# 300+ TOP I.C. Engines MCQ Questions and Answers Quiz

## 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

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

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

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

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

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

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

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

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

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

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

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.

13. Which of the following is the lightest and most volatile liquid fuel?

A. Diesel

B. Kerosene

C. Fuel oil

D. Gasoline

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

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

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

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

18. The ignition quality of petrol is expressed by

A. Cetane number

B. Octane number

C. Calorific value

D. All of these

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

43. The inlet valve of a four stroke cycle internal combustion engine remains open for

A. 130°

B. 180°

C. 230°

D. 270°

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

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

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

47. In petrol engines, advancing of the spark timing will _________ the knocking tendency.

A. Not effect

B. Decrease

C. Increase

D. None of these

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

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

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

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)

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

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

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

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

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

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

59. Scavenging is usually done to increase

A. Thermal efficiency

B. Speed

C. Power output

D. Fuel consumption

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)

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

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)

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

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

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

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

67. The process of breaking up or a liquid into fine droplets by spraying is called

A. Vaporisation

B. Carburetion

C. Ionization

D. Atomization

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

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

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

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

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

73. In loop scavenging, the top of the piston is

A. Flat

B. Contoured

C. Slanted

D. Depressed

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

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%

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

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

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

79. Polymerization is a chemical process in which molecules of a compound become

A. Larger

B. Slowed down

C. Smaller

D. Liquid

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

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

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

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

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

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

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

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

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

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

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

91. Engine pistons are usually made of aluminium alloy because it

A. Is lighter

B. Wear is less

C. Absorbs shocks

D. Is stronger

92. Which of the following fuel detonates readily?

A. Benzene

B. Iso-octane

C. Normal heptane

D. Alcohol

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

94. During idling, a petrol engine requires _________ mixture.

A. Lean

B. Rich

C. Chemically correct

D. None of these

95. The air-fuel ratio in petrol engines is controlled by

A. Controlling valve opening/closing

B. Governing

C. Injection

D. Carburetion

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

114. Which of the following does not relate to a spark ignition engine?

A. Ignition coil

B. Spark plug

C. Carburettor

D. Fuel injector

115. Compression loss in I.C engines occurs due to

A. Leaking piston rings

C. Clogged air inlet slots

D. All of the above

116. Iso-octane (C₈H₁₈) has octane number of

A. 0

B. 50

C. 100

D. 120

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

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

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

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

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

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

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

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%

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

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

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

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

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

130. The thermal efficiency of petrol and gas engines is about

A. 15%

B. 30%

C. 50%

D. 70%

131. Which is more viscous lube oil?

A. SEA 30

B. SAE 50

C. SAE 70

D. SAE 80

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

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

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

135. The magneto in an automobile is basically

A. Transformer

B. D.C. generator

C. Capacitor

D. Magnetic circuit

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

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

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

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

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

141. The inlet value of a four stroke cycle I.C engine remains open for nearly

A. 180°

B. 125°

C. 235°

D. 200°

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

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

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

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

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.

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

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

149. A diesel engine has

A. 1 valve

B. 2 valves

C. 3 valves

D. 4 valves

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

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

152. The reflectivity depends upon

A. Geometry of the reflector

B. Energy of neutrons

C. Properties of the reflector

D. All of these

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

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

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

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)

