发动机冷起动阶段混合气较浓,未燃烧的碳氢化合物及一氧化碳等有害物质排放相对较高,并且此时,三元催化转化器尚未达到正常工作温度(300℃以上),为了降低发动机冷起动阶段有害物质的排放,同时再次燃烧的热量也使三元催化转化器很快能达到所需的工作温度,普遍采用二次空气喷射系统。该系统通过向废气中吹进额外的空气 In the cold start phase of the engine, the mixture is rich, and harmful substances such as unburned hydrocarbons and carbon monoxide are emitted relatively high, and at this time, the three-way catalytic converter has not yet reached the normal operating temperature (above 300 ° C.). In order to reduce engine cold start Phase of harmful emissions, while re-burning the heat also enables three-way catalytic converter can quickly reach the desired operating temperature, the widespread use of secondary air injection system. The system pulls extra air into the exhaust