The Petrol engine

• Four strokes are involved in the operation of most petrol engines
• They are thus known as four-stroke engines
• The first stroke is known as the inlet stroke
• During the inlet stroke the piston moves downwards
• Drawing in air and petrol vapor from the carburetor through the open inlet valve
• The compression stroke 
• During this stroke the piston moves upwards and the all the valves are closed
• This compresses the air and petrol mixture
• The power stroke comes next
• During this phase the gas is ignited by a spark plug
• The gas mixture explodes giving off a lot of heat energy
• This causes a large rise in pressure in the cylinder and the piston is forced downwards
• The last stroke is known as the exhaust stroke
• The piston rises and the exhaust valve opens
• The exhaust gas is pushed out of the cylinder
• The piston is kept moving between power strokes by the flywheel
• A flywheel is a heavy revolving wheel that machine which is used to increase the machine’s momentum
• and they provide greater stability or  reserve of available power in an engine
• The crankshaft connects the movement of the pistons to the driving shaft through a system of gears
• There are at least four cylinders in a motor car
• During every half-revolution of the crankshaft the cylinders “fire” in turn
• This results in a much smoother running operation and evens out the distribution of power
• Lubrication of the engine results in higher speed in the pistons
• Oil is ed under pressure into the moving parts

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