This report summarizes results from an invited two-day colloquium of twenty-nine combustion engine experts from academia, industry, and national labs that was convened March 3rd and 4th, 2010, at the headquarters of the United States Council for Automotive Research (USCAR) in Southfield, Michigan. The colloquium was held at the request of The Department of Energy (DOE) Office of Freedom Car and Vehicle Technologies (OFCVT) to review and assess the current state of transportation combustion engine technology from theoretical and practical perspectives. In the ensuing discussions, the experts were able to reach a broad consensus on some important questions regarding current fuel efficiency limits. They also identified technology barriers and recommended specific near and longer-term R&
D priorities for DOE's consideration. Internal combustion engines currently play a dominant role in U.S. transportation and are expected to continue to do so well beyond 2020 [1]. Because of this, the Department of Energy (DOE) has placed high priority on promoting technologies that maximize combustion engine fuel efficiency while minimizing greenhouse gas emissions. Identification of the most promising paths to achieve these goals has recently become more complicated as non-traditional transportation fuels and hybrid electric vehicles become widely available. To reassess the state of combustion engine science and identify new opportunities for technology breakthroughs, an invited colloquium of combustion engine experts was convened on March 3rd and 4th, 2010, at the headquarters of the United States Council for Automotive Research (USCAR) in Southfield, Michigan. The colloquium objectives were: (1) Review and assess the current state of transportation combustion engine technology from both theoretical and practical perspectives
(2) Arrive at a consensus on the theoretical and practical fuel efficiencies that can be achieved
and (3) Recommend near and longer-term R&
D priorities for DOE to consider in developing their strategic planning for reaching efficiency goals. This report summarizes the main discussion points and recommendations that emerged from the meeting. Included are areas where there is widespread consensus and areas where there are still important technical uncertainties and wide ranging opinions.