Spark plugs in a gasoline engine
A spark plug is used in internal combustion engines to create a spark in the cylinder and ignite the fuel in the combustion chamber allowing the engine to rotate. The common spark plug has come a long way in development over the years.
The basic operation of a spark plug is very simple. It is composed as a compact ignition source. The individual components are as follows:
the terminal or tip: this is the part of the spark plug that the ignition wires or coils make contact with,
the insulator, usually made of porcelain and developed to provide mechanical support to the center electrode, while isolating the electrical current flowing through the plug,
the ribs: these are built into the insulator which is used to lengthen the area between the high voltage terminal and the grounded metal box of the plug, the design also helps prevent electrical power from leaking along the surface of the insulation,
the tip of the insulator- this is the part of the plug that sticks out into the combustion chamber, this is designed to withstand extreme temperatures while retaining electrical insulation, it must also retain thermal conductivity to do its job properly,
the seal: between the ceramic center and the metal shell, this is normally a multi-layer weld to stop any leaks, the metal shell, also known as the jacket, this is the part of the spark plug that screws into the cylinder head of the cylinder, the threads are made of steel and acts as a ground connection for the plug itself,
The Center Electrode – The electrode is the working part of any spark plug, it carries current from the ignition wire along the electrode and allows the spark plug to spark through the gap between the electrode and the housing ground lug , allowing ignition. fuel in the combustion chamber.
In recent years there have been quite a few revisions to the basic design of the spark plugs. Revisions were made to provide better ignition or longer service life, in some cases both. Some are physical changes that are apparent when looking at a spark plug, the addition of multiple ground leads that surround the center electrode, the use of a single ground lead with an av-shaped notch to increase spark size. Multiple ground points typically provide longer life, as when the electrodes wear out, they move to the next closest point, effectively lengthening the life of the plug.
The problem with long-life spark plugs is the design of many modern engines. Many modern engines have aluminum cylinder heads. A spark plug shell is made of steel, over time the two different metals create a form of galvanic corrosion in which both types of metal corrode together. It is not uncommon to remove a spark plug from an aluminum cylinder head only to find that the threads have disintegrated from inside the cylinder head and can no longer be repaired. This is a case where meeting quoted service intervals can actually cost you more time, money, and hassle. It is much better to replace the plugs at least every two years to avoid a more expensive repair bill later.