A valve is a device that controls the flow of a liquid or gas through a pipe or tube. It can allow the substance to pass through or stop the flow completely, like a gate that can be opened or closed. Full definition
The 2001, 2002 and 2003 RAV4 came with the 148 - hp 2.0 - liter 4 - cylinder DOHC engine with Variable Valve Timing with intelligence (VVT - i). (samarins.com)
It has system of variable valve timing on the intake and exhaust. (mywikimotors.com)
The demand for service media (steam, water and ice water) is also calculated, as this substantially influences the choice of valves for steam regulation and ice water feed. (dairyprocessinghandbook.com)