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03-30-2008, 12:36 PM | #243 | |
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Although I haven't seen TB on the track it is abundantly clear he has significant track time. As well I know nothing about your racing resume. But it SOUNDS from most of your posts that your money is not where your mouth is. |
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03-30-2008, 04:40 PM | #244 | |
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Unfortunately I think it will be a while before anyone here will be able to test the DCT with any accuracy..... 100Hz sampling won't pick up a claimed sub 8 millisecond shift, I don't think even the industy standard VBOXIII could resolve that (the measuring gear I use is made by the same company and is within -/+ 1% as accurate according to their own testing) |
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03-30-2008, 04:53 PM | #245 | |
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Out of curiousity, were you Wide-Open-Throttle in your graphics? Also, did you back off after 70 mph? Finally, SMG shifts are fastest from 3rd to 4th or 4th to 5th.....
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03-30-2008, 10:23 PM | #246 | |
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On top of this you clearly must agree that the time estimated from both curves disagree fairly dramatically. That is the biggest problem I see with this data and that was about the first point I made. Two conflicting curves, they give totally different estimates and do not match in the time domain. Who knows what the best conclusion is. Myself as well as most folks "in the know" seem to agree that 8ms shift times are not possible. There is a lot of claims about VW/Audi DSG accomplishing this, but more cerdible sources claim about 30ms. I think M-DCT will surely be in this same general neighborhood of times. Lastly on the accuracy of the VBOX. You have to be careful on your very definition of "accuracy". Sure I bet the system is 1% accurate for some measurements but similarly there is no way it is 1% accurate for all measurements. As far as requirements go 200Hz should get us to withing 10 ms (don't forget Nyquist) accuracy and that should be about the minimum. 500 Hz - 2 kHz would be much better for really figuring out the differences down to 1 - 5 ms which would be required to see differences between individual drivelogic modes. |
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03-31-2008, 04:19 AM | #247 | |
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T Bone was I WOT? Yes up to the point of shifting then off the gas and back on again ie. I didn't keep the throttle down during the shift (is that you you guys call a power shift????) |
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03-31-2008, 10:40 AM | #248 | |||
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Is that true? If so, that's just one more reason why SMG was and is a completely bad idea by BMW. Quote:
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03-31-2008, 11:31 AM | #249 | |
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03-31-2008, 12:13 PM | #250 | |
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Manual gearboxes, the rotary dial of cars.
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03-31-2008, 12:58 PM | #251 |
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Maybe slightly off topic here, but experiencing how quickly the revs build in this car in the lower gears, DCT will be instrumental in shifting close to redline. This will be much harder to do with the 6MT although I personally don't care about shifting at the latest possible moment since I am not going to race this car. In the manual modes, does DCT automatically shift up at redline under acceleration?
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03-31-2008, 01:06 PM | #252 | |
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But again it's a car which I wouldn't want to shift during a corner, that's the difference between SMG and DSG, dual clutch is really that good, when you watch the FifthGear comparison test of DSG vs Manual you will see that poor old Vicki wasn't tuned into the DSG car in the same way she would with the manual but it was still quicker. And that's with a car which automatically shifts up at the limit regardless if you want or not, DCT will improve on this because of the fact it gives you the option, but only if the shift is smooth when cornering. |
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03-31-2008, 01:14 PM | #253 | |
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Even with SMG or DCT, the BMW V8s and V10s build the revs so quickly near the redline that I upshift when the needle hits 8000 rpm. By the time my finger and SMG reacts, I am shifting at redline. My Dinan software gives a redline of 8400 rpm but after 8000 rpm, you don't get more power anyway on either the V8 or V10. Shift at 8000 rpm. On a related note, in auto mode, SMG / MDCT will use the optimal upshift programs. If you get a shorter rear end, WOT upshift at redline in auto mode won't work anymore....since the tranny computer reads the speeds sensors before shifting.
