DCT behavior question

[ihyln]

I'm wondering if the following is normal... In S5 while I'm on an on-ramp I'm not depressing the pedal entirely but lightly enough to get the engine going in a hurry (not in kickdown mode either). As I shift I was getting soft jerks but I'm not getting it anymore (or at least noticing now, I'll check again tomorrow)

I don't get any soft jerks of any sort in any of the D modes. I don't feel them in S1-4 either.

Anything to worry about or is the tranny breaking in normally?

[nusevad]

Yea its suppose to tug when you shift in S5. Its normal.

[ybbiz34]

The other day when I was test driving a DCT equipped car, I was driving the car in manual mode (if this has another name I apologize, as I am not quite up to par on the DCT proper terminology) and I was sitting at a stoplight in first gear. The throttle was in its most aggressive setting (I had recently just pushed the M button), and I hit the gas casually and before shifting to second I lifted up off of the pedal a bit and the car began to jerk back and forth rather violently, and the situation became increasingly complicated/worse as my foot would tap the gas again slightly as a result of the jerking. After getting rocked back and forth for a couple of seconds I finally was able to grab a shift into second gear. Needless to say, I felt like a jackass. Has anyone else experienced this, or can anyone comment on what that was all about? Was it all just a matter of throttle sensitivity or a flaw with the transmission?

[ihyln]

Phew, Thanks Dave! I was getting concerned. I just took it out for a spin on to a few on-ramps to double check and yup it's there. It's a good way to flatten your kidneys.

ybbiz32, it happens to me in first but not as violent as you had mentioned. It's a result of not keeping steady on the gas but when you have the Power button on it can get like that. I've learned just to keep a light foot in first coming off a red light.

[ybbiz34]

Originally Posted by ihyln

ybbiz32, it happens to me in first but not as violent as you had mentioned. It's a result of not keeping steady on the gas but when you have the Power button on it can get like that. I've learned just to keep a light foot in first coming off a red light.

Yeah that makes sense. That's what I figured was the problem. Good to know from now on.

[nusevad]

Originally Posted by ihyln

Phew, Thanks Dave! I was getting concerned. I just took it out for a spin on to a few on-ramps to double check and yup it's there. It's a good way to flatten your kidneys.

No problem Shaf.

I was concerned at first too, since i was used to driving in D1-4, when i first tried S5 i was like whoa...whats this tug. I like it, the feel of the kick during spirited driving is great.

[nusevad]

Originally Posted by ybbiz34

The other day when I was test driving a DCT equipped car, I was driving the car in manual mode (if this has another name I apologize, as I am not quite up to par on the DCT proper terminology) and I was sitting at a stoplight in first gear. The throttle was in its most aggressive setting (I had recently just pushed the M button), and I hit the gas casually and before shifting to second I lifted up off of the pedal a bit and the car began to jerk back and forth rather violently, and the situation became increasingly complicated/worse as my foot would tap the gas again slightly as a result of the jerking. After getting rocked back and forth for a couple of seconds I finally was able to grab a shift into second gear. Needless to say, I felt like a jackass. Has anyone else experienced this, or can anyone comment on what that was all about? Was it all just a matter of throttle sensitivity or a flaw with the transmission?

throttle sensitivity. First gear is rather short so if you let off the trottle at 3-4k rpms and quickly step on it again its going to jerk a bit esp. since you have sport on.

[skierman64]

Try full throttle in S5 and see how that feels. The higher rpm the shift the bigger the jerk will be.

[skierman64]

Originally Posted by ybbiz34

The other day when I was test driving a DCT equipped car, I was driving the car in manual mode (if this has another name I apologize, as I am not quite up to par on the DCT proper terminology) and I was sitting at a stoplight in first gear. The throttle was in its most aggressive setting (I had recently just pushed the M button), and I hit the gas casually and before shifting to second I lifted up off of the pedal a bit and the car began to jerk back and forth rather violently, and the situation became increasingly complicated/worse as my foot would tap the gas again slightly as a result of the jerking. After getting rocked back and forth for a couple of seconds I finally was able to grab a shift into second gear. Needless to say, I felt like a jackass. Has anyone else experienced this, or can anyone comment on what that was all about? Was it all just a matter of throttle sensitivity or a flaw with the transmission?

Driver induced oscillations. The throttle pedal is sensitive. Putting your foot lightly against the transmission tunnel while pressing the accelerator (center console) will help prevent that as your accelerating briskly.

I had the same thing happen to me twice the first week I owned the car, but it hasn't happened since.

[darkalley]

Originally Posted by ybbiz34

The other day when I was test driving a DCT equipped car, I was driving the car in manual mode (if this has another name I apologize, as I am not quite up to par on the DCT proper terminology) and I was sitting at a stoplight in first gear. The throttle was in its most aggressive setting (I had recently just pushed the M button), and I hit the gas casually and before shifting to second I lifted up off of the pedal a bit and the car began to jerk back and forth rather violently, and the situation became increasingly complicated/worse as my foot would tap the gas again slightly as a result of the jerking. After getting rocked back and forth for a couple of seconds I finally was able to grab a shift into second gear. Needless to say, I felt like a jackass. Has anyone else experienced this, or can anyone comment on what that was all about? Was it all just a matter of throttle sensitivity or a flaw with the transmission?

