Leaky exhaust valve will result in which of the following？①high exhausttemperature ②low compression ③low firing pressure

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• （）is harmful for fuel pumps, fuel valves, cylinder liner, exhaust valve seats, and the turbocharger blades as well.

  A . Bad combustion of the fuel B . Bad atomization of the fuel C . Liquid contaminants D . Solid contaminant

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• For an ordinary four-stroke engine the exhaust valves open （）.

  A . after TDC B . before TDC C . after BDC D . before BDC

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• The loss of the diesel engine cylinder air charge through leaky valves, piston rings, worn or scored liners, would be indicated by which of the following sets of conditions?（）

  A . Low compression pressure and high exhaust temperature B . Low firing pressure and high exhaust temperature C . Low compression pressure and low exhaust temperature D . Low firing pressure and low exhaust temperature

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• During the valve overlap period, the exhaust pressure of a turbochargers, four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure （）

  A . effective cylinder scavenging and cooling B . constant pressure from the turbochargers C . cooler operation of the exhaust system D . effective constant pressure for turbocharger operatio

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• In an engine with air inlet valve and exhaust valve on its cylinder heads the fresh air will enter into the cylinder （） and the gases exhaust （）, there being an adequate overlap between the inlet opening and the exhaust closing.

  A . downwards；upwards B . upwards；downwards C . downwards；downwards D . upwards；upward

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• A ruptured diaphragm in a thermostatic expansion valve will cause the valve to （）.

  A . open B . close C . remain in its position D . flood the evaporator with refrigerant

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• A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) MEP is lower and the scavenging air is cooling the exhaust gases (2) valve overlap in a four-stroke

  A . (1) only is correct B . (2) only is correct C . both (1) and (2) are correct D . Neither (1) or (2) are correct

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• The exhaust valve opens before bottom dead center in a four stroke engine to（） Ⅰ.allow for blow down Ⅱ.Reduce pumping losses

  A . Ⅰ only B . Ⅱ only C . both Ⅰ and Ⅱ D . neither Ⅰ nor Ⅱ

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• Increasing the valve clearance between a valve stem and rocker arm, will result in the valve （）

  A . closing later B . opening sooner C . staying open for a shorter period of time D . staying open for a longer period of time

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• High exhaust back pressure will result in an increase in （）

  A . turbocharger efficiency B . engine power output C . carbon deposits on fuel injectors D . cylinder scavenging

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• The satisfactory operation of diesel engine exhaust valves usually depends on（）

  A . the proper back pressure B . the cooling water temperature C . correct timing and proper seating D . accurate metering and the exhaust temperature

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• The opening of an exhaust valve on a modem, large, low-speed, main propulsion diesel engine may be actuated by （）.

  A . direct action of cam shaft B . compressed air pressure C . hydraulic “push rods” D . direct action of the main piston moving dow

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• If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.

  A . open；short；after B . closed；short；after C . open；long；before D . closed；long；before

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• In a diesel engine exhaust system, the cooling of the exhaust gases below their dew point, will result in （）

  A . increased engine back pressure B . sulfuric acid corrosion C . surface pitting of the turbocharger D . moisture impingement on the turbocharger compressor blade

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• For an ordinary four-stroke diesel engine the exhaust valves close （）.

  A . after TDC B . before TDC C . after BDC D . before BDC

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• A substance found in residual fuels which tends to cause exhaust valve corrosion and grooving, is（）

  A . carbon B . vanadium C . calcium D . hydroge

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• In a diesel engine, exhaust valves open before the intake ports are uncovered to （） Ⅰ.reduce pumping losses Ⅱ.reduce back pressure

  A . Ⅰonly B . Ⅱonly C . bothⅠand Ⅱ D . neitherⅠnor Ⅱ

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• 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 spring

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• Leaky exhaust valve will result in which of the following?（） (1) high exhaust temperature; (2) low compression pressure; (3) low firing pressure.

  A . (1) and (2) B . (1) only C . (2) only D . (1),(2) and (3)

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• A dry-type exhaust muffler clogged with soot, will cause（）

  A . low exhaust temperature B . loss of engine power C . burned intake valves D . engine racing

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• A built-up exhaust valve is one in which （）.

  A . the stem and heads are made of different material B . low-alloy steel is used throughout C . a replaceable valve disk is welded to the head D . the self-centering action comes from motion of the valve stem in the guide

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• In an ordinary four-stroke engine the exhaust valves open （）

  A . after TDC B . before TDC C . after BDC D . before BDC

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• In a turbocharged four-stroke/cycle diesel engine, the exhaust valve remains open until after top dead center and the intake valve opens before top dead center to_______.

  A.produce a scavenging effect in the combustion space B.equalize cylinder and exhaust manifold pressures C.alleviate the difference in valve size between the intake and exhaust D.flush out condensate that collects after each compression stroke

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• The exhaust valve opens before bottom dead center in a four stroke engine to______Iallow for blow down IIReduce pumping losses

  A.I only B.II only C.both I and II D.neither I nor II

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