1965-02-01

Capacitor Discharge Ignition * 650276

This paper describes a new electronic ignition system which provides trouble-free operation, while extending spark plug life to a warranted 50,000 miles or more. Design considerations are discussed that led to the development of a high-voltage capacitor discharge system whose performance justifies its premium cost.
It describes how output voltage, available energy and output voltage rise time (the three major properties that determine overall ignition system performance) are used to establish the design features for new electronic ignition systems. Specific considerations are examined in detail, and appropriate mathematical computations are reviewed; for example, it is shown how energy storage and time constant relationships can be used to derive conditions for achieving ignition at higher engine speeds.
Engineering data, such as spark plug firing voltage as a function of pressure, characteristic response curves based on ignition frequency, and spark plug fouling rate as a function of voltage rise time, are used to compare this new system with conventional ignition systems as well as with transistor ignition designs. Conclusions are drawn that relate the new ignition's performance capability to high reliability applications and extended warranty periods.

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