Abstract
Future diesel engines for heavy-duty trucks are required to have significantly low NOx, PM, and fuel consumption characteristics. In order to improve those, various technologies including high pressure fuel injection systems, combustion optimization, high boost pressure turbocharging, EGR, homogeneous charge compression ignition combined with multiple injections, and aftertreatment are discussed. As each technology has a number of challenges to overcome, it will take long before engines with those technologies are commercially available. In this paper, the research activities accomplished to date are reported.