Variable valve timing

process of altering the timing of a valve lift event

thumb|A Honda K24A Engine with i-VTEC right|thumb|VTEC engaging in the F23A7 Inline-four Variable Valve Timing & Lift Electronic Control (VTEC) is a valve system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine, resulting in higher performance at high rpm, and lower fuel consumption at low rpm. VTEC uses two (or occasionally three) camshaft profiles and hydraulically selects between profiles. It was invented by Honda engineer Ikuo Kajitani. It is distinctly different from standard VVT (variable valve timing) systems which change only the valve

thumb|Cutaway view of Variable Valve Timing with intelligence on a Toyota ZR engine|ZR engine in [[Techniquest Glyndŵr ]]

thumb|right|250px|VANOS units on the intake and exhaust camshafts of a BMW N52 engine VANOS is a variable valve timing system used by BMW on various automotive petrol engines since 1992. The name is an abbreviation of the German words for variable camshaft timing ().

thumb|4B11 MIVEC engine MIVEC (Mitsubishi Innovative Valve timing Electronic Control system) is the brand name of a variable valve timing (VVT) engine technology developed by Mitsubishi Motors. MIVEC, as with other similar systems, varies the timing of the intake and exhaust camshafts which increases the power and torque output over a broad engine speed range while also being able to help spool a turbocharger more quickly and accurately.

motor vehicle engine

thumb|right|Valvetronic system of the BMW N52 engine The Valvetronic system is a BMW variable valve lift system which, in combination with VANOS, allows infinite adjustment of both intake valve timing and lift. The system claims to improve fuel economy and emissions, and negates the need for a throttle body in regular use.

thumb|right|Fiat 875 cc two cylinder TwinAir engine featuring Multiair technology MultiAir or Multiair is a hydraulically actuated variable valve timing (VVT) and variable valve lift (VVL) engine technology enabling "cylinder by cylinder, stroke by stroke" control of intake air directly via a gasoline engine's inlet valves. Developed by Fiat Powertrain Technologies, the technology addresses a primary engine inefficiency: pumping losses caused by restricting intake passage by the throttle plate that regulates air feeding the cylinders.

automobile variable valve timing technology