BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i)
 





 

Post Reply
 
Thread Tools Search this Thread
      01-04-2010, 10:54 PM   #1
JHZR2
Captain
16
Rep
906
Posts

 
Drives: 91 E30, 11 135i cv
Join Date: Mar 2009
Location: New Jersey

iTrader: (0)

Tell me more about DCT

Hello,

Ive been in the market for a BMW 135i for a while. Havent bit the bullet for a number of reasons, but Ive been tracking things... Interesting news that the 2011 model will have a 7-speed DCT.

Im a die-hard MT fan, and really do not like ATs at all. However, 7 speeds and continuous forward momentum with a turbo engine (so there are no pressure variations during shifts) is a good thing... Not that I drive hard - Id drive the thing super-gently 99.9% of the time.

Anyway, I initially dismissed the DCT as more or less an automatic. It only has two pedals, and you can put it in "D" and just turn the brain off... but can you?

Reviewing how to operate the DSG at wikipedia (FWIW):
http://en.wikipedia.org/wiki/Direct-Shift_Gearbox

I get this:
""N"

N position of the floor-mounted shift lever means that the transmission is in "neutral". Similar to P above, both clutch packs and all gear-sets are fully disengaged, however the parking lock is disengaged. This position should be used when the motor vehicle is stationary for a period of time, such as at red traffic lights, or waiting in a queue of stationary traffic.[19] The DSG should not be held in any of the active gear modes while stationary using the footbrake for other than brief periods - due to the clutches being held on the bite point, as this can overheat the clutches and transmission fluid.[19]"

So this tells me that you cannot turn your brain off like with an AT. Or, I guess you can (for a little while), but you will be damaging your gearbox.

So, what's the deal with the DCT/DSG/dual clutch gearbox? You DO always need to be involved for the trans to last?

Im sure repairs are expensive, and there is lots of fluid replacement if it is anything like what Ive heard of the VW DSG - fluid costs aside, Im mainly interested if you DO need to ALWAYS be engaged - a "D" position isnt a set and forget position like it is in an AT.

Any comments or ideas? Ive never even driven a VW DSG...

Thanks!
Appreciate 0
      01-05-2010, 12:03 PM   #2
Tom K.
Major General
Tom K.'s Avatar
United_States
55
Rep
5,412
Posts

 
Drives: '07 328iT, '13 Boxster
Join Date: Mar 2008
Location: Maryland

iTrader: (0)

Quote:
Originally Posted by JHZR2 View Post
The DSG should not be held in any of the active gear modes while stationary using the footbrake for other than brief periods - due to the clutches being held on the bite point, as this can overheat the clutches and transmission fluid.[19]"

So this tells me that you cannot turn your brain off like with an AT. Or, I guess you can (for a little while), but you will be damaging your gearbox.
Since the DCT will apparently replace the current torque converter "Sport Automatic", I wonder how many future 135i "A/T" buyers will encounter transmission problems for that very reason!

Tom
Appreciate 0
      01-05-2010, 12:52 PM   #3
emtrey
Captain
emtrey's Avatar
9
Rep
657
Posts

 
Drives: 13 335 AW sport 06 Carrera S
Join Date: Jul 2009
Location: Midwest

iTrader: (0)

Considering the high percentage of AT 135s d/cing that option could create problems.

I would love the DCT choice but my wife does use the car on occasion and she prefers
the non involvement mode of driving. She does like powerful cars but that is where her involvement starts and ends.
Appreciate 0
      01-05-2010, 03:54 PM   #4
RPM90
Major General
105
Rep
6,095
Posts

 
Drives: 335i Msport w/sport AT
Join Date: Mar 2006
Location: Chicago

iTrader: (1)

Quote:
Originally Posted by emtrey View Post
Considering the high percentage of AT 135s d/cing that option could create problems.

I would love the DCT choice but my wife does use the car on occasion and she prefers
the non involvement mode of driving. She does like powerful cars but that is where her involvement starts and ends.
A DCT will be perfect for her and for anyone else who wants an 'automatic' trans where they can simply put it in "D"rive and go about their merry business while never having to touch a trans related button or lever other than the typical things anyone does in any automatic trans.

