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Future emission legislation and new diesel engine technology tighten the requirements for modern diesel vehicle exhaust after-treatment systems. In particular, the oxidation catalyst system requires more efficiency to treat increasing raw emissions of HC and CO at low exhaust gas temperatures resulting from advanced combustion processes. This represents a big challenge for all developers today where the cost of raw materials continues to rise. Splitting the oxidation catalyst volume into two parts and mounting a very small part in front of a turbocharger on Euro III or Euro IV Diesel engines has been proved very efficient: Light off and maximum pollutant conversion rates were improved. New results gained with Pre Turbocharger Catalyst (PTC) on a Euro V type diesel engine are confirming previous observations. The complete after-treatment system of today's vehicles should be designed and developed for the whole life of the vehicle.

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.

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.