Re: How Important is OMC Ignition Timing?

[legendre]

If what you’re saying were correct, then there would be no need for the recently-discussed OMC timing tool.. think about it:

The magneto rotor could be marked with a line at the factory for magnetic dead-center, and a corresponding mark could be placed dead-center on the coil’s pole shoe. Then it would be simply a matter of adjusting the points to open when the two marks came into alignment – as that would be the magnetic dead-center point, hence the AC zero crossing which is the point of maximum primary current and strongest spark.

Absent the factory-made marks, it would be trivial to make your own set of marks using nothing more than a flexible ruler and scratch-awl. Again, it would obsolete the OMC timing tool.

Again, event #1 is a range, not a specific angular position per se. Look at the shape of a sine wave – you can see that it is at or near the point of maximum current for about 22′ of the cycle. Event #2 (the firing of the spark plug) can occur at any point across that range, and have nearly full spark energy. Sure, max current is at the peak, but allowing 11′ either side of peak would give what, about 90-95% of max? That’s perfectly acceptable.

So ask yourself, now, why does that OMC timing tool exist? It exists, because event #1 is taken care of by the design engineers and careful manufacturing, and no normal wear & tear will ever alter the range of event #1. Event #2 however needs to be precisely set – it’s not a range, it’s a fixed angle BTDC at a stated RPM.