Cylinder Deactivation

Q: I have heard about cylinder deactivation on new cars. What is this and how does it work?

A: Cylinder deactivation (also known as displacement on demand, variable displacement, multiple displacement system, or active fuel management technology) uses engine control systems to shut off the air-fuel mixture to some of the engine’s cylinders when all the cylinders are not needed. For example, cruising at highway speeds takes less horsepower and torque than during acceleration. When additional power is not needed, the intake and exhaust valves on half the engine’s cylinders close. When the valves are closed for these cylinders, fuel is not being burned in those cylinders.