Close

Results 1 to 11 of 11
  1. #1
    Join Date
    Feb 2010
    Location
    NJ
    Posts
    13,426
    Rep Points
    58.0
    Mentioned
    318 Post(s)
    Rep Power
    0


    1 out of 1 members liked this post. Yes Reputation No

    how does BMW M3 DCT(double clutch transmission) works


  2. #2
    Join Date
    Apr 2011
    Location
    Jersey City
    Posts
    3,852
    Rep Points
    3,647.6
    Mentioned
    74 Post(s)
    Rep Power
    37


    Yes Reputation No
    nice vid....a true upgraded DCT needs a software change...the way the transmission holds the clutch for the next gear and uses a "controlled slip" into the next gear is hydraulic and electronic...just changing the clutches is half the battle...

    Some vids that explain DCT operation....not the m3 trans, but you get the idea




    Click here to enlarge
    ESS 6XX kit

  3. #3
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    120,249
    Rep Points
    32,700.6
    Mentioned
    2130 Post(s)
    Rep Power
    328


    Yes Reputation No
    Click here to enlarge Originally Posted by bobS Click here to enlarge
    nice vid....a true upgraded DCT needs a software change...the way the transmission holds the clutch for the next gear and uses a "controlled slip" into the next gear is hydraulic and electronic...just changing the clutches is half the battle...
    Yep, true. I don't know who has truly demonstrated control of the DCT software. Not really anybody I can think of...
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  4. #4
    Join Date
    Feb 2011
    Posts
    1,590
    Rep Points
    2,018.0
    Mentioned
    10 Post(s)
    Rep Power
    21


    Yes Reputation No
    See below - tried to delete, too late.

  5. #5
    Join Date
    Feb 2011
    Posts
    1,590
    Rep Points
    2,018.0
    Mentioned
    10 Post(s)
    Rep Power
    21


    1 out of 1 members liked this post. Yes Reputation No
    This is interesting that you guys posted about this today. I actually emailed

    Dr.-Ing. Hartmut Faust
    Chief Engineer Technical Excellence

    GETRAG Getriebe- und Zahnradfabrik

    and asked him about the millisecond delay - and asked how there was a delay if there was no loss in tractive force. For those interested, here is his reply:

    you are right, with the GETRAG PowerShift there is no loss of tractive force during shift.
    This is different to AMTs (Automated Manual Transmissions) where the power flow from engine to wheel is cut in the phase where clutch is opened, old gear is disengaged, new gear to be synchronized, clutch torque ramped up again.

    In PowerShift this torque break time is not existent, so we can say it is zero. And this is the main reason for the very good shift quality.
    What is talked about shift time in PowerShift/DCT usually means just the phase the engine speed needs to ramp from old to new speed according to the gear ratios, with tractive force available.

    More in detail the main phases for (up-) shift in PowerShift are:
    1 Torque handover, from offgoing clutch to oncoming clutch, with tractive force
    2 Speed phase, just pulling engine speed down to the lower engine speed in higher gear, with tractive force (shift time)
    "tq breaktime 0 ms"

    For AMT the main phases are:
    1 Tq ramp-down of clutch tq ramp
    2 Disengagement of old gear tq break
    3 Dynchronizing and engagement of new gear tq break
    4 Tq ramp-up of clutch tq ramp
    "tq break time xxx ms"

    Hope this helps.

    Mit freundlichen Gren/ Kind regards
    Dr.-Ing. Hartmut Faust
    Chief Engineer Technical Excellence

    GETRAG Getriebe- und Zahnradfabrik
    Hermann Hagenmeyer GmbH & Cie KG
    GETRAG InnovationsCenter
    Hermann-Hagenmeyer-Strae
    D-74199 Untergruppenbach





    --- My question ---

    I am having issue deciphering what the quoted shift time of a DCT is; is it possible to obtain a proper explanation? What I mean by this is, most car manufacturers (BMW or Mercedes) quote something like no loss of tractive force yet also quote shift times of 100ms or less when using your transmissions. If there is no loss of tractive force, how can there be an associated time? Is this time quoted by the manufacturer for something that I am not understanding? Is there an indeed a loss of tractive force for under 100 ms?

    I am at a loss with the technical information I have found - I cannot find any solid evidence of what this time means.

    I am looking forward to hearing back and very much appreciate your time.

