Question

For volatile petroleum fuels of high octane number, pre-ignition is reduced at _____________ mixture.

(a) very rich

(b) very lean

(c) equal

(d) none of the mentioned

I got this question during an internship interview.

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

Answer 1

Answer: (b) very lean

Explanation: For volatile petroleum fuels with a high octane number, pre-ignition is reduced at a very lean mixture. Pre-ignition occurs when the air-fuel mixture ignites prematurely due to excessive heat or pressure in the combustion chamber. A lean mixture, which has less fuel and more air, tends to burn at lower temperatures, thereby reducing the chances of pre-ignition. On the other hand, a rich mixture (excess fuel) can increase the likelihood of pre-ignition due to higher combustion temperatures.