Exhaust and control method for an internal combustion engine having an exhaust bypass

摘要

An exhaust system for an internal combustion engine comprises an exhaust bypass (7) in parallel with an upstream portion of a main exhaust path (3) having a main catalytic converter (4) in a downstream portion thereof; an exhaust bypass catalytic converter (8) provided in the exhaust bypass (7); and a flow path switching valve (5) for blocking the main exhaust path (3) at the upstream portion thereof. The exhaust system includes an ignition timing adjustment mechanism for adjusting ignition timing to delay sparking when the flow path switching valve (5) is switched from the closed condition to the open condition thereof. A control method for the exhaust system is also disclosed.