TDI Engines.

In the common rail system, the components for pressure generation and fuel injection are separate from one another. An independent pump maintains a constant fuel pressure at all times. This pressure is stored in a single distribution rail, the common rail, which is so called because it is shared by all the cylinder heads. The injectors which feed the fuel to the engine’s cylinders are connected to the common rail by short feed lines in a parallel arrangement.

The ever higher injection pressures being generated for boosting the efficiency of diesel engines and lowering their emission levels place acute demands on the common rail system. For this reason, Volkswagen manufactures the rail itself, the first automotive manufacturer to do so. Our latest generation of diesel engines attain injection pressures as high as 1,800 bar. The resulting operating requirements mean that surface finish, fatigue strength, seal tightness and cleanliness must all be of an exceptionally high standard. Consequently, every component must first come through ten million load cycles at alternating pressure without developing a single flaw.

In the new Golf, common rail technology makes a significant contribution to reducing noise levels too: while the injection pressure of up to 1,800 bar and specially designed eight-hole injector nozzles guarantee extremely fine atomisation of the diesel fuel, latest-generation piezoelectric inline injectors are responsible for controlling the nozzles. The piezoelectric technology enables more flexible fuel injections with smaller quantities of fuel that can be metered more precisely. The advantages of this are very quiet and pleasurably smooth engine running, remarkably spontaneous response, as well as particularly low fuel consumption and emissions figures.