What is a petrol particulate filter and how does it work?
Diesel cars have been fitted with particulate filters for years, and now petrol cars are getting them as well in order to reduce pollution...
A growing number of petrol cars are being fitted with petrol particulate filters – also called gasoline particulate filters – in order to meet the latest stringent emissions limits. According to Volkswagen, the particulate emissions of some of its petrol models can be reduced by up to 95% by fitting a filter to the exhaust system.
Why are petrol particulate filters being introduced?
Petrol-engined cars have been subject to particulate emissions limits since the EU5 standard was introduced in 2009. The permissible limits were reduced ten-fold in September 2018 when EU6c legislation came into force. This brought the NOx limit down to 60mg/km for new petrol cars, below the 80mg/km limit for diesels. This means particulates are virtually eliminated from exhaust emissions, including nanoparticles, which are considered to be more harmful than larger particulates.
How does a petrol particulate filter work?
The system on Volkswagen Group cars, such as the Volkswagen Up GTI and models using the 1.4 TSI engine, newer 1.5 TSI and 2.0-litre petrol, works like a three-way catalytic converter, through which exhaust gases flow after exiting the engine and going towards the exhaust pipe.
The unit is situated just behind the engine, close to the turbocharger. This helps it warm up quickly – useful because it needs to be hot to work effectively.
Exhaust gases are forced through the filter, wherein the trapped unwanted hydrocarbons (HC), nitrous oxides (NOx) and carbon monoxide (CO) particulates are heated up and reduced to small amounts of carbon dioxide (CO2), nitrogen and water.
After leaving the filter, the gases pass through a second, conventional three-way catalytic converter mounted beneath the floor. This ensures the tailpipe exhaust complies with the latest level of EU6c emissions standards even when the engine is working flat out.
Which cars are fitted with petrol particulate filters?
Volkswagen committed to introducing particulate filters to its petrol models in 2016, having started with the Tiguan and Up. Petrol-engined versions of the various Ford, Mercedes-Benz and Porsche models, including the Mustang, S-Class and Macan, also have particulate filters.
The technology has also been introduced on most new petrol models introduced since September 2018 in order to meet the EU6c requirements.
Do petrol particulate filters need maintenance?
According to manufacturers, cars with petrol particulate filters shouldn’t need to regularly be driven at higher speeds for short periods to stop them getting clogged up with soot, unlike with diesels.
Petrol particulate filters aren’t prone to getting blocked up like diesel particulate filters because petrol engines heat up quicker and run hotter than diesel engines, so more of the soot that’s collected in the filter is burnt off. Additionally, Porsche says that the electronic control units in its cars will detect when soot particles occasionally need to be burned off and increase the exhaust gas temperature to do this.
Should I buy a car with a petrol particulate filter?
Petrol cars fitted with particulate filters are among the cleanest cars on sale, and there's no evidence so far that the filters will suffer the problems that have proved costly for a small proportion of diesel car owners.
Coming soon: new cars for 2019
Planning to buy a new car? Think you know what you want? Well, before you sign on the dotted line, make sure you read our round-up of the models coming soon; there are lots that could be worth waiting for, whether you're after something small, something spacious or something stylish.
In this guide we look at every class of car. And we not only reveal what's coming when, but what's special about each of the newcomers.
Small and family cars
On sale Autumn
The Volkswagen Golf is one of the best-selling cars in the UK, with more than 26,000 finding homes in the first five months of 2019, even though the current version will soon be replaced.
Don’t expect a revolution when it comes to the looks; the new, eighth-generation Golf will feature sharper creases to bring it into line with the latest Polo, but it will still be instantly recognisable, and the three-door, five-door and estate bodystyles are all expected to continue.
The new Golf will be based on the same underpinnings, too, but its front and rear axles are likely to be farther apart to liberate more rear leg room. The boot is also expected to grow, although it’s still unlikely to outclass the gargantuan Skoda Octavia in this area.
We’ve become used to seeing modern cars launched with far fewer interior switches than their predecessors, and this will also be the case with the new Golf. In fact, on high-end versions there will be almost no switches at all, with Volkswagen bosses describing the car’s interior as a “total digital environment”.
The 1.5-litre turbo petrol engine we currently recommend will be carried over as part of an expanded range of petrol and diesel units. Many of the petrols will feature 48V mild hybrid tech to both improve acceleration and cut emissions. There will also be a new 1.0-litre petrol and 1.5-litre and 2.0-litre diesels.
The next Golf GTI hot hatch, due in 2020, will use a revised version of today’s 2.0-litre petrol unit with the mild hybrid tech, making around 260bhp, while the e-Golf will be discontinued ahead of the electric ID hatchback’s arrival.
As for tech, the Golf will be permanently connected to the internet, thanks to an eSIM that will allow it to show advanced 3D sat-nav mapping, always find the strongest radio signal and let its engine coast in the run-up to junctions or when you’re heading downhill.
Prices for the Golf are expected to shift significantly upwards, beyond the £18,795 asked for today’s cheapest five-door model.
On sale Late 2019
Don't panic: the new Fiat 500 is almost certain to look much like the current one and offer a range of head-turning colours and interior finishes similar to that which makes it so popular among fashion-conscious buyers today.
Instead, interest in the new model lies in whether Fiat can complement its cutesy design with a much-improved driving experience – something that it badly needs, seen in its current two-star What Car? rating.
From what we know so far, the most headline-grabbing changes will be the introduction of mild hybrid tech – alongside conventional petrol engines – and the introduction of electric and estate variants.
The mild hybrid will use an electric set-up to boost fuel economy and therefore lower emissions, while the electric 500e will arrive from 2020, with the estate, likely to be called the Giardiniera, to follow.
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