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      12-13-2008, 08:38 AM   #1
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M3 6speed vs DCT

Today I decided to settle my doubts on which is faster. I was tired of hearing how much faster the DCT is than 6 speed, faster even than C63 in some cases. So my buddy has JzB with carbon roof coupe in M-DCT and I called him to have some dice fun

He is a showoff of note and would not stop dissing 6 speed and how much better carbon roof is and saying things like "Why the fuck would you put upgraded sound in an E92 M3 when BMW have the best integrated enhanced sound!"

HIs car has 5000miles I have 20000miles (Well opened up engine )

Anyways we did 5 runs till limiter on closed circuit

LAunch control used(when it worked) on MDCT and M-dynamic launching at 4500 RPM in 6 speed :
1)first run. I get boggy launch and MDCT pulls 2 car length ahead but gap stays constant.. AFter 120mph I start to catch up.. by 140 I am at his bumper
and catching fast.. LImiter.
"WTF? u got nitrous or what?" is his comment
DCT- 1 6speed- 0

2)second run. I messed up again on launch and tried to make up by slipping clutch. He got away a bit further, maybe 3 car lengths this time but I still started to catch up with him at the same rate of acceleration as before - hit limiter together
DCT- 2 6speed- 0

3)third run. Launch control does not want to work - high temps detected so we do rolling start to be fair

Nailed him by 3 car lengths easily and pull away (maybe opened up to 5 car lengths) all the way to limiter
DCT- 2 6speed - 1

4)fourth run. DCT launch control back in action
I nail perfect launch and pull away by a bonnet bulge. After 120mph gap opened to 1 car length, hit limiter 2 car lenghts ahead
DCT-2 6speed - 2

So we even and I say lets go home but my pal is a cock "We must go again, you decatted your fucking exhaust you liar.. i cant believe this shit" are his words. Me is :

5)fifth run. Launch control wont work again.
So rolling we go. Kill him by 2 car lengths and just open up 5 car lengths till limiter.
DCT-2 6speed - 3

The pussy goes home with his tail between his legs silent
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      12-13-2008, 09:32 AM   #2
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That sounds an impressive beating. It's definitely more than has been reported else where but without trying it myself I can't really say either way.

I know I did similar runs when I had a GTI with DSG, comparing it to another GTI 6speed manual. In that case the DSG was quicker but then again the ratios were matched and it was solely the shift times making the difference. With the M-DCT you have an extra gear (7) and most of the ratios and final drive is different so it's explainable why a manual could indeed be quicker.

I wonder if your friend happen to be doing his runs in S5 instead of the quicker S1.
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      12-13-2008, 10:54 AM   #3
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Nice story, without videos its just a story...
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      12-13-2008, 11:47 AM   #4
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Quote:
Originally Posted by aggs400 View Post
Nice story, without videos its just a story...
Whats there to lie about? I am partial to both transmissions and I am about to possibly swap to a DCT so no hard feelings if it wins or loses really. Videos will be made tomorrow and results will be the same I am sure if my buddy does not sneak in a nos canister
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      12-13-2008, 11:55 AM   #5
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Quote:
Originally Posted by footie View Post
That sounds an impressive beating. It's definitely more than has been reported else where but without trying it myself I can't really say either way.

I know I did similar runs when I had a GTI with DSG, comparing it to another GTI 6speed manual. In that case the DSG was quicker but then again the ratios were matched and it was solely the shift times making the difference. With the M-DCT you have an extra gear (7) and most of the ratios and final drive is different so it's explainable why a manual could indeed be quicker.

I wonder if your friend happen to be doing his runs in S5 instead of the quicker S1.

Not really that impressive considering the mileage on my car and the way I drive (fucking hard - living above 7000rpm in most gears when roads and traffic allow) so its well broken in and obviously better at making power than his. Lower final drive on manuals are also an advantage in rolling starts and top end accelaration. He was using fastest manual shift mode with surge delux
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      12-13-2008, 12:40 PM   #6
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Quote:
Originally Posted by Doc View Post
Not really that impressive considering the mileage on my car and the way I drive (fucking hard - living above 7000rpm in most gears when roads and traffic allow) so its well broken in and obviously better at making power than his. Lower final drive on manuals are also an advantage in rolling starts and top end accelaration. He was using fastest manual shift mode with surge delux
I wished he had tried some other modes, if only to give another resulting view of which manual mode is quickest. Chances are if he had have used S1 he would have won all of the races.

