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Opel Offers Particulate Filters on All Diesels for Germany


GM’s Opel has announced that it is offering a particle filter (DPF) on all diesel-powered cars it sells in Germany. The move follows the German government’s decision to offer tax subsidies to owners of vehicles equipped with such filters, effective from 1 January 2005.

Earlier this year, Mercedes-Benz became the first manufacturer to make particulate filters standard on its diesel vehicles. (Earlier post.)

In May, Opel had increased the number of models with a DPF as standard to include all 1.9 CDTI Vectra, Signum and new Zafira models.

The Opel DPF is a platinum-impregated catalyzed system, similar to that used by VW/Audi, BMW, and Renault. It operates without additives, and requires no maintenance.

Pressure and temperature sensors in the DPF recognize when capacity is reached. At that point, the engine management system increases the temperature of the exhaust gas via multiple injection, burning the soot particles and restoring the capacity of the filter.



Ron Fischer

When the particulate filter is 'full' and the burn-off process occurs doesn't this release the same particulate material, just converted into an even finer form, and in a different location?


Not in the sense that you mean. The ideal oxidation reaction of the regenerative burn-off converts the soot particles (primarily carbon) to CO2 and H20—think of it as gasifying the soot.

In practice, given the different attributes of soot, and the regenerative process, there will likely be CO, HC and other emissions attendant.

So, yes, you’re outputting more CO2, CO and a level of ride-along contaminants, but no, you’re not outputting more PM.

Checking for and managing secondary emissions is a big part of the development and testing process of the DPF.

The purpose of the filter, though, is not to eliminate all emissions—it’s specific to dealing with the soot particles that have their own toxic attributes based on size, etc.


Something that has bothered me for a long time is the issue of particle size when discussing PM filters. While it is incontrovertible that the filters reduce PM output by mass, do they reduce the number of fine particles? This is of course the real objective, as particles on the order of 100nm and smaller are the biggest health concern. If you eliminate PM2.5 and PM10 at the cost of higher levels of particles with diameters on the nanometer scale, you have actually made the health situation worse.


DPFs have been shown to be about equally effective across the entire size distribution range. As a matter of fact, many studies have shown that the exhaust of a DPF-equipped engine has (numerically) fewer aerosols than the intake air. See, for example, slide 10 in this presentation: .

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