Question

In alcoholic fuels the knock is reduced at _____________ mixtures.

(a) rich

(b) lean

(c) equal

(d) none of the mentioned

I got this question during an interview.

My question is taken from Effects of Supercharging in section Supercharging of IC Engine

Answer 1

Answer: (b) lean

Explanation: In alcoholic fuels, such as ethanol, the knock is reduced at lean mixtures. Alcohol-based fuels generally have higher resistance to knocking compared to gasoline, and operating with a lean mixture (less fuel, more air) further reduces the chances of knocking. Lean mixtures lower combustion temperatures, which helps in preventing the premature ignition (knock) of the fuel-air mixture.