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      02-07-2011, 10:37 PM   #1
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BMW exec foresees the demise of the DCT from the M3

Anyone seen this story coming out of Australian media about BMW possibly dripping the DCT from future M3's? Very interesting read, although would be much better to see a full-blown interview. Good news is that Kretschmer says they're going to keep the 6MT.

http://watoday.drive.com.au/motor-ne...207-1aj01.html
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      02-07-2011, 10:39 PM   #2
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interesting.
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      02-07-2011, 10:40 PM   #3
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I can see dropping the manual, but never some form of automated shifting (unless we're talking CVTs here)
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      02-07-2011, 10:47 PM   #4
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      02-07-2011, 10:54 PM   #5
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Very interesting report.

MT: "Rumours of my demise are premature."

In the event that a torque converter automatic replaces DCT in the next gen M3, I can only wonder how many will be running back to the timeless MT.
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      02-07-2011, 11:07 PM   #6
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Quote:
Originally Posted by Eau Rouge View Post
Very interesting report.

MT: "Rumours of my demise are premature."

In the event that a torque converter automatic replaces DCT in the next gen M3, I can only wonder how many will be running back to the timeless MT.
I think that the article is predicting the demise of the DCT rather than manual transmissions. The torque converters on high performance ATs are out of the picture once the car gets moving and some of the newer designs replace the torque converter with a multi-plate clutch. The shift times of both a "converntional' AT and the DCT are so fast that further improvements are moot. Both types of transmissions are capable of shifting much faster than human reaction time and in fact both are faster than "The Blink of an Eye" whch is about 300-400MS.

I have driven the DCT in both the 335is and the M3 and found it to be an excellent transmission but did not find it to be significantly better than a good AT. IMO a lot the appeal of the DCT is that it does not carry the stigma of being a "Slushbox"



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Last edited by captainaudio; 02-07-2011 at 11:18 PM..
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      02-07-2011, 11:12 PM   #7
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Quote:
Originally Posted by captainaudio View Post
I think that the article is predicting the demise of the DCT rather than manual transmissions. The torque converters on high performance ATs are out of the picture once the car gets moving and some of the never designs replace the torque converter with a multi-plate clutch. The shift times of both a "converntional' AT and the DCT are so fast that further improvements are moot. Both types of transmissions are capable of shifting much faster than human reaction time and in fact both are faster than "The Blink of an Eye" whch is about 300-400MS.

I have driven the DCT in both the 335is and the M3 and found it to be an excellent transmission but did not find it to be significantly better than a good AT. IMO a lot the appeal of the DCT is that it does not carry the stigma of being a "Slushbox"


CA
You make a good point. I haven't driven the IS-F but I've heard that it shifts very fast. The 7-speed auto in my car could be faster though.
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      02-07-2011, 11:14 PM   #8
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Quote:
Originally Posted by gblansten View Post
You make a good point. I haven't driven the IS-F but I've heard that it shifts very fast. The 7-speed auto in my car could be faster though.
To put exactly how fast 200 Milliseconds actually is this reaction time test may put things into perspective.

http://www.humanbenchmark.com/tests/...time/index.php

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      02-07-2011, 11:20 PM   #9
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that test is pretty cool!
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      02-07-2011, 11:22 PM   #10
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Quote:
Originally Posted by GhostRideTheWhip View Post
"The only advantage to a Dual Clutch is that it allows to you rev past 7000 RPM"

The M5 revs past 7,000k and it has 1 clutch....
I think the reference is vs automatic trans, and not SMG.

I'm sure this debate will be played out 1,000,000 times at BMW with differing opinions, from different folks and without any real decision. Will it be the M1? The 1M? The 1M coupe? The 135is? - remember that little debate?

