The diesel particulate filter does exactly what it says on the tin. It cleans the particles as they exit the engine after combustion. Without this not only would your diesel car emit considerably greater dangerous emissions but you would also fail your MOT under the new 2018/19 standards.
The term Dirty Diesel comes from this knowledge that diesel fuel burns to leave soot and leaves residue. Compared to petrol and alternative fuels, in its raw form Diesel produces high particulates and 'dirt'. If you've ever seen a big tankard lorry or a big block engine for typically American trucks, when revved and driven hard you often see billows of smoke and soot from the exhaust pipes. Especially the heavily modified engines can produce clouds of black smoke as they remove the DPF to maximise power and create outlandish chromed exhaust pipes to the sky. The DPF is there to catch all those soot particles and fine dust from the burnt fuel via a membrane of filters much like the intake air filter does.
Unburnt fuel build up. If a diesel engine cannot fully heat up the entire exhaust system, it cannot burn off any residue, and therefore it stays in the DPF filter until next time. Each time this happens the layers of soot build up and end up restricting flow.
Yes, it is the job of the DPF to filter these particles, however, the reason it works overtime is that once the filter maintains a level of build up residue it will actively work to 'regen' the system by superheating the elements to burn off this build up before it clogs the pipes.
If you imagine you have a 2" exhaust it's capable of a large amount of air flow. Your 200hp engine has been tuned for 'x' amount of air flow into the engine and 'x' amount out, automatically adjusting fuel/air mix for the required power.
Now after a few years of driving to the shops and back, short journeys, not getting very hot your 2" exhaust pipe has so much build up of soot and particles, it's functioning like a 1 1/2" pipe with a 25% reduction in air flow.
As your engine has to work harder to adapt to your clogged pipes, like a drain the flow is slow, the air cannot escape as quickly as it needs to and your engine ECU will make adjustments based on the restrictions. These adjustments will result in less power from a starved engine and reduced economy in MPG adding greater wear to the car components. For the same effort put in you are getting reduced power, like a mobile phone battery over time it just won't work aswell.
You'll be pleased to know you can do it yourself. Or rather the car will actually do it for you. This was part of the key selling point of diesel engines when they started to rise in popularity. If you often do long journeys over 30 minutes or enough time to allow the car to reach a high overall temperature, in theory, your car should naturally heat off the excess soot and build up and pass it through the system. Doing a long journey over an hour around the M25 (without traffic) for example gives the car a chance to get up to a good speed, heat up all the elements with multiple fast moving parts and naturally clean itself. Much like how you can clean an oven by superheating it at maximum temperature, your car works the same way to dislodge any stubborn particles.
This is not full-proof though. Ultimately over time, there will be unavoidable build up, you cannot burn it all off and it will dirty up your cars' insides. That's where we come in. We've recently upgraded ourselves with a Stage 2 chemical deep clean machine designed and dedicated to cleaning DPF filters on site. Not only will it clean your DPF but it will also cleanse the exhaust system and we can do it easily on site. For £175 we offer this full clean with a regen to aid the natural processes of the engine and restore it like it was a new machine.
We have found this level of clean is the only one we will provide. Although there are 'quick cleans' available, we don't want to see you back in a month with the same problems or seeing minimal improvements. As much as we like to see your smiling faces, we'd rather fix and protect your car for years, not months. By choosing the full clean you can rest assured we can restore your car back from the depths of sooty hell, or simply give it a refresh if you're worried about its long-term performance. Whatever your level of restoration, we have the solution for you.