Importance

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Abstract

In a method for metering a reducing agent into a NO.sub.x containing exhaust gas of an internal combustion engine before the exhaust gas enters the catalytic convertor having at least NO.sub.x reducing activity, a minimal heat capacity, and a minimal storage capacity for a reducing agent, the engine-specific data for NO.sub.x concentration and exhaust gas volume are determined with a reference engine. The actual exhaust gas temperature of the internal combustion engine during operation is measured by a sensor. The reducing agent amount is calculated based on the engine-specific data and the actual exhaust gas temperature. Load-specific parameter changes of the internal combustion engine during operation are detected and a dynamic correction of the reducing agent amount based on the load-specific parameter changes is performed. The corrected reducing agent amount is then supplied into the exhaust gas stream. In a variation of the inventive method, the NO.sub.x concentration is determined during operation of the internal combustion engine based on data provided by a sensor arranged in the exhaust gas stream upstream of the catalytic convertor.

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First Claim