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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

This paper presents some of our various test data, newly developed testing method and valuable field data about reliability of Variable Geometry Turbine (VGT) turbocharger. Influential parameters are reviewed item by item. Establishing durability of VGT nozzle and link system is essential for developing VGT turbocharger. However that is not enough to achieve reliability target of VGT turbocharger system only since operating range and conditions of VGT turbocharger is different from conventional system. It was also necessary to optimize other components such as thrust bearing, sealing mechanism and compressor wheel etc. to severer conditions than conventional system.