The 2.0 TDI engine is the new optional powerplant for the A3, Audi's small-car offering that first arrived here for 2006. The TDI certainly makes a lot more sense than the 3.2-liter V-6 (which has been dropped) as the alternative engine offering in this car, particularly as the latest version of the A3's standard, 2.0-liter turbo four boasts the drivability of a V-6. Indeed, only a small fraction of buyers chose the V-6, but Audi expects the TDI -- which just went on sale in December -- to account for 40 percent of A3 sales.
While the A3's gasoline engine comes with a choice of transmissions and front- or four-wheel drive, the TDI is offered exclusively with the six-speed S Tronic dual-clutch automatic and front-wheel drive. The latter might seem strange given that Audi's identity is so strongly wrapped up in Quattro all-wheel-drive, but most TDI buyers are going to be looking for maximum fuel economy. And the A3 TDI does deliver some standout numbers, particularly its 42 mpg EPA highway rating, which is the best of any premium-nameplate car, better even the Lexus HS250 hybrid -- although the Lexus hybrid easily tops the Audi's 30 mpg city figure. A more direct comparison is with the gasoline-powered A3. Similarly configured (with S Tronic and front-wheel drive), the TDI crushes the 2.0T's 22/28 mpg ratings. Considering that Audi charges only $1200 extra for the diesel, the TDI makes a pretty compelling case on economics alone. (Of course, the truly hardcore green eyeshade type wouldn't even shop in an Audi store; he/she would be down at the VW dealer, haggling mercilessly over a Golf TDI, which has the same powertrain.)
So, the TDI is far more economical and not much more expensive than a standard A3, but how does it drive? The short answer is: much better than the numbers suggest. Like all diesel engines, the TDI is relatively short on horsepower (140 hp) but long on torque (236 lb-ft) compared to its gasoline sibling (200 hp, 207 lb-ft). The low power figure explains the relatively long factory-quoted 0-to-60 mph time of 9.1 seconds (versus a brisk 6.9 seconds for the gasoline version). But the TDI actually feels much quicker in real world driving, because of the wealth of torque on tap at low engine speeds -- as low as 1750 rpm. So the relatively light throttle openings you use in most everyday driving produce lots of thrust.
Normally, sending a lot of torque through the front wheels is a recipe for torque steer, but any steering wheel twitchiness is well suppressed. Without the benefit of Quattro, pulling out onto a busy street can briefly overwhelm the front tires and call upon the services of the traction control system, but it's not much of an issue. The only negative with regard to driveability is the TDI's distinct diesel engine note, which is always present.