The Capacitor Discharge Ignition (or CDI) does not charge an ignition coil, rather it uses the 1:100 winding ratio of the coil as a transformer. Initially, the 12 volts of the electrical system is converted to 200-500 volts and stored in a capacitor. When the spark is required, the capacitor is discharged into the ignition coil instantly producing a spark with duration of only 0.1 to 0.3 milliseconds. For many applications this spark duration is not long enough to ensure that the air-fuel mixture ignites completely.
A multiple coil ignition system, like the Electroair EIS solves this problem by using an ignition coil for every pair of companion cylinders. The time available to charge an ignition coil goes up. This allows the full benefit of an inductive charging method to be realized: the coil will apply enough voltage to the spark plug to jump the gap (regardless of cylinder pressure). The rest of the energy in the coil will then be dissipated in the plug as measured by the spark-duration. Depending on the cylinder pressure, the spark duration will be over 2.0 milliseconds. This spark-duration ensures that any air-fuel mixture will burn!