Hi Jim,
cool that we are starting a more technical discussion here...
there are a couple of things that I alsways wanted to know...
first off all I thought that modern high voltage transformers NEED the additional resistance on the spark plug wire... otherwise the voltage would not reach high enough values
secondly. as far as I understand this.... before the spark the transformer generates a (for arguments sake) 15kV voltage pulse. This voltage pulse travels along the spark plug wire to the spark plug where the gap and environmental varibale determine the spark voltage.. lets say 10kV. As soon as the spark voltage is reached a spark occours. The duration is depending on how long the rotor closes the contact (and how much energy there is to keep the current up to create this amount of voltage).
Lets say that the spark would stay until it is interupted by the moving rotor:
a) low impendance cable (copper wire)
b) high impendance cable
on a.. there would not be any voltage bouncing forward and backward (the 5kV "leftover" voltage") since the resistance is so low that there is (practically speaking) no voltage difference beween the input and output of the wire. The only voltage leftover is based on the capacity of that cable...... which is very minimal... HOWEVER there is a current bounce that induces a high energy pulse(es) into the system........
Additionally, the low impendance calbe causes an excessive current flow (limited only by the transformers impendance)... espscially because we are talking about pulses that will cuase most of the RF noise induced by the ignition transformer. ..... consider that the transformer will be shorted to ground every time the spark voltage is reached... all the leftover voltage would be abosorbed and converted into heat (and RF noise)....
b) since it is a high impendance cable.. there will be an instand voltage shift as soon as the voltage reaches the spark voltage.....
the 15kV form the transformer will be connected through the rotor.. reach the plug... spark voltage occours... current starts flowing.... the voltage now divides between the source and the wire, substantially limiting the current and load on the ingition transformer.. when the rotor passes.. the left over voltage in the cable has only a very limited energy amount (based on the cables capacity) and will be converted to "heat" very fast
Oh yeah.. I really hate the sales pitch that one needs a high performance ingition system to produce higher voltage sparks
however the spark itslef could very well be different (looking at a square angle current wave form) ..the performance ignition system might provide a higher energy level that under certain circumstances increases the spark duration.... ????
Cheers, Mike