DCT tech question?

[J08M3]

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?

[icemang17]

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....

[J08M3]

all computer controlled I guess?

[kenwelch]

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.

[alvinjamur]

SICK!!


There is an animated description of the dual clutch assembly on the porsche website. anyone care to look there u can...

[Dascamel]

Awesome pics!

[J08M3]

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?

[J08M3]

Kenwelch thanks for the info

[kenwelch]

Originally Posted by J08M3

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?

You really need to drive an M-DCT car to get a true feel for the “delay”. Swamp was kind enough to give me an introduction. Then we purchased on July 2 and traded our 1995 E36 M3……life just isn’t the same.

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.

[swamp2]

Great pics Ken . Source?

[kenwelch]

Originally Posted by swamp2

Great pics Ken . Source?

They were posted some where???? Sorry in my enthusiam in locating info about the M-DCT I did not keep the source links. There were additional pictures that I also saved to use in my class if you are interested?

[swamp2]

Originally Posted by kenwelch

They were posted some where???? Sorry in my enthusiam in locating info about the M-DCT I did not keep the source links. There were additional pictures that I also saved to use in my class if you are interested?

Post em up. Heck I would start a new topic for hi-res DCT photos! Thanks again.

[ZoinksM3]

Originally Posted by kenwelch

They were posted some where???? Sorry in my enthusiam in locating info about the M-DCT I did not keep the source links. There were additional pictures that I also saved to use in my class if you are interested?

Seconded