timing]


During basic ignition timing set mode for M.U.T.-III actuator test function, sparking is done with fixed ignition timing (5° BTDC) synchronized with crankshaft position sensor signal.