单项选择题
Which of the engine components listed increases air charge density and helps to improve engine operating efficiency?（）
A.Intake manifold B.Water-cooled exhaust system C.After-cooler D.Exhaust diffuser
单项选择题 A diesel engine will lose power if fuel injection occurs too early because the （）
单项选择题 The air supplied to the cylinders by a turbocharger is often reduced in volume by a/an （）
单项选择题 Which of the listed set of conditions indicates early fuel injection timing?（）
