DCT on Track & Downshifting Problem

[sayemthree]

consensus seems to be that SMG was better on the track then street. DCT is better on the street than the track.

[footie]

Originally Posted by sayemthree

consensus seems to be that SMG was better on the track then street. DCT is better on the street than the track.

I would personally prefer a much better street gearbox with a less than perfect track record than the other way round.

[SteelTorque]

So M-DCT sucking ass on the track?

Well, my friend with his M3 DCT will be hitting the track this Wednesday. I will check with his to see if he has the same problem.

[Gearhead999s]

Originally Posted by sayemthree

consensus seems to be that SMG was better on the track then street. DCT is better on the street than the track.

This is what I have been saying all along.I had the same issue with my wifes DSG GTI on track and I guess its inconsistancy in downshifting under braking on track was also related to its ABS operation.At least with my 6 speed M/T M3 i can select the gear I want when I need it.

[sayemthree]

Originally Posted by footie

I would personally prefer a much better street gearbox with a less than perfect track record than the other way round.

well since I track a lot - I prefer one that does BOTH well.....MT!

[enigma]

I ran into some problems at the autocross doing 3->2 downshifts. I have the camera and data logger in the car but have not had a chance to look at the data yet. Will post details once I procees the data.

[skierman64]

Originally Posted by sayemthree

consensus seems to be that SMG was better on the track then street. DCT is better on the street than the track.

DCT is better than SMG on the street, however it's way to early to call regarding DCT on the track, there's only been one or two instances of DCT problems on the track.

No consensus yet, due to not enough data.

[swamp2]

Originally Posted by skierman64

DCT is better than SMG on the street, however it's way to early to call regarding DCT on the track, there's only been one or two instances of DCT problems on the track.

No consensus yet, due to not enough data.

Enigma has reported problems on the 3->2 downshift on the track as well. Ugh.

[bmwwr250f]

Great report, thanks for the information. I guess I just have not pushed hard enough on my canyon runs yet to experience this (I have pushed pretty hard). Do report this to your dealer and insist that they report it to BMW (as it is very likely they will be unable to reproduce the issue).

@bmwwr250f: Good explanation, sounds like you are on track but also you must admit you are doing a fair amount of speculation here. Your explanation does not account for why this seems to occur only on one particular downshift.

This occurs mostly due to the fact of how you are coming into the corner during downshifting(i.e large steering angle input,heavy brake application,the vehicle already sliding,ect.). The DCT control unit takes into account a variety of the power train sensors from the PT-CAN and F-CAN to make the calculations that will maintain control of the vehicle under extreme conditions. This occurs even with DSC disabled. You can still over drive the vehicle and lose control, but this is one way that is used to give the driver the best chance of regaining control during such a situation. This can happen even on up shifts, get the vehicle completely sideways drifting and try to upshift. It won't let you shift until the vehicle is back under control, otherwise it would just be another spin out. The DCT trans is a great attribute to the vehicle, compared to earlier smg2 and 3 versions that actually used a manual transmission modified for paddle shift use. The twin input shaft system used on the M3 is by far the best out there. The car already knows what gear the driver wants next before even pulling the paddle. The gear is already engaged before the paddle is pulled. This is all done from inputs from the rest of the powertrain control units and calculations made by the DCT control unit. Hopefully this helps out.

[Gearhead999s]

Originally Posted by bmwwr250f

This occurs mostly due to the fact of how you are coming into the corner during downshifting(i.e large steering angle input,heavy brake application,the vehicle already sliding,ect.). The DCT control unit takes into account a variety of the power train sensors from the PT-CAN and F-CAN to make the calculations that will maintain control of the vehicle under extreme conditions. This occurs even with DSC disabled. You can still over drive the vehicle and lose control, but this is one way that is used to give the driver the best chance of regaining control during such a situation. This can happen even on up shifts, get the vehicle completely sideways drifting and try to upshift. It won't let you shift until the vehicle is back under control, otherwise it would just be another spin out. The DCT trans is a great attribute to the vehicle, compared to earlier smg2 and 3 versions that actually used a manual transmission modified for paddle shift use. The twin input shaft system used on the M3 is by far the best out there. The car already knows what gear the driver wants next before even pulling the paddle. The gear is already engaged before the paddle is pulled. This is all done from inputs from the rest of the powertrain control units and calculations made by the DCT control unit. Hopefully this helps out.

Being able to shift up or down while in a slide is a very elemental part of advanced car control and to have this ability taken away in my opinion is a very bad thing.They have dumbed this system down so much that even the most unskilled drivers will have a tough time getting into trouble.I am very disapointed by this as my intention was to get a M-DCT car to replace my 6 speed car once the availability was OK,but I think with what I am hearing my 6 speed is a much better choice for the few track days I do a year.

