Rather than the single-turbo setup from the 135i, the 1 Series M gets a twin-turbo six-cylinder that's good for 335 hp and 332 pounds-feet of torque. In extreme situations, the 1 Series M can enter an overboost mode to crank out 369 pounds-feet of torque (horsepower remains the same). A standard limited-slip differential can go all the way to lock, rendering maximum straight-line acceleration and better traction on slippery surfaces.

The 1 Series M comes only as a coupe, and only with a six-speed manual transmission. Citing a lower center of gravity and overall weight savings of 35 pounds, BMW will not offer the 1 Series' optional moonroof on the M car. That helps it tip the scales at just under 3,300 pounds, more than 400 pounds less than the 414-hp M3 coupe — the next rung up on BMW's M ladder. Indeed, the 1 Series M's zero-to-60 time — just 4.7 seconds, BMW says — ties a stick-shift M3's.

Visual changes include unique side mirrors that look similar to those on the M3, as well as a more aggressive front bumper and quad tailpipes. The 1 Series M's extended fenders house a track that's 2.8 inches wider up front and 1.8 inches wider in back versus the 135i. The suspension, which shares its aluminum components with the M3, supports lightweight 19-inch wheels. The car also gets cross-drilled 14.2-inch front and 13.8-inch rear brake discs.