August 29, 2019

Innovative twin dosing reduces NOx emissions by
approx. 80 percent
Double injection of AdBlue into the exhaust system enables
significant reduction of nitrogen oxides
→ First use of the new technology in the Passat 2.0 TDI Evo1,
later also in the new Golf2
→

Wolfsburg (Germany) – Since 2018, only SCR exhaust gas treatment
systems have been used in Volkswagen models with diesel engines. SCR
(selective catalytic reduction) technology significantly reduces nitrogen
oxides in the exhaust gas. Volkswagen has now developed the next
evolutionary stage of the SCR system – so-called “twin dosing”. Adblue is
injected 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
110 kW (150 PS), which already meets the technical requirements of the
future Euro 6d emission standard as a result.
Current
RDE
(real
driving
emissions) measurements confirm
Volkswagen's type approval: in the
new 2.0 TDI Evo with twin dosing,
NOX levels are reduced by around
80 percent compared to the
previous generation of the
respective models.

Press Contact
Volkswagen Communications
Product Communications
Jens Bobsien

Twindosing - double SCR injection

Volkswagen will now gradually
introduce the new technology to all models with 2.0 TDI Evo engines.
Following the 2.0 TDI Evo with 110 kW (150 PS) currently fitted in the
Passat, the new Golf – soon to see its world premiere – will likewise feature
twin dosing in all TDI variants.

Head of Communications Innovation,
Technology & Design
Tel.: +49 5361 9-32529
jens.bobsien@volkswagen.de
Product Communications
Christian Tinney
Communications Innovation &

The twin dosing process requires a second SCR catalytic converter which is
located in the underbody of the vehicle. Since the distance to the engine is
greater, the exhaust temperature upstream of the second catalytic
converter can be as much as 100°C lower. This expands the window for
aftertreatment of exhaust gases: even at exhaust gas temperatures close to
the engine of +500°C, the system is still able to achieve very high conversion
rates. In addition, a blocking catalytic converter downstream of the SCR
system prevents excess ammonia slip.
The innovative twin dosing process compensates for a system-based
disadvantage of diesel engines. Modern diesel engines emit less CO2 than
No. 277/2019

Technology
Tel.: +49 5361 986214
christian.tinney@volkswagen.de

More at
volkswagen-newsroom.com

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 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, thereby forming nitrogen oxides.
Ammonia is needed to reduce the nitrogen oxides produced in diesel
engines. It is injected as an aqueous reducing agent (AdBlue) via a dosing
module into the exhaust gas upstream of an SCR catalytic converter. Here,
the solution evaporates; the reducing agent is split, combining with steam
to form ammonia. In the SCR catalytic converter, the ammonia (NH3) then
reacts on a special coating with the nitrogen oxides (NOx) to form water and
harmless nitrogen (N2) – the main constituent of the air we breathe.
In existing exhaust gas treatment systems, a close-coupled SCR catalyst is
located between the turbocharger, the diesel oxidation catalytic converter –
which converts uncombusted hydrocarbons – and the flexible connecting
piece to the silencer pipe. The SCR coating is applied to the honeycomb
structure of the diesel particulate filter, thereby enabling a single
component to perform several functions. The close-coupled arrangement
means that the exhaust gas temperatures required for high conversion rates
can be achieved quickly after a cold start – the ideal range for conversion
rates of more than 90 percent is between +220°C and +350°C. These
conditions are met in many operating situations.
Conversion rates do not drop above +350°C – thanks to twin dosing-system.
Temperatures at this level occur for example when driving at high speeds on
the motorway, at high engine speeds over prolonged periods of time and
when driving uphill, especially if the vehicle is fully loaded or towing a trailer.
1)

2)

Passat Variant 2.0 TDI Evo 110 kW / 150 PS (NEFZ) fuel consumption in
l/100 km: urban 4,5 / extra-urban 3,6 / combined 4,0; CO2-emissions
combined
in
g/km:
104;
efficiency
class:
A+
Passat Limousine 2.0 TDI Evo 110 kW / 150 PS (NEFZ) fuel consumption in
l/100 km: urban 4,5 / extra-urban 3,5 / combined 3,9; CO2-emissions in
g/km: 101; efficiency class: A+

The vehicle has not yet gone on sale.

About the Volkswagen brand:
Volkswagen Passenger Cars operates in more than 150 markets worldwide and produces vehicles at more
than 50 locations in 14 countries. In 2018, Volkswagen produced around 6.2 million vehicles, including
bestsellers such as the Golf, Tiguan, Jetta and Passat. Volkswagen has a current workforce of 195,878
employees around the globe. Added to this are more than 10, 000 dealerships with 86,000 employees.
Volkswagen is forging ahead consistently with the further development of automobile production. Electric
mobility, smart mobility and digital transformation of the brand are the key strategic issues for the future.

No. 277/2019

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