* 2.0L Turbocharged 4-cylinder: This was the standard engine for the TT Coupe and Roadster models, producing 200 horsepower.
* 3.2L Naturally Aspirated 6-cylinder: This was the engine option for the TT Quattro model, producing 250 horsepower.
Therefore, the base engine size for the 2006 Audi TT is 2.0L.