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DC CDI Theory
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SEA DOO DC CDI
DC CDI Theory
DC CDI Systems
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SEA DOO DC CDI
DC CDI Theory
Objective
 The participants will identify the
components and their function of a
Battery Powered Capacitor Discharge
Ignition system. This will be
demonstrated by the participants
completing a written exam with 80
percent accuracy.
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SEA DOO DC CDI
DC CDI Theory
DC CDI Systems
 In the world of personal watercraft the ignition
system design has been exclusively self-powered
capacitor discharge ignition (AC CDI) systems.
 Today, due to new standards of pollution control, the
AC CDI system is being replaced by a battery
powered CDI (DC CDI) system, which is one of the
most efficient ignition systems available today.
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SEA DOO DC CDI
DC CDI Theory
DC CDI Systems (cont’d)
 The DC-CDI ignition system is similar to an AC CDI
system except that the battery is used as the source
instead of an AC source (exciter) coil.
 In addition, except for the DC-DC converter, the DCCDI ignition control module is identical to the AC CDI
unit.
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DC CDI Theory
DC CDI Systems (cont’d)
 There is a capacitor in the black box that's charged
to several hundred volts by a DC to DC converter
(electronic oscillator) that steps up the 12 volts DC
from the battery.
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SEA DOO DC CDI
DC CDI Theory
Capacitor Charge
220 volts capacitor charge
Battery Volt (12v).
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220 Volts
SEA DOO DC CDI
DC CDI Theory
DC CDI Systems (cont’d)
 Then, at the right time, a switch (magnetic) that's
actuated by a disk on the end of the crankshaft puts
out a pulse that causes the SCR (also in the black
box) to dump the capacitor's several hundred volts
into the coil.
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SEA DOO DC CDI
DC CDI Theory
Ignition Pulse Generator
2 ~ 3 Volts
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DC CDI Theory
Capacitor Discharge
220 volts capacitor discharge
Inducing voltage into the secondary coil
220 volts
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SEA DOO DC CDI
DC CDI Theory
DC CDI Systems (cont’d)
 The coil (acting as a transformer) takes the 220 volt
pulse and transforms it to approximately 30,000
volts for the spark plug.
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SEA DOO DC CDI
DC CDI Theory
Secondary Current Loop
30 Kv spark
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DC CDI Theory
End
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