What this race really proves is your car is quicker and that would have been the outcome regardless of the transmission he was running.

Next time get some video, it's always fun to see an M3 running at maximum attack mode.
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      12-13-2008, 01:04 PM   #7
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Quote:
Originally Posted by aggs400 View Post
Nice story, without videos its just a story...
+1
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      12-13-2008, 05:27 PM   #8
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Seems to me the variation in the results are large enough and the raw value of who "won" swapped enough times that no real conclusion is possible other than that the cars are close, which makes perfect sense.

What about vehicle weights, fuel levels, wheel sizes, etc? They all add up.

If you really want to determine a winner from a drag racing perspective you need to have similarly outfitted cars that weigh the same, with similar miles (prob. above 10k), use wheel testers, have equally skilled drivers and perform lots of runs. Personally, I will not accept such anecdotal and uncontrolled results as anything but that - anecdotal - in terms of a real difference between transmissions.
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      12-13-2008, 05:32 PM   #9
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Quote:
Originally Posted by footie View Post
That sounds an impressive beating.
Yup, wins to both parties and it is a "beating". You are funny.

Quote:
Originally Posted by footie View Post
I know I did similar runs when I had a GTI with DSG, comparing it to another GTI 6speed manual. In that case the DSG was quicker but then again the ratios were matched and it was solely the shift times making the difference. With the M-DCT you have an extra gear (7) and most of the ratios and final drive is different so it's explainable why a manual could indeed be quicker.
Not sure how many times I have to tell you but VW DSG in the GTI has different ratios than the 6MT. I have posted both sets of ratios here in the past.
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      12-13-2008, 05:48 PM   #10
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6MT for ultimate control and in this case FTW!!!
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      12-13-2008, 08:15 PM   #11
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So the car with higher mileage which had been driven harder had better acceleration, particularly at the top end - same result as my comparisons recorded on Drivers' Republic.
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      12-13-2008, 08:57 PM   #12
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I wonder how the Ferrari guys are doing with the same Gertrag DCT transmission the M3 has in their new models.
Somehow I doubt it will get bashed in any reviews.
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      12-13-2008, 10:18 PM   #13
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Quote:
Originally Posted by Advskier View Post
I wonder how the Ferrari guys are doing with the same Gertrag DCT transmission the M3 has in their new models.
Somehow I doubt it will get bashed in any reviews.
+1.

Despite the few bugs found thus far, those fixed and those not, it is still an amazing transmission. I really can't see owning the car without it. It was not designed for drag racing. It is beyond mildly entertaining that we don't see more discussion about the improvements from the DCT on the track both in terms of actual times but in regards to the important areas of confidence, control and the freeing up of your left foot and mental/physical capacity for other aspects of high performance driving.
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      12-13-2008, 11:09 PM   #14
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I remember reading the Road Test Summary page in the back of Road & Track.

The DCT was faster 0-60mph by .3 sec, 0-100mph by .5 sec.

Last edited by JetBlack5OC; 12-14-2008 at 01:05 AM.
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      12-14-2008, 04:37 AM   #15
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Well to put things in perspective we both have 19inch wheels with Michelin Pilot sports, had full tanks of gas and no passengers or any other weight in the boot (except for my JL sub, alpine pdx amps, clean sweeps and I have a sunroof) so it was not a fair comparison against me. I will tell you this much: the DCT in real world is faster for just getting in and driving. However put a skilled driver in a 6 speed and the DCT, the gains are not really visible. The gearing plays a big role here. Between 60mph to 110mph is the DCT sweet spot and were its short spaced gears allow it to pull away with rapid shifts. Lets face it, that is the speed range on most tracks so I guess the DCT has the advantage here. However above 115mph the manual does catch up and the gains of DCT are eaten up by the 6speed. I guess if you take identical mileage cars and put a ninny driver in the DCT and an expert in the 6speed the results will favor the DCT. I just think that its much of a muchness and you have to chose what you like to drive and how you like to experience your drive. For me its just going to be fun working on getting perfect launches and making perfect shifts. Heel and toeing with the perfect downshift is very satisfying and I like to impress my passengers with my skills, if you know what I mean
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      12-14-2008, 06:01 AM   #16
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Quote:
Originally Posted by swamp2 View Post
Not sure how many times I have to tell you but VW DSG in the GTI has different ratios than the 6MT. I have posted both sets of ratios here in the past.

