I.C. Engines Multiple Choice Questions with Answers :-
1. In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as
A. Scavenging
B. Detonation
C. Supercharging
D. Polymerisation
Answer: A
2. 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
Answer: D
3. Number of working strokes per min. for a four stroke cycle engine are _________ the speed of the engine in r.p.m.
A. Equal to
B. One-half
C. Twice
D. Four-times
Answer: B
4. In a typical medium speed 4-stroke cycle diesel engine the inlet valve
A. Opens at 20° before top dead center and closes at 35° after the bottom dead center
B. Opens at top dead center and closes at bottom dead center
C. Opens at 10° after top dead center and closes 20° before the bottom dead center
D. May open or close anywhere
Answer: A
5. The voltage required to produce a spark across the gap, between the sparking points is
A. 2000 to 4000 volts
B. 4000 to 6000 volts
C. 6000 to 10,000 volts
D. 10,000 to 12,000 volts
Answer: C
6. Compression ratio of I.C. Engines is
A. The ratio of volumes of air in cylinder before compression stroke and after compression stroke
B. Volume displaced by piston per stroke and clearance volume in cylinder
C. Ratio of pressure after compression and before compression
D. Swept volume/cylinder volume
Answer: A
7. 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
Answer: D
8. The air standard efficiency of an I.C. engine is given by (where r = Compression ratio, and γ = Ratio of specific heats)
A. 1 – rγ – 1
B. 1 + rγ – 1
C. 1 – (1/rγ – 1)
D. None of these
Answer: C
9. In the opposed piston diesel engine, the combustion chamber is located
A. Above the piston
B. Below the piston
C. Between the pistons
D. There is no such criterion
Answer: C
10. The ignition of the charge by some hot surface within the engine before the passage of spark is called
A. Pre-ignition
B. Detonation
C. Ignition delay
D. Auto-ignition
Answer: A
11. In a typical medium speed, 4-stroke cycle diesel engine
A. Fuel injection starts at 10° before top dead center and ends at 20° after top dead center
B. Fuel injection starts at top dead center and ends at 20° after top dead center
C. Fuel injection starts at just before top dead center and ends just after top dead center
D. May start and end anywhere
Answer: A
12. Which one of the following engines will have heavier flywheel than the remaining ones?
A. 30 kW four-stroke petrol engine running at 1500 r.p.m.
B. 30 kW two-stroke petrol engine running at 1500 r.p.m.
C. 30 kW two-stroke diesel engine running at 750 r.p.m.
D. 30 kW four-stroke diesel engine running at 750 r.p.m.
Answer: A
13. Which of the following is the lightest and most volatile liquid fuel?
A. Diesel
B. Kerosene
C. Fuel oil
D. Gasoline
Answer: D
14. The working pressure and temperature inside the cylinder of an internal combustion engine is _________ as compared to a steam engine.
