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a b s t r a c tThis paper focuses on the diversity of engine technologies for low emission vehicles (LEVs) that are developed by car manufacturers in order to substitute for the conventional internal combustion engine vehicle (ICEV). Our purpose is to analyse the competition between the various technologies for LEVs as well as the innovative strategy of car manufacturers. We first propose to define and to represent these technological trajectories in order to compare their performances and to identify their strengths and weaknesses. The technological bottlenecks, the barriers to the adoption of these alternative engine technologies as well as the features of this technological competition are underlined. We then use a patent data analysis to study the patent portfolios of the main car manufacturers in these technologies over the period [1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002][2003][2004][2005]. The dynamics of patent applications by car manufacturers gives insight on the competition among technologies and on the strategy of firms. This analysis emphasises the progressive diversification of firms' patent portfolios over the whole set of engine technologies and the differentiated strategic positioning of car manufacturers according to countries.