Description And Operation

COILS 

Courtesy of CHRYSLER GROUP, LLC

The coils are directly connected to the plugs and are "plug top" type; they are used by the Engine Management Node to supply the spark plugs at high voltages. They are installed directly on the cylinder head cover, and are also used as a lock for the Blow-By cover; they are connected through a highly insulated connection to the spark plugs.

Characteristics and operation 

The coils are made up of a closed magnetic core (double E), formed of a segmented silicon steel pack in the coil head. Electrical windings are wound around the core to form primary and secondary windings.

The windings are housed in a pressed plastic container with the low voltage connector and the fastening bush on the cylinder head; they are insulated through immersion in an epoxy resin which has excellent dielectric, mechanical and also thermal properties, as the coils are exposed to high temperatures. The coil head is connected to the spark plug through a silicon rubber cap containing a spring that transmits the high voltage from the secondary winding to the spark plug terminal.

The coils are directly controlled by the Engine Management Node in a timed, sequential manner.

Power drivers are built into the Engine Management Node.

The Engine Management Node closes the primary winding supply circuit to earth to create a strong magnetic field around the primary winding. When the primary winding circuit is opened, a high voltage is generated by induction in the secondary winding.

This high voltage is discharged to the engine earth through the electrodes of the spark plugs to generate the spark which ignites the air/fuel mixture.