A. Low
B. Very low
C. High
D. Very high
Answer: D
15. The rating of a diesel engine, with increase in air inlet temperature, will
A. Increase linearly
B. Decrease linearly
C. Increase parabolically
D. Decrease parabolically
Answer: B
16. If the temperature of intake air in internal combustion engine increases, then its efficiency will
A. Remain same
B. Decrease
C. Increase
D. None of these
Answer: B
17. The operation of forcing additional air under pressure in the engine cylinder is known as
A. Scavenging
B. Turbulence
C. Supercharging
D. Pre-ignition
Answer: C
18. The ignition quality of petrol is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. All of these
Answer: B
19. The mean effective pressure obtained from engine indicator indicates the
A. Maximum pressure developed
B. Minimum pressure
C. Instantaneous pressure at any instant
D. Average pressure
Answer: D
20. The probability of knocking in diesel engines is increased by
A. High self ignition temperature
B. Low volatility
C. Higher viscosity
D. All of these
Answer: D
21. 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
Answer: B
22. In a four stroke cycle petrol engine, the compression
A. Starts at 40° after bottom dead centre and ends at 30° before top dead centre
B. Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre
C. Starts at bottom dead centre and ends at top dead centre
D. May start and end anywhere
Answer: A
23. The maximum temperature in the I.C. engine cylinder is of the order of
A. 500-1000°C
B. 1000-1500°C
C. 1500-2000°C
D. 2000-2500°C
Answer: D
24. In compression ignition engines, swirl denotes a
A. Haphazard motion of the gases in the chamber
B. Rotary motion of the gases in the chamber
C. Radial motion of the gases in the chamber
D. None of the above
Answer: B
25. Supercharging is the process of
A. Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
B. Providing forced cooling air
C. Injecting excess fuel for raising more loads
D. Supplying compressed air to remove combustion products fully
Answer: A
26. The knocking in spark ignition engines can be reduced by
A. Retarding the spark
B. Increasing the engine speed
C. Both (A) and (B)
D. None of these
Answer: C
27. An engine indicator is used to determine the following
A. Speed
B. Temperature
C. Volume of cylinder
D. m.e.p. and I.H.P.
Answer: D
28. In a four stroke cycle diesel engine, the exhaust valve
A. Opens at 30° before bottom dead centre and closes at 10° after top dead centre
B. Opens at 30° after bottom dead centre and closes at 10° before top dead centre
C. Opens at bottom dead centre and closes at top dead centre
D. May open and close anywhere
Answer: A
29. The pressure at the end of compression in the case of diesel engine is of the order of
A. 6 kg/cm
B. 12 kg/cm
C. 20 kg/cm
D. 35 kg/cm
Answer: D
30. The fuels in order of decreasing knock tendency for spark ignition engines are
A. Paraffin, aromatic, napthene
B. Paraffin, napthene, aromatic
C. Napthene, aromatics, paraffin
D. Napthene, paraffin, aromatic
Answer: B
31. Crankcase explosion in I.C. engines usually occurs as
A. First a mild explosion followed by a bi explosion
B. First a big explosion followed by a mil explosion
C. Both mild and big explosions occurs simultaneously
D. Never occurs
Answer: A
32. The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is
A. More
B. Less
C. Same
D. May be more or less depending on engine capacity
Answer: B
33. In a four stroke cycle diesel engine, the compression
A. Starts at 40° after bottom dead center and ends at 10° before top dead center
B. Starts at 40° before top dead center and ends at 40° after top dead center
C. Starts at top dead center and ends at 40° before bottom dead center
D. May start and end anywhere
Answer: A
34. It the temperature of intake air in IC engines is lowered, then its efficiency will
A. Increase
B. Decrease
C. Remain same
D. Increase up to certain limit and then decrease
Answer: A
35. The loud pulsating noise heard within the cylinder of an internal combustion engine is known as
A. Detonation
B. Turbulence
C. Pre-ignition
D. Supercharging
Answer: A
36. Which of the following medium is compressed in a Diesel engine cylinder?
A. Air alone
B. Air and fuel
C. Air and lub oil
D. Fuel alone
Answer: A
37. Detonation is harmful due to
A. Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine
B. Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls
C. High intensity of knock causes crankshaft vibration and the engine runs rough
D. None of the above
Answer: D
38. A stoichiometric air-fuel ratio is
A. Chemically correct mixture
B. Lean mixture
C. Rich mixture for idling
D. Rich mixture for over loads
Answer: A
39. The firing order in an I.C. engine depends upon
A. Arrangement of the cylinders
B. Design of crankshaft
C. Number of cylinders
D. All of these
Answer: D
40. Pick up the false statement
A. Thermal efficiency of diesel engine is about 34%
B. Theoretically correct mixture of air and petrol is approximately 15:1
C. High speed compression engines operate on dual combustion cycle
D. S.I. engines are quality governed engines
Answer: D
41. The maximum propulsive efficiency of a turbojet engine is at a speed of
A. 1000 km/h
B. 2000 km/h
C. 2400 km/h
D. 3000 km/h
Answer: C
42. The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called
A. Net efficiency
B. Efficiency ratio
C. Relative efficiency
D. Overall efficiency
Answer: C
43. The inlet valve of a four stroke cycle internal combustion engine remains open for
A. 130°
B. 180°
C. 230°
D. 270°
Answer: C
44. 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
Answer: D
45. Number of working strokes per min. for a two stroke cycle engine is _________ the speed of the engine in r.p.m.
A. Equal to
B. One-half
C. Twice
D. Four-times
Answer: A
46. Flash point of fuel oil is
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. 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
Answer: A
