单项选择题 An operating turbocharged diesel engine that suddenly loses power, is due to a/an（）

单项选择题 The exhaust valve opens before bottom dead center in a four stroke engine to（） Ⅰ.allow for blow down Ⅱ.Reduce pumping losses

单项选择题 Which of the turbo-charging systems listed operates with the least average back pressure in the exhaust manifold?（）