250+ TOP MCQs on Knocking in S.I. Engine and Answers

IC Engines Multiple Choice Questions on “Knocking In S.I. Engine”.

1. In a spark ignition engine combustion which is initiated between the spark plug electrodes spreads across the combustible mixture.
a) True
b) False

Answer: a

2. A definite flame front is one that separates the fresh mixture from the products of combustion travels from the spark plug to the other end of the combustion chamber.
a) True
b) False

Answer: a

3. The process of autoignition has nothing to do towards engine knock.
a) True
b) False

Answer: b
Clarification: Actually, the process of autoignition leads towards engine knock.

4. In SI engine, ignition lag is reduced if the initial temperature and pressure are _____________
a) decreased
b) increased
c) constant
d) none of the mentioned

Answer: a
Clarification: In SI engine, due to the increment of the initial temperature and pressure are ignition lag is reduced.

5. Auto ignition refers to the initiation of combustion without the necessity of a flame.
a) True
b) False

Answer: a

6. What are the effects of knocking?
a) noise and roughness
b) mechanical damage
c) carbon deposits
d) all of the mentioned

Answer: a
Clarification: The effects of knocking are
i) noise and roughness
ii) mechanical damage
iii) carbon deposits
iv) increase in heat transfer
v) decrease in power output and efficiency
vi) preignition.

7. What are the effects of knocking?
a) increase in heat transfer
b) decrease in power output and efficiency
c) preignition
d) all of the mentioned

Answer: a
Clarification: The effects of knocking are

1. noise and roughness
2. mechanical damage
3. carbon deposits
4. increase in heat transfer
5. decrease in power output and efficiency
6. preignition.

8. Increase of pressure increases the self ignition temperature and the induction period.
a) True
b) False

Answer: b
Clarification: In fact, increase of pressure decreases the self ignition temperature and the induction period.

9. Low engine speeds will give low turbulence and low flame velocities and knock may occur at low speed.
a) True
b) False

Answer: a

10. Use of low octane fuel can eliminate detonation.
a) True
b) False

Answer: b
Clarification: No, but the use of high octane fuel can eliminate detonation.