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      07-31-2007, 04:05 PM   #1
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Why is BMW going away from SMG? Why does the press/others dislike SMG, but Love DSG?

I don't understand why the press & others don't love the SMG? I test drove an M3 one a year ago & I absolutely LOVED it!!! The 2006 M brochure says in the most aggressive setting (S6) it has 80-millisecond shifts, isn't that faster than Ferraris 100-milliseconds? In fairness I've never driven a DSG, is it that much better?
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      07-31-2007, 04:54 PM   #2
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DSG uses twin clutches, one on the even gears, the other on the odd gears, and is optimized for upshifting under power. Upshifts take 8 ms. Down shifts, 600 ms.

http://www.autozine.org/technical_sc...ear_manual.htm
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      07-31-2007, 05:03 PM   #3
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Quote:
Originally Posted by RI_RS4 View Post
DSG uses twin clutches, one on the even gears, the other on the odd gears, and is optimized for upshifting under power. Upshifts take 8 ms. Down shifts, 600 ms.

http://www.autozine.org/technical_sc...ear_manual.htm
I cannot recall the source, but I do recall reading somewhere that the M version of the DCT will not be handicapped with the same "long" downshift time that existing DCT units have. I think the reason for this is that the M DCT will combine the SMG technology with the DCT concept.
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      07-31-2007, 05:24 PM   #4
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Because SMG is hard to shift smoothly. DSG will have the smoothness of a slushbox, but with the benefit of lighting fast, controllable shifts.
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      07-31-2007, 05:35 PM   #5
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SMG vs. DCT

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Originally Posted by Lex View Post
I don't understand why the press & others don't love the SMG? I test drove an M3 one a year ago & I absolutely LOVED it!!! The 2006 M brochure says in the most aggressive setting (S6) it has 80-millisecond shifts, isn't that faster than Ferraris 100-milliseconds? In fairness I've never driven a DSG, is it that much better?
Aside from the slightly better potential maximum performance, many bought SMG expecting it to act like a conventional auto tranny and were disappointed with the smoothness in this mode. I think DCT is largely in response to that.
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      07-31-2007, 05:37 PM   #6
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Down shifts

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Originally Posted by RI_RS4 View Post
DSG uses twin clutches, one on the even gears, the other on the odd gears, and is optimized for upshifting under power. Upshifts take 8 ms. Down shifts, 600 ms.

http://www.autozine.org/technical_sc...ear_manual.htm
Good reference. I have yet to see a quote for downshift times and the actual penalty for distant downshifts. I do suspect that BMW will improve on these numbers a bit, but then again if you have to wait for the blip, maybe it is irrelevant. Either way the 600 adn 900 ms times are simply limited by how fast the clutch and gear shift movements can occur. It would be interesting to compare these figures to SMG II downshifts. Anyone have that data?
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      07-31-2007, 05:48 PM   #7
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Quote:
Originally Posted by RI_RS4 View Post
DSG uses twin clutches, one on the even gears, the other on the odd gears, and is optimized for upshifting under power. Upshifts take 8 ms. Down shifts, 600 ms.

http://www.autozine.org/technical_sc...ear_manual.htm
Thanks for the link. Holy Shi* 8 milliseconds, but down shifts of 600 milliseconds, thats gotta hurt on the twisties. It will be interesting what BMW does with the new one,
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      07-31-2007, 07:45 PM   #8
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Quote:
Originally Posted by RI_RS4 View Post
Now that is informative.

Yikes:

"Changing down a few gears could be more complicated. The most complicated is from 6th to 2nd (both are controlled by the same clutch while the distance between the two gears is the longest). It needs to change to 5th (controlled by another clutch) temporarily before 2nd is selected. This takes 900ms."
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      07-31-2007, 07:58 PM   #9
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Importance

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Originally Posted by Epacy View Post
Now that is informative.

Yikes:

"Changing down a few gears could be more complicated. The most complicated is from 6th to 2nd (both are controlled by the same clutch while the distance between the two gears is the longest). It needs to change to 5th (controlled by another clutch) temporarily before 2nd is selected. This takes 900ms."
My bets are the BMW system is better. That may be a bit "fan boy" but isn't it what we generally expect and get from BMW (well, Getrag, working for BMW...). Also the importance of very fast shift with basically uninterrupted power to the wheels while accelerating is obvious. How much need it there for 8ms shifts when downshifting?
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      07-31-2007, 08:00 PM   #10
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Quote:
Originally Posted by Epacy View Post
"Changing down a few gears could be more complicated. The most complicated is from 6th to 2nd (both are controlled by the same clutch while the distance between the two gears is the longest). It needs to change to 5th (controlled by another clutch) temporarily before 2nd is selected. This takes 900ms."
I wonder how many average drivers could accomplish a 6th to 2nd shift using a manual in 900ms using their most aggressive shift. I don't know if I'd be faster than the machine.
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      07-31-2007, 08:02 PM   #11
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Because DCT is FTW and SMG is FTL.
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      07-31-2007, 08:03 PM   #12
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In my opinion SMG systems were basically prototypes for what we are getting now with the MDCT/DSG.

