Ignition system requirements and their application to the design of capacitor discharge ignition systems.

Abstract

Kettering ignition systems used on the majority of automotive engines can no longer assure reliable ignition for high-output engines. The capacitor discharge ignition, CDI, is a promising system to supersede the obsolete battery-coil. This study examines wave-front requirements at the spark plug for producing ignition in the internal combustion engine and system characteristics necessary for producing the wave-front. Arc requirements are described and used to define CDI parameters. A modified Kettering system which violates some basic ignition concepts was replaced by a CDI system designed in this study. Its characteristics were derived from arc requirements, not by aggrandizing the replaced battery-coil parameters. During performance tests, the CDI system exhibited superior performance. It fired simulated fouled plugs and continued to produce an arc when pressurized tx) 3 times the value at which the Kettering ceased to function. This improved performance was accomplished with approximately the same stored energy and less input power.