For the OP - your DEF is injected for the SCR portion of your exhaust. your DPF is the thing that REGEN burns are done for....
You are experiencing the same problem that the Jeep Grand Cherokee's with the baby eco diesel experiences, when driven back and forth to the mall... you've got to get the engine under LOAD, for some highway time, to allow the DPF to clear out. Push down on the GO pedal for a while....
Diesel Particulate Filter (DPF)
(2007.5 - current engines)
The DPF captures particulate matter (soot) from the exhaust stream via a honeycomb shaped element. It is said to reduce diesel particulate and unburned hydrocarbon emissions by up to 90 percent. Two regeneration modes clean the filter when it nears maximum capacity - passive and active regeneration. Passive regeneration occurs naturally anytime the exhaust gas temperature reaches the required threshold to burn the collected particulates from the filter (950+ degrees F).
Since the conditions that allow for passive regeneration don't always occur during everyday use, the engine enters the active regeneration state to periodically burn off particulates that have accumulated in the filter. A
differential pressure sensor measures the pressure difference between the inlet and outlet of the DPF in order to monitor the filter's capacity. An exhaust gas temperature and oxygen sensor mounted in the inlet of the DPF provide additionally information to the engine control module. During active regeneration, commonly referred to as "reburn" or "regen", diesel fuel is introduced into the exhaust stream by an injection event occurring late in the power stroke and/or through the exhaust stroke.
Early regen strategies proved widely unreliable and DPF clogging issues were common. Most of these concerns have since been alleviated due to a more effective regeneration strategy. The disadvantage of the DPF system is significant reductions in fuel economy, although the introduction of selective catalytic reduction for the 2013 model year has proven to offset some of the efficiency concerns by reducing the frequency of active regenerations.
Selective Catalytic Reduction (SCR)
(2013 - current engines)
Cummins first required SCR for the 6.7 liter for the 2011 model year Ram chassis cab pickup line. The technology later became standard on all 2013+ model year Ram pickups equipped with any version of the 6.7L Cummins turbodiesel. The SCR system requires the use of diesel exhaust fluid (
DEF), a substance comprised primarily of urea and water. DEF is injected into the SCR catalyst where a reduction reaction occurs, converting nitrous oxides into harmless water and nitrogen gas. While it adds significant cost to the price of a new vehicle, it reduces both the EGR and DPF regeneration duty cycles. Ideally, a tank of DEF should last between oil change intervals, though towing and stop-and-go driving may require more frequent refills.