Common rail and its benefits

Common rail is a fuel injection system found in modern diesel engines. Common rail systems provide a level of flexibility which can be exploited for class leading emission control, power and fuel consumption. This enables Original Equipment Manufacturers (OEMs) to design for optimum performance and exceptional end-user value across a range of machines and applications.

An increasing number of modern diesel engines employ common rail direct injection (CRDi) fuel systems for the flexibility they provide while meeting the most stringent emission control standards.

In common rail systems, the fuel is supplied to the engine under pressure with electronically controlled precision. This provides a level of flexibility which can be exploited for class leading levels of emission control, power and fuel consumption.

Common rail system

How does CRDi work?

The fuel in an electronically controlled engine is stored at variable pressure in a cylinder or ‘rail’ connected to the engine’s fuel injectors via individual pipes, making it a ‘common rail’ to all the injectors. The pressure is controlled by a fuel pump but it is the fuel injectors, working in parallel with the fuel pump, that control the timing of the fuel injection and the amount of fuel injected. In contrast earlier mechanical systems rely on the fuel pump for pressure, timing and quantity.

A further advantage of the CRDi system is that it injects the fuel directly into the combustion chamber. The indirect injection (IDI) system in older engines injected fuel into a pre-combustion chamber which then fed the main combustion chamber.

What is the advantage of CRDi?

CRDi ensures the fuel injection timing, quantity of fuel and atomisation or fuel spray are controlled electronically using a programmable control module. This allows multiple injections at any pressure at any time (within pre-defined limits), providing a level of flexibility which can be exploited for better power, fuel consumption and emission control. 

How will you notice the benefits of common rail?

Noise, vibration and harshness (NVH) are improved with CRDi as a result of the timing flexibility. Your engine sounds quieter and has a better quality of sound. It also runs smoother. You will see fuel consumption benefits as well because greater injection pressure produces a finer spray of fuel (atomisation) that burns more efficiently.

Better combustion efficiency is a key part of meeting emission standards. Less fuel is wasted as soot or particulates in the exhaust and deposits in the engine. A cleaner running engine is good for the environment – and for the cost of ownership. Cleaner running improves the long-term durability and reliability of your engine.

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