C&D 2011 BMW 135i DCT - First Drive Review
Join Date: Dec 2001
A dual-clutch automated manual brings virility to BMW’s potent 135i
BMW’s 135i coupe and convertible might not look much different for 2011, but with a new turbocharged inline-six engine and a newly available dual-clutch automated manual transmission, the 2011 135i certainly feels different. We came to this conclusion following our first opportunity to sample the latest 135i on the roads around New Jersey Motorsports Park, as well as on its Lightning Raceway track, during BMW’s recent 2011 model roll out.
On paper, the differences are slight. Cosmetic and interior changes are more or less limited to reshuffled options packages. Although the single-turbo N55 replaces the award-winning N54 twin-turbo motor in all 135s, its output figures are technically the same as those of the N54: 300 hp and 300 lb-ft of torque, with peak torque now occurring 200 rpm sooner. (We say “technically the same” because it has been our longtime suspicion that the N54 is actually 20 to 30 hp more powerful than BMW claims, and it’s possible that the N55’s ratings are not similarly underestimated.) The dual-clutch transmission is the same DCT-branded gearbox offered in the Z4. It replaces the 135i’s optional six-speed automatic and costs $200 more; a six-speed manual is still the standard transmission option. The 128i continues with the choice of six-speed manual or traditional automatic.
Credit the Transmission More Than the Engine
The close-ratio, seven-speed dual-clutch gearbox feels far better than the conventional autobox it replaces, which itself was a swell-enough automatic. By virtue of its conventionality, however, the auto couldn’t deliver an almost uninterrupted stream of torque to the rear wheels as does the DCT. The outgoing slushbox was also hamstrung by its artful but clumsy to use optional shift “paddles,” which required a push for downshifts and a pull for upshifts. The DCT comes with honest-to-goodness, pull-only steering-wheel paddles–downshift on the left, upshift on the right–that make far easier work of changing gears during high-intensity driving.
We generally prefer the driver involvement of traditional manual transmissions, especially when they’re as good as the ones offered on most BMW models. In the case of the 135i, the fitment of the DCT might close the preference gap for some and will likely improve acceleration times. The difference in character between the N54 and N55 seems minimal, at least in this application, but it’s the DCT’s quick shifts that improve the experience, keeping the engine in the power better than the automatic was able to. We expect the DCT will bring 0-to-60-mph times down by 0.1 or 0.2 second compared with manual-equipped 135s, into the mid-four-second range. The quickest 135i we’ve tested, a manual-equipped coupe, took 4.7 seconds to reach 60, and a three-pedal convertible completed the task in 4.9.
As expected, the convertible feels heavier and slightly less nimble in spirited driving, although we could hardly characterize it as sloppy. We don’t expect too many 135i convertible owners to head to the track in their cars, so that’s a relatively moot point. Convertible buyers want convertibles, and this one continues to require few sacrifices as compared with the coupe.
So the good news is that the switch from twin- to single-turbo six hasn’t affected the 135i’s character noticeably. As long as BMW’s output claims are on the up and up, performance should improve, too—we’ll wait for a formal test session to confirm that. Buyers who would have chosen the automatic last year will be happy with the dual-clutch upgrade. The better news is that the three-pedal manual is still available—at least for now. Let’s keep it that way, okay, BMW?
Source - http://www.caranddriver.com/reviews/...t_drive_review