The quicker on/off of the ignition module won't effect how quickly the secondary coil discharges.
Basically since the coil stores current, the resistance in the secondary circuit slows the discharge of the coil.
So, the theory is that if you have excess voltage, you can trade that for extended spark time duration, which would involve more of the combustion chamber charge leading to a more complete combustion event. The final impedance of the coil output loop effects the pulse peak and duration.
So, you're saying that the discharge duration CAN'T be changed, meaning the spark duration can't be changed, outside of having too little charge at the end of the discharge to bridge the gap, which would shorten spark time (though not discharge time). TT's post you quoted, however, appears to say something slightly different.
.........the way I understand it.........a coil can't really be designed with a set discharge time, unless (to some degree) the ignition is designed around the specific coil performance characteristics.
Pinhead states that the secondary coil controls the duration of the discharge, which means the coil IS designed with a set discharge duration, give or take some percentage reliant upon the amount of charge that's built up.
All of this, however, points to the idea that no, you cannot use an ignition to both increase output voltage and shorten spark duration on a coil with a fixed duration discharge simultaneously.
It's very possible I'm missing some important attribute of the coils which DOES make this possible (that is, making longer spark with more voltage, shorter spark with more voltage, and shorter spark with less voltage) on the same coil that has a 'fixed' discharge duration, but so far, no one has told me what this is.
Still waiting. Again, not saying it isn't possible. Just no one has told me how it is possible.
I was saying the discharge time isn't really effected by the "quickness" of the shut-off on the primary, other than causing the voltage to more quickly rise and to more quickly initiate the spark. I don't believe the duration spark, itself, can be appreciably extended by changing the method of switching the primary. Spark duration and discharge time
can be extended by tuning the output loop of the coil, however.
The coil has a set maximum potential voltage before the secondary coil starts shunting voltage between the windings. This is where coils get their 30,000 and up voltage rating.
However, in operation, the output voltage is determined by the plug gap and cylinder conditions. Once a high enough voltage is reached to start the actual spark, voltage no longer rises (except maybe a small amount).
From what I've read this is typically around 5,000 volts.
When Twotired was speaking of "excess voltage" I believe he meant excess voltage potential i.e. the potential of the coils.
BUT that doesn't mean you can open your gaps by 6x the factory recommended setting based on the coil's "available" voltage... Because in order to light the mixture you need spark
power which requires voltage, current, and time. Increasing the first two or reducing time will increase power which means going resistorless will increase the instantaneous power output.
However, the mixture doesn't
instantly burn, so a longer spark discharge (as long as it still contains sufficient power) will more effectively ignite the mixture.
Choosing the secondary resistance is a balancing act between spark discharge power and time in order to match in-cylinder conditions, trying to create an optimized spark characteristic in order to most effectively ignite the mixture.
