BMW launched the 1-series just a few years ago, but the company’s smallest current model isn’t immune to the engine update that is spreading across the BMW lineup for the 2011 model year. Accordingly, the ’11 135i is now offered with the new single-turbocharged “N55” six-cylinder engine, which features BMW’s Valvetronic technology and direct fuel injection. Even more notable is the 135i’s new seven-speed dual-clutch transmission (a.k.a. DCT), the first application of a DCT with the N55 in-line six.
We drove a 135i convertible with the new powertrain on the track at New Jersey Motorsports Park and came away highly impressed. The seven-speed DCT gearbox rips off very quick, thrusty upshifts in manual mode while the engine begs for more. Or you can put the gear lever in Sport mode and let the transmission do its thing — which it does almost telepathically — while you concentrate on the other controls and transferring the nimble car’s weight from side to side, turning in fast laps the whole time. (And yes, we do realize that many hard-core — and perhaps insecure — BMW fans would be ashamed to own a 1-series convertible, let alone drive it on a racetrack.)
On public roads in southern Jersey, the 135i’s new dual-clutch gearbox continues to nail superquick upshifts. Even more impressive is how quickly the transmission jumps down to lower gears. For instance, if you’re cruising at about 50 mph in seventh (top) gear and drop the hammer without using the gas pedal’s kickdown switch, the gearbox will shift almost instantly to third. If you tap the kickdown button, you’ll get second gear, whether you’re in full-automatic or Sport mode. If you care to shift for yourself (as we usually do), you can use the steering-wheel-mounted paddles. Happily, these are proper left-for-downshift, right-for-upshift paddles, unlike those found in the new Z4 sDrive35is . Enthusiasts might be very unhappy, however, that the DCT won’t hold gears at the engine’s redline when you’re in manual mode, a particular weakness on the racetrack.
No matter where you’re driving, the 300-hp N55 engine reaches its 300 lb-ft torque peak 200 rpm sooner than the N54 (which had identical horsepower and torque ratings), so the lead-footed 2011 135i driver is greeted with smoother acceleration than in previous twin-turbo models, yet the urge remains plenty powerful. BMW reports that six-speed manual 1s with the new engine are capable of the same 0-to-60-mph times as last year’s model, but dual-clutch automatic cars pick up two-tenths on N54-powered slushbox models (5.0 seconds for the 2011 135i coupe with the DCT versus 5.2 seconds for the 2010 six-speed automatic coupe). Another big improvement on paper is in the mpg category, where the new engine — with the help of some revised gearing — helps stick-shift coupes improve by a whopping 3 mpg in the EPA’s combined rating (from 20 mpg overall to 23 mpg); customers averse to clutch pedals will see improvements of only 1 mpg here or there, depending on body style.
The lesson with the 135i DCT (and all BMWs with a dual-clutch automatic) is that there’s now even less shame in paying more to get your Bimmer with one less pedal. A silver lining for stick-shift fans like us is that BMW has decided to charge $200 more for the DCT option in the 135i on top of last year’s already pricey $1375 automatic option. The 2011 135i will go on sale by the end of May for a base price identical to that of the outgoing 2010 model: $37,800 for the coupe and $42,100 for the convertible.