Reference
Modification no.
- 0 -
Page
50
Date
1997 02 01
Main
914 F
01476
9.4.1) Ignition
See Pic. 24.
As already stated the engine is equipped with dual ignition of a breakerless
capacitor discharge design (DCDI). That means that the ignition unit com-
prises two independently working ignition circuits (separate trigger coil,
electronic module, charging coil etc.).
â—† NOTE: The ignition unit is completely free of maintenance and
without any adjustment.
Each ignition circuit consists of two ignition branches. Ignition occurs on
cylinder 1 and 2 simultaneously every 360° as well as on cylinder 3 and 4 but
180° offset.
â—† NOTE: Due to engine design ignition occurs also at overlap T.D.C.,
but this is for engine operation insignificant.
The engine is furnished with an automatic ignition adjustment controlled by
the edge of trigger cams on the flywheel and the electronic modules.
◆ NOTE: For easy engine start the ignition timing at start is 4° B.T.D.C.
for ignition circuit A and B.
As soon as the engine runs the ignition timing will change over automatically
to operation timing of
26° BTDC on ignition circuit A and
22° BTDC for ignition circuit B
The transition from start ignition timing to the timing for operation takes place
between 650 to 1000 rpm.
â—† NOTE: The different ignition timing for the top spark plugs and the
bottom spark plugs take into account the differing ignition
lag resulting in better knock behaviour.
The difference in the ignition timing will be achieved by
different length of the trigger cam Q.
Trigger cam for ignition circuit A (raised position) is approx.
4 mm (.16") longer.
B3/4
A1/2
Pic. 24
1
00135
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