Pistons are the components in an engine that slide up and down against the walls of the cylinder and compress the air and fuel inside the cylinder bores. Pistons are one of the most vital aspects of an engine, particularly if it is a high-performance motor. Pistons are manufactured in two different methods, forging and casting.
Most original equipment manufacturer (or OEM) and aftermarket pistons are cast pistons. These are made through a process called "gravity die casting." Put simply, cast pistons are made by pouring melted aluminum and silicon alloy into a mold. The piston is then released from the mold.
Instead of being cast, forged pistons are made from a solid chunk of billet alloy that is then stamped to form the shape of the piston.
Advantages of Forged Pistons
Because the forging process compresses the metal's molecules into a denser area, the main advantage of forged pistons is that they are much stronger than cast pistons, which tend to be brittle. This is why they are developed primarily for high horsepower applications. Companies like BMW, Porsche and Ferrari use forged pistons for their engines, which often put out well over 500 horsepower. This is also the reason that forged pistons are favored by high-performance engine builders.
Disadvantage of Forged Pistons
The single biggest disadvantage of forged pistons for the consumer is the cost. Having a set of forged pistons custom made is quite a bit more expensive than buying mass-produced cast pistons.
Buying Forged Pistons
A variety of forged pistons are available from a number of companies, on the aftermarket and the Internet as well as from high-performance parts companies. (See Resources.)
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