I.C. Engines Questions and Answers
1. 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
(e) 8.
Ans: c
2. 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
(e) combustion chamber.
Ans: c
3. Scavenging air in diesel engine means
(a) air used for combustion sent under pres-sure
(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
(e) air fuel mixture.
Ans: d
4. 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 load
(d) supplying compressed air to remove combustion
products fully
(e) raising exhaust pressure.
Ans: a
5. 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
(e) depends on other factors.
Ans: b
6. 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
(e) cycle efficiency.
Ans: c
7. Compression ratio of LC. 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
(e) cylinder volume/swept volume.
Ans: a
8. 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
(e) unpredictable.
Ans: c
9. The calorific value of gaseous fuels is expressed
in terms of
(a) kcal
(b) kcal/kg
(c) kcal/m2
(d) kcal/n?
(e) all of the above.
Ans: d
11. If the intake air temperature of I.C. engine
increases, its efficiency will
(a) increase
(b) decrease
(c) remain same
(d) unpredictable
(e) depend on other factors.
Ans: b
12. All heat engines utilize
(a) low heat value of oil
(b) high heat value of oil
(c) net claorific value of oil
(d) calorific value of fuel
(e) all of the above.
Ans: a
13. 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.
(e) BHP.
Ans: d
14. 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
(e) all of the above.
Ans: b
17. If the compression ratio of an engine working on
Otto cycle is increased from 5 to 7, the %age
increase in efficiency will be
(a) 2%
(b) 4%
(c) 8%
(d) 14%
(e) 27%.
Ans: d
18. 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) middle heat value
(e) calorific value.
Ans: b
19. 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
(e) remains open for 200°.
Ans: a
20. 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
(e) 30 - 40 kg/cm2 and 500 - 700°C.
Ans: b
21. The pressure at the end of compression in the
case of diesel engine is of the order of
(a) 6 kg/cm
(b) 12kg/cmz
(c) 20 kg/cmz
(d) 27.5 kg/cmz
(e) 35 kg/cm
Ans: e
22. 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
(e) 2500-3000°C
Ans: d
23. The thermal efficiecny 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
(e) none of the above.
Ans: b
24. 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 work on otto cycle
(e) petrol engines occupy more space than diesel
engines for same power output.
Ans: e
25. Combustion in compression ignition engines is
(a) homogeneous
(b) heterogeneous
(c) both (a) and (b)
(d) laminar
(e) turbulent.
Ans: b
26. 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
(e) 150-250 kg/cm2
Ans: d
27. 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
(e) 0.35 kg.
Ans: b
28. 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
(e) 320°C.
Ans: c
30. Crankcase explosion in I.C. engines usuall
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 occi simultaneously
(d) never occurs
(e) unpredictable.
Ans: a
31. Compression loss in I.C engines occurs duto
(a) leaking piston rings
(b) use of thick head gasket
(c) clogged air-inlet slots
(d) increase in clearance volume caused b bearing-
bushing wear
(e) all of the above.
Ans: e
32. 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) 0.3kg
(e) 0.35 kg.
Ans: c
33. The air requirement of a petrol engine during
starting compared to theoretical airequired for
complete combustion is
(a) more
(b) loss
(c) same
(d) may be more or less depending on engine
capacity
(e) unpredictable.
Ans: b
34. The inlet value of a four stroke cycle I.C engine
remains open for nearly
(a) 180°
(b) 125°
(c) 235°
(d) 200°
(e) 275°.
Ans: c
35. Which of the following is not an interns
combustion engine
(a) 2-stroke petrol engine
(b) 4-stroke petrol engine
(c) diesel engine
(d) gas turbine
(e) steam turbine.
Ans: e
36. Pick up the false statement
(a) Thermal efficiency of diesel engine i about 34%
(b) Theoretically correct mixture of air am petrol is
approximately 15 : 1
(c) High speed compression engines operate on
dual combustion cycle
(d) Diesel engines are compression ignition engines
(e) S.I. engines are quality-governed engines.
Ans: e
37. 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) exhaust temperature will be high
(d) engine starts overheating
(e) scavenging occurs.
Ans: e
38. The output of a diesel engine can be increased
without increasing the engine revolution or size in
following way
(a) feeding more fuel
(b) increasing flywheel size
(c) heating incoming air
(d) scavenging
(e) supercharging.
Ans: e
39. It the temperature of intake air in IC engines is
lowered, then its efficiency will
(a) increase
(b) decrease
(c) remain same
(d) increase upto certain limit and then decrease
(e) decrease upto certain limit and then in-crease.
Ans: a
40. 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
(e) none of the above.
Ans: a
41. 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
(e) which is more efficient would depend on engine
capacity.
Ans: a
42. The precess of breaking up or a lipuid into fine
droplets by spraying is called
(a) vaporisation
(b) carburetion
(c) ionisation
(d) injection
(e) atomisation.
Ans: e
43. 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
(e) rate of rise of horse-power.
Ans: b
44. 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 Caront cycles have same
efficiency between same temperature limits
(d) All reversible engines working between same
temperature limits have same-efficiency
(e) Between same temperature limits, both petrol
and diesel engines have same efficiency.
Ans: d
45. Most high speed compression engines operate
on
(a) Diesel cycle
(b) Otto cycle
(c) Dual combustion cycle
(d) Special type of air cycle
(e) Carnot cycle.
