The latest and most sophisticated VTEC development is i-VTEC ("intelligent" VTEC), which combines features of all the various previous VTEC systems for even greater power band width and cleaner emissions. With the latest i-VTEC setup, at low rpm the timing of the intake valves is now staggered and their lift is asymmetric, which creates a swirl effect within the combustion chambers. At high rpm, the VTEC transitions as previously into a high-lift, long-duration cam profile.
The i-VTEC system utilizes Honda's proprietary VTEC system and adds VTC (Variable Timing Control), which allows for dynamic/continuous intake valve timing and overlap control. The demanding aspects of fuel economy, ample torque, and clean emissions can all be controlled and provided at a higher level with VTEC (intake valve timing and lift control) and VTC (valve overlap control) combined.
VTEC (standing for Variable valve Timing and lift Electronic Control) does Honda Motor Co., Ltd. develop a system. The principle of the VTEC system is to optimize the amount of air-fuel charge entering, and the amount of exhaust gas leaving, the cylinders over the complete range of engine speed to provide good top-end output together with low and mid-range flexibility.
VTEC system is a simple and fairly elegant method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of only one cam lobe actuating each valve, there are two - one optimized for low RPM smoothness and one to maximize high RPM power output. Switching between the two cam lobes is controlled by the engine's management computer. As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide.As engine RPM increases, a locking pin is pushed by oil pressure to bind the high RPM cam follower for operation. From this point on, the valve opens and closes according to the high-speed profile, which opens the valve further and for a longer time.
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