Magneto or Coil Ignition for Motor-Cars

Abstract

F. R. HAIGH has recently compared the relative advantages of magneto and coil ignition used for generating the explosions which occur in motor-car engines (Students' Quart. J. Inst. Elec. Eng., Dec.). Coil ignition was prominent on the early types of petrol engines, but magnetos appeared on the market and for a number of years prior to 1914 a Bosch magneto was regarded as the acme of perfection. About ten years ago coil ignition systems came to the front. The magneto is of great importance in aero work and is popular on racing-cars, but in motor-vehicles it has been almost entirely replaced by coil ignition. Modern coil ignition systems are very trustworthy. The causes of the failure of the ignition system are almost always due to battery and wiring faults; they are very rarely due to the ignition apparatus itself. The contact breaker, coil and ignition switch are generally mounted at different points and thus their action is dependent on the soundness of the wiring between them. Loss of magnetism which used to cause trouble with magnetos is absent in coil systems. Ease in starting up an engine is a prominent feature in coil ignition; at whatever speed the engine is turning, a good spark is always obtained at the plug points. The contact breaker is usually the first component to be examined following an ignition failure, and hence its accessibility and ease of adjustment are of great importance. In this respect, coil ignition has nearly always the advantage. A clear view of magneto contact breakers can rarely be attained without the aid of a mirror. Coil ignition is also greatly superior to the magneto so far as the rapid replacement of faulty parts is concerned.