Objectives of IC Engine

1. IC Engines
01. Basic of IC Engines
Objectives by:- Prakash shakti
1. Advantages of reciprocating IC engines over steam turbine is –
Mechanical simplicity, improved plant efficiency & Lower average temperature.
2. The intake charge in a diesel engine consists of –
Air alone.
3. Engine of different cylinder dimensions, power & speed can be compared on the basis of –
Mean effective pressure.
4. Disadvantages of reciprocating IC engine are –
Vibration, Use of fossils fuels & Balancing problems.
5. Gudgeon pin forms the link between –
Piston & small end of connecting rod.
6. An IC engine gives an output of 3 kW when the input is 10,000 J/s. The thermal efficiency of the engine is –
30%
7. In a 4-stroke IC engine cam shaft rotates at –
Half the speed of crankshaft.
8. Thermal efficiency of CI engine is higher than that of SI engine due to –
Higher compression Ratio.
9. SI engines are of –
Light weight, High speed & Homogeneous change of fuel & oil.
10. Compression ratio in diesel engines is of the order of –
14-20
11. In a reciprocating engine with a cylinder diameter of D and Stroke of L, the cylinder volume is –
π/4 D2L + clearance volume.
12. Main advantages of a 2-stroke engine over 4-stroke engine is –
More uniform torque on the crankshaft, amore power O/P for the cylinder of same dimension & Absence of
valves.
13. Engines used for ships are normally –
2-stroke CI engines of very high power.

2. 14. If L is the stroke & N is the rpm, mean piston speed of 2-stroke engine is -
2LN
15. Equivalence ratio is –
Stoichiometric fuel – air ratio / actual fuel – air ratio
16. The volumetric efficiency of the SI engine is comparatively –
Lower than CI engine.
17. The range of volumetric efficiency of a –
85 – 90%
18. Relative efficiency is the ratio of –
Actual thermal efficiency / air – standard efficiency.
19. Brake specific fuel consumption is defined as –
Fuel consumption per brake power hour.
20. Engine can be fired with –
Solid fuel, liquid fuel or gaseous fuel.
21. The unit of force in SI units is –
Newton.
22. First law of thermodynamics define a property called –
Energy.
23. Specific value of any property is its value –
Per unit mass.
24. Second law of thermodynamics define the property called –
Entropy.
25. Unit of universal gas constant is –
KJ / kmol K
26. A constant volume process –
Heat supplied = change in internal energy.
27. A constant pressure process –
Heat transfer = change in enthalpy.
28. In an isothermal process –
Heat transfer = work done
29. In a reversible adiabatic process –
Entropy = constant

3. 30. At critical point the latent heat of vaporization is –
Zero
31. The internal energy of an ideal gas is –
A function of its temperature alone.
32. Property of system –
Pressure, temperature & entropy.
33. An isochoric process is a –
Constant volume process
34. An isobaric process is a –
Constant pressure process.
35. An isothermal process is a –
Constant temperature process.
36. An isentropic process is a –
Constant entropy process.
02. Air-Standard Cycles
37. Efficiency of strilling cycle is same as –
Carnot cycle.
38. The air standard Otto cycle consists of –
2 constant volume & 2 isentropic processes.
39. Mean effective pressure of Otto cycle is –
Directly proportional to pressure ratio.
40. For a given compression ratio the work )/P of Otto cycle is –
Increases with increase in r.
41. For a given value of r, efficiency of Otto cycle is –
Increases with compression ratio.
42. For dual combustion cycle for fixed value of heat addition & compression ratio –
mep will be greater with increase in rp & decrease in re.
43. The normal range of compression ratio for Otto cycle is –
6 to 10
44. The normal range of compression ratio for Diesel cycle is –
15 to 20
45. Lenoir cycle is used in –
Pulse jet engines.