Ans: c
48. The accunmulation of carbon in a cylinder
results in increase of
(a) clearance volume
(b) volumetric efficiency
(c) ignition time
(d) effective compression ratio
(e) valve travel time.
Ans: d
49. Which of the following medium is compressed in
a Diesel engine cylinder
(a) air aione
(b) air and fuel
(c) air and lub oil
(d) fuel alone
(e) air, fuel and lub oil.
Ans: a
54. The air-fuel ratio of the petrol engine is
controlled by
(a) fuel pump
(b) governor
(c) injector
(d) carburettor
(e) scavenging.
Ans: d
55. In a typical medium speed, 4-stroke cycle diesel
engine
(a) fuelinjection starts at 10° before to dead center
and ends at 20° after tor 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 deac center
(d) may start and end anywhere
(e) none of the above.
Ans: a
56. 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
(e) none of the above.
Ans: c
57. 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) 150CPC
(e) 2000°C.
Ans: c
58. When crude oil is heated, then which of the
following hydrocarbon is given off first.
(a) kerosene
(b) gasoline
(c) paraffin
(d) diesel
(e) natural gas.
Ans: e
59. The rating of a diesel engine, with increase in
airintlet temperature, will
(a) increase linearly
(b) decrease linearly
(c) increase parabolically
(d) decrease parabolically
(e) first decrease linearly and then increase
parabolically.
Ans: b
60. A 75 cc engine has following parameter as 75 cc
(a) fuel tank capacity
(b) lub oil capacity
(c) swept volume
(d) cylinder volume
(e) clearance volume.
Ans: c
61. A heat engine utilises the
(a) calorific value of oil
(b) low heat value of
(c) high heat value of oil
(d) mean heat value of oil
(e) all of the above.
Ans: c
62. 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
(e) all of the above.
Ans: b
63. Fuel consumption of diesef 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
(e) none of the above.
Ans: c
64. Polymerisation is a chemical process in
which molecules of a compound become
(a) larger
(b) slowed down
(c) smaller
(d) liquid
(e) gaseous.
Ans: a
65. The term scavenging is generally associated
with
(a) 2-stroke cycle engines
(b) 4-stroke cycle engines
(c) aeroplane engines
(d) diesel engines
(e) high efficiency engines.
Ans: e
66. In diesel engine, the compression ratio in
comparison to expansion ratio is
(a) same
(b) less
(G) more
(d) variable
(e) more/less depending on engine capacity.
Ans: c
67. The cam shaft of a four stroke I.C. engine
running at 1500 rmp will run at
(a) 1500 rpm
(b) 750 rpm
(c) 3000 rpm
(d) any value independent of engine speed
(e) none of the above.
Ans: b
68. Engine pistons 'are usually made of aluminium
alloy because it
(a) is lighter
(b) wears less
(c) absorbs shocks
(d) is stronger
(e) does not react with fuel and lub oil.
Ans: a
69. Most high speed compression engines operate
on
(a) Otto cycle
(b) Diesel cycle
(c) Dual cycle
(d) Carnot cycle
(e) Two stroke cycle.
Ans: c
70. The specific fuel consumption of a petrol engine
compared to diesel engine of same H.P. is
(a) same
(b) more
(c) less
(d) less or more depending on operating conditions
(e) unpredictable.
Ans: b
71. A diesel engine as compared to petrol engine
(both running ar rated load) is
(a) more efficient
(b) less efficient
(c) equally efficient
(d) unperdictable
(e) other factors will decide it.
Ans: a
72. The size of inlet valve of.an engine in
comparison to exhaust valve is
(a) more
(b) less
(c) same
(d) more/less depending on capacity of engine
(e) varies from design to design.
Ans: b
74. In a cycle, the spark lasts roughly for
(a) 1 sec
(b) 0.1 sec
(c) 0.01 sec
(d) 0.001 sec
(e) 0.0001 sec.
Ans: d
75. Which of the following is false statement :
Excess quantities of sulphur in diesel fuel are
Objectionable because it may cause the following
(a) piston ring and cylinder wear
(b) formation of hard coating on piston skirts
(c) oil sludge in the engine crank case
(d) detonation
(e) forms corrosive acids.
Ans: d
76. Which of the following is false statement. Some
of the methods used to reduce diesel smoke are as
follows
(a) using additives in the fuel
(b) engine derating i.e. reducing the maxi-mum flow
of fuel
(c) increasing the compression ratio
(d) adherence to proper fuel specification
(e) avoidance of overloading.
Ans: c
77. The fuel air ratio in a petrol engine fitted with
suction carburettor, operating with dirty air filter as
compared to clean filter will be
(a) higher
(b) lower
(c) remain unaffected
(d) unpredictable
(e) none of the above.
Ans: a
78. Pick up the wrong statement about
supercharging
(a) supercharging reduces knocking in diesel
engines
(b) there can be limited supercharging in petrol
engines because of detonation
(c) supercharging at high altitudes is essential
(d) supercharging results in fuel economy
(e) supercharging is essential in aircraft engines.
Ans: d
79. The actual volume of fresh charge admitted in
4-stroke petrol engine is
(a) equal to stroke volume
(b) equal to stroke volume and clearance volume
(c) less than stroke volume
(d) more than stroke volume
(e) more than cylinder volume.
Ans: c
80. The magneto in an automobile is basically
(c) transformer
(b) d.c. generator
(c) capacitor
(d) magnetic circuit
(e) a.c. generator.
