單項選擇題Turbocharged four-stroke/cycle diesel engines utilize valve overlap for（）.

A.improving cylinder scavenging
B.preheating the combustion chamber
C.reducing air charge density
D.preventing valve wear


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1.單項選擇題Operating a propulsion diesel engine at less than 30% of designed normal load for prolonged periods will result in （）.

A.decreased fuel consumption per brake horsepower
B.more complete cylinder scavenging
C.extended valve life
D.carbon formation on combustion chamber surfaces

2.單項選擇題A dirty fuel oil filter element can be detected by （）

A.Visual inspection of the element
B.the pressure drop cross the filter
C.high fuel oil tank temperature
D.increase flow rate from the filter

3.單項選擇題The major cause of fuel pump and injection system problems is （）

A.improper adjustments
B.contaminated fuel
C.kinked fuel lines
D.excessive engine vibration

4.單項選擇題A diesel engine should not be operated at low loads for long periods of time because（）

A.heavy carbon deposits will buildup on the valves and in the exhaust
B.fuel dilution is increased at low load
C.exhaust valves may be damaged
D.all of the above

5.單項選擇題Diesel engine fuel oil contamination often results in （）

A.governor malfunctions
B.fuel injection system malfunctions
C.high cylinder lube oil temperatures
D.low intake temperatures