The 1M's powertrain is the car's high point, providing ample torque at low engine speeds for a satisfying launch. This twin-turbocharged 3.0-liter inline-six-cylinder produces 335 horsepower at 5,800 rpm and 332 pounds-feet of torque at 1,500 rpm. For comparison, the 335i coupe uses a single-turbo 3.0-liter I-6 with 300 hp and 300 pounds-feet. The displacement and compression ratios are the same, but the 135i's boost pressure is 8.7 psi and the 1M's starts at 11.6 psi. I say "starts" because the 1M's turbo can up the pressure to 14.5 psi for a momentary burst of torque, rated at 370 pounds-feet.

The boost works: Nail the gas pedal at practically any speed in any gear, and after waiting a half-beat you'll feel the additional tug. I'd find this annoying if the initial power were anemic, but you get respectable response even before the surge. The low-rev torque peak that extends from 1,500 rpm all the way to 4,500 rpm continues to surprise anyone who has decades of turbocharger experience. In some ways, I prefer the 1M's ready torque to the M3 V-8's gentle rise. Despite their relatively small displacement, modern turbocharged direct-injection engines deliver the character that many larger, normally aspirated V-8s no longer do. Fantastic.

BMW didn't mess with the 135i's success: It carried over the six-speed manual's gear ratios, a good match for the 1M. The only difference is a shorter final drive ratio of 3.154 in the 1M versus the 135i's 3.077. I prefer the 1M's shifter and clutch over those of the M3, whose stick is rubbery and disconnected and whose clutch pedal presents a peculiar, nonlinear resistance through its motion. The 1M's shifter isn't my favorite, but it is an improvement, and the pedal is consistent. Borrowed from the M3, the brakes — with their 14.2-inch front and 13.8-inch rear cross-drilled rotors — do a stellar job with this lighter car.