Electrified Dynamic Skip Fire (eDSF): Design and Benefits

Mark Wilcutts; Masaki Nagashima; Kian Eisazadeh-Far; Matthew Younkins; Keith Confer

doi:10.4271/2018-01-0864

Tula’s Dynamic Skip Fire (DSF®) technology combines highly responsive torque control with cylinder deactivation to optimize fuel consumption of spark ignited engines. Through careful control of individual combustion events, engine operation occurs at peak efficiency over the full range of torque demand.

A challenge with skip-fire operation is avoiding objectionable noise and vibration. Tula’s DSF technology uses sophisticated firing control algorithms which manage the skip-fire sequence to avoid excitation of the powertrain and vehicle at sensitive frequencies. DSF enables a production-quality driving experience while reducing CO2 emissions by 8-15% with no impact on regulated toxic emissions. Moreover, DSF presents a high value solution for meeting global emissions mandates, with estimated cost less than $40 per percent gain in fuel efficiency. DSF is slated for production on larger engines in the near future, and is in advanced development with automotive OEMs for four cylinder applications.

In a partnership with Delphi Technologies, DSF has been implemented in 1.8 L 4-cylinder GTDI vehicles, and has been shown to provide a smooth driving experience with substantial fuel economy benefits. Further, projects coupling DSF with hybridization are under way. Hybridization, projected to soon be in place on most new vehicles, offers opportunities for additional fuel economy gains for DSF via careful control of motor and engine torques to broaden skip-fire operation over the engine operating range.

This paper discusses design features and fuel economy benefits of coupling DSF with electric hybridization, dubbed eDSF. The fuel economy benefit synergies include enhanced vehicle kinetic energy recovery through decel cylinder cutoff, and expansion of DSF zone of operation using torque assist and torque smoothing. In the torque smoothing operation an electric torque waveform is introduced in concert with the skip-fire engine operation.

A fuel economy simulation study is described, and predictions of test-cycle reduction in CO2 emissions are presented. Hardware requirements for implementing an eDSF system are discussed, as well as preliminary simulation analyses of front-end accessory drives, relevant when eDSF is implemented in a P0 configuration.

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Electrified Dynamic Skip Fire (eDSF): Design and Benefits 2018-01-0864

SAE MOBILUS