Parse variable valve technology

Japan's Honda's variable cam variable valve technology pioneer, published his famous VTEC (Valve Timing Electronic Control = electronically controlled valve timing technology) in the late 1980s. Configuration in the Civic, CRX and NS-X first, then gradually become the standard configuration of most models.
In the figure we can see that there are two groups have different shape of the cam to achieve a different valve timing and lift. Wherein one works in the normal speed condition, i.e. daily use of 4500rpm. Another group at high speed replacement actuator. Obviously, this design does not continuously variable valve timing in 4500rpm VTEC engine (high-speed cam open speed due to the different models and engine models vary) performance fairly mild, but once over 4500rpm switch to high-speed cam (commonly known as "open-TEC"), the performance of the engine will be like a beast-like power of emotion.
The system can indeed improve peak horsepower, the engine can easily climbed close to 8,000 rpm (the engine on the S2000 even can reach 9,000 rpm), like a fitted athletic camshaft, allows a 1.6 upgrade other engine horsepower to enhance the rate reached 30 huge! ! However, we want to take full advantage of this powerful force, the engine speed must be maintained above the point of the open-TEC ", so you need to frequently shift. In addition, the low-speed region horsepower performance is not so can make people impressed, because the low-speed cam must scratch work to 4500rpm, driving pleasure unsatisfactory. Overall, variable cam technology is very suitable with the sports car.Basic schematic variable cam variable valve technology
Honda has some engine models, the 2-stage VTEC improved 3-stage VTEC. Of course, the higher the number of segments, and its performance is more perfect. It is always, however, can only be provided with respect to the other continuously variable valve technology is not very broad torque band. However, since the other of the VVT ​​system does not change the valve lift, variable cam system is still the most powerful of the VVT ​​system.
Advantages:
The rear section of the engine is more powerful, suitable for high-speed orientation engine
Shortcoming
Only 2-3 variable, non-continuous variable; limited improvement in torque distribution; complex structure
Similar principles of technology:
Honda VTEC, Mitsubitshi MIVEC, Nissan Neo VVL