Cummins Cylinder Deactivation Saves on Fuel and Emissions

Cummins states that the Jacobs CDA system saved over to two percent on fuel usage during instrumented testing.

August 2, 2024

Matt Wolfe

Cummins reportedly observed a 77-percent reduction in NO_x was recorded on a low load cycle during laboratory testing. (Cummins)

Cylinder deactivation has become increasingly common across various types of commercial on-road ICE powertrains to meet the upcoming North American (EPA 27) and Europe (Euro 7) standards, which cover both NO_x and CO₂ emissions. Cummins announced in 2020 that it had partnered with Tula Technologies to demonstrate diesel Dynamic Skip Fire (dDSF) software on a Cummins X15 Efficiency Series inline six-cylinder engine.

Cummins CDA system uses a hydraulically actuated mechanism that integrates into a pushrod, rocker, or bridge to deactivate selected cylinders. (Cummins)

Cummins has now announced that they are seeing positive results from further on-road testing of Jacobs’ cylinder deactivation technology. According to Cummins, a fuel savings of 2.76-percent was seen in the first SAE J1321 standardized fuel consumption testing using fully laden comparison trucks on a highway route in North America. Cummins also claims that tests on a distribution route returned similar fuel savings.

Cummins tested their CDA system using a 2018 International LT625 6x4 tractor. (Cummins)

The tests were conducted using a 2018 International LT625 6x4 tractor with a 13-liter Navistar A26 450 hp diesel engine and an Eaton Endurant 12-speed overdrive AMT gearbox. Tests were conducted over 12,000 miles according to SAE’s J1321 standard fuel economy protocol. The truck was tested multiple times both with and without CDA active an average speed of 51 mph (82 kph) on the highway route, and 38 mph (61 kph) on the distribution route.

Cummins states that the Jacobs CDA system uses a hydraulically actuated mechanism that integrates into a pushrod, rocker, or bridge to deactivate selected cylinders. The mechanism is capable of individual cylinder control and is dynamically switchable between cylinders. The system will automatically shut down selected cylinders in low engine load conditions by leaving their inlet and exhaust valves closed throughout the four-stroke cycle while simultaneously deactivating the fuel injectors. When additional engine braking is required, the same components are repurposed to provide deceleration via the Jake Brake compression release engine brake.

Cummins also states that the system offers a reduction in emissions by optimizing the efficiency of exhaust after-treatment systems through thermal management. The CDA system increases exhaust temperatures at part loads and eliminates cooling, which in testing has reportedly revealed a reduction in parasitic drag when the engine is in over-run.

The CDA system will automatically shut down selected cylinders in low engine load conditions by leaving their inlet and exhaust valves closed. (Cummins)

During a lab test in 2020, a 77-percent reduction in NO_x was recorded on a low load cycle with a 2018 aftertreatment system. While NO_x emissions testing was not a focus for the reported road test, the trucks had the same calibration compliance to EPA 2018 standards. Cummins expects the results to further improve for future emissions requirements where the benefits of CDA thermal management are further utilized.

During highway tests without CDA, temperatures in the control truck’s SCR unit fell below 250 Celsius (482 Fahrenheit) for over 15 percent of the journey time. When CDA was used, SCR temperatures fell below that temperature only during the scheduled stops. On the distribution route, the mean temperature of the SCR unit was 243 Celsius with CDA engaged, 16-percent above the figure recorded without cylinder deactivation. Cummins also confirmed that in on-road testing with optimized engine and cab mounts, NVH was equivalent to the non-CDA-equipped standard engine and vehicle while at 600 rpm in idle.