Particulate filters explained

By David Bonnici, 08 Aug 2016 Car Advice

Volkswagen Tiguan

Volkswagen is following Mercedes-Benz’s lead by introducing particulate filters to petrol engines to further reduce emissions. But what are particulate filters and how do they work?

Volkswagen has taken another step to show it’s serious about reducing emissions by introducing particulate filters for petrol engines across its group.

From 2017, all Volkswagen Group direct injection TSI and TFSI engines will be fitted with petrol particulate filters, which it claims will reduce emissions of fine soot particles by up to 90 per cent.

The 1.4-litre TSI engine in the new Volkswagen Tiguan and the 2.0-litre TFSI engine in the Audi A5 will be the first engines to be equipped with the filters, from June next year.

This follows Mercedes-Benz’s recent announcement that petrol engines in the upgraded Mercedes-Benz S-Class model will come fitted with particulate filters.

SO WHAT ARE PARTICULATE FILTERS AND HOW DO THEY WORK?

  • Particulate filters aren’t new. They’ve been fitted to diesel engines for some time, which why you no longer see them bellow black smoke. But the move by Mercedes-Benz and Volkswagen is a first for petrol engines.

  • The filter is located in the exhaust system to capture small soot particles, which stops them entering the atmosphere. As with any filter it needs emptying periodically and this is done automatically, by burning up the particulates in a process called regeneration.

  • Regeneration requires high temperatures from driving for at least 15 minutes – this is one reason why diesel cars aren’t really suitable for low-mileage city driving.

  • If regeneration is unable to occur the filter can block causing damage to the engine, though this is less of a problem with newer engines that create fewer emissions to begin with. If the filter begins to block a yellow warning lamp will come on telling the driver they need to drive the vehicle at the speed specified by the manufacturer (see owner’s manual) to generate the heat required to burn off the soot.

  • This could mean having to drive at speeds above 50 km/h for around 15 minutes to complete regeneration, though this is no excuse to run through red lights.

  • If the filter becomes blocked the warning lamp will turn red which means it’s time to see your car dealer or mechanic.

  • Regeneration shouldn’t be as much as an issue with petrol engines as they produce less sooty emissions than diesels and run hotter in slower traffic.