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Jacobs Cylinder Deactivation Jacobs

Jacobs, Tula collaborating on cylinder deactivation tech

Jacobs Vehicle Systems, a manufacturer of heavy-duty diesel engine retarding systems and valve actuation systems, recently entered into a collaboration with internal combustion controls company Tula Technology.

The two businesses will work together to enable Jacobs to further develop cylinder deactivation technologies, which reduce engine fuel consumption and emissions, Jacobs said.

Jacobs introduced its Cylinder Deactivation (CDA) technology for medium- and heavy-duty commercial vehicle engines in 2018, and Tula, headquartered in Silicon Valley, licenses its Dynamic Skip Fire (DSF) technology for major automotive OEM gasoline applications. The new working partnership between the two companies will utilize Tula’s DSF controls to support Jacobs’ diesel deactivation hardware development.

“Jacobs is very excited to partner with Tula to progress cylinder deactivation technology by combining our companies’ strengths,” said Robb Janak, director of new technology at Jacobs Vehicle Systems. “Vehicle manufacturers are looking for new and improved technologies to comply with stricter legal limits on CO2 and NOx emissions. New test measures, such as Real Driving Emissions and CARB Low Load Cycle for heavy duty trucks are encouraging the adoption of smarter technologies that address these requirements.

“Cylinder deactivation is a great solution, technically proven and cost effective.”

With Jacobs’ CDA, cylinder deactivation mechanisms originally designed for the company’s High Power Density (HPD) engine brake are used in the valvetrain to disable the opening of the intake and exhaust valves, the company said. The hydraulically activated 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, multiple cylinders can be deactivated as needed. At low engine loads with three of six cylinders deactivated, fuel consumption can be improved by up to 20%. 

Jacobs’ CDA reduces emissions by achieving higher exhaust temperatures by maintaining after-treatment temperatures for optimal efficiency of SCR (Selective Catalytic Reduction) systems, even when the engine is in idle or low load operation, Jacobs claimed. CDA also enables faster warm-up after engine start-up of the after-treatment system, and minimizes cooling of after-treatment during coasting. CDA additionally reduces camshaft friction and pumping losses in part-load conditions, and can reduce or eliminate use of the intake throttle, all of which yields overall improvements in fuel consumption while simultaneously increasing  exhaust temperatures.

“Tula is pleased to support our industry partner Jacobs Vehicle Systems in its development of Dynamic Skip Fire-enabling hardware for the diesel engine marketplace,” said John Fuerst, senior vice president of engineering at Tula.

Tula developed a variable cylinder deactivation system, integrating advanced digital signal processing and software with sophisticated engine control algorithms. This technology reduces fuel consumption of gasoline engines by 6%-15% on real-world drive cycles, Tula maintained. This collaboration aims to enable Jacobs to develop and demonstrate deactivation hardware required for diesel engines.

The Tula DSF system makes dynamic firing decisions based on how much torque is requested and then selectively choosing which cylinders will be active or deactivate to meet performance demand. When more torque is required, the firing density increases, and when there is less demand for torque, firing density decreases. This means the control algorithm effectively creates an engine with optimal displacement for the torque required, Tula said.

Tula’s control system also helps ensure production level NVH. By having the ability to select which cylinders are fired every engine cycle, and accounting for the frequencies and amplitudes of vibration produced by cylinder combinations, the control algorithm determines the cylinder firing sequences that deliver smooth operation and reduced cost to the driver at the fuel pump.

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