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It is necessary to mount a three-way catalyst at a place near the engine such as a close coupled converter or manifold converter to decrease cold-start emission. Naturally, in that case the catalyst of course is used under considerable A/F fluctuations at higher temperatures. We have developed a catalyst with excellent durability under such severe conditions. Three types of catalysts, made with different loading locations of precious metals, were evaluated using model gases. Durability was found to strongly depend on the loading location, and thus it should be possible to design an optimal catalyst for close coupled and manifold converters.

The catalytic performance and On-Board Diagnostics (OBD) of the manifold catalyst having high Oxygen Storage Capacity (OSC) are described in this paper. First of all, we compared the performance of three-way catalysts containing Cerium - Zirconium - Yttrium oxide with Cerium - Zirconium oxide. Three-way catalysts dispersed Pt, Rh and Pd on Cerium - Zirconium - Yttrium oxide showed excellent catalytic performance especially at cold starting and at transient states, after high temperature aging at 1050°C. The performance of these catalysts was studied using the Driving Mode Simulation Dynamometer, which was developed in-house, and oxygen storage and release responses were compared in actual gas. Then we investigated the possibility of on-board diagnostics of catalyst deactivation with high OSC in manifold and close-coupled positions, a diagnostic which is usually assumed to be difficult to attain with present conventional technology.

We have succeeded in applying a new injection molding method, die rotary injection (DRI), for plastic intake manifold production. Polyamide 6 and polyamide 66 are the optimum materials with consideration of the mechanical properties and the durability against heat and chemicals. Though the conventional plastic manifolds are mostly made by polyamide 66, polyamide 6 showed preferable characteristics for the injection welding technology that we have developed. Measurement of welding strength and observation of fracture surface were carried out by using specimens that were cut from the real products. High welding strength without delamination of the welding surface was confirmed in the molding condition up to high cylinder temperature and high injection rate.