The common-rail system takes its name from the shared high-pressure line (the ‘common rail’) that supplies all cylinders with fuel and serves as a pressure accumulator.
Unlike other injection systems, in common-rail systems pressure generation and injection are separate from each other. A separate high-pressure pump continuously feeds the fuel into the rail, allowing the system to have fuel available at the right pressure at all times, even at low engine speeds. Other diesel direct-injection systems have to build up the high fuel pressure anew for each injection process.
The primary pump supplies fuel to a high-pressure reservoir (the fuel rail), where the fuel is stored at the optimal pressure for the engine’s instantaneous operating conditions in preparation for subsequent injection. Each of the engine’s cylinders are equipped with an injector featuring an integral solenoid valve. This solenoid valve opens and closes to define the starting point and mass of the injection process. The driver’s demand is defined by the accelerator pedal. An engine control unit (ECU) registers driver demand and current vehicle operating conditions as the basis for calculating the required fuel pressure and injection timing according to the parameters defined in the program map.
Common-rail technology differs from conventional systems by providing multiple injections per working cycle. The cycle is divided into pre or pilot injection for reduced engine noise, main injection for optimal power deployment and secondary injection for reduced emissions. The fuel reaches the injection nozzles via short pressure lines.
The first generation of the common-rail system permitted an injection pressure of 1300 bar. At present, the second generation of the system generates 1600 bar. The third generation introduced in 2003 achieves pressures of up to 2000 bar at the nozzle. For injection, newly-developed piezo injectors are used instead of conventional solenoid valves. Piezo injectors operate up to five times faster, allowing an even greater degree of freedom in designing the rate-of-discharge curve with both pilot and post-injections.
MTQ Engine Systems Australia is a common-rail specialist with the capabilities to repair or remanufacture all components of the various common-rail fuel systems available today.
Due to the advanced technological nature of the common-rail system, repairs of the components require advanced equipment and highly trained technicians to ensure that the system is working harmoniously. MTQ’s branches are equipped with the latest technology and factory-trained technicians to ensure you get vehicles back on the road with minimal downtime. MTQ is also a Bosch common-rail repair partner, meeting the strict criteria for equipment, tooling and facility capabilities.
Along with common-rail repairs, MTQ offers a ‘Reman’ exchange program where you bring in your worn or damaged unit and replace it from an expansive range of remanufactured units, saving you time and money. All of MTQ’s remanufactured units come with a 12 month, unlimited kilometer/hours warranty to give you piece of mind.
For more information visit: www.mtqes.com.au