Ans: b
81. The reason for supercharging in any engine is to
(a) increase efficiency
(b) increase power
(c) reduce weight and bulk for a given out-put
(d) effect fuel economy
(e) none of the above.
Ans: c
82. The operation of forcing additional air under
pressure in the engine cylinder is known as
(a) scavenging
(b) turbulence
(c) supercharging
(d) pre-ignition
(e) dissociation and carburretion of fuel.
Ans: c
83. Supercharging is essential in
(a) diesel engines
(b) gas turbines
(c) petrol engines
(d) aircraft engines
(e) marine engines.
Ans: d
84. The minimum cranking speed in case of petrol
engine is about
(a) half the operating speed
(b) one-fourth of operating speed
(c) 250-300 rpm
(d) 60-80 rpm
(e) 10-20 rpm
Ans: d
85. In a typical medium speed 4 stroke cycle diesel
engine
(a) exhaust valve opens at 35° before bot-tom dead
center and closes at 20° after top dead center
(b) exhaust valve opens at bottom 'dead center and
closes at top dead center
(c) exhaust valve opens just after bottom dead
center and closes just before top dead center
(d) may open and close anywhere
(e) none of the above is true.
Ans: a
86. Flash point of fuel oil is
(a) minimum temperature to which1 oil is heated
in order to give off inflammable vapours in sufficient
quantity to ignite momentarily when brought in
contact with a flame
(b) temperature at which it solidifies or congeals
(c) temperature at which it catches fire without
external aid
(d) indicated by 90% distillation temperature, i.e.
when 90% of sample oil has distilled off
(e) none of the above.
Ans: a
87. The mean effective pressure obtained from
engine indicator indicates the
(a) maximum pressure developed
(b) minimum pressure
(c) instantaneous pressure at any instant
(d) exhaust pressure
(e) average pressure.
Ans: e
88. For the same power developed in I.C. engines,
the cheaper system is
(a) naturally aspirated
(b) supercharged
(c) centrifugal pump
(d) turbo charger
(e) none of the above.
Ans: b
89. Installation of supercharger on a four-cycle
diesel engine can result in the following percentage
increase in power
(a) upto 25%
(b) upto 35%
(c) upto 50%
(d) upto 75%
(e) upto 100%.
Ans: e
90. Scavenging is usually done to increase
(a) thermal efficiency
(b) speed
(c) power output
(d) fuel consumption
(e) all of the above.
Ans: c
91. Which of the following is the lightest and most
volatile liquid fuel
(a) diesel
(b) kerosene
(c) fuel oil
(d) gasoline
(e) lub oil.
Ans: d
92. The theoretically correct air fuel ratio for petrol
engine is of the order of
(a) 6 : 1
(b) 9 : 1
(c) 12 : 1
(d) 15 : 1
(e) 20 : 1.
Ans: d
93. Air fuel ratio for idling speed of a petrol engine is
approximately
(a) 1 : 1
(b) 5 : 1
(c) 10:1
(d) 15 : 1
(e) 20 : 1.
Ans: c
94. Air fuel ratio at which a petrol engine can not
work is
(a) 8 : 1
(b) 10 : 1
(c) 15 : 1
(d) 20 : 1 and less
(e) will work at all ratios.
Ans: d
95. For maximum power generation, the air fuel
ratio for a petrol engine for vehicles, is of the order
of
(a) 9 : 1
(b) 12 : 1
(c) 15 : 1
(d) 18 : 1
(e) 20: 1.
Ans: b
96. The following volume of air is required for
consuming 1 liter of fuel by a four stroke engine
(a) 1 m3
(b) 5 m3
(c) 5-6 m3
(d) 9-10 m3
(e) 15-18 m3.
Ans: d
97. Pour point of fuel oil is the
(a) minimum temperature to which oil is heated in
order to give off inflammable vapours in sufficient
quantity to ignite momentarily when brought in
contact with a flame
(b) temperature at which it solidifies or congeals
(c) it catches fire without external aid
(d) indicated by 90% distillation temperature i.e.,
when 90% of sample oil has distilled off
(e) temperature at which it flows easily.
Ans: b
98. A 5 BHP engine running at full load would
consume diesel of the order of
(a) 0.3 kg/hr
(b) 1 kg/hr
(c) 3 kg/hr
(d) 5 kg/hr
(e) 10 kg/hr.
Ans: b
99. Diesel engine can work on very lean air fuel
ratio of the order of 30 : 1. A petrol engine can also
work on such a lean ratio provided
(a) it is properly designed
(b) best quality fuel is used
(c) can not work as it is impossible
(d) flywheel size is proper
(e) engine cooling is stopped.
Ans: c
100. A diesel engine has
(a) 1 valve
(b) 2 valves
(b) 3 valves
(d) 4 valves
(e) no valve.
Ans: c
101. A hmh flame speed is obtained in diesel engine
when air fuel ratio is
(a) uniform throughout the mixture
(b) chemically correct mixture
(c) about 3-5% rich mixture
(d) about 10% rich mixture
(e) about 10% lean mixture.
Ans: d
102. The knock in diesel engine occurs due to
(a) instantaneous and rapid burning of the first part
of the charge
(b) instantaneous atuo iginition of last part of charge
(c) delayed burning of the first part of the charge
(d) reduction of delay period
(e) all ot the above.
Ans: a
103. The air-fuel ratio in petrol engines-is
controlled by
(a) controlling valve opening/closing
(b) governing
(c) injection
(d) carburettion
(e) scavenging and supercharging.
