EXHAUST SYSTEM FOR ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust system for an engine capable of early activating a catalyst at a low temperature and preventing the deterioration of the catalyst at a high temperature by using a selecting means of a simple structure. SOLUTION: This exhaust system for an engine comprises a three-way catalyst 3a placed in an exhaust system of an engine, a front pipe 2 connected to the upstream of the three-way catalyst 3a and formed by approximately concentrically arranged inner pipe 2a and outer pipe 2b, and a valve element 5 switched to introduce the exhaust gas discharged from an engine to a space between the inner pipe 2a and the outer pipe 2b, and to the inner pipe 2a at a high temperature, and to introduce the exhaust gas discharged from the engine to the inner pipe 2a at a low temperature, and the valve element 5 is switched by expanding or contracting a part of the inner pipe 2a.