Fuel Systems: Intake & Exhaust: Intake & exhaust systems

       

Carbureted systems

Summary
Air enters through the air cleaner and passes through the carburetor to be mixed with the correct amount of fuel. Air-fuel mixture then passes through the inlet manifold, and enters the cylinders.

On a carbureted engine, the intake system is part of the fuel system.
The main function of the intake system on a gasoline engine is the delivery of the required amount of the mixture of air and fuel.
In a basic system, air enters the air cleaner for filtering, then passes into the carburettor, where it mixes with the required amount of fuel. This air-fuel mixture then enters the intake manifold, and finally the cylinder.
The same basic principle applies on the rotary engine.
On all carbureted systems, the intake system can be crucial in increasing engine output. This can be done by increasing volumetric efficiency, that is, by increasing the amount of air-fuel mixture burned in the cylinders.
This can be achieved by using a larger inlet valve to admit more charge into the combustion chamber; by using large, free-flowing intake manifolds; or by using extra carburetors.
Carbureted intake systems were once standard for gasoline engines, but increasingly they are being displaced by electronic fuel injected systems.