VW ‘Twin Dosing’ Claims 80% Emissions Cut

Volkswagen is claiming an 80% reduction in NOx emissions thanks to ‘twin dosing’ with Adblue.

While many view using the additive in modern diesel exhausts as a rather inelegant methods of meeting Euro 6 emissions standards, the doubling of the treatment is claiming impressive results. For years Mazda Skyactive diesel engines managed to meet the latest emissions standard without the need for exhaust additives but even this engineering focused automaker had to turn to Adblue in its latest Mazda CX-5 crossover.

Now VW says its selective catalytic reduction (SCR) technology significantly reduces NOx in the exhaust gas by injecting selectively upstream of two SCR catalytic converters which are arranged in series. The system is used in the new Passat 2.0 TDI Evo with 147bhp, which already meets the technical requirements of the future Euro 6d emission standard as a result. The auto giant will now gradually introduce the technology to all models with 2.0 TDI Evo engines including the forthcoming Golf in all TDI variants.

VW says the twin dosing process compensates for a basic disadvantage facing diesel engines. Modern diesel engines emit less CO2 than petrol engines because diesel fuel has a higher energy density and the combustion process is more efficient. Diesel engines are also subject to special requirements, however, since fuel combustion takes place with excess air. The main constituent of air is nitrogen and this reacts with oxygen during combustion, thus forming NOx.

— Paul Myles is a seasoned automotive journalist based in London. Follow him on Twitter @Paulmyles_

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