I know I'm splitting hair but after implementing emission control systems for "off-highway" equipment (excavators and container handling equipment at ports) last few years I wouldn't call it just as "catalytic converter" as on this size TDI's there is no "thing" that would do same stuff as catalytic converter does in gasoline car.
On gasoline engines, the emission control is through the catalytic converter (the internal honeycomb is made from platinum and palladium) that creates catalyst converting the hydrocarbons into carbon dioxide and water and also converts the nitrogen oxide back into nitrogen and oxygen.
On diesel depending the continents and engine cc's, the emission control can be either just SCR (selective catalytic reduction) or combination of DPF (diesel particulate filter) and SCR.
DPF and SCR requires ULSD diesel so these doesn't work on 3rd world countries with higher sulfur content..
Anyways, the DPF honeycomb traps the larger particles and the smaller particles are conveyed to SCR honeycomb together with DEF (diesel exhaust fluid here in States) / AdBlue (in Europe) to create chemical reaction resulting nitrogen and water vapor.
At some point the DPF becomes filled with particles and engine management will inject diesel fuel either directly (injector on front of DPF) or indirectly (cylinder injector spray timing while exhaust valve is still open) to burn off the soot and then convey those particles to SCR to process them as well.
The amount of water is far less than on gasoline engine with catalytic converter so I see no reason for weep hole.
Only time I see weep hole on SCR system is with vertical exhaust pointing upwards and the weep hole is used to drain the rain water that may rain in from vertical stack to prevent that amount entering to SCR, DPF and even to turbo. On horizontal lay-out there is no need for weep hole.
As gasoline car "catalytic converter" is more known to general public, by using just catalytic converter can easily create assumption those being same with gasoline and diesel while the detail of diesel requiring DEF as an catalyst to "ignite" the chemical reaction is left out of the context...
On the on-highway and off-highway equipment industry no one uses term catalytic converter and each is called with their own names , the DPF and the SCR.
On gasoline engines, the emission control is through the catalytic converter (the internal honeycomb is made from platinum and palladium) that creates catalyst converting the hydrocarbons into carbon dioxide and water and also converts the nitrogen oxide back into nitrogen and oxygen.
On diesel depending the continents and engine cc's, the emission control can be either just SCR (selective catalytic reduction) or combination of DPF (diesel particulate filter) and SCR.
DPF and SCR requires ULSD diesel so these doesn't work on 3rd world countries with higher sulfur content..
Anyways, the DPF honeycomb traps the larger particles and the smaller particles are conveyed to SCR honeycomb together with DEF (diesel exhaust fluid here in States) / AdBlue (in Europe) to create chemical reaction resulting nitrogen and water vapor.
At some point the DPF becomes filled with particles and engine management will inject diesel fuel either directly (injector on front of DPF) or indirectly (cylinder injector spray timing while exhaust valve is still open) to burn off the soot and then convey those particles to SCR to process them as well.
The amount of water is far less than on gasoline engine with catalytic converter so I see no reason for weep hole.
Only time I see weep hole on SCR system is with vertical exhaust pointing upwards and the weep hole is used to drain the rain water that may rain in from vertical stack to prevent that amount entering to SCR, DPF and even to turbo. On horizontal lay-out there is no need for weep hole.
As gasoline car "catalytic converter" is more known to general public, by using just catalytic converter can easily create assumption those being same with gasoline and diesel while the detail of diesel requiring DEF as an catalyst to "ignite" the chemical reaction is left out of the context...
On the on-highway and off-highway equipment industry no one uses term catalytic converter and each is called with their own names , the DPF and the SCR.
