Combustion engines have experienced a mounting PR problem in recent years, as more truck OEMs, major cities and countries announce their intentions to more aggressively pursue non-diesel vehicles, especially those powered by electric drive. But proponents of the IC engine are not going down without a fight, developing new technologies and employing established solutions in new applications to improve its efficiency. Jacobs Vehicle Systems falls squarely into this camp.

Known for manufacturing heavy-duty diesel engine retarding systems and valve actuation systems, Jacobs revealed at IAA Commercial Vehicles a new cylinder deactivation (CDA) technology that uses the proven componentry of its High Power Density (HPD) engine brake. One, two or three cylinders can be deactivated as needed. CDA and HPD technologies are modular and can be integrated into an engine individually or together. 

“The benefits of CDA have been largely established by the automotive market, as there are large fuel-economy gains that match the reduced CO₂ goals in all the world CV markets,” Robb Janak, director of new technology at Jacobs Vehicle Systems, explained to Truck & Off-Highway Engineering. “The heavy-duty ICE will work to stay relevant with a global market pushing for increased electrification, but at the same time needing [the ICE] for its efficiency and long-range capability. We believe that CDA will become as common in the CV market as it is in the automotive sector, and the heavy-duty ICE will continue to evolve with additional technologies like VVA [variable valve actuation].”

Design for extreme duty cycles

For Jacobs’ CDA technology, hydraulically-activated mechanisms originally designed for HPD applications are used in the valvetrain to disable the opening of the intake and exhaust valves. The mechanism is integrated in a collapsing valve bridge system for overhead camshaft engines or with a collapsing pushrod system for cam-in-block engines. When this is combined with disabled injection in selected cylinders, the deactivated cylinders act as a gas spring and return the compressed energy of the air back to the crank.

“This CDA technology was initially developed for the extreme duty cycle and durability requirements for the heavy-duty Class 8 and industrial markets, but we have found that it is easily transferable to the medium-duty and smaller engines,” Janak said. “The mechanism is small, does not contain many parts, and is activated by a hydraulic solenoid, which is the same we use for our Jacobs engine brakes. Therefore, there is no significant weight increase.”

A big challenge—and key breakthrough—was designing a system that did not have the durability concerns Jacobs’ engineers witnessed from the automotive market, he added. “The locking mechanisms from those markets are prone to partial engagement that causes overload and premature wear-out,” he said. “Our system is designed for the 1 million-mile heavy-duty market.”

Exhaust thermal management

Higher exhaust temperatures in the operating cylinders make it possible to maintain aftertreatment temperatures when the engine is in low-load operation, helping to cut NOx emissions. Faster warm-up of the aftertreatment system after engine start-up and reduced cooling during coasting are other benefits, according to Jacobs. Temperature increases of 100-200°C (180-360°F) are achieved in low-load conditions, and 250°C (482°F) is consistently maintained at loads of approximately 15 kW (20 hp) or more.

In addition to increasing exhaust temperatures for optimal SCR (selective catalytic reduction) operation, CDA also improves the fuel economy of heavy-duty engines, according to Janak, by reducing camshaft friction, reducing pumping losses in part-load conditions, and reducing or eliminating use of the intake throttle.

At the lowest engine loads and with three of six cylinders deactivated, fuel consumption improves by up to 20%, the company claims. During vehicle coasting, CDA can be applied to some or all cylinders to further reduce the air mass flow going through the aftertreatment system to reduce both the cooling and the engine pumping losses.

“Pressure from world government regulations will continue to drive improvements to the CV market,” Janak said. “The additional challenging goal of lowering CO₂ while also reducing NOx sought by CARB [California Air Resources Board] has been demonstrated with our CDA system.”

CARB says that Board action on a lower NOx standard for on-road heavy-duty engines is expected in 2019. The organization is currently funding three stages of research projects with Southwest Research Institute (SwRI) to assess the feasibility of lower NOx emissions. Objectives of the ongoing Stage 2 program, with the National Renewable Research Laboratory (NREL) as a subcontractor, are to optimize diesel engine calibrations for low-load duty cycles and to develop a low-load certification cycle.

Jacobs’ CDA hardware has been demonstrated on seven different engine platforms, ranging from 9- to 16-L, with manufacturers in North America, Europe, China, Japan and Korea. During these trials, the technology has been subjected to over 4,300 hours of durability testing, more than 1.2 billion component cycles, and 500 million cycles of fatigue and overload testing. The company believes that CDA is production-ready. 

“We believe this will be widely adopted by 2024, but some customers and markets are looking to do this as early as 2022 and even late 2020,” Janak said. Continue reading »