47. In petrol engines, advancing of the spark timing will _________ the knocking tendency.
A. Not effect
B. Decrease
C. Increase
D. None of these
Answer: C
48. In a naturally aspirated diesel engine, the air is supplied by
A. A supercharger
B. A centrifugal blower
C. A vacuum chamber
D. An injection tube
Answer: C
49. A supercharged engine as compared to an ordinary engine
A. Requires smaller foundation
B. Is lighter
C. Consumes less lubricating oil
D. All of these
Answer: D
50. Which of the following is not an intern’s combustion engine?
A. 2-stroke petrol engine
B. 4-stroke petrol engine
C. Diesel engine
D. Steam turbine
Answer: D
51. The spark ignition engines are governed by
A. Hit and miss governing
B. Qualitative governing
C. Quantitative governing
D. Combination of (B) and (C)
Answer: C
52. 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. Cannot work as it is impossible
D. Flywheel size is proper
Answer: C
53. The object of providing masked inlet valve in the air passage of compression ignition engines is to
A. Enhance flow rate
B. Control air flow
C. Induce primary swirl
D. Induce secondary turbulence
Answer: C
54. In the crankcase method of scavenging, the air pressure is produced by
A. Supercharger
B. Centrifugal pump
C. Natural aspirator
D. Movement of engine piston
Answer: D
55. The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, l = Length of arm in meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Dia. of brake drum in meters, and d = Dia. of rope in meters)
A. B.P = (Wl × 2πN)/60 watts
B. B.P = [(W – S) πDN]/60 watts
C. B.P = [(W – S) π (D + d) N]/60 watts
D. All of these
Answer: D
57. The temperature of interior surface of cylinder wall in normal operation is not allowed to exceed
A. 80°C
B. 120°C
C. 180°C
D. 240°C
Answer: C
58. Thermal efficiency of a two stroke cycle engine is _________ a four stroke cycle engine.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer: B
59. Scavenging is usually done to increase
A. Thermal efficiency
B. Speed
C. Power output
D. Fuel consumption
Answer: C
60. If V₁ is the jet velocity and V₀ is the vehicle velocity, then the propulsive efficiency of a rocket is given by
A. [2(V₀/V₁)]/ [1 + (V₀/V₁)²]
B. (V₀/V₁)/ [1 + (V₀/V₁)²]
C. V₀/(V₀ + V₁)
D. V₁/(V₀ + V₁)
Answer: A
61. The pressure and temperature at the end of compression stroke in a petrol engine are of the order of
A. 4-6 kg/cm² and 200-250°C
B. 6-12 kg/cm² and 250-350°C
C. 12-20 kg/cm² and 350-450°C
D. 20-30 kg/cm² and 450-500°C
Answer: B
62. The compression ignition engines are governed by
A. Hit and miss governing
B. Qualitative governing
C. Quantitative governing
D. Combination of (B) and (C)
Answer: B
63. The reason for supercharging in any engine is to
A. Increase efficiency
B. Increase power
C. Reduce weight and bulk for a given output
D. Effect fuel economy
Answer: C
64. Stoichiometric ratio is
A. Chemically correct air-fuel ratio by weight
B. Chemically correct air-fuel ratio by volume
C. Actual air-fuel ratio for maximum efficiency
D. None of the above
Answer: B
65. Volatility of diesel fuel oil is
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
Answer: D
66. The purpose of testing an internal combustion engine is
A. To determine the information, which cannot be obtained by calculations
B. To conform the data used in design, the validity of which may be doubtful
C. To satisfy the customer regarding the performance of the engine
D. All of the above
Answer: D
67. The process of breaking up or a liquid into fine droplets by spraying is called
A. Vaporisation
B. Carburetion
C. Ionization
D. Atomization
Answer: D
68. The ratio of the volume of charge admitted at N.T.P. to the swept volume of the piston is called
A. Mechanical efficiency
B. Overall efficiency
C. Volumetric efficiency
D. Relative efficiency
Answer: C
69. The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is
A. Same
B. Less
C. More
D. More or less depending on power rating
Answer: C
70. In order to prevent knocking in spark ignition engines, the charge away from the spark plug should have
A. Low density
B. Low temperature
C. Long ignition delay
D. All of these
Answer: D
71. 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
Answer: C
72. The power actually developed by the engine cylinder of an I.C. engine is known as
A. Theoretical power
B. Actual power
C. Indicated power
D. None of these
Answer: C
73. In loop scavenging, the top of the piston is
A. Flat
B. Contoured
C. Slanted
D. Depressed
Answer: B
74. The correct sequence of the decreasing order of brake thermal efficiency of the three given basic types of engines is
A. Four stroke C.I. engine, four stroke S.I. engine, two stroke S.I. engine
B. Four stroke S.I. engine, four stroke C.I. engine, two stroke S.I. engine
C. Four stroke C.I. engine, two stroke S.I. engine, four stroke S.I. engine
D. Two stroke S.I. engine, four stroke S.I. engine, four stroke C.I. engine
Answer: A
75. If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, the percentage increase in efficiency will be
A. 2%
B. 4%
C. 8%
D. 14%
Answer: D
76. The knocking tendency in compression ignition engines for a given fuel will be
A. Enhanced by decreasing compression ratio
B. Enhanced by increasing compression ratio
C. Dependent on other factors
D. None of the above
Answer: A
77. When crude oil is heated, then which of the following hydrocarbon is given off first?
A. Kerosene
B. Gasoline
C. Paraffin
D. Natural gas
Answer: D
78. Supercharging is the process of supplying the intake air to the engine cylinder at a density _________ the density of the surrounding atmosphere.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer: C
79. Polymerization is a chemical process in which molecules of a compound become
A. Larger
B. Slowed down
C. Smaller
D. Liquid
Answer: A
80. In a petrol engine, the fuel supplied to the engine cylinder is mixed with required quantity of air and the mixture is ignited with a