In my smg car that would happen about once a week. in my dct it seems like once a month. the dct can, in rare occasions, become a little confused. in the smg it was called "bucking bronco". not sure if we will be bringing that over to DCT. Happens in f1 ferraris, e-gear lambos, etc. nothing to be worried about. 2000 miles on my dct and it is incredible.

[ybbiz34]

Originally Posted by skierman64

Driver induced oscillations. The throttle pedal is sensitive. Putting your foot lightly against the transmission tunnel while pressing the accelerator (center console) will help prevent that as your accelerating briskly.

I had the same thing happen to me twice the first week I owned the car, but it hasn't happened since.

Originally Posted by FifthStreetz

throttle sensitivity. First gear is rather short so if you let off the trottle at 3-4k rpms and quickly step on it again its going to jerk a bit esp. since you have sport on.

Originally Posted by darkalley

In my smg car that would happen about once a week. in my dct it seems like once a month. the dct can, in rare occasions, become a little confused. in the smg it was called "bucking bronco". not sure if we will be bringing that over to DCT. Happens in f1 ferraris, e-gear lambos, etc. nothing to be worried about. 2000 miles on my dct and it is incredible.

Thanks for all of the responses and information guys. It is good to know I'm not the only one who has had that little experience. Aside from this error caused by my unfamiliarity with the transmission, and as I mentioned in my other thread, I was floored by the DCT. Remarkable transmission.

[e46e92love]

Originally Posted by FifthStreetz

No problem Shaf.

I was concerned at first too, since i was used to driving in D1-4, when i first tried S5 i was like whoa...whats this tug. I like it, the feel of the kick during spirited driving is great.

Just felt that tug for the first time today (THANK skierman64 ) and its awesome.......

[JEllis]

Yep that sensitive throttle will get you every time!

Jason

[ferrari6891]

but how can you fix it because it happened to me just as I was about to race an S4....and the audi just left me in the dust because it started jerking violently...and if I go on the throttle slowly..theres no way i can win a race

[swamp2]

The OP is talking about jerk (actually a mathematical term - the time derivative of acceleration). BMW calls this feeling surge. Humans are more sensitive to jerk than raw acceleration levels, i.e. the change in acceleration (typically over a short duration). There has been extensive discussion and debate on this topic all over the forum. Surge is both Drivelogic mode and rpm dependent. No modes but S4, S5 and S6 have surge and it is greater in each mode. As well the higher the rpm of the shift and the more you are on the pedal the more you will feel the surge. Surge will also be so high in S5 and S6 to lead to wheelspin and/or "chirp" when at very high throttle and high rpm shifts.

[DonM3]

This has happened to me on many occasions...

The violent jerking makes you look like a real idiot

Originally Posted by ferrari6891

but how can you fix it because it happened to me just as I was about to race an S4....and the audi just left me in the dust because it started jerking violently...and if I go on the throttle slowly..theres no way i can win a race

[Powerslide]

Originally Posted by DonM3

This has happened to me on many occasions...

The violent jerking makes you look like a real idiot

Has anyone heard whether this will be addressed with the Sept. 2008 software upgrade for M DCT equipped cars, or is this just an inherent characteristic of the transmission? It happens to me under similar circumstances referenced in the preceeding posts, about 1-2 times out of 10 while accelerating aggressively from a red light - sounds like it most likely is induced by starting out heavy on the accelerator and then easing off the throttle somewhat - followed by the "bucking bronco" or violent jerking back and forth...

[Dascamel]

Its the same in other cars, tons of power, going off and on again with the throttle will create it everytime. If your not pushing it, just start in 2nd gear.

[cchan]

The bucking bronco can happen in any car with a clutch. With an MT, you can disengage the clutch to stop it and let things settle down. In an SMG car, the best thing to do was upshift. Don't know if that will help in DCT though.

[Powerslide]

Originally Posted by cchan

The bucking bronco can happen in any car with a clutch. With an MT, you can disengage the clutch to stop it and let things settle down. In an SMG car, the best thing to do was upshift. Don't know if that will help in DCT though.

Now that you mention that, I have noticed that upshifting helps - the bucking bronco immediately goes away...

[footie]

Originally Posted by swamp2

The OP is talking about jerk (actually a mathematical term - the time derivative of acceleration). BMW calls this feeling surge. Humans are more sensitive to jerk than raw acceleration levels, i.e. the change in acceleration (typically over a short duration). There has been extensive discussion and debate on this topic all over the forum. Surge is both Drivelogic mode and rpm dependent. No modes but S4, S5 and S6 have surge and it is greater in each mode. As well the higher the rpm of the shift and the more you are on the pedal the more you will feel the surge. Surge will also be so high in S5 and S6 to lead to wheelspin and/or "chirp" when at very high throttle and high rpm shifts.

I read in one of the British mags that S5's surge felt slightly stronger than S6, is this true or do both felt about the same?