SMG vs. DCT

TimK · Mar 4, 2009

I'm sure more informed member will eventually chime in but here's my .02 DCT should be superior in most ways. It is easier to drive smoothly around town, upshift and downshift even quicker (at least 1 gear anyway) and the auto mode is much more natural feeling than SMG's.
According to some SMG might have an advantage when shifting quickly across multiple gears, and the best part is the simultaneous kick in the back of the head and arse when shifting in S6 at wide open throttle. You definitely don't get that from DCT.
I also like the way SMG feels and sounds much more like a 3 pedal car when driven like one (easing off throttle before shifts)

Daytona Bones · Mar 4, 2009

TimK said:
DCT should be superior in most ways. It is easier to drive smoothly around town, upshift and downshift even quicker (at least 1 gear anyway) and the auto mode is much more natural feeling than SMG's.
According to some SMG might have an advantage when shifting quickly across multiple gears, and the best part is the simultaneous kick in the back of the head and arse when shifting in S6 at wide open throttle. You definitely don't get that from DCT.
I also like the way SMG feels and sounds much more like a 3 pedal car when driven like one (easing off throttle before shifts)

Well said... I do wonder what our car would feel like with the double clutch.

xraym5 · Mar 4, 2009

I have always been concerned that DCT does not have the "raw" manual feeling of SMG. While I might initially appreciate the smoothness and quickness of the shifting with DCT, I fear that I would quickly become bored with this transmission, ultimately feeling too refined for my tastes. Then again, I have never test driven a new M3 with DCT, so I will withhold final judgment.

Fahrenheit · Mar 4, 2009

xraym5 said:
I have always been concerned that DCT does not have the "raw" manual feeling of SMG.

I have driven the M3 DCT around the track on BMW Drive Days. The car feels practically like an automatic, and in D mode, you probably won't notice the difference. A BMW instructor even said to me he would NEVER drive the SMG III in D mode, but now, he often drives the DCT in D mode.

DCT lacks the raw feel of the SMGIII. SMGIII is more "involved", in the sense that you need to listen/feel the car more when you shift in Shift mode or Drive mode. My feeling is that when BMW designed the SMGIII, they partly wanted the "feel" of a traditional manual clutch preserved as much as possible, while giving us an engineering marvel. Then came the "critics" and other folks who hated the SMGIII because they did not physically see a clutch, thus expecting a smooth automatic type feel. Now BMW is reacting to this, thus dumping the SMGIII and moving on to DCT.

superlubricity · Mar 4, 2009

A great post on e60.net here -> Comparing the M5's SMG with M3's DCT - E60 Forums

A quote from that thread from member Filip535D:

Hi,

My wife has a M3 DCT and i have a M5 SMG.
The difference

M5 - 1 clutch - 1 transmission with 7 gears
M3 - 2 clutches - 2 transmissions with Left ( 1-3-5-7) and right ( 2-4-6)

When you shift in the M5, the gear has to be taken like with a manual transmission, 1 by 1.
With the M3 , every next gear is waiting to come in , so when you are driving in Second gear and you pull the paddle, the next gear immediatly is there without any delay, it's like with a scooter with a vario, the kick and sensation is much less with the M3 then with the M5. This because you don't have the bang that shakes your head by shifting ( hope this is understandable).
The only good difference for me is , when you do a kickdown in 7th gear with the M3 , you give 1 pull on the paddle and the gearbox is going to the best gear immediatly. With the M5 you have to pull several times to go 3 gears down.

I hope this gives an idea of the difference.

Greetings
Filip

AFC1 Discussion starter · Mar 4, 2009

Thank you everyone for your responses. this may be a false assumption but it seems to me that DCT is more likable (hence the raving reviews from magazines) but there are less people who genuinely love the DCT the way that many M5/M6 board members love the SMG. so, it seems that in making the DCT more approachable, BMW has also partially taken away the "soul" that came with the SMG

xraym5 · Mar 4, 2009

Perhaps history will repeat itself, and if enough people complain about DCT, SMG will be offered as an option, just like MT was offered with the E60 M5.

