Diesel particulate filters restrict exhaust free flow and once they are blocked, it becomes like having a potato stuck up the tailpipe!
A Diesel Particulate Filter (DPF), sometimes called FAP on French vehicles (and of course fitted in Mini Diesels), is a filter designed to collect the diesel particulate matter (carbon soot) from the exhaust gas of a diesel engine.
The particulate accumulates in the filter and this needs to be emptied for the filter to continue functioning. The filter burns the particulate at very high temperatures before blasting the treated content out the exhaust.
DPF Sensors monitor the accumulation of soot to calculate when regen is required, temperature is also monitored and controlled. Some DPF systems have a DPF PAT fluid system to assist with regen cycles, often by allowing the regen to occur at a lower temperature. The fluid will need renewal periodically.
A high quality chemical properly and directly applied to the DPF filter will always work provided the filter isn't starting to collapse. We have successfully cleaned DPF filters that were so blocked that the vehicle no longer ran or started.
Cleaning a DPF filter has the same pitfalls as replacing it. Whilst we guarantee to unblock a blocked DPF, we cannot guarantee to keep it unblocked. This is why we always perform an initial assessment before we agree to any DPF works.
If the DPF filter has started to collapse, cleaning it will not work. We cannot always guarantee a filter hasn't started to collapase internally (nobody can).
As with replacing a filter the cause of the DPF blockage must be addressed.
The way you drive your car often leads to the DPF blocking. Short journeys, switching the car off whilst its performing a regen (DPF light comes on and people switch the car off despite the handbook advising against). Normally driving style affects the earlier DPF filters more, pre 2010 cars.
At some point the filter will start to break up, this happens in about 10% of all the DPF filters that we see. Typically with over 150,000 miles on the car or where lots of short journeys with excessive regens. Basically because the filter goes through hot and cold cycles it evenautally cracks.
EGR, Pressure Sensors, Injectors, Air Leaks, MAF, Turbo and a whole host of other problems can easily cause your DPF to block. We often repair vehicles that have had a DPF filter cleaned or replaced elsewhere only for the filter to block within a matter of days or weeks due to an underlying issue upstream.
We are able to offer a complete DPF removal package for all BMW and Mini DPF Filters.
There are a number of pitfalls to this, most notably is that you should inform the DVLA as the vehicle will no longer be compliant with EU4 or later emissions regulations and may be taxed differently.
After a DPF removal you will benefit from:-
You will not be able to tell visually that the DPF has been removed, nor will a standard MOT test be able to detect an increase in NOX or Soot Emissions.
Removing a DPF filter will increase Soot and Particle Emissions
However, because you gain MPG benefits you are burning less fuel.