IC Engine MCQ Objective Question and Answers Part 3

Internal Combustion Engine ( IC Engine ) Multiple Choice Question and Answers , MCQ Objective Question for Mechanical Engineering

IC Engine MCQ Objective : Part 1 | Part 2 | Part 3

68. Engine pistons are usually made of aluminium alloy because it
(a) is lighter
(b) wears less
(c) absorbs shocks
(d) is stronger
(e) does not react with fuel and lub oil.
Ans: a

69. Most high speed compression engines operate on
(a) Otto cycle
(b) Diesel cycle
(c) Dual cycle
(d) Carnot cycle
(e) Two stroke cycle.
Ans: c

70. The specific fuel consumption of a petrol engine compared to diesel engine of same H.P. is
(a) same
(b) more
(c) less
(d) less or more depending on operating conditions
(e) unpredictable.
Ans: b

71. A diesel engine as compared to petrol engine (both running are rated load) is
(a) more efficient
(b) less efficient
(c) equally efficient
(d) unperdictable
(e) other factors will decide it.
Ans: a

72. The size of inlet valve of an engine in comparison to exhaust valve is
(a) more
(b) less
(c) same
(d) more/less depending on capacity of engine
(e) varies from design to design.
Ans: b

74. In a cycle, the spark lasts roughly for
(a) 1 sec
(b) 0.1 sec
(c) 0.01 sec
(d) 0.001 sec
(e) 0.0001 sec.
Ans: d

75. Which of the following is false statement :
Excess quantities of sulphur in diesel fuel are Objectionable because it may cause the following
(a) piston ring and cylinder wear
(b) formation of hard coating on piston skirts
(c) oil sludge in the engine crank case
(d) detonation
(e) forms corrosive acids.
Ans: d

76. Which of the following is false statement. Some of the methods used to reduce diesel smoke are as follows
(a) using additives in the fuel
(b) engine derating i.e. reducing the maxi-mum flow of fuel
(c) increasing the compression ratio
(d) adherence to proper fuel specification
(e) avoidance of overloading.
Ans: c

77. The fuel air ratio in a petrol engine fitted with suction carburettor, operating with dirty air filter as compared to clean filter will be
(a) higher
(b) lower
(c) remain unaffected
(d) unpredictable
(e) none of the above.
Ans: a

78. Pick up the wrong statement about supercharging
(a) supercharging reduces knocking in diesel engines
(b) there can be limited supercharging in petrol engines because of detonation
(c) supercharging at high altitudes is essential
(d) supercharging results in fuel economy
(e) supercharging is essential in aircraft engines.
Ans: d

79. The actual volume of fresh charge admitted in 4-stroke petrol engine is
(a) equal to stroke volume
(b) equal to stroke volume and clearance volume
(c) less than stroke volume
(d) more than stroke volume
(e) more than cylinder volume.
Ans: c

80. The magneto in an automobile is basically
(c) transformer
(b) d.c. generator
(c) capacitor
(d) magnetic circuit
(e) a.c. generator.
Ans: b

81. The reason for supercharging in any engine is to
(a) increase efficiency
(b) increase power
(c) reduce weight and bulk for a given out-put
(d) effect fuel economy
(e) none of the above.
Ans: c

82. The operation of forcing additional air under pressure in the engine cylinder is known as
(a) scavenging
(b) turbulence
(c) supercharging
(d) pre-ignition
(e) dissociation and carburetor of fuel.
Ans: c

83. Supercharging is essential in
(a) diesel engines
(b) gas turbines
(c) petrol engines
(d) aircraft engines
(e) marine engines.
Ans: d

84. The minimum cranking speed in case of petrol engine is about
(a) half the operating speed
(b) one-fourth of operating speed
(c) 250-300 rpm
(d) 60-80 rpm
(e) 10-20 rpm
Ans: d

85. In a typical medium speed 4 stroke cycle diesel engine
(a) exhaust valve opens at 35° before bot-tom dead center and closes at 20° after top dead center
(b) exhaust valve opens at bottom ‘dead center and closes at top dead center
(c) exhaust valve opens just after bottom dead center and closes just before top dead center
(d) may open and close anywhere
(e) none of the above is true.
Ans: a

86. Flash point of fuel oil is
(a) minimum temperature to which1 oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame
(b) temperature at which it solidifies or congeals
(c) temperature at which it catches fire without external aid
(d) indicated by 90% distillation temperature, i.e. when 90% of sample oil has distilled off
(e) none of the above.
Ans: a

87. The mean effective pressure obtained from engine indicator indicates the
(a) maximum pressure developed
(b) minimum pressure
(c) instantaneous pressure at any instant
(d) exhaust pressure
(e) average pressure.
Ans: e

88. For the same power developed in I.C. engines, the cheaper system is
(a) naturally aspirated
(b) supercharged
(c) centrifugal pump
(d) turbo charger
(e) none of the above.
Ans: b

89. Installation of supercharger on a four-cycle diesel engine can result in the following percentage increase in power
(a) upto 25%
(b) upto 35%
(c) upto 50%
(d) upto 75%
(e) upto 100%.
Ans: e

90. Scavenging is usually done to increase
(a) thermal efficiency
(b) speed
(c) power output
(d) fuel consumption
(e) all of the above.
Ans: c

91. Which of the following is the lightest and most volatile liquid fuel
(a) diesel
(b) kerosene
(c) fuel oil
(d) gasoline
(e) lub oil.
Ans: d

92. The theoretically correct air fuel ratio for petrol engine is of the order of
(a) 6 : 1
(b) 9 : 1
(c) 12 : 1
(d) 15 : 1
(e) 20 : 1.
Ans: d

93. Air fuel ratio for idling speed of a petrol engine is approximately
(a) 1 : 1
(b) 5 : 1
(c) 10:1
(d) 15 : 1
(e) 20 : 1.
Ans: c

94. Air fuel ratio at which a petrol engine can not work is
(a) 8 : 1
(b) 10 : 1
(c) 15 : 1
(d) 20 : 1 and less
(e) will work at all ratios.
Ans: d

95. For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of
(a) 9 : 1
(b) 12 : 1
(c) 15 : 1
(d) 18 : 1
(e) 20: 1.
Ans: b

96. The following volume of air is required for consuming 1 liter of fuel by a four stroke engine
(a) 1 m3
(b) 5 m3
(c) 5-6 m3
(d) 9-10 m3
(e) 15-18 m3.
Ans: d

97. Pour point of fuel oil is the
(a) minimum temperature to which oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame
(b) temperature at which it solidifies or congeals
(c) it catches fire without external aid
(d) indicated by 90% distillation temperature i.e., when 90% of sample oil has distilled off
(e) temperature at which it flows easily.
Ans: b

98. A 5 BHP engine running at full load would consume diesel of the order of
(a) 0.3 kg/hr
(b) 1 kg/hr
(c) 3 kg/hr
(d) 5 kg/hr
(e) 10 kg/hr.
Ans: b

99. Diesel engine can work on very lean air fuel ratio of the order of 30 : 1. A petrol engine can also work on such a lean ratio provided
(a) it is properly designed
(b) best quality fuel is used
(c) can not work as it is impossible
(d) flywheel size is proper
(e) engine cooling is stopped.
Ans: c

100. A diesel engine has
(a) 1 valve
(b) 2 valves
(b) 3 valves
(d) 4 valves
(e) no valve.
Ans: c