A. Fuel pump
B. Fuel injector
C. Spark plug
D. None of these
Answer: C
81. 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
Answer: B
82. The ratio of the indicated thermal efficiency to the air standard efficiency is known as
A. Mechanical efficiency
B. Overall efficiency
C. Volumetric efficiency
D. Relative efficiency
Answer: D
83. The knock in diesel engine occurs due to
A. Instantaneous and rapid burning of the first part of the charge
B. Instantaneous auto ignition of last part of charge
C. Delayed burning of the first part of the charge
D. Reduction of delay period
Answer: A
84. Which of the following statement is correct regarding petrol engines?
A. A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure
B. The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug
C. The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition
D. All of the above
Answer: B
85. If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the
A. Exhaust will be smoky
B. Piston rings would stick into piston grooves
C. Engine starts overheating
D. Scavenging occurs
Answer: D
86. Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke, and is due to
A. Cylinder walls being too hot
B. Overheated spark plug points
C. Red hot carbon deposits on cylinder walls
D. Any one of these
Answer: D
87. Scavenging air in diesel engine means
A. Air used for combustion sent under pressure
B. Forced air for cooling cylinder
C. Burnt air containing products of combustion
D. Air used for forcing burnt gases out of engine’s cylinder during the exhaust period
Answer: D
88. The reference fuels for knock rating of spark ignition engines would include
A. Iso-octane and alpha-methyl naphthalene
B. Normal octane and aniline
C. Iso-octane and normal hexane
D. Normal heptane and iso-octane
Answer: D
89. The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft
A. 1/2
B. 1
C. 2
D. 4
Answer: C
90. The brake power of a diesel engine, keeping other parameters constant, can be increased by
A. Decreasing the density of intake air
B. Increasing the temperature of intake air
C. Increasing the pressure of intake air
D. Decreasing the pressure of intake air
Answer: C
91. Engine pistons are usually made of aluminium alloy because it
A. Is lighter
B. Wear is less
C. Absorbs shocks
D. Is stronger
Answer: A
92. Which of the following fuel detonates readily?
A. Benzene
B. Iso-octane
C. Normal heptane
D. Alcohol
Answer: C
93. In a typical medium speed 4-stroke cycle diesel engines
A. Exhaust valve opens at 35° before bottom 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
Answer: A
94. During idling, a petrol engine requires _________ mixture.
A. Lean
B. Rich
C. Chemically correct
D. None of these
Answer: B
95. The air-fuel ratio in petrol engines is controlled by
A. Controlling valve opening/closing
B. Governing
C. Injection
D. Carburetion
Answer: D
96. The function of a distributor in a coil ignition system of I.C. engines is
A. To distribute spark
B. To distribute power
C. To distribute current
D. To time the spark
Answer: D
97. The specific fuel consumption per BH hour for a petrol engine is approximately
A. 0.15 kg
B. 0.2 kg
C. 0.25 kg
D. 0.3 kg
Answer: C
98. In a four stroke cycle petrol engine, the expansion
A. Starts at top dead center and ends at bottom dead center
B. Starts at 30° before top dead center and ends at 50° before bottom dead center
C. Starts at 30° after top dead center and ends at 50° after bottom dead center
D. May start and end anywhere
Answer: B
99. 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
Answer: D
100. As compared to air standard cycle, in actual working, the effect of variation in specific heats is to
A. Increase maximum pressure and maximum temperature
B. Reduce maximum pressure and maximum temperature
C. Increase maximum pressure and decrease maximum temperature
D. Decrease maximum pressure and increase maximum temperature
Answer: B
101. Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads
A. The friction is high
B. The friction is unpredictable
C. The small difference in cooling water temperature or in internal friction has a disproportionate effect
D. The engine is rarely operated
Answer: C
102. By higher octane number of spark ignition fuel, it is meant that the fuel has
A. Higher heating value
B. Higher flash point
C. Lower volatility
D. Longer ignition delay
Answer: D
103. In diesel engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of
A. 250°C
B. 500°C
C. 1000°C
D. 2000°C
Answer: C
104. A gas engine has a swept volume of 300 cm3 and clearance volume of 25 cm3. Its volumetric efficiency is 0.88 and mechanical efficiency is 0.90. The volume of the mixture taken in per stroke is
A. 248 cm3
B. 252 cm3
C. 264 cm3
D. 286 cm3
Answer: C
105. In a typical medium speed 4-stroke cycle diesel engine
A. Compression starts at 35° after bottom dead center and ends at top dead center
B. Compression starts at bottom dead center and ends at top dead center
C. Compression starts at 10° before bottom dead center and, ends just before top dead center
D. May start and end anywhere
Answer: A
106. In a petrol engine, the mixture has the lowest pressure at the
A. Beginning of suction stroke
B. End of suction stroke
C. End of compression stroke
D. None of these
Answer: B
107. The specific fuel consumption per BHP hour for diesel engine is approximately
A. 0.15 kg
B. 0.2 kg
C. 0.25 kg
D. 0.3 kg
Answer: B
108. Which of the following statement is correct?
A. Compression ratio for petrol engines varies from 6 to 10
B. Higher compression ratio in diesel engines results in higher pressures
C. Petrol engines work on Otto cycle
D. All of the above
Answer: D
109. All heat engines utilize
A. Low heat value of oil
B. High heat value of oil
C. Net calorific value of oil
D. Calorific value of fuel
Answer: A
110. Which of the following statement is wrong?
A. A four stroke cycle engine develops twice the power as that of a two stroke cycle engine
B. For the same power developed, a four stroke cycle engine is lighter, less bulky and occupies less floor area
C. The petrol engines are costly than diesel engines
D. All of the above
Answer: D
111. Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged?
A. Yes
B. No
C. To some extent
D. Unpredictable
Answer: B
112. Which one of the following event would reduce volumetric efficiency of a vertical compression ignition engine?
A. Inlet valve closing after bottom dead center
B. Inlet valve closing before bottom dead center
C. Inlet valve opening before top dead center
D. Exhaust valve closing after top dead center
Answer: B
113. In a diesel engine, the fuel is ignited by
A. Spark
B. Injected fuel
C. Heat resulting from compressing air that is supplied for combustion
D. Ignition
Answer: C
114. Which of the following does not relate to a spark ignition engine?
A. Ignition coil
B. Spark plug
C. Carburettor
D. Fuel injector
Answer: D
115. Compression loss in I.C engines occurs due to
A. Leaking piston rings
B. Use of thick head gasket
C. Clogged air inlet slots
D. All of the above
Answer: D
116. Iso-octane (C₈H₁₈) has octane number of
A. 0
B. 50
C. 100
D. 120
Answer: C
117. As a result of detonation in an I.C. engine, following parameter attains very high value
A. Peak pressure
B. Rate of rise of pressure
C. Rate of rise of temperature
D. Peak temperature
Answer: B
118. A two stroke cycle engine gives ________ the number of power strokes as compared to the four stroke cycle engine, at the same engine speed.
A. Half
B. Same
C. Double
D. Four times
Answer: C
119. The accumulation of carbon in a cylinder results in increase of
A. Clearance volume
B. Volumetric efficiency
C. Ignition time
D. Effective compression ratio
Answer: D
120. In a four stroke cycle engine, the sequence of operations is
A. Suction, compression, expansion and exhaust
B. Suction, expansion, compression and exhaust
C. Expansion, compression, suction and exhaust
D. Compression, expansion, suction and exhaust
Answer: A
121. Gaseous fuel guarantees are based on
A. Calorific value of oil
B. Low heat value of oil
C. High heat value of oil
D. Mean heat value of oil
Answer: B
122. The ratio of the work obtained at the crankshaft in a given time to the energy supplied during the same time is called
