Sometimes the ignition system is improved by installing a transistor circuit. The interrupter contacts remain, they must however, only handle a small amount of controlling current. The lion's share of the work is now done by the transistor. The contacts last much longer and the ignition, together with the dwell-angle, must no longer be adjusted.
The target was of course, the contact-free ignition system and this came out shortly afterwards, there were two types, one with an inductive pick-up and one with a Hall-effect generator. Now the system was, apart from changing the spark plugs, practically maintenace free. Indeed, there were still the centrifugal force- and vacuum adjustment, not really the best solution for operation very close to the pinking limit. A control device was given the task of calculating this data.
These devices were among the first sensors in the motor vehicle, e.g., one on a punched out metal plate on the flywheel and at least one for the temperature of the coolant. In carburettor engines the load signal was picked up by a pressure sensor on the inlet manifold and in petrol injection engines through the position or the change of position of the gas pedal. Only the mechanical high tension distribution remained, e.g., through the distributor finger at the camshaft ends.
They disappeared again very quickly after the appearance of the single- and twin-spark coils. Thus, any form of mechanical wear and tear was removed from the ignition system. In the beginning so-called maps determined and held ready all the, through the sensors detectable values, for the dwell- and ignition angle. In the factory, after extensive trial runs, the values were determined and entered. On certain connector contacts one could even switch over from a map for regular- to one for premium petrol.
These so-called intelligent ignition systems were soon a thing of the past, because now there were pinking sensors, which could differentiate between normal- and pinking combustion. The system could now react in a flash, the ignition for the endangered cylinders could be retarded. Vice versa, one could also operate very close to the pinking limit, which brought about advantages for the consumption and the performance.
Alone the possible reaction to the engine temperature, compared with the old mechanical system, brings an unbelievable advantage. Now, when the engine is cold, the ignition can be advanced 40 degrees or more, without having to worry about pinking. The ageing of an engine is also taken into consideration, previously these were all problems, for which one had to keep a safe distance away from the pinking limit for the entire life of the engine. 05/12