Active Cylinder Technology (ACT)

Sourced from: Volkswagen site : Volkswagen

Active Fuel Management (formerly known as displacement on demand (DoD)) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to “turn off” half of the cylinders under light-load conditions to improve fuel economy.

In this kind of innovation Volkswegan has developed it as Active Cylinder Technology (ACT) to improve the fuel efficiency. The 1.4 TSI of the Polo BlueGT is the top engine of the entirely new series of petrol engines that has been developed. The engine range consists of 1.0, 1.2 and 1.4 litre engines. The efficient 1.0-litre three-cylinder engines are used to drive such cars as the new up!. The 1.2- and 1.4-litre four-cylinder engines were each designed as charged direct fuel injection engines (TSI).

The outstanding technical aspect of the engine is its active cylinder management (ACT). Volkswagen is the first carmaker to implement this fuel saving cylinder deactivation technology on four-cylinder engines, as it was previously the preserve of large eight or 12 cylinder engines. Shutting down the second and third cylinders during low and medium load states reduces fuel consumption in the EU driving cycle by about 0.4 l/60 miles*. For urban driving it saves as much as 1.0 l/60 miles*. Even while driving at 70 km/h in fifth gear, fuel consumption of the Polo BlueGT is reduced by 0.7 l/60 miles*.

*This information should be used for illustration purposes only. Standard EU Test figures for comparative purposes, may not reflect real driving results.

Active cylinder Technology (ACT) mode of operation.

ACT is active over an engine speed range between 1,400 and 4,000 rpm and torque outputs between 25 and approx. 100 Nm – a range that covers nearly 70 per cent of all driving states in the EU driving cycle! If the driver presses the accelerator pedal hard, both cylinders begin to work again without a noticeable transition. The high efficiency of the system has no negative effects on smooth running: even with two cylinders the excellently balanced the 1.4 TSI engine of the Polo BlueGT runs very quietly and with low vibration.

All mechanical switchover processes take place within one-half of a camshaft rotation; depending on engine speed this takes between just 13 and 36 milliseconds. Accompanying interventions in ignition and throttle valve processes smooth the transitions. What’s more, thanks to an accelerator pedal sensor and intelligent monitoring software, the system can also detect irregular driving profiles – such as during a drive through a roundabout or in sporty shifting on a highway. In such cases, cylinder shut-off is deactivated. The driver is aware of whether two or four cylinders are active by a related indicator in the multifunction display between the speedometer and tachometer.

ACT components.

Altogether, the components of active cylinder management weigh just three kilogrammes. Their actuators, the camshafts and their bearing frames are integrated in the cylinder head; two low-friction bearings reduce friction of the shafts. It is only with the TSI concept – petrol direct injection plus turbocharging – that a cylinder deactivation is even conceivable in its form today.

To understand how it works click on :Active Cylinder Technology