[Dynomite]

Originally Posted by Franke

I think the story goes that the cylinder under compression would fire and the other one would be wasted spark. Yes - No?

Paul wrote a good description...of waste spark.

Originally Posted by Paul Workman

It's called a "waste spark" system. Cylinders are twinned, but only one at a time is in compression cycle when the spark arrives.

Just a point of interest: Because current flows in a loop through the block, coil and plug wires/plugs, the current is the same through both spark gaps. However, due to the much higher compression air pressure in the cylinder about to fire, the gap resistance to flow is much higher, resulting in the heat generated in the spark to be proportionately higher than that in the waste spark cylinder. In other words, the majority of the energy expended in the circuit is concentrated in the compression cylinder, resulting in very little actual "waste", really.

FWIW,

P.