A hydraulic valve is a device that controls the flow of liquid in a hydraulic system. It opens or closes to regulate the movement of fluid, allowing it to go through pipes and tubes to power various machinery or equipment. Full definition
The valves are controlled by means of cam followers and feature maintenance - free, hydraulic valve clearance compensation. (topspeed.com)
It is a development of the engine used in the 911 R and GT3 RS, with an upgraded valve train, a stiffer crank, low - friction cylinder liners, a new cylinder head design that dispenses with hydraulic valve adjusters and a 9000rpm redline - 750rpm more than the RS. (autocar.co.uk)
[5] MiTo got new electro - hydraulic valve control system Multiair engines from September 2009. (en.wikipedia.org)