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A single cylinder direct injection gasoline engine has been developed and commissioned on a transient engine test bed in order to study different engine cycles and combustion modes with identical hardware and operating conditions. The engine can be operated in either 4-stroke cycle or 2-stroke cycle by means of an electro-hydraulic camless system. In addition, both spark ignition and controlled autoignition (CAI) combustion can be achieved. In this paper, effects of the injection timing on different CAI combustion modes are investigated, including the residual gas trapping and exhaust gas rebreathing CAI operations in 4-stroke mode, and also 2-stroke CAI operation, with a stoichiometric air fuel ratio and homogeneous charge used throughout. The performance and emission data are presented and analysed as a function of the injection timing. Results show that the charge cooling effect on the intake flow rate is dependent upon the in-cylinder temperature at the time of injection.

Over recent years, in order to develop more efficient and cleaner gasoline engines, a number of new engine operating strategies have been proposed and many of them have been studied on different engines but there is a lack of different comparison between various operating strategies. In this work, a single cylinder direct injection gasoline engine equipped with an electro-hydraulic valvetrain system has been commissioned and used to achieve seven different operation modes, which are 4-stroke throttle-controlled SI, 4-stroke intake valve throttled SI, 4-stroke positive valve overlap SI, 4-stroke negative valve overlap CAI, 4-stroke exhaust rebreathing CAI, 2-stroke CAI and 2-stroke SI. Their performance and emission characteristics are presented and discussed.