Like them or loathe them, they're here to stay. Every diesel engined vehicle from around 2008/9 onwards has one, but they're very often mis-understood and many of the problems we hear about are not directly the fault of the DPF, and in many cases the DPF is wrongly blamed because garages/mechanics fail to correctly diagnose the root cause of why the DPF has a problem.......
Let's start with the what?.......
In essence, a DPF is a just a filter. It allows exhaust gasses to pass through it but traps larger soot particles and prevents them from exiting the exhaust and polluting the atmosphere.
Why?..... Well, primarily because European Emissions Regulations dictate that diesel soot emissions need to be under a specific level for Euro 4 compliance onwards. The other reason is the obvious one..... So that we don't breathe it in.....
And then the how?.......
Soot/Carbon is a natural byproduct created by burning fossil fuels, and diesel is the most filthy of them all.....
Hold a piece of paper over a candle and it will turn black from the soot. The same is emitted by an internal combustion engine, and diesel will emit the most soot of any engine. Frankly, it's filthy!
To further reduce the soot emissions of an engine, the European Emissions regulations were tightened in the UK in January 2005, commonly known as Euro 4, and subsequently many engines that didn't meet the requirement needed DPF's to be fitted. We're now on Euro 6 and the DPF is still a mainstay component.
So how does the DPF work? In much the same way as a self-cleaning domestic oven..... It heats up and burns the carbon into ash. The ash particles are then small enough to pass through the filter.
TBC...