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      08-21-2008, 01:53 AM   #1
M3Rad
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M3 DCT vs. 6-speed gear ratios for Track Use

The DCT has very close ratios from 2nd to 6th, I have yet to drive a track where this car could exceed 173 mph, so 7th won't see track use.

1st and 2nd are very similar between transmissions, the gap between these two gears doesn't matter for track use, because I don't know of any track that requires a downshift to 1st.

With the manual transmission, there is a huge gap between 2nd/3rd and 3rd/4th, this must hurt acceleration beyond 75 mph compared to the DCT. Things get closer to even after 150 mph, but it is rare to exceed this speed at the U.S. racetracks.

The engine produces its nicest power between 7,000 rpm and 8,400 rpm, this is the ideal powerband. I would consider a shorter final ratio with a top speed of 170 mph in 7th and 80 mph in 3rd spreading 5 gears across 90 mph.

BMW M3 DCT
Gear / Ratio / Max Speed / RPM drop on upshift
1st 4.780 44
2nd 2.933 71 5200
3rd 2.153 97 6200
4th 1.678 124 6500
5th 1.390 150 6900
6th 1.203 173 7300
7th 1.000 208 7000
Final Ratio 3.154
Redline 8400

BMW M3 6-speed
Gear / Ratio / Max Speed / RPM drop on upshift
1st 4.055 44
2nd 2.396 75 4900
3rd 1.582 113 5600
4th 1.192 150 6300
5th 1.000 179 7000
6th 0.872 205 7300
Final Ratio 3.678
Redline 8400
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      08-21-2008, 02:49 AM   #2
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and your point is......?
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      08-21-2008, 02:51 AM   #3
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and your point is......?
I was scratching my head on that one as well.
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      08-21-2008, 04:11 AM   #4
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Quote:
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and your point is......?
For track use, if your focus is on faster lap times, DCT offers a very nice benefit (not considering shifting times) due to the close ratios between 2nd and 6th compared to the manual transmission.
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      08-21-2008, 06:15 AM   #5
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Originally Posted by M3Rad View Post
For track use, if your focus is on faster lap times, DCT offers a very nice benefit (not considering shifting times) due to the close ratios between 2nd and 6th compared to the manual transmission.
I understand that but there is very few semi-autos that allow the same choice/flexibility as you get with a manual, in fact if you search you will see that there is issues with DCT on downshift requests. That is something you don't get with a manual, on the other hand when the downshift is executed it will be conducted to a higher standard than almost any human, the same goes for the speed of the shifts both up and down.

The DCT may be a little quicker on the track but the jury is out on whether it's as entertaining as stirring things yourself.
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      08-21-2008, 07:29 AM   #6
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I have been on track 2 times now with my M3 6sp and do not have issues with the ratios.According to your calculations with the M-DCT I would be shifting twice as much as I am now.That is great in theory as long as you get it downshift when you need it to.I am quite enjoying my old school 6 speed car and with the broad power delivery that this motor makes ,it is just fine thank you.
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      08-21-2008, 11:27 AM   #7
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1) DCT still has downshift delay issues that may be fixed soon with an update.
2) Possible heat issues on hot days.
3) Durability, fluid changes under track use? Could be very expensive.

Now if the issues get fixed, we can talk about an advantage, but for now who knows.
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      08-21-2008, 06:19 PM   #8
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You missed the biggest advantages of DCT.

1: You can shift mid turn without upsetting the car since the gearbox doesn't interrupt the power delivery to the rear wheels.

2: left foot brake 100% of the time.
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      08-22-2008, 02:07 AM   #9
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Quote:
Originally Posted by enigma View Post
You missed the biggest advantages of DCT.

1: You can shift mid turn without upsetting the car since the gearbox doesn't interrupt the power delivery to the rear wheels.

2: left foot brake 100% of the time.

HAha !!!! that is IF the computer decides to downshift.
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      08-22-2008, 07:06 AM   #10
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Quote:
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HAha !!!! that is IF the computer decides to downshift.
I restrained myself from saying that
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      08-22-2008, 11:53 AM   #11
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Quote:
Originally Posted by sayemthree View Post
HAha !!!! that is IF the computer decides to downshift.
Quote:
Originally Posted by Gearhead999s View Post
I restrained myself from saying that


And the car doesn't go into limp mode in mid-corner.

When I took my E92 335i to the track, it went into f-king limp mode as I came out of the corner.
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      08-22-2008, 11:58 AM   #12
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6MT owners should be banned from all DCT-related threads IMHO

coz we cant help but point out how DCT sucks ass all the time
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      08-22-2008, 01:52 PM   #13
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Quote:
Originally Posted by sayemthree View Post
HAha !!!! that is IF the computer decides to downshift.
And you wonder why DCT owners don't go out of their way to answer your questions....
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      08-22-2008, 06:10 PM   #14
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Quote:
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And you wonder why DCT owners don't go out of their way to answer your questions....
Dude - relax, its all in fun. we have to make up for feeling inferior due to having old school hardware.
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      08-22-2008, 06:24 PM   #15
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Dude - relax, its all in fun. we have to make up for feeling inferior due to having old school hardware.

I was about to say the same, I'm getting an M-DCT but I didn't class it as a dig, just a lighthearted joke.
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      08-25-2008, 01:28 AM   #16
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Quote:
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I was about to say the same, I'm getting an M-DCT but I didn't class it as a dig, just a lighthearted joke.

some people take these internets too serious!?!
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      08-25-2008, 02:07 AM   #17
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Quote:
Originally Posted by clubspec330i View Post


And the car doesn't go into limp mode in mid-corner.

When I took my E92 335i to the track, it went into f-king limp mode as I came out of the corner.
I haven't heard of any limp mode nor related issues tracking the M3. Of course the 335i and modded 335i's is another story entirely .
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      08-25-2008, 11:49 AM   #18
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Quote:
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I haven't heard of any limp mode nor related issues tracking the M3. Of course the 335i and modded 335i's is another story entirely .
I think MarksM got limp mode - possibly related to DCT overheating/downshifting issue.

as far as ratios and the track? it all depends on the track layout.
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      08-25-2008, 02:01 PM   #19
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I think MarksM got limp mode - possibly related to DCT overheating/downshifting issue.

as far as ratios and the track? it all depends on the track layout.
I think driver skill will have far more bearing of lap times than one car having better spaced ratios than another.

It's a silly discussion in my opinion.
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      08-25-2008, 07:24 PM   #20
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Quote:
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I think driver skill will have far more bearing of lap times than one car having better spaced ratios than another.

It's a silly discussion in my opinion.

agree - this true.


and optimal gearing for one track may not be the same as the optimal gearing required for the next track.
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