單項選擇題During which of the listed piston stroke of a four-stroke/cycle diesel engine, is the piston moving downward?（）

A.Intake stroke
B.Compression stroke
C.Exhaust stroke
D.Pumping stroke


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1.單項選擇題A piston is at bottom dead center when it is（）

A.opening the exhaust ports
B.closing the fuel ports
C.farthest from the cylinder head
D.nearest to the cylinder head

2.單項選擇題The average pressure exerted on piston during each power stroke is termed（）

A.indicated horsepower
B.mean effective pressure
C.exhaust back pressure
D.compression pressure

3.單項選擇題If all other conditions such as bore, stroke, speed, and mean effective pressures are equal, a two-stroke/cycle diesel engine will develop approximately（）

A.the same indicated horsepower as a four-stroke/cycle engine
B.twice the indicated horsepower as a four-stroke/cycle engine
C.one half indicated horsepower as a four-stroke/cycle engine
D.one power stroke for every two crankshaft revolutions

4.單項選擇題In comparing engines of equal horsepower, higher exhaust gas temperatures occur in a/an（）

A.opposed-piston engine
B.double-acting engine
C.two-stroke/cycle engine
D.four-stroke/cycle engine

5.單項選擇題A disadvantage of a two-stroke/cycle diesel engine is（）

A.more power strokes per revolution
B.the use of scavenge air
C.more complicated valve gear
D.higher working temperature of the piston and cylinder