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The paper describes the design and development of ‘Sabre’, a 3-cylinder engine encompassing a combination of technologies to realise low CO2 in a practical automotive application while retaining driving pleasure (vehicle acceleration performance). This project is a partnership with Continental Automotive, in which Lotus Engineering is responsible for the base engine and combustion system. The decision process that led to a close-spaced direct injection combustion system that does not target high BMEP as the chief route to low fuel consumption is described. Instead of pursuing an approach in which specific power is maximized in order to reduce throttling losses at part load, mild downsizing coupled with throttling loss reduction and turbulence manipulation enabled by a switching valve train is employed.

Electrohydraulic and electromechanical valve train technologies for four-stroke engines are emerging which allow much greater flexibility and control of the valve events than can be achieved using mechanically-based systems. Much of the work done on exploiting the benefits of these systems has been directed towards improving engine fuel economy and reducing emissions. In the present work a study has been made, using an engine simulation program, in to some of the possible benefits to engine performance that may be facilitated by the flexibility of fully variable valve train (FVVT) systems. The simulation study indicates that FVVT systems, limited by realistic opening and closing rates, provide sufficient range in the valve event duration and timing to enable the engine to produce very high specific outputs whilst achieving a high level of torque in the low- and mid-speed range.