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Gasoline HCCI engine has the potential of providing better fuel economy and emissions characteristics than the current SI engines. However, management of HCCI operation for a vehicle is a challenging task. In this paper, the issues of mode transitions between the Spark Ignition and HCCI regimes, and the dynamic nature of the load trajectory within the HCCI regime are considered. Then the phenomena encountered in these operations are illustrated by the data from a single-cylinder engine with electromagnetic-variable-valve timing control. Mode transitions from the SI to HCCI regime may be categorized as robust and non-robust. In a robust transition, every intended HCCI cycle is successful. In a non-robust transition, one or more intended HCCI cycles misfire, although the cycles progress to a satisfactory HCCI operating point in steady state. (The spark ignition was kept on so that the engine could recover from a misfired cycle.)

Homogeneous-Charge-Compression-Ignition (HCCI) engine operation in a vehicle drive cycle is a very dynamic process. In this paper, a controller is devised on the premise that the vehicle is operating under Drive-By-Wire so that the driver commands the engine torque output according to the perceived vehicle speed. Thus a load-following controller is appropriate. Such a controller was developed for a single cylinder engine with electromagnetic variable valve timing control (also known as Controlled-Auto-Ignition (CAI) operation). Under open-loop operation within the CAI regime, the results indicated that the engine response was bipolar in nature: (a) the engine either responded quasi-statically to the open-loop control, or (b) the CAI combustion failed. The latter happened in a load increase process in which the per-cycle increment was too high.