A dual clutch trans can operate in FULL automatic mode where you simply select "drive" and go. You don't need to worry about stop and go traffic and how long you've been on the brakes or anything like that, well, at least that's how it's been for the current crop of DCT's from VW and Mits.
If BMW doesn't do something hair-brained to mess up a good thing, minimal driver involvement is all that will be needed to use it.

For those want some involvement the DCT will operate pretty much the same as the Sportronic trans does now. If you want manual mode you can have it, and you can select gears with either the console lever or the paddle shifters. How far to redline or near redline the system will allow before doing an automatic upshift is up to BMW. I hope the system will allow full up to the limiter performance without upshifting for us.

The main problems with DCT's is how smooth or unsmooth they can be in stop and go traffic where a manual driver will typically need to slip the clutch in order to stay with traffic and do it smoothly. The Audi/VW DSG has had some unsmooth or harsh operation in heavy stop/go traffic where the clutch's get warm, and there can be a bit of lag on take off on some cars when trying to take off slow and smooth.
Clutch heat is one issue, and smooth clutch application via software is another. Still, overall I find these transmissions to be really cool and quite smooth for what they do.
A torque converter can take up much more shock than a DCT as the TC has fluid to help dampen engine to trans shock, whereas a DCT is a standard clutch operated trans where the clutch is operated by electronics, but it's still a "hard" connection between engine and trans.
But, to me that's what makes if feel more like the real thing.
Appreciate 0
      01-05-2010, 06:36 PM   #5
clausy
Private First Class
2
Rep
147
Posts

 
Drives: 135i M Sport Pack
Join Date: Dec 2009
Location: Westport CT

iTrader: (0)

Quote:
Originally Posted by JHZR2 View Post
Any comments or ideas? Ive never even driven a VW DSG...

Thanks!
I just got out of a GTi with DSG. Originally I wanted a stick but after one driveI was really impressed. It really is faster than a stick if you floor it. It shifts up like silk. Amazing.

After about 10 minutes of owning it you start to hate it. Don't get me wrong, in traffic it's great so if you commute a lot in traffic then get one. As soon as you're on your own on open roads you'll hate it. It's never quite in the right gear: D would shift up too early, sport would go to redline and there's no 'sporty' inbetween. Powering out of corners it would gulp for air because it was never ready to shift down: it would be in 3rd with 4 selected, when you wanted 2, so you get air while it pops down from 4 to 2 on the one clutch.

I couldn't wait to get rid of it. If you like to drive, then don't get one. If you want to drag race then fine. It's also notchy on the way down under braking: it shifts down, does nice rev matching but still manages to be bumpy, so no smooth decel. That also used to get to me.

I never ever put it in neutral at the lights: thats just garbage.

Hope that helps. I'm much happier with a stick. I think DSG is a step up from slushbox: faster, more economical but it won't replace a real clutch for me at least.
Appreciate 0
      01-05-2010, 07:44 PM   #6
bmwzone
Captain
bmwzone's Avatar
12
Rep
778
Posts

 
Drives: Black 5.0 (ordered), 135i
Join Date: Apr 2008
Location: USA

iTrader: (1)

Garage List
2008 135i  [0.00]
Funny how all these slushbox "improvements" are in an attempt to make the experience fun. Then again you could save the cash with improved reliability and buy the benchmark 6mt.
Appreciate 0
      01-05-2010, 08:05 PM   #7
jeremyc74
Banned
United_States
66
Rep
5,972
Posts

 
Drives: '08 135i Montego/Terra
Join Date: Feb 2008
Location: Evansville, IN

iTrader: (0)

Quote:
Originally Posted by bmwzone View Post
Funny how all these slushbox "improvements" are in an attempt to make the experience fun. Then again you could save the cash with improved reliability and buy the benchmark 6mt.

