Ignition

RW,

I think Leo has a 912iS engine so that diagram does not apply.  Still, it is correct that the iS engine does fire both plugs in the cylinder at the same time when both lanes are active, and 1 plug per cylinder when only one lane is active.  

The ignition system description in the 912iS MMH, section 74-00-00 (page 3) is not very well worded.  The term “charging coils” is used and I find that misleading.  There are no specific ignition charging coils, rather energy from the alternators is stored in capacitors in the Fusebox for discharge to the ignition coils.  The system description would be more accurately described by saying  that in normal operation power is supplied to the ignition coils and other engine functions by alternator “A”, and spark timing is controlled by the ECU based on a signal from the crankshaft position sensors.  And, if alternator “A” fails, then alternator “B”  assumes these functions.  

Hi Jeff

You are right, my bad.  I should have looked at the thread top and not made an assumption.  Sorry for the misleading things. 

On the iS engine ignition is is however the same running timing, 26 degrees.  Only the type 915 and 916 have the ability to lower the timing in the event of a knock.  The standard 912iS they do not use the knock sensor.  That said the firing order and the fact that there is a waste spark while running  is still correct.  The timing control is done in the ECU and the power for the spark is managed from the fuse box with command from the ECU.  

Cheers