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      03-27-2012, 07:10 PM   #1
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Question Upshifting mid-corner in S6 ?

Question for DCT track junkies: do you upshift mid-corner using S6 mode.

Let me elaborate my question. Using MDM and S5 in a straight line, I can clearly feel the "surge" on upshifts. However, I found that when I upshift mid-corner the DCT seems to read the conditions (i.e. lateral acceleration) and does a butter smooth upshift as to not upset the car. I found this extremely useful, as you can always maximize the power band regardless of the car's cornering attitude.

So does the DCT behave the same way in S6 (obviously with DSC off )?

I have yet to find a corner where I can try this out safely. I do not want to spin at 100mph...





I did , but couldn't find...
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      03-27-2012, 07:47 PM   #2
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Quote:
Originally Posted by CanAutM3 View Post
Question for DCT track junkies: do you upshift mid-corner using S6 mode.

Let me elaborate my question. Using MDM and S5 in a straight line, I can clearly feel the "surge" on upshifts. However, I found that when I upshift mid-corner the DCT seems to read the conditions (i.e. lateral acceleration) and does a butter smooth upshift as to not upset the car. I found this extremely useful, as you can always maximize the power band regardless of the car's cornering attitude.

So does the DCT behave the same way in S6 (obviously with DSC off )?

I have yet to find a corner where I can try this out safely. I do not want to spin at 100mph...





I did , but couldn't find...
I do upshift in corners usually from the apex out on corner exit from 3-4 or 4-5 not on a 2-3 shift as it will chirp the tires in a straight line so I would imagine it would upset the car.The 2 places that I do this that I can think of where I do this is exiting the Esses at Watkins Glen coming onto the straight where it is a 4-5 shift and Corner 5 and Corner 3 at Mosport where I do a 3-4 shift while the car still has a lot of cornering load on it with no issues from the shift.I run with all the nannies turned off in S6.

Last edited by Gearhead999s; 03-27-2012 at 07:59 PM.
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      03-27-2012, 07:56 PM   #3
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Not so sure, as I always use S4. S5 is too rough
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      03-27-2012, 08:00 PM   #4
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Quote:
Originally Posted by Gearhead999s View Post
I do upshift in corners usually from the apex out on corner exit from 3-4 or 4-5 not a 2-3 shift as it will chirp the tires in a straight line so I would imagine it would upset the car.The 2 places that I do this that I can think of where do this is exiting the Esses at Watkins Glen coming onto the straight where it is a 4-5 shift and Corner 3 at Mosport where I do a 3-4 shift while the car still has a lot of cornering load on it with no issues from the shift.I run with all the nannies turned off in S6.
Thanks. Kind of figured you'd be the first to post an answer.

I'll try it at turn 6 at Tremblant. It's a left hand sweeper that can be taken flat out all the way through. But I would need to upshift mid corner to maximize the power band. Looking forward to try it out.
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      03-27-2012, 08:12 PM   #5
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Here is a video of the Glen showing where I was shifting.The GPS reads low compared to my revs and in gear speeds.

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      04-05-2012, 04:55 PM   #6
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I agree with Persian54. No need to use S6 unless you want to destroy the DCT sooner. S4 is fast enough and doesn't upset the car.

There is a trade off between fast shifts and slow shifts. Fast shifts are harder on the gears. Slow shifts are harder on the clutches. Gears break. Clutches wear out. In this case the DCT clutches are pretty robust. Probably will never wear out. Gears on the other hand, and the syncros, usually just break.

Learned that the hard way on my E46 M3 with SMG II.
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      04-05-2012, 05:25 PM   #7
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i only drive in s5 with sport plus. I feel the surge but it is defiantly less noticeable when turning. u might have to counter a little bit but thats about it.
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      04-05-2012, 06:18 PM   #8
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Quote:
Originally Posted by jvitas View Post
I agree with Persian54. No need to use S6 unless you want to destroy the DCT sooner. S4 is fast enough and doesn't upset the car.