If you think a DCT is a slushbox, you either don't know what the term means, or don't understand how they work.
Appreciate 0
      01-05-2010, 08:16 PM   #8
vasracer
Private
0
Rep
97
Posts

 
Drives: 2009 BMW 135i 6spd Msport
Join Date: Apr 2009
Location: Santa Monica, CA

iTrader: (0)

$.02 worth

if you are really interested in dct, just go to the lively discussion on the m3 boards...

but...we had an audi a3 dsg for 3 years, my wife's daily driver. She never knew what those things behind the wheel were for (paddle shifters). Almost everytime I drove it, I would put it in manual mode for approximately 3 minutes, when I got bored and put in D or S (auto modes). S made great sounds on downshifting, but wasted gas.

A couple of times I went into the Malibu canyons, though, and then it was fun. I played with left foot braking, trail braking (it's harder to spin a noseheavy frontdriver) and shifting with paddles (like GT5 or Forza). I now know why some fast autoxers have autos...I also fried my brake pads.

No, seriously, if you change the way you drive fast, the paddles are awesome. They probably are the future. But I suspect most people will leave it in auto soon after they take delivery.
Appreciate 0
      01-05-2010, 08:29 PM   #9
raisemyrent
Captain
Canada
10
Rep
901
Posts

 
Drives: Estoril Bue 435i
Join Date: Mar 2008
Location: Vancouver, BC

iTrader: (0)

isn't a DSG different than a DCT? old M3 used to have a DSG everyone hated kinda thing?
__________________
435i Coupe
Estoril Blue on Black
X Drive, M Sport Package Stage II, Premium Package
Appreciate 0
      01-05-2010, 08:39 PM   #10
jeremyc74
Banned
United_States
66
Rep
5,972
Posts

 
Drives: '08 135i Montego/Terra
Join Date: Feb 2008
Location: Evansville, IN

iTrader: (0)

Quote:
Originally Posted by raisemyrent View Post
isn't a DSG different than a DCT? old M3 used to have a DSG everyone hated kinda thing?
Edit: This should be SMG instead of DSG. The SMG was what was used in the previous generation M3 and wasn't very well liked.

Yeah, they're different. The SMG used a single clutch, and was really just sort of an automated manual transmission, except you couldn't skip gears. When it does a gear change, it's much the same process as a manual:

Clutch in
Select Gear
Clutch out

With the DCT, there's two shafts (one takes care of odd numbered gears and the other takes care of even) and two clutches. The gear selection takes place while the other shaft is engauged, so when it's time to shift, it simply switches shafts. That makes it extremely fast.

I'd have to test drive one before I'd jump on it, but I'd certainly consider it. The real issue with them, as mentioned above, is making them smooth around town, where it's constantly engauging and disengauging the clutch. A good manual driver can modulate the gas and clutch to keep from jerking the car around in traffic, and that's something that's pretty hard to program.

Last edited by jeremyc74; 01-05-2010 at 11:09 PM.
Appreciate 0
      01-05-2010, 08:42 PM   #11
red-sauerkraut
.
red-sauerkraut's Avatar
45
Rep
3,927
Posts

 
Drives: x-car/m-car
Join Date: Oct 2007
Location: northern hemisphere

iTrader: (0)

IMO it is not an auto, but rather a manual w/out a clutch pedal!

It is one of my favorite tranny's w/out a doubt.

To bad it will not mate-up to x-drive...
__________________
LESS LIMIT. MORE SKY.
Appreciate 0
      01-05-2010, 08:57 PM   #12
ennislaw
NCO
United_States
7
Rep
640
Posts

 
Drives: 2010 BSM 135i M-Sport
Join Date: Nov 2008
Location: RTP

iTrader: (0)

Quote:
Originally Posted by bmwzone View Post
Funny how all these slushbox "improvements" are in an attempt to make the experience fun. Then again you could save the cash with improved reliability and buy the benchmark 6mt.
No doubt great for racing or those times when you need an auto in bumper-to-bumper traffic, but how do you shift from 2nd to 4th or 4th to 6th without slapping the paddles an extra time?

