單項選擇題Many cast iron pistons are designed with heat dams, which serve to （）

A.keep piston crown temperatures elevated for smoother combustion
B.reduce the possibility of overheating the top compression ring
C.help retain the heat of compression to prevent ignition delay
D.help retain the heat of compression to prevent combustion knock


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1.單項選擇題The adverse effects of burning high sulfur fuel can be compensated for by using a cylinder oil having sufficient（）

A.dispersant additives
B.floc point
C.alkalinity additives
D.ignition quality

2.單項選擇題Scuffed cylinder liner surfaces in a diesel engine can result form（）

A.starting the engine hot
B.knurling the piston skirt
C.operating an overheated engine
D.using scuff resistant piston rings

3.單項選擇題When comparing different fuels for different engines, the ignition quality of diesel fuel oils becomes a less critical consideration as （）

A.the amount of lube oil additives increase
B.piston speeds increase
C.injection pressure decrease
D.engine speeds decrease

4.單項選擇題To reduce the weight of the reciprocating parts, pistons of high-speed engines are made considerably shorterThis results in （）

A.less piston slap and quieter running
B.increased crankshaft bearing wear
C.slightly greater piston wear
D.decreased side pressures

5.單項選擇題Which of the following statements concerning cylinder liner wear is true?（）

A.Liner wear is distributed equally between the upper and lower portions of the cylinder
B.Excessive liner wear causes wear between piston ring and groove
C.Excessive, but uniform liner wear will not cause wear between piston ring and groove
D.Liner wear is normally greatest in the middle of the cylinder