Introduction to Four-Stroke Engines

Four-stroke engines power most cars and small planes. They convert chemical energy into mechanical motion through intake, compression, power, and exhaust strokes, occurring over two crankshaft revolutions per cycle.

During the intake stroke, the piston descends, creating a vacuum that draws in air-fuel mixture through the open intake valve. This stroke's efficiency is enhanced by advanced variable valve timing technology.

As the piston rises, the intake valve closes, compressing the air-fuel mix. Compression ratio optimization is a balancing act for efficiency and power, impacting the engine's thermal efficiency significantly.

The spark plug ignites the compressed mixture, pushing the piston down. Direct injection and turbocharging have revolutionized this stroke by improving power output and reducing emissions.

Post-power stroke, the exhaust valve opens for waste expulsion. Modern engines employ exhaust after-treatment systems like catalytic converters and particulate filters to minimize environmental impact.

Engine smoothness is paramount. Engineers use counterweights, balance shafts, and harmonics analysis to mitigate vibrations, promoting a smoother operation and longevity of the engine components.

Recent developments include variable compression engines and homogeneous charge compression ignition (HCCI), which promise to enhance fuel efficiency and lower emissions, paving the way for cleaner, more efficient future propulsion.