Knocking in S.I. Engine

·         In a spark ignition engine combustion which is initiated between the spark plug electrodes spreads across the combustible mixture.

Answer: True

·         A definite flame front is one which separates the fresh mixture from the products of combustion travels from the spark plug to the other end of the combustion chamber.

Answer: True

·         The process of autoignition has nothing to do towards engine knock.

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

·         In SI engine, ignition lag is reduced if the initial temperature and pressure are

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

·         Auto ignition refers to initiation of combustion without the necessity of a flame.

Answer: True

·         The effects of knocking are

Answer: 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.

·         Increase of pressure increases the self ignition temperature and the induction period.

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

·         Low engine speeds will give low turbulence and low flame velocities and knock may occur at low speed.

Answer: True

·         Use of low octane fuel can eliminate detonation.

Answer: False