Common Rail Diesels

I first heard about Common Rail Diesels in the marketing of the Jeep Grand Cherokee! I couldn’t understand why this would be such a major marketing item. I’ll cover that off at the end of the article.

Direct injection was developed for military use on aircraft by the Germans and Soviets and then jumped to civilian use after World War 2. Robert Bosch developed an automotive version in the 1950s and it was fitted to Mercedes models. This allowed a precise amount of fuel to be used for linear performance and to remove the issues of unbalanced carburettors.

The Common Rail Diesel, an extension of direct injection, was first developed in the 1960s by the Swiss and then further development was done by Magneti Marelli, FIAT and other collaborators. They were looking for a way to take the concept and mass produce it. Ultimately their work was bought by Bosch who put it into production.

The Common Rail bit of the diesel engine can also be used on a petrol engine – it is basically a common rail (pipe) that delivers fuel to the cylinders. Whereas a fuel injected car has a mechanical injection system that meters the fuel according to power required and there is a spark plug – or compression in the case of the diesel motor – to cause detonation, the Common Rail delivers the fuel at very high pressure electronically with the ECU controlling the flow.

Most diesel motors in cars now use the Common Rail system developed by Bosch, Denso or Siemens and run at 15 – 20,000 psi and push the fuel to the electronic injectors. A high pressure pump loads up the rail ready for the injectors to deliver to the cylinders. The idea is to increase power and fuel efficiency because the system regulates the fuel according to the ECU’s management.

Have a look at this video produced by Engineered Diesel:

Back to the Jeep Grand Cherokee advertisements, the marketing message should have concentrated on the fuel economy and power produced by the engine, however Jeep were clearly hoping that buyers would think that their Common Rail Diesels were new and exciting! Now you know that most diesel cars on the road use this technology.