4. 46. A brayton cycle consists of –
1 constant pressure, 1 constant volume & 2 isentropic processes.
47. Brayton cycle is used in –
Gas turbines.
03. Fuel-Air cycles & Actual cycles
48. The actual efficiency of a good engine is about –
85%
49. With dissociation peak temperature is obtained –
When the mixture is slightly lean.
50. With dissociation the exhaust gas temperature –
Decreases.
51. Fuel-air ratio affects maximum power O/P of the engine due to –
Higher specific heats & Chemical equilibrium losses.
52. Mean effective pressure at a given compression ratio is maximum when the air-fuel ratio is –
Lower than stoichiometric.
53. For a compressure process with variable specific heat the peak temperature & pressure are –
Lower.
54. Dissociation can be considered as –
Disintegration of combustion products at high temperature, reverse process of combustion or heat absorption
process.
55. When the mixture is lean –
Power O/P is less.
56. For a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure –
Initially increases & then decreases.
57. Time loss factor in actual cycle is due to –
Progressive combustion.
58. If the spark timing is at TDC, the work is less as –
The peak pressure is low.
59. When the spark is advanced, work O/P is less as –
Addition work is required to compress the burning gas.
60. Optimum spark timing gives –
Higher mean effective pressure & higher efficiency.
61. The major loss in a SI engine is due to –

5. Variation in specific heat & chemical equilibrium.
62. Fuel-air cycle efficiency is less than air-standard cycle efficiency by an amount equal to –
Loss due to specific heat variation & chemical equilibrium.
63. The major loss in CI engine is –
Loss due to incomplete combustion.
64. The ratio of the actual efficiency & the fuel-air cycle efficiency for CI engines is about –
0.6-0.8
65. In actual SI engine the pumping loss with respect to speed –
Increases.
66. The volumetric efficiency is affected by –
The exhaust gas in the clearance volume, the design of intake & exhaust valve or valve timing.
04. Fuels
67. Advantages of gaseous fuel is that –
It can mix easily with air.
68. Paraffin’s are in general represented by –
CnH2n+2
69. paraffin’s have molecular structure of –
Chain saturated.
70. Olefins are represented by the formula –
CnH2n
71. Hydrocarbons are decomposed into smaller hydrocarbons by –
Cracking.
72. The molecular structure of the straight run gasoline is changed by –
Reforming.
73. For SI engines fuels most preferred are –
Aromatics.
74. For CI engines fuels most preferred are –
Paraffins
75. Octane number of iso-octane is –
100
76. Ignition quality of diesel fuel is indicated by its –
Cetane number.
05. Alternate Fuels

6. 77. Gasohol is a mixture of –
10% ethanol + 90% gasoline
78. Stoichiometric air-fuel ratio of alcohol when compared to gasoline is –
Lower.
79. Small amount of gasoline is often added to alcohol to –
To improve cold weather starting.
80. Methanol by itself is not a good CI engine fuel because –
Its octane number is high & its cetane number is low.
81. Anti-knock characteristics of alcohol when compared to gasoline is –
Higher.
82. Alcohols alone cannot be used in CI engines as –
Their self-ignition temperature is high & latent heat of vaporization is high.
83. Advantage of hydrogen as an IC engine fuel –
No HC & CO emissions.
84. Disadvantage of hydrogen as a fuel in IC engine –
Detonating tendency.
85. Major constituent of natural gas is –
Methane
86. Octane number of natural gas is –
>100
87. Major disadvantage of LPG as a fuel in automobile is –
Reduction in life of the engine & less power compared to a gasoline.
88. Advantage of LPG as fuel in automobiles –
Engine has longer life when running on LPG.
89. Compared to diesel, biomass fuels have the advantages of –
Lower emission & easy availability.
90. Biomass fuels suffer from the disadvantage of –
Low energy content & high specific fuel consumption.
06. Carburetion
91. Stoichiometric air-fuel ratio of petrol is roughly –
15:1
92. Venturi in the carburetor results in –
Increase of air velocity.
93. The choke is closed when the engine is –

