Pencil coils are used in vehicles with a fully electronic ignition. They
are attached directly to the spark plug. With this coil type the
high-voltage pulse is generated directly at the spark plug. The
advantage: There is essentially no cable loss.
In addition, this compact design provides for valuable additional space - which is particularly important in modern engines - since the spark plug shaft and ignition coil would otherwise take up this essential space.
Due to its installation position directly in the cylinder head, however, this ignition coil type is subjected to higher thermal loads and often subjected to more vibrations.