What is the state of the intake and exhaust valves during the power stroke of a four-stroke engine?

[StElisa]

During the power stroke of a four-stroke engine, both the intake and exhaust valves are in the closed state. Function of valves: The valves are specifically responsible for introducing air into the engine and expelling the exhaust gases after combustion. Structurally, they are divided into intake valves and exhaust valves. The intake valve's role is to draw air into the engine to mix with fuel for combustion; the exhaust valve's role is to expel the burned exhaust gases and dissipate heat. Current development of valves: To improve intake and exhaust efficiency, multi-valve technology is now commonly used. A typical configuration is four valves per cylinder (though designs with three or five valves per cylinder also exist), totaling 16 valves for a four-cylinder engine. The notation "16V" often seen in automotive specifications indicates that the engine has 16 valves in total. This multi-valve structure facilitates the formation of a compact combustion chamber, with the fuel injector positioned centrally. This allows the air-fuel mixture to burn more rapidly and uniformly, while the weight and lift of each valve are appropriately reduced, enabling faster opening and closing speeds of the valves.