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To reduce flow restriction of the wall flow type diesel particulate filters, the pore size distribution of DPF material was improved. Large pore material is preferred to reduce the flow restriction of the DPF. However pore diameter should be controlled within a certain limit to maintain high trapping efficiency against diesel particulates. In order to solve these conflicting matters, the mean pore diameter was enlarged from 13μm of the current material to 20 μm or more, while maintaining the cumulative volume of pores above 100μm within 8% of the total pore volume. The safe limit against thermal shock failure of the improved DPF material having 9″D x 12″/, 12.5/ volume was also determined using diesel burner regeneration system.

Silicon nitride (SN) valves promise significant reductions in weight and inertial force for valve trains because they are only two-fifths the weight of equivalent metal versions. This study evaluates how the higher engine speeds and lower valve spring loads that they permit contribute to higher engine output and greater fuel economy. It also evaluates their reliability in the presence of valve bounce and other adverse conditions that ceramic valves normally fail to withstand. For this purpose, material studies, actual engine tests and finite element method (FEM) analysis were conducted. Long-term durability tests revealed that SN valves are capable of providing the necessary resistance to breakage.