The 1.6L engine in the Micra uses continuously variable (within a set range) valve timing on the intake & exhaust camshafts / valves. (Information source)
Above: at idle, the system enables an Atkinson-cycle approach by delaying closure of the intake valves to reduce compression load. The Atkinson-cycle allows more expansion than compression to improve heat efficiency.
Above: in normal operation, EGR (Exhaust Gas Recirculation) is varied by overlapping the open cycles of intake and exhaust. By recirculating some exhaust into the cylinder, pumping loss is reduced.
While the Atkinson-cycle and EGR help improve fuel efficiency, neither achieves really stable combustion because of the lower compression and temperatures of the Atkinson cycle and the refeeding of unburned exhaust gas in the combustion chamber with EGR. Nissan uses a Dual Injector system to compensate for these drawbacks; together with CVTC the two systems boost fuel efficiency up to 4% compared with Nissan gasoline-powered engines in the same class, and reduce the amount of rare metal required in the catalyst.
Above: camshaft actuator housing detail shown on the intake side (left side in image) of a Nissan V6 engine with CVTC.
The twin (intake & exhaust) valve control system operates on the Micra's engine using hydraulic pressure -- engine oil directed through oil pathways in the actuator from ECU-controlled hydraulic valves.
This Youtube video explains how the system works. The presenter actually demonstrates with parts from an HR16DE engine:
See also: http://micra-forum.com/showthread.ph...cifications%29