The DPF (Diesel Particulate Filter) is a ceramic filter made of cordierite or silicon carbide installed in the exhaust system of post-2009 diesel engines (Euro 5+). Its function is to retain particulate matter (PM10, PM2.5) before it exits the exhaust pipe.
How regeneration works
When the DPF fills with soot (60-80% capacity), the ECU starts a regeneration: post-fuel injection which burns the soot converting it into CO2 + ash. Internal temperature: 600-700°C. Frequency: every 300-1000 km based on driving style.
Common problems
- Interrupted regenerations: short urban journeys do not allow the regeneration to be completed
- DPF clogged: reconstruction costs €800-€1500, replacement €1500-€3000
- Engine oil diluted: the post-injection contaminates the engine oil
- Broken differential sensor: ΔP measurement, if faulty ECU thinks that the DPF is clogged
DPF Off
The removal of the DPF (software or hardware) is a common request but illegal in Italy for road use. See complete guide to DPF/EGR removal.
Passive and active regeneration
Passive regeneration occurs spontaneously on extra-urban routes, when the exhaust gases remain hot for a long time and burn the soot without intervention from the control unit. The active one is forced by the ECU with post-injections when the differential pressure sensor detects excessive accumulation; in the workshop, a service regeneration can be started with the diagnostic tool when the others fail.
DPF and chiptuning
The DPF must always be considered in a remapping: more torque and diesel mean more soot and more frequent regenerations. Correct tuning preserves the regeneration logic and differential sensor parameters, so as not to generate error codes or reduced mode inputs. Thermal management and regeneration frequency must be checked after the intervention, especially on vehicles for urban use.
Frequently asked question
"Why is my DPF clogged?": in most cases the cause is predominantly urban use, which prevents the regenerations from being completed. Periodic extra-urban driving at a constant speed allows the filter to regenerate. The level and dilution of the engine oil and the state of the differential pressure sensor must also be kept under control: neglecting them leads to continuous regenerations and clogging which, beyond certain limits, requires professional cleaning or replacement.