Ans: d
104. 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
(e) temperature at which it flows easily.
Ans: d
105. Which is more viscous lub oil
(a) SEA 30
(b) SAE 4£
(c) SAE 50
(d) SAE 70
(e) SAE 80.
Ans: e
106. In the opposed piston diesel engine, the
combustion chamber is located
(a) above the piston (/;) below the piston
(c) between the pistons
(d) any when
(e) there is no such criterion.
Ans: c
107. A stoichiometric air-fuel ratio is
(a) chemically correct mixture
(b) lean mixture
(c) rich mixture for idling
(d) rich mixture for over loads
(e) the ratio used at full rated parameters.
Ans: a
108. 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
(e) forced chamber
Ans: c
109. In loop scavenging, the top of the piston is
(a) flat
(b) contoured
(c) slanted
(d) depressed
(e) convex shaped.
Ans: b
110. 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
(e) reciprocating pump.
Ans: d
111. In order to prevent formation of carbon on the
injector, the temperature of nozzle tip should be
(a) less than 100°C
(b) between 100-250°C
(c) between 250 - 300°C
(d) between 400 - 500°C
(e) between 500 - 1000°C.
11 The thermal efficiency of a petrol engine of two
stroke with crank case scavenging as compared to
four stroke petrol engine with same comperssion
ratio will be
(a) higher
(b) lower
(c) same
(d) depends on size of engine
(e) unpredictable.
113. Ignition quailty of petrol is expressed by
(a) octane number
(b) cetane number
(c) calorific value
(d) self ignition temperature
(e) distillation temperature.
114. Petrol is distilled at a temperature in range of
(a) 30 - 65°C
(b) 65 - 220°C
(c) 220-350°C
(d) 350-450°C
(e) 450-550°C.
115. Kerosene is distilled at
(a) 30 - 65°C
(b) 65 - 220°C
(c) 220 - 350°C
(d) 350 - 450°C
(e) 450-550°C.
116. Self-ignition temperature of petrol is of the
order of
(a) 150°C
(b) 240°C
(c) 370°C
(d) 450°C
(e) more than 500°C.
117. Iso-oct ,ne
(a) has octane number of 0
(b) has octane number of 50
(c) has octane number of 100
(d) is an index of detonation quality
(e) is an index of knocking quality.
118. Octane number is determined by comparing
the performance of the petrol with the following
hydrocarbons
(a) iso-octane
(b) mixture of normal heptane and iso-oc-tane
(c) alpha methyl napthalene
(d) mixture of methane and ethane
(e) mixture of paraffins and aromatics.
119. Cetane
(a) has zero cetane number
(b) has 100 cetane number
(c) helps detonation
(d) is a straight chain paraffin
(e) determines the efficiency of an I.C. engine.
120. Ethyl fluid is used
(a) to increase the octane rating of the fuel
(b) to increase the cetane rating of the fuel
(c) as a defrosting agent
(d) as a superior type of fluid compared to others
(e) to improve lubricating quality of fuel.
121. The self-ignition temperature of diesel oil
compared to petrol is
(a) higher
(b) lower
(c) same
(d) depends on quality of fuel
(e) unpredictable?
112. Normal heptane
(a) accelerates auto-ignition
(b) helps to resist auto-ignition
(c) does not affect auto-ignition
(d) has no relation with auto-ighition
(e) retards auto-ignition.
123. Cetane number is determined by comparing
the performance of diesel oil with the following
hydrocarbons
(a) cetane
(b) mixture of cetane and alphamethyl napthalene
(c) ethylene dibromide
(d) mixture of aldehydes and ketones
(e) mixture of cetane with tetra-ethyl lead
124. Which is correct statement about reaction time
for autoignition of fuel and the fuel air ratio
(a) lean mixture has high reaction time
(b) rich mixture has high reaction time
(c) chemically correct mixture has mini-mum
reaction time
(d) all of the above.
(e) non of the above.
125. Violent sound pulsations within the cylinder of
an I.C. engine are caused due to
(a) heavy turbulence
(b) improved scavenging
(c) heavy supercharging
(d) detonation
(e) preignition.
126. Auto-ignition temperature 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) that at which it catches fire without external aid
(d) indicated by 90% distillation temperature, i.e.,
when 90% of sample oil has distilled off
(e) indicated by 50% distillation temperature.
127. Ignition lag is
(a) the time taken by fuel after injection (before top
dead center) to reach upto auto-ignition
temperature
(b) time before actual fuel injection and the pump
plunger starts to pump fuel
(c) time corresponding to actual injection and top
dead center
(d) time corresopnding to actual ingition and top
dead center
(e) none of the above.
128. The spark plug gap is normally maintained at
(a) 0.1 to 0.2 mm
(b) 0.2 to 0.4 mm
(c) 0.45 to 0.6 mm
(d) 0.6 to 0.8 mm
(e) 0.8 to 1 mm.
129. The function of a fuel pump in a petrol pump is
to
(a) inject fuel in cylinder
(b) supply fuel when carburettor fails
(c) pump fuel so that it reaches carburettor (to
improve thermal efficiency)
(d) does not exist.
130. The delay period in petrol engine is of the order
of
(a) 0.001 sec
(b) 0.002 see
(c) 0.01 sec
(d) 0.05 sec
(e) 0.1 sec.
