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Do modern petrol vehicles emit no particulates at all?

The wide-spread application of direct injection techniques for diesel engines as from the 1990s has significantly decreased the fuel consumption of diesel cars. More recently, this direct injection technique has also been applied on petrol engines, which made them much more economical than before. These direct injection (DI) engines are made available now by most manufacturers, but the conventional engines (using ‘multipoint’ injection’) are in most case still available as well. The DI petrol engines can mostly be recognized by some typical acronyms/labels: TSI (VW/Seat/Skoda), TFSI (Audi), TCe (Renault/Dacia), DIG (Nissan), EcoBoost (Ford), THP (Citroën/Peugeot), SkyActiv-G (Mazda), GDI (Hyundai/Kia), etc. Some manufacturers have completely switched and as a result all petrol engines they offer have DI technology (e.g. BMW, Mercedes).

These DI gasoline cars consume considerably less fuel than their (non-DI) predecessors. However, the other side of the coin is that they emit particulates, which was not the case for their non-DI predecessors. In terms of mass (PM, short for ‘particulate mass’), the emission of particulates is rather small, but their emission is very high in terms of the number of particulates (PM, short for ‘particulate number’). This implies that these are particulates with a very small diameter.

When calculating Ecoscore, we currently take into account the emission of PM, but not the emissions of PN. After all, there is scientific evidence of an interrelation between emissions of PM and human health. For the moment, however, such evidence does not yet exist on the connection between the particulate diameter and their harmfulness. As a result, we (currently) do not (yet) take into account PN emissions for calculating the Ecoscore. It can be expected, though, that in the future it will be proven that these small particulates are more harmful than larger particulates, just because they can penetrate our lungs much deeper. Therefore, we cannot rule out the possibility that a future correction will take place for these DI petrol cars, taking into account the emissions of PN. Currently, however, the uncertainty is still too large to quantify this correction.

The high emissions of PN by DI petrol engines is a problem that will be dealt with by the introduction of the final phase of the Euro 6 standard, in 2017/2018. For each new DI petrol engine sold as from 2018, the emissions of PN must not exceed 6x1011 particulates per km. To comply with this standard, it can be expected that petrol vehicles will be equipped with a particulate filter, which can be very effective in significantly reducing emissions of PM and particularly PN. More information on particulate emissions (PM and PN) by DI petrol engines can be found in this publication (pdf).

last database update: 12/05/2022 - next database update planned for: 15/07/2022
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