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Recently, passenger cars require better acceleration from low engine speed including starting-up in order to decrease the amount of paticulate matter (PM) of diesel engines or to improve the driver's feeling. However, turbocharged cars generally have worse response than the non turbo cars because it takes a few seconds to get the turbocharger rotate up to high speed, usually called “Turbo-lag”. In order to solve this, various technologies have been developed for a turbocharger itself as well as for charging system such as the sequential system. Here in this paper, we focus on the development of the following turbocharger technology to reduce Turbo-lag and to achieve better transient response. 1. MIXED-FLOW TURBINE IMPELLER 2. TWIN ENTRY TURBINE HOUSING 3. BALL BEARING SYSTEM 4. SEPARATED THRUST BEARING SYSTEM

Turbochargers for vehicle use have been utilized for passenger cars and trucks to achieve high power, high torque, low fuel consumption and as a countermeasure for low emission of CO, HC, NOx, etc. Turbochargers are expected to play a major role in future to improve the performance of automobiles. Moreover, life of turbochargers has been increased steadily in spite of severe heat and stress condition due to requirement from engine manufactures. In case of truck use turbochargers, great efforts have been made to increase turbocharger life from 500,000 kms to 1,000,000 kms though the stress of the wheels has been raised due to increased boost pressure. Also, life of passenger-car use turbocharger has been increased in spite of higher exhaust gas temperature. This paper describes our experience of durability problems and our solution.