A. Mechanical efficiency
B. Overall efficiency
C. Indicated thermal efficiency
D. Volumetric efficiency
Answer: B
123. 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
Answer: B
124. The volumetric efficiency of a well designed engine may be
A. 30 to 40%
B. 40 to 60%
C. 60 to 70%
D. 75 to 90%
Answer: D
125. 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
Answer: B
126. A petrol engine, during suction stroke draws
A. Air only
B. Petrol only
C. A mixture of petrol and air
D. None of these
Answer: C
127. Which of the following statements is correct?
A. All the irreversible engines have same efficiency
B. All the reversible engines have same efficiency
C. Both Rankine and Carnot cycles have same efficiency between same temperature limits
D. All reversible engines working between same temperature limits have same efficiency
Answer :Option D
128. The fuel valve in a four stroke cycle diesel engine
A. Opens at 15° after top dead center and closes at 20° before bottom dead center
B. Opens at 15° before top dead center and closes at 20° after top dead center
C. Opens at top dead center and closes at bottom dead center
D. May open and close anywhere
Answer: B
129. For the same power developed in I.C. engines, the cheaper system is
A. Naturally aspirated
B. Supercharged
C. Centrifugal pump
D. Turbo charger
Answer: B
130. The thermal efficiency of petrol and gas engines is about
A. 15%
B. 30%
C. 50%
D. 70%
Answer: B
131. Which is more viscous lube oil?
A. SEA 30
B. SAE 50
C. SAE 70
D. SAE 80
Answer: D
132. In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will _________ the knocking tendency.
A. Not effected
B. Decrease
C. Increase
D. None of these
Answer: C
133. Fuel oil consumption guarantees for I .C. engine are usually based on
A. Low heat value of oil
B. High heat value of oil
C. Net calorific value of oil
D. Calorific value of fuel
Answer: B
134. The compensating jet in a carburettor supplies almost constant amount of petrol at all speeds because the
A. Jet area is automatically varied depending on the suction
B. The flow from the main jet is diverted to the compensating jet with increase in speed
C. The diameter of the jet is constant and the discharge coefficient is invariant
D. Flow is produced due to the static head in the float chamber
Answer: D
135. The magneto in an automobile is basically
A. Transformer
B. D.C. generator
C. Capacitor
D. Magnetic circuit
Answer: B
136. In order to eliminate knocking in compression ignition engines, there should be
A. Short delay period
B. Late auto-ignition
C. Low compression ratio
D. High self ignition temperature of fuel
Answer: A
137. Air fuel ratio at which a petrol engine cannot work is
A. 8 : 1
B. 10 : 1
C. 15 : 1
D. 20 : 1 and less
Answer: D
138. A fuel of an octane number rating of 75 matches in knocking intensity as a mixture of
A. 75% iso-octane and 25% normal heptane
B. 75% normal heptane and 25% iso-octane
C. 75% petrol and 25% diesel
D. 75% diesel and 25% petrol
Answer: A
139. An hmh flame speed is obtained in diesel engine when air fuel ratio is
A. Uniform throughout the mixture
B. Chemically correct mixture
C. About 35% of rich mixture
D. About 10% of rich mixture
Answer: D
140. A supercharged engine as compared to an ordinary engine
A. Is lighter
B. Requires smaller foundations
C. Consumes less lubricating oil
D. All of these
Answer: D
141. The inlet value of a four stroke cycle I.C engine remains open for nearly
A. 180°
B. 125°
C. 235°
D. 200°
Answer: C
142. The basic requirement of a good combustion chamber is
A. Minimum turbulence
B. Low compression ratio
C. High thermal efficiency and power output
D. Low volumetric efficiency
Answer: C
143. The cam shaft of a four stroke I.C. engine running at 1500 rpm will run at
A. 1500 rpm
B. 750 rpm
C. 3000 rpm
D. Any value independent of engine speed
Answer: B
144. In a four stroke cycle petrol engine, the inlet valve
A. Opens at top dead center and closes at bottom dead center
B. Opens at 20° before top dead center and closes at 40° after bottom dead center
C. Opens at 20° after top dead center and closes at 20° before bottom dead center
D. May open or close anywhere
Answer: B
145. 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. Increasing the compression ratio
C. Adherence to proper fuel specification
D. Avoidance of overloading
Answer: B
146. The frictional power (F.P.) is given by
A. F.P. = B.P. – I.P.
B. F.P. = I.P. – B.P.
C. F.P. = B.P./I.P.
D. F.P. = I.P./B.P.
Answer: B
147. 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. 56 m3
D. 910 m3
Answer: D
148. The delay period in compression ignition engines depends upon
A. Temperature and pressure in the cylinder at the time of injection
B. Nature of the fuel mixture strength
C. Relative velocity between the fuel injection and air turbulence pressure of residual gases
D. All of the above
Answer: D
149. A diesel engine has
A. 1 valve
B. 2 valves
C. 3 valves
D. 4 valves
Answer: C
150. The mechanical efficiency (ηm) of the engine is given by
A. ηm = B.P/I.P
B. ηm = I.P/B.P
C. ηm = (B.P × I.P)/100
D. None of these
Answer: A
151. The output of a diesel engine can be increased without increasing the engine revolution or size in following way
A. Feeding more fuel
B. Heating incoming air
C. Scavenging
D. Supercharging
Answer: D
152. The reflectivity depends upon
A. Geometry of the reflector
B. Energy of neutrons
C. Properties of the reflector
D. All of these
Answer: D
153. 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. None of the above
Answer: A
154. The sensing element in the control system of nuclear reactors measures the _________ of the neutron flux in the reactor.