7. Cold
94. Lean air mixture is required during –
Cruising
95. The limits of air-fuel for SI engine are
8/1 to 18/1
96. In a SI engine for maximum power, the relative fuel -air ratio is –
1.2
97. For maximum thermal efficiency, the fuel-air mixture in SI engines should be –
Lean
98. During starting petrol engine require –
Rich mixture
99. For petrol engine the method of governing is –
Quantity governing.
00. Economizer is used to provide enriched mixture during –
Full throttle opening.
01. When the throttle is suddenly opened, the mixture from the simple carburetor tends to become –
Lean.
02. Precise petrol injection system is –
Throttle body injection.
03. The choke in an automobile meant for supplying –
Rich mixture.
04. Modern carburetors provide the correct quality of air-fuel mixture during –
Starting, idling & cruising.
05. A simple carburetors supplies rich mixture during –
Accelerating.
06.Mechanical Injection Systems
07. Fuel injector is used for –
CI engines
08. Advantage of air injection system is –
Cheaper fuels can be used, mep is high & fine atomization and distribution of the fuel.
09. Commonly used injection system in automobiles is –
Solid injection.
10. Fuel injection pressure in solid injection system is around –

8. 200-250 bar
11. Fuel filters do not use generally –
Paper
12. Fuel is injected in a 4-stroke CI engine –
At the end of compression stroke.
13. Injection system in which the pump and the injector nozzle is combined in one housing is known as –
Unit injector system.
14. Main advantage of pintaux nozzle is –
Better cold starting performance.
15. The most accurate gasoline injection system is –
Port injection.
16. Advantage of fuel injection in SI engine is –
Increased volumetric efficiency.
07. Electronic Injection System
17. Multi-point fuel injection system uses –
Port injection & throttle body injection.
18. L-MPFI system uses –
Port injection.
19. D-MPFI system use –
Manifold injection.
20. Common rail injection system uses injection pressures of the order –
1500 bar
21. Continuous injection system usually has –
Rotary pump.
22. The cold start injector –
Gives rich air-fuel ratio.
23. ECU is an electronic injection system used for –
Calculating the appropriate injection timing.
24. With EFI of diesel engines –
Very high injection pressure can be obtained.
25. EFI system can achieve –
Proper injection timing, Proper injection quantity & Proper injection pressure.

9. 08. Ignition
26. The secondary winding of ignition coil consists of –
Many turns of fine wire.
27. Dwell is the time –
For which the points remain closed.
28. Dwell period –
Is inversely proportional to engine speed.
29. If the contact breaker gap is small, it results in –
Rapid burning of the pointer gaps.
30. For a four cylinder engine operation at N rpm, the conytact breaker must make and break the circuit.
2N times.
31. Contact breaker should be set –
After adjustment of dwell angle.
32. Dwell meter is used for –
Contact breaker gap.
33. For a four cylinder vertical engine, the commonly used firing order is –
1-3-4-2
34. For engine operating with rich mixture the optimum spark timing.
Must be advanced.
35. For peak lead operation. The spark advance –
Must be increased.
36. Ignition timing is adjusted by –
Stroboscopic light.
37. Vacuum advance mechanism shifts the ignition point under –
Part load operation.
38. Battery ignition system –
Occupies more space, has more maintenance problem & is commonly employed in 4-Wheeler.
09. Combustion & Combustion Chamber
39. In SI engines maximum flame speed is obtained when the equivalent ratio is between –
1.1 and 1.2

