TDI Engines.

Modern diesel engines emit substantially less particulate matter than older engines. Diesel particulate filters are very effective in minimising particulate emissions. The filters are capable of trapping even the finest soot particles produced by the combustion of diesel fuel.

The latest generation of diesel particulate filters at Volkswagen operates without additives and is therefore completely maintenance-free for a long time. An initial inspection is usually carried out after 150,000 km. The filter’s lifespan is dependent on factors such as fuel quality, driving style, use and oil consumption.

The coated filter consists of a porous ceramic component with a coating containing precious metal. As the exhaust gas passes through the filter material, particulate matter is detained while the gases flow on unhindered. To ensure the filter’s long-term permeability, it needs to be cleaned of the trapped particles.

To clean the filter, the trapped particulate matter is periodically removed. In passive regeneration, the soot is slowly and gently converted to CO2. This process requires an exhaust temperature of over 630 °C and takes place without the need for special measures, e.g. on the motorway. Only when the vehicle is driven for long periods at low load, e.g. in urban traffic, is the filter actively cleaned.

This is achieved by raising the exhaust temperature through alterations to specific engine parameters. The detained soot particles are burnt off every 1,000 to 1,200 km. The positioning of the filter close to the engine means that the exhaust gas temperature is sufficient to convert the soot particles while the engine is running. This results in low component stress and good filter efficiency.