Multiple Choice Questions and Answers (MCQs) on Internal Combustion (IC) Engine

01. 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

02. The operation of forcing additional air under pressure into the engine cylinder is known as

(A) Supercharging
(B) Carburetion
(C) Turbulence
(D) Delay period

03. 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

04. 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

05. 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

06. 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

07. 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

08. 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

09. 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 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 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