Improving fuel economy with Cylinder Deactivation Technology (CDA)

As the push for cleaner, more efficient engines, Cylinder Deactivation (CDA) is helping internal combustion technology move forward. By intelligently shutting down select cylinders when full power isn’t needed, CDA reduces fuel consumption, carbon dioxide (CO₂) emissions, and better manages nitrogen oxides (NOₓ). It’s a powerful tool for manufacturers preparing to meet upcoming emissions standards in North America and Europe.

Cummins Valvetrain Technologies (CVT) is leading innovation in this space, integrating advanced valvetrain solutions that make CDA performance seamless, reliable, and compatible with high-performance engine braking systems.

What are the benefits of cylinder deactivation?

CDA allows internal combustion engines to temporarily deactivate some of their cylinders when full power is not needed, such as when a vehicle is coasting, idling, or low-load driving. 

With fewer cylinders working during light-load conditions, the engine moves less air and less fuel, which results in less energy being wasted. The result? Better fuel economy, lower CO₂ emissions, and reduced operating costs by minimizing pumping losses and engine friction.

CDA also helps maintain higher exhaust temperatures during low-load driving, keeping the aftertreatment system—especially the Selective Catalytic Reduction (SCR) system—working efficiently to reduce NOₓ emissions. With fewer cylinders pumping cold air, the exhaust stays hot even during extended coasting or light engine loads.

How does cylinder deactivation work?

Cylinder Deactivation (CDA) activates when the engine isn’t operating at full power—during idling, light acceleration, or when returning with a lighter load. In these low-demand situations, the system automatically shuts down select cylinders.

Here’s how: CDA temporarily closes the intake and exhaust valves of specific cylinders and disables their fuel injectors, stopping airflow and fuel use in those cylinders. This prevents energy loss from unnecessary pumping. The remaining cylinders keep running normally to provide the required power, and the engine continuously adjusts which cylinders are active based on driving conditions.

When full power is needed, all cylinders re-engage instantly and automatically. The same components that control CDA are also integral to the high-performance engine brake—the 1.5-stroke High Power Density®(HPD) Jake Brake®—providing extra braking force for descents or sudden stops. These components are not just similar, but CDA, engine braking, and the HPD Jake Brake are fully integrate modular technologies to the valvetrain

This seamless switching between modes allows the engine to adapt to changing loads and road conditions, all while optimizing fuel efficiency and emissions in real time.

How much does fuel economy improve with cylinder deactivation technology?

Extensive lab and real-world testing show that CDA delivers measurable gains in fuel efficiency, especially during low-load conditions:

• Up to 12% fuel savings in low-load test cycles
• 3–5% fuel savings in EPA FTP test cycles.
• 14–18% less fuel used during idle when operating in 4-cylinder mode compared to full 6-cylinder operation.

In SAE J1321 vehicle fuel consumption tests — a trusted industry standard for evaluating real-world highway fuel savings — trucks equipped with Jacobs® CDA technology showed strong efficiency gains. The test compares a CDA-equipped vehicle to a control vehicle under identical conditions, isolating the technology’s true impact on fuel savings.

• 2.76% fuel savings when fully loaded on the highway
• 2% fuel savings in a separate distribution route test  

While on-road savings in SAE J1321 tests are typically lower than lab-based results, CDA’s greatest benefits come during conditions like idling, coasting, and light-load operation. Over time, these small gains can translate into significant fuel and emissions reductions.

How do drivers experience cylinder deactivation?

From the driver’s perspective, the transition is seamless. In practice, there’s no noticeable change in performance—speed and drivability stay the same—just better fuel economy and reduced friction with no tradeoffs.

The switch between active and deactivated cylinders happens automatically and is hardly noticeable. CDA also aids thermal management, as deactivating cylinders during coasting helps keep the exhaust system hotter for longer. This prevents cooling and ensures the SCR system stays within its optimal temperature range, even during extended low-load driving.

Conclusion: a key technology for fuel efficiency and emissions control

Cylinder Deactivation is a smart, efficient solution that helps fleets cut fuel costs, improve emissions performance, and stay ahead of tightening regulations. Whether in long-haul operations, return-to-base cycles, or stop-and-go distribution routes, CDA consistently delivers real-world fuel economy gains, all while maintaining the power, reliability, and performance drivers expect from an engine. This performance is made possible by Cummins Valvetrain Technologies, which provides the precision and durability needed to make CDA work seamlessly on the road.