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What are Piston Rings?

10/25/2013 9:29:24 AM | by Anonymous

Piston Rings

Piston rings are split rings made of metal that are affixed to an engine’s piston. The piston ring systems in four stroke automobile engines are responsible for sealing the combustion chamber and its contents from the rest of the engine. At the same time, it regulates the oil circulation and consumption. In simpler two stroke engines found on motorcycles and scooters, piston rings do not circulate oil. This is because lubrication is provided by oil mixed directly with the fuel. In both cases, the piston rings play a vital role in ensuring the smooth operation of an engine.


The three main functions of piston rings in the reciprocating engines are firstly to seal the combustion chamber so that there is no transfer of gases from the combustion chamber to the crank. Secondly, it is to support heat transfer from the piston to the cylinder wall. Last but not least, it also helps to regulate the engine oil consumption so that there will be no waste of engine oil.


A series of three rings is used per piston in most four stroke engines. Each piston ring is open ended rather than entirely circling the piston. This is so that it can compress when it is installed in the cylinder to ensure that it is a tight seal. However, not all of the piston rings perform the same function. In the order of top to bottom of a piston head, it comprises of the compression ring, the wiper ring and the oil control ring. Each one of the rings are made out of steel or cast iron. They are all shaped differently and have unique design features to suit their own needs.


The topmost ring known as the compression ring functions mainly as the seal that keeps the fuel air mixture in the combustion chamber from escaping to the other parts of the engine. At the end on, the compression ring can look like a keystrone or a rectangle. In the middle, the wiper ring is designed with a tapered edge angled downwards. This is to help lubricate the cylinder wall and direct excess oil down to the crankcase. Lastly, the oil control ring. The oil control ring is often not just a single ring. It is two thin rails incorporate drilled holes that allow oil to sluice through.


The piston rings are among the most constantly stressed part of an engine that is subjected to wear and tear out of all the parts. The pressure of each ignition must be contained by the rings with an engine’s piston acting as the movable end of the combustion chamber. A piston ring nevertheless is extremely prone to wearing down through normal usage despite the wear resistant coatings and treatments.


Due to the wear and tear of a piston ring, the undesirable behaviour can have an adverse effect on the engine performance. Pressure can build up in the crankcase as the gasoline dilutes the oil due to the segregation of oil and fuel intermixed. Additionally, oil that enters into the combustion chamber can also ignite. This causes the car’s exhaust system to emit blue smoke. At the end of it, piston rings that are worn out can have a negative impact on the engine’s compression. This will result in wasted fuel, decreased horse power and excessive oil consumption. Despite being relatively inexpensive as a product on its own, the labour that is required to replace the piston ring can make it an expensive and time consuming proposition. It is also essential to replace the product as it is necessary for optimal performance to be conducted.

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