DEF/Regen Question

[Berrigan]

This morning the truck (2016,2500)(need to update my sig) went into regen again. At the beginning I was stopped and it was quiet in the cab. Then the drone of the engine at idle changed and almost sounded like the exhaust brake was on. I did not have it on, nor did I think to look at the evic to see if it was on. Then while driving the instantaneous mpg was much lower than normal and the regen smell was noticeable. At the next stop light the engine idle seemed normal again. So my 3 questions are, is it possible energizing the exhaust brake is part of the regen process?

Is the extra fuel used in the regen process consumed at a constant rate or does it vary?

Is DEF used at a constant rate or does it vary, and or is DEF used only when not in regen mode.

Thanks to all for any input, these are things I am curious about.

 

[kthaxton]

I can only partially answer your last question.

DEF is not consumed at a constant rate, more load/fuel = more DEF.

As to DEF being used during regen....while I don't know this for a fact, I am reasonably certain it is still used during regen.

 

[pcdavis]

My truck's exhaust sound also changes during regen. It may be partially engaging exhaust brake, which changes the pitch of the turbo blades thus the change is sound. I think this is to help raise the exhaust temperature to clean the soot from the DPF.

Extra fuel is to help raise the exhaust temp and mine stays at a constant higher rate until regen is complete. I have had regen stop and then restart again when speed or other conditions change. There are sensors in front of and back of the DPF that measure back pressure and regen will continue until the soot is cleared and the filter is opened up again.

From my understanding, DEF is used as a catalyst for the SCR filter and really has nothing to do with the DPF filter or regen. If your engine is under a heavier load, DEF usage is higher. Lighter load, less DEF

 

[JLandry]

Is DEF used at a constant rate or does it vary...

Per Cummins, DEF is consumed at approximately 2% of fuel consumed (roughly a 50:1 ratio). See the attached Cummins DEF Q&A for more information.

John L.