A. Temperature
B. Volume
C. Density
D. None of these
Answer: C
155. Pick up the wrong statement
A. 2-stroke engine can run in any direction
B. In 4-stroke engine, a power stroke is obtained in 4-strokes
C. Thermal efficiency of 4-stroke engine is more due to positive scavenging
D. Petrol engines occupy more space than diesel engines for same power output
Answer: D
156. If V₁ is the jet velocity and V₀ is the vehicle velocity, then propulsive efficiency of a turbojet engine is
A. V₁ / (V₀ + V₁)
B. V₀ / (V₀ + V₁)
C. 2V₀ / (V₀ + V₁)
D. 2V₁ / (V₀ + V₁)
Answer: C
157. In a cycle, the spark lasts roughly for
A. 1 sec
B. 0.1 sec
C. 0.01 sec
D. 0.001 sec
Answer: D
158. Which of the following does not relate to a compression ignition engine?
A. Fuel pump
B. Fuel injector
C. Governor
D. Carburettor
Answer: D
159. Air fuel ratio for idling speed of a petrol engine is approximately
A. 1 : 1
B. 5 : 1
C. 10 : 1
D. 15 : 1
Answer: C
160. The advancing of spark timing in spark ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer: A
161. The fuel in diesel engine is normally injected at pressure of
A. 5-10 kg/cm²
B. 20-25 kg/cm²
C. 60-80 kg/cm²
D. 90-130 kg/cm²
Answer: D
162. A mixture containing 65% of iso-octane and 35% of normal heptane will have
A. Cetane number 65
B. Octane number 65
C. Cetane number 35
D. Octane number 35
Answer: B
163. The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will
A. Increase
B. Decrease
C. Be independent
D. May increase or decrease depending on other factors
Answer: B
164. Theoretically, a four stroke cycle engine should develop _________ power as that of a two stroke cycle engine.
A. Half
B. Same
C. Double
D. Four times
Answer: A
165. The calorific value of gaseous fuels is expressed in terms of
A. kcal
B. kcal/kg
C. kcal/m²
D. kcal/m3
Answer: D
166. The pressure at the end of compression, in diesel engines, is approximately
A. 10 bar
B. 20 bar
C. 25 bar
D. 35 bar
Answer: D
167. A 75 cc engine has following parameter as 75 cc
A. Fuel tank capacity
B. Lube oil capacity
C. Swept volume
D. Cylinder volume
Answer: C
168. The combustion in compression ignition engines is
A. Homogeneous
B. Heterogeneous
C. Both (A) and (B)
D. None of these
Answer: B
169. Supercharging is essential in
A. Diesel engines
B. Gas turbines
C. Petrol engines
D. Aircraft engines
Answer: D
170. Which of the following fuel has little tendency towards detonation?
A. Benzene
B. Iso-octane
C. Normal heptane
D. Alcohol
Answer: B
171. Most high speed compression engines operate on
A. Diesel cycle
B. Otto cycle
C. Dual combustion cycle
D. Special type of air cycle
Answer: C
172. The higher combustion chamber wall temperature in compression ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer: B
173. If the intake air temperature of I.C. engine increases, its efficiency will
A. Increase
B. Decrease
C. Remain same
D. None of these
Answer: B
174. Solid fuel fabricated into various small shapes, which are assembled to form fuel elements, is in the form of
A. Plates
B. Pallets
C. Pins
D. All of these
Answer: D
175. A heat engine utilizes the
A. Calorific value of oil
B. Low heat value of
C. High heat value of oil
D. Mean heat value of oil
Answer: C
176. Diesel as compared to petrol is
A. Highly ignitable
B. More difficult to ignite
C. Less difficult to ignite
D. None of these
Answer: B
177. 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
Answer: B
178. The increase of efficiency of a compression ignition engine, as the load decreases, is due to
A. Higher maximum temperature
B. Qualitative governing
C. Quantitative governing
D. Hit and miss governing
Answer: B
179. For the same compression ratio
A. Otto cycle is more efficient than the Diesel
B. Diesel cycle is more efficient than Otto
C. Both Otto and Diesel cycles are, equally efficient
D. Compression ratio has nothing to do with efficiency
Answer: A
180. The self ignition temperature of petrol is _________ as compared to diesel oil.
A. Same
B. Lower
C. Higher
D. None of these
Answer: C
181. In diesel engine, the compression ratio in comparison to expansion ratio is
A. Same
B. Less
C. More
D. Variable
Answer: C
182. In a four stroke cycle petrol engine, the pressure inside the engine cylinder during the suction stroke is __________ the atmospheric pressure.
