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Twin-spark Ignition


Ever since the ignition system has existed, it was also built as a twin-spark system. In the beginning, mostly in racing cars, the ignition system was completely doubled to ensure a greater operational reliability. Nowadays, it's function is different. With the twin-spark, it's possible to influence the combustion process in the cylinder and with it the performance- and particularly the exhaust gas development.


In all cases, the twin-spark requires, at least two spark plugs. In addition, the high tension supply for both. Should one wish to achieve a special amount of operational reliability, then the primary system must still be laid out twice. This was also the case with the first rotary engines. Some of them had two distributors and two spark plugs per chamber. This was due to the elongated combustion chamber in which the mixture was difficult to ignite, because the spark was coming from one particular point. The two distributors had to be adjusted to each have a different ignition timing. With todays electronic ignition, the adjustment would be simpler and would not change, except in the case of a repair. In the above figure, a motorcycle cylinder head is shown. On the right, two smaller inlet valves, and on the left, one larger exhaust valve. The two spark plugs are grouped around this arrangement. The twin spark system mostly requires a longer series of experimentation to determine the ignition timing and where the plugs should be placed. Apparently, in this case, the portion of late burning mixture, or that which is not burned at all, is kept to a minimum. Hot-spots are avoided. A well controlled flame-front mostly allows a higher compression. 11/10