The key issue with DPF systems is regeneration—i.e., how to clear away those particles the filter captures.

Ford’s current DPF systems—those noted above—rely on the use of a cerium-based fuel additive (Rhodia’s EOLYS) to enable diesel particulates to oxidize at relatively low temperatures in the filter.

(EOLYS significantly lowers the light-off temperature of the soot and the heat of the resulting combustion process to maintain the long-term integrity of the filter.)

With such systems, additional attention must be paid to the collection of ash residues in the particulate filter.

These ash residues come from four sources: engine wear, fuel, oil and the fuel additive itself. The ash is inert, and the filtration efficiency of the DPF is so high that ash is eliminated from the tailpipe emissions. However, storage is limited, and thus requires the system to be serviced.

The next Ford product to be equipped in production with a DPF system will be the Ford Mondeo.

Although the Ford Mondeo TDCi powertrains meet Euro 4 standards without a DPF, the 85-kW (114 hp) and 96-kW (129 hp) versions of the 2.0-liter TDCi engine will be offered with an optional catalyst-coated DPF (C-DPF) system from early 2006.

In this system, the internal surface of the filter itself is coated with a catalyst to enable oxidation of particulates in the filter (eliminating the need for the liquid additive).

The Mondeo TDCi with C-DPF will initially be offered in Germany plus the Scandinavian, Austrian, Swiss and French markets. Other markets will follow shortly afterwards, depending on demand which in turn is largely driven by local governmental tax incentives or penalty regulations.

Ford is also working on a solution to provide older cars calibrated to the Euro Stage 3 and 4 emissions standards with retrofit DPF systems. Ford will soon begin to market these kits as Ford Motorcraft RetroFit systems.

Unlike the closed ceramic filter body used in the volume production models, the Motorcraft RetroFit kit consists of a wrapped metal foil system with trap pockets to filter the flow of emission gasses.

Unable to rely on more modern engine management systems to handle regeneration, the Motorcraft RetroFit system relies on the filter’s natural regenerative capabilities under the heat of higher load conditions.

The Ford Motorcraft RetroFit system has therefore been designed to be open, to allow the engine continuous and unrestricted operation even with a fully loaded filter. The overall efficiency of this filter system has been determined to be between 30% and 40% compared to the 99+% of the others.