There is a trade off between fast shifts and slow shifts. Fast shifts are harder on the gears. Slow shifts are harder on the clutches. Gears break. Clutches wear out. In this case the DCT clutches are pretty robust. Probably will never wear out. Gears on the other hand, and the syncros, usually just break.

Learned that the hard way on my E46 M3 with SMG II.
SMG's which used a "normal" dry clutch and M-DCT 'dual clutch" are night and day different in the way they operate.A SMG shifts like a normal manual gearbox where a DCT uses 2 input shafts with the gears preloaded before the clutch drives the next gear selected.Quite different for sure.So far issues that happened with SMG have not surfaced in the M-DCT.
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      04-05-2012, 08:49 PM   #9
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Originally Posted by vonwilbs View Post
What about grabbing a higher gear before entering the long corner? Do you really lose time? OR does the great new technology of double clutch and no torque loss transmissions allow us to achieve faster times through solving this time honored conundrum?
Good question. It is exactly the point of my post.

Looking at data logging, there is a clear advantage of maximizing the power band. For example, at Mont-Tremblant turn 6, when short shifting into 4th gear at 7000RPM before entering the turn compared to maximizing the power band by shifting mid corner at 8400RPM, I manage to be about 0.3 sec quicker through that sector. Not a huge difference, but still faster. At Tremblant, there is also a similar gain to be had between 13 and 14.

Using MDM and S5, I would shift with the throttle pinned to the floor. Either the transmission or DSC/MDM is smart enough to know that the car is laterally loaded and executes a smooth seamless shift (no loss of traction and no surge). When I run DSC off and S6, I never trusted shifting mid corner at WOT, so I always lifted slightly before shifting, thus negating some of the advantage and slightly unbalancing the car (also never tried it at turn 6).

So I am wondering if the same smart logic is there in S6. In other words, is the smart logic programmed in the DCT or is it part of MDM/DSC.

Based on Gearhead's input, I will try a flat out mid-corner shift in S6 next time I am out there (keeping some margin for the first time of course )

I'll keep you informed of the results .

Last edited by CanAutM3; 04-05-2012 at 09:47 PM.
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      04-05-2012, 09:06 PM   #10
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Quote:
Originally Posted by vonwilbs View Post
Thinking about it more, if you're mid corner then you'd want to be using 100% of the tire and shifting is going to upset that and upset the balance of the car as well. Even without any torque loss between gears, on power you'd be going from one understeer condition to a lesser one because the higher gear sends less torque to the wheels so weight would transfer forward. It would be like breathing the throttle, I think. You can even spin a car on a straight if you aren't smooth.

Do you think if you can upshift in a turn, even on track out, then you aren't going fast enough? Or am I not thinking about everything here?
That is the exactly the benefit of DCT in this situation, at least in S5 with MDM. With the two clutches, the transmission can do such a smooth shift that you DO NOT FEEL THE SHIFT AT ALL. It does not upset the chassis even if you are at the limit of adhesion of the tires.

Now I only need to prove to myself that I can also do this in S6 .
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      04-05-2012, 09:13 PM   #11
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Quote:
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I think maybe if you are getting away with it, you're going to slow!
Don't think so, read my post again... then again, you might be right, there is always more speed to be gained .

Turn 6 a Tremblant is particular in the sense it can be taken flat out all the way through, no braking before entry. The only way to carry more speed is to exit faster from 5 or to have more power .

