Re: How do Atom Computer Ignition modules work?

[legendre]

quote jnjvan:

But you can have both: You time for optimal spark energy with the points, you time for crank angle by rotating the magneto plate (which moves the coil and the points relative to the crankcase).

This thing about being able to "move the mag plate" is a HUGE red herring. Think about any other engine with dynamically variable timing – be it an automotive system, a motorcycle, or any other system with variable timing.

Just because the operator is able to control the timing (via the engine speed lever) doesn’t account for the upper & lower bounds of the timing range. Again, ignore the fact that the timing may be changed and just think of it as a fixed timing system, with the engine speed lever moved to "FAST" and as such, the throttle wide open. Can we agree that the ignition timing must be as specified in terms of degrees relative to TDC at the full-speed settings? I can guarantee you, it IS.

So then, what timing angle is set by setting the engine speed lever to FAST – if we’ve timed the magneto for maximum energy? Why should it end up at the required angle, for full-speed operation?

If what you’re saying were correct, then there would be no need to time +any+ ignition system with variable advance – either manual, or automatic – for anything other than max spark energy, as the timing would some how be magically correct whenever the engine ran up to full advance.

This concept just isn’t sinking in, is it? If not, let me phrase it this way:

When an OMC engine is set to full speed, and hence full spark advance – what is the more critical factor: That the plug(s) fire at the correct crankshaft angle, relative to TDC – or that the plug(s) fire at the moment of greatest spark energy. Very recently, we all seemed to agree that the former was correct.. Yes?