FOUR STROKE ENGINE

A four-stroke engine is an internal combustion engine that completes one power cycle using four distinct movements (strokes) of the piston during two revolutions of the crankshaft. It is widely used in automobiles, trucks, and many other machines due to its efficiency and lower emissions.

The four strokes, often summarized as "suck, squeeze, bang, blow", are as follows: 

Intake (Suction): The piston moves downward from Top Dead Center (TDC) to Bottom Dead Center (BDC), and the intake valve is open. This creates a vacuum, drawing a mixture of air and fuel into the cylinder (or just air in a diesel engine).

Compression: Both the intake and exhaust valves close, and the piston moves upward from BDC to TDC, compressing the air-fuel mixture. Compressing the mixture increases its temperature and pressure, which allows more energy to be released during combustion.

Power (Combustion/Ignition): Just before the piston reaches TDC, a spark plug ignites the compressed mixture in a gasoline engine, or the high heat of compression ignites injected fuel in a diesel engine. The resulting rapid expansion of hot gases forces the piston down from TDC to BDC, which is the stroke that produces mechanical work to turn the crankshaft.

Exhaust: The exhaust valve opens, and the piston moves back up from BDC to TDC, pushing the spent combustion gases out of the cylinder through the exhaust system. Once complete, the exhaust valve closes, the intake valve opens, and the cycle begins again. 

Key components include the Piston which is a moving component within the cylinder that transfers the force of expanding gases to the connecting rod

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The Crankshaft which Converts the linear (up and down) motion of the pistons into rotational motion. The connecting rods which Links the piston to the crankshaft, acting as a lever arm. The Valves (Intake and Exhaust): which are  Mechanically timed components that control the flow of the air/fuel mixture into and exhaust gases out of the cylinder. The Camshaft: which Uses cams to open and close the valves at the appropriate times, synchronized with the crankshaft's rotation. The Spark Plug: which Delivers an electric current to ignite the air-fuel mixture in gasoline engines. And the Flywheel which is a  heavy rotating disk that stores angular momentum from the power stroke to carry the piston through the other three stroke

 

Four-stroke engines are generally more complex and heavier than their two-stroke counterparts but offer superior efficiency and are the industry standard for most modern applications.