Why do manufacturers always brag about the open circuit voltage capabilities of their coils? Once a clean, properly gapped spark plug ionizes the gap at around 8K-10K volts, it's impossible for the coil to build up any more voltage- - - - -whether its open-circuit capability is 20KV or 500KV. The current flow across the plug gap remains constant, and the induced voltage in the coil secondary winding CANNOT rise above the point where the spark begins to flow across the gap.
Jerry
