New research shows the negative side of particulate filters in modern cars

Modern cars with internal combustion engines don’t always sound very good. The sound is partially dampened by turbos, but soot filters in exhaust systems also dampen the sound. These particulate filters are designed to reduce emissions levels, but a new study shows these filters aren’t perfect.

Particulate filters used to be mainly in diesel cars, but nowadays they are also in cars with petrol engines. So also inside PerformanceCars like the Porsche 911 Turbo S. The German car takes off like a rocket, but the sound lags a bit behind in terms of intensity. Turbos and filters are also to blame here. But do these filters actually help against soot emissions?

What exactly do particle filters do?

Exhaust gases are passed through the particulate filter, also known as the particle filter, where small particles are trapped and accumulate. Exhaust gases can escape through small cracks and continue on their way to the tailpipes.

The filters are not only mandatory for diesel engines, but also for petrol engines for several years. If a filter is full, the accumulated soot is burned. The car does this by temporarily injecting more fuel to raise the temperature of the exhaust gases. This process turns out to be much more polluting than expected.

Studies show that small particles slip through

British researchers from a university in Birmingham have researched the soot filters. In the data used, the researchers saw that the number of larger soot particles in London fell by 81 percent between 2014 and 2021. This is because filters became mandatory during this period. It’s not for nothing that cars sound less sharp these days.

However, the soot filters do not always work so well. While the filters manage to keep larger soot particles out, very fine particles still seem to be able to find their way. The number of small soot particles fell by only 26 percent during this period. This applies to pieces of soot that are smaller than a hundred nanometers. That’s a ten-thousandth of a millimeter. In fact, the number of soot particles smaller than thirty nanometers did not decrease at all.

“High concentrations of very small soot particles are becoming a permanent problem. The number of electric cars will have to increase proportionally. Additionally, additional measures are needed to limit emissions from diesel vehicles,” Professor Roy Harrison said after the study.