This could all be wrong, but it's what I found on google.
The Mazda2 has S-VT (sequential valve timing).
S-VT (sequential valve timing) controls the valve timing in various driving modes, through continually varying the opening and closing timing of the intake valve, to give the most suitable operation. It goes without saying that the application of this control technology has simultaneously improved both the performance of the engine and its fuel efficiency.
S-VT is composed of a vane actuator, which continually varies the phase of the intake valve timing and the crank angle through oil pressure, along with a computer, which calculates the intake valve timing, and an oil control valve (OCV), which controls the oil pressure in accordance with instructions from the computer. The most appropriate valve timing control can be achieved through detection of the engine's revolutions, intake volume and water temperature. NOx emissions are also reduced, through the implementation of EGR.
It's different from Honda VTEC because there is no 2nd intake valve that opens up.
I think it's similar to the BMW Vanos system which also varies the timing/duration of the intake valves.
They now have double-Vanos which varies both the intake & outtake valves.
Here's how VANOS works:
VANOS is a combined hydraulic and mechanical camshaft control device managed by the car's DME engine management system.
The VANOS system is based on an adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds an adjustment of the intake and outlet camshafts.
VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed.
VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy. The latest version of VANOS is double-VANOS, used in the new M3.
