The required levels illustrated by the example of nitrogen oxide emissions for diesel engines show how much stricter emissions legislation has become. While the Euro 3 limit from 2000 onwards was still set at 500 mg/km, only 80 mg/km have been permissible for new type approvals according to Euro 6d since 2020. Within the space of two decades, the limit has dropped to less than one sixth. The move from Euro 5 to Euro 6 alone resulted in 56 percent of the total reduction. On January 1, 2020, the Euro 6d standard superseded the previously valid Euro 6d TEMP limits for newly homologated models. Starting on January 1, 2021, all new vehicles seeking first-time approvals will have to comply with the new standards, including the strict requirements of the RDE (Real Driving Emissions) test method that targets emissions in real-world day-to-day driving. Nitrogen oxides – also referred to by their chemical abbreviation NOx – are formed when nitrogen from the air reacts with oxygen during the combustion process. The proportion of nitrogen oxide is particularly high with diesel engines because these units are designed to operate with a surplus of air.
Audi is using complex exhaust after-treatment systems to meet increasingly lower emission limits. Besides the utilization of in-engine technology, the latest gasoline and diesel engines meet the strict standards especially due to powerful and sophisticated exhaust gas purification systems. Particulate filters complement catalytic exhaust after-treatment on both TDI and TFSI engines.
What are the current challenges of exhaust gas purification?
How has Audi composed its exhaust aftertreatment system for the V6 TDI?
How does multi-stage exhaust gas purification work on TDI engines?
What are the benefits of a twin dosing system?
Twin dosing of the aqueous AdBlue urea solution is particularly effective. It takes advantage of the different conditions in various areas of the exhaust system to enhance the effectiveness of the total system, adjusted to diverse operating conditions. In this way, Audi manages to convert more than 90 percent of the nitrogen oxides across a wide temperature and operating range. Thus, twin dosing decisively contributes to meeting NOx emission limits. If the vehicle is driven in high-load conditions for a longer period of time, such as on expressways or while towing a trailer, exhaust gas temperatures in the SDPF close to the engine significantly increase, resulting in a decline of nitrogen oxide conversion rates. This provides the stage for the second injection of AdBlue upstream of the second active SCR catalyst, which is located significantly further downstream in the vehicle’s underfloor on a lower temperature level. This enables the total system to achieve high conversion rates across a wide range.
When will this V6 TDI engine be launched and in which model ranges will it be used?
Twin dosing technology in the V6 TDI will be used from the Evo 3 generation onwards. It is available in diesel engines with three liters of displacement in three different performance classes and will be installed for the new year in all models featuring this engine.
Audi emphasizes sophisticated emission reduction technology also with spark ignition (SI) engines. How does Audi reduce pollutant levels for its gasoline units?
Why do SI engines require a gasoline particulate filter?
Most of Audi’s gasoline-powered models use efficient TFSI technology, in other words gasoline direct injection engines. Turbocharging is additionally utilized in the majority of models. The objective is to effectively purify exhaust gas even in unfavorable operating ranges. The GPF reduces carbon particulate emissions caused especially when cold-starting gasoline engines by as much as 90 percent. Since 2018, all of Audi’s model ranges approved according to the Euro 6d TEMP emissions standard have been equipped with gasoline particulate filters, with two exceptions: the two-liter TFSI engine of the EA888 model range for natural gas engines such as the one used in the Audi A4 Avant g-tron and Audi A5 Sportback g-tron and the 1.5 TFSI unit in the Audi A3 Sportback 30 g-tron. These engines do not require such a filter because methane, which is also referred to as CNG (Compressed Natural Gas), burns without particulate emissions.
How does a gasoline particulate filter work?
What distinguishes Audi’s system compared to the competition?
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