pge
Appreciate 0
      01-05-2010, 09:01 PM   #13
jeremyc74
Banned
United_States
66
Rep
5,972
Posts

 
Drives: '08 135i Montego/Terra
Join Date: Feb 2008
Location: Evansville, IN

iTrader: (0)

Quote:
Originally Posted by ennislaw View Post
No doubt great for racing or those times when you need an auto in bumper-to-bumper traffic, but how do you shift from 2nd to 4th or 4th to 6th without slapping the paddles an extra time?

pge

It can't skip gears, but it will change so fast it won't really matter.
Appreciate 0
      01-05-2010, 09:07 PM   #14
ennislaw
NCO
United_States
7
Rep
640
Posts

 
Drives: 2010 BSM 135i M-Sport
Join Date: Nov 2008
Location: RTP

iTrader: (0)

Quote:
Originally Posted by jeremyc74 View Post
It can't skip gears, but it will change so fast it won't really matter.
Maybe it does not matter to you, but everyone isn't racing all the time on public streets (I hope). It's an issue of the control you lose. A person choice, but nonetheless, it's a loss of that choice.

pge
Appreciate 0
      01-05-2010, 09:17 PM   #15
jeremyc74
Banned
United_States
66
Rep
5,972
Posts

 
Drives: '08 135i Montego/Terra
Join Date: Feb 2008
Location: Evansville, IN

iTrader: (0)

Quote:
Originally Posted by ennislaw View Post
Maybe it does not matter to you, but everyone isn't racing all the time on public streets (I hope). It's an issue of the control you lose. A person choice, but nonetheless, it's a loss of that choice.

pge

I'm not sure I understand where the loss of control is? The only real reason to skip gears going up or down in a manual transmissioned vehicle is just so you don't have to operate the clutch more often than needed. This is taking care of that for you, so why would you want to skip them?
Appreciate 0
      01-05-2010, 09:21 PM   #16
Cuz5150
Major
Cuz5150's Avatar
21
Rep
1,271
Posts

 
Drives: 06-M3ZHP/04-M3 Vert/02Duc998
Join Date: May 2008
Location: NJ

iTrader: (0)

JHRZ2 go and test drive a used VW gti with DCT. Play with it and see if you like it. The word on the street is the VW is a fantastic trans. They have got it "right". As for the BWM being new, I wouldnt touch it with a 10 ft pole. Something like that, i would wait a year or 2 to be safe.
As for the trans is a manual with out a clutch pedal. no ATF fluid and NO power sapping converter. THe down side its way to complex with more parts...etc.

So, at the end of the day, good ol' Manual is still the king IMHO
__________________
-Diplomacy is saying, "nice doggie while trying to find a rock"-

04-M3 vert-Black/Imolla/6MT/Cold/Xenon/HK/
06-M3 Cp-Mystic/Black/6MT/Comp/Xenon/HK/
09-135i- AW/Bk-Lette/6MT/M-pac/Nav/Hi-Fi/Usb-Ipod/SOLD
Appreciate 0
      01-05-2010, 09:26 PM   #17
ennislaw
NCO
United_States
7
Rep
640
Posts

 
Drives: 2010 BSM 135i M-Sport
Join Date: Nov 2008
Location: RTP

iTrader: (0)

Quote:
Originally Posted by jeremyc74 View Post
I'm not sure I understand where the loss of control is? The only real reason to skip gears going up or down in a manual transmissioned vehicle is just so you don't have to operate the clutch more often than needed. This is taking care of that for you, so why would you want to skip them?
No, you don't understand. It's not about using or not using the clutch, it is about a *choice*. I get to choose which gear I shift to without the machinery telling me I have to go through another gear. Again, I repeat, it's a personal choice and for a lot of folks it is not an issue.

pge
Appreciate 0
      01-05-2010, 09:31 PM   #18
jeremyc74
Banned
United_States
66
Rep
5,972
Posts

 
Drives: '08 135i Montego/Terra
Join Date: Feb 2008
Location: Evansville, IN

iTrader: (0)

Quote:
Originally Posted by ennislaw View Post
No, you don't understand. It's not about using or not using the clutch, it is about a *choice*. I get to choose which gear I shift to without the machinery telling me I have to go through another gear. Again, I repeat, it's a personal choice and for a lot of folks it is not an issue.

pge

You still get to choose exactly which gear you want to be in. If you want to go from fourth to second, tap it twice. It's really not a big deal. In that situation using a manual, why would you skip 3rd if it's not about just not operating the clutch an extra time?

