Quote:
Originally Posted by Piwoslaw
Older diesels had a pump for each injector, while in commonrail technology there is one pump responsible for creating very high fuel pressure in a reservoir used by all four injectors. This, along with direct injection, gives a much better air-fuel mixture, which increases engine efficiency, power by around 25% and low end torque by 50%, reduces fuel consumption by around 20%, and reduces emissions.
|
All diesels, even the old ones, are direct injection.
Although a better fuel/air mix does help with common-rail injection systems, the main advantage comes from ability to fine tune the injection event. Old diesels just injected a slug of diesel into the cylinder at the appropriate time (giving that traditional diesel bang). With high pressure common-rail systems the injection period can be spread out over time - slowly at the beginning of the stroke and then pouring it on during the peak power stroke and then tapering off at the end. This wrings every bit of available power out of the stroke, resulting in more power, more torque, more efficiency, and most notably - less noise.