Daimler Chrysler Ag

Peter Renninger

Siegfried Sumser

Helmut Daudel

In the engine braking operation of supercharged internal combustion engines, the braking power is generated by backing-up the exhaust gas before it enters an exhaust gas turbine of an exhaust gas turbocharger from an actuator in the exhaust gas duct. In order to make it possible to control the braking power within the operating limits of the exhaust gas turbocharger, the actual value and a maximum value of the turbine inlet pressure within the operating limits of the exhaust gas turbo supercharger are inferred from a performance graph of the internal combustion engine, which performance graph includes an electronically stored compressor performance graph of the supercharged air compressor which represents the relationship between mass throughput and total pressure ratio of the compressor and in which a plurality of engine operating lines for certain actuator positions and certain engine speeds as well as for a constant turbine inlet pressure are recorded. The maximum value arises as a function of the engine speed from a characteristic rotational speed line stored in the performance graph. Corresponding to the desired braking power, a nominal value which, together with the actual value of the turbine inlet pressure, serves in the control circuit as an inlet parameter for an engine controller for a comparison of nominal and actual values, is determined proportionally from the maximum value.

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Stuttgart, Germany

Peter Renninger