Audi’s A3 equipped with the 1.4-liter TFSI engine will have access to Cylinder-on-Demand (CoD) technology.

According to Audi, the A3 with CoD technology will return fuel economy figures of up to 60.1mpg. Capable of making a near seamless switch between two cylinder and four cylinder operation in as little as 13 milliseconds, this system allows the A3 to cruise ultra-frugally, but also immediately draw on full power when required.

In the UK, CoD models carry a premium of £850 over their continuing 1.4 TFSI 122PS equivalents in both ranges, positioning them as attractive alternatives to the 2.0-litre TDI variants.

The A3 Sportback returns 58.9mpg. In all versions, an engine start-stop system cuts in when the cars are waiting at traffic lights and junctions because no-cylinder operation is even more efficient than two-cylinder operation.

Audi’s cylinder on demand technology made its debut in a similar form last year in the S6, S7 Sportback and S8. The technology was also installed recently in the new RS 6 Avant and RS 7 Sportback.

When applied to the four-cylinder TFSI engine, it shuts down the second and third cylinders under low and intermediate loads and when coasting. In order for it to do this, engine speed must be between 1,400 and 4,000 rpm.

Deactivation of the cylinders is done with sleeves called cam elements, each of which carries two different cam profiles. When the sleeves are slipped over the camshafts through the use of electromagnetic actuator, the zero-lift profiles rotate over the exhaust and intake valves. They don’t actuate the valves; the valve springs hold them closed. Injection is deactivated at the same time. Efficiency in the active cylinders 1 and 4 is increased, however, because the operating points shift toward higher loads.

As soon as the driver needs strong acceleration by pressing hard on the gas pedal, the sleeves are pushed back and the deactivated cylinders are activated again.

All of these switching operations take place in 13 to 35 milliseconds, depending on engine speed, and are carried out virtually imperceptibly thanks to manipulation of the injection system and the throttle valve and modifications to the engine bearings, the dual-mass flywheel and the exhaust system.