DPF regeneration is the process that cleans the particulate filter by burning accumulated soot. Three types:
- Passive: occurs naturally on the motorway with the exhaust already hot
- Active: the ECU forces a post-injection to warm up the DPF (every 300-1000 km)
- Forced: in the workshop with a diagnostic tool, when the car enters limp mode
What happens during
For 10-25 minutes: exhaust temperature rises to 600-700°C, engine fan goes to maximum, consumption doubles, white/yellow smoke may come out. DO NOT turn off the engine during an active regeneration — interrupt it = cycle aborted = DPF clogs faster.
Common problems
- Short urban cycles: regeneration never completes
- Diluted oil: post-injection ends up in the engine oil
- Dirty sensors: the ΔP DPF differential sensor faulty
See DPF.
What to do during a regeneration
When an active regeneration is in progress it is best to continue driving at a constant speed until it is completed: turning off the engine interrupts it and the cycle will have to start again, accelerating the clogging. Typical signs are increased consumption, the fan at maximum and sometimes a smell or light smoke from the exhaust.
Prevention and tuning
On vehicles mainly used in urban areas, regenerations are not completed and the filter becomes clogged: periodic extra-urban cycles help. On the chiptuning side, every intervention must preserve the correct regeneration strategy and the parameters of the differential sensor: altered management leads to too frequent or absent regenerations, with dilution of the engine oil or premature clogging of the DPF.
Good habit
Recognizing the signs of a regeneration in progress (increasing consumption, fan at maximum, light smoke) and completing it without turning off the engine is the single habit that most prolongs the life of the engine. DPF. On vehicles for urban use, planning an extra-urban journey every now and then is a form of preventive maintenance. On the software side, any intervention must preserve the regeneration strategy so as not to trigger anomalous cycles or premature clogging of the filter.