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Multi-level Miller-cycle Dynamic Skip Fire (mDSF) is a combustion engine technology that improves fuel efficiency by deciding on each cylinder-event whether to skip (deactivate) the cylinder, fire with low (Miller) charge, or fire with a high (Power) charge. In an engine with two intake and two exhaust valves per cylinder, skipping can be accomplished by deactivating all valves, while firing with a reduced charge is accomplished by deactivating one of the intake valves. This new ability to modulate the charge level introduces new failure modes. The first is a failure to reactivate the single, high-charge intake valve, which results in a desired High Fire having the air intake of a Low Fire. The second is a failure to deactivate the single intake valve, which results in a Low Fire having the air intake of a High Fire.

Amid various cylinder deactivation technologies in automobile engines which provide better fuel efficiency, Dynamic Skip Fire (DSF) has proved to be promising. In DSF, a firing decision is made before every cylinder firing opportunity based on the engine torque requested. Providing this technology to automakers in form of a software object integratable with the customer’s engine controller is done by careful specification of interfaces and execution context definitions. The timing and performance of the software objects integrated with controller firmware can be dependent on the platform and compiler development environment used by the customer. This paper discusses the development of a code test environment for producing high-confidence verification. To do so an industry-accepted verification tool suite is used. Execution timing data of various functions of the source code is analyzed in detail, as well as input-output correctness.

Cylinder deactivation is a technology seeing increased automotive deployment in light of more demanding fuel economy and emissions requirements. Examples of current production systems include GM's Active Fuel Management and Chrysler's Multi-Displacement System, both of which provide one fixed level of deactivation. Dynamic Skip Fire (DSF), in which the number of fired cylinders is continuously varied to match the torque demand, offers significantly increased fuel savings over a wider operating range than the current production systems. One of the biggest challenges in implementing cylinder deactivation is developing strategies to provide acceptable Noise, Vibration and Harshness (NVH); this paper discusses those challenges and the methodologies developed. This work covers theoretical root causes; proposed metrics to quantify the NVH level; algorithmic and physical mitigation methods; and both subjective and objective evaluation results.