Last edited by CanAutM3; 04-06-2012 at 04:22 PM.
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      04-05-2012, 09:30 PM   #12
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Quote:
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I think maybe if you are getting away with it, you're going to slow!
If you are accelerating from the apex out enough that you need an upshift your cornering load is being reduced so the tires can take more forward thrust without loosing grip.Remember the traction circle!M-DCT also is great at allowing downshifts while trailbraking at the limit without causing the car to be more upset.
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      04-06-2012, 02:41 PM   #13
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Gerahead999 is absolutly correct about the differences between DCT and SMG. However, they both contain gears and clutches. I've been involed with clutch and gear box designs for over 30 years and you can't design away the problem completely. BMW did a phenominal job with the DCT and the computer control is extremely precise, but this is still a passenger car transmission, albeit a very good one, but if you abuse it it will fail. So if shifting in S6 is your thing, do it. But if you think its improving your lap times you're kidding yourself. Does it change the speed of the car? I doubt it. Does it put extra strain on the transmission? Absolutely. Does it unbalance the car? Sometimes.
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      04-06-2012, 03:04 PM   #14
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Quote:
Originally Posted by jvitas View Post
Gerahead999 is absolutly correct about the differences between DCT and SMG. However, they both contain gears and clutches. I've been involed with clutch and gear box designs for over 30 years and you can't design away the problem completely. BMW did a phenominal job with the DCT and the computer control is extremely precise, but this is still a passenger car transmission, albeit a very good one, but if you abuse it it will fail. So if shifting in S6 is your thing, do it. But if you think its improving your lap times you're kidding yourself. Does it change the speed of the car? I doubt it. Does it put extra strain on the transmission? Absolutely. Does it unbalance the car? Sometimes.
Maybe a little. The higher the DCT setting, the bigger the "surge" when shifting, so more of the inertia of the engine is converted in forward thrust instead of dissipating it as clutch slippage and heat...
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      04-06-2012, 03:17 PM   #15
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Quote:
Originally Posted by jvitas View Post
Gerahead999 is absolutly correct about the differences between DCT and SMG. However, they both contain gears and clutches. I've been involed with clutch and gear box designs for over 30 years and you can't design away the problem completely. BMW did a phenominal job with the DCT and the computer control is extremely precise, but this is still a passenger car transmission, albeit a very good one, but if you abuse it it will fail. So if shifting in S6 is your thing, do it. But if you think its improving your lap times you're kidding yourself. Does it change the speed of the car? I doubt it. Does it put extra strain on the transmission? Absolutely. Does it unbalance the car? Sometimes.
I have tried running my car in the lower settings of 4 & 5 and found that the downshifts were slow and lazy compared to 6.The only time I notice "shift shock" is in the lower gears which are not being used at most of the faster tracks that I have run at.I find the 3-4-5 shifts are pretty dam smooth.
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      04-06-2012, 04:04 PM   #16
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      04-10-2012, 09:36 AM   #17
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I spend a lot of time at Road America which is a very high speed track with 3 long straights. I use 3rd, 4th, 5th and 6th. Based on the best locations to shift, S4 works fine for me. There are some areas, like the infamous "kink", where you don't want to shift in the middle of the turn. The cost of failure is just to high. S6 justs makes failure that much more likely.

As for S4 vs. S6 at RA, S4 works fine for me. I find it very smooth. I'm sure there are some differences from car to car. I paid $7K to replace an SMG II transmission in my 2002 M3. There are some DCT failures out there. I don't want to be one of them and repeat that experience.

BTW I really don't expect Bernie Ecclestone to call me one way or the other.
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      04-10-2012, 10:40 AM   #18
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2 questions:

As a 6MT user, shouldn't you have the correct gear selected for the track-out before you reach the apex, either by "handbag-holding" flippy-flappy paddles or "hairy-chested" heel-toe shifts, during straight-line or trail braking? Is this about down shifting during turn-in? I am confused about DCT throttle sensitivity and gear change abruptness in cornering with DCT

Can someone with a handbag help out a hairy-chested Luddite driving 20th century technology in the use of DCT on the track?

[There may have been some writer bias expressed in the above message]
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      04-10-2012, 12:56 PM   #19
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Quote:
Originally Posted by LiM3y View Post
2 questions:

As a 6MT user, shouldn't you have the correct gear selected for the track-out before you reach the apex, either by "handbag-holding" flippy-flappy paddles or "hairy-chested" heel-toe shifts, during straight-line or trail braking? Is this about down shifting during turn-in? I am confused about DCT throttle sensitivity and gear change abruptness in cornering with DCT

Can someone with a handbag help out a hairy-chested Luddite driving 20th century technology in the use of DCT on the track?

[There may have been some writer bias expressed in the above message]
With the closer gear ratios of the M DCT there are a few corners where from the apex to the corner exit point,you will pick up enough speed to require a shift.The one corner that really shows the benefit of this is corner 3 at Mosport.