A. Equal to
B. Below
C. Above
D. None of these
Answer: B
183. Diesel fuel, compared to petrol is
A. Less difficult to ignite
B. Just about the same difficult to ignite
C. More difficult to ignite
D. Highly ignitable
Answer: C
184. In a petrol engine, if diesel is used, then the engine will
A. Not run
B. Run more efficiently
C. Run at high speed
D. Explode
Answer: A
185. Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power
A. Up to 35%
B. Up to 50%
C. Up to 75%
D. Up to 100%
Answer: D
186. The thermal efficiency of diesel engines on weak mixtures is
A. Unaffected
B. Lower
C. Higher
D. Dependent on other factors
Answer: C
187. Combustion in compression ignition engines is
A. Homogeneous
B. Heterogeneous
C. Both (A) and (B)
D. Laminar
Answer: B
188. The colour of exhaust from diesel engine is generally
A. White
B. Bluish
C. Black
D. Violet
Answer: C
189. A diesel engine as compared to petrol engine (both running and rated load) is
A. More efficient
B. Less efficient
C. Equally efficient
D. Other factors will decide it
Answer: A
190. In a four stroke cycle petrol engine, the charge is ignited at
A. 30° before top dead center
B. 30° after top dead center
C. 30° before bottom dead center
D. 30° after bottom dead center
Answer: A
191. In case of gas turbines, the gaseous fuel consumption guarantees are based on
A. High heat value
B. Low heat value
C. Net calorific value
D. Calorific value
Answer: B
192. The knocking tendency in spark ignition engines may be decreased by
A. Controlling the air-fuel mixture
B. Controlling the ignition timing
C. Controlling the exhaust temperature
D. Reducing the compression ratio
Answer: D
193. The term scavenging is generally associated with
A. 2-stroke cycle engines
B. 4-stroke cycle engines
C. Aeroplane engines
D. High efficiency engines
Answer: D
194. Which of the following statement is correct regarding normal cetane?
A. It is a standard fuel used for knock rating of diesel engines
B. Its chemical name is normal hexadecane
C. It has long carbon chain structure
D. All of the above
Answer: D
195. Most high speed compression engines operate on
A. Otto cycle
B. Diesel cycle
C. Dual cycle
D. Carnot cycle
Answer: C
196. In a four stroke cycle diesel engine, the inlet valve
A. Opens at 20° before top dead center and closes at 40° after bottom dead center
B. Opens at 20° after top dead center and closes at 20° before bottom dead center
C. Opens at top dead center and closes at bottom dead center
D. May open and close anywhere
Answer: A
197. The air-fuel ratio of the petrol engine is controlled by
A. Fuel pump
B. Governor
C. Injector
D. Carburettor
Answer: D
198. Which of the following statement is wrong?
A. In compression ignition engines, detonation occurs near the beginning of combustion.
B. Since the fuel, in compression ignition engines, is injected at the end of compression stroke, therefore, there will be no pre-ignition.
C. To eliminate knock in compression ignition engines, we want to achieve auto-ignition not early and desire a long delay period.
D. In compression ignition engines, because of heterogeneous mixture, the rate of pressure rise is comparatively lower.
Answer: C
199. In a four stroke cycle, the minimum temperature inside the engine cylinder occurs at the
A. Beginning of suction stroke
B. End of suction stroke
C. Beginning of exhaust stroke
D. End of exhaust stroke
Answer: A
200. The exhaust valve in a four stroke cycle petrol engine
A. Opens at 50° before bottom dead center and closes at 15° after top dead center
B. Opens at bottom dead center and closes at top dead center
C. Opens at 50° after bottom dead center and closes at 15° before top dead center
D. May open and close anywhere
Answer: A
201. The expansion of fuel in a four stroke cycle diesel engine
A. Starts at 15° before top dead center and ends at 30° after top dead center
B. Starts at top dead center and ends at 30° after top dead center
C. Starts at 15° after top dead center and ends at 30° before bottom dead center
D. May start and end anywhere
Answer: C
202. In a diesel engine, the duration between the time of injection and ignition, is known as
A. Pre-ignition period
B. Delay period
C. Period of ignition
D. Burning period
Answer: B
203. The effective inhibitor of pre-ignition is
A. Alcohol
B. Water
C. Lead
D. None of these
Answer: B
204. A diesel engine has
A. One valve
B. Two valves
C. Three valves
D. Four valves
Answer: C
205. The pressure inside the cylinder is _________ the atmospheric pressure during the exhaust stroke.
A. Equal to
B. Below
C. Above
D. None of these
Answer: C
206. A carburettor is used to supply
A. Petrol, air and lubricating oil
B. Air and diesel
C. Petrol and lubricating oil
D. Petrol and air
Answer: D
207. Morse test can be conducted for
A. Petrol engines
B. Diesel engines
C. Multi cylinder engines
D. All of these
Answer: C
208. High speed compression engines operate on
A. Otto cycle
B. Diesel cycle
C. Dual combustion cycle
D. All of these
Answer: C
209. The theoretically correct mixture of air and petrol is
A. 10 : 1
B. 15 : 1
C. 20 : 1
D. 25 : 1
Answer: B
210. A diesel engine has compression ratio from
A. 6 to 10
B. 10 to 15
C. 15 to 25
D. 25 to 40
Answer: C
211. In order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke, then _________ is employed.
A. Fuel pump
B. Injector
C. Carburettor
D. None of these
Answer: C
212. The ratio of the brake power to the indicated power is called
A. Mechanical efficiency
B. Overall efficiency
C. Indicated thermal efficiency
D. Volumetric efficiency
213. The cetane (C₁₆H₃₄) which is a straight chain paraffin, is assigned a cetane number of
A. 0
B. 50
C. 100
D. 120
214. The thermodynamic cycle on which the petrol engine works, is
A. Otto cycle
B. Joule cycle
C. Rankine cycle
D. Stirling cycle
215. The correct mixture strength (by weight) for petrol is about
A. 14.6 : 1
B. 18.5 : 1
C. 20.4 : 1
D. 22.6 : 1
216. The scavenging efficiency of a four stroke cycle diesel engine is
A. Below 50%
B. Between 50 and 85%
C. Between 85 and 95%
D. Between 95 and 100%
217. If the speed of the engine is increased, the indicated power will
A. Increase
B. Decrease
C. Remain same
D. None of these
218. The specific fuel consumption per B.P. hour for a petrol engine is about
A. 0.2 kg
B. 0.25 kg
C. 0.3 kg
D. 0.35 kg
219. The injector nozzle of a compression ignition engine is required to inject fuel at a sufficiently high pressure in order to
