Question

In a petrol engine, the mixture has the lowest pressure at the __________

(a) beginning of suction stroke

(b) end of suction stroke

(c) end of compression stroke

(d) none of the mentioned

The question was asked in semester exam.

This intriguing question originated from Comparison of Two Stroke S.I. and C.I. Engines topic in portion Two Stroke Engines of IC Engine

Answer 1

The correct answer is:

(a) beginning of suction stroke

In a petrol engine, the mixture of air and fuel has the lowest pressure at the **beginning of the suction stroke**. This is because, at this point, the intake valve opens, and the piston moves downwards, creating a vacuum that causes the air-fuel mixture to be drawn into the cylinder. The pressure is lowest here before the intake process begins to fill the cylinder.