BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Engine, Transmission, Exhaust, Drivetrain, ECU Software Modifications
 
BPM
Post Reply
 
Thread Tools Search this Thread
      07-11-2008, 08:40 PM   #1
EscortKing
Registered
1
Rep
3
Posts

Drives: Opel Corsa 1.5D Swing
Join Date: Nov 2007
Location: Valencia, Spain

iTrader: (0)

Question Any videos for confirming/refuting M-DCT upshift lag?

I mean, it wouldn't be so difficult to take a video that shows the moment when your hand presses the paddle and the revs fall because of the gear change. We could then measure the time difference, leaving the subjective part out of the equation.

Any other ideas for finding out if this is a general issue or just a defective batch of M-DCT boxes?

Regards.
Appreciate 0
      07-12-2008, 01:33 AM   #2
MDCTFTW
Lieutenant Colonel
123
Rep
1,973
Posts

Drives: E92 DCT
Join Date: Apr 2008
Location: Norcal

iTrader: (0)

What lag? DCT is instantaneous.
__________________


MDCT ... so you can drive and eat a hamburger at the same time.
Appreciate 0
      07-12-2008, 05:50 AM   #3
EscortKing
Registered
1
Rep
3
Posts

Drives: Opel Corsa 1.5D Swing
Join Date: Nov 2007
Location: Valencia, Spain

iTrader: (0)

I'm sure you know what I mean. In auto mode it is nearly instantaneous as any other double clutch system. But in manual mode, many people claim that there is a lag from the moment the driver presses the paddle till the software/hardware "decides" to execute the upshift. Once the upshift begins, it is nearly instantaneous. Many other people claim that there is no lag at all, that it is as fast in manual as in auto. It is not clear if this is an issue related to the driver... maybe the drivers that feel the lag are very sensitive, maybe they do something wrong, maybe the drivers that don't feel the lag are not sensitive at all... OR maybe this "problem" is not present in all cars.
That's why i think that some videos could solve the debate.

Regards.
Appreciate 0
      07-12-2008, 07:50 AM   #4
M-Maika
First Lieutenant
M-Maika's Avatar
Portugal
11
Rep
365
Posts

Drives: M3 E92 AW
Join Date: Jan 2008
Location: Barcelona ( Spain ) Porto ( Portugal )

iTrader: (0)

Garage List
2008 BMW M3 E92  [10.00]
Quote:
Originally Posted by MDCTFTW View Post
What lag? DCT is instantaneous.
Not that instantaneous.
It takes a couple of miliseconds to change gear.
IMHO i think that the gear changes are more quick in the stick. In think that the paddles are a little bit slower.
Could be just me.

Best Regards, Maika
__________________
M3 E92 M-DKG and all the options available.
Forum BMW Portugal: http://www.forumbmwportugal.com
Appreciate 0
      07-12-2008, 08:08 AM   #5
ihyln
Banned
United_States
85
Rep
3,384
Posts

Drives: M3post sucks
Join Date: Apr 2008
Location: M3post sucks

iTrader: (1)

Garage List
2008 M3  [0.00]
2002 530i  [0.00]
There is no lag. I click the paddle and it shifts. What's so hard to believe?
Appreciate 0
      07-12-2008, 09:00 AM   #6
footie
Major General
footie's Avatar
No_Country
1072
Rep
8,008
Posts

Drives: i4M50
Join Date: Oct 2007
Location: No where fast

iTrader: (0)

Garage List
Watch this video from fifthgear on the DSG, at 2:11approx watch Jason's fingers flick the paddle and listen to the revs drop. You could'n't click your fingers any quicker and that a system which is slower than the M-DCT.


