TDI Engines.

To achieve maximum precision in controlling the injection process and thus substantially reduce fuel consumption and emissions, Volkswagen uses piezo inline injectors instead of solenoid valves. For instance, in the 2.0 TDI® PD producing 125 kW and in the 3.0 V6 TDI® the injectors are actuated by means of piezo crystals. The injectors contain several piezo crystals connected in series (inline), in order to achieve the required needle or valve lift. Piezo crystals have the property that the structure of their crystal lattice changes when an electric current is applied to them, causing the crystal to expand or contract.

Piezo elements are significantly lighter and respond twice as fast as conventional solenoid valves. This enables the injector valve to switch five times more quickly and therefore meter the fuel and control the injection curve far more precisely. This represents an important factor in achieving efficient and smooth combustion with low emissions. To express its capabilities compared with previous systems in figures, diesel injection with piezo injectors offers the potential, depending on the design concept, to reduce fuel consumption by roughly three percent, to lower pollutant emissions by up to 20 percent, to increase the achievable engine power by up to five percent and to approximately halve engine noise with a reduction of up to three decibels (A).