They just interviewed someone who had that view on that day. What me worry? Time will tell.
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      02-07-2011, 11:23 PM   #11
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AMG has the answer for the best of both worlds: a conventional planetary-gear automatic with a wet clutch, rather than a torque converter. Shifts just as quick as a DCT, no power loss, much smoother in traffic, can rev higher than 7K rpm, has better reliability than DCT, weighs less, it's less complex, and costs less. It's just a novelty while something better comes along IMO. We'll see soon enough .
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      02-07-2011, 11:28 PM   #12
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Quote:
Originally Posted by elp_jc View Post
AMG has the answer for the best of both worlds: a conventional planetary-gear automatic with a wet clutch, rather than a torque converter. Shifts just as quick as a DCT, no power loss, much smoother in traffic, can rev higher than 7K rpm, has better reliability than DCT, weighs less, it's less complex, and costs less.

DCT is too damn complex, heavy, and expensive. Wait until people start changing clutches and/or electronic/hydraulic components and it'll disappear for sure. I agree it's not here to stay, but it certainly was a technological step in the direction of quicker shifting. To be DCT is a deal breaker because it hasn't been proven, and probably never will for the reasons stated above, but we all could be wrong. It'll be interesting to watch .
The newest generation ZF automatic transmissions will be available with either a torque converter or a wet clucth like the AMG unit uses. The torque converter and the wet clutch pack are only used when the car is starting fom a dead stop and both are out of the picture above about 10MPH and do not participate in the shifting of gears once the car is in motion.

If you take the reaction time test I linked a few posts back it becomes apparent that once shift times are in the 200 MS range any further improvements are imperceptable.

CA
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      02-07-2011, 11:29 PM   #13
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hahaha awesome test!
I can see where this thread is headed

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      02-07-2011, 11:35 PM   #14
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DCT is amazing
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      02-07-2011, 11:35 PM   #15
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I think that most of us will average 200-350ms. The lowest single time I ever got was 21ms but in actuality I jumped the gun and lucked out when the light turned green immedately after I did,

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      02-07-2011, 11:57 PM   #16
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BS, DCT/DSG/etc are here to stay and they are still getting better. Software is the key, I've been saying that about DCTs for some time.

Quote:
Originally Posted by captainaudio View Post
The shift times of both a "converntional' AT and the DCT are so fast that further improvements are moot. Both types of transmissions are capable of shifting much faster than human reaction time and in fact both are faster than "The Blink of an Eye" whch is about 300-400MS.
Shift times vary for DCT and vary quite a bit (up vs. down and auto vs manual mode, rpm, etc). However, under ideal circumstances upshifts can be less than 50 ms. No automatics are that fast. The fastest auto I have heard of is in the Lexus IS-F and IIRC that box can shift in 200ms.

The transmissions continue to get faster and better and although there is not a lot of room left in terms of pure speed of the fastest shifts there is much room to continue DCT/DSG boxes.

Also reaction times and shift times are VERY different. A reaction time is based on a somewhat random stimulus. A shift is very carefully planed and orchestrated to occur just when one wants, absolutely no random stimulus. It's basically only coincidence that a typical reaction time and typical shift time are similar.
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      02-08-2011, 12:06 AM   #17
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Quote:
Originally Posted by swamp2 View Post
BS, DCT/DSG/etc are here to stay and they are still getting better. Software is the key, I've been saying that about DCTs for some time.



Shift times vary for DCT and vary quite a bit (up vs. down and auto vs manual mode, rpm, etc). However, under ideal circumstances upshifts can be less than 50 ms. No automatics are that fast. The fastest auto I have heard of is in the Lexus IS-F and IIRC that box can shift in 200ms.

The transmissions continue to get faster and better and although there is not a lot of room left in terms of pure speed of the fastest shifts there is much room to continue DCT/DSG boxes.

Also reaction times and shift times are VERY different. A reaction time is based on a somewhat random stimulus. A shift is very carefully planed and orchestrated to occur just when one wants, absolutely no random stimulus. It's basically only coincidence that a typical reaction time and typical shift time are similar.
I will stand by my statement that once shift time is below 200ms futher improvements are moot. I will also say that from my experience the DCT is very good at being an automatic transmission when it is in automatic mode and I did not find either the 335is or the M3 DCT to be jerky in stop an go traffic.

