yep as above, injection timing is retarded to bump exhaust temp to over 600c
so hot tail pipes, decrease fuel consumption, subtle burning smell, reduced power for around 8 minutes every 400>900 miles.
Every 2k miles for me or 400 miles when i used to use 'supermarket' deisel.
Nice deep exhaust note too when it happens.
For your info:
DPF SYSTEM (Diesel Particulate Filter)
This is a mechanical filter that "traps" the carbon particles (particulate) and the engine oil ashes in diesel engine exhaust gases.
The action of the DPF makes it possible to keep the level of carbon particles down by around 90% in line with Euro 4 and 5 regulations.
The operation of the DPF system is managed by the injection control unit by means of special strategies. In addition to the filter the DPF system comprises an exhaust gas temperature sensor and a differential pressure sensor.
The differential pressure sensor measures the pressure of the exhaust gases upstream and downstream of the filter, by means of special pipes, signalling the gradual accumulation of particulate to the control unit. The particulate accumulation process and increase in the pressure of the exhaust gases inside the filter depends on the engine load, the weight of the vehicle, the engine capacity and power. Therefore the occasional removal of the particulate is necessary, regenerating the filter by means of a procedure that makes use of multiple injections to increase the temperature of the exhaust gases (about 600°C) and consequently burn the particulate. The regeneration procedure is controlled by the injection control unit which acts: on the metering of the fuel (up to five injections in the same engine cycle per cylinder) and on the control of the air (E.G.R. and supercharging pressure).
The regeneration phase takes place in a few minutes and does not affect the continuity of the torque supplied by the engine compared with normal operation.