Common rail technology differs in that fuel is delivered to all cylinders through a fuel rail that is pressurized by one single pump,
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| Common-rail technology is hardly a revolutionary concept, introduced to the Dodge Ram 2500/3500 Cummins pickup in model year 2003 and updated again for the 2004.5 model year. (Photo: DaimlerChrysler Canada) |
with highly precise computer-controlled injectors. Common rail engines are capable of producing multi-phase injections (capable of injecting before and after combustion) for even greater efficiency, performance, refinement and drastically reduced emissions. In case you weren't aware, two common-rail diesel engines currently sold in North America are found in the Jeep Liberty CRD, introduced for the 2005 model year, and the Dodge Ram 2500/3500 Cummins pickup which debuted in model year 2003 and updated again as a 2004.5 model... i.e. this is not a revolutionary concept.
Another factor involved in cutting emissions, particulate filters, can be fitted to common-rail diesel-powered vehicles, but they cannot be fitted to unit-injection diesel vehicles. The reason, unsurprisingly, has to do with common-rail technology and its ability to inject fuel during the post-combustion phase. The small secondary burst of fuel allows the temperature of exhaust fumes to rise, allowing for the filtration of emissions-causing particles. Particle filters are able to remove up to 80 percent of particulate emissions and would certainly help VW sneak by lofty tailpipe regulations.
While
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| While VW has stuck it out with PD-injection, Audi, by comparison, offers common rail technology on its Euro luxury models. (Photo: Audi Canada) |
VW has stuck it out with PD-injection, Audi, by comparison, offers common rail technology on its luxury models. You may have heard the term 'piezo injector' mentioned in reference to diesel-powered A6 and A8 models. Piezo, Greek for "squeeze" are amongst the newest generation diesel injectors available, and capable of delivering fuel even more precisely and at higher pressure than the direct injectors previously used by VW's TDI engines. And when combined with particle filters, vehicles equipped produce carbon dioxide ratings that are significantly lower than those of regular gasoline engines. Combine this with the improved off-the-line performance of torquey diesel engines, reduced fuel consumption and refinement that's on par with regular gasoline engines, and there is no wonder why diesels are so popular in places where fuel quality is clean enough to make use of them.
