Forgive my ignorance, A/M ignition

[Pete_89T2]

Originally Posted by RETed

Circuit is not as simple as we thought...

Did a quick test of resistance on the terminals.
If the parallel circuit was as simple as above, measuring resistance across the towers should be nil - not the case.
In fact, the towers are isolated from the two coil inputs + and - (no surprise there), and there is no resistance between either tower to coil ground - kind of a surprise.
The coil outputs are isolated from every part of the coil body including from each other.

Twin, independent coil circuits wound within the coil body itself?


-Ted

Ok, now it's starting to make sense. By inference of Ted's measurements, the tower outputs can't be wired in parallel. I can't draw & post the circuit, so hopefully this description will make sense to everyone if you reference NoDOHC's diagram and use your imagination.

If you added a 2nd distinct coil winding to the secondary side of the transformer, and connect one leg from each of these secondary windings to a common ground through a diode (i.e., allows DC to flow in only one direction, connect "-" side of the diode to ground, "+" side to coil winding) and the remaining coil leads become your L1 & L2 tower terminals, Ted's measurements make perfect sense. In effect, we have two secondary coils driven by a common primary coil.

[NoDOHC]

You may not be able to see resistance, a lot of coils are capacitively coupled. It is simplest to observe the direction that the spark takes while cranking.

Originally Posted by Pete_89T2

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.

Actually, you can research the dielectric strength characteristics of air easily. Higher pressure increases the density of the air, which increases the dielectric strength of the air (more molecules to force to ionize).

Breakdown Voltage

Anyway, I am back in town today, maybe I will test this myself tonight.