131. Detonation is caused by the following unstable
compounds
(a) peroxides, aldehydes and ketones
(b) peroxides, aldehydes, oxides and sul-phides
(c) aldehydes, oxides and ketones
(d) ketones and sulphur compounds
(e) none of the above.
13 If overhead clearance is less, then the following
type of engine should be selected
(a) V-type
(b) In-line
(c) Vertical
(d) Horizontal
(e) Radial.
133. Which is false statement about advantages of
V-type engine
(a) compact design requiring lesser space
(b) improved distribution of air to cylinder
(c) casting less liable to distortion
(d) reduced torsional vibration because of shorter
crankshaft
(e) less overhead clearance.
134. The pistons are usually given a coating such
as tin plating in order to
(a) reduce weight
(b) conduct heat efficiently
(c) reduce possibility of scoring
(d) reduce friction
(e) increase lubrication effect.
135. Piston rings are usually made of
(a) cast iron
(b) aluminium
(c) phosphor bronze
(d) babbitt
(e) carbon steel.
136. Piston rings are plated with
chromium,cadmium or phosphate in order to
(a) reduce cost
(b) improve surface finish
(c) prevent clogging
(d) reduce wear and eliminate scuffing
(e) improve heat transfer.
137. The top piston ring nearer to the piston crown
is known as
(a) compression ring
(b) oil ring
(c) scrapper ring
(d) groove ring
(e) leading ring.
138. In order to prevent knock in the S.I. engines,
the charge away from the spark plug should have
(a) low temperature
(b) low density
(c) long ignition delay
(d) rich mixture
(e) all of the above.
139. Diesel engines have low specific fuel
consumption compared to petrol engine. This
statement is
(a) not true
(b) true at full load
(c) true at part load
(d) true at both part and full load
(e) there could not be any such criterion.
140. To reduce the possibility of knock in the C.I.
engines, the first elements of fuel and air should
have
(a) high temperature
(b) high density
(c) short delay
(d) reactive mixture
(e) all of the above.
141. The detonation tendency in petrol engines for
specified conditions of fuel rating, compression
ratio, speed etc. can be con-trolled by having
(a) smaller cylinder bore
(b) bigger cylinder bore
(c) medium cylinder bare
(d) cylinder bore could be anything as it does not
control detonation
(e) proper stroke legth.
142. According to Recardo's theory, detonation
occurs due to
(a) instantaneous auto-ignition of last part of charge
to be burnt
(b) improper mixing of air and fuel
(c) improper combustion
(d) self ignition temperature has nothing to do
with detonation
(e) none of the above.
143. A fuel will detonate less if it has
(a) higher self ignition temperature
(b) lower self ignition temperature
(c) proper self ignition temperature
(d) self ingition temperature has nothing to do with
detonation
(e) none of the above.
144. The knocking in diesel engines for given fuel,
will be
(a) enhanced by increasing compression ratio
(b) enhanced by decreasing compression ratio
(c) unaflected by compression ratio
(d) first enhanced by increasig compression ratio
upto a limit beyond which it will be suppressed
(e) dependent on other factors.
145. The ignition of charge by some hot surface in
the engine cylinder before operation of spark plug is
known as
(a) auto ignition
(b) preignition /
(c) retarded ignition
(d) accelerated ignition
(e) detonation.
146. Injection lag is
(a) the time taken by fuel after injection (before top
dead center) to reach upto auto-ignition
temperature
(b) time before actual fuel injection and the pump
pluger starts to pump fuel
(c) time corresponding to actual injection and top
dead center
(d) time corresponding to actual ignition and top
dead center
(e) none of the above.
147. Ignition quality of diesel-fuel oil is expressed
by an index called
(a) octane number
(b) cetane number
(c) calorific value
(d) carbon content
(e) ignition temperature.
148. For best results of efficient combustion, high
speed diesel engines need an approximate cetane
number of
(a) 100
(b) 10
(c) 50
(d) 5
(e) 1.
149. Calorific value of diesel oil is of the order of
(a) 3000 kcal/kg
(b) 5000 kcal/kg
(c) 7500 kcal/kg
(d) 10000 kcal/kg
(e) 15000 kcal/kg.
150. Carbon residue in diesel oil should not be more
than
(a) 1%
(b) 0.5%
(c) 0.1%
(d) 0.01%
(e) 0.001%.
151. The most popular firing order in case of four
cylinder in-line I.C. engine is
(a) 1-2-3-4
(b) 1-3-2-4
(c) 1-4-2-3
(d) 1-2-4-3
(e) 1-3-4-
15 The compression ratio of motor cars is
(a) 5
(b) 1
(c) 10
(d) 13
(e) 16.
153. The specific gravity of diesel oil Is
(a) 1
(b) 0.7
(c) 0.85
(d) 0.5
(e) 1.25.
154. Freezing temperature of petrol is usually
(a) 0°C
(b) - 10°C
(c) 10°C
(d) less than - 30°C
(e) less than - 273°C.
155. The specific gravity of petrol is about
(a) 0.65
(b) 0.75
(c) 0.85
(d) 0.95
(e) 1.1.
156. Pick up the correct statement. Detonation can
be controlled by
(a) varying compression ratio
(b) using lian mixture
(c) retarding the spark timing
(d) reducing the r.p.m.
(e) increasing inlet pressure.
157. The efficiency of I.C. engines normally is of the
order of
(a) 15-20%
(b) 20-25%
(c) 25-30%
(d) 30-35%
(e) 35-50%.
