1991-02-01

A Design and Experimental Study of an Otto Atkinson Cycle Engine Using Late Intake Valve Closing 910451

Previous work has established that part load fuel consumption of a spark ignition engine may be improved by means of both load control by Variable Valve Timing (VVT) and Variable Compression Ratio (VCR). The Otto-Atkinson cycle can be achieved by combining VVT with VCR. This paper explores the design aspects, production constraints and performance of such an engine, in which VVT is realised by Late Intake Valve Closing (LIVC).
The LIVC aspect of the chosen design makes use of two independently operated intake valves, such that variable dwell is obtained by phase control only of one of the valves. This allows a considerable degree of compatibility with a conventional 16 valve cylinder head. The first version of this design has been built and successfully tested.
A broad range of possible VCR design solutions has been analysed for performance and feasibility. Production constraints and a need for rapid transient response were identified as the main determining factors. The most promising option could be confined to the cylinder head, and has been built and demonstrated.

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