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Various technologies for improving the environmental performance of vehicles have been vigorously developed in the automotive industry in recent years. In this regard, the core technologies for improving vehicle fuel economy are still mostly aimed at internal combustion engines. This paper presents a new variable displacement oil pump (VDOP) that was adopted for enhancing the fuel economy of a newly developed 1.2-liter three-cylinder supercharged gasoline direct injection engine. It describes the purpose, benefits, performance and variable displacement principle of the VDOP. Published papers concerning the development of the new engine, the friction reduction technologies it embodies and additional details of the mechanisms incorporated in the new oil pump are cited in the references for the further information of the reader.

Scope of this work is to analyse potentials in terms of efficiency of two pump units belonging to two families: the first intervening on the maximum volume generated by variable volume chambers (e.g. a vane pump where eccentricity is varied), the second that changes the quantity of fluid being sucked or delivered (e.g. a gear pump with variable timing). In more detail the comparison will be established between a vane pump where displacement is varied through eccentricity and an internal gear pump of Gerotor type where flow rate is controlled through a rotating sector that alters the effective geometry of kidney ports. A detailed simulation of the two solutions brings to evidence the advantages of the first approach with respect to the second as confirmed by experimental investigations.