Nissan Diesel Motor Co.,LTD have developed a new turbocharged diesel engine with a variable nozzle turbocharger for the purpose of solving the contradictory problems of mobility and fuel economy, while meeting the 1990 Japanese emission standards. The heavy-duty trucks equipped with this new turbocharged engine have been released in the market recently. The variable nozzle turbocharger capable of maintaining sufficient turbine efficiency over the broad range of engine operating band was jointly developed with Allied Signal, Garrett Automotive Group in United States of America.It's control method, a stepless boost pressure feedback control system, was newly developed in order to make the most effective use of the turbocharger. As a result, the engine with stepless controlled variable nozzle turbocharger,when compared with a conventional fixed geometry turbocharger or a stepwise controlled variable nozzle turbocharger, showed better improvements with higher low speed torque, lower fuel consumption, quicker transient response and concentration smoke reduction while maintaining a low emission level. The engine with this new charge-air-system has received high appraisal in the market.