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What is a Piston?

11 September 2015, 10:05

What is a Piston?
The piston is an essential part of the internal combustion engine which is key in converting the fuel which you use to fill up your car into energy to drive the car forward.

It is a moving component which is used to transfer the force from the gas which expands in the cylinders to the crankshaft to turn the wheels.

They are needed to convert the linear motion in the cylinders to a circular motion which can power the wheels.

Combustion Engine



The internal combustion engine in your car derives its energy by burning petrol or diesel. The gases which are produced by burning fuel at high temperatures are used to drive the pistons and subsequently transfer energy to turn the wheels of your vehicle.

The piston is essentially a thick metal plate which compresses gas inside the cylinders.

The plate has the same diameter as the width of the cylinders so that no air or fuel can escape round the sides.

It completes a cycle, starting at the top of the cylinder as a valve is opened to fill the cylinder with air and fuel.

The piston is then forced downwards to compress the mixture of air and fuel. It is important to compress the mixture before it is ignited as this gives the explosion more power and makes a more efficient use of fuel.

The spark plug then creates a spark in order to ignite the fuel and cause an explosion. The force from the explosion moves the piston and the exhaust valve is opened to allow the burnt fuel and fumes to leave the cylinder.

As the piston moves up and down, the top of the connecting rod moves up and down too. The bottom of the connecting rod is not fixed in position which allows it to move in a circular motion, rather than a linear one. This circular motion is what will be used to turn the wheels.

This process is repeated over and over again at high speed throughout the whole time that your engine is switched on.

Precision and raw energy



It is therefore easy to see how the piston is absolutely vital to the inner workings of your vehicle. Without the piston, there would be no way to turn the raw energy contained in petrol or diesel into a force which is able to turn the wheels and drive your vehicle forward.

All about the engine/motor



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