What is it?
With car manufacturers seeking ever cleverer ways to reduce the consumption of their latest models to meet stringent emission standards we've been exposed to quite a lot of new fuel saving technologies n recent times.
Features such as automatic stop/start, brake energy recuperation, on-demand engine ancillaries and low rolling resistance tyres have gone from being exotic options not that long ago to just about universal standard today.
However, they're not the end of it. Because, as signs have it, there's another fuel saving technology that's about to go prime time: cylinder shutdown, or as Volkswagen prefers to refer to it, Active Cylinder Management (ACM), for small displacement engines.
Previewed by Volkswagen earlier this year, it is included on a frugal new version of the German car maker's latest turbocharged 1.4-litre four-cylinder direct injection petrol engine, the EA211 as it is known, fitted to a new sporting version of the Polo called the BlueGT.
The principle of ACM is simple, and a good deal less expensive than other systems already applied to larger capacity powerplants, with a set of electronic actuators sitting above the camshaft on the middle two cylinders controlling the movement of the valves and fuel injection.
At revs between 1400 and 4000rpm and torque loads between 18 and 74lb ft - a characteristic Volkswagen claims covers nearly 70 per cent of all driving states, the valves and injection process is shut down, effectively turning the engine into a 700cm3 twin for lower consumption and emissions, most noteably in city driving and at constant motorway speeds.