Row SCR works
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m Urea is non-toxic, colourless and odourless. The SCR system is made up of an additional tank and electronic metering unit for the reducing agent—prototypes have featured a OSlitre tank positioned directly adjacent to the main fuel tank—and a ceramic catalyst housed in the silencer.
Nitrogen oxides are reduced in the catalytic converter via ammonia created from the addition of aqueous urea solution to the hot exhaust gases. The precise quantity metered is calculated by the engine's electronics system and on average will be around 6% of the diesel fuel used.
ilaimlerChrysler is already working with mineral oil suppliers on ways in which to ensure the general availability of urea in time for the introduction of Euro-4. The spokesman says the urea solution will be probably be distributed via current fuel suppliers.