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Common Rail INjection Systems

How Common Rail Diesels Work



How a Common Rail Works

High pressure common rail injection is a technique for delivering pressurized fuel to the injectors. The low pressure fuel pump (lift pump) delivers fuel to the injection pump (high pressure pump). The injection pump pressures fuel up to 30,000 psi in a common rail, a tube (I-6 engines) or tubes (V-8 engines) that are connected to each of the fuel injectors. The name "common rail" is derived from the fact that all fuel injectors receive fuel from the same fuel rail (in V-8 engines, each bank shares a fuel rail), as opposed to individual lines for each injector.

Benefits of Common Rail Injection

Since pressurized fuel is stored in the common rail, injection pressures are less dependent on engine speed, unlike mechanical injection systems. Today's high pressure common rail systems also utilize Piezo injectors, which allow for multiple injection events per cycle. All of this translates into higher performance potentials, increased low-end performance, improved fuel economy, reduced engine noise, and significantly lower emissions.

Which Engines use Common Rails

Cummins switched to a high pressure common rail in 2003 for the 5.9L 24v Cummins. All 6.7L Cummins also use common rails. All generations of 6.6L Duramax diesels use Bosch high pressure common rail systems. Ford ditched the HEUI injector in 2007, and started using common rails on the 6.4L Power Stroke for 2008. The 6.7L Power Stroke also uses a high pressure common rail.


Common rail injection system