Variable Valve Timing And Lift Electronic Control Pdf

variable valve timing and lift electronic control pdf

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In internal combustion engines , variable valve timing VVT is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with variable valve lift systems. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. Increasingly strict emissions regulations are causing [ citation needed ] many automotive manufacturers to use VVT systems. Two-stroke engines use a power valve system to get similar results to VVT. The valves within an internal combustion engine are used to control the flow of the intake and exhaust gases into and out of the combustion chamber. The timing, duration and lift of these valve events has a significant impact on engine performance.

Variable valve lift VVL is an automotive piston engine technology which varies the height a valve opens in order to improve performance, fuel economy or emissions. There are two main types of VVL: discrete, which employs fixed valve lift amounts, and continuous, which is able to vary the amount of lift. Continuous valve lift systems typically allow for the elimination of the throttle valve. When used in conjunction with variable valve timing VVT , variable valve lift can potentially offer infinite control over the intake and exhaust valve timing. In Porsche made application for a German patent, also applied for and published as British Patent GB in The Porsche patent used an oscillating cam to increase the valve lift and duration.


VTEC variable valve timing and electronic control lift system developed by honda. It was invented by honda engineer ikuo kajitani. It improves the volumetric efficiency of 4 stroke diesel engine. It improves the volumetric efficiency of the engine by providing excess amount of air fuel in to engine at high speed. By regulating valve opening to match engine speed, theVTEC engine adjusts its characteristics to realize both superior power and low fuel consumption Cleaner emission.

Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. A variety of two-stage, or discrete, variable valve lift DVVL and continuously variable valve lift CVVL systems have recently been incorporated in production vehicles. Several systems that have been introduced with the objective of reducing fuel consumption are described in this Appendix. CPS provides a means of switching the actuation of the intake valves between a standard high lift cam for maximum power operation and a low lift cam for efficient light load operation. The low lift cam for light load operation reduces fuel consumption by transferring air flow control from the throttle to the intake valves which results in reduced pumping losses. The incorporation of the CPS concept in numerous production applications is described in the following sections.

engine called the variable valve timing and lift electronic control (VTEC) system [​10,19,54]. VTEC uses two (or occasionally three) intake.

Variable valve timing

Engine development today necessitates both better fuel economy and advanced vehicle performance. Modern engines must also meet the social requirements of natural resource conservation and environment preservation. In , Toyota introduced the WT mechanism on its 4A-GE sports engines in order to increase engine torque and output. WT enables the intake valve to open and close in two steps, based on engine operating conditions.

Variable valve timing


Amelio S.


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