10. 40. In SI engine flame speed increases –
With turbulence & with fuel-air ratio.
41. With increase in compression ratio flame speed –
Increases.
42. With increase in speed the crank angle required for flame propagation –
Not affected.
43. Increasing the compression ratio in SI engines the knocking tendency –
Increases.
44. Decreasing the cooling water temperature in SI engines the knocking tendency –
Decreases.
45. Detonation in SI engines occur due to –
Auto ignition of the charge after the spark in struck.
46. Desirable characteristics of the combustion chamber for SI engines to avoid knock is –
Small bore, short ratio of flame path to bore & absence of hot surface in the last region of the charge.
47. In CI engines with increase in compression ratio the delay period –
Decreases.
48. Knocking takes place in CI engines –
At the start of combustion.
49. In CI engines knocking tendency increases with –
Decrease in compression ratio.
50. In CI engines by increasing inlet air pressure the knocking tendency –
Decreases.
51. Open combustion chambers in CI engines require –
High injection pressures & accurate metering of fuel by the injection system.
52. The advantages of the indirect injection combustion chambers are –
Low injection pressure & direction of spray is not critical.
53. In CI engines the delay period is affected by –
Compression ratio, engine speed & output.
10. Engine Friction & Lubrication
54. Mechanical efficiency is the ratio of –

11. Brake power to indicated power.
55. Most commonly used lubrication system in automobiles is the –
Pressure system.
56. Friction that occurs between the layers of oil film is called –
Viscous friction.
57. Crankcase ventilation is provided –
To remove blow by.
58. The most important property of lubricant is –
Viscosity.
59. The maximum pressure in the lubrication system is controlled by –
Valve relief.
60. The lubricants commonly used in the automobiles are –
Mineral oils.
61. Detergents are oil additives used to –
Prevent sludge formation.
62. Oil pressure in the dry sump lubrication system is around –
3bar – 8 bar.
63. F mep decreases when using –
Larger number of smaller cylinders.
64. With increase in compression ratio, mechanical efficiency –
Increases.
65. Blow by losses are –
Proportional to the square root of inlet pressure.
66. Most lubrication system is mainly used in –
Two-stroke petrol engine.
67. Additives are added in lubricant to have –
Detergent-dispersant characteristics, pour point depression & antifoam characteristics.
11. Heat Rejection & Cooling
68. The heat given to cooling medium in IC engine is about –
30 – 40%
69. Radiator is provided to –
Cool the jacket water.

12. 70. Thermostat is used in radiators to –
Control the water temperature.
71. As the compression ratio increases, there is a –
Marginal reduction in heat rejection.
72. Spark timing other than minimum spark advance for heat torque (MBT) results in –
More heat rejection.
73. Direct system of cooling air is one which –
Hot water is simply discharged.
74. In evaporate cooling systems, heat absorbed per kg of coolant air is equal to –
Latent heat of the coolant.
75. Pump used in the forced cooling system in normally –
Centrifugal pump.
76. Advantage of liquid cooling system is –
Even cooling.
77. Limitation of air cooling system are –
Higher working temperature compared to water cooling.
78. The main purpose of a thermostat in an engine cooling system is to –
Allow engine to warm-up quickly.
79. The radiator cooling tubes are generally made of –
Copper.
80. Water circulation in a thermo syphon cooling system is due to –
Conduction currents.
81. The main purpose of fan in a liquid cooling system is to –
Pump cold air over the hot water.
82. Engine overheating may be due to –
Broken fan belt.
12. Engine Emissions & Their Controls
83. Strictest emission norms are initiated in the world first in –
California.
84. One of the major exhaust emissions from CI engines compared to SI engine is –
Particulates.

13. 85. Decrease In air-fuel ratio in SI engines results in –
Increase of CO and UBHC.
86. NOx emission is maximum in SI engines when the air-fuel ratio is –
Nearly stoichiometric.
87. NOx emission in SI engines will be lowest during –
Idling.
88. Photochemical smog is mainly due to –
NOx and HC
89. Alcohol is the major source for the emission of –
Aldehydes.
90. Fumigation technique is used to control –
Smoke.
91. Blue smoke in diesel engine indicates –
Unburnt oil.
92. Thermal converters cannot reduce emission of –
NOx
93. Three way catalytic converters reduce emission of –
CO, NOx and HC
94. Platinum and Rhodium promote the oxidation of –
CO, HC
95. Rhodium promotes the reduction of –
NOx
96. Efficient operation of catalytic converters require maintenance of –
Temperature and equivalence ratio.
97. EGR is the most effective way of reducing emission of –
NOx
98. EGR has disadvantage of –
Decreasing thermal efficiency & increasing HC emission.
99. Evaporative emission in SI engines account for emission of –
25% HC