Now I hope I didn't cause Ashok's blood pressure to elevate. ouich

Murtaza · Mar 4, 2009

SMG is great when you're hauling *** but under normal driving conditions it's not so smooth. The length of shift times when not at redline are my main gripe. Shifts at 2-5k are sluggish in every shift setting. My AMG slushbox felt faster then these shifts.

In the end the positives outweigh the negatives for me, I love it! I do wonder how the DCT would perform and am sure it would be an overall improvement. The ferocity of S6 shifts would certainly be missed and I'm not sure how fast multiple downshifts are with DCT. I often go from 7th to 3rd on the highway...

stunt · Nov 20, 2010

Murtaza said:
The length of shift times when not at redline are my main gripe. Shifts at 2-5k are sluggish in every shift setting.

I have been wondering about this. I have a 02/06 build and have complained to my dealer a couple of times that in S6, shifts seem just as sluggish as when in any other s or d level setting, even at wot above 5k. wot shifts around 8k will only give me firm shifts 50% of the time on the 1-2 shift, and 75% of the time on the 203 shift. Kinda weird.

Dealer states everything is fine after checking for codes and doing a test drive. Personally I think my smg pump is weak.

I think I'll video what I'm talking about and post it to see if anyone else is experiencing this.

Sorry to stray off topic...

JonnybravoM3 · Mar 4, 2009

Ya thats so true -- it does bug me when you have to pull a few times to go 3 gears down if you wanna make a quick getaway in 7th gear! In that respect, the M3 DCT is preferable to me.

Other than that, i'm an SMG man all the way. (to be fair, I'm a 6MT man all the way but with the M6 i'm afraid I didn't have a choice! plus its more practical in traffic jams). Love the raw manual feel (my girlfriend doesn't like it much so when I take her out with me I turn the it down to S-1 as opposed to my usual S-4 and (M) mode on).

Its funny how my friends have asked me numerous times "how does it feel in P400 mode as opposed to P500?" ... my only response to them is "dunno..never tried it!".

shchow · Mar 4, 2009

I love the feel of the SMG. As already mentioned, it still gives a better connection, IMHO, to the car. I never use D mode unless I'm having a cup of java on my way in to work. When controlling your own shifts, I never felt it to be too lurchy. It may not be as smooth as an automatic, but if I wanted smooth, I would have gotten an slushbox.
I think the double clutch technology is fantastic, but I wonder about reliability. Whenever adding more components/complexity, there's always going to be issues of durability.
In as far as making the clutchless manuals smoother with the development of the double clutched systems, I'm not sure how successful they will be in the long run. With improvements in slushboxes, the tiptronic feature in automatics have almost become as good as the clutchless manuals, C63 for example.
The DCT is an attempt to refine something that, IMHO, didn't need to be refined. If I order seafood, I want it to be fishy, and not make it taste like chicken...

PianoProdigy · Mar 4, 2009

Still haven't tried the DCT (maybe this week), but my biggest gripe about the SMG is the slow shift times at lower RPMs which I believe is fixed by the DCT.

Hammer91 · Mar 5, 2009

Sorry to have to say it!

Had 2002 M3 Cab with SMG, have now 2006 M5 SMG and 2008 M3 Cab with DCT. There is no comparison, DCT is better in every way you can imagine. Instant shifts, great function in auto mode, and NO LAG. The M5 SMG is worse than my old M3 SMG IMHO. Don't get me wrong, I love my M5, but once you drive the DCT you will notice how much lag the SMG has. SMG will soon disappear from the scene.

bart12 · Mar 5, 2009

Its funny why car makers are trying to develop transmissions away from an automatic to give people the benefit of enjoying an F1 derived engine.

I think that is why SMG3 was perfect for me. I never use the D mode in my M5 because it gives me a headache. I would rather drive my 3 series if I were to use the D mode. And I am sure a lot of you here would use your other car if you are stuck with the D mode for any reason.

But now, we have a DCT which is supposedly an improvement from the SMG3, but actually trying to mimic the smoothness of an automatic.

Just get an automatic. Whats the use of getting a DCT and end up using the D mode. This is what I dont get. Talk about going in a circle.:nono:

Everyday I drive my M5, its a manual transmission and the engine is music to my ears. And I dont have to worry how my left shoe looks like in 2 months. Imagine, my left shoes looks 2 years older compared to my right one when I use to :eek7:drive a MT....

