Exhaust gas-purifying system for internal combustion engines

摘要

An exhaust gas-purging system for an internal combustion engine includes a catalyst arranged in an exhaust passage of the engine, for purifying exhaust gases emitted from the engine. The system detects an engine operating condition and a catalyst temperature parameter indicative of the temperature of the catalyst. The supply of secondary air to the exhaust passage and the flow path cross-sectional area of the exhaust passage are controlled based on at least one of the operating condition of the engine and the catalyst temperature parameter.