VTEC

VTEC, short for Variable Valve Timing and Lift Electronic Control, is a valve actuation system developed by Honda for four-stroke internal combustion engines. In its basic form a locking rocker arm lets the same valves follow either a mild cam profile, chosen for low-speed economy and smooth running, or a taller and longer-lasting profile that gives more power at high revolutions. The engine control unit decides when to switch by reading oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Honda introduced the DOHC form in Japan in 1989 on the Integra XSi with the B16A engine, and later developed SOHC VTEC, VTEC-E, three-stage VTEC and i-VTEC, which adds continuously variable intake cam phasing. Honda engineer Ikuo Kajitani is credited with inventing it.