Let's get caught up on history, shall we?
As recently as 2001, the quattro GmbH-built Audi B5 RS 4 Avant trim was the benchmark for Audi performance. The RS 4 packed a 375 hp Cosworth-built 2.7L biturbo V6—Audi’s most powerful production engine.
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Audi leadership decided that it was time to explore a sports car to rival the outright performance of foes from BMW, Porsche, and Mercedes-Benz—not to mention their own RS 4…wagon.
With start of Audi R8 development four years away and production six years away, the only sports car that Audi had in its stable was the Mk1 TT. The transversely mounted 225 horsepower 1.8L 4-cylinder even with tuning could not match the power output levels required.
Audi may have wanted to build a sports car that could rival the 911, but they lacked a modern 5-cylinder power plant, which would have fit transversely into the TT engine bay and produce RS 4 levels of power. (Does this sound similar to the eventual formula decided upon for the quattro GmbH-developed TT RS?)
At the time, it decided that it would be too expensive to design an engine for such a limited application. So they had to work within the boundaries of what they already had in parts bins. Even the eventual TT VR6—with its 247 hp 3.2-litre engine—while a significant upgrade over the 1.8T it was not as powerful or robust as the 2.7T.
The quattro GmbH engineers started with the RS 4 underbody and drivetrain (Torsen rear differential, engine, transmission, axles, radiators, brakes and even the wheels). The engineers had to trim away 170mm from the front of the floorpan to reduce the RS 4 underbody dimensions to fit the TT body.
Once the modifications were complete, the RS 4 floorplan and drivetrain meet the upper chassis of the TT. After eight months of work, the job was complete. They had succeeded in building a sports car to rival the 911.
The best part? Nobody knew—they tested it without camoflauge on public roads! To the unknowing eye it was just another TT, but when examined the larger front cooling inlets and enlarged rear spoiler gave away that there was something more sinister here.
This TT now had the driving dynamics of the B5 RS 4 and could hit 0-100 km/h in just 4.8 seconds with a top speed of 295 km/h (183 mph.) After the engineering tests were complete, including more than 20,000 km of driving, the engineers decided against production.
There was just too much complex work involved with shortening the underbody for such a limited production vehicle.
With only one made, quattro GmbH sometimes trots it our for official functions, including—where it was captured for these photos—last year's 30 Years of quattro GmbH celebration.