ventiiliajastust

Ventiiliajastust, commonly translated as valve timing, refers to the precise moments at which the intake and exhaust valves of an internal combustion engine open and close. This timing is critical for the efficient operation of the engine, as it directly influences the flow of the air-fuel mixture into the combustion chamber and the expulsion of exhaust gases. The timing is determined by the camshaft, which is driven by the crankshaft, typically through a timing belt or chain.

The opening and closing of valves do not perfectly coincide with the piston's movement. Intake valves usually open before the piston reaches the top dead center (TDC) on the intake stroke and close after the piston passes the bottom dead center (BDC). This overlap allows for better scavenging of exhaust gases and ensures a more complete filling of the cylinder with the fresh charge. Exhaust valves, on the other hand, tend to open slightly before the piston reaches BDC on the exhaust stroke and close after the piston passes TDC on the subsequent intake stroke.

Modern engines often employ variable valve timing (VVT) systems. These systems can alter the timing of valve opening and closing based on engine speed and load. By adjusting valve timing, VVT can optimize engine performance, fuel efficiency, and emissions across a wider range of operating conditions. This is achieved through mechanisms that can advance or retard the camshaft's position relative to the crankshaft.