DPF Regeneration

Just what are the issues with a DPF filter?

If you use your modern Diesel car for short journeys in and about town the filter does not warm up sufficiently to burn off the soot that is caught in the filter, the filter must reach temperatures of 350-500oC to fully burn off the soot. Overtime if you consistently do short trips in your Diesel car the filter will become blocked. Usually a long trip every week or so will clear out the filter by means of “passive regeneration”

What happens when the DPF filter is blocked?

When the DPF filter reaches about 45% blockage the filter will begin “active regeneration” this means that the EGR (Exhaust gas Recirculation) valve is closed, the boost pressure from the turbo is increased slightly along with a slightly higher idle RPM. Diesel is then injected into the cylinders just after combustion so that it enters the Exhaust further heating up the DPF to around 600c and clearing the soot from the filter.

If however you switch off the engine before the DPF has been cleared you will get a DPF warning light on your dash.

What should I do if I know it is blocked?

You can replace the DPF filter which is normally a costly option.

Here at P&R BMW we have specialist equipment whereby we clean your DPF, and then carry out a forced regeneration using the BMW diagnostic machine.

Can I remove the DPF?

We do not remove diesel particulate filters and remap the ECU of vehicles as this is not legal. According to the DPF guidance sheet on the .GOV website it is an offence to remove the DPF filter.

Below is a copy of the relevant paragraph.

It is an offence under the Road vehicles (Construction and Use) Regulations (Regulation 61a(3))1 to use a vehicle which has 
been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. 
Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use.