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The Selective Catalytic Reduction (SCR) is the main after-treatment solution for high efficient diesel engines under development to cope with future lower fuel consumption and NOx emissions requirements (EU6+ legislation). Exhaust gas temperatures are decreasing too, leading to new after-treatment system developments in a close coupled position. Nevertheless before all vehicle architectures allow it, SCR systems are and will still be installed in underbody position. The current paper deals with an underbody metal SCR after-treatment systems, which is capable of active thermal management, and an ultra-compact SCR dosing system. These technologies are described and emission results obtained on several application examples (from passenger cars to light duty commercial vehicles) are presented and discussed in conjunction with an effective active thermal management of the SCR function.

More efficient and durable catalytic converters for the two- and three-wheeler industry in developing countries are required at an affordable cost to reduce vehicle emissions, to maintain them at a low level and therefore to participate in a cleaner and healthier environment. This particularly is true nowadays, because the demand and prices of Platinum Group Metal (PGM) for catalyst are continuously increasing due to i) the worldwide progressive implementation of motorcycles emission legislations similar to Euro 3 Stage requiring catalysts, ii) the need for non-road diesel vehicles to be equipped now with catalyst systems, and iii) the constant increase of the worldwide automobile market. A new generation of metallic substrates with structured foils for catalytic converters is proven to be capable of improving conversion behavior, even with smaller catalyst size.

On one hand, latest worldwide emissions legislation developments aim to reduce NOx and Particulate Matter (PM) emissions of all diesel engines, while on the other hand lower fuel consumption diesel engines are still required for lower fleet average CO₂ emissions. As a consequence of the chosen CO₂ optimized combustion mode, the raw NOx emission increases and as such Selective Catalytic Reduction (SCR) technology will be the future choice for high efficiency NOx aftertreatment. This paper deals with SCR technology and its derivative SCRi® technology, when diesel particle reduction is required, especially for heavy-duty applications. Alongside the developed metal catalyst technologies, a complete SCR reducing agent dosing system is presented. Emission results gained with the SCR or SCRi® technologies on European commercial engines illustrate the potential of these technologies for conversion of NOx and PM emissions.