17 April 1999
PSA Peugeot Citroen unveiled a diesel particulate filter system which is expected to go into production in the year 2000. The filter is designed to reduce particulate emissions from diesel fueled cars to levels required by the year 2005 EU emission standards.
Peugeot will fit the filter on a 2.2 liter, common rail diesel engine which will go into production early next year. Initially, the filters will be available on a relatively expensive Peugeot model 607. As the cost of the filter system decreases, Peugeot hopes to be able to equip its entire line of cars with particulate traps.
The Peugeot filter system utilizes a porous silicon carbide substrate. It also includes an oxidation catalyst upstream of the filter. Regeneration of the filter, which occurs every 400-500 km, is controlled by the common rail injection system. Multiple post-injections of fuel during the regeneration period increase the combustion temperature. The oxidation catalyst oxidizes unburnt hydrocarbons generated by the post-injections, releasing additional quantity of heat. Both effects increase the exhaust gas temperature to about 450°C.
A fuel additive (cerium based Eolys by Rhodia) is used to lower the combustion temperature of soot, allowing the filter to regenerate at temperatures below 450°C. The additive is stored on the vehicle and automatically dozed. After every 80,000 km the filter must be cleaned from the additive ashes by flushing with water, and the additive replenished.
Peugeot said it invested 400 million francs ($66 million) to produce the filter system.
Particulate traps were first introduced to German cars sold in California in the 1980's. Due to technical problems traps were quickly abandoned and have not been used on diesel cars since that time. The Peugeot would be first modern, mass-produced automobile equipped with a diesel particulate filter.
Particulates are perceived as one of the most troublesome of diesel emissions. Carmakers are under increasing pressure from environmental regulatory authorities, both in EU and in the US, to reduce the particulate emissions. For example, emission levels specified by the newly adopted California LEV II standard (year 2004) appear to be impossible to meet without diesel particulate filters.