6MT vs Dual Clutch

[Minn19]

Yes, this is my M5. It has the same DCT as the F8X, which I also used to own, which was also the same DCT in E9X M3.

I think many of you are confusing "crisp/quick" with "smooth".

When slowing down to a stop light, I can shift from 3rd to 2nd and modulate the clutch in such a way that you practically cannot feel any jerkiness. Then I put it in neutral for the last 5-6 mph (or 1st). In my M5, you do the same, there is always the downshift to 2nd which is clunky and jerky.

I'll give you another example (try this yourself). Say that you have a stop sign or a red light up on a hill. You are traveling towards the hill and eventually come to a stop, car's nose is pointing upwards. If you come to a full stop and wait 1-2 seconds, gyroscope in the car will detect the steep incline and put it in 1st. All good. HOWEVER, if you dont come to a stop but slowly move (i.e the creep mode), car will stay in 2nd and suddenly it will want to move to 1st. Then you will feel this weird motion of someone pushing you from the back. Not smooth at all.

Bottom line is, I can control the clutch slippage with my left foot. Depending on my speed, road conditions, throttle mode, etc, I can intuitively cater the use of clutch for my own unique situation and can control whether I want a very smooth shift or very quick/sporty shift. Yes I can probably wear the clutch a bit more, but the fact remains. If I want I can have my downshift take slightly longer by modulating the clutch resulting in a smoother operation. The computer on the other hand cannot do that. This is also why true AI will never work. One simple reason, you cannot teach computers instincts. What makes us human is our instincts and our ability to make unpredictable decisions.

Lastly, another thing that annoys the crap out of me in my DCT is the stupid throttle sensitivity. Now this may be more to do with the turbos rather than the DCT, but it adds to the overall driving experience being very poor in day to day driving. Basically if you are traveling on 1st gear and suddenly move your foot of the throttle car and lightly tap back on will jerk back and forth. It will do this so badly that you think something is wrong. In contrary, do the same in GT350, even in the drag strip mode, car doesnt suddenly jerk back and forth. Its butter smooth. This may be due to the pretensioned turbos, its a side effect of anti lag basically.

I don't think I've put as much thought into as you have. ;) I also don't have my DCT M4 to compare with anymore either so there is that.

I only had the throttle sensitivity problem in sport plus mode, which is why I rarely used it.

Also, I could've sworn the DCT unit is different from the E9X to the F10/F8X DCT units.

I'll leave it at this, I didn't have any issues with the DCT and found it to be an awesome transmission (especially for the track). The only problem I had with it was that it got boring and lacked the involvement of the MT.

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[Cobra6185]

Finally got a chance to test drive a GT350 today. Haven't driven stick in about 8 years. I prefer my DCT M4 but the 6MT wasn't bad at all..

 

[Norm Peterson]

I'll leave it at this, I didn't have any issues with the DCT and found it to be an awesome transmission (especially for the track).

Isn't 'working especially well at the track' where the DCT's principal benefit lies?

How good is it at the other end of the driving spectrum, chugging along in traffic at speeds that occasionally drop below whatever corresponds to idle rpm in 1st gear? With a clutch car, you have a clutch pedal available to allow coasting at very low speeds (and by occasionally and briefly re-engaging it at least partially with little or no throttle, keep such coasting from ending up in a full stop). With an automatic you can ride the brake pedal (something that I absolutely abhor doing, pressing on the 'stop' pedal in order to go). How does a DCT cope with this situation?


Norm

 

[ForTehNguyen]

DCT have low speed smoothness issues, which is why acura put a torque converter on the early gears of its 9 speed DCT. Require a lot more maintenance as well.

 

[Minn19]

Isn't 'working especially well at the track' where the DCT's principal benefit lies?

How good is it at the other end of the driving spectrum, chugging along in traffic at speeds that occasionally drop below whatever corresponds to idle rpm in 1st gear? With a clutch car, you have a clutch pedal available to allow coasting at very low speeds (and by occasionally and briefly re-engaging it at least partially with little or no throttle, keep such coasting from ending up in a full stop). With an automatic you can ride the brake pedal (something that I absolutely abhor doing, pressing on the 'stop' pedal in order to go). How does a DCT cope with this situation?


Norm

I don't know the mechanics of it, but I believe it has the ability to coast in those situations. It's kind of odd from a start, you can feel the DCT riding/engaging the clutch like a manual so you can feather the throttle to get a smooth start. Once in a blue moon it would get jerky, but that was usually because of something I did. I drove it a lot in stop and go commuting and had no issues.

I liked the no creep unlike a traditional auto and the ability to feather the throttle to do what you suggested (not riding the brake pedal) in low speed situations. I hope that helps.

 

[Mike02z]

I honestly don't care how good a DCT shifts. A lot of the fun for me is rowing through the gears. If the Manual ever does go away, I'll stop buying fun cars. You can have my manual when you pry it from my cold, dead hands.

 

[Stuntman]

^agreed. And when coming to a stop, you can always drop the car into neutral and smoothly coast to a stop, then grab 1st gear while you're waiting for the light to turn green -like a manual.

 

[Hack]

I've driven a few cars with a DCT and they are not for me. I rented a GT3 and F430 on a track and they were fast but not nearly as fun to drive as my GT350. I also drove an M4 with the DCT and it worked fine and the car was fast, but I have no interest in buying it.

