I usually agree with most everything you state Supercuda.
My opinion here, is there is no need to limit anything to the coil, or we'd be building better coils.
These high energy ignitions are high energy because we are putting more in, and getting more out. That's all.
I used to teach electronics, real electronics. Magnetism, transformer action, induction are just some fascinating topics.
Off topic, but part of magnetism, "is aluminum affected by magnetism?" Yes, its repelled. EVERYTHING is affected by magnetism.
And its magnetism that makes a coil work. That concludes todays topics for me.
More specifically, the collapse of the magnetic field is what makes the spark. But the point is if you want a specific output voltage from a transformer you have a couple ways to do it. Overdrive an existing transformer by pumping up the input voltage, like a CD setup, or rewind the transformer to increase
the secondary ratio. One of them increases the voltage in, the other the current. You have to balance the current thru the system and it's cheaper to just use a ballast resistor than it is to use more copper in a coil. We aren't limited to cost considerations and until it became more expensive to not have a high power ignition system the OEM's didn't change what worked, for certain values of work. Emissions got tighter and then things didn't work anymore.
Oh, what causes ringing isn't "left over energy". In electrical circuits, ringing is an unwanted oscillation of a voltage or current. It happens when an electrical pulse causes the parasitic capacitances and inductances in the circuit (i.e. those that are not part of the design, but just by-products of the materials used to construct the circuit) to resonate at their characteristic frequency.