14. 00. Chemiluminescene technique is used to measure –
NOx
01. Lead compounds were added in gasoline to –
Reduce knocking.
13. Measurements & Testing
02. The range of mechanical efficiency for automobile engines is –
70-80%
03. The measurement of frictional power by willans line is applicable only to –
CI engines at a particular speed.
04. Morse test is applicable only to –
Multicylinder CI engines.
05. The most accurate method of determining f p is by –
Measurement of brake & indicated power.
06. In the air box method of measuring air flow, the air box is provided to –
Damp out the pulsations.
07. The air box/swept volume ratio should be in the range for angle cylinder engine –
500-600%
08. The best method of measuring speed is by –
Magnetic pickup.
09. Flame ionization detector is used for measuring –
HC
10. Non-dispersive infra-red analyzer is widely accepted instrument for measuring –
CO
14. Performance Parameters & Characteristics
11. Thermal efficiency varies –
Inversely as s f e.
12. Mechanical efficiency is ratio of –
Bp to ip
13. The spark timing & combustion rate should be such that –

15. One half of the total pressure occurs at TDC.
14. Volumetric efficiency is a measure of –
Breathing capacity of the engine.
15. Indicated power is directly proportional to –
Air consumption.
16. Brake thermal efficiency of SI engine is in the range –
25% to 35%
17. Sankey diagram represents –
Heat balance of the engine.
18. The volumetric efficiency of a well-designed engine is in the range –
75 to 90%
15. Engine Electronics
19. Hall effect pickup use –
Semiconductors
20. LVDT is used to measure –
Large displacement.
21. The disadvantage of the piezoelectric pressure pickup is that –
It can only give pressure difference.
22. Thermistors are desirable because of –
Large temperature coefficient.
23. Seebeck effect is used in –
Thermocouples.
24. Hot-wire sensors are used for measurement of –
Mass flow rate.
25. Knock sensors use –
Piezoelectric pickup.
26. Catalytic converters use lambda sensors to keep –
Excess air ratio within a range.
27. Strain gauges are mainly used to measure –
Pressure.

16. 28. Electro-optical sensors are used for –
Position and speed measurement.
16. Supercharger & turbocharger
29. Turbocharger engines are those in which charge density is increased by –
Compressors driven by exhaust gas turbine.
30. Supercharger increases the power output of engine by –
Increasing the charge pressure.
31. The centrifugal type supercharger is preferable only for –
Low speed.
32. Advantage of Root’s supercharger is –
Minimum maintenance.
33. Supercharger air compressor is driven by –
Engine itself.
34. Turbocharger compressor is driven by –
Exhaust gas turbine.
35. Cooling after compression is necessary to –
Increase the density of air & reduce engine operating temperature.
36. Volumetric efficiency of supercharger engine is –
Between 100-110%
37. Compared to engine driven supercharger the exhaust driven supercharger is –
Utilizes the exhaust energy of the engine.
38. Types of supercharger are –
Centrifugal, Root’s & vane.
17. Two-Stroke Engines
39. A two-stroke engine is identified by –
Absence of valves.
40. Advantages of two-stroke engine is –
More uniform torque, lighter flywheel & no valves.
41. Charge pressure at the inlet port if a two-stroke engine is –
Higher than atmospheric.
42. The most perfect method of scavenging is –

17. Uniflow scavenging.
43. Two-stroke engine suffer from –
Fuel loss.
44. At the same speed two-stroke engine of the same size as a four-stroke engine will develop.
Twice the power.
45. Two wheelers without deflector type piston use –
Cross scavenging.
46. Crankcase scavenged engine have delivery ratio of –
Equal to 1
47. Short-circuiting in the case of two-stroke engines is equal to –
1 – ηtrap