单项选择题Cold clearances between the skirt of an aluminum piston and the cylinder liner is about ()

A.twice as large as with a cast iron piston
B.the same size as with a cast iron piston
C.half as large as with a cast iron piston
D.the same size as the crown of an aluminum piston


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1.单项选择题Exhaust valve openings in a diesel engine cylinder head are made as large as practical to ()

A.increase back pressure during the exhaust process
B.facilitate periodic replacement of the valves
C.reduce the pumping loss associated with scavenging
D.reduce tension on valve springs

2.单项选择题If the compression rings on a diesel engine piston become stuck in the ring groove, the cause may be due to()

A.excessive ring action
B.excessive ring temperature
C.improper ring rotation
D.excessive ring face wear

4.单项选择题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

5.单项选择题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

6.单项选择题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

7.单项选择题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

8.单项选择题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

9.单项选择题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

10.单项选择题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