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03-31-2008, 01:24 PM | #254 |
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But that depends on where you would end up on the power curve after the shift. You should keep on going until you reach a point where power in the current gear is about to be less than the power in the next gear or are about to destroy your drivetrain. For the V8, that seems to indicate shifting at the redline.
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03-31-2008, 01:35 PM | #255 | |
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But this is precisely what BMW has figured out. You shift at redline to be in the meat of the powerband for the next gear. Where I felt BMW made the wrong compromise with the V8 is that they chose a flat torque curve below 5500 rpm instead of giving more torque in the last 2000-2500 rpm like the M5 / M6's V10. When you are accelerating, tracking, racing, you are really playing around with a 3000 rpm powerband.....if you can deliver power in this narrow band, you will be happy. The rest of the power band is for the street and unimportant.
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03-31-2008, 01:41 PM | #256 | |
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03-31-2008, 01:46 PM | #257 | |
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Sorry, I don't understand what you are asking?? Can you please restate what you mean and the scenario?
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03-31-2008, 01:50 PM | #258 |
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I was just saying the optimal shift point for fastest acceleration in the M3 seems to be at the redline, and DCT will allow one to do that more precisely compared to 6MT, that's all. I think you are saying the same thing, just that one should click at 8000 to get the redline shift timed right?
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03-31-2008, 02:11 PM | #259 | |
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Yes.... You just need to anticipate the shift or else you bounce off the limiter and it cuts power for what seems forever.... Also you lose less revs with MDCT....since the shift with 6MT takes longer your engine revs drop more and you lose more power (remember power is a function of torque multiple by RPM).
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03-31-2008, 05:37 PM | #260 | |
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I drove my friends 964 variant of the 911 many years ago and I spun it a couple of times because I lifted mid corner. Earlier 911s are reknowned as widow-makers because of this phenomena, aka, lift-throttle oversteer. It is induced as easily as lifting the throttle (let along trying to shift). People like Hurley Haywood have been able to actual use this to their advantage (along with turbo lag).....they would go into a corner hot, understeer and then lift, inducing oversteer thus allowing the car to rotate....during the rotation, they would mash the throttle and by the time the car was pointed the right way, the turbo would be back on full boost.... But very few have Hurley's skills to pull this off.
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03-31-2008, 05:47 PM | #261 |
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Have had enough experience of most modern 911 to know exactly what you are on about. They are getting better but it's still a different skill required to drive one quickly and you are correct you can use the lift off oversteer to your advantage but even the best don't always get it right. Out of all the cars being discussed the 911 will benefit most from dual clutch.
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03-31-2008, 06:48 PM | #262 | |
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03-31-2008, 11:20 PM | #263 | |
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I'd like to remind you that, if you'd like to be fast, you're generally not cornering at 10/10ths - particularly if it's a corner that demands a shift. No, it's not self preservation at work. It's just that if you're going through there at 9/10ths, you can get on the gas earlier so as to make it down to the end of the next straight faster than the other guy. The first corner of a series of bends? Maybe ten tenths. The last corner? Nine tenths. Slow in, fast out. In my experience so far, any corner where I upshift is one where exit speed is paramount for good lap times. Exit speeds suffer if you're on the ragged edge through any given corner, for obvious reasons. It doesn't matter if that corner flows into the next one, but it sure as hell does matter if you're heading out onto a straight. At NHIS, I had to upshift in three (THREE!) corners in order to get the best out of my SRT4. When done right, however, that car would eat E36 M3s for breakfast and not even burp. Bruce PS - I have yet to experience a vehicle where stability control doesn't kill lap times, so I always disable it. Last edited by bruce.augenstein@comcast.; 03-31-2008 at 11:53 PM.. Reason: Spelling |
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04-01-2008, 01:21 AM | #264 | |
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I wholeheartedly agree that more crude/slow/primitive systems hamper serious performance driving rather than help and this I know from both direct and indirect evidence. |
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