View Single Post
      06-20-2012, 09:59 PM   #22
GTR-Dad's Avatar

Drives: 2012 M5 - DCT
Join Date: Oct 2007
Location: Beaumont, AB

iTrader: (0)

DCT vs 6MT is far from a black and white issue, even for a keen driver who revels in executing flawless shifts in a 'proper' manual. You know, the kind with a 3rd pedal and gear selector that YOU actuate...

Here's an excerpt from a review I wrote describing my initial impressions of my M5. This is dangerously close to quoting myself, which I find kind of, well, narcissistic, but it illustrates the tension I experience on this topic.

The M5 is spec'd with a 7 speed dual clutch automated manual gearbox rather than a 'proper' manual with a clutch and gear shift. This choice represents the most difficult part of ordering the car. Every other car I've owned has required me to take a more active role in changing gears, and it was really out of respect for the BMW engineers' design intent that I decided to try the dual clutch box. From where I sit right now, I think I made the right choice, but I've got a bit of learning to do before I can claim to drive this car the way I want to on the race track.

Efficiency mode in either auto or sequential configuration does a great job of minimizing fuel consumption and softening the edge that comes with more assertive settings. Comfortable, smooth, and relaxed are the correct descriptive words. I didn't engage efficiency shift mode very much.

Sport Plus shift mode promises the ultimate response and performance experience. Right? That's where I started and it certainly wakes the car up! Shifts are crisp, solid, and perhaps even a bit harsh. (I might have been more decisive about shift harshness if I hadn't driven an Aventador on the track a couple of months ago. Corsa mode, Lamborgini's version of Sport Plus, under WOT acceleration is a recipe for whiplash. Fun, but worryingly hard on the drive train and occupants alike.) I didn't use Sport Plus in auto mode as the shift points were significantly in excess of run in rev limits, but I think I'll be manually shifting this car most of the time anyhow. My only real beef with Sport Plus manual is with down shifting. Although there's an appropriate throttle blip to match revs, when the clutch reengages, engine braking is significant enough to upset the car, particularly in trail braking / late downshifting situations. A good heel/toe downshift in a proper manual is smoother and provides a more natural opportunity to modulate engine braking with a bit of maintenance throttle. I expect I'll learn this skill with the dual clutch setup, but not this week.

Sport shifting speeds up the gear changes substantially compared to efficiency, and remains decently smooth. Smooth enough to keep your passenger's head from jerking forward during shifts, and smooth enough to keep 'shock loading' out of the gear train's load history. In automatic configuration, the shift map is remarkably sympathetic with enthusiastic and spirited driving. If you get caught needing to attack a road in this mode, you'll find that crisp shifts at reasonable but assertive revs will get the job done. If you lift, the car will hold the gear anticipating reapplication of the throttle and will upshift only when moderate throttle is applied. Downshifts are a little slower than Sport Plus, but the payback is that engine braking is less obtrusive and the shift is smoother. Almost as smooth as I'd do it myself - on a good day. Of course not every downshift in a proper manual is perfect, and I'd never want to go up against the dual clutch system in a contest of consistency, but then again, striving for the perfect downshift - every time- is part of the joy of driving and when the car does it for you, something is lost. (Reflective pause.....)