Lag..............what lag?
Appreciate 0
      07-12-2008, 09:56 AM   #7
lucid
Major General
lucid's Avatar
United_States
374
Rep
8,033
Posts

Drives: E30 M3; Expedition
Join Date: Apr 2007
Location: USA

iTrader: (0)

There can be a delay depending on the conditions under which you request the shift. You can measure it when it happens. I felt it. It's been reported in press reviews. But it is pretty short and a somewhat subjective thing to consider so it would take some work to instrument things properly to be able to measure it under different conditions. This has nothing to do with the actual shift time. The lag must predominantly arise from the fact that the second clutch cannot be simultaneously pointing at the higher and the lower gear, and the system has to pick one. If you end up doing what the system has not anticipated, it will need to change the gear the second clutch is pointing at, which will cause a slight delay. No way around that unless you have a third clutch and both possibilities are always covered (2nd clutch pointing at the lower gear, 3rd clutch pointing at the higher gear). In the dual clutch system, the chance of requesting a gear the computer has not anticipated probably depends on how well the computer can predict what you want to do next depending on throttle input and engine speed and maybe some other variables. It makes sense for the computer to be conservative and pick the lower gear in normal driving conditions in low-mid range rpms since the lower gear is where the power is in case you want to accelerate quickly (for peak acceleration, the sensible thing to do would be to downshift and floor it rather than floor it in the current gear). So, the delay seems to be absent for a downshift when you are cruising around calmly. I don't see this being an issue when you are driving aggressively at high revs as what you want to do should be much more transparent to the computer in that case. That said, in objective terms, I don’t know that this is a major issue overall.

However, even if you experience a delay under certain conditions, I'm pretty sure:

the delay + DCT shift time < human MT shift time.
__________________

Last edited by lucid; 07-12-2008 at 10:41 AM..
Appreciate 1
wfdeacon881102.50
      07-14-2008, 01:44 PM   #8
Mr.AK
Second Lieutenant
41
Rep
242
Posts

Drives: 2008 M3 e92
Join Date: Jul 2008
Location: Baltimore MD

iTrader: (0)

What is LAG?....I have 2 lags, and two arms
Appreciate 0
      07-15-2008, 11:20 PM   #9
Dascamel
Lieutenant Colonel
Dascamel's Avatar
48
Rep
1,664
Posts

Drives: 2008 e92 M3, 2010 e91 328i
Join Date: Jul 2007
Location: Bakersfield, CA

iTrader: (0)

Exactly Lucid, only two clutches, one works odd gears, one even gears, if you shift in a manner its not expecting, the clutch needs to move and engage. If you shift two gears in either direction(odd gear to odd gear or even gear to even gear), delay expected. Most likely the shift is still occuring faster than most can pull it off on a MT. More to come in a month, ordered a cruisecam and eventually the car will arrive.

-Das
__________________
2008 E92 M3 Jerez Black,DCT,Fox Red ext,Prem,Tech,19", ipod/usb, CF roof and trim
2010 E91 328i Space Gray,Black int, M sport, most options
2007 Montego Blue 335i (retired)
Appreciate 0
      07-16-2008, 12:03 AM   #10
Big Windy
Major General
Big Windy's Avatar
United_States
150
Rep
5,124
Posts

Drives: None
Join Date: Mar 2007
Location: Bay Area

iTrader: (0)

Quote:
Originally Posted by lucid View Post
There can be a delay depending on the conditions under which you request the shift. You can measure it when it happens. I felt it. It's been reported in press reviews. But it is pretty short and a somewhat subjective thing to consider so it would take some work to instrument things properly to be able to measure it under different conditions. This has nothing to do with the actual shift time. The lag must predominantly arise from the fact that the second clutch cannot be simultaneously pointing at the higher and the lower gear, and the system has to pick one. If you end up doing what the system has not anticipated, it will need to change the gear the second clutch is pointing at, which will cause a slight delay. No way around that unless you have a third clutch and both possibilities are always covered (2nd clutch pointing at the lower gear, 3rd clutch pointing at the higher gear). In the dual clutch system, the chance of requesting a gear the computer has not anticipated probably depends on how well the computer can predict what you want to do next depending on throttle input and engine speed and maybe some other variables. It makes sense for the computer to be conservative and pick the lower gear in normal driving conditions in low-mid range rpms since the lower gear is where the power is in case you want to accelerate quickly (for peak acceleration, the sensible thing to do would be to downshift and floor it rather than floor it in the current gear). So, the delay seems to be absent for a downshift when you are cruising around calmly. I don't see this being an issue when you are driving aggressively at high revs as what you want to do should be much more transparent to the computer in that case. That said, in objective terms, I don’t know that this is a major issue overall.

