VTEC

Advanced technology Variable Valve Timing and Lift Electronic Controlled (VTEC) Honda innovation results show different mechanisms. The main difference is the inclusion of valve movement. In the 16 valve engine, there is two of each incoming and exhaust valves in each cylinder.
VTEC is applied only on the intake valve. In this valve controlling the efficiency of the engine more powerful. The assumption, the process does not require disposal of the variable valve opening for the more smoothly the exhaust, engine work will be more lightly.
In VTEC engine, the second intake valve does not always move together. For example, at low speed there is only one valve is opened. Opening was also relatively small because the characters are punched camshaft valve is suitable for low speed. This condition is considered fit for the machine. Since at low rpm a lot of unnecessary air supply. In addition, there could be air turbulence to help mix the fuel. Engines so efficient, efficient, environmentally friendly too.
With increasing engine speed, air supply needs are also increasing. Directly answered by the second valve. Larger opening for nok chamshaft have a higher degree of character. Fun, had joined the first valve to open wider. This is because there are pins that connect the rocker arm and push pin. This will automatically lock the second pin rocker arm. Because the second rocker arm which is driven by the camshaft duration nok higher, so follow the movement of the first valve.

In addition there is also VTEC i-VTEC (intelligent VTEC), which also features forward and rewind mechanism of ignition. Certainly the results more leverage to improve engine efficiency.
VTEC: an entirely new approach to engine design
4-stroke engine goes through induction, compression, combustion and exhaust strokes to generate power. Before the advent of VTEC, the valves controlling the intake and exhaust strokes were operated according to fixed rules.

If the intake valves were made to open a relatively small amount to privilege drivability at low engine speeds as used in normal driving conditions, the engine would not be allowed to intake enough air at higher engine speeds, sacrificing outright performance. On the other hand, if the intake valves were made to open wide to privilege breathing at higher engine speeds, performance at low engine speeds would be compromised. This is a dilemma that has plagued engines for over a century.
by Honda’s official website at http://world.honda.com/automobile-technology/VTEC for details.

Optimizing engine breathing: how VTEC works
An elegant, simple mechanism
Switching between high and low valve lift using two cam profiles and two rocker arms per cylinder.
The switch is made using hydraulic pressure to push/release the sliding pin, locking/unlocking the middle rocker arm and the other rocker arm.
At low engine speeds, the pin is retracted, disengaging the middle rocker arm. The valves are operated by the two outside, low-profile cams for a low valve lift.
At higher engine speeds, increased hydraulic pressure pushes the pin, engaging the middle rocker arm. The valves are operated by the middle, high profile cam for high valve lift. by Honda’s official website at http://world.honda.com/automobile-technology/VTEC for details

VTEC Cylinder Cut-off System

When the throttle is open during acceleration or cruising, the valve lift-mode rocker arm and the idle-mode rocker arm are engaged via a synchronizing piston. During deceleration, as soon as the throttle is closed and regeneration begins, the synchro piston is positioned inside the idle-mode rocker arm, disengaging the lift-mode rocker arm so that the valve remains at rest. Since the cylinder is sealed off, pumping losses (resistance caused by engine aspiration) that result in engine friction are reduced, and the wheels' rotational energy is effectively transmitted to the motor. Moreover, cylinder idling can be maintained at engine speeds as low as 1,000rpm, for even greater regenerative efficiency.

VTEC The team refined this technology over the next few years, eventually creating VTEC, which not only has variable valve timing, but also variable lift. Instead of turning off two valves during low rpm driving, as was the case with REV, the DOHC VTEC system employs all four valves at all times. The camshaft design had three lobes per cylinder, two low cam lobes and one high cam lobe. The two low cam lobes were tuned for drivability and economy. The high cam lobe actuated a cam follower that was disconnected from the two cam followers that actuated the valves while at low rpm. When the motor reached higher engine speeds, a VTEC solenoid sent hydraulic pressure to locking pins that connect all three cam followers. At this point, only the radical third cam lobe actuated the valves for timing and lift. The increased timing and lift increased airflow in and out of the cylinders at high speed, increasing power output.

This technology debuted in April 1989 in the Japanese-spec Integra as the B16A, a 1.6-liter DOHC engine boasting 160 hp. It was followed by the Civic SiR with the same engine in the fall of the same year. As is typical, the U.S. market heard about this, but didn't have the privilege of seeing any of this technology until 1991, when Honda decided to incorporate VTEC into its V6-powered NSX super car. The NSX was an awesome Japanese exotic and as such was way beyond the reach of the average enthusiast. In 1992 average Americans gained access to VTEC technology in the 1.7-liter, 170-hp Integra GS-R engine. The Integra was well received, sending a message up the ladder to Honda Corporate that the company had really hit the mark.