Composition of common rail system
The common rail system refers to a closed-loop fuel supply system composed of a fuel tank, a gear pump, an oil-water separator, a gear pump, a diesel fine filter, a high-pressure pump, a common rail pipe, an injector, and sensors and an ECU. It completely separates the generation of injection pressure and the injection process.
Common rail operation
The diesel in the fuel tank is sucked in by the pump, which delivers it to another high-pressure pump. The second pump delivers diesel to the distribution pipe, which is the source of each injector for each cylinder. Diesel is injected into the cylinder at a pressure of 300 to 1600 bar (Toyota engines inject up to 2000 bar, compared to gasoline engines that inject no more than 5 bar). Due to the smaller nozzle, more powdered diesel enters the cylinder (as well as very fine mist), which contributes to spontaneous combustion.
The injection pressure and the possibility of pre injection before the main injection are controlled by the onboard computer to optimize power, consumption, and engine noise based on the engine load and power requirements.
The result of pre injecting diesel before the main diesel in the cylinder is to control the noise level and improve the performance of the engine. Fiat is the company that makes the system more advanced, with its technology called MultiJet, which can send up to 5 previous diesel injections to the cylinder before the main injection, improving control of the mixture and increasing pressure and temperature inside the cylinder.
