IGNITION DESIGN TRENDS.

So far, the trend towards breakerless ignition systems has been dictated by a need for greater accuracy of ignition timing, but the timing point is determined on the basis of averaging the conditions and requirements within the engine at each point over its operating range. Currently the aim is to achieve a performance that follows closely the advance curve required relative to crankshaft speed, and to maintain that accuracy throughout the life of the vehicle. Ultimately, however, the aim must be to take additional factors into consideration in specifying the curve. These will include air temperature, coolant temperatures, air pressure, humidity, fuel quality, throttle valve position and rate of change of position, gear in use at the time, and exhaustgas constituents. Also described is the plasma torch ignition system. This comprises essentially a three-electrode plug, a dc/dc converter, a condenser, a conventional coil and a circuit-breaker device. Heat produced by the discharge rapidly increases the pressure of the gas in the plug and this then drives the very hot plasma out, through the orifice formed by the earth electrode, into the combustion chamber. The jet of plasma may be as much as 10 mm long and 2 mm in diameter at its source.