Quote:
Turn 3
Turn 3 is slightly off camber with a deceptive entrance, and a nasty bit of curbing at the apex.

If your car has 'street' ABS unit, be cautious of extreme late braking from the far left side of the track as the track goes quickly right and the very, very end of the brake zone fully left, has a decrease in the 'Uphill Slope' that can trigger ABS intervention. Best to enter the corner 1 foot off the left edge and trail brakes aggressively into turn.

The natural camber slopes away from the apex, so cars tend to push out. To counter this, make a very deep entrance, and slowly bring the car in to the apex curbing. A bit of curbing sticks out into the track, and the actual apex runs along the curbing just beyond this point. If you can apex the turn 1 foot after all the curbing, there is a small section of track with neutral camber that will help hold the car and resist the negative camber - you will know if you hit it as your car won't shoot left.

An early apex will have the car bouncing off the protruding curb, and can easily leave the track to the left.

Exit the corner at the end of the curbing on the left, and move over to position yourself for turn 4.


In my old car with the 6 speed I would downshift to 3rd on corner entry and upshift past the exit curbing back up to 4th.

With my M-dct I downshift to 3rd on corner entry and halfway out to the curbing I run out of revs in 3rd and must shift to 4th while still turning.Doing this gives me a lot more exit speed as I am not under 6500 at the apex so the car is in the sweet spot of the power where it needed.If I was doing this in 4th and not shifting I would be a lot slower as I would be a lot lower in the power band at the apex which will also make the car tougher to balance on corner exit.
In my 6 speed car I did some in car coaching with trail & follow with some race licence students and found that a 500 rpm reduction in revs at the shift point reduced my speed at the end of the 3/4 mile uphill straight by 7-8 kph.You need to shift these cars just before the limiter to work best on the track.

http://www.trackpedia.com/wiki/Turn_...national_track

Last edited by Gearhead999s; 04-10-2012 at 01:17 PM.
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      04-10-2012, 06:44 PM   #20
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Quote:
Originally Posted by LiM3y View Post
[There may have been some writer bias expressed in the above message]
Really ??

Quote:
Originally Posted by LiM3y View Post
As a 6MT user, shouldn't you have the correct gear selected for the track-out before you reach the apex, either by "handbag-holding" flippy-flappy paddles or "hairy-chested" heel-toe shifts, during straight-line or trail braking?
In most cases this is also what is done with DCT, you essentially downshift while braking to be in the right gear to accelerate out of the turn. However, in some corners (as gearhead mentions), it is beneficial to upshift during track out to maximize the power band. DCT makes it easy, so why not use it. On the specific example I mention in this thread, some corners are taken flat out (no braking at entry). In these cases the cornering speed is lot limited by lateral grip but rather by entry speed. In this case, it is very beneficial to maximize the power band by shifting mid-turn rather than short shifting before turn-in.

Quote:
Originally Posted by LiM3y View Post
Is this about down shifting during turn-in?
This is another benefit of DCT. I can think of a very specific turn where I use it. It is at Temptation at Calabogie. It is a 180deg decreasing radius turn with an entry speed of about 85mph and an exit of 45mph. So with an entry speed of 85mph it is not wise to downshift in 2nd and 3rd is not the best gear to pull at 45mph. With DCT I can trail brake through most of the turn, downshift in 2nd at the apex (which is very late apex) and be in the power band to accelerate out.

Quote:
Originally Posted by LiM3y View Post
I am confused about DCT throttle sensitivity and gear change abruptness in cornering with DCT.
This is the beauty of the smarts behind DCT. It does a harsh power shift in a straight line and a butter smooth shift when the car is under lateral load. The original question of this thread was if that smart logic was also programmed in S6.

Last edited by CanAutM3; 04-10-2012 at 07:00 PM.
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      04-10-2012, 06:46 PM   #21
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might snap the back end out.. but that could just be fun
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      04-10-2012, 07:16 PM   #22
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Apparently we all have been doing Temptation wrong at Calabogie
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