| abstract |
Provided is an exhaust system for a positive ignition internal combustion engine that operates at a stoichiometric air-fuel ratio of a vehicle but is suitable for lean combustion. A wall flow filter (20) for filtering particulate matter of exhaust gas exhausted from an internal combustion engine, the filter includes a porous substrate having an inlet surface and an outlet surface, the inlet surface being a first average The porous structure of the coated porous substrate is separated from the exit surface by a porous structure containing pores having a pore size, and the porous substrate is coated with a three-way catalyst washcoat containing a large number of solid particles Has a second average pore size, the second average pore size is smaller than the first average pore size, and the three-way catalyst 18 washcoat is located upstream of the filter. The exhaust system 10 formed above, wherein the mass of the three way catalyst washcoat on the upstream substrate monolith is 75% or less of the total weight of the three way catalyst washcoat [Selection] Figure 5 |