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Ceramic honeycombs have been used as automotive catalytic supports in Europe. USA, Japan and other highly urbanized countries. (1)(2)(3) Maximising engine power output is of great interest to automotive manufacturers. Power output is partly dependant on the back pressure of the catalytic converter in the exhaust system. This paper discusses the use of a catalytic converter, designed to give a low pressure drop, that incorporates a ceramic catalytic support with low cell wall thickness. Further discussion concerns the canning techniques associated with this new substrate material, as well as converter durability and engine performance.

The effects of the factors of reverse pulse air regeneration; pulse air pressure, pulse air time and pulse air interval, were evaluated. Pulse air pressure significantly affects a DPF's pressure drop increase. Pulse air time and pulse air interval do not greatly affect a DPF's pressure drop. Current DPFs and samples with modified materials were tested. The pressure drop increse varied with the material properties, such as mean pore size and porosity. Current DPFs are applicable to a DPF system with reverse pulse air regeneration. There is the possibility to get an optimum DPF for the reverse pulse air regeneration system by changing the mean pore size, porosity and/or other properties.

A new type of catalytic converter has been developed for the coming TLEV (Transitional Low Emission Vehicle) standards. It is a “Front Curve Catalytic Converter (FCCC)” using a curved cordierite ceramic honeycomb substrate. During this development, an optimum location and volume of the front curve catalytic converter were determined from the view points of thermal deterioration of the catalyst and hydrocarbon conversion performance. Based on CAE (Computer Aided Engineering) analysis, the best curvature radius of the substrate was selected to minimize a pressure drop of the front curve catalytic converter. The emission conversion and light-off performances of the front curve catalytic converter were compared with a conventional straight design. A series of durability tests; hot vibration, engine dynamometer and vehicle fleet tests were also conducted to confirm the reliability of the new front curve catalytic converter.

Since the monolithic ceramic substrate was introduced for automotive catalytic converters, the reduction of the substrate wall thickness has been a continuing requirement to reduce pressure drop and improve catalytic performance. The thin wall substrate of 0.10 mm (4 mil) thick wall/400 cpsi cell density has been introduced to production by achieving mechanical strength equivalent to a conventional 0.15 mm (6 mil)/400 cpsi substrate. Although a round cross-section substrate can have a reduced catalyst volume compared to an oval cross-section substrate because of uniform gas flow distribution, the smaller cross-section of the round substrate increases pressure drop. The thin wall technology was applied to the round substrate to offset the pressure drop increase and to further improve catalytic performance.

The adoption of the diesel engine EGR systems, and increased uses of alcohol in spark ignited engines require wear resistant and low maintenance valve trains. Silicon nitride ceramic inserts were pressureless-sintered and successfully die-cast in rocker arms contacting the overhead cams in the valve trains. As fired, the insert sliding surface was fine and precise, eliminating any further processing. The comosite structure was machined with the sliding surface as a reference plane. Beside inherent high wear resistance, these lighter inserts reduced inertial forces of the trains and the torque required to drive the cams. The hard, brittle ceramics and a softer, more elastic aluminum alloy made the structure more durable and reliable. The process of development includes characterization, screening, manufacturing and quality control of the materials, and determination of wear resistance and reliability for this new structure.