Function

The single spark ignition coil makes it possible: short loading times and thus multiple ignitions. At the moment they are made use of only during idle running. Because it takes its time, it will probably be restricted for low revs. Besides, the number of ignitions clearly depend on the temperature at the moment, the warmer, the more ignitions per time unit. It is not just about sure ignitions in critical conditions. Even if the first ignition is a success, the subsequent ignitions affect the combustion apparently positively.

How it works

In the Bosch FSA figures the primary voltage is determined as usual between 1 and ground. U- multi is the voltage that is measured between 4a and ground. You can see the diagram in figure 3. How is it possible that an ignition operates with a dwell angle of 3 - 4% (!) (see figure 3). At the moment obviously it is only possible if you use single spark ignition coils which probably feature a slightly faster load energy. Another reason for the small dwell angle is recognizable from every last ignition in all three figures. Here the secondary voltage slowly comes to an end, while they are cut off in the first ignitions "by force". A certain rest voltage is left which can be used for the next quick ignition.