IGNITION
Page 2A-10 90-857046R1 NOVEMBER 2001
Ignition Description
The ignition system uses CDI (Capacitor Discharge Ignition). This system provides quick
voltage buildup and strong spark required for high power and high performance engines.
The CDI ignition system does not incorporate mechanically operated points, therefore mak-
ing this CDI unit virtually maintenance free.
As the flywheel rotates, electrical power (alternating current) is produced by the capacitor
charging coil. This power is rectified by diodes so that direct current voltage is utilized by
the ignition system. When the ignition driver is off, the D.C. voltage is stored by the capacitor.
Once capacitor voltage is charged to its potential, a gate signal is applied on the SCR and
the residual current is dissipated through the capacitor charging coils.
The electronic control module (ECM) activates the ignition driver in the ECM which allows
the capacitor to discharge, causing the spark to occur. Ignition timing is regulated by the
ECM which receives status input from a variety of sensors. These sensors include the crank
position sensor, engine temperature and oil pressure sender.
The voltage discharged to the primary winding of the ignition coil causes a surge of high volt-
age to be induced in the secondary winding of the ignition coil. This induced voltage of suffi-
cient amplitude causes the spark plugs to fire.
Ignition Component Description
Electronic Control Module (ECM)
Under normal operating conditions the ECM unit controls the following:
1. Controls ignition spark timing by monitoring the crank position sensor, the engine tem-
perature sensor, and the oil pressure sensor.
2. Maintains normal idle timing (see specification).
3. Engine stall.
a. The stall saver feature will advance the ignition timing to 15° BTDC if engine falls
below 615 RPM.
4. Advances spark timing quickly to 28° BTDC under hard acceleration conditions.
5. Limits RPM of the engine in the event of a over speed condition (cavitation, no load on
propeller, and/or under propped), as listed in the following steps:
a. Soft Reduction: Ignition timing is gradually retarded to keep engine RPM below
6200.
b. Spark Cut-Out Reduction: Percentages of ignition spark will be cut-out according to
the degree of over speed RPM reached.
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