A four-cycle engine works with 4 basic steps to a successful rotation of the crankshaft: the intake, compression, power and exhaust stroke. Each engine cylinder has four openings for the intake, exhaust, spark plug and fuel injection. The piston is driven by the engine's crankshaft whereas the intake and exhaust valves are driven by the camshaft. The crankshaft and camshaft are connected by a timing belt/chain to maintain synchronization between them. The various processes comprising the cycles of a four-stroke engine are explained below:
Intake Stroke: The intake stroke is where the intake valves are open and the air is drawn into the cylinder. The fuel injector sprays the fuel into the cylinder to achieve the perfect air-fuel ratio. The downward movement of the piston causes the air and fuel to be sucked into the cylinder.
Compression Stroke: The next is the compression cycle where both the intake and exhaust valves are closed. The upward movement of the piston causes the air-fuel mixture to be compressed upwards towards the spark plug. The compression makes the air-fuel combination volatile for easier ignition.
Combustion/Power Stroke: During the power/combustion stroke, both the intake and exhaust valves are still closed. The spark plug produces a spark to ignite the compressed air-fuel mixture. The resulting energy of the combustion forcefully pushes the piston downward.
Exhaust Stroke: The last cycle is the exhaust stroke, when the exhaust valves open and the exhaust gases are forced up by the returning piston.
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