单项选择题
Ring groove inserts are occasionally used on aluminum alloy piston to（）
A.reduce the ring groove wear rate B.seal against crankcase vapors C.lessen the wear on aluminum part of the cylinder D.allow for the greater expansion rate of aluminum
单项选择题 A sudden drop in diesel engine cylinder compression pressure can be caused by（）
单项选择题 Which of the following statements is correct for the design and installation of diesel engine cooling water systems?（）
单项选择题 High exhaust back pressure will result in an increase in （）
