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03-27-2012, 07:10 PM | #1 |
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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... |
03-27-2012, 07:47 PM | #2 | |
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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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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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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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04-05-2012, 08:49 PM | #9 | |
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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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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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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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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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04-06-2012, 03:17 PM | #15 | |
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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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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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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. 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
Watch Scott Maxwell in the factory Boss 302 R Grand Am Cup car. Last edited by Gearhead999s; 04-10-2012 at 07:26 PM.. |
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