Jason
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      07-31-2007, 08:30 PM   #13
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Quote:
Originally Posted by swamp2 View Post
the importance of very fast shift with basically uninterrupted power to the wheels while accelerating is obvious. How much need it there for 8ms shifts when downshifting?
Exactly. If you are going fast enough to warrant 6th gear, you wouldn't then downshift to 2nd gear in 8ms anyway, without over-revving it. Ideally you downshift thru every gear on the track. A more likely track situation would be topping out 4th gear, braking hard, and while you're braking you go thru 3rd, then 2nd.... Not 6th to 2nd...
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      07-31-2007, 08:59 PM   #14
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Quote:
Originally Posted by aerisolphaln View Post
I wonder how many average drivers could accomplish a 6th to 2nd shift using a manual in 900ms using their most aggressive shift. I don't know if I'd be faster than the machine.
How'd I know someone would bring that up? Leave it to you nonetheless.
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      07-31-2007, 09:02 PM   #15
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Quote:
Originally Posted by Hans Delbruck View Post
Exactly. If you are going fast enough to warrant 6th gear, you wouldn't then downshift to 2nd gear in 8ms anyway, without over-revving it. Ideally you downshift thru every gear on the track. A more likely track situation would be topping out 4th gear, braking hard, and while you're braking you go thru 3rd, then 2nd.... Not 6th to 2nd...
Well, the way you put it sounds like manually shifting. If you still go from 4 to 2, you are on the same even-sided cluth, which is the issue. Obvoiusly travel isn't as far.
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      07-31-2007, 09:26 PM   #16
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Quote:
Originally Posted by JEllis View Post
In my opinion SMG systems were basically prototypes for what we are getting now with the MDCT/DSG.

Jason
From my understanding this is not the case. SMG is essentially a standard manual box, mechatronically operated, which is the cause of the "slow" upshift. The DCT/DSG concept allows almost instantaneous sequential upshifts since the opposing clutches engage odd and even gears simultaneously.

Quote:
Originally Posted by Epacy View Post
Well, the way you put it sounds like manually shifting. If you still go from 4 to 2, you are on the same even-sided cluth, which is the issue. Obvoiusly travel isn't as far.
Agreed. 6-2 might take some justification, but a 4-2 is pretty normal in everyday driving. The throttle blip adds a bit more time in these situations. This appears to be one situation in which the "regenerative" braking is counter-intuitive.
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      07-31-2007, 10:23 PM   #17
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Quote:
Originally Posted by aerisolphaln View Post
I wonder how many average drivers could accomplish a 6th to 2nd shift using a manual in 900ms using their most aggressive shift. I don't know if I'd be faster than the machine.
With no braking - I'm fairly sure I could beat that.

With heel-toe braking? Forget about it. That's where DCT/SMG shine.
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      08-01-2007, 12:40 AM   #18
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It is not clear yet wich system should prevail, in Garching they said both, SMG and DSG, are curently being tested. It could be possible that BMW keeps both, but as I said, nothing is sure for now.......................we will have to wait en see..............................
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      08-01-2007, 12:49 AM   #19
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Seems like M-DCT for sure

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Originally Posted by Romo View Post
It is not clear yet wich system should prevail, in Garching they said both, SMG and DSG, are curently being tested. It could be possible that BMW keeps both, but as I said, nothing is sure for now.......................we will have to wait en see..............................
I guess you can not count your chickens before the eggs hatch...However, all of the press as well as "insider" information from BMW clearly points to one MT alternative for the M3 and that is M-DCT by Getrag. I got a private message the other day from a fellow who liked my simulation work on the M-DCT and claimed his friend is a test driver for BMW currently driving M-DCT cars and absolutely loves it. It seems it would be nearly impossible for BMW to back pedal and offer SMG on the car. All UK, EU, SA, etc. literature claims 6MT only, for now. M-DCT fits the "efficient dynamics" so perfect as well - better fuel consumption and better performance.
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      08-01-2007, 01:40 AM   #20
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Quote:
Originally Posted by Lex View Post
I don't understand why the press & others don't love the SMG? I test drove an M3 one a year ago & I absolutely LOVED it!!! The 2006 M brochure says in the most aggressive setting (S6) it has 80-millisecond shifts, isn't that faster than Ferraris 100-milliseconds? In fairness I've never driven a DSG, is it that much better?

I have had both a SMG and a DSG fitted car. My M3 with SMG was great and I loved every minute of driving it! My TT with DSG plain and simply sucked big time! I also can’t understand why the DSG system gets such good reviews. I am confident that the new BMW system will be good.
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      08-01-2007, 02:53 AM   #21
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Quote:
Originally Posted by 888 View Post
I have had both a SMG and a DSG fitted car. My M3 with SMG was great and I loved every minute of driving it! My TT with DSG plain and simply sucked big time! I also can’t understand why the DSG system gets such good reviews. I am confident that the new BMW system will be good.
what was the main issues with the TT dsg? interested as my order is with M-dct.
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      08-01-2007, 05:45 AM   #22
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what was the main issues with the TT dsg? interested as my order is with M-dct.
I did not feel “connected” to the car. Up shifts are nearly seamless and downshifts could get confused. I loved the “crisp” responsive feel that the SMG offered. At first I did not like my SMG and I nearly took it back to BMW. After a few days you start to learn how the box works and you start interacting with it like it has its own soul. The DSG on the other hand was always just bland. Passengers however preferred the DSG.

This highlights the dangers of both car reviews and short test drives. I guess the DSG gets rave reviews because it is so versatile, the SMG on the other hand is bad in auto mode (which I never used).

I assume that the M division won’t make a box that is not suited to an M car.

A friend of mine bought his wife a SMG M3 and she absolutely hated it.

When I attended the M high speed driving course my instructor loved the SMG.

I also want the M-dct, but because I am high on the list I will take a Mt for now.

I hope my coments helped.
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