How it works.
SCR is an aftertreatment system that uses an external catalyst to convert NOx into nitrogen and water. The chemical reaction is initiated by a non-toxic, odourless mixture of chemical urea and purified water called Diesel Exhaust Fluid (DEF or AdBlue).

The engine has been designed for optimal power and performance, reducing the PM created by incomplete fuel burning. In the end, exhaust from Steyr SCR engines is cleaner than the intake air.