Volkswagen has launched a new range of very clean diesel engines (TDI) on the market. The TDI engines are characterised by extremely low nitrogen oxide emissions (NOx) and thus come in far below the Euro 6 NOx limit of 80 mg/km.
The Touareg V8 TDI, generating 310 kW (421 PS02), is among the first Volkswagen to feature an exhaust purification system that filters nitrogen oxides at this low level: it emits between just 10 and 20 mg/km. The NOx values were determined on the basis of RDE measurements (Real Driving Emissions03) in actual road traffic by independent specialist of Emissions Analytics.
RDE measurements defined by the European Union are extremely close to values determined in practical conditions. They supplement the new WLTP test cycle (Worldwide Harmonized Light Vehicles Test Procedure), determined on a rolling road test bed and thus in laboratory conditions, by an emissions test carried out in actual road traffic. In the case of the Touareg V8 TDI, these RDE measurement runs (which have been synchronised with the actual everyday usage of Volkswagen customers as part of a targeted procedure) were performed by Emissions Analytics in three German metropolitan areas. One test was carried out in the topographically flat federal German state of Lower Saxony while two further tests were conducted on routes in Baden-Württemberg and Bavaria that included differences in altitude.
The fact that the all-wheel drive Touareg V8 TDI reliably came in below the NOx limit in each of the tests – regardless of the route, differences in altitude and individual traffic volume – was particularly remarkable: in Lower Saxony the value totalled 10 mg/km on average, in Bavaria it amounted to 13 g/km and in Baden-Württemberg the value stood at 20 mg/km. The Volkswagen averaged an NOx value of 14 mg/km over all three measurement runs. As outlined, the limit is 80 mg/km. With this in mind, the Touareg V8 TDI not only sets important benchmarks in the SUV top tier thanks to its NOx values.
This positive result has been made possible by elements including multi-stage exhaust gas treatment featuring a very large NOx storage unit (capacity: 2.3 litres) with high-grade coating and SCR (selective catalytic reduction) with complex conditioning. The SCR catalytic converter converts NOx to harmless steam and nitrogen using AdBlue (synthetic urea solution). Like all Volkswagen TDI models, the Touareg V8 TDI also features a diesel particulate filter.
In addition, the V8 TDI operates particularly efficiently and economically as a result of several, internal engine innovations. These include a variable twin-turbo system: at part load – for instance in cities or on country roads – the V8 TDI, generating 900 Nm from as little as 1,250 rpm, generates an extremely high torque and thus largely runs at low engine speeds using only one turbocharger. This single turbocharger operation minimises both consumption and emissions. The second turbocharger only kicks into action from engine speeds over 2,200 rpm using an electrical valvelift system. The overall package generates very clean results: the Touareg V8 TDI effortlessly meets the Euro-6d-TEMP-EVAP-ISC emission standard.
The TDI flagship is not the only Volkswagen generating only a fraction of the NOx emissions permitted as the European limit: the new Golf and the current Passat with their new EA288 Evo four-cylinder model range TDI engines also fall into this sustainable category. More new models featuring TDI engines that undercut the nitrogen oxide limits by generating minimum emissions will follow.