Just about every bike on the road today is running a sequential box that requires the same thing.
Appreciate 0
      01-05-2010, 09:40 PM   #19
ennislaw
NCO
United_States
7
Rep
640
Posts

 
Drives: 2010 BSM 135i M-Sport
Join Date: Nov 2008
Location: RTP

iTrader: (0)

Quote:
Originally Posted by jeremyc74 View Post
You still get to choose exactly which gear you want to be in. If you want to go from fourth to second, tap it twice. It's really not a big deal. In that situation using a manual, why would you skip 3rd if it's not about just not operating the clutch an extra time?

Just about every bike on the road today is running a sequential box that requires the same thing.
Ya know, when you don't get it, ya don't get it. It obviously is not an issue for you, but I suspect I'm not the only one who would still like to make that choice for myself.

pge
Appreciate 0
      01-05-2010, 09:40 PM   #20
JHZR2
Captain
16
Rep
906
Posts

 
Drives: 91 E30, 11 135i cv
Join Date: Mar 2009
Location: New Jersey

iTrader: (0)

I will go test drive a VW with DSG, as we are in the market at some point for a jetta diesel wagon...

That said, I have 120k miles on my original clutch in my 91 318i, and I have driven that in a LOT of traffic... it is great in traffic. My wife's old integra was terrible... it seems that BMW is an OK traffic MT... Though Ill try to simulate that on a test drive I guess.

Sounds like the MT is still for me, which is exactly what I anticipated... since the MT will still be there on a MY11, Im happy.

Seems that the clutch heating mentioned above is due to drivers NOT putting the trans in neutral, and thus the clutch sitting at the bite point too much/too long. Maybe there is truth in the wiki write-up? I always put my slushbox ATs in neutral when stopped or coasting to a stop in traffic...

Thanks!
Appreciate 0
      01-05-2010, 10:55 PM   #21
vasracer
Private
0
Rep
97
Posts

 
Drives: 2009 BMW 135i 6spd Msport
Join Date: Apr 2009
Location: Santa Monica, CA

iTrader: (0)

Quote:
Originally Posted by raisemyrent View Post
isn't a DSG different than a DCT? old M3 used to have a DSG everyone hated kinda thing?
i think dsg and dct are both dual clutch gearboxes, smg was the e46m3 gearbox.

The reason the dual clutches are so fast and smooth is because they preselect the next gear on the opposite clutch (or something equivalent) and just switch seamlessly. Things aren't so fast when you go two gears up or down (same clutch). Trust me, though...dsg on audi will go from 6-3 with 3 tugs on the paddle quite quickly. I used to purposely lift the throttle on upshifts just so I could feel the engine pull between gears, otherwise it was just seamless power delivery. As good as any automatic, better than my experience with smg (just a couple of days).

I don't know why i am so vocal on this, maybe i am just excited because i actually have some experience on something on this forum.!!
Appreciate 0
      01-05-2010, 11:06 PM   #22
jeremyc74
Banned
United_States
66
Rep
5,972
Posts

 
Drives: '08 135i Montego/Terra
Join Date: Feb 2008
Location: Evansville, IN

iTrader: (0)

Quote:
Originally Posted by vasracer View Post
i think dsg and dct are both dual clutch gearboxes, smg was the e46m3 gearbox.

!!

You are correct about that. My post above was made with the SMG in mind. I hope he meant SMG instead of DSG, otherwise all that typing was wasted.
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 09:30 PM.




1addicts
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST