ACT cylinder deactivation function. How does it work and what gives in practice?

Fuel consumption is one of the key criteria when choosing a car for a buyer. Therefore, manufacturers use various solutions to reduce fuel consumption. One of them is the ACT function, which disables half of the engine's cylinders.

It's no secret to most drivers that a car's engine needs the most power to start the car and when it needs to accelerate hard, such as when overtaking. On the other hand, when driving at a constant speed, the power that the engine nominally has is usually not used. Instead, the fuel is used to power the cylinders. Therefore, the designers considered such a situation to be wasteful and suggested that when the full power of the drive unit is not needed, turn off half of the cylinders.

You might think that such ideas are implemented in expensive cars with large units. Nothing could be more wrong. Solutions of this type can also be found in cars for a wide range of customers, for example, in Skoda.

This cylinder deactivation feature is available in the 1.5 TSI 150 hp petrol engine, which can be selected for the Skoda Octavia (saloon and station wagon) and Skoda Karoq, both manual and dual-clutch automatic transmissions.

The solution used in this engine is called Active Cylinder Technology - ACT. Depending on the engine load, ACT accurately deactivates two of the four cylinders to reduce fuel consumption. Two cylinders are deactivated when there is no need for additional engine power, i.e. during rough driving at low speed.

It is worth adding that automatic transmission was already used several years ago in a 1.4 TSI engine with a capacity of 150 hp, which was installed in the Skoda Octavia. Later, this unit began to be installed under the hood of the Superb and Kodiaq models.

In relation to the 1.4 TSI engine, a number of modifications have been made to the 1.5 TSI unit. The manufacturer reports that the cylinder stroke is increased by 5,9 mm while maintaining the same power - 150 hp. However, compared to the 1.4 TSI engine, the 1.5 TSI engine is more flexible and responds faster to the accelerator pedal.

In turn, the intercooler, that is, the cooler of the air compressed by the turbocharger (to force more air into the cylinders and increase the efficiency of the engine), was designed to cool the compressed cargo to a temperature of only 15 degrees higher than the engine. ambient temperature. As a result, more air enters the combustion chamber, resulting in improved vehicle performance.

The petrol injection pressure has also been increased from 200 to 350 bar, which has optimized the combustion process.

The operation of the engine mechanisms has also been improved. For example, the crankshaft main bearing is coated with a polymer layer, and the cylinders are specially structured to reduce friction when the engine is cold.