Cylinder shut off on demand, how does the engine shut down and deactivate cylinders and still run

Описание: This advanced technology temporarily shuts down four of the eight cylinders when engine load is low — like when cruising on the highway or coasting at steady speed. The result? Lower fuel consumption and reduced emissions, without compromising performance.

Here’s how it works:

When conditions are right, the system deactivates cylinders 2, 3, 5, and 8. To do this, the camshafts are disengaged via special actuators, closing the valves and cutting off fuel injection. These cylinders essentially “go to sleep,” reducing internal friction and improving efficiency.

The transition is incredibly fast — taking just milliseconds — and virtually imperceptible to the driver. Thanks to sophisticated engine mounts and active noise cancellation, the V8 remains smooth and refined, even when running on only four cylinders.

As soon as more power is needed — for overtaking or acceleration — the system reactivates all eight cylinders seamlessly, delivering the full performance expected from a V8.

It’s this intelligent balance between power and efficiency that makes Audi’s V8 CoD system so effective — offering the thrill of a high-performance engine with the sensibility of modern efficiency.

Audi Cylinder on Demand — engineered for real-world performance with no compromise.


Cylinder deactivation facilitates the deactivation of not required cylinders within part-load operations in almost every gasoline engine. This saves fuel and thus reduce CO2-output.

When the driving situation allows for cylinders to be deactivated -- e. g. upon marginal requirements on the motorway -- the engine is made ready for switching off some of the cylinders. For the still active cylinders, that means having to help generate the torque otherwise contributed by the deactivated ones.
As a result of the shift of the load point and due to the partially deactivated charge exchange, the fuel consumption and the CO2-output are reduced.

When driving requirements demand the cylinders to be reactivated, for an overtaking maneuver for instance, this occurs within just milliseconds. Engine activities are carried out in a torque-neutral manner, imperceptible for the passengers in the vehicle.
Cylinder deactivation is a highly effective measure to reduce fuel consumption and CO2-output of combustion engines while meeting the most stringent demands for driving dynamics and comfort.

Credit - Audi Communications

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