Published: 16 October 2018
Common Rail - The cleaner more powerful modern diesel system
We offer a 24 hour test & report service
Diesel engine technology has advanced by light-years over the last decade or so.
Gone are the days of sulphur laden black, sooty diesel smoke spewing out of the exhausts of semi trucks. The lumbering and cantankerous beasts that filled the roadways and clogged our airways. After the oil shock of the late seventies and early eighties they are now just a memory.
Though diesels have always been very fuel efficient, stringent emissions laws and expectations of performance by the car buying public, has forced developments that have taken the lowly diesel from an embarrassment, to be engineered all the way to clean air and economical powerhouse champions.
So what has changed?
Diesel Common Rail is a fundamental change in diesel technology and it is happening now.
The modern direct-injection engine with common rail is a pre-requisite for new diesel powered passenger vehicles across Europe.
It is the only technology to address all planned European emissions legislation, whilst enhancing reliability, performance and fuel economy. The number of diesel cars we see on our roads is constantly growing. In Europe alone, this growth is predicted to continue at an average rate of 10% per annum, with Common Rail systems growing by more than 35% per year.
Delphi Bosch and Siemens VDO common rail systems can all be serviced in our own workshop.
How does It work?
Diesel from the fuel tank passes up to the filter and onto the high pressure pump. This pump produces fuel pressure in excess of 1600 bar. The pressurised fuel then passes into the fuel rail. From here it flows to the injectors. When the injectors are electronically fired by the vehicle control unit (ECU) fuel in a gas form is injected into the cylinder. The heat caused by the inducted air being compressed ignites the fuel for combustion.
Injection timing and injected amount is calculated by the control unit using sensors on the engine. These include air mass drawn in, engine temperature, air temperature, throttle pedal position and speed, turbo pressure, engine & camshaft position.
The role of the humble fuel filter cannot be under estimated in the modern common rail fuel system.
With the build tolerances being so small in both the high pressure pump and the injectors cleanliness is absolutely vital for long life of the parts and economy.
We recommend using genuine diesel system manufactures filters such as Stanadyne filter manager, Delphi or Bosch. These are constructed to remove all solid contamination before it enters the fuel system.
Costing only fractionally more than a cheap non genuine alternative these will safe guard your system for many thousands of miles.
Common Rail Safety
With the fuel pressure capable of running at >1600 bar and at >70 degrees Celsius safe practices must be followed. Injected fuel can enter the bloodstream . If oil has penetrated the skin, seek medical help immediately. Hospital treatment is imperative and urgent. Never test for leaks with the engine running or without letting the pressure dissipate once keyed off. If live pressure data is not available wait a minimum of 15 minutes before releasing any pipe or connection fittings. Never release a injector or feed pipe nut with the engine running whilst looking to see if an injector is receiving fuel. Never use your finger or any body parts to find a leak.
Common Rail Facts
- Fuel droplets measure only 20 microns diameter.
- Fuel exits the nozzle at up to 1240 mph.
- Injection takes place in 1-2 milliseconds
- That’s 200 injections for a single blink of the eye lid.
- Production allows variations of just 0.2 microns for any moving parts.
- In comparison a human hair is 30 times thicker.
- Latest versions can fire fuel 7 times per firing cycle.
- Fuel pressures now up to 2200bar / 31908psi