Please see our warning when working on common rail diesels or looking for leaks. Diesel is now more powerful, responsive and environmentally friendly than ever. Thanks largely to the development of the diesel 'common rail' system, the days of noisy, unresponsive tractor style engines are long gone. Instead of only being fitted to trucks, tractors and 4WD, diesel engines now find applications in small city vehicles such as the Volkswagen Golf, Ford Focus and Holden Astra through to high end luxury vehicles such as the Mercedes Benz E class, BMW X5, and Volvo XC70. In addition, common rail diesel is the preferred choice for commercial vehicles such as the Mercedes Benz Sprinter and Vito, Iveco Daily and others because of the low down torque and improved fuel economy. So what is common rail, how does it work, what are the advantages, what types of Australian vehicle's is it fitted to and what does it mean for you? This website will endeavour to answer these questions in a basic and easy to understand way. It is by no means a detailed analysis of this complicated diesel injection system.
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| What is Common Rail
As it's name suggests there is a common rail that acts as an accumulator to feed fuel to all of the injectors. Filtered fuel is supplied to the rail by means of a high pressure pump.
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1 = High Pressure Pump 2 = High Pressure Rail 3 = Electronic Control Unit 4 = Injector |
 Unlike various other diesel fuel injection systems where
the injector only receives fuel pressure once the injection pump has metered
an amount of fuel for that cylinder, the common rail system stores a constant
amount of high pressure fuel at the rail and right up to the injectors.
The main advantage of this system is to vary injection pressure and timing over a broad scale leading to many benefits in engine design, improved driveability and greatly reducing it's environmental impact. Therefore the heart of the common rail system is the injectors and electronic software and hardware. |
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| How does Common Rail work?
Filtered diesel fuel is delivered in a low pressure condition (between 6-7 bar or 85-100psi) from the diesel fuel tank to the high pressure pump. This can be done by either an electric fuel pump, gear pump or both. The high pressure pump uses mechanical plungers to increase this fuel pressure to pressures up to and including 2000 bar (over 29,000psi) and delivers this to the common rail.
This pressure is regulated and monitored by the electronic diesel control by means of a rail pressure sensor. Due to the safety concerns of a diesel leak at 2000 bar, there is also the facility for a pressure-relief valve or pressure maintaining valve. A common rail injector comes in 2 basic types: the solenoid-valve injector and the piezo-inline injector. |
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| You have probably used Piezo crystals before on your BBQ or gas stove
without even realising. When the button is pressed on your BBQ lighter the
movement of the Piezo crystals create a high voltage spark. The reverse is
the case when these crystals are installed in a common rail injector. A voltage
is sent to the injector, which creates movement in the Piezo crystals and
allows the delivery of fuel.
The Piezo injector allows the implementation of very short and rapid fuel delivery characteristics. By avoiding mechanical forces acting on the needle, such as a pushrod, it allows consistent and accurate delivery of diesel with up to 7 injection cycles per engine combustion cycle. All of these components are interconnected by means of the Electronic Diesel Control Unit. It gathers a seemingly endless source of information by means of input sensors such as:
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Calculating all these inputs against the manufactures mapping it can
control actuators such as:
All of these capabilities allows the common rail diesel injection system to be one of the fastest growing segments in Australian vehicles, and the choice of most manufactures.
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WHAT ARE THE ADVANTAGES COMMON RAIL?
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WHAT TYPE OF AUSTRALIAN VEHICLE"S IS DIESEL COMMON RAIL FITTED
TO? Ford Focus 2.0 litre 100kw/4000rpm 320Nm/2000rpm
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| WHAT DOES IT MEAN FOR YOU?
When it comes to purchasing your next vehicle - drive the diesel! You will be very surprised at the driveability, responsiveness and most importantly the economy. Of course with such complex technology on board your vehicle, you need to know that these systems can be repaired economically. There is no doubt that these systems are well beyond being repaired in your next door neighbours back shed (please see our warning on common rail diesel systems) however there is a specialists common rail repairer conveniently located in Brisbane, Queensland. Highway Diesel Service is located at 26 Annie Street Coopers Plains Qld 4108 and their phone number is +61 7 3277 5244 and the fax number is +61 7 3875 1398 or you can contact them via email Highway Diesel Service is a diesel fuel injection specialist repairer. Authorised repairer for Bosch, Denso, Delphi, Stanadyne, Zexel they can diagnose and repair your diesel injection system and keep you on the road and your vehicle's injection system running at it's optimum. Check them out at www.highwaydiesel.com.au |
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| SAFETY
Common rail injection systems operate at voltages of well over 100 volts and fuel pressures of up to 30,000psi! Experience and training are necessary for the safety of all who work on vehicles equipped with common rail. Please do not 'feel' for leaks with your hands around the engine or loosen high pressure injection lines as this has the potential for injury or even death. If you have a difficulty with your common rail diesel or are a mechanic about to work on a vehicle, and are unsure of which procedure to follow please contact the professionals for their friendly advice:
Highway Diesel Service Phone: 07 3277 5244
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