Filter systems in conjunction with low nitrogen oxide engine tuning will no longer be sufficient for future legal exhaust-gas regulations. In many cases, an active nitrogen oxide reduction based on NO_x storage catalytic converters or SCR catalytic converters in the exhaust-gas system will be used. In particular, the selective catalytic reduction by means of urea or hydrocarbons is very effective , but it requires high tuning efforts – on the one hand for the demand-based dosing of the reducing agent, on the other hand for a flawless interaction with other components of the exhaust-gas system.