DCT Doesn't Rev Match - Software Issue???

[edwchow]

After getting to operating temperature in my 2015 F80 M3 and then parking for 5-10 mins, then starting it and driving off, the DCT suddenly forgets how to rev match when slowing down into second gear. Here are two instances of this happening (take note of the noise and the visible jerk when this happens):

Slowing down from 50km/h

Slowing down from 20km/h, you can see the camera shaking too when the DCT downshifts to second

This happens for 2-3 minutes when I start driving, and goes away afterwards. There are no error codes, and the DCT behaves 100% normally otherwise.

There is another issue that happens sometimes under the same conditions (Parking the car warm, and then driving off a few minutes later), where the clutch seems to engage and disengage multiple times when up-shifting into second gear and accelerating. This causes a repetitive clicking noise that happens for around a second, where it clicks 5-6 times and the car does not accelerate.

I brought it to the dealership for diagnosis, but they couldn't reproduce the issue, which makes sense as I only encounter this issue once or twice a week. Any help would be appreciated!

[F82///M]

Originally Posted by edwchow

After getting to operating temperature in my 2015 F80 M3 and then parking for 5-10 mins, then starting it and driving off, the DCT suddenly forgets how to rev match when slowing down into second gear. Here are two instances of this happening (take note of the noise and the visible jerk when this happens):

Slowing down from 50km/h

Slowing down from 20km/h, you can see the camera shaking too when the DCT downshifts to second

This happens for 2-3 minutes when I start driving, and goes away afterwards. There are no error codes, and the DCT behaves 100% normally otherwise.

There is another issue that happens sometimes under the same conditions (Parking the car warm, and then driving off a few minutes later), where the clutch seems to engage and disengage multiple times when up-shifting into second gear and accelerating. This causes a repetitive clicking noise that happens for around a second, where it clicks 5-6 times and the car does not accelerate.

I brought it to the dealership for diagnosis, but they couldn't reproduce the issue, which makes sense as I only encounter this issue once or twice a week. Any help would be appreciated!

It doesn't rev match when dct drivelogic is in setting 1, only 2 and 3. Setting 1 allows more clutch slippage so I would avoid using it. I might be wrong but think I've seen someone saying setting 1 will rev match if the throttle is applied while down shifting, haven't tried that.

Occasional jerk while slowing down, in my case was fixed 95% via gts dct flash. Happens rarely these days assuming adaptation took some time to learn.

[NSX2M4]

Why would a DCT need to rev match when it can literally shift while in gear???

[csboi]

Originally Posted by NSX2M4

Why would a DCT need to rev match when it can literally shift while in gear???

To reduce wear on the clutches.

[alex2364]

Originally Posted by NSX2M4

Why would a DCT need to rev match when it can literally shift while in gear???

This is like asking why would a stick shift driver need to rev match when he can use the clutch.

[NSX2M4]

Originally Posted by alex2364

This is like asking why would a stick shit driver need to rev match when he can use the clutch.

Rev matching makes sense for a manual. For a DCT, the shift takes a nanosecond. But one could always argue that they're real drivers doing real things like yourself. BTW, you spelled shift wrong.

[csboi]

Originally Posted by NSX2M4

Rev matching makes sense for a manual blah blah blah

Dude you have your answer. Believe it, or don't. What more do you want?

Hope this helps - https://auto.howstuffworks.com/dual-...ansmission.htm