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Cylinder deactivation is an effective measure to reduce the fuel consumption of internal combustion engines. This paper deals with several practical aspects of switching from conventional operation to operation with deactivated cylinders, i.e., gas spring operation with closed intake and exhaust valves. The focus of this paper lies on one particular quantity-controlled stoichiometrically-operated engine where the load is controlled using the valve timing. Nevertheless, the main results are transferable to other engines and engine types, including quality-controlled engines. The first aspect of this paper is an analysis of the transition from fired to gas spring operation, and vice versa, as well as the gas spring operation itself. This is essential for mode changes, such as cylinder deactivation or skip-firing operation. Simulation results show that optimizing the valve timing in the last cycle before deactivating/first cycle after reactivating a cylinder, respectively, is advantageous. We further show that steady-state gas spring operation is reached after approximately 6 s regardless of the initial conditions and the engine speed. The second aspect of this paper experimentally verifies the advantage of optimized valve timings. Furthermore, we show measurements that demonstrate the occurrence of an unavoidable torque ripple, especially when the transition to and from the deactivated cylinder operation is performed too quickly. We also confirm with our experiments that a more gradual mode transition reduces the torque drop. [ABSTRACT FROM AUTHOR]

Cylinder deactivation is an effective measure to reduce the fuel consumption of internal combustion engines. This paper presents a control strategy for the cylinder deactivation (CDA) process and the cylinder reactivation (CRA) process, based on the inversion of a control-oriented discrete-event model. The focus of this paper lies on quantity-controlled stoichiometrically-operated engines with different layouts. Nevertheless, the main results are transferable to other engines, including quality-controlled engines. Two major aspects of CDA and CRA are considered in detail in this paper. The first aspect is the cycle-averaged torque during the CDA and CRA. Due to the reciprocating behaviour of the engine, an unavoidable discontinuity in the cycle-averaged torque is identified, irrespective of the type of engine. The amplitude of this torque ripple depends on the duration of the CDA or CRA and can be quantified a priori. A trade-off between the torque ripple amplitude and the CDA or CRA duration is identified. The second aspect is the amount of fuel consumed during the CDA and CRA. It is shown that to achieve a CDA or CRA with a limited torque ripple amplitude, some combustion cycles at unfavourable low-load conditions must occur. For example, ignition retardation might be used resulting in a significant portion of the fuel energy being lost. As a result an increase in the amount of fuel consumed during the CDA or CRA compared to that of continued operation in activated cylinder mode may arise. The conducted investigations show that this increase in fuel consumption is compensated after a few seconds of operation in the more fuel-efficient deactivated cylinder mode. [ABSTRACT FROM AUTHOR]