Ignition System; Ignition Control System - Suzuki DF 90 Service Manual

3-12 ENGINE CONTROL SYSTEM

IGNITION SYSTEM

The ignition system used by the DF90/DF115 is a fully transistorized, electronic microcomputer timing ad-
vanced type.
This system is totally battery powered, with the ECM controlling all ignition timing functions.
The ignition system is composed of the ignition coil, spark plug and components for system control (ECM,
sensor, switch, etc.).
When the ignition switch is "ON", battery voltage (12V) is applied to the circuit as shown in the illustration.
At the calculated time of ignition, the transistor in the ECM turns "OFF", breaking the ground circuit.
In this way, a mutual induction high voltage occurs in the ignition coil secondary side and spark is generated.
Battery
charge
coil
Rectifier &
regulator
30A fuse
60A fuse
Battery

IGNITION CONTROL SYSTEM

OUTLINE
Sensors at specific points on the engine monitor current engine conditions and send signals to the ECM.
Based on these signals, the ECM determines the optimum ignition timing and releases voltage to the ignition
coils.
Basic sensors
MAP sensor :
Informs ECM of intake manifold pressure.
CKP sensor :
Informs ECM of engine speed and crankshaft angle.
Compensating sensors
Cylinder temperature sensor :
Informs ECM of cylinder temperature.
Others
CTP switch :
Informs ECM of throttle position (open / closed).
Ignition switch :
Informs ECM of "START" signal.
ECM
main
relay
Ignition
switch
ECM
Sensor / switch
CPU
signal input
Ignition coil
12V
Spark plug
Ignition timing is determined by
a digital map designed in rela-
tion to intake manifold pres-
sure and engine speed.
Ignition timing compensation
Spark plug
Spark timing
(Voltage)
A terminal voltage (Time)
ECM
Signal Signal
Ign.coil Ign.coil