However, even if you experience a delay under certain conditions, I'm pretty sure:

the delay + DCT shift time < human MT shift time.
that makes a lot of sense. i am a MT guy, but I know I won't be beating DCT anyday when it comes to shift times.
Appreciate 0
      07-16-2008, 12:09 AM   #11
M3WC
Brigadier General
3639
Rep
3,241
Posts

Drives: BMW
Join Date: Jul 2008
Location: ...location...location

iTrader: (0)

New DCT review by Edmunds.

Very positive, they loved it.

http://www.edmunds.com/insideline/do...hotopanel..1.*
Appreciate 0
      07-16-2008, 04:09 AM   #12
EscortKing
Registered
1
Rep
3
Posts

Drives: Opel Corsa 1.5D Swing
Join Date: Nov 2007
Location: Valencia, Spain

iTrader: (0)

Quote:
Originally Posted by JetBlack5OC View Post
New DCT review by Edmunds.

Very positive, they loved it.

http://www.edmunds.com/insideline/do...hotopanel..1.*
From this article:

Edmunds.com Editor in Chief Karl Brauer says:

[...]

"At over 2 tons this is by far the heaviest M3 ever, even outweighing its sibling coupe and sedan by several hundred pounds.
The extra strain is seen in the performance numbers, while acceleration and shifting action left me unimpressed. Using the most aggressive throttle (Sport Plus) and transmission settings had the car lurching when I drove out of corners and banging through gears like an old Torqueflite in need of a rebuild. Dialing things back to the midlevel throttle (Sport) position and halfway up the transmission settings (three bars out of six) solved most of these issues, but delays between paddle pull and shift action were still too long."
Appreciate 0
      07-17-2008, 10:20 PM   #13
2FED
Private First Class
2FED's Avatar
Spain
8
Rep
160
Posts

Drives: M3 E92 DCT
Join Date: Sep 2006
Location: Barcelona, Spain

iTrader: (0)

Garage List
2008 E92  [0.00]
2006 E90 330D  [0.00]
Quote:
Originally Posted by EscortKing View Post
From this article:

Edmunds.com Editor in Chief Karl Brauer says:

[...]

"At over 2 tons this is by far the heaviest M3 ever, even outweighing its sibling coupe and sedan by several hundred pounds.
The extra strain is seen in the performance numbers, while acceleration and shifting action left me unimpressed. Using the most aggressive throttle (Sport Plus) and transmission settings had the car lurching when I drove out of corners and banging through gears like an old Torqueflite in need of a rebuild. Dialing things back to the midlevel throttle (Sport) position and halfway up the transmission settings (three bars out of six) solved most of these issues, but delays between paddle pull and shift action were still too long."

Sometimes changing have a little delay, but not everytime. Anyway, this delay is not so much noticable.
The most bigger problem for me what I have noticied is what sometimes you pull the paddle for kick-down and nothing... pull second time and then its kicks-down... This had happened with me 2-3 times only at over 11.000kms.
__________________
M3 E92 Euro DCT / Alipne White; MDrive; EDC; PDC; Navi; 19'' Wheels; CF grille; CF lether trim; Individual Audio; STI-R; Video rec. system; Tint: 18% front, 6% rear;
Coming: Vorsteiner CF VRS Rear Diffuser, Vorsteiner CF VRS Front Add On Spoiler, Eisenmann Sport Exhaust.
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



All times are GMT -5. The time now is 11:29 AM.




m3post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
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