[skierman64]

Originally Posted by swamp2

Enigma has reported problems on the 3->2 downshift on the track as well. Ugh.

That's two

Originally Posted by Gearhead999s

Being able to shift up or down while in a slide is a very elemental part of advanced car control and to have this ability taken away in my opinion is a very bad thing.They have dumbed this system down so much that even the most unskilled drivers will have a tough time getting into trouble.I am very disapointed by this as my intention was to get a M-DCT car to replace my 6 speed car once the availability was OK,but I think with what I am hearing my 6 speed is a much better choice for the few track days I do a year.

I think it's still too early to call. I have a track event coming up in August, I plan to video each session, that way I can share with everyone the DCT on track experience. I can't wait to report back.


Any chance different S modes effect the downshift ability at all.

[swamp2]

Originally Posted by bmwwr250f

This occurs mostly due to the fact of how you are coming into the corner during downshifting(i.e large steering angle input,heavy brake application,the vehicle already sliding,ect.). The DCT control unit takes into account a variety of the power train sensors from the PT-CAN and F-CAN to make the calculations that will maintain control of the vehicle under extreme conditions. This occurs even with DSC disabled. You can still over drive the vehicle and lose control, but this is one way that is used to give the driver the best chance of regaining control during such a situation. This can happen even on up shifts, get the vehicle completely sideways drifting and try to upshift. It won't let you shift until the vehicle is back under control, otherwise it would just be another spin out. The DCT trans is a great attribute to the vehicle, compared to earlier smg2 and 3 versions that actually used a manual transmission modified for paddle shift use. The twin input shaft system used on the M3 is by far the best out there. The car already knows what gear the driver wants next before even pulling the paddle. The gear is already engaged before the paddle is pulled. This is all done from inputs from the rest of the powertrain control units and calculations made by the DCT control unit. Hopefully this helps out.

I like many of your posts, well thought out and lots of details. However, they also seem VERY HEAVY on the speculation. The information you posted above is simply not any that just any old consumer can get a hold of. So if you are guessing you should say so. My conclusion is 1. You are purely speculating, 2. You know someone inside BMW directly involved with M-DCT. These really are the only two possibilities. So don't get me wrong speculation is good and useful but you should mention it.

[enigma]

Originally Posted by bmwwr250f

This occurs mostly due to the fact of how you are coming into the corner during downshifting(i.e large steering angle input,heavy brake application,the vehicle already sliding,ect.). The DCT control unit takes into account a variety of the power train sensors from the PT-CAN and F-CAN to make the calculations that will maintain control of the vehicle under extreme conditions. This occurs even with DSC disabled. You can still over drive the vehicle and lose control, but this is one way that is used to give the driver the best chance of regaining control during such a situation.

I hope this is speculation, if not then its defective by design. There was no pending loss of control when I was driving. Yes I rotated the car hard then hit the brakes hard enough to engage the ABS, so what. The car was under control and I asked for 2nd gear. Thats the end of it, it either gives me 2nd or its broken.

The put an off switch on DSC for a reason. Its to let experienced drivers do maneuvers under safe conditions that would normally be considered "out of control".

[footie]

swamp,

I like speculation, I personally use it a lot.

Enimga,

This could be another case of the new M3's role having shifted from pure road racer to a more luxury everyday replacement with a fair bit of sportiness thrown in for good measure.

P.S.
That's another bit of speculation.

[Gearhead999s]

Originally Posted by footie

swamp,

I like speculation, I personally use it a lot.

Enimga,

This could be another case of the new M3's role having shifted from pure road racer to a more luxury everyday replacement with a fair bit of sportiness thrown in for good measure.

P.S.
That's another bit of speculation.

I think its a case of BMW trying to reduce liability for both vehicle warranty and personal claims and that is total speculation on my part

[swamp2]

Originally Posted by enigma

I hope this is speculation, if not then its defective by design. There was no pending loss of control when I was driving. Yes I rotated the car hard then hit the brakes hard enough to engage the ABS, so what. The car was under control and I asked for 2nd gear. Thats the end of it, it either gives me 2nd or its broken.

The put an off switch on DSC for a reason. Its to let experienced drivers do maneuvers under safe conditions that would normally be considered "out of control".

No bueno...

-DSC: On, off or M?
-Drivelogic mode?
-Differences if this behavior based on the above?

[enigma]

Originally Posted by swamp2

No bueno...

