A common rail is one of the most important components in a diesel and gasoline direct injection system. The main difference between a direct and a standard injection is the delivery of fuel and the way how this one mixes with incoming air. In the direct injection system, the fuel is directly injected into the combustion chamber, skipping the waiting period in the air intake manifold. Controlled by the electronic unit, the fuel is squirted directly where the combustion chamber is hottest, which makes it burn more evenly and thoroughly.
The main advantages of the common rail direct fuel injection can be summarized in reduction of exhaust and noise emissions, better fuel efficiency and improved overall engine performance. The system consists of a high-pressure pump, injectors, a rail, and an electronic control unit.