Dynamic Skip Fire: The Ultimate Cylinder Deactivation Strategy

Authors

M. Younkins PhD, A. Tripathi PhD, J. Serrano PhD, J. Fuerst BSME MBA, Tula Technology, San Jose, USA; H.-J. Schiffgens PhD, J. Kirwan PhD, W. Fedor BSME MS, Delphi, Bascharage, Luxembourg / Troy / Rochester, USA

Year

2017

Print Info

Fortschritt-Berichte VDI, Series 12, No 802

Summary

What if every ICE combustion event occurred under optimal conditions, delivering peak efficiency? What if those events could be scheduled, in real time, to provide the exact torque demanded in an automotive application? Tula’s Dynamic Skip Fire (DSF^®) technology delivers that combination. By selecting the sequence of combustion events dynamically, engine operation occurs near peak efficiency, virtually eliminating pumping losses and significantly improving thermal efficiency. The challenge with such a concept is avoiding objectionable vibration caused by stronger torque pulsations occurring at lower frequency. Tula’s DSF technology overcomes this challenge. Sophisticated objective and subjective development have enabled DSF algorithms which avoid sensitive frequencies and amplitudes. DSF ensures a smooth driving experience while delivering an 8-15% fuel consumption reduction and no impact on regulated toxic emissions. Moreover, DSF presents a high value solution for meeting global emissions mandates as these benefits cost less than 40€ per percent gain in fuel efficiency. Selecting combustion on a per-event basis enables efficient, millisecond torque modulation, allowing gear shifts without spark retard. Further, DSF provides faster torque response due to intrinsically high manifold pressure. Deactivating all intake and exhaust valves during deceleration minimizes catalyst reactivation fuel losses, which simultaneously allows additional gains in brake energy regeneration due to elimination of pumping loss during deceleration. Production implementation in larger engines is pending, and development in partnership with Delphi on a 1.8L 4-cylinder GTDI vehicle is nearing completion. Development of integrated hybrid (optimally 48V) torque smoothing amplifies DSF benefits while adding essentially zero cost to the hybrid or DSF implementation.