汽车专业英语+Unit+4讲解.ppt

汽车专业英语;Unit 4;Part A Overview of Engine Induction and Exhaust System;Try to remember them;Phrases and expressions;Text;Text;Text;Text;Text;Text;Text;New words，phrases and expressions;Try to remember them;Try to remember them;Try to remember them;Phrases and expressions;Text;Text;Text;Text;Text;Text; First, high EGR flow is necessary during cruising and mid-range acceleration，when combustion temperatures are typically very high． Second, low EGR flow is needed during low speed and light load conditions. Third, no EGR flow should occur during conditions when EGR operation could adversely affect engine operating efficiency or vehicle driveability (engine warm up, idle, wide open throttle, etc.) The EGR control valve is used to regulate exhaust gas flow to the intake system. The valve makes sure that the EGR system is off at idle, where it would lead to erratic and loping idle, and is open at loading, since adding exhaust gasses robs power from the engine.;EVAP（evaporative emission control） System Approximately 20% of all hydrocarbon(HC) emissions from the automobile originated from evaporative sources．The EVAP system is designed to store and dispose of fuel vapors normally created in the fuel system；thereby，preventing their escape to the atmosphere．This closed system separates fuel vapors and routes them back into the engine to be burned．When the engine is not running，a charcoal canister stores fuel vapors．Once the engine starts，engine vacuum draws vapors out of the canister and into the engine intake manifold．;Text;Text;Part C Dialogue;A：通常有三种情况排气警告灯会亮。一是某种随机原因引起的传感器误动作，可以采用专用电脑工具消去故障码；二是由于局部空气质量或燃油中的局部杂质引起的排放超标，这种情况很简单，你自己消去故障码就可以啦；最后一种情况也是最严重的一种，可能是发动机故障引起的排气系统报警。例如，排气系统中的氧含量过高，可能是用于控制的空气和燃油混合比引发的传感器故障，这种情况必须去修你的车。 B：如何区别这三种情况? A：一般来说，对于偶发性的报警，可以暂时排除第三种可能。但如果频繁报警，就应该考虑有可能是第三种情况，并及时进行专业检测、维修。 B：非常谢谢你。 A：我的荣幸。;再见