158. The firing order in a six stroke I.C. engine is
(a) 1-3-6-5-2-4
(b) 1-4-2-5-6-3
(c) 1-6-2-5-4-3
(d) 1-5-2-6-3-4
(e) 1-5-3-4-2-6.
159. Sulphur content in diesel oil should not be more
than
(a) 10%
(b) 5%
(c) 1%
(d) 0.1%
(e) 0.01%.
160. The m.e.p. of a diesel cycle having fixed
compression ratio with increase in cut-off will
(a) increase
(b) decreae
(c) be unaffected
(d) depend on other factors
(e) unpredictable.
161. The ash content in diesel oil should bot be
more than
(a) 1%
(b) 5%
(c) 0.1%
(d) 0.01%
(e) 0.001%.
16 The pour point of diesel oil must be
(a) lower than the coldest atmospheric temperature
at which oil is to be pumped
(b) higher than above
(c) has no such relation
(d) more than 100°C
(e) none of the above.
163. High carbon content in diesel oil used for diesel
engine leads to
(a) production of highly corrosive gases corroding
the cylinder walls and exhaust system
(b) excessive engine wear
(c) damaging of both the storage tank and the
engine
(d) deposition on engine parts
(e) none of the above.
164. Exhaust pipes of engines are covered with
insulating marterial in order to
(a) keep the exhaust pipes warm
(b) reduce formation of condenstae
(c) reduce heat transfer to the engine room
(d) increase engine efficiency
(e) conserve heat.
165. Ignition timing of a multicylider petrol engine
can be adjusted by
(a) rotating the crank
(b) adjusting the spark plug gap
(c) adjusting ignition coil position
(d) rotating the distributor
(e) delaying the spark by increasing capacitor in
ignition circuit.
166. Fuel consumption with increase in back
pressure will
(a) increase
(b) decrease
(c) remain unaffected
(d) depend on other factors
(e) none of the above.
167. The cooling water requirement for diesel
engine is of the order of
(a) 0.2 to 1.0 liter per minute per h.p.
(b) 1 to 3 liters per minute per h.p.
(c) 5 to 10 liters per minute per h.p
(d) 10 to 20 liters per minute per h.p.
(e) 20-30 liters per minute per h.p.
168. A 4-stroke diesel engine needs about following
amount of air
(a) 75 cc per min. per h.p.
(b) 750 cc per min. per h.p.
(c) 7500 cc per min. per h.p.
(d) 75000 cc per min. per h.p.
(e) 750000 cc per min. per h.p.
169. Leakage past the piston rings and valve seats
in I.C. engines with increase in speed
(a) increases .
(b) decreases
(c) remains same
(d) unpredictable
(e) none of the above.
170. The heat wasted in diesel engine is of the
order of
(a) 80%
(b) 65%
(c) 50%
(d) 35%
(e ) 25%.
171. With increa.se in speed of vehicle, the back
pressure will
(a) decrease
(b) increase
(c) remain unalfected
(d) depend on other factors
(e) none of the above.
17 The function of a distributor in an automobile is
to
(a) distribute charge, equally to all the cylinders
(b) regulate power
(c) feed lub oil to all moving parts
(d) time the spark
(e) inject fuel at appropriate time.
173. The ratio of useful power; engine friction
exhaust gas losses; cooling water, air and oil losses
for a diesel engine is of the order of
(a) 5:25:30:50
(b) 25:35:5:35
(c) 25:5:10:60
(d) 40:30:15:15
(e) 25:5:35:35.
174. For same power and same speed, the flywheel
of a four stroke engine as compared to two-stroke
I.C. engine will be
(a) smaller
(b) bigger
(c) same size
(d) dependent on other engine parameters
(e) unpredictable.
175. Air injection in I.C. engines refers to injection of
(a) air only
(b) liquid fuel only
(c) liquid fuel and air
(d) supercharging
(e) does not exist.
176. Solid injection in I.C. engines refers to injection
of
(a) liquid fuel only
(b) liquid fuel and air
(c) solid fuel
(d) solid fuel and air
(e) does not exist.
177. The system of lubrication used for motor
cycles and scooters is by
(a) forced lubrication system
(b) splash lubrication
(c) applying grease under pressure
(d) wet sump method
(e) mixing about 5% lub oil with petrol.
178. The m.e.p. of a petrol engine first increases as
the fuel air ratio is increased and then decreases on
further increase in fuel air ratio. The m.e.p. is
maximum in the zone of
(a) lean mixture
(b) chemically correct mixture
(c) rich mixture
(d) unpredictable
(e) none of the above.
179. The specific fuel consumption for a petrol
engine first decreases with increase in fuel air ratio
and then increases with further increase in fuel air
ratio. The minimum value occurs in the range of
(a) lean mixture
(b) chemically correct mixture
(c) rich mixture
(d) unpredictable
(e) none of the above.
180. The thermal efficiency of a two cycle engine as
compared to four cycle engine is
(a) more
(b) less
(c) same
(d) more upto some load and then less
(e) it may be less or more depending on several
other factors.
181. Diesel engines as compared to petrol engines
require
(a) bigger flywheel
(b) smaller flywheel
(c) same size flywheel
(d) no flywheel
(e) flywheel whose size may be less or more
depending on several other fac-tors.
