1. ABSTRACT:The exhaust emission gas regulations on truck diesel engines are becoming increasingly stringent in various countries in the coming years.The '94 EPA (U.S.A.) regulations include the entire working range of engines, including transient conditions; thus requiring a large-scale improvement in engine properties.For this reason, various engine components are now undergoing a series of improvements; in particular, the injection system has experienced a major renovation. However, the improvement of a naturally-aspirated engine has its own limit; and the turbocharged engine with inter-cooler becomes essential.Mitsubishi Heavy Industries has been pushing ahead with the development of turbochargers for use with the truck diesel engines. To assist the Diesel engine manufacture to meet these new emission regulations, we have developed various turbocharger options for improving engine performance, in addition to our continuing efforts for improving the aerodynamic properties.The TF07 model turbocharger has been the development target of our efforts. The TF07 model turbocharger applies to 6 to 9 liter truck diesel engines. The characteristics of the TF07 turbochargers and the effects of various options are explained in this paper.