Murtaza · Mar 5, 2009

bart12 said:
But now, we have a DCT which is supposedly an improvement from the SMG3, but actually trying to mimic the smoothness of an automatic.

Just get an automatic. Whats the use of getting a DCT and end up using the D mode. This is what I dont get. Talk about going in a circle.:nono:

I have to disagree here. Whats wrong with having F1 performance with the comfort of an automatic all in one? Some people like to use both.

Revo · Mar 5, 2009

I think most people have covered major differences and advantages between the DCT and SMGIII.

However, I do wonder about the post on the first page saying that at full throttle it takes only one pull on the negative paddle for the transmission to automatically shift into the gear most ideal for maximum acceleration? While in once sense I feel this is a bit "cool" I also don't like it, and would prefer that they give you an option to enable or disable the feature.

I say this because I like the raw feeling of the SMGIII. It's really just like a manual except you choose the gear and it does the rest for you.

I will honestly say that the SMG pisses me off a lot cause it shifts like crap (even in S5) unless you do it just right (when you aren't driving it like a F1 car). In D mode I feel like I have a 5 second float through the space/time continuum between each shift. Makes me feel like an idiot in front of my friends - can't even drive what is otherwise (to them) an automatic car.

However, once you get on it and go through a few gears in S5/S6 and feel that kick as it slams into each next gear, all the hate is gone - its all smiles.

This is why I think they should give you an option to turn the automatic downshift on or off.

My reasoning is this, tiptronic automatic transmissions are set apart by one defining thing - how "manual" they really are. Some tiptronics are just like the SMG. They let you bounce off the rev limiter all day until YOU tell it to shift. Others are the lame type that the second you get near redline they just shift anyway. I don't want the SMG (DCT) to turn into one of these, starting to do more and more and more automatically without driver input.

Though, I'll have to admit, even after the exhilaration of driving the M, sometimes I just have such appreciation after getting back into my own car (G35 Coupe for those that don't know) and playing with a traditional 3 pedals and a proper 6 speed stick. I guess nothing can really replace that feeling of dropping the clutch after slipping it into the next gear.

Well, now that I've finished my little rant, I will have to point out something about the DCT that seems inconsistent.

I can see how the DCT may best the SMGIII when shifting from one gear to the next (1 to 2, 2 to 3, 3 to 4, etc.). However, based on the design (one clutch for even gears - 2,4,6 and one clutch for odd gears - 1,3,5,7 - I can see how it gains the advantage going from one gear to the next, since theoretically the next is already engaged.

However, when going from say, an even gear to an even gear, or odd gear to odd gear (say 7th down to 3rd, 6th down to 2nd) or something of the sorts, I can't see the transmission being any quicker than the SMGIII. In the end, both transmissions have to engage the clutch, shift to a new gear, and release. Just figured I'd point that out.

Lastly, I find it funny that we who drive the 4000lb luxury sedans (and coupes, for our fellow M6 owners) get the raw tranmission, while the ones with the sports car (M3 owners) get the refined one. That's irony!

So, if I EVER get past the decision of what car to buy once I'm out of college (M3 or M5), I'll have the awesome fun of choosing what transmission. :dunno:

Either way, happing M mode-ing everyone! :wroom: (for the manual guys: :noSMG: )

Murtaza · Mar 5, 2009

Revo said:
However, I do wonder about the post on the first page saying that at full throttle it takes only one pull on the negative paddle for the transmission to automatically shift into the gear most ideal for maximum acceleration? While in once sense I feel this is a bit "cool" I also don't like it, and would prefer that they give you an option to enable or disable the feature.

I really hope it doesn't work that way, it would be a nice option but to have it work that way all the time...say it ain't so:nono:

KGPEsq · Nov 19, 2010

I agree with the comments regarding the relative smoothness of DCT versus the natural feel of SMG

HOWEVER, how do you think a DCT E60 M5, which we now know is an impossibility, would fair in performance sprint times versus the SMG?

bkesler · Nov 19, 2010

Seems to me that in a straight line, any performance gains from quicker shift times would be offset by added weight of second tranny and clutch. On the track, I would guess that the extra weight would be even more of a negative factor.

