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Cylinder Deactivation

Cylinder Deactivation, or CDA,  is a technique in multi-cylinder engines where a combination of cylinders are systematically disabled, effectively reducing the engine’s displacement, improving overall engine efficiency and fuel economy.  

CDA is achieved by deactivating the intake and exhaust valves for the deactivated cylinder. This can be done on multiple cylinders of an engine providing variations of active cylinder displacement. For gasoline engines, this is done to improve pumping work and increase fuel economy. 

Cylinder deactivation is not just for gasoline engines.  In diesel engines, cylinder deactivation is used for the purpose of exhaust heating. By deactiving cylinders at low loads, the remaining active cylinders work harder and produce more heat, which gets the aftertreatment system hotter quicker and reduces emissions.  Learn more below. 

Gasoline engine cylinder deactivation

In gasoline engines, CDA essentially operates fewer cylinders at higher power providing displacement on demand.  It optimizes engine performance by providing full power when required and increasing efficiency when less power is needed


Fuel economy

  • Dual mode operation deliver significant improvement in overall fuel efficiency by reducing pumping losses

Optimized air flow

  • Optimizes air flow effiency with seamless switching from normal to low lift occurring in less than one camshaft revolution


  • Maintains centerlines and utilizing existing envelope

Diesel engine cylinder deactivation

Diesel cylinder deactivation (CDA) and early/late intake valve closing (EIVC/LIVC) technologies can be used to reduce fuel consumption between five and 25 percent, increase the rate of aftertreatment warm up, and maintain higher temperatures during low load operation. These can also be used at road loads to achieve active diesel particulate (DPF) regenerations without requiring the traditional method of dosing the diesel oxidation catalyst.

Vehicle acceleration is limited by the engine’s ability to increase the airflow quickly enough to allow the addition of sufficient fuel to meet the desired torque and power. Results show that it is possible to operate a diesel engine at low loads in CDA without compromising its torque and power capabilities, a key finding in enabling the practical implementation of cylinder deactivation in diesel engines, which initial testing shows has no negative effects on engine response.

EIVC/LIVC modulation reduces the effective compression ratio, which decreases nitrogen oxides (NOx) through reductions in in-cylinder temperatures prior to, during and following combustion. EIVC/LIVC enables the engine calibration to be tuned for better engine efficiency, including earlier injection timing.

Selective catalytic reduction (SCR) systems operate most efficiently when temperatures are between 250 and 450 degrees Celsius. Once the aftertreatment has reached this temperature range, it is preferable to maintain turbine outlet temperature (TOT) within this range so that dosing of the diesel oxidation catalyst, which still requires temperatures above 250 degrees Celsius, is not needed to keep SCR temperatures elevated.

Eaton’s CDA and EIVC/LIVC technology can operate at up to 3 to 4 bar BMEP at all speeds, which reduces emissions by improving aftertreatment thermal management while providing the welcome side effect of better fuel economy. These technologies can be used at higher loads for DPF regeneration. Similarly, IVC modulation can be used at higher loads to enable Miller cycle operation to improve engine fuel efficiency.

Other variable valvetrain functions include exhaust valve opening (EEVO) and internal exhaust gas recirculation (iEGR), which help heat the exhaust for improved catalyst efficiency and improved emissions.