单项选择题
A.bottom-blow valve
B.skin valve
C.feed-check valve
D.feed-stop valve
单项选择题 The mechanical exhaust valve operation system is replaced by（）in an electronic controlled ME engine.
单项选择题 （）is not a feature of the electronic controlled engines.
单项选择题 If a camshaft-less engine has a normal injection pressure at rated speed, the injection pressure will be at slow speed（）