Ignition and Fuel Systems

ignition-and-fuel-systems

Petrol engines

Air passes through the air filter into the inlet manifold, where it is mixed with fuel, before passing through the inlet valves into the engine cylinders.

On some engines, a carburettor is used to mix the fuel and air. A carburettor uses the flow of air to suck fuel into the engine. It doesn’t give as much control over the fuel/air mixture as a fuel-injected engine.

A fuel injection system is much more efficient than a carburettor, and allows fine control of the fuel/air mixture. On a single-point fuel injection system, a fuel injector is used to spray fuel into the inlet manifold, where it is mixed with air before passing to the cylinders. On a multi-point fuel injection system, one fuel injector is used for each cylinder in the engine.

Diesel engines

The air passes through the air filter into the inlet manifold, and into the engine cylinders. A fuel injection pump pumps fuel to a fuel injector for each cylinder.

On an indirect injection diesel engine, the fuel injector pumps the fuel into a swirl chamber mounted in the cylinder head above the cylinder, which swirls the fuel around to mix it with the air in the cylinder. On a direct injection diesel engine, the fuel injector pumps the fuel directly into the cylinder, where it is mixed with the air.

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