-DSC: On, off or M?
-Drivelogic mode?
-Differences if this behavior based on the above?

DSC off. I tried M, it sucked dead bunnies through a straw... Way to intrusive.

S6 when I had the problems.
I used D5 later for my best time.

I didn't try the lower S modes.


I should be specific. By problem was not an ignored shift. 3 times when I attempted to downshift from 3->2 it went into 6th or 7th instead.

[hakaida442]

Originally Posted by enigma

DSC off. I tried M, it sucked dead bunnies through a straw... Way to intrusive.

S6 when I had the problems.
I used D5 later for my best time.

I didn't try the lower S modes.


I should be specific. By problem was not an ignored shift. 3 times when I attempted to downshift from 3->2 it went into 6th or 7th instead.

That sounds horrible. I hope that this can be fixed with a software update.

[T Bone]

Originally Posted by enigma

DSC off. I tried M, it sucked dead bunnies through a straw... Way to intrusive.

S6 when I had the problems.
I used D5 later for my best time.

I didn't try the lower S modes.


I should be specific. By problem was not an ignored shift. 3 times when I attempted to downshift from 3->2 it went into 6th or 7th instead.

Out of curiousity where were you in the rev range when you tried 3 -> 2?

I wonder if this is BMW trying to protect the drivetrain? (see the BMW USA disaster in the M5 6MT and no DSC off initially)

[swamp2]

Originally Posted by enigma

DSC off. I tried M, it sucked dead bunnies through a straw... Way to intrusive.

S6 when I had the problems.
I used D5 later for my best time.

I didn't try the lower S modes.


I should be specific. By problem was not an ignored shift. 3 times when I attempted to downshift from 3->2 it went into 6th or 7th instead.

Wow even worse than no shift, you get the wrong freaking gear.

Although I have not been a the track yet, I'm still waiting for a M-DCT TCU software update. Good luck trying to get you local service guy to listen. Let us know with an update if they will take a report. Take them out and scare the s%^$ out of them if they won't!

[Mickb]

Originally Posted by bmwwr250f

This occurs mostly due to the fact of how you are coming into the corner during downshifting(i.e large steering angle input,heavy brake application,the vehicle already sliding,ect.). The DCT control unit takes into account a variety of the power train sensors from the PT-CAN and F-CAN to make the calculations that will maintain control of the vehicle under extreme conditions. This occurs even with DSC disabled. You can still over drive the vehicle and lose control, but this is one way that is used to give the driver the best chance of regaining control during such a situation. This can happen even on up shifts, get the vehicle completely sideways drifting and try to upshift. It won't let you shift until the vehicle is back under control, otherwise it would just be another spin out. The DCT trans is a great attribute to the vehicle, compared to earlier smg2 and 3 versions that actually used a manual transmission modified for paddle shift use. The twin input shaft system used on the M3 is by far the best out there. The car already knows what gear the driver wants next before even pulling the paddle. The gear is already engaged before the paddle is pulled. This is all done from inputs from the rest of the powertrain control units and calculations made by the DCT control unit. Hopefully this helps out.

A lot of speculation here I'm afraid. Just in case I wasn't clear in my initial posts, the failure to downshift occurred during heavy braking and on the straights, i.e. before I had put any steering angle on the car or turned in. I always have my cornering gear selected before turning in, so this wasn't a case of the car trying to prevent a potentially troublesome downshift during a turn. If you have some inside knowledge on this then great, but I really feel the system is potentially fatally flawed if it won't allow a downshift on a straight during heavy braking.

Secondly, I had no problem upshifting during long drifts transitioning from 2nd to 3rd gear.

Finally, I find it kind of ironic that the BMW promo video that we all saw before the DCT was available made a huge amount of its ability to shift during cornering causing no loss of momentum or balance to the vehicle. If they have now engineered in this "safey" facility that would be pretty sad IMO.

I could understand it if they left this in on certain modes, but it should be possible for the driver to communicate to the vehicle that "YES I WANT FULL MANUAL CONTROL EVEN IF THIS CAUSES VEHICLE INSTABILITY".........restrict it to S6/DSC off if you will but teh current situation is unacceptable IMO.

[Mickb]

Originally Posted by T Bone

Out of curiousity where were you in the rev range when you tried 3 -> 2?

I wonder if this is BMW trying to protect the drivetrain? (see the BMW USA disaster in the M5 6MT and no DSC off initially)

Shouldnt be really......I mean the computer can rev match more perfectly than any human so drivetrain shock shouldnt be an issue. Also, I have experienced the problem in situations where I had a friend watching my rev counter to make sure it wasn't just the computer preventing a money shift (which it will).

Mick