M-DCT Semantics and Subtleties

[voodoogeek]

so what about the carwash with comfort access? I put lever to N, stop the engine with brake pedal depressed and exit the car for it to get washed. does it now jump back to P, or perhaps after some idle time, say 10 minutes (auto-lock feature dunno)?

I am quite reluctant taking the car to a car wash now...

[castilla]

I read something about DCT.It says ,to move the car you must press gas pedal , releasing your foot from brake pedal is not moving car .. is that true ??

[CanAutM3]

Originally Posted by castilla

I read something about DCT.It says ,to move the car you must press gas pedal , releasing your foot from brake pedal is not moving car .. is that true ??

True.

M-DCT is programmed without "creep" when you release the brake. You need to press the gas pedal for the clutch to engage. This was done to mimic the behavior of a manual transmission rather than a conventional automatic. On non-///M cars with DCT, the DCT does creep when the brake is released to behave as a standard auto box .

[kinimod]

Question:

When you hold the brake pedal uphill or downhill, the car won't start rolling immediately. It takes maybe 2 seconds, as if the clutch was engaged by default and it only disengages after releasing the brake pedal.

Is that so? Is the DCT clutch engaged when standing still in 1st or 2nd gear and holding the brake pedal?

[Blksnowflake]

What you're referring to is what I believe is hill assist. Mostly all modern cars come with some form of this even manual as well as DCT cars.

[kinimod]

Originally Posted by Blksnowflake

What you're referring to is what I believe is hill assist. Mostly all modern cars come with some form of this even manual as well as DCT cars.

Makes sense, so I'm curious then how the clutch works when standing still on a flat, level surface and accelerating from a full stop.

Is it always engaged, or only engages when pressing on the throttle?

[Algol]

Originally Posted by kinimod

Makes sense, so I'm curious then how the clutch works when standing still on a flat, level surface and accelerating from a full stop.

Is it always engaged, or only engages when pressing on the throttle?

Only when pressing the throttle will the clutches engage. You can feel the clutches slip and grab easily if you apply 30-50% throttle from a stop in comfort mode.

[robg]

-What is it's behavior like in stop and go traffic?
-Does it always start in 1st, or is there a mode where it will start in 2nd (and not downshift to 1st)?
-Given that there's no "creep", and you dont have a clutch pedal to modulate, how jerky is it?
-How smooth is the 1->2 upshift in the 3 transmission modes? (and in auto vs manual modes)

To ask in a simpler way, if you leave the car in auto and the trans in the slowest mode what does it feel like in heavy traffic? Is it annoying?

Would also be interested in perspectives from those who have owned a ZF8 equipped BMW and how the DCT compares in these situations.

[e90post_user]

I own a six-speed car, and drove a DCT equipped M4 recently - I couldn't tell it apart from a conventional automatic transmission in the scenario you mentioned above.

[JonnyM3]

It's smooth in my E90, partly why I never have driven it in auto, but others have. Only thing that separates it from a traditional auto is it won't move at a stop when releasing the brakes and clutch engaging when first beginning to move. I can see this being new to some, but not a deal breaker for anyone. In short the tranny is smooth, way smooth in all given scenarios.

[Yeoman]

The only time it's "jerky" is when the DCT and throttle response are in the most aggressive modes.. otherwise you won't be able to tell it apart from a conventional auto aside from the much faster shifts.. you can start it off in 2nd if it's in manual mode.

[khaye1]

you're wife will be fine...just set everything to the lowest setting and it's smooth as butter.

my only complaint is when you put it on reverse then drive, there's a significant lag!

[JeffM-Houston]

-What is it's behavior like in stop and go traffic?

Just fine

-Does it always start in 1st, or is there a mode where it will start in 2nd (and not downshift to 1st)?

If you haven't come to an absolute stop and then ease on the gas it will stay in 2nd.

-Given that there's no "creep", and you dont have a clutch pedal to modulate, how jerky is it?

Not at all jerky.

-How smooth is the 1->2 upshift in the 3 transmission modes? (and in auto vs manual modes)

On the street I usually use comfort mode, shift is very smooth from 1-2, you won't notice any difference to a regular automatic. I sometimes use the middle position for tranny and that is a little faster but still doesn't jerk at all.

[WVUDrJay]

[QUOTE=khaye1;17428315]you're wife will be fine...just don't let her drive it!

Fixed for you.

[robg]

Originally Posted by JeffM-Houston

-What is it's behavior like in stop and go traffic?

Just fine

-Does it always start in 1st, or is there a mode where it will start in 2nd (and not downshift to 1st)?

If you haven't come to an absolute stop and then ease on the gas it will stay in 2nd.

-Given that there's no "creep", and you dont have a clutch pedal to modulate, how jerky is it?

Not at all jerky.

-How smooth is the 1->2 upshift in the 3 transmission modes? (and in auto vs manual modes)

On the street I usually use comfort mode, shift is very smooth from 1-2, you won't notice any difference to a regular automatic. I sometimes use the middle position for tranny and that is a little faster but still doesn't jerk at all.