M3toM5 · Nov 19, 2010

I find this thread very interesting - great question.. the argument of SMG being "raw" and "natural" and "feels better" relative to a DCT is ironic - it is all a relative world after all. Having driven SMG in e46M3, E60 M5 and DCT in the current M3 & Audi TT, I can relate to the arguments. But I cannot come up with any arguments for SMG now.

The last time I wanted to buy a SMG e46 M3 (in 2003).. i experienced it and decided it was awesome at the time, blew me away but why I drive is the feel and involvement and purchased a 6sp manual (E39 M5)...

again when it was time buy 4 weeks ago, upon back to back testing of a DCT M3 and SMG E60M5, I decided SMG felt like a "hack" compared to the DCT and decided to buy a E60M5 6sp manual because it is more natural, raw, better feel, more involved etc etc (i may be getting old whatever...totally agree the SMG is a superior technical set up and is progress in engineering)

so there is no argument for a SMG imho, either DCT or a 6speed manual.. SMG was a long hack(come out in a e36 M3 in europe in mid 90s) to get get to a DCT.

EGBOZ · Nov 19, 2010

DCT is silky smooth, on the track it gives lightening quick shifts without unbalancing the car the way the E60 SMG II does. With the E92 DCT you don't need to lift - shifts are definately faster (and smooth while still being strong); with the E60 SMG II if you don't lift just a touch it's really too jerky (IMHO) for the track where you don't want the car being unsettled anywhere near the limits. :checkeredflag:

fasttoys · Nov 20, 2010

SMG Raw
DCT feels like Auto to me. Sold my M3 DCT it was boring.

BMWM5Driver · Nov 20, 2010

I too have tracked the M3 DCT and it was impressive. I enjoyed the DCT more than the SMG which i describe as clunky for daily commuting.

I like my SMG, but the DCT was quicker on the track and silky for commuting.

BMWM5Driver · Nov 20, 2010

I hope the F10 M5 has a DCT.

AFC1 Discussion starter · Nov 20, 2010

Nice to revisit one of my older threads. Since I started this thread last year, I've tried VW/Audi's DSG in a few different models, but I haven't yet had the chance to drive an M3 DCT or a Porsche PDK, so I'll still reserve full judgment about this type of transmission.

I will say that compared to the Audi DSG, the SMG is way more raw feeling, and feels close enough to driving a three pedal car that I would consider having an SMG car as my only vehicle (I couldn't only own a car with a DSG as I would still crave the "feel" of a manual transmission in everyday driving). I've driven SMG enough at this point that it can really be perfectly smooth for daily driving. Yes, it takes a little work unlike a full automatic or DCT, but so does a manual to drive it smoothly. Lastly, I like how SMG has such a loyal fan group...I feel like people are more "in awe" or "impressed" by DCT, as opposed to having a true love for the transmission like people on this board have with SMG.

In short, I'd take a high quality single-clutch sequential gearbox over any of the dual clutch transmissions I've tried so far.

afc1
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KGPEsq · Nov 20, 2010

Paradox equation

This brings me to the other side of the issue, the ideology of M.

Gerd Richter in 2006 explains the preference for SMG over the then available DCT on the E60 by more or less saying that the seamless DCT shifts are better suited to luxury driving akin to the 7-series and is not the feel demanded by M. To be fair, SMG II was lauded by critics in its days with the E46, many describing it as fun to drive.

Now the E9x M3 has had DCT since 2008 and no SMG, which is 2 years during the E60 production that the SMG was still available, the F10 M5 is looking more and more like a DCT sans SMG car and we could imagine that the M6 when launched again will fall into the same category.

At the BMW M Power Tour last month, our BMW chief tech speaker lauded DCT as the most natural transmission a race car should have and perfectly in tune with M's needs.

Is it me or did M do an about face on the issue? If so is this due to the poor critical reception of SMG III vis-a-vis its second generation descendant?

Revo · Nov 20, 2010

KGP said:
This brings me to the other side of the issue, the ideology of M.

Gerd Richter in 2006 explains the preference for SMG over the then available DCT on the E60 by more or less saying that the seamless DCT shifts are better suited to luxury driving akin to the 7-series and is not the feel demanded by M. To be fair, SMG II was lauded by critics in its days with the E46, many describing it as fun to drive.

