The ceramic Cylindrical filter has many small square channels running in the axial direction seperated by thin porus walls. These channels are plugged in one end but open on the other. This way the soot laden exhaust gases are forced through the walls. Particulates are too big to escape and are trapped in the filter walls. (Called Wall-flow monolith) (See attachment.)

A Catalyst is also coated to these walls giving the soot a lower combustion temp allowing the filter to regenerate (This is why it never gets completely clogged.) Periods of exhaust temps of 615-750*f cause the soot to burn, regenerating the filter. This makes our systems "passive" as there are no active mechanisms to clean them.

The filters efficiency raises with soot accumulation, but even at low soot levels, it is 90%+ effective at catching soot.

Typical exhaust pressure drops are 20-40" of H2O (0.75-1.5PSI)

Uncontrolled Regeneration
Runaway regeneration or thermal runaway.
This refers to the uncontrolled burning of a Large quantity of soot accumulated in the filter media.

It is caused by a series of events starting with overloading the TrapOx with soot at exhaust temps not high enough to cause regeneration (Lots of stop-go traffic on a cool morning with exhaust below 600*f) followed be a period of high exhaust temps that ignite the soot, and followed finally by low power or idle operation which raises the Oxygen level of the exhaust (Race on the highway at 85mph with a warm/hot engine then stop for rush-hour traffic.)

Thermal runaway can easily cause filter temps that will MELT the filter media or cause thermal stress that can crack the filter (This is what caused so much turbo damage on MB's). If water gets in/on the filter it is possible for the unit to EXPLODE! (This HAS happened, but you will never hear it from Mercedes-Benz)

If you have not had the FREE recall performed on your MB, this should be more than enough reason to swap it for the OxCat (Or replace the entire setup with a "federal" intake/exhaust system ).

Attached Thumbnails

 

Both done on mine, OxCat replacement by the previous owner and fed version swap by me.

I bet an OxCat will not last either.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012