A new complaint filed by the New York Supreme Court has cast Volkswagen's diesel emissions cheating scandal in an all-new light. Earlier today, we reported that the suit accuses former VW Group CEO Martin Winterkorn, current CEO Matthias Müller, and other key executives as being more aware of the cheating than VW's initial claims. Interestingly, the complaint also reveals the origins of VW's emissions-cheating defeat device, which is no doubt of huge interest those following this story.

The complaint, which was obtained by Road & Track, cites internal documents from VW, employee testimony, and a third-party investigation by the New York Attorney General's office.

Seemingly confirming a report that emerged this past April, Audi originally developed the defeat device software back in 1999, though not for the reason you think. The complaint says that the software was developed for Audi's 3.0-liter V6 diesel as part of an initiative to reduce the characteristically harsh, clattering noise of a diesel engine at idle.

Audi developed a piece of technology called "Pilot Injection" that injected additional fuel into the engine upon ignition, which achieved the effect of reducing noise, but increased emissions significantly. To combat this issue, Audi then developed the now-infamous defeat device software that detects when a car is undergoing emissions testing, and reduces emissions accordingly. The defeat device was internally called an "Acoustic Function," which was previously believed to be a code phrase intended to mask its true function.

The Acoustic Function was used on European-market 3.0-liter diesel V6 Audis from 2004-2008, according to the complaint. It was in 2006 when Volkswagen engineers made the fateful decision to adapt the defeat device for its Generation 1 EA189 engine, better known as the 2.0-liter TDI that's now at the heart of VW's scandal.

VW engineers apparently considered using selective catalytic reduction (SCR) technology in this engine, which uses liquid urea to reduce nitrogen oxide (NOx) emissions. The only trouble with this was that it would facilitate the need for a separate urea tank, and it would have to license the tech from Mercedes-Benz.

Instead, the engineers opted for a Lean Trap solution, which involves trapping NOx emissions in a catalytic converter and occasionally running the engine in a fuel-rich mode to break down the NOx into nitrogen and oxide. Unfortunately, this caused the engine's Soot Filters to prematurely fail due to excess buildup, which was deemed unacceptable. At this point, the engineers decided that using the "Acoustic Function" was the only way to achieve their goals, a decision apparently approved by management.

In further iterations of this engine and in Audi's 3.0-liter V6 TDI engine, the defeat device continued to be used for a variety of reasons. As you likely know at this point, a team of West Virginia researchers blew the whistle on VW, leading to all sorts of fallout, most notably, a near-$15 billion settlement with the U.S. government.

The complaint does a great job of presenting the slippery slope of the so-called Acoustic Function. Its intent was always to evade emissions testing, but an increasingly desperate Volkswagen Group leaned on it further and further, resulting in the trouble it's in today. Knowing what we know now, it seems VW's current issues were very easily avoidable.

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