Variable Valve Timing

How is this system actually implemented, what control do you have over it and what types are in.
And are (or will) other systems for having a multi purpose engine (be) included like VRIS (Variable Resonance Induction System from Mazda) or the computer controlled systems on modern vehicles that lets you choose different settings on the fly (including torque).
These systems would be great late game i presume, allowing engines that are both powerfull and fuel efficient with or without a Vvt system.
And are (or will) other systems for having a multi purpose engine (be) included like VRIS (Variable Resonance Induction System from Mazda) or the computer controlled systems on modern vehicles that lets you choose different settings on the fly (including torque).
These systems would be great late game i presume, allowing engines that are both powerfull and fuel efficient with or without a Vvt system.