VVA - Variable Valve Actuation

How does VVA work?

The technology used by some Yamaha engines for improved power and economical use. Also similar to Honda's VTEC.

At low RPM, the low lift cams are engaged, thus the valves only opens in a short duration or small lift. The effect is fuel economy and manageable power delivery in normal riding.

At high RPM, the "wild cams" gets engaged. These cams have high lift or long duration. Similar to racing cams. The effect is increased power delivery at high rpm when needed.

With VVA, the "wild cams" and "soft cams" are selected by an electronically controlled actuator, (in other brands, actuator is engaged by pressurised solenoid) it pushes a small pin to select which rocker arm to activate. The actuator is activated at a certain RPM electronically via ECU. Some cars/bikes engage the VTEC at 5000 rpm, some models activate higher or lower rpm, depending on the manufacturer. Racing ECU's are controllable via laptop and one can change what RPM to engage these wild cams.

On the other hand, Variable Valve Timing of VVT-i, the acutuator is located in the cam gears, the ECU decides the valve opening duration, to advance or retard the combustion. The effect is to control the engine timing, the cams by few degrees forward or backward from the TDC, thus increases or decreases the power delivery at a desired RPM.

There you go. Variable Valve Actuation is good for you!