In internal combustion engines, variable valve timing is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. In internal combustion engines, variable valve timing (VVT) is the process of altering the timing. VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing technology developed by Toyota. Variable valve lift is used to enhance performance depending on the RPM and load, while. [HINDI] VVT System : Variable Valve Timing | Working Animation | Meaning.