A spark plug is an electrical component of a spark ignition system used in an internal combustion engine, most commonly a gasoline engine. Spark plugs essentially have two key functions. One is to ignite the air and fuel mixture inside the engine after compression.[1] The other is to transfer heat from the combustion chamber. A spark plug consists of an electrode joined to a heavy insulated wire and then to an ignition coil that acts as a high-voltage transformer.
[edit] How it Works
Spark plugs are situated on top of the cylinder where the air and fuel mixture is compressed. The spark plug tip rests inside the engine recessed into the side of the cylinder wall. The other end of the spark plug remains outside of the engine, affixed to a spark plug wire that connects the distributor to the spark plug.[2]
When the piston descends downwards inside the cylinder after the intake of air, the air and fuel mixture is compressed inside the combustion chamber, at which point the distributor releases a surge of energy along the spark plug wire. This surge of energy eventually reaches the spark plug, causing it to fire up and ignite the air and fuel mixture. An explosion or combustion results, forcing the piston down again. The piston comes up for a second time and pushes the burned off gas created from combustion out an exhaust valve.[3]
Ignition is a rather simple process. The spark plug forces electricity across a gap similar to a lightening bolt. The electricity needs to be high voltage to jump across this gap and produce a good spark. Normally, spark plug voltage is between 40,000 to 100,000 volts.[4]
Spark plugs also comprise an insulated passageway that permits a high voltage charge of electricity to travel down to an electrode. From the electrode, it can travel over the gap, be conducted into the engine block, and afterwards grounded. The spark plug should also withstand intense heat and pressure inside the cylinder. Design of the spark plug is also important, as deposits from fuel additives should not build up on the actual plug.[5]
A ceramic insert is used on a spark plug to isolate the high voltage of electricity at the electrode. This ensures that the electrical charge or spark is only released from the tip of the electrode and not somewhere else on the spark plug. The ceramic insert is also used to burn off deposits.[6]
There are hot spark plugs and cold spark plugs. A hot plug is designed with a ceramic insert that has a smaller contact area that connects to the plug’s metal part. This lessens the transfer of heat from the ceramic, causing it to run hotter and burn away more deposits. Cold plugs have more contact area and this makes them run cooler.[7]
[edit] References
- ↑ Techtips. Ngk Sparkplugs. 2008-09-30.
- ↑ What is a Spark Plug. Wisegeek.com. 2008-09-30.
- ↑ What is a Spark Plug. Wisegeek.com. 2008-09-30.
- ↑ Ignition System. Howstuffworks.com. 2008-09-30.
- ↑ Ignition System. Howstuffworks.com. 2008-09-30.
- ↑ Ignition System. Howstuffworks.com. 2008-09-30.
- ↑ Ignition System. Howstuffworks.com. 2008-09-30.
