Spark Plug: Description and Operation

Spark Plug Construction:

SPARK PLUG CONSTRUCTION

Spark Plug Temperature:

SPARK PLUG HEAT RANGE

The spark plug provides a path for the high current of the secondary circuit to flow to ground. The only paths for this current are through the ground electrode and center electrode across the spark gap. The spark produced when the current jumps the gap and ignites the air/fuel mixture in the cylinder. The temperature of the spark plug is determined by the length of the insulator and the size of the heat sink area. The longer the insulator is, the smaller the heat sink area will be and this will cause the spark plug to be hotter. The center electrode temperature ranges from a low of 392~F (200~C) at 10 m.p.h. to a high of 1472~F (800~C) at 80 m.p.h..