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mDSF is a novel cylinder deactivation technology developed at Tula Technology, which combines the torque control of Dynamic Skip Fire (DSF) with Miller cycle engines to optimize fuel efficiency 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 designated as: High Fire, Low Fire, and Skip (deactivation). The Low 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 the all-cylinder, High Fire mode. mDSF can be implemented cost-effectively using an asymmetric intake valve lift strategy, with one high-flow power charging port and one high-efficiency Miller port.

Cylinder deactivation in multicylinder spark-ignition (SI) engines leads to increased fuel efficiency at part load by allowing fired cylinders to operate closer to their peak thermal efficiency compared to all-cylinder operation. Unlike traditional cylinder deactivation strategies that are limited to deactivating only certain cylinders, Dynamic Skip Fire (DSF) is an advanced cylinder deactivation control strategy that makes deactivation decisions for every cylinder on an individual firing opportunity basis to best meet driver torque demand while saving fuel and mitigating noise, vibration, and harshness (NVH). During DSF operation, inducted charge air mass can vary for each firing event due to the firing sequence history. To maximize efficiency, cylinder fueling should be adjusted for each firing event in DSF based on the inducted charge air mass for that event.

Misfire detection and monitoring on US passenger vehicles are required to comply with detailed and specific requirements contained in the OBD-II regulations. Numerous technical papers and patents discuss various methods and metrics for detecting misfire in conventional all-cylinder firing engines. However, the current methods are generally not suitable for detecting misfires in a dynamic skip fire engine. For example, a detection approach based on peak crankshaft angular acceleration may work well in conventional, all-cylinder firing engine operation, since it is expected that crankshaft acceleration will remain generally consistent for a given operating condition. In a skip fire engine, any cylinder or cycle may be skipped. As a result, the crankshaft acceleration peaks and profiles may change abruptly as the firing sequence changes. This paper presents two approaches for detecting misfires in a dynamic skip fire engine.