單項選擇題The size of the exhaust valve opening is （）

A.most critical in a four-stroke cycle diesel engine
B.most critical in a two-stroke/cycle diesel engine
C.most critical in a four-stroke/cycle diesel engine if it is turbocharged
D.of equal importance in a two-stroke/cycle diesel engine as in a four-stroke/cycle diesel engine


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1.單項選擇題If the piston groove drain holes for the oil control rings become clogged, which of the following is likely to occur?（）

A.The oil control rings will seal improperly and wear rapidly
B.The piston will overheat due to insufficient lubrication
C.Excessive oil will remain on the cylinder wall
D.Light brown smoke will emanate from the engine exhaust

2.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

3.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

4.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

5.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