900 Series

Ignition ECM controls ignition advance. Ignition ECM uses inputs from the fuel injection ECM, Hall Effect sensor, and coil to calculate advance. A sensor detects any knocking in the engine and sends a signal to the ECM, which then retards ignition timing. On 900 Series Turbo, a pressure signal from the air intake duct controls a distributor-mounted diaphragm which retards timing.