my questions were for the people doing the evaluations and comparisons between CDI and LDI,
the energy in a capacitor is 1/2 C V^2, the energy in an inductor is 1/2 L I^2, these are computable,
measurable, and knowable, but no one seems to be doing it.
You hit the nail on the head in asking for a better understanding of where the energy goes and why does CDI seem to deliver less of it to the spark. I'm in the process of figuring that out in more detail, but I have some thoughts about just what may be going on.
First, the CDI: voltage on a capacitor depends entirely on its charge. To get energy out, you must draw current from it at whatever voltage it happens to have at the moment. Starts high, gets lower as it becomes discharged.
Spark voltage, on the other hand (after the arc has been struck and stabilized) is kind of fixed. In fact, it gets lower when you run more current through it. I'm testing that now, but my early data is showing maybe a mean value of 100 volts at 0.1 amp, down to about 50 volts at 0.5 amps for a CM6 plug with a 0.025 gap.
As you can see, the capacitor energy source and the spark plug energy sink don't match very well. The CDI step-up transformer has to make a high initial voltage to start the spark in the first place, but after it fires, the spark almost shorts out the transformer, so it makes a very short spark. There's likely more voltage drop across the winding resistance than there is across the spark itself.
For the LDI: current and voltage essentially switch roles. During the spark the inductor voltage will be the same as the spark voltage, and the rate of current decay is proportional whatever the voltage happens to be at any given instant. The voltage can be high to start the spark and can be low during the discharge. "Shorting out" the output of an inductor PRESERVES its stored energy rather than dissipating it. Thus, the spark can last as long as it takes to discharge the inductor.
I'm well aware that this explanation glosses over whole lot of important details, but I think this is the basic reason for the CDI/LDI difference.
Don