Question

The knock limit is dependent upon ___________

(a) the type of fuel used

(b) mixture ratio

(c) spark advance

(d) all of the mentioned

The question was asked in an interview.

The doubt is from Effects of Supercharging in division Supercharging of IC Engine

Answer 1

Answer: (d) all of the mentioned

Explanation: The knock limit is dependent on:

• The type of fuel used: Different fuels have varying resistance to knocking. Fuels with a higher octane number are less prone to knocking.
• Mixture ratio: A leaner mixture (more air, less fuel) tends to reduce knocking, while a richer mixture (more fuel) can increase knocking.
• Spark advance: Advancing the spark (ignition timing) can increase the likelihood of knocking, as it causes the air-fuel mixture to ignite earlier in the compression stroke, potentially before the piston reaches its optimal position.

All these factors collectively influence the knock limit in an engine.