Volkswagen is introducing gasoline particulate filters (GPFs) to its petrol cars as part of wider plans to improve emissions across its whole range - and it predicts reductions of particulate emissions in some models by up to 95%.
The Up GTI gained GPF technology earlier this year, but the device was already used on the manual-transmission variant of the Tiguan 1.4 TSI in Germany and is being rolled out across the brand's other cars.
Other manufacturers are equipping their own petrol cars with GPF systems. Mercedes-Benz, for example, fits it to some S-Class derivatives and, like VW, plans to roll it out more widely across its fleet. Ford has the system on its new Mustang, among other models.
Petrol cars have been subject to particulate emissions legislation since the introduction of the EU5 standard in 2009. The latest stage, EU6c, was introduced in September 2017, forcing petrol engine particulate emissions to be reduced by 10 times the previous level.
The VW particulate filter doubles as a three-way catalytic converter, the device normally fitted to petrol car exhausts to reduce emissions of toxic gases. Conventional three-way catalytic converters contain a ceramic honeycomb called a substrate, through which the exhaust gases flow on their way to the tailpipe. The substrate has a catalyst coating that greatly cuts levels of the three main toxic gases in exhaust: unburned hydrocarbons (HC), oxides of nitrogen (NOx) and carbon monoxide (CO).
Traditionally, the focus has been on larger diesel particulate matter up to 10 microns in diameter (PM10), or smaller PM2.5. By comparison, a human hair is around 70 microns in diameter. But as far back as 2001, a new threat came to light in the form of nanoparticles, which are more than 100 times smaller than a PM10.