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Variable Valve Timing (VVT) has been demonstrated by other authors as a means of improving engine performance and idle quality. The possibility of improving fuel economy as well with VVT is investigated here. The effect of VVT on the mechanical efficiency of the engine is a crucial design factor affecting fuel economy. A number of concepts are evaluated with experimental and computer modelling results. Among these, Late Intake Valve Closing (LIVC) is shown to be a practical concept applicable to engines with two intake valves per cylinder where the intake valves can be phased relative to each other to extend the total intake opening period.