Thanks!

So regarding coming to a complete stop-- I'm glad to hear it waits until being completely stopped before shifting to 1st.

And I understand that you can, of course, click the paddle shifter to 2nd and force it to start out in 2nd when starting from a stand still. But just wondering - when you're in automatic mode, will any of the trans modes cause it start out in 2nd all the time?


(I know these seem like very nit picky questions, but I have a BMW with a regular ZF8 auto currently and it actually drives me nuts in stop and go traffic with its insistence on starting in 1st and dwonshifting to 1st at 5mph. Kind of want to toss it out a window. I'm not at all concerned about the m3 in higher performance situations but am curious how it does in these annoying everyday type situations)

[khaye1]

[QUOTE=WVUDrJay;17428346]

Originally Posted by khaye1

you're wife will be fine...just don't let her drive it!

Fixed for you.

that's good

[mkoesel]

Originally Posted by robg

And I understand that you can, of course, click the paddle shifter to 2nd and force it to start out in 2nd when starting from a stand still. But just wondering - when you're in automatic mode, will any of the trans modes cause it start out in 2nd all the time?

I believe it will do this in D1. I don't use D mode so I won't guarantee it, but I think this is the case.

[Rick955]

I had lots of questions too, also using the ZF8 now... this thread helped quite a bit, especially posts on the last few pages...
http://f80.bimmerpost.com/forums/sho....php?t=1090537

[robg]

Originally Posted by Rick955

I had lots of questions too, also using the ZF8 now... this thread helped quite a bit, especially posts on the last few pages...
http://f80.bimmerpost.com/forums/sho....php?t=1090537

Thanks! That was an interesting thread. A few take-aways I got from that:
-Reminded me that the M3/4 allow you to choose steering, suspension, shift speed and throttle mapping separately. On regular BMWs, it's all bundled together in the various driving modes for the most part. Combined with the steering wheel presets on the Ms it makes it easy to have a "stop and go traffic" mode with the settings that work best, and a "backroads mode". I tend to hate non-linear "sport" throttle mappings and unncessarily fast/jerky transmission shift speeds, but like firmer steering and sometimes firmer shocks. So it gives me that flexibily.

-Sounds like the DCT is actually less aggressive about downshifting as you're coming to a stop than the ZF8..which is great. Regardless of mode, it sounds like it will never downshift to 1st while rolling-- only from a stop. If I had a manual, i'd coast in neutral to come to a smooth stop (and never downshift to 1st either). Also, sounds like it is easier to pop it into neutral (as you would on a manual) if you prefer.

-Sounds like the car behaves consistently in terms of how it slips the clutch relative to throttle inputs from a start. So its possible to "learn" the transmission just as you would the clutch in a manual. the ZF8 behaves somewhat inconsistently in my experience which is partly what drives me nuts about it.


Funny thing is that I had an older 335 with the ZF6 plus paddles and thought it was great. the Much praised ZF8 drives me nuts by trying to be sporty. Glad the DCT doesnt share its silly programming.

[Rick955]

Originally Posted by robg

Thanks! That was an interesting thread. A few take-aways I got from that:
-Reminded me that the M3/4 allow you to choose steering, suspension, shift speed and throttle mapping separately. On regular BMWs, it's all bundled together in the various driving modes for the most part. Combined with the steering wheel presets on the Ms it makes it easy to have a "stop and go traffic" mode with the settings that work best, and a "backroads mode". I tend to hate non-linear "sport" throttle mappings and unncessarily fast/jerky transmission shift speeds, but like firmer steering and sometimes firmer shocks. So it gives me that flexibily.

-Sounds like the DCT is actually less aggressive about downshifting as you're coming to a stop than the ZF8..which is great. Regardless of mode, it sounds like it will never downshift to 1st while rolling-- only from a stop. If I had a manual, i'd coast in neutral to come to a smooth stop (and never downshift to 1st either). Also, sounds like it is easier to pop it into neutral (as you would on a manual) if you prefer.

-Sounds like the car behaves consistently in terms of how it slips the clutch relative to throttle inputs from a start. So its possible to "learn" the transmission just as you would the clutch in a manual. the ZF8 behaves somewhat inconsistently in my experience which is partly what drives me nuts about it.


Funny thing is that I had an older 335 with the ZF6 plus paddles and thought it was great. the Much praised ZF8 drives me nuts by trying to be sporty. Glad the DCT doesnt share its silly programming.

Glad it helped. I'm going to be curious to see about that lack of a button for PARK. Seems to be a common complaint as it can be "fussy" if you don't do it right... not letting you lock the car, or it staying in N and rolling. Guess it's just another little thing you have to get used to.

[Giggity]

To the point about having a hard time getting the DCT into "park", i normally just put the trans in reverse and hit the start/stop button. Defaults to park every time.

[Rick955]

Originally Posted by Giggity

To the point about having a hard time getting the DCT into "park", i normally just put the trans in reverse and hit the start/stop button. Defaults to park every time.

Cool. Thanks!