The IGNITION SYSTEM as Influenced by FUEL CHARACTERISTICS 420078
RECENT tests indicate that ignition timing can be used to measure the detonation characteristics of a fuel at various speeds in a multicylinder engine. Present engines usually require a spark to be set below the point of maximum power to avoid objectionable detonation. A more advanced spark timing with a higher octane fuel will give more power where desired.
Unfortunately, the spark-advance requirements with change of speed are not uniform on various commercial fuels from different sources with different processing and blending. Unless a very-high-octane fuel is used, the automatic spark advance on the distributor supplied on the engine may not be equally satisfactory on different fuels. There seems to be no easy or practical way to make possible the adjustment of the ignition timing by the driver to accommodate different fuels now used.
At present it does not seem desirable, from an economic point of view, to increase the accuracy of the ignition distributor if there is much additional cost involved. When fuels become more nearly standardized as to detonation, it may be worthwhile not only to improve the accuracy of the distributor but to change the method by which it is driven by the engine.