German tuner Alpina has given the world some fantastically tweaked BMWs over the years, from the AWD B3 Biturbo to the new B7, based on the latest 7-series and shown at this year's Geneva Auto Show. Finding places in the BMW lineup that aren't covered from the factory is the tuner's specialty, and the latest from Alpina doesn't disappoint: the diesel D3 Biturbo is the 3-series we never had. Alpina released a previous version of this car last year, but they have updated it this year with better performance and efficiency.

Yanking the twin-scroll four-cylinder oil-burner from the heart of a 123d, the Germans put their arts to work and raised output for the D3 to 214hp from the stock 204hp. But like all diesels, the fun lies in the low-end rather than the high-end, and with 450Nm on tap, the fun should be in ample supply. Sprinting from rest to 100km/h in just 6.9s and topping out at 152mph, the D3 combines speed and efficiency. The performance puts the D3 in good standing with the likes of the six-cylinder 325d and 330d - while only burning the fuel required to power four cylinders.

The donor engine gets an impressive 5.2L/100km (45mpg US) in its application in the 123d. While the slightly heavier 3-series chassis and more sport-oriented tuning cut into that number somewhat, it still manages 5.4L/100km (43.5mpg US) and 143g/km CO2. Available in saloon or touring (wagon) form factors, the D3 could be one of the best daily-drivers around.