Spark Plugs in a Petrol Engine

Spark plugs in a petrol 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. Is it made up as a compact source of ignition. 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- normally made of porcelain and developed to provide mechanical support to the centre electrode while also insulating the electrical current going through the plug, the ribs- these are built in to the insulator used to lengthen the surface between the high voltage terminal and the grounded metal case of the plug itself, the design also helps prevent electrical energy from leaking along the insulator surface, the insulator tip- this is the part of the plug that protrudes into the combustion chamber, this is designed to withstand the extreme temperatures while retaining electrical insulation, it also must retain thermal conductivity to do its job properly, the seal- between the ceramic centre and the metal casing this is normally a multi layered braze to stop any leakage, the metal case- also known as the jacket, this is the part of the spark plug that screws into the cylinder head the threads are made of steel and acts as an electrical ground for the plug itself, the centre electrode- the electrode is the working part of any spark plug, it carries current from the ignition wire down the length of the electrode and allows the plug to spark across the gap between the electrode to the ground tab of the casing allowing the ignition of the fuel in the combustion chamber.

In the past years there have been quite a few revisions on the basic spark plug design. Revisions were made in order to provide either better ignition or longer life, in some cases both. Some are physical changes which are apparent when looking at a spark plug, the addition of multiple grounding tips surrounding the centre electrode, the use of a single ground tip with a v shaped notch in it to increase the size of the spark. The multiple ground points normally provide longer life as when the electrodes wear they move to the next closest point, in effect lengthening the life of the plug.

The problem with long life plugs is the design of many modern engines. Many modern engines have cylinder heads made of aluminium. The jacket of a spark plug 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 aluminium cylinder head only to find the threads have actually disintegrated from inside the cylinder head and it is no longer serviceable. This is a case where abiding by the quoted service intervals can actually cost you more time money and hassle. You are far better off replacing the plugs at a minimum of every two years in order to stop a more expensive repair bill later.

Wayne Adams is an expert in Reconditioned Engines. If you are interested in learning more about quality Reconditioning an Engine, please contact us by visiting our main site: Petrol Engines or by calling us at 442085960396