900 SE Convertible L4-1985cc 2.0L DOHC Turbo EFI (1998)
Ignition Control
On starting, ignition timing is 10° BTDC. To facilitate starting when the coolant temperature is below 0°C, the engine control module will ground the
relevant trigger lead 210 times a second from 10° BTDC to 20° ATDC, which gives rise to the "multispark" function. This function is discontinued at
engine speeds above 900 rpm.
A special ignition control curve is used at idling speed. Normal ignition advance is about 6-8°.
If engine speed drops, as may happen when the radiator fan cuts in, the ignition timing will be advanced to a maximum of 20° BTDC to increase engine
torque and restore engine revs. Similarly, the ignition will be retarded if engine speed increases.
Ignition control during idling compensates for rapid changes in engine idling speed.
When the throttle position moves away from idling, ignition control changes over to normal control depending on load and engine speed.
