Diesel catalytic converter.

Cleaner running and dynamic performance: the diesel catalytic converter fitted to BMW diesel vehicles helps reduce emissions of gases and particulates.

Petrol engines use a three-way catalytic converter, which reduces oxides of nitrogen (NOx) and oxidises hydrocarbons (HC) and carbon monoxide (CO). BMW diesel engines use an oxidation-type catalytic converter to oxidise hydrocarbons and carbon monoxide using the oxygen present in diesel exhaust.
The post-oxidisation also serves to reduce the soluble organic fraction of particulates. The catalytic converter consists of a ceramic block with a honeycomb structure: the channels of this honeycomb possess a high-performance platinum washcoat. In BMW vehicles, the converter block is located close to the engine, providing it with the warmth it needs to function efficiently.