mDSF: Improved Fuel Efficiency, Drivability and NVH Via DSF and Miller Cycle Synergies 2019-01-0227
mDSF is a novel cylinder deactivation technology being developed at Tula Technology, which integrates Dynamic Skip Fire (DSF) and Miller cycle engines to deliver maximum fuel consumption improvements at minimal cost. mDSF employs a valvetrain with variable valve lift plus deactivation and novel control algorithms founded on Tula’s proven DSF technology. This allows cylinders to dynamically alternate among 3 potential states: high-charge fire, low-charge fire and skip or deactivation. The low-charge fire state is achieved through an aggressive Miller cycle with Early Intake Valve Closing (EIVC). The three operating states in mDSF can be used to simultaneously optimize engine efficiency and driveline vibrations. Acceleration performance is retained using all-cylinder, high-charge firing mode.
The lower cost valvetrain solution for mDSF comprises of asymmetric intake valve lifts and/or ports, with one power charging port and one high efficiency Miller port. The power charging port is deactivated independently, whereas the Miller port is coupled to the exhaust valves. High-charge firing is realized with all four valves active, low-charge firing is realized with the power valve deactivated, and skip is realized with all four valves deactivated.
The mDSF asymmetric valve strategy was tested in a production Miller cycle engine and the efficiency impact was minimal. Maximum torque was reduced by 3-8%, but it is expected this can be recovered with combustion system optimization. Engine fuel consumption maps were generated based on experimental data and mDSF “flyzones” were estimated Tula’s extensive NVH database and experience. Compared with a production state-of-the-art Miller cycle engine baseline, mDSF is projected to reduce fuel consumption by 9.5% in the US City-Highway cycle and 7.5% in the WLTC (Class 3). Combined with a relatively low added cost of the proposed valvetrain design, mDSF presents an unparalleled cost-benefit ratio in the market with relatively short-term production viability.
Elliott Ortiz-Soto, Benjamin Wolk, Hao Chen, Matthew Younkins