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Last edited by captainaudio; 02-08-2011 at 12:11 AM..
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      02-08-2011, 12:14 AM   #18
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The quoted shift times all vary as well. Many times, it's not referring to the entire process. Basically, many would start with fuel cut-off, meshing of gears, and then back to fuel supply, all within the quoted 100-200ms. Typically, the faster times quoted are referring to the meshing of gears, or switching between the two clutches. The current f1 transmission are seamless, where two gears are simulatenously engaged for a split second. In any case, pretty much all of the newer automated transmissions are very fast.

What interests me is that Porsche is apparently getting ready to debut a 7MT. I wonder if BMW will be following suit.
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      02-08-2011, 12:25 AM   #19
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Can anyone explain what Kretschmer means when he says that the disadvantage of DCT is that you can't have more than 7 gears without adding additional components? Is he essentially saying that if you wanted an 8 speed dual-clutch you would have to add a third wet clutch? I just don't know enough about dual clutch transmissions to understand what he is saying there.

Also, anyone have more info on BMW's newest 8-speed automatic? Is this a torque converter automatic?
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      02-08-2011, 12:48 AM   #20
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To add an 8th gear to a DCT, you'd need to add the physical gears, plus extend the various shaft involved to accomodate them. You're also going to increase the physical size of the transmission. With a planetary gear traditional slushbox, you can create the additional ratios without adding further (physical) gears.

The current 8-speed is a traditional torque converter auto.
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      02-08-2011, 02:42 AM   #21
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Quote:
Originally Posted by swamp2 View Post
BS, DCT/DSG/etc are here to stay and they are still getting better. Software is the key, I've been saying that about DCTs for some time.

Shift times vary for DCT and vary quite a bit (up vs. down and auto vs manual mode, rpm, etc). However, under ideal circumstances upshifts can be less than 50 ms. No automatics are that fast. The fastest auto I have heard of is in the Lexus IS-F and IIRC that box can shift in 200ms.

The transmissions continue to get faster and better and although there is not a lot of room left in terms of pure speed of the fastest shifts there is much room to continue DCT/DSG boxes.

Also reaction times and shift times are VERY different. A reaction time is based on a somewhat random stimulus. A shift is very carefully planed and orchestrated to occur just when one wants, absolutely no random stimulus. It's basically only coincidence that a typical reaction time and typical shift time are similar.
I think you are right to say that DCT autos are here to stay. My dealer has loaned me a DCT auto M3 while my 6MT gets a new crank and bottom end bearings (!!) - and the experience of driving is interesting...

Accelerate - wow, what a rapid gearchange - very impressed!!!

Change down - what? How slow is that!!!!

Try to go from 5th to 2nd gear in a hairpin quickly. Suck!!! The downshift is shocking...

How about reversing out of a tight garage when the engine is cold? That is an experience. Need to be up around 2500rpm to get the auto computer clutch to engage. Bad.

DCT auto has quite a bit more development to go before it can be considered "overall" better than the 6MT, but the shifting up speed shows the potential...I'll let all the DCT auto buyers of today do all the R&D and I'll buy one when they are ready.

[yes, I know DCT is dual clutch transmission, but no where does it say manual. Looks like an auto, drives like an auto, changes for you like an auto --- so it must be an auto. It even has D,P,N, R]



BTW, all 2008 M3s will need their cranks replaced at some point. It was fixed November 2008. Just go to realoem.com and put in your VIN. Go to the crank assembly and see if the bearings and crank for your model have a new part number and the original numbers STOPPED. Scary.
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      02-08-2011, 02:59 AM   #22
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Quote:
Originally Posted by mrad01 View Post
I

Try to go from 5th to 2nd gear in a hairpin quickly. Suck!!! The downshift is shocking...
Thats because you are doing it wrong.
You don't go barreling up to a hairpin in 5th, jump on the brakes then triple down-shift to 2nd......you down-shift *as* you brake.
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