Pistons are vital components in a vehicle's internal combustion engine. There is one piston inside each engine cylinder, so cars usually have four, six, or eight, depending on the engine size. Modern factory-fitted pistons are strong, and some are forged to withstand higher operating temperatures, so piston failure is not very common. However, if a failure does occur, motorists must decide whether to replace worn pistons with original equipment manufacturer (OEM) components, or third-party aftermarket components.
What pistons do
All cars, trucks, and motorbikes are powered by four-stroke engines. In this type of engine, the piston makes four separate strokes in a single cycle, including intake, compression, power, and exhaust. Each stroke is the travel of the piston in the cylinder. Two of the strokes move the piston down, and two of the strokes move the piston up.
The four-stroke cycle
The cycle of the engine begins with the intake stroke, where the piston descends to increase volume in the cylinder. The fuel and air mixture enters the cylinder at this point. In the compression stroke, the cylinder travels up, compressing the fuel and air in the cylinder head. A spark from the spark plug ignites the mixture, and the resulting pressure forces the piston down. Finally, the piston moves up once more, venting the exhaust left over from the explosion.
Strong hypereutectic alloys and anti-scuff coatings aid in the prevention of piston damage, allowing them to operate for longer and at higher temperatures. However, excessive heat, abrasions, insufficient oil, and general wear from use may harm the pistons. Symptoms of piston failure include engine noise, oil burning, misfiring, and a loss of power. A drop in compression below 100 psi per cylinder also indicates a problem.
OEM pistons vs. aftermarket pistons
When replacing pistons, motorists have two options. OEM pistons are available directly from a dealership, while aftermarket pistons are available from a variety of third-party companies.
OEM pistons match the ones fitted by the vehicle manufacturer, allowing a motorist to restore a vehicle to the condition it was in when it rolled off the production line. This is an assurance of quality, and ensures the pistons fit without requiring any modifications.
Aftermarket pistons are generally less expensive than OEM pistons. Manufacturers are in direct competition and must price their goods accordingly to attract customers. Furthermore, there is plenty of variety, so motorists have an opportunity to tailor their vehicle to their personal requirements. It is possible to find aftermarket pistons that match or exceed the quality of the OEM equivalent, although motorists must research their purchases carefully, and seek out the best brands.
One of the main advantages of purchasing aftermarket vehicle parts is the additional choice consumers get. For example, consumers may wish to choose cast pistons or forged pistons.
Cast pistons are created by a method called gravity die casting, which involves pouring melted metal into a mould. This is a cost-effective way to make components on a large scale, and results in a final product that is more affordable. However, these pistons can be weaker than alternative types, and they are heavy as the manufacturers make them thick to add strength.
Forged pistons are performance components that are mechanically shaped by hammering rolled metal into moulds. This forces the grains of the alloy together for a stronger and more expensive product than a cast piston. Consumers have the opportunity to order custom forged pistons from manufacturers, which is not possible with cast pistons where the production scale is much larger. Forged pistons are often used for racing vehicles due to their ability to withstand high heat and higher RPMs.
Hypereutectic pistons are composed of aluminium with a quantity of silicon. The pistons are hard and less susceptible to scuffing, and the silicon acts as an insulator, allowing the pistons to operate at high temperatures.
How to buy pistons on eBay
Sellers on eBay offer a wide selection of vehicle parts, including OEM and aftermarket pistons for all model engines. It is easy to find the spare parts and replacement components for the make and model of your vehicle by using the search function available on every eBay page. Simply enter a search criterion, such as "Ford engine OEM piston", to get a comprehensive list of related lots. You can use filters to refine the results list, and arrange the results by price or closing time for easier viewing.