Common Rail Direct Injection

  The common rail is a fuel rail where fuel pressure can build much higher than the pressure that was used in previous engines and the fuel is sent directly to the cylinders through the use of electrical injectors which are situatied directly above each cylinder.
  Common rails are used to improve the operation of both the gasoline and diesel engines. They are used in direct injection gasoline engines and have provided several improvements over previous types of fuel injected engines.
  The bulk of this webpage will discuss the benefits of the common rail to diesel engines, although gasoline engines have improved via the common rail they were always great at performance, refinement, quiet operation and low emissions but the diesel engine's only benefits were fuel efficiency and more torque giving it the ability to carry heavier loads over longer distances much easier.
  The common rail diesel is an engine that performs better, is quiter, has less emissions and more fuel efficient than the regular mechanical injection diesel engines. Common rail direct injection has changed the way diesel engines were percieved and they are now worthy to be placed in some of the most highly regarded luxury vehicles in the world.
  A traditional diesel engine has a fuel pump that builds up the pressure of the fuel and that fuel is sent to mechanical injectors with the pressure of the fuel pump being used to open the injectors and the fuel being under pressure would literally spray into the cylinder.
audi common rail
Image from
  The fuel pump is still used to build pressure and the fuel is stored in the common rail. An electrical system is used to send the fuel to piezo injectors and the spraying of the fuel is done in high precision. As the injectors are controlled electronically a spray pattern for a more powerful explosion can be achieved. There is no unburnt fuel or very little if any and the fuel is injected at exactly the right time for all to be used. This image is the V6 3-litre diesel engine used in several Audi models.
  While these engines are still not as quiet, refined or any other the benefits of the gasoline engines their vast improvements have now found themselves in luxury and sport, and performance oriented vehicles. If fuel cost is your preference you can have a vehicle with a common rail diesel that almost as good but much more fuel efficient than even the common rail gasoline engines.
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