Common rail system (CRS)

The common rail system (CRS) is an electronically controlled, direct fuel injection system used to satisfy emission regulations.

By promoting complete combustion, it reduces amounts of carbon monoxide (CO), hydrocarbons (HC), and particulate matter that would otherwise be generated due to incomplete fuel combustion.

Common rail systems have the four following characteristics:

  1. Common rail systems inject fuel at a higher pressure than mechanical fuel systems.
  2. The length of time at which fuel is injected is controlled by the engine control unit (ECU).
  3. Common rail systems can perform fuel injection multiple times during each combustion cycle.
  4. Fuel injection quantity are controlled by the ECU.
    These four characteristics enable common rail systems to aid in reducing exhaust gas emissions.

The term "common rail" is also used as a common name to describe diesel engines equipped with electronically controlled fuel injection systems. This usage is unique to electronically controlled diesel engines due to the fact that mechanically controlled diesel engines do not have a part called a "rail."
Common rail systems are comprised of three main components: a supply pump, rail, and injectors.

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