183. The tendency of a diesel engine to knock
increases, if
(a) engine speed is increased
(b) engine H.P. is increased
(c) octane number of fuel is increased
(d) conperssion ratio is increased
(e) engine has to move uphill.
184. The tendency of a petrol engine to knock
increases by
(a) supercharging
(b) scavenging
(c) increasing engine H.P,
(d) reducing the spark advance
(e) increasing cetane number of fuel.
185. Free acids in diesel oil for diesel engine lead to
(a) production of highly corrosive gases corroding
the cylinder walls and exhaust system
(b) excessive engine wear
(c) damaging of both the storage tank and the
engine
(d) deposition on engine parts
(e) excessive fuel consumption.
186. Thermal efficiency of high speed diesel engine
at design load may be of the order of
(a) 20%
(b) 35%
(c) 50%
(d) 70%
(e ) 85%.
187. The thermostat in I.C. engines permitting hot
water to go to radiator is set around
(a) 70-80°C
(b) 80-85°C
(c) 85-95°C
(d) above 100°C
(e) above 120°C.
188. The brake mean effective pressure of an I.C.
engine with increase in speed will
(a) increase
(b) decrease
(c) remain unaffected.
(d) fluctuate according to engine speed
(e) unpredictable.
189. High ash and sediment in diesel oil used in
diesel engine lead to
(a) production of highly corrosive gases corroding
the cylinder walls and ex-haust system
(b) excessive engine wear
(c) damaging of both the storage tank and the
engine
(d) deposition on engine parts
(e) blocking of exhaust pipes.
190. Mixing of fuel and air in case of dies engine
occurs in
(a) injection pump
(b) injector
(c) inlet manifold
(d) carburettor
(e) engine cylinder.
191. The advantage of reversing the flow of a in an
air cleaner is to
(a) increase velocity of air
(b) increase air flow
(c) reduce the velocity of air
(d) throw out a large percentage of foreig matter
(e) cool the air.
19 The most effective air cleaner in case diesel
engines is
(a) dry type
(b) wet type
(c) whirl type
(d) oil bath type
(e) all are equally good.
193. Fins are provided over engine cylinder
scooters for
(a) higher strength of cylinder
(b) better cooling
(c) good appearance
(d) higher efficiency
(e) easier handling and ease in manufacturing.
194. The elements of most concern in regard
pollution caused by engines are
(a) CO and C02
(b) CO and hydrocarbons
(c) C02 and hydrocarbons
(d) carbon and dust
(e) hot products of combustion
195. The preferred location of an oil cooler is
(a) before the filters
(b) after the filters
(c) between the filters
(d) before and after the filters
(e) any where.
196. The petrol from tank to the automotive ergine
is fed by
(a) gravity
(b) pump run by engine
(c) suction pressure created by, suctio stroke
(d) capillary action
(e) fuel pump.
197. In petrol engine, increase of cooling water
temperature will
(a) increase the knocking tendency
(b) decrease the knocking tendecny
(c) not affect the knocking tendency
(d) increase or decrease knocking tendency
depedning on strength and time of spark
(e) unpredictable.
207. In carburettors, the top of the fuel jet with
reference to the level in the float chamber is kept at
(a) same level
(b) slightly higher level
(c) slightly lower level
(d) may be anywhere
(e) varies from situation to situation.
208. Carburretion is done to
(a) feed petrol into cylinder
(b) govern the engine
(c) break up and mix the petrol with air
(d) heat up the charge to cylinder
(e) scavenge the cylinder.
209. Power impulses from an I.C. engine are
somoothed out by
(a) governor
(b) crank shaft
(c) gear box
(d) flywheel
(e) timing spark properly.
210. The theoretically correct mixture of air and
petrol is approximately
(a) 8 : 1
(b) 12 : 1
(c) 15 : 1
(d) 20 : 1
(e) 24: 1.
211. For low speed operation or for idling in petrol
engines, the engine requirements are for
(a) lean mixture
(b) theoretically correct mixture
(c) rich mixture
(d) any type of mixture
(e) lean/rich mixture depending upon capacity of
engine.
21 In petrol engines, advancing the spark timing will
(a) increase the knocking tendency
(b) decrease the knocking tendency
(c) not affect the knocking tendncy
(d) increase or decrease knocking tendency
depending on strenght and time of spark
(e) unpredictable.
213. The following type of carburettor is preferred
(a) concentric type
(b) eccentric type
(c) horizontal type
(d) vertical type
(e) none of the above.
214. In the passanger cars, the following type of
carburettor is preferred
(a) horizontal type
(b) downward draught type
(c) upward draught type
(c) inclined draught type
(e) any one of the above types.
215. The essential equipment for producing high
vlotage for sparking in petrol engines with battery is
(a) ignition coil
(b) ignition coil and distributor
(c) ignition coil and condenser
(d) ignition coil and contact breaker
(e) ignition coil, contact breaker and con-denser.
216. The ignition coil in diesel engines produces
voltage of the order of
(a) 6 to 12 volts
(b) 240 volts
(c) 1000 volts
(d) 20,000 volts
(e) 80,000 volts.
217. If the door of a diesel engine crankcase is
opened just after shutdown before cooling of engine,
then
(a) efficiency of engine will be poor
(b) there is a risk of explosion taking place
(c) it is the safest practice
(d) some parts may be subjected
(e) some lub oil may be wasted.
218. The thermal efficiency of a diesel engine is of
the order of
(a) 92%
(b) 68%
(c) 52%
(d) 34%
(e) 25%.
