True revolutions in the car are rarely noisy. .. A typical example of a quiet revolutionary technology in the strict meaning of the term is the piezoelectric effect, used in the injectors of the third generation diesel engines with direct injection of fuel according to the system Common-Rail.Generally there is nothing new in the piezoelectric effect. It was discovered by the brothers Pierre and Jacques Curie 125years ago. Then the French scientists found out that when mechanical effect ( pressure, tension or torsion) is exerted on some crystals voltage arises in them. Later studies revealed that along with the natural stone minerals quartz and tourmaline some ceramic materials fit for mass engineering, industrial and household use show good piezo electrical properties.

Everyone can give examples in this direction – the gas-fuelled lighters with piezo element are already a cheap disposable good which has long displaced its gasoline counterparts in the collectible niche and the quartz watches considered to be a technological masterpiece at their appearance in the seventies of the last century today are only a reliably functioning everyday objects.

What is new is that in recent times the good old piezo effect is experiencing its next high point of glory in the field of direct fuel injection technology in the diesel engines owing to the giant Bosch. The piezoelectric cristals which are rediscovered by the specialists of the Stuttgart concern are used in the so called “linear injectors” which are produced in the Bosch factory in the German city of Bamberg and are successfully built in first in the engines of the serial Audi A6 2.7 TDI and 3.0 TDI and a little later in the rest representatives of the brand.

The principle of operation of the new technology is quite simple – voltage is fed to the working piezo module consisting of several hundred separate crystals as a result of which it expands increasing its volume. The process is shorter than one ten thousandth of the second and the movement of the piezo module is transmitted directly without any mechanical mediators and losses of friction of the valve controlling the process of injection which is enabled to respond extremely fast and adequately when controlling the processes. Owing to this lightning speed the injection nozzles can let through microscopic amount ( of the order of one cubic millimeter) fuel in the cylinders thus fulfilling the role of “pilot” injection before the main dose. Moreover, owing to the new technology the fuel designated for one stroke can be distributed to up to five partial processes of injection under the pressure of 1600 bar.

All this may sound as a pretty dry theory but it has huge practical advantages. An example in this direction is the increase in the environmental performance – the engine of Audi 3.0 TDI performs without any problems the requirements of the Euro 4 norm even without a particulate filter ( which is offered meanwhile by the Ingolshtad company). According to the specialists from the Audi engine development department the piezo technology has contributed greatly to the decrease of fuel consumption and the level of noise and from Bosch they point out as a major advantage of the new technology its contribution to the increase in the power of diesel engines. Obviously the advantages are really impressive because after Audi brands like Mercedes-Benz, BMW, Vw and Renault soon joined the clients of Bosch and after some years the piezo technology in the spray injectors probably will be applied in the vast majority of diesel engines with direct injection. In that the potential of Bosch accentuates on the increased power but the torque curve also looks convincingly.

The discovery which Pierre and Jacques Curie made 125 years ago in the automotive field seems far from exhausted. In Bosch, for example, they plan to use in the Common-Rail aggregates of the fourth generation not only injection under the pressure of 2000 bar but also nozzles allowing variable geometry of the injected jet. The company experts apparently have a very clear idea of how to manage the nozzle needles to achieve that effect.