Spark Control System: Description: SPFI

The ignition system on the Single Point Fuel Injection (SPFI) system is composed of a battery, an ignition coil, a distributor, spark plugs, an SPFI control unit and wires. The crank angle sensor built into the distributor detects the reference crank angle and the positioned crank angle.

Electronic signal of both angles is transmitted to SPFI control unit which is used in common with fuel injection system. The SPFI control unit calculates the spark advance angle and determines the spark timing.

The electronic signal of spark timing determined by control unit is transmitted to the power transistor where it makes the primary circuit to ignition coil, whereby high voltage current is generated in the secondary circuit.

The high voltage of secondary circuit is distributed to the spark plug of each cylinder and discharged there. The spark advance angle is calculated from the following 3 factors: engine speed compensation, advance when starting the engine, and advance in all driving conditions except starting the engine, after engine speed exceeds the present value. See Figure .