If you haven’t heard of a DPF (diesel particulate filter) before, this surprising little piece of technology is one of the most interesting and troublesome parts of a modern diesel engine.
Put simply, a DPF does exactly what is says on the box, it removes particulate matter (sooty emissions) from the exhaust before it exits the vehicle and attempts to burn it in a more environmentally friendly manner.
However, while this seems like a simple solution to a big problem, is it really all it’s cracked up to be?
As with anything, the DPF is somewhat of a compromise between regulation and performance. While on the surface the DPF is a great system, it relies on a few key things to operate effectively, extreme heat and longer running times.
Because of the heavy (relative) nature of diesel soot, these particles are incredibly difficult to break down. The process of breaking them down requires a large amount of heat and time to burn the particulate enough that it is less toxic.
When buying a diesel vehicle, this is something that many people don’t consider, driving only to and from work or on shorter trips. However, when taking into account the fact that diesels take longer to warm up in general, the time that they may need to become hot enough to burn these particles often becomes longer than the trip overall. This can cause blockages in the DPF system.
In normal operation, this really isn’t so bad and the vehicle will usually flash a warning light on the dash which can be cleared by taking a long, hard drive. However, when left ignored, these filters can often become completely blocked meaning they need to be forced to burn off or replaced.
Toyota has had a lot of issues with this exact problem lately which can be seen here. When these manual burns are required, quite often the car must be parked up in a mechanics shop and run for 20 minutes-2 hours at high rpm. By running the motors at high rpm’s and dumping fuel into them, they effectively force the exhaust to become hot enough to manually burn off the particulate.
Though this is a fairly regular practice, it has left a lot of mechanics wondering what the long term effects are of running these vehicles hard enough and hot enough to shoot soot out the back like a ye olden chimney sweep.
What is the solution though?
First, buy a car that suit’s your needs. Check out our blog that weighs up the benefits of petrol vs diesel.
After that, the best medicine is prevention. The way to prevent these DPF issues is to regularly drive the car for a longer period of time and harder than normal. Once per week or fortnight, take an hour long drive on the highway and, if you have a manual option on your gearbox, you can even run it one gear lower than normal for a while on this drive.
This usually allows these cars to get hot enough to start to work their magic and can prevent DPF issues for a long time.
If you have any questions about this blog post, would like a second opinion from a mechanic or would like to find an honest mechanic in Brisbane, check out Kashy here.