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A wall-flow honeycomb filter comprising a ceramic monolith having a plurality of porous walls formed therein. The plurality of porous walls define a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith. The inlet cells ar

A wall-flow honeycomb filter comprising a ceramic monolith having a plurality of porous walls formed therein. The plurality of porous walls define a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith. The inlet cells are open at the inlet end face and plugged at or near the outlet end face. The outlet cells are open at the outlet end face and plugged at or near the inlet end face. The monolith has a ratio of a combined cross-sectional area of the inlet cells to a combined cross-sectional area of the outlet cells greater than 1. The monolith has at least one inlet cell cluster which contains an N×M group of inlet cells, N and M being integers greater than 1, each inlet cell cluster consisting of a plurality of inlet cells separated by inlet cluster walls.

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1. A wall-flow honeycomb filter comprising: a ceramic monolith having a plurality of porous walls formed therein, the plurality of porous walls defining a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith along a Z axi

1. A wall-flow honeycomb filter comprising: a ceramic monolith having a plurality of porous walls formed therein, the plurality of porous walls defining a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith along a Z axis, the inlet cells being open at the inlet end face and plugged at or near the outlet end face, the outlet cells being open at the outlet end face and plugged at or near the inlet end face;the monolith having a ratio of a combined cross-sectional area of the inlet cells to a combined cross-sectional area of the outlet cells greater than 1;wherein inlet cells (I) and outlet cells (O) are arranged along an X and Y axis, wherein the X and Y axis are both orthoganol to the Z axis, in the following repeating pattern: wherein the arrows indicate the X axis and the Y axis. 2. A method of making a wall-flow honeycomb filter according to claim 1, comprising: providing a wall-flow honeycomb filter comprising a ceramic monolith having a plurality of porous walls formed therein, the plurality of porous walls defining a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith, the inlet cells being open at the inlet end face and plugged at or near the outlet end face, the outlet cells being open at the outlet end face and plugged at or near the inlet end face;the monolith having a ratio of a combined cross-sectional area of the inlet cells to a combined cross-sectional area of the outlet cells greater than 1; and,the monolith having at least one inlet cell cluster which is cross-shaped, each inlet cell cluster consisting of a plurality of inlet cells separated by inlet cluster walls, inlet cells (I) and outlet cells (O) being arranged along an X and Y axis, wherein the X and Y axis are both orthoganol to the Z-axis, in the following repeating pattern: wherein the arrows indicate the X axis and the Y axis;applying a washcoat comprising active catalytic species to at least one inlet cluster wall;wherein the washcoat applied to at least one inlet cluster wall is different form washcoats applied to porous walls that are not within a cluster of inlet cells. 3. The method of claim 2, wherein applying a washcoat to an inlet cluster wall comprises dipping the monolith into a slurry of the washcoat comprising active catalytic species from the inlet end face of the monolith. 4. The wall-flow honeycomb filter of claim 1, wherein at least a portion of the inlet cell cluster walls is loaded with a washcoat comprising active catalytic species. 5. The wall-flow honeycomb filter of claim 4, wherein the inlet cluster walls have a higher loading of the washcoat than the cell walls external to the inlet cell clusters. 6. The wall-flow honeycomb filter of claim 4, wherein the inlet cluster walls are loaded with a different catalytic species than the cell walls external to the inlet cell clusters. 7. The wall-flow honeycomb filter of claim 4, wherein a porosity of the inlet cluster walls is different from a porosity of the cell walls external to the inlet cell clusters. 8. The wall-flow honeycomb filter of claim 1, wherein the inlet cluster walls are thinner than the cell walls external to the inlet cell clusters. 9. A wall-flow honeycomb filter comprising: a ceramic monolith having a plurality of porous walls formed therein, the plurality of porous walls defining a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith along a Z axis, the inlet cells being open at the inlet end face and plugged at or near the outlet end face, the outlet cells being open at the outlet end face and plugged at or near the inlet end face;the monolith having a ratio of a combined cross-sectional area of the inlet cells to a combined cross-sectional area of the outlet cells greater than 1;wherein inlet cells (I) and outlet cells (O) are arranged along an X and Y axis, wherein the X and Y axis are both orthoganol to the Z axis, in the following repeating pattern: wherein the arrows indicate the X axis and the Y axis. 10. The wall-flow honeycomb filter of claim 9, wherein at least a portion of the inlet cell cluster walls is loaded with a washcoat comprising active catalytic species. 11. The wall-flow honeycomb filter of claim 10, wherein the inlet cluster walls have a higher loading of the washcoat than the cell walls external to the inlet cell clusters. 12. The wall-flow honeycomb filter of claim 10, wherein the inlet cluster walls are loaded with a different catalytic species than the cell walls external to the inlet cell clusters. 13. The wall-flow honeycomb filter of claim 10, wherein a porosity of the inlet cluster walls is different from a porosity of the cell walls external to the inlet cell clusters. 14. The wall-flow honeycomb filter of claim 9, wherein the inlet cluster walls are thinner than the cell walls external to the inlet cell clusters. 15. A method of making a wall-flow honeycomb filter according to claim 14, comprising: providing a wall-flow honeycomb filter comprising a ceramic monolith having a plurality of porous walls formed therein, the plurality of porous walls defining a plurality of inlet cells and a plurality of outlet cells extending between an inlet end face and an outlet end face of the monolith, the inlet cells being open at the inlet end face and plugged at or near the outlet end face, the outlet cells being open at the outlet end face and plugged at or near the inlet end face;the monolith having a ratio of a combined cross-sectional area of the inlet cells to a combined cross-sectional area of the outlet cells greater than 1; and,the monolith having at least one inlet cell cluster which is cross-shaped, each inlet cell cluster consisting of a plurality of inlet cells separated by inlet cluster walls, inlet cells (I) and outlet cells (O) being arranged along an X and Y axis, wherein the X and Y axis are both orthoganol to the Z-axis, in the following repeating pattern: wherein the arrows indicate the X axis and the Y axis; and,applying a washcoat comprising active catalytic species to at least one inlet cluster wall; wherein the washcoat applied to at least one inlet cluster wall is different from washcoats applied to porous walls that are not within a cluster of inlet cells.