Hotter spark does not make more power. However, doing other things to the engine may require hotter spark to enable that power increase.
For example, higher cylinder pressure requires higher voltage to create the arc across the electrodes.
So, high performance engines often require a spark improvement. But, spark improvement is not going to make an ordinary engine produce more power just from the added spark energy.
Here's a crude calculation:
1 horsepower hour = 745.699 861 11 watt hour
Let's say we make our engine output 50hp. This converts to 37250 watt hours.
The ignition system, regardless of the output voltage, is current limited to a percentage of what the primary of the coil draws from the electrical system.
Two 5 ohm coils draw 67 watts, (in one hour it uses 67 watt hours).
Two 3 ohm coils draw 112 watts, (in one hour it uses 112 watt hours).
Even if we assume that the coil energy conversion is 100%, and that 100% of the coil energy is transferred into the engines output (it is certainly not in either case)
67 watt hours = 0.089 848 481 265 horsepower hour
112 watt hours = 0.150 194 476 14 horsepower hour
These are small numbers to start with, and the differences between them are even smaller. I don't think even the most calibrated butt dyno will feel an added boost from high output ignition systems as the sole variable.
I admit that there are other (valid) reasons to improve an ignition system besides a desired HP boost. But, those goals need identification before a cost/benefit analysis can be reasoned.
IMO, of course.
