Active Cylinder Technology (ACT), also known as Cylinder Deactivation, is a feature in some modern cars that allows the engine to temporarily deactivate or "shut off" specific cylinders under certain driving conditions.

The purpose of ACT is to improve fuel efficiency by reducing the amount of fuel consumed during light-load or cruising conditions when all engine cylinders are not necessary for power delivery.

Here's how Active Cylinder Technology typically works:

Cylinder Deactivation

When the vehicle is operating under light-load conditions, such as cruising on a highway or coasting, the engine control unit (ECU) can deactivate specific cylinders. For example, in a four-cylinder engine, it may deactivate two of the cylinders, effectively turning it into a two-cylinder engine.

Valve Operation

To deactivate the cylinders, the engine's intake and exhaust valves for those cylinders are kept closed, preventing fuel and air from entering or exiting them. This action effectively shuts down the deactivated cylinders and prevents any power generation from them.

Seamless Transition

The transition between cylinder activation and deactivation is designed to be seamless and imperceptible to the driver. The engine control unit continuously monitors various parameters such as throttle position, vehicle speed, load demand, and engine temperature to determine when cylinder deactivation is appropriate.

The transition is usually accomplished by adjusting fuel injection, valve timing, and ignition timing to maintain smooth operation and minimize vibration.

Reactivation

When the driver demands more power, such as during acceleration or heavy load conditions, the deactivated cylinders are quickly reactivated, and all cylinders resume their normal operation to provide the required power output.

Benefits of ACT

The benefits of Active Cylinder Technology include improved fuel efficiency, reduced emissions, and lower operating costs. By deactivating cylinders when not needed, the engine consumes less fuel, resulting in better mileage.

However, it's important to note that the effectiveness of ACT can vary depending on driving conditions and the specific implementation of the technology in different vehicle models.

Many automakers, including Volkswagen, General Motors, Honda, and others, have implemented Active Cylinder Technology in their vehicles to improve fuel economy without compromising performance.

For detailed information, please watch the full video.