Cylinder deactivation

ABSTRACT

In cylinder deactivation, a number of engine cylinders are shut down when less power is needed to save fuel.

The simple fact is that when we all need small amount of power, such as for crawling around town, what we really need is a smaller engine. To put it another way, an engine performs most efficiently when it’s working harder. So ask it to do the work of an engine half its size and efficiency suffers. ‘Pumping’ or ‘throttling’ losses are mostly to blame. When a petrol engine is running with the throttle wide open, pumping losses are minimal. But at part throttle, the engine wastes energy trying to breathe through a restricted air way and bigger the engine, the bigger the problem. Deactivating half the cylinders at part load is much like temporarily fitting a smaller engine