To improve engine economy and power performance, valve timing has different effects at high and low RPMs:
At high RPMs, intake inertia can be utilized to increase intake volume and scavenging efficiency, thus early valve opening and late closing is a common technique. However, at low RPMs, valve timing needs to be adjusted to achieve optimal performance. Therefore, modern engines typically employ variable valve timing technology to automatically adjust valve opening and closing times according to different RPMs and load conditions, thereby improving engine performance and fuel economy.