I dislike any form of automatic.

 

[Stuntman]

I've driven a few cars with a DCT and they are not for me. I rented a GT3 and F430 on a track and they were fast but not nearly as fun to drive as my GT350. I also drove an M4 with the DCT and it worked fine and the car was fast, but I have no interest in buying it.

I dislike any form of automatic.

F430's have a single clutch, not a DCT.

I probably shouldn't care, but it's a bit derogatory and inaccurate to call SMG, PDK, DCT,... transmissions "automatics" when they have all of the internal components of a manual transmission that is actuated by electronics, while an "automatic" transmission is a completely different design.

I guess almost all professional racing is with "automatics" then...

 

[Minn19]

F430's have a single clutch, not a DCT.

I probably shouldn't care, but it's a bit derogatory and inaccurate to call SMG, PDK, DCT,... transmissions "automatics" when they have all of the internal components of a manual transmission that is actuated by electronics, while an "automatic" transmission is a completely different design.

I guess almost all professional racing is with "automatics" then...

I always called it a quirky automatic. I remember these fights/long threads on the BMW forum about what to call them. I guess I consider it an automatic, the highest version of one, but it is what is is.

 

[Mike02z]

Call them what you will. If the car does not have 3 pedals, it's not a "manual" to me.

 

[mdmoore23]

I have to make this thread. Sorry, I do and it's not what you think it is.

I have owned DCT cars for the last 10 years. My previous 6MT was a 335i from 2006 or 2007 I believe. I have always thought how "advanced" and how "smooth" DCT transmissions were.

While it is true that in terms of sheer acceleration, they are great, ever since I got my GT350, I realize more and more that they are so bad in city driving, so clunky and uncomfortable. Not to mention in snow and ice. Nothing and I mean this from the bottom of my heart, beats a traditional clutch pedal and a driver's ability to modulate clutch gently. In stop and go traffic, slowing the car down, down shifting, managing slippery conditions, a computer cannot replace human instincts and the third pedal.

Now a traditional torque converter based auto might be something else, but that has its own problems in terms of delay in upshifts and downshifts (in manual mode). The so called 911 PDK killer GM auto transmission in Z06 was so bad, I laughed when I drove it (in manual mode).

I think nothing beats a manual transmission.

hy bother with a DCT when they've co-engineered a new 10 speed auto with GM? Torque converter autos are good enough now to rival DCT shifting without the cons of clunkiness and poor daily driving characteristics. The ZF 8 speed in my Hellcat is borderline perfect. That transmission is awesome! Google it and see how many manufacturers are using it today. There is no delay on upshifts or downshift to gripe about. Paddles are responsive and it Rev matches downshift. And I've heard the 10 speed is good too. Just listen to a video of the ZL1 shifting.

 

[Minn19]

hy bother with a DCT when they've co-engineered a new 10 speed auto with GM? Torque converter autos are good enough now to rival DCT shifting without the cons of clunkiness and poor daily driving characteristics. The ZF 8 speed in my Hellcat is borderline perfect. That transmission is awesome! Google it and see how many manufacturers are using it today. There is no delay on upshifts or downshift to gripe about. Paddles are responsive and it Rev matches downshift. And I've heard the 10 speed is good too. Just listen to a video of the ZL1 shifting.

I had the same ZF8 in a few of my BMW's and my wife's current 428. While it is a very very good automatic, it still wasn't as good or quick as the DCT and noticeably so.

I have no idea about the new 10 speed auto, it might be just as fast.

 

[Stuntman]

How many of you guys who dislike DCTs have driven a PDK, 458/Speciale, McLaren (12C, 570, 650, 675)? I think these are quite a step above BMW's programming of the Getrags, and from a stop I think they're just as smooth as an "automatic".

 

[mdmoore23]

I have to make this thread. Sorry, I do and it's not what you think it is.

I have owned DCT cars for the last 10 years. My previous 6MT was a 335i from 2006 or 2007 I believe. I have always thought how "advanced" and how "smooth" DCT transmissions were.

While it is true that in terms of sheer acceleration, they are great, ever since I got my GT350, I realize more and more that they are so bad in city driving, so clunky and uncomfortable. Not to mention in snow and ice. Nothing and I mean this from the bottom of my heart, beats a traditional clutch pedal and a driver's ability to modulate clutch gently. In stop and go traffic, slowing the car down, down shifting, managing slippery conditions, a computer cannot replace human instincts and the third pedal.

Now a traditional torque converter based auto might be something else, but that has its own problems in terms of delay in upshifts and downshifts (in manual mode). The so called 911 PDK killer GM auto transmission in Z06 was so bad, I laughed when I drove it (in manual mode).

I think nothing beats a manual transmission.

Why bother with a DCT when they've co-engineered a new 10 speed auto with GM? Torque converter autos are good enough now to rival DCT shifting without the cons of clunkiness and poor daily driving characteristics. The ZF 8 speed in my Hellcat is borderline perfect. That transmission is awesome! Google it and see how many manufacturers are using it today. There is no delay on upshifts or downshift to gripe about. Paddles are responsive and it Rev matches downshift. And I've heard the 10 speed is good too. Just listen to a video of the ZL1 shifting.

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