A. Inject fuel in a chamber of high pressure at the end of compression stroke
B. Inject fuel at a high velocity to facilitate atomization
C. Ensure that penetration is not high
D. All of the above
220. A fuel of cetane number 40 has the same ignition quality as a mixture of
A. 40% cetane and 60% alpha methyl naphthalene
B. 40% alpha methyl naphthalene and 60% cetane
C. 40% petrol and 60% diesel
D. 40% diesel and 60% petrol
221. The two reference fuels used for cetane rating are
A. Cetane and iso-octane
B. Cetane and alpha-methyl naphthalene
C. Cetane and normal heptane
D. Cetane and tetra ethyl lead
222. In petrol engines, the delay period is of the order of
A. 0.001 second
B. 0.002 second
C. 0.003 second
D. 0.004 second
223. A diesel engine is _________ as compared to petrol engine, both running at rated load.
A. Equally efficient
B. Less efficient
C. More efficient
D. None of these
224. The pressure at the end of compression, in petrol engines, is approximately
A. 10 bar
B. 20 bar
C. 25 bar
D. 35 bar
225. The turbine of the turboprop engine is __________ that of the turbojet engine.
A. Same as
B. Smaller than
C. Bigger than
D. None of these
Answer: C(15)
226. A higher compression ratio causes
A. Pre-ignition
B. Increase in detonation
C. Acceleration in the rate of combustion
D. Any one of these
Answer: D
228. A spark plug gap is kept from
A. 0.3 to 0.7 mm
B. 0.2 to 0.8 mm
C. 0.4 to 0.9 mm
D. 0.6 to 1.0 mm
Answer: A
229. The air standard efficiency of an I.C. engine depends on
A. Fuel used
B. Speed of engine
C. Compression ratio
D. None of these
Answer: C
230. Alpha-methyl-naphthalene (C₁₁ H₁₀) has a cetane number of
A. 0
B. 50
C. 100
D. 120
Answer: A
231. The increase in intake temperature of internal combustion engines will _________ efficiency.
A. Have no effect on
B. Increase
C. Decrease
D. None of these
Answer: C
232. The thermal efficiency of a petrol engine is _________ as compared to diesel engine.
A. Same
B. Less
C. More
D. None of these
Answer: B
233. The thermal efficiency of diesel engines is about
A. 15%
B. 30%
C. 50%
D. 70%
Answer: D
234. The ignition quality of diesel oil is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. None of these
Answer: A
235. If petrol is used in a diesel engine, then
A. Low power will be produced
B. Efficiency will be low
C. Higher knocking will occur
D. Black smoke will be produced
Answer: C
236. In a coil ignition system of petrol engines, a condenser is connected across the contact breaker in order to
A. Prevent sparking across the gap between the points
B. Cause more rapid break of the primary current, giving a higher voltage in the secondary circuit
C. Both (A) and (B)
D. None of the above
Answer: C
237. The _________ engines can work on very lean mixture of fuel.
A. Spark ignition
B. Compression ignition
C. Both (A) and (B)
D. None of these
Answer: B
238. A diesel engine, during suction stroke, draws
A. Air only
B. Diesel only
C. A mixture of diesel and air
D. None of these
Answer: A
239. Antiknock for compression ignition engines is
A. Napthene
B. Tetra ethyl lead
C. Amyl nitrate
D. Hexadecane
Answer: C
240. The method of determination of indicated power of a multi cylinder spark ignition engine is by the use of
A. Morse test
B. Prony brake test
C. Motoring test
D. Heat balance test
Answer: A
241. The cetane number of diesel oil, generally available, is
A. 20 to 25
B. 25 to 30
C. 30 to 40
D. 40 to 55
Answer: D
242. A petrol engine has compression ratio from
A. 6 to 10
B. 10 to 15
C. 15 to 25
D. 25 to 40
Answer: A
243. The brake power is the power available
A. In the engine cylinder
B. At the crank shaft
C. At the crank pin
D. None of these
Answer: B
244. The normal heptane (C₇H₁₆) is given a rating of ________ octane number.
A. 0
B. 50
C. 100
D. 120
Answer: A
245. The knocking in diesel engines may be prevented by
A. Reducing the delay period
B. Raising the compression ratio
C. Increasing the inlet pressure of air
D. All of these
Answer: D
246. The air-fuel ratio of the petrol engine is controlled by
A. Carburettor
B. Injector
C. Governor
D. None of these
Answer: A
247. If the compression ratio in I.C. engine increases, then its thermal efficiency will
A. Decrease
B. Increase
C. Remain same
D. None of these
Answer: B
248. The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be
A. 25%
B. 50%
C. 70%
D. 100%
Answer: B
249. The octane number of petrol, generally available, is
A. 20 to 40
B. 40 to 60
C. 60 to 80
D. 80 to 100
Answer: D
250. The object of supercharging the engine is
A. To reduce mass of the engine per brake power
B. To reduce space occupied by the engine
C. To increase the power output of an engine when greater power is required
D. All of the above
Answer: D
251. The increase of cooling water temperature in petrol engine will _________ the knocking tendency.
A. Not effect
B. Decrease
C. Increase
D. None of these
Answer: C
252. The specific fuel consumption per B.P. hour for a diesel engine is about
A. 0.2 kg
B. 0.25 kg
C. 0.3 kg
D. 0.35 kg
Answer: A
253. The injection pressure in a diesel engine is about
A. 10 bar
B. 100 bar
C. 150 bar
D. 500 bar
Answer: B
254. Morse test is used to determine the I.P. of a
A. Single cylinder petrol engine
B. Four stroke engine
C. Single cylinder diesel engine
D. Multi cylinder engine
Answer: D