Study shows cylinder deactivation results in fuel savings

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Updated Nov 5, 2019

Jacobs Vehicle Systems recently released the results of fuel consumption and emission reduction tests with the company’s Cylinder Deactivation (CDA) technology.

At the North America Commercial Vehicle Show in Atlanta last week, Jacobs announced that its CDA was installed on a 13-liter Navistar engine under evaluation with the U.S. Department of Energy’s Super Truck II program and showed a 3% improvement in fuel consumption. It also provided for a corresponding decrease in NOx emissions from the baseline of 0.107 grams per horsepower-hour to 0.097 grams in a heavy duty Federal Test Procedure transient cycle test. The NOx reduction is due to the increased exhaust temperatures during cold operation while in CDA mode, which pushes the SCR (Selective Catalytic Reduction) system to its most efficient range of 250–400°C.

Robb Janak, Jacobs’ director of new technology, noted CDA allows a six-cylinder diesel engine to operate on three of cylinders when under light load conditions and during cold starts.

“The CDA mechanism in the valve-train allows the valves in the deactivated cylinders to simply remain closed,” he said. “The injectors in those cylinders go to zero fuel at the same time to reduce fuel consumption. The engine switches from six-cylinder operation to three-cylinder operation via CDA whenever the load drops below a predetermined threshold.”

At the lowest engine loads and with three of six cylinders deactivated, Jacobs says fuel consumption can improve by up to 20 percent. During vehicle coasting conditions, CDA can be applied to some or all cylinders to further reduced the air mass flow going through the aftertreatment system to both reduce the cooling, and also reduce engine pumping losses, allowing the vehicle to coast further with less fuel.

Janak said the system had undergone lab testing and optimization for several years and has been on a truck for nearly a year. CDA is now ready for additional tests on the road. Jacobs’ Cylinder Deactivation hardware has so far been demonstrated on 10 different heavy-duty engine platforms, covering 7 to 15-liter engines, as well as six different heavy-duty truck road tests. It has undergone 6,900 hours and 118,000 km of durability testing. There have been more than 1.9 billion test cycles on CDA components and over 470 million cycles of fatigue and overload testing.

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Super Truck II is a multi-million dollar program involving the DOE, truck manufacturers and equipment suppliers to, in part, develop and demonstrate cost-effective technologies to improve medium- and heavy-duty truck efficiency.

Jason Cannon has written about trucking and transportation for more than a decade and serves as Chief Editor of Commercial Carrier Journal. A Class A CDL holder, Jason is a graduate of the Porsche Sport Driving School, an honorary Duckmaster at The Peabody in Memphis, Tennessee, and a purple belt in Brazilian jiu jitsu. Reach him at [email protected].