219. The thermal efficiency of a gas engine is of the
order of
(a) 92%
(b) 68%
(c) 52%
(d) 34%
(e) 25%.
220. Theoretically, the following engine should have
maximum efficiency
(a) gas engine
(b) 2-stroke S.I. engine
(c) 4-stroke S.I. engine
(d) steam engine
(e) 4-stroke C.I. engine.
221. In petrol engine using a fixed octane rating fuel
and fixed compression ratio, super charging will
(a) increase the knocking tendency
(b) decrease the knocking tendency
(c) not affect the knocking tendency
(d) increase or decrease knocking tendency
depending on strength and time of spark
(e) unpredictable.
223. High sulphur content in diesel oil used for
diesel engines leads to
(a) production of highly corrosive gases corroding
the cylinder walls and exhaust system
(b) excessive engine wear
(c) damaging of both the storage tank and the
engine
(d) deposition on engine parts
(e) reduction in thermal efficiency.
224. In open combustion chamber in diesel engines
(a) the shape and layout of the piston crown, the
inlet port, and the valve produce the turbulent effect
on fuel mixture
(b) fuel is injected into an auxiliary chamber that is
separated from the cylinder by an orifice or throat
(c) only a part of air charge is contained in an
auxiliary chamber in which the fuel starts to burn
with insufficient air which due to explosion tendency
mixes thoroughly into main cylinder charge
(d) fuel is injected at atmospheric pres¬sure
(e) there are no valves.
225. The basic requirement of a good combustion
chamber is
(a) high compression ratio
(b) low compression ratio
(c) low volumetric efficiency
(d) minimum turbulence
(e) high power output and high thermal efficiency.
226. Deposition of carbon in petrol engine cylinder
would result in increase of
(a) clearance volume
(b) swept volume
(c) compression ratio
(d) volumetric efficiency
(e) mean effective pressure.
227. Which of the following engines can work on
very lean mixture
(a) S.I. engine
(b) C.I. engine
(c) two stroke engine
(d) four stroke engine
(e) all of the above.
228. If petrol is used in a diesel engine, then
(a) higher knocking will occur
(b) efficiency will be low
(c) low power will be produced
(d) black smoke will be produced
(e) lot of fuel will remain unburnt.
229. Hot air standard diesel cycle efficiency with
increase in value of C„
(a) increases
(b) decreases
(c) remains unaffected
(d) depends on other factors
(e) unpredictable.
230. In turbulence chamber in diesel engine
(a) the shape and layout of the piston crown, the
inlet port, and the valve produce the turbulent effect
of fuel mixture
(b) fuel is injected into an auxiliary chamber that is
separated from the cylinder by an orifice or throat
(c) only a part of air charge is contained in an
auxiliary chamber in which the fuel starts to burn
with insufficient air which due to explosion tendency
mixes thoroughly into main cylinder charge
(d) there are no valves
(e) fuel is partly burnt by spark.
231. For low load operation, more suitable
(economical) engine is
(a) S.I. engine
(b) C.I. engine
(c) both are equally good
(d) multicylinder engine
(e) two stroke engine.
232. A two stroke crank compressed engine has
following ports in the cylinder
(a) suction port and exhaust port
(b) transfer port only
(c) suction port and transfer port
(d) transfer port and exhaust port
(e) suction port, exhaust port and transfer port.
233. For the same size and weight, a two stroke
engine as compared to four stroke engine will
generate power
(a) about twice
(b) about 0.5 times
(c) nearly equal
(d) about 1.7 times
(e) about 5 times.
234. A two stroke engine is usually identified by
(a) size of flywheel
(b) weight of engine
(c) type of lubrication system
(d) absence of valves
(e) location of fuel tank.
235. If diesel is fed by mistake in the oil tank of a
petrol engien, then engine will
(a) give lot of smoke
(b) detonate
(c) knock
(d) not run
(e) run for some time and then stop.
236. The thermal efficiency of a semi-diesel cycle
having fixed compression ratio and fixed quantity of
heat, with increase in pressure ratio will
(a) increase
(b) decrease
(c) remain unaffected
(d) increase/decrease depending upon engine
capacity
(e) first increase and then decrease.
245. The termal efficiency of a petrol engine at
design load is around
(a) 90%
(b) 50%
(c) 40%
(d) 30%
(e) 15%.
246. In isochronous governing, speed droop is
(a) 100%
(b) 50%
(c) 5%
(c) 30%
(e) 1%.
247. Method of governing used in petrol engine is
(a) quantity governing
(b) quality governing
(c) combined governing
(d) partial governing
(e) hit and miss governing.
248. Pick up false statement
(a) For petrol and large gas engines, quantity
governingds preferred
(b) In quantity governing, air fuel ratio is almost
constant and quantity of charge is changed
depending on load
(c) In hit and miss governing, fuel supply is
completely cut off during one or more number of
cycles
(d) In quality governing, quantity of fuel is varied to
suit the load and total charge of air is varied
(e) For close regulation of speed, combination of
both quality and quantity governing is used.
249. Method of governing used in diesel engine is
(a) quantity governing
(b) quality governing
(c) combined governing
(d) partial governing
(e) nit and miss governing.
250. An engine has a normal speed of 960 r.p.m.
and no load speed of 1000 r.p.m. The speed droop of
governor will be about
(a) 2%
(b) 4%
(c) 8%
(d)±4%
(e) 1%.
