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How the Diesel Particulate Filter Works

Europe loves turbo diesel-powered automobiles and it is hardly a surprise why. Truth be told, hybrid vehicles and their electric counterparts still have a long way to go to make sense range-wise and money-wise, while modern turbocharged petrol engines are criticized by many for drinking way more fuel in real world driving conditions than what automakers normally tell you.
Diesel particulate filter 1 photo
When animated by a turbo diesel engine, everything from a Citroen C4 Cactus to a Mercedes-Benz CLA and even SUVs such as the BMW X3 are far more economical propositions than their petrol-fed counterparts. Another aspect that sort of explains why Europeans are so fond of oil burners is rather simple: these babies have smaller torque bands than petrol engines, but develop more twist from lower in the rpm range.

Whether you want to accelerate quickly to 30 mph (roughly 50 km) when the lights turn green or you need to tow and haul junk from point A to B, a turbo diesel is the best way to go. But there’s something you need to look out if you’re on the oil burning front: turbo diesel mills are more expensive to service.

If a component of the exhaust system referred to as the diesel particulate filter (or DPF for short) goes kaput, replacing it will set you back from £1,000 (€1,275) to £3,500 (€4,465) depending on the model.

This apparently unimportant contraption is the subject of our latest guide, but before we go further, let’s go through a bit of DPF history. Particulate filters have been used on non-road machinery since 1980, while high-end vehicles, trucks and lorries adopted them starting with the mid-1980s.

After the first California Heavy Truck rule from 1987, the European Union and the rest of the world followed suit and the DPF eventually became mandatory on all brand spanking new turbo diesel cars.

Now for the basics. Designed to lower emissions, particulate filters are to blame for the black exhaust fumes you sometimes see produced by the car in front of you when the driver gives it no quarter.

As simply put as possible, the particulate filter looks a lot like the Audi A8 3.0 TDI unit in the pic above, and it’s a part of the exhaust system because it’s sole purpose is to eliminate particulate matter from exhaust gases as much as possible.It doesn’t look like much, but the DPF's role is of extreme importance
Like any consumable, the DPF is a service item and every manufacturer guarantees under warranty how much a unit will last if the owner drives his car normally. Blockages and erroneous regeneration cycles may damage the component prematurely, but these things normally happen if the driver doesn’t let the regeneration cycle complete.

Most common scenario: drivers who make frequent short journeys (in the city, for example) at low speeds, journeys that don’t let the DPF effectively regenerate itself, deleting the soot collected by the filtration system. Now you might be wondering what’s it made of and how does this thing work.

As simply put as before, a DPF’s metal shell hides a rather complex mixture of liquid and solid components, the majority of being made up of carbon microspheres on which fuel soot (mostly hydrocarbons) condensates, soot resulted from the suck, squeeze, bang, blow end of the deal. 

By condensing the yucky stuff, a particulate filter greatly reduces the harmful molecular yuck eliminated through burning diesel. As the online diesel particulate filter encyclopedia points out on, this process eliminates at least 80 % of soot matter from the combustion cycle's exhaust gases.

German automakers lately started an affair with selective catalytic reduction reduction (or SRC). This system is an alternative approach to reducing NOx by injecting AdBlue (32.5 % urea and the rest water) into the exhaust system after the oxidizing catalyst and the diesel particulate filter work their magic.

This lorry world-inspired solution to reducing NOx does the job well, but also improves combustion and diesel fuel economy by reducing the duties of the EGR (exhaust gas recirculation) system.

With the current Euro 6 emissions standards, as well as their CAFE 2016 counterparts from across the pond, diesel emissions technology is getting more attention than ever. It’s an uphill battle for many to meet the new stringent regulations, but I have faith in the future of the humble oil burner.

Despite the recent announcements according to which Paris and London will ban diesel cars from driving inside the city by 2020, I recommend you to don’t believe the hype. The automotive industry will undoubtedly advance at a very fast pace, so will the turbo diesel engine and the diesel particulate filter.


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