Forgive my ignorance, A/M ignition

[Pete_89T2]

Originally Posted by NoDOHC

The problem with parallel circuits is that the dielectric strength of the spent chamber (just completing the exhaust stroke) is a lot lower than that of the compressed chamber with air and fuel in it.

What data supports this? If this were true, then the odds of the the stock FC ignition system ever firing the leading plug of the *correct* rotor (i.e., the one with the compressed fuel/air charge) would be slim to none.

Originally Posted by NoDOHC

This means that the spark voltage will build until the field intensity exceeds the breakdown level of the lower dielectric, then that ionized gas in the air gap of the spark plug will short-circuit the coil (spark voltage goes low) while current flows through the air gap. This means that the charged chamber will never get enough voltage to the spark plug to exceed the higher dielectric strength and the charged chamber will never fire.

This explanation is correct, but I suspect you've got the dielectric characteristics reversed - it must be much easier to jump a spark across the gap when the medium is a compressed fuel/air charge than exhaust gases & blowby, assuming the full regime of variables as Mazda designed, otherwise our leading plugs would always misfire.