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The possibility of applying two types of raw materials which have transition elements such as B and Nb was investigated to develop new bearings which have metallurgical characteristics and fatigue resistance enhanced for advanced automotive transmissions which are known to supply severe lubrication environments. Those results were compared with the results of typical low carbon chromium steel which is widely used for the automotive transmission. Thrust type rolling contact fatigue testers were used for the evaluation of fatigue life of steel grades, and each specimen was tested under clean and contaminated lubrication environment. As a result, the microalloyed forging steels have shown the behavior of stabilized austenitic grain superior to comparative grade at high temperature regions. On the other hand, the test steels have shown a large amount of non-metallic microscopic inclusion or carbide segregation on near surface below the flaking.

A high-frequency ignition system was developed to improve the stability of initial flame development under the lean burn condition. The electrical principle of the high-frequency ignition system is based on successive spark discharges in a spark plug. The ignition system provides electronically controlled charges in spark duration (1∼2msec) and restriking rates (10∼30kHz). Flow characteristics of tumble-swirl were varied with swirl control valve attached at the inlet ports. Four different flow patterns were tested by the combination of tumble and swirl strengths achieved by various shapes of swirl control valve. The effects of flow and ignition characteristics on the combustion performances and their interaction were investigated in a 4-valve SI engine. Flow characteristics were quantified by steady flow tests and in-cylinder flow measurements.