Multi-spark for Electronic Ignition

Posted on Sep 25, 2012

Multi-spark ignition is very useful especially in the case of startings at low temperature and at low rpm range. Basic idea, is to apply to spark plugs instead of only one spark, a spark-burst” having big energy. In this case, combustion of air/fuel mixture is much better and the emissions are more reduced. In addition, through burning improvement, the consumption of fuel can be reduced.

Multi-spark for Electronic Ignition
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Special literature abounds in multi-spark EID schematics. These have in common the fact, as the breaker-points don’t control directly EID, but an oscillator, which will generate a succession of impulses, and these impulses shall command EID. This aproach has two major deficiencies: 1. First spark doesn’t match exactly with the moment of breaking points; so, it has an aleatory delay toward this. This is equivalent to an aleatory modification of ignition advance, which will leads to non-uniform run of engine. 2. At high rpm range, the time between two impulses of multi-spark device can become comparable with the time between breaker-points impulses; this shall lead to an unstable operation of engine, with trepidations and knockings. To avoid this trouble, is necessary to switch-off the multi-spark device when rpm of engine exceeds a certain value. With these in mind, I imagined the device described forwards. Shaping block has the role to provide fixed length impulses (2 mS) at each breaker-points opening. In this way are eliminated the false impulses which appear due contacts vibrations. In multi-spark module, during 2 mS interval, a sequence timer (a counter with decoded outputs) accomplishes the initialization of circuits (full operations will be detailed later). When impulse BP disappears, the gate P2 is opened and the counter N1 receives impulses with 1 mS period, from clock generator. This 8 bits counter measures,...

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