Cylinder on demand by Audi, now available on the 1.4 TFSI, 4.0 TFSI and W12 engines

Selective cylinder deactivation is already becoming more common in several models, mainly luxury and high-priced ones. In the case of Audi, three of its petrol engines now include this selective cylinder deactivation technology: the 1.4 TFSI COD with four cylinders, the V8 4.0 TFSI COD and now also the W12 COD in the new Audi A8 L.

This technology deactivates half of the cylinders at low and intermediate loads in the higher gears, until the driver accelerates hard again. In this phase, efficiency increases in the cylinders that remain active, because the operating points shift towards higher loads.

Activation and deactivation are so smooth that they are barely noticeable. In the eight-cylinder models, the active engine mounts take care of compensating for any possible vibration, while the Audi Noise Cancellation system cancels any noise produced during the cylinder deactivation phase by emitting sounds with an opposite-phase frequency. These solutions are used independently or both in combination, depending on the engine.

In the 1.4 TFSI COD engine, the system disconnects cylinders two and three, and in the V8 4.0 TFSI it does so with cylinders number two, three, five and eight. The cylinders are deactivated by cutting off the ignition and fuel injection. The valves are closed by elements that move along the camshaft by means of electromagnetically actuated pins. Beforehand, the combustion chambers are filled with fresh air to reduce the internal pressure in the cylinders.

In the case of the 500 hp W12 engine in the new Audi A8 L, the system has a slight variation, in which the valves remain open. The system first cuts off fuel injection and ignition for all the cylinders on the engine’s left bank, so that it runs on six cylinders. If driving conditions allow it to continue in six-cylinder mode before the catalytic converter temperature drops too far, this bank is reactivated and the right bank is deactivated, so that during the cylinder deactivation phase, the connection and disconnection of the two banks alternate.

COD technology drastically reduces fuel consumption. In the RS 6 Avant and RS 7 Sportback, for example, the saving is approximately 5%. The 4.0 TFSI COD consumes only 9.8 L/100 km. The 1.4 TFSI COD in the Audi A3 averages just 4.7 L/100 km; here, cylinder deactivation saves approximately 0.4 L/100 km according to the official homologated consumption cycle. With a moderate driving style, consumption can be reduced by up to 20%.

Source | Audi