INTERNAL COMBUSTION ENGINE

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A car engine looks like a large block of metal. And it is. It is a large block of cast iron. In this block there are round holes. These holes are the cylinders. The cylinder block of a car usually has four or six cylinders. In the cylinder the power of petrol is controlled. In each cylinder there is a piston. It can move up and down inside the cylinder. Its shape is like the bottom half of a bottle. It has cast iron rings round it. These piston rings help it to fit tightly inside the cylinder. A connecting rod comes from inside the piston. The top of each cylinder is covered. There are three holes in the top. Two are for valves which open and shut. These are the inlet valve and the exhaust valve. The other hole is for the sparking plug. The sparking plug ignites (fires) the mixture of air and petrol by means of a spark and causes it to explode.

When the inlet valve opens, a mixture of air and petrol is sucked into the cylinder.

The mixture fills the space above the pistons. When the inlet valve is open the exhaust valve is closed.

Smoke and gases remain after the explosion of the petrol and air mixture. When the exhaust valve opens, the smoke and gases are pushed out of the cylinder.

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