Re: How Important is OMC Ignition Timing?

[legendre]

quote Archangel:

(…) The trouble is, the TD-20 does not have the OMC universal magneto that everyone else is talking about. He isn’t aware that the universal magneto is a different configuration than the TD-20 and has wrongly assumed that the TD-20 uses the universal magneto. Another instance of model specifics being as — or more — important than general theory.

Thanks for elucidating this point.. I recognized the issue a couple of days ago, and was intending to get around to addressing it. But frankly, the whole debate was getting a little long in the tooth, and I just didn’t have much enthusiasm remaining.

You’re certainly correct that I was using the older, TD-type magneto as my reference.. but sadly, the main contested point(s) still apply to the ‘universal’ magneto. This, despite the fact that the universal is ‘inside-out’ compared to the TD. Here’s what the disagreement boils down to:

– Position #1 (mine) – Ignition timing on any engine is strictly a function of crankshaft angle, usually expressed as a figure of degrees before top dead-center (degrees BTDC). Spark energy remains important, but thanks to careful design & manufacture, the range of sufficient energy is wide enough that a properly-timed ignition event will always fall within an acceptable spark energy range.

– Position #2 (others) – Ignition timing on OMC magnetos +only+ is strictly a function of maximum spark energy, determined by the angular relationship between the rotor magnet(s) and the coil pole shoe(s). Actual spark timing remains important, but thanks to careful design & manufacture, the range of allowable timing is wide enough that a max-energy ignition event will always fall within an acceptable angular range.

Are we at least clear on what is ultimately being contested, here?