NOX-reduction on HD-vehicles-low cost quality check

The NOx reduction of recent HD-vehicle is performed mostly by means of the selective catalytic reduction SCR. There are some manufactures and some applications of SCR as retrofit systems (mostly for the low emission zones LEZ and in combination with a DPF). In charge of Swiss authorities AFHB investigated several SCR-systems, or (DPF+SCR)-systems on HD-vehicles and proposed a simplified quality test procedure of those systems. This procedure can especially be useful for the admission of retrofit systems but it can also be helpful for the quality check of OEM-systems. In the present paper the test procedures will be described and some examples of specific results will be presented. As general conclusions it can be stated: – the foundations for the quality verification procedures of SCR-systems are established, – the SCR-systems are not active at lower temperatures < 200°C, – SCR-testing on vehicle is a simple & low-cost tool for quality check, – the overall average NOx reduction rate depends on the operating profile of the vehicle – for low-load, for cold operation and for interrupted operation (HEV) there are lower NOx reduction efficiencies.