Controlled recirculation

Electric motor driven exhaust flap (PresseBox) (Neckarsulm, ) Since 1982, exhaust gas recirculation has been one of the most wellestablished methods for internal engine emission control in diesel engines to essentially control the formation of soot particles and the discharge of nitric oxides. After the combustion, the exhaust gas is extracted and mixed with fresh air in order to regulate the combustion gas temperature. Besides the well-known high pressure exhaust gas recirculation, the introduction of Euro 6 will lead to an increased usage of so-called low-pressure exhaust gas recirculation. As its name suggests, it requires auxiliary means, such as for example exhaust flaps, to build up the necessary back pressure due to its low-pressure configuration. Pierburg GmbH refined its electromotor driven exhaust flap especially for this application - the newest model is significantly lighter and more compact.

In low-pressure exhaust gas recirculation, the exhaust is extracted from the exhaust stream after passing the turbine behind the diesel particle filter and mixed with fresh air before the compressor. The advantage is that the turbine does not lose any hot, energy-rich exhaust gas for powering the compressor.

This positively affects fuel consumption. On the other hand, this method only recirculates exhaust which has already been cleaned by the diesel particle filter. The result is that less dirt and soot particles end up in the recirculation system and total particle emission levels are decreased. The unfavourable low-differential pressure between the diesel particle filter and the compressor can be compensated with the usage of the electric motor driven exhaust flap from Pierburg. The necessary back pressure can be generated with its help and high mass exhaust flow rates can be achieved.

The electromotor driven flap is continuously adjustable from the "open" to the "closed" position. It enables a defined pressure build-up in the entire adjustment range and consequently promotes controlled exhaust gas recirculation and emission reduction. The flap position feedback signal is transmitted by a contactless angle sensor. If the drive loses electric current, the flap is automatically spring-loaded back into the "open" default position. Offering the same functional range, the modular design of the main elements just vary in the flange layout, mounting geometry and flap diameter. The electromotor driven exhaust flap can thus be adapted for various vehicle types and exhaust systems, depending on the necessary size of the individual installation space available.

High-quality materials pay off

Pierburg developed the first electromotor driven exhaust flap featuring a precision-casted housing for the NAFTA market in 2007. Today a more advanced exhaust flap is also available in a lighter sheet-metal design, which thereby contributes additional fuel savings. The use of high-grade materials has paid off from the start. On the one hand, the high corrosion resistance enables the flap to be applied directly in the exhaust system, which, as everyone knows, is located in the vehicle underbody, where it is especially exposed to dirt from the outside; additional stress arises from continual exposure to corrosive exhaust products from the inside. On the other hand, the highly temperature-resistant material ensures proper functioning of the electric flap, even at high temperatures up to 750°C.


Rheinmetall Automotive AG
Karl-Schmidt-Straße 1
D-74172 Neckarsulm
Anne-Kristin Noack


Social Media