Section 08
ELECTRICAL SYSTEM
Sub-Section 02
(IGNITION SYSTEM)
08-02-2
787 Engine
The 787 engine has a digital DC-CDI (Direct Cur-
rent-Capacitor Discharge Ignition) system. The
high amperage / voltage components are located
into a rear electrical box (next to the battery). The
other components are located in the conventional
electrical box. The ignition system includes the
following components :
1. Rotor
2. Trigger coil
3. MPEM
4. Digital DC-CDI module
5. Holder relay
6. Ignition coil
Magneto Rotor
/
Trigger Coil
The trigger coil is mounted outside the rotor (in-
side the magneto housing of the engine) and is
not adjustable. It’s purpose is to signal the DC-CDI
to be conductive at the proper number of degrees
before TDC (Top Dead Center). The rotor has two
protrusions (180 degrees apart) that, when cou-
pled with the trigger coil, accomplish the signaling.
1. Coil
2. Magnet
3. Rotor protrusion
4. Magnetic field outside of coil
5. Magnetic field crossing coil
6. Current to CDI module
DC-CDI Module
The DC-CDI module receives the input from the
trigger coil and signals the ignition coil when to
fire. It also has the rev limiter function built into its
circuitry, as well as the ignition timing curve. The
DC-CDI module is mounted in the cover of the
conventional electrical box.
Multi-Purpose Electronic Module
(MPEM)
The MPEM has a micro processor inside of its
sealed case and basically is responsible for : inter-
preting information, distribution of information,
and as a timed
/untimed power source. The
MPEM is mounted in the conventional electrical
box. Wire connections are as follows
:
F01H4ZA
3
1
6
2
4
5
WIRE COLOR
FUNCTION
RE/PU
CDI power source from MPEM
through holder relay
BK
Grounded in main electrical box
WH
To ignition coil
YL/WH
Impulse from trigger coil
BK/OR
Blanks-not used at this time
BK/GR
Blanks-not used at this time
BK
Ground between CDI and MPEM
GY/WH
RPM data to MPEM
WH/BL
Data to MPEM (low voltage)
N
S
N
S
A00E4JA
6
3
1
2
1
2
4
5
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