At what point is petrol mixed with air before being drawn into the engine?

The mixing of petrol with air occurs in the Venturi, which is a crucial component of carburetors or fuel injection systems. The Venturi effect utilizes the principles of fluid dynamics where air flows through a tube that narrows in the middle. As the air passes through this constricted section, its velocity increases and, due to the Bernoulli principle, the pressure decreases. This drop in pressure allows fuel from the petrol supply to be drawn into the airflow, creating a fine mist of fuel that mixes with air. This mixture is then directed into the engine's intake manifold and ultimately reaches the combustion chamber.

Understanding this process is essential for grasping how internal combustion engines operate efficiently. Other locations mentioned in the options serve different functions: the combustion chamber is where the air-fuel mixture ignites, the air intake is where air enters the engine system, and the fuel pump is responsible for delivering fuel to the engine but does not mix it with air. Therefore, the Venturi is where the decisive mixing of petrol and air takes place prior to being drawn into the engine for combustion.