OK, my choice of words 'ratios were matched' was a little misleading and you were right to pick me up on this. What I meant was that they were both 6 gears and the ratio/final drives were 'closely matched'.

http://tt.mania.ru/TT_coupe32.pdf

I might add that the future of DCT gearboxes is not wet clutch, they weigh too much and are less efficient compared to a dry clutch system as used in the Bugatti Veyron (might explain it's excessive price).

Wet Clutch 6sp DSG vs Dry Clutch 7sp DSG
Weight : 16Kgs less for Dry Clutch transmission (even with extra gear)
Efficiency : 85% vs 91% for Dry Clutch

Wet Clutch is the cheap way to achieve the kind of torque handling capabilities required but I think they will be short lived and dry clutch will replace them within 4 years.
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      12-14-2008, 06:54 PM   #17
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Is there not a power loss with the DCT with regard to the 6MT? I know rotating mass makes a difference in most cars but does it apply here?
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      12-15-2008, 05:59 AM   #18
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Yes, DCT is less efficient than a standard manual and it's all down to the wet clutch assembly. How much of a difference I don't know but gauging that both forms of DSG (wet vs dry) the difference must be at least 6%.
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      12-15-2008, 05:03 PM   #19
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6% more drivetrain loss sounds extreme?
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      12-15-2008, 05:34 PM   #20
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Originally Posted by Dascamel View Post
6% more drivetrain loss sounds extreme?
I can only comment on the facts between the two DSG gearboxes, one being a wet clutch and the other dry. In this case the dry clutch setup is 6% more efficient and it's only logical to expect a manual to be similar.
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      12-15-2008, 08:40 PM   #21
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Quote:
Originally Posted by Dascamel View Post
6% more drivetrain loss sounds extreme?
Exactly. You can not infer the exact same thing is happening in a DCT vs. wet/dry differences and generational differences combined in DSG. The M3 is generally seen to have a very efficient drive train which is part of BMWs effort in efficient dynamics. As well the efficiency differences do not translate directly to overall drivetrain efficiencies. If the transmission is responsible for about 1/2 of the total drive train loss, not counting tires, then this 6% really means 3% overall and I still seriously doubt that DSG 2nd gen vs. DCT first gen will be 3% overall more efficient. Really doesn't matter anyway with the huge losses from quattro...
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      12-16-2008, 01:02 AM   #22
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Quote:
Originally Posted by swamp2 View Post
Exactly. You can not infer the exact same thing is happening in a DCT vs. wet/dry differences and generational differences combined in DSG. The M3 is generally seen to have a very efficient drive train which is part of BMWs effort in efficient dynamics. As well the efficiency differences do not translate directly to overall drivetrain efficiencies. If the transmission is responsible for about 1/2 of the total drive train loss, not counting tires, then this 6% really means 3% overall and I still seriously doubt that DSG 2nd gen vs. DCT first gen will be 3% overall more efficient. Really doesn't matter anyway with the huge losses from quattro...
This 6% efficiency difference is solely the gearbox, not total drivetrain and the dry clutch system VAG offer with their transverse setup is the most efficient DCT system currently on the market.

My point is that on pure efficiency the manual and this dry clutch DSG will probably be very similar and I don't believe that the fwd (wet clutch) DSG and BMW's (wet clutch) DCT will produce that different figures of efficiency.

I might be wrong, but I doubt it.
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