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This paper describes the concept, analysis and preliminary rig proving of a 2-mode mechanical variable-valve-actuation system, “Latchcam”, designed initially for prototype bucket-tappet overhead-cam applications. The rig-test data allows the prototype Latchcam performance to be compared to a state-of-art 2-mode system in a current cylinder-head application. Some general design implications and issues are reviewed.

A review is made of the part and full load behaviour of several high compression ratio compact combustion chambers. Comparisons are made with current moderate compression ratio quiescent and fast burn combustion chambers. Typical vehicle fuel consumptions are projected for the various chamber types at similar vehicle performance and emission levels. Measured vehicle results with experimental combustion systems are indicated. The underlying reasons for the part load fuel consumption improvements of both high compression compact and fast burn open chambers are examined in terms of burn rate and friction.