It seems as though when customers are at the shop, the question always arises as to what common-rail really means. Then after I explain the technology to them, the reply that I get is, “Why did they have to change everything and start using computers?”

If you find yourself in a similar boat and have to explain a process to your customers that they’re already using, I think I can help. In simple terms, the common-rail system consists of four major components: the high-pressure fuel pump, high-pressure fuel rail, individual injectors, and an electronic control unit (ECU). The high-pressure fuel pump is gear driven by the engine. As the engine spins, fuel enters the pump and is pressurized (at idle, fuel pressure is around 5,000 psi; at wide open throttle, fuel pressures can reach as high as 28,000 psi). Fuel is then delivered to the high-pressure fuel rails. The fuel rails are basically storage devices with hard, thick steel lines delivering fuel to the injectors. The injectors have solenoids actuated by the electronic control unit that allow fuel to be delivered to the cylinders.

Keep in mind that other sensors and actuators are controlled by the same electronic control unit that maintains and regulates fuel pressures as the demands of the engine change. Any changes to the fuel system from different demands of the engine are calibrated by the ECU in milliseconds, so if there is an increase in the demand for power, the results are felt almost instantly. Especially since all diesels are now turbocharged, boost has an incredible impact on power and efficiency.

But the question of “Why all the computers?” still remains. Owners seem to feel that the automakers are a part of some sort of conspiracy, probably due to the price of repairs. So the common-rail subject led me to dig a little deeper. Not necessarily about why it came about but WHEN the concept came about.

The introduction of the Chevrolet Duramax engine seems to be when the public started hearing more about common-rail injection. One thing you have to remember, the reason that there have been so many technological changes to gas and diesel engines is because of emissions laws. Automakers were forced to come up with a solution to decrease the  hydrocarbons and nitrogen oxides from the tailpipe. So even though we may frown on emissions devices that are placed on the engine, they have made things better overall.

With common-rail injection, being able to inject diesel into the combustion chamber at that kind of pressure and at the right time resulted in a more efficient burn. And with the ECU being in control, pilot injection was possible, which made the diesel quieter. With  pilot injection, as the piston travels up the bore and compresses the air, a small amount of fuel is injected into the cylinder to start the burn process. This way, when the piston reaches the top of the bore and injection takes place, there isn’t such a harsh clack or rattle when the fuel is ignited.

If you remember, diesel injection used to be very crude, harsh and inefficient. Most diesel injection systems back in the day incorporated a fuel pump that delivered fuel to an injection pump. As the injection pump was driven by the engine, fuel was drawn into the delivery chamber of the injection pump where it was compressed and sent through a hard steel line to the injector. The injector used the pressurized fuel to lift the injector needle off the seat and squeeze the fuel through the nozzle into the cylinder. This crude method of delivering fuel often made the engines run lean and inefficient, not to mention loud. However, they were reliable, and gave trouble-free service for many years.

During my research on the subject, one amazing thing I discovered was that the concept has been in existence for more than 50 years! The idea was apparently developed by a gentleman named Robert Huber of Switzerland in the 1960s. I couldn’t find out much about Huber other than a mention, so I do not know what the prototype was. In the 1970s, Dr. Marco Ganser, also of Switzerland, further developed Huber’s idea of common-rail. Ganser was, at the time, a project engineer with Stanadyne Diesel.

Stanadyne Corporation has built diesel injection pumps for many diesel engine manufacturers for years. In 1985, Dr. Ganser started his own company – Ganser-Hydromag – for the purpose of developing his common-rail system. At that time,  no one believed he could succeed with this idea. Despite opposition, Ganser continued to further develop the common-rail system and worked with automakers such as Volkswagen, Daimler, Mercedes, General Motors, Isuzu and Yamaha.

In the 1990s, more common-rail systems were being developed using an electronic control unit. The major automaker developing this concept at the time was Fiat, working in conjunction with Magneti-Marelli. Then Fiat got into financial trouble and decided to sell the idea to Bosch, which developed the idea and placed its first common-rail system in a production car in the Alfa-Romeo 156 in 1997.

However, the story really goes much further back and begins much earlier than Huber’s concept in the ’60s.  Doing some more research, I found that there was a mechanically operated common-rail system in existence 90 years ago. This type of common-rail was developed for use in submarine engines by a team of engineers at the Vickers shipyard in northwest England.

Steam engines at that time were very inefficient and unreliable and the team of engineers at Vickers powered diesel engines in their submarines using the mechanical common-rail system. This type of common-rail, with one or more pumps discharging high pressure fuel into a delivery line to the injectors, serves as the basic principle we use today. Cummins recognized this system’s advantages and employed a similar type of injection on its L10 engines.

Despite wishful thinking on the part of some consumers, the common-rail system does not employ electronics merely to feed some conspiracy theory, but instead to make things better and more efficient. The concept of evolution in this business has been around for years and has been refined for today’s demands. Think about Rudolph Diesel’s first attempt and where it has evolved today. The process is what drives great thinkers of today. It’s not about trying to reinvent the wheel, but only to make it better.

Robert McDonald is owner of Atlantic Engines in
Granite Falls, NC, and specializes in high performance diesel and
gasoline engines and cylinder heads for street, marine, dirt and drag
racing. You can reach Robert at [email protected].