BMW is earning quite the reputation of underrating its turbocharged engines. From the early days of the N54 twin-turbo inline six, through the later N55 single-turbo iteration and straight on to the 2012 M5's turbocharged V8, the crafty Bavarians have always erred on the low side with their factory-quoted power figures.
According to the dyno run that you'll see after the break, the tradition continues with BMW's new twin-scroll turbocharged four-cylinder inline N20 engine that sees duty in the 2012 328i. The mill is rated at 240 horsepower and 255 pound-feet of torque, and on at least one Dynojet dyno, a stock 328i put down 226 horses and 230 lb-ft.
Assuming that around 15 percent of power is lost to the various friction forces of the drivetrain, these results indicate that the engine is really spinning out 265 horsepower and 270 pound-feet of torque. Those are mighty impressive figures, and equal about 25 more horses than stock and at least 15 more lb-ft of torque. Suffice it to say, this engine is an extremely tempting proposition for future 3 Series owners.