Construction of a Spark Plug

A Proven Principle with a Special Design
The principle of a spark plug is ingenuously simple and simply ingenious. A conductor insulated from the engine block conducts a high-voltage pulse of electricity to an electrode, which causes a spark to jump the gap to a ground electrode. This spark ignites the mixture of fuel and air.

The spark plug's design, the materials used, and the manufacturing process all determine which demands the spark plug can meet.


1) Sharp-Edged Ribs on the Insulator Tip
To prevent ignition misfires, the ribs function as a fivefold (!) barrier against current leakage.

2) Insulator
Consists predominantly of aluminum oxide. Its job is to insulate the connecting bolt and central electrode from the jacket.

3) Terminal Stud
In Bosch's Super spark plugs, the terminal stud is made of steel.

4) Flange Ring
Serves to secure and seal the insulator..

5) Jacket
Made of steel and surface-treated to protect against corrosion. Helps connect the spark plug to the cylinder head.

6) Glass Seal
Conducts electricity and thermal energy. Connects the terminal stud to the central electrode.

7) Sealing Ring
Secures and seals the insulator.

8) Central Electrode
Consists of a nickel-chrome alloy with a copper core.

9) Ground electrode
Positioning, number and geometry have an influence on the sparking process and service life.