STOP mixing VTEC with VVT!
VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different rpm ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way, the engine gets the best features of low-speed and high-speed camshafts in the same engine.
It's true that the engine's valve timing changes, but that's a secondary to the primary objective of VTEC - which is valve lift.
i-VTEC: (intelligent-VTEC) introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines. The technology first appeared on Honda's K-series four cylinder engine family in 2001 (2002 in the U.S.). In the United States, Honda first debuted the technology on the 2003 Honda Civic Si EP3 with the economy version. Valve lift and duration are still limited to distinct low- and high-RPM profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. Phase changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to somewhat advanced at full throttle and low rpm. The effect is further optimization of torque output, especially at low and midrange RPM.
Finally! You can now have real VVT without a change in active cam profiles !
Toyota's VVT was a 2 mode CAM PHASING system (no lift) and eventually progressed into VVT-i which allowed true variable timing.
Toyota's VVTL-i (Variable Valve Timing and Lift intelligent system) included what the original VTEC had - 2-mode valve lift adjustment.
So there you have it, VTEC IS NOT VVT. Honda calls it Variable Valve Timing because technically the valve timing changes. You cant change valve lift efficiently without changing timing.