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This paper proposes a development of “Low Light-off Three Way Catalyst” and results by evaluation with a high density thin wall substrate such as 1.0×10-4m / 9.3×105cells/m2 (4mil/600cpsi) and 5.1×10-5m / 1.4×106cells/m2 (2mil/900cpsi). For development of “Low Light-off Three Way Catalyst”, the material components were improved. For example, 1) three kinds of precious metals, 2) Pr compound to improve the oxygen storage performance at low temperature of cerium oxides, 3) Ba for thermal stabilizer to prevent from the sintering of precious metals. To optimize these three factors, the developed catalyst could lower 90K light-off performance and C773 NOx was improved 15% to compare with current Pt/Rh catalyst after 1373K, 24h thermal aging. And by the vehicle test, tail pipe emission could be improved about 23% and 10% for HC and NOx conversion performance respectively. And substrate structure is one of the factors to improve the catalyst performance.

An all-ceramic swirl chamber combined with an air gap has been developed, and methods have been established to assure its durability and quality. Materials and configurations of the swirl chamber components were selected to demonstrate long-term durability. And improving manufacture and inspection procedures has helped achieve high reliability of the swirl chamber.

An all-ceramic swirl chamber has been developed and analyses and evaluations concerning the strength of silicon nitride ceramic (Si3N4) have been performed with a view to using it for the entire internal wall surface of the swirl chamber. The strength characteristics of Si3N4 and their effect and variation have been determined. On the basis of measurements and analyses of thermal stresses, assembling stresses, etc., investigation of the most suitable construction and assembling methods to reduce load stresses on ceramic, and various kinds of duration tests, the swirl chamber has been confirmed to have the required durability. This engine was found to comply with the 1987 U.S. diesel particulate regulation.