Now the E9x M3 has had DCT since 2008 and no SMG, which is 2 years during the E60 production that the SMG was still available, the F10 M5 is looking more and more like a DCT sans SMG car and we could imagine that the M6 when launched again will fall into the same category.

At the BMW M Power Tour last month, our BMW chief tech speaker lauded DCT as the most natural transmission a race car should have and perfectly in tune with M's needs.

Is it me or did M do an about face on the issue? If so is this due to the poor critical reception of SMG III vis-a-vis its second generation descendant?

I think one thing that needs to considered is that the SMG II (which was the first SMG available in a road car) was released in the M3, which is a car focused greatly on driving experience and handling/performance.

The next SMG, the SMG III was then released on the M5 and M6, and while it was light-years smoother than the SMG II in many ways, the car attracted a different crowd and the consumers were a lot less forgiving of the SMG's flaws. The simple fact is that the M5 and M6 attract a lot of executives which want "the top of the line 5 series" and mistakenly get the M5 for the M badge and because it cost the most, despite the 550i being the most luxurious one in the 5 series lineup, and especially a car that's supposed to be a comfortable mini-7 series when not in M mode, then of course you get complaints.

Based on these complaints, the DCT was the next logical step - performance wise it's all the benefits, none of the drawbacks, and for everyday driving, it's almost the same thing.

///M-five · Nov 24, 2010

I was reading up on the new yet to be released Lamborghini’s Murcielago LP700-4 with an all-new 6498cc V12 engine producing 690bhp at 8250rpm and delivering a heady 509lb ft of torque at 5500rpm which will be shown at the 2011 Geneva motor show early next year, and what caught my interest therein was its 7-speed gearbox, have pasted some of the info below;

'This new Murceilago replacement gets a completely new seven-speed gearbox which Lamborghini refer to as being an ‘ISR’ transmission, standing for ‘Independent Shifting Rods’, here’s how it works.

On a conventional gearbox, second gear sits next to third gear on a shaft running through the gearbox, and as you move the gearstick from second to third, a selector fork moves a sleeve from one gear to the other, allowing the next gear to come into play.

On this new gearbox, though, the gears are engaged independently. So in the same example of changing from second to third, the third gear selector can be partway through the process of bringing the gear into play as the second gear selector is taking second gear out of drive. This means the speed of change can be shortened dramatically, Lamborghini is saying changing gear via a paddle on this new gearbox will take just 50milliseconds, some 40 per cent faster than on the very latest e-gear equipped Lamborghini Gallardo.

Another requirement was for this gearbox to carry all the hydraulic valves and piping internally within its casing, so reducing the overall size of the gearbox dramatically.

Fitting a dual-clutch transmission to this new car was dismissed very early on - this type of gearbox would weigh a lot more than the new single clutch gearbox does, as well as being physically bigger too, so packaging would have been much trickier.

Winkelmann doesn’t like the feel a modern DSG gives either, preferring the more aggressive action of the new gearbox, saying it gives the driver a more emotional link with the mechanicals of the car than a dual-clutch transmission gearbox ever could.'

Daytona Bones · Nov 24, 2010

///M-five said:
I was reading up on the new yet to be released Lamborghini’s Murcielago LP700-4 with an all-new 6498cc V12 engine producing 690bhp at 8250rpm and delivering a heady 509lb ft of torque at 5500rpm

Fitting a dual-clutch transmission to this new car was dismissed very early on - this type of gearbox would weigh a lot more than the new single clutch gearbox does, as well as being physically bigger too, so packaging would have been much trickier.

Weight can't be too much of a problem when they decided to shove a huge V-12 in there... :grinyes:

DB

NavM · Nov 24, 2010

Once you drive DCT, you don't want to go back to SMG. I've driven the E92 M3 and B8 S4 with dual clutch and love it. I like the SMG in M5 and drive it everyday, on highways, stop and go traffic and it doesn't bother me. Yes, it may be jerky on occasion depending on the drivelogic setting selected or the RPMs but overall I like it a lot. However, the DCT is on a different level and I wish the E60 M5 was equipped with it.

FTB · Nov 24, 2010

Maybe you'd like to go out in bang...with the car. Sounds like fun at times...

SMG vs. DCT

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