Cylinder Deactivation

Christopher White
Sep 21, 2022
3 min read

Cylinder deactivation (CDA) technology is also called cylinder-on-demand (COD). It is a clever use of technology that stops some of an internal combustion engine (ICE) from taking in fuel and air while it's running.

Cylinder Deactivation Process

The technology relies on advanced techniques to help the internal computer detect whether your vehicle requires much energy or not. Once the computer detects that your car doesn't need that much power, it will automatically freeze some of the fuel lines and allow combustion in certain cylinders, but not in all of them. Conversely, when the computer detects that additional energy is needed, it will immediately switch to full power mode and activate all cylinders.

When the computer brain in your vehicle detects that you don't require all the power the engine can provide, a cylinder deactivation solenoid valve kicks in to prevent fuel and air from entering the cylinder, which means that the combustion process in some of those cylinders can't occur, and less fuel is spent overall. See Figure 1 for an example.

Figure 1: Shows an illustration on how cylinder deactivation works. Source: cylinder deactivation concept - Bing images

Variable displacement

Variable displacement happens when the engine cylinder deactivation system allows the engine displacement to change temporarily. For example, if half of a 4.0-liter V8's cylinders are temporarily turned off, the engine functions like a 2.0-liter V4 for the deactivation duration. A large engine running on all cylinders in low-power conditions like cruising at highway speed is inefficient. Turning it into a small engine temporarily can boost fuel economy by as much as 25 percent under certain driving conditions.

Fuel consumption

The idea behind cylinder deactivation is to eliminate fuel flow to unnecessary cylinders; it can save fuel consumption. In other words, if a particular vehicle runs on eight cylinders, stops using two of them, and drops them down to six cylinders, you will see a significant drop in fuel consumption.

Advantages of Cylinder Deactivation

The benefits of a system such as this include:

Improvement in fuel efficiency
Reduced emissions
Reduction in pumping losses
Optimized airflow in the engine at low load

Manufacturers That Use CDA Technology

Some of the most notable ones are:

Volkswagen Group: Volkswagen's Active Cylinder Technology was the first application of cylinder deactivation on a four-cylinder engine, starting with the 1.4–liter TSI engine. Today, the VW Group uses the technology on other engines, such as the group's 4.0-liter twin-turbocharged V8 engine.
General Motors: Starting in 2005, GM applied its version, Active Fuel Management, to its Generation IV small-block V8 engine. The 2018 redesign of this system, called Dynamic Fuel Management, brought the ability to any number of cylinders in any combination.
Stellantis: Originally developed by Mercedes during the Daimler–Chrysler years, the Multi-Displacement System was first used on Mercedes' V12 engines and Chrysler's Hemi V8 in 2004. The Hemi V8 still uses the system today.
Mazda: Mazda started widespread use of its version in 2017 with the Mazda CX-5 compact crossover SUV–one of the most popular and best small SUV models in the US.
Honda: Honda started using its proprietary Variable Cylinder Management system in 2003 on the J family of V6 engines; it can switch the V6 between six–, four–, and three-cylinder operations.
Ford: Ford started using cylinder deactivation in 2016, and the application of the technology on its small Ecoboost engine was the first application ever on a three-cylinder engine.

Conclusion

Cylinder deactivation technology has been used to improve internal combustion engines' fuel efficiency and emissions, which can reduce fuel consumption by up to 40 percent.

References

“What is Cylinder Deactivation (CDA) Technology” Corbus F. Potgieter, accessed May 3, 2022, Cylinder Deactivation System | CarBuzz
“Cylinder Deactivation” Tom Harbid, accessed May 1, 2022, Cylinder Deactivation ❤️ What Is It and How Does It Help Save Fuel (cashcarsbuyer.com)

Article by: Christopher White