157. In a cycle, the spark lasts roughly for

A. 1 sec

B. 0.1 sec

C. 0.01 sec

D. 0.001 sec

158. Which of the following does not relate to a compression ignition engine?

A. Fuel pump

B. Fuel injector

C. Governor

D. Carburettor

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

160. The advancing of spark timing in spark ignition engines will _________ knocking tendency.

A. Increase

B. Reduce

C. Not effect

D. None of these

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

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

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

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

165. The calorific value of gaseous fuels is expressed in terms of

A. kcal

B. kcal/kg

C. kcal/m²

D. kcal/m3

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

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

168. The combustion in compression ignition engines is

A. Homogeneous

B. Heterogeneous

C. Both (A) and (B)

D. None of these

169. Supercharging is essential in

A. Diesel engines

B. Gas turbines

C. Petrol engines

D. Aircraft engines

170. Which of the following fuel has little tendency towards detonation?

A. Benzene

B. Iso-octane

C. Normal heptane

D. Alcohol

171. Most high speed compression engines operate on

A. Diesel cycle

B. Otto cycle

C. Dual combustion cycle

D. Special type of air cycle

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

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

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

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

176. Diesel as compared to petrol is

A. Highly ignitable

B. More difficult to ignite

C. Less difficult to ignite

D. None of these

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

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

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

180. The self ignition temperature of petrol is _________ as compared to diesel oil.

A. Same

B. Lower

C. Higher

D. None of these

181. In diesel engine, the compression ratio in comparison to expansion ratio is

A. Same

B. Less

C. More

D. Variable

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

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

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

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%

186. The thermal efficiency of diesel engines on weak mixtures is

A. Unaffected

B. Lower

C. Higher

D. Dependent on other factors

187. Combustion in compression ignition engines is

A. Homogeneous

B. Heterogeneous

C. Both (A) and (B)

D. Laminar

188. The colour of exhaust from diesel engine is generally

A. White

B. Bluish

C. Black

D. Violet

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

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

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

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

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

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

195. Most high speed compression engines operate on

A. Otto cycle

B. Diesel cycle

C. Dual cycle

D. Carnot cycle

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

197. The air-fuel ratio of the petrol engine is controlled by

A. Fuel pump

B. Governor

C. Injector

D. Carburettor

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.

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

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

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

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

203. The effective inhibitor of pre-ignition is

A. Alcohol

B. Water

D. None of these

204. A diesel engine has

A. One valve

B. Two valves

C. Three valves

D. Four valves

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

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

207. Morse test can be conducted for

A. Petrol engines

B. Diesel engines

C. Multi cylinder engines

D. All of these

208. High speed compression engines operate on

A. Otto cycle

B. Diesel cycle

C. Dual combustion cycle

D. All of these

209. The theoretically correct mixture of air and petrol is

A. 10 : 1

B. 15 : 1

C. 20 : 1

D. 25 : 1

210. A diesel engine has compression ratio from

A. 6 to 10

B. 10 to 15

C. 15 to 25

D. 25 to 40

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

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

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

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

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

230. Alpha-methyl-naphthalene (C₁₁ H₁₀) has a cetane number of

A. 0

B. 50

C. 100

D. 120

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

232. The thermal efficiency of a petrol engine is _________ as compared to diesel engine.

A. Same

B. Less

C. More

D. None of these

233. The thermal efficiency of diesel engines is about

A. 15%

B. 30%

C. 50%

D. 70%

234. The ignition quality of diesel oil is expressed by

A. Cetane number

B. Octane number

C. Calorific value

D. None of these

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

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

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

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

239. Antiknock for compression ignition engines is

A. Napthene

C. Amyl nitrate

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

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

242. A petrol engine has compression ratio from

A. 6 to 10

B. 10 to 15

C. 15 to 25

D. 25 to 40

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

244. The normal heptane (C₇H₁₆) is given a rating of ________ octane number.

A. 0

B. 50

C. 100

D. 120

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

246. The air-fuel ratio of the petrol engine is controlled by

A. Carburettor

B. Injector

C. Governor

D. None of these

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

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%

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

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

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

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

253. The injection pressure in a diesel engine is about

A. 10 bar

B. 100 bar

C. 150 bar

D. 500 bar

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

#### 36 thoughts on “300+ TOP I.C. Engines MCQ Questions and Answers Quiz”

1. Shivam geed says:

Sir mujhe iti mmv 4th sem trade k objective hona

2. Hrishikesh Dutta says:

Sir, plz send me all the Pdf files of questions with answers …

3. mohamed ata says:

plz, can u send me a pdf for these questions @mohamedatta750@gmail.com

4. Aman says:

5. Aman says:

6. Aman says:

Sir, Plz send answer of 111 to 250.

7. kannan says:

very useful questions with answers in IC engines.

8. jatindra mohanty says:

9. neeraj gupta says:

Please sir hindi me question dijiye

10. Bikalpa says:

11. Amar Sharma says:

12. Iqbal singh says:

Pls provide answers of question from no. 111to250

13. mahesh says:

Plz sir submit the remaining answer as soon as quick or send on my mail adress

14. k.s.prabu says:

this material is super i wan to prepare goverment exam can you send pdf copy

16. Vishal says:

Without answers how to get benefitted for upcoming exams? Pls update or mail it me..
Thanks

17. bukayaw says:

thanks a lot, very useful for every MENG students.

18. rifaz says:

19. sem says:

20. Karan says:

21. amit says:

Sir pls send me all mech subjects pdf

22. SIJUMON N S says:

can you send it to my mail

23. vijendra says:

24. Big potato says:

why some questions have no answers

25. Krishna Gupta says:

Answer kaha hai sir G plz update to karo

26. veeru says:

27. karthick says:

Where is answers and can u update aptitude queations on mechanics and dynamics

28. sandeep says:

ques 111 to till end….answers not available…….

1. Sasikumar says:

I need answer for QN no from 111 to 250

1. k.s.prabu says:

I need answer for Q.No:from 111 to 250

1. k.s.prabu says: