The Diesel Particulate Filter is in the exhaust system of all diesel-powered cars sold new since 2009. It is a vital component that is designed to enable cars to pass increasingly tough emissions legislation. The DPF’s job is to trap the particles that are caused by the compression-ignition combustion process and thereby prevent harmful smoke from being pumped into the atmosphere.
How does it work?
Like any filter, the DPF will gradually get clogged with the soot that it traps. However, the car is designed to clean it by heating this residue up, turning it to ash and expelling it. This happens about every 300 miles, either when you travel at motorway speed, or because the Engine Control Unit initiates what’s known as regeneration by raising exhaust temperatures artificially.
In order for a DPF to efficiently burn off the soot inside of it, the engine needs to be nice and hot. Many diesel car owners are not aware of this and it is because of this that some owners are having problems earlier than they might expect (assuming that they are even aware they have a DPF on the car in the first place). Clearly, to get a car hot, it needs to be driven. The first 10 minutes of any journey from a cold start are when the car produces the most emissions and so, if the car is being driven for short times only, to the shops and back, to drop the children off at school or even on just some slow town driving, the engine will not get hot enough to burn off the particle matter in the filter. It is this kind of driving that produce, more problems with DPFs than any other.
If you do find that your car is feeling far more sluggish than normal and/or there is a DPF warning light on the dash – DO NOT IGNORE IT. Driving the vehicle with a blocked DPF can seriously damage your engine / turbo and it’s not uncommon to have to replace a turbo when the warning light has been ignored for extended periods.