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Gasoline engine downsizing is already established as a proven technology to reduce automotive fleet CO₂ emissions. Further real-world benefits are possible through more aggressive downsizing; however, there is a trade-off between maintaining a high compression ratio for good part load fuel consumption and maintaining optimal combustion phasing at higher loads. There are many different technologies, which could be applied to gasoline-downsized engines in order to improve efficiency. One is to adopt a Miller/Atkinson cycle, which uses variable valve timing to reduce throttling losses in part load operation and reduce effective compression ratio to optimize combustion phasing at higher loads. MAHLE Intake CamInCam® is a technology enabler for Miller/Atkinson cycle operation. It uses asymmetric intake valve timing control to effectively provide a method of running increased intake cam duration allowing Late Intake Valve Closing cycle strategies to be adopted.

This experimental work was concerned with the combination of internal EGR with an early inlet valve closure strategy for improved part-load fuel economy. The experiments were performed in a new spark-ignited thermodynamic single cylinder research engine, equipped with a mechanical fully variable valvetrain on both the inlet and exhaust. During unthrottled operation at constant engine speed and load, increasing the mass of trapped residual allowed increased valve duration and lift to be used. In turn, this enabled further small improvements in gas exchange efficiency, thermal efficiency and hence indicated fuel consumption. Such effects were quantified under both port and homogeneous central direct fuel injection conditions. Shrouding of the inlet ports as a potential method to increase in-cylinder gas velocities has also been considered.

In recent times regulatory pressure to reduce CO2 emissions has driven research towards looking at blending fossil fuels with alternatives such as crop-produced alcohols. The alcohol of interest in this paper is ethanol and it was studied in mixtures with gasoline and iso-octane in an optical spark-ignition engine, running at 1500 RPM at low-load operation with 0.5 bar absolute intake plenum pressure. Specifically, tests involved fuels of 100% gasoline and 100% iso-octane, so that differences between multi and single-component fuels could be compared within this environment. A mixture of 25% ethanol with 75% iso-octane was also tested and compared. Finally, mixtures of high-percentage of ethanol (85% ethanol) in gasoline and in iso-octane were used in the study and compared. Tests were undertaken using a standard port injection system as well as a direct injection system so an appraisal of both mixture preparation methods could be made.