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Technical Paper

New Developments in Catalytic Converter Technology as Demonstrated by Mercedes-Benz 300 SL and 300 CE

The new Mercedes-Benz sportscars typify European catalytic converter design trends. Maximum frontal-area for minimum back-pressure and maximum power of the 4-valve engine was the target for the new 300 SL. This was achieved by moving away from conventional design and using a shape of substrate and housing equidistant to the contour of the transmission-tunnel. Great efforts had to be done to give necessary mechanical strength to the system, but as a result there is a big improvement in engine power and catalytic longterm stability. New canning technology, based upon mat, has been utilised for the 300 CE. A lot of engineering ideas were necessary to develop a so-called “high-tech” variant of the mat-canning system, which fulfills all the demands without any defects, especially under European driving conditions. Apart from economy of space, additional advantages of the new converter, compared with wire-mesh systems, include lower external surface temperature and less noise.
Technical Paper

Secondary Air Injection with a New Developed Electrical Blower for Reduced Exhaust Emissions

Secondary air injection after cold start gives two effects for reduced exhaust emissions: An exothermic reaction at the hot exhaust valves occurs, which increases the temperature of the exhaust gas. It gives sufficient air to the catalyst during the cold start fuel enrichment that is necessary to prevent driveability problems. Handicaps for the wide use of air injection include space constraints, weight and price. An electrical air blower was choosen to best satisfy all these requirements. The development steps are described. The result is a three stage radialblower with extremly high revolutions of about 18000 rpm. The system configuration and the outcome are demonstrated on the new C-Class of Mercedes-Benz. The results show emission reductions higher than 50 %, while also satisfying the development goals of noise, volume, weight and cost requirements.