Smart Cylinder Deactivation Strategies to Improve Fuel Economy and Pollutant Emissions for Diesel-Powered Applications

Mauro Scassa; Thomas Körfer; S Kevin Chen; John Fuerst; Matthew Younkins; Marco Nencioni; Shino George

doi:10.4271/2019-24-0055

Further improvement of the trade-off between CO2 and pollutant emissions is the main motivating factor for the development of new diesel engine concepts, from light-duty car applications via medium-duty commercial vehicles up to large long-haul trucks. The deactivation of one or more cylinders of a light-duty diesel engine during low load operation can be a sophisticated method to improve fuel economy and reduce especially NOx emissions at the same time.

Dynamic Skip Fire (DSF) is an advanced cylinder deactivation technology, where the decision to fire or skip singular units of a multi-cylinder engine architecture is taken just prior to each firing opportunity, based on a balanced rankling of multiple input parameters. A DSF-equipped engine incorporates the ability to selectively deactivate cylinders on a cylinder event-by-event basis for best matching of the requested driver’s torque demand at optimum fuel efficiency, while ensuring no drawback in terms of drivability with respect to fully firing engine. Dynamic Skip Fire has already demonstrated significant fuel economy improvements for throttled spark-ignition engines on a number of different applications.

The publication presents the potential of the DSF technology in improving fuel economy while supporting the realization of ultra-low tailpipe emissions for small cylinder displacements as well as bigger cylinder bore diesel applications, covering LD as well as MD Diesel powertrains. The simulation activity has been carried out using an advanced, internally developed FEV Powertrain Simulation Platform.

A representative state-of-the-art 4-cylinder 2.0-liter LD Diesel engine definition has been analyzed. Simulation results highlighted a significant CO2 benefit both on WLTC as well as RDE cycle. The analysis results obtained so far demonstrate that DSF technology, when applied to a light-duty diesel engine with optimized transmission shift scheduling, can achieve up to 0.5% to 1.5% fuel economy benefit, while realizing tailpipe nitrogen oxides (NOx) emissions reduction up to 33%. The reduction of tailpipe NOx is achieved mainly by improved conversion efficiency in the NOx aftertreatment system due to increased exhaust temperatures with DSF technology.

The investigations have been extended to a larger 6-cylinder 7.7-liter MD Diesel engine application for commercial applications. On this heavier application DSF shows approximately 50% reduction in terms of tailpipe NOx both on the European and American MD legislation cycle, together with a CO2 benefit respectively of 2.5 and 3.5%.

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Smart Cylinder Deactivation Strategies to Improve Fuel Economy and Pollutant Emissions for Diesel-Powered Applications 2019-24-0055

SAE MOBILUS