Question

For volatile petroleum fuels of high octane number, the knocking is reduced at _____________ mixture.

(a) very rich

(b) very lean

(c) equal

(d) none of the mentioned

The question was posed to me in a national level competition.

My question is based upon Effects of Supercharging topic in portion Supercharging of IC Engine

Answer 1

Answer: (b) very lean

Explanation: For volatile petroleum fuels with a high octane number, knocking is reduced at a very lean mixture. A lean mixture, with less fuel and more air, tends to lower the likelihood of knocking because it reduces the combustion temperature and pressure. Knocking is more likely to occur in rich mixtures (excess fuel), which cause higher combustion temperatures. Therefore, operating with a leaner mixture helps to mitigate knocking, particularly with high-octane fuels.