  6. #6
    Join Date
    Apr 2011
    Location
    Jersey City
    Posts
    3,852
    Rep Points
    3,647.6
    Mentioned
    74 Post(s)
    Rep Power
    37


    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Yep, true. I don't know who has truly demonstrated control of the DCT software. Not really anybody I can think of...
    yep, until someone breaks into the software....its useless to upgrade or pay for any kind of half upgrade imo
    Click here to enlarge
    ESS 6XX kit

  7. #7
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    120,249
    Rep Points
    32,700.6
    Mentioned
    2130 Post(s)
    Rep Power
    328


    Yes Reputation No
    Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
    In PowerShift this torque break time is not existent, so we can say it is zero. And this is the main reason for the very good shift quality.
    What is talked about shift time in PowerShift/DCT usually means just the phase the engine speed needs to ramp from old to new speed according to the gear ratios, with tractive force available.
    This is interesting, effectively 0?

    So to people list time from what? The torque ramp down to ramp up?
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  8. #8
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    120,249
    Rep Points
    32,700.6
    Mentioned
    2130 Post(s)
    Rep Power
    328


    Yes Reputation No
    Click here to enlarge Originally Posted by bobS Click here to enlarge
    yep, until someone breaks into the software....its useless to upgrade or pay for any kind of half upgrade imo
    We'll see won't we?
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  9. #9
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    120,249
    Rep Points
    32,700.6
    Mentioned
    2130 Post(s)
    Rep Power
    328


    Yes Reputation No
    Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
    This is interesting that you guys posted about this today. I actually emailed

    Dr.-Ing. Hartmut Faust
    Chief Engineer Technical Excellence

    GETRAG Getriebe- und Zahnradfabrik

    and asked him about the millisecond delay - and asked how there was a delay if there was no loss in tractive force. For those interested, here is his reply:

    you are right, with the GETRAG PowerShift there is no loss of tractive force during shift.
    This is different to AMTs (Automated Manual Transmissions) where the power flow from engine to wheel is cut in the phase where clutch is opened, old gear is disengaged, new gear to be synchronized, clutch torque ramped up again.

    In PowerShift this torque break time is not existent, so we can say it is zero. And this is the main reason for the very good shift quality.
    What is talked about shift time in PowerShift/DCT usually means just the phase the engine speed needs to ramp from old to new speed according to the gear ratios, with tractive force available.

    More in detail the main phases for (up-) shift in PowerShift are:
    1 Torque handover, from offgoing clutch to oncoming clutch, with tractive force
    2 Speed phase, just pulling engine speed down to the lower engine speed in higher gear, with tractive force (“shift time”)
    "tq breaktime 0 ms"

    For AMT the main phases are:
    1 Tq ramp-down of clutch tq ramp
    2 Disengagement of old gear tq break
    3 Dynchronizing and engagement of new gear tq break
    4 Tq ramp-up of clutch tq ramp
    "tq break time xxx ms"

    Hope this helps.

    Mit freundlichen Gren/ Kind regards
    Dr.-Ing. Hartmut Faust
    Chief Engineer Technical Excellence

    GETRAG Getriebe- und Zahnradfabrik
    Hermann Hagenmeyer GmbH & Cie KG
    GETRAG InnovationsCenter
    Hermann-Hagenmeyer-Strae
    D-74199 Untergruppenbach





    --- My question ---

    I am having issue deciphering what the quoted shift time of a DCT is; is it possible to obtain a proper explanation? What I mean by this is, most car manufacturers (BMW or Mercedes) quote something like “no loss of tractive force” yet also quote “shift times of 100ms or less” when using your transmissions. If there is no loss of tractive force, how can there be an associated time? Is this time quoted by the manufacturer for something that I am not understanding? Is there an indeed a loss of tractive force for under 100 ms?

    I am at a loss with the technical information I have found - I cannot find any solid evidence of what this time means.

    I am looking forward to hearing back and very much appreciate your time.
    Maybe you should e-mail to ask if hey will reprogram my gearbox... Click here to enlarge
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  10. #10
    Join Date
    Feb 2011
    Posts
    1,590
    Rep Points
    2,018.0
    Mentioned
    10 Post(s)
    Rep Power
    21


    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    This is interesting, effectively 0?

    So to people list time from what? The torque ramp down to ramp up?
    That's exactly how I took it also. When thinking about it - it makes sense I guess. It seems the bigger engines are the ones that claim a longer time - so maybe they just take a few more ms to drop from redline to next gear's RPM?

    I was surprised he replied to tell you the truth. Click here to enlarge

  11. #11
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    120,249
    Rep Points
    32,700.6
    Mentioned
    2130 Post(s)
    Rep Power
    328


    Yes Reputation No
    Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
    I was surprised he replied to tell you the truth.
    Nah, they are pretty good about it. When I e-mailed asking about drivetrain losses they replied back which was cool.
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •