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08-20-2008, 05:16 PM | #1 |
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DCT tech question?
I'm sure if I searched long enough first I could find the answer myself. But can someone tell me how the DCT is connected to the engine? Or does anyone have a diagram showing how it works? I'm talking about the actual point by the flywheel since I guess it's not a conventional clutch or torque converter?
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08-21-2008, 11:08 AM | #2 |
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it is a convential dual disk clutch (except its a wet clutch)...the difference is how the clutch is acutated by a solenoid or something vs a slave cylinder driven by your foot in most manuals....
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Brian
2008 E92 M3, MR, DCT, extended BB leather, loaded! 1988 Porsche 928S4, Guards red/Champagne leather 1989 Porsche 928S4 track beast!!! |
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08-23-2008, 12:40 PM | #4 |
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The M-DCT uses two clutch assemblies that are multiple disc wet design (like the clutches used in automatic transmissions). The clutches are applied (engaged) by hydraulic pressure and released (disengaged) by springs. Each clutch assembly is attached to a separate input shaft. One input shaft has the even numbered gears and the other the odd numbered gears. The shifts are completed by releasing one clutch and applying the other. The computer (seen in the second picture) makes sure everything works like magic.
The M-DCT clutches are NOT like the clutch used in the manual transmission cars OR the SMG used in the M5/M6 vehicles (and older M3’s). There is a video description on the BMW USA website in the M3 technical section. Enjoy the pictures. |
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08-23-2008, 08:52 PM | #6 |
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Awesome pics!
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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) |
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08-26-2008, 08:26 PM | #7 |
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Next question:
I understand the actual shift if very fast, but from what I read (since I haven't gotten to drive one yet) there is a slight lag between when you hit the paddle and the shift happens. Why is there a lag and how bad is it?
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08-27-2008, 12:28 AM | #9 | |
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Quote:
My “butt meter” says that damm! this is consistently the fastest shifting production street transmission on the planet. Then my understanding of power train takes over and I know that the shift didn’t happen instantly just like it doesn’t in a manual transmission car. Manual Transmission: Driver decides it’s time to shift Takes hand off steering wheel to grab shifter Pushes clutch in (even if you don’t use the clutch it still takes time to pull the lever) Moves shift lever Releases the clutch pedal Returns hand to steering wheel. M-DCT: Driver decides it’s time to shift Pulls paddle with fingers The steering column switch cluster sends a signal to the M-DCT electronics (attached to the passenger side of the transmission. The decision on how fast to shift is determined by data (load, RPM, rate of throttle movement, temp, etc….) from the DME –Digital Engine Electronics through the PT-CAN buss connected to the M-DCT electronics. Electronic signals are sent to the clutch and shift rail control valves. Hydraulic transmission fluid pressure moves the shift rail to select the gear (Note: with the DCT very often the gear has been pre-selected because the software makes a decision about what the driver/vehicle will need. The active clutch hydraulic pressure is dumped and the clutch releases with spring pressure. The selected clutch is engaged by using hydraulic pressure. This timing is critical because both clutches CAN NOT be engaged at the same time! BAM another amazing shift The M-DCT “delay” is like many other electro-mechanical devices….you push the keys and it takes a while for the letters to appear on the screen. As long as I push the right key I get what I hoped for. I like my M-DCT M3 because of the automatic mode and manual mode. This transmission is also one of the smoothest shifting automatic transmissions I have experienced and my wife can drive it if needed. You will see many more manufacturers beginning to use DCT’s to replace traditional automatic transmissions. As a point of reference I have taught college level automatic and manual transmission classes for 32 years. From 1970-72 I drove an SS/DA 1970 Dodge Challenger 426 Hemi (manual valve body automatic) 10.50s @ 130 mph and a street 340 cid 1968 Dodge Dart (also an automatic) that ran 13.13 @ 110 mph. |
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08-29-2008, 01:46 PM | #11 |
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08-29-2008, 02:46 PM | #12 |
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Post em up. Heck I would start a new topic for hi-res DCT photos! Thanks again.
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08-30-2008, 07:44 PM | #13 |
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Seconded
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