VW Debuts Dual SCR Diesel Emissions Tech

Volkswagen AG is introducing a twin-dosing selective catalytic reduction (SCR) technology that promises to reduce nitrogen oxide emissions in diesel-powered cars by as much as 80%.

The system is launching this summer in Europe in the Passat midsize car with a 2.0-liter 4-cylinder “TDI Evo” diesel engine (pictured). VW says the technology meets updated Euro 6 emission standards. Other vehicles equipped with the engine will be phased in later, starting with the all-new 2020 Golf small car that bows later this year.

The system features two SCR catalytic converters arranged in series with Adblue urea injected at two points upstream of the devices. The dual setup allows the devices to work more effectively by treating emissions at different temperatures as they get further away from the engine, according to the carmaker.

VW says real world testing of the new Passat and Golf diesels with twin-dosing demonstrated an 80% reduction in NOx emissions versus previous generation cars with a single SCR.

SCR reduces NOx by injecting a urea-water solution, standardized in Europe as AdBlue, into the exhaust stream. Most carmakers employ the technology.

VW, which had been using less-expensive lean NOx traps, began switching to SCR shortly after the company’s diesel emission cheating scandal came to light in September 2015. The company has used SCR in all diesel-powered models since 2018.

VW admitted to using special software to allow its diesel engines to pass emission certification but allow NOx emissions in real-world conditions to zoom as much as 40 times over the limit. To date, the scandal has cost VW more than €23 billion ($26 billion) in fines, engine upgrades, vehicle buybacks and environmental restitution.