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03-26-2008, 09:21 PM | #89 |
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Numbers and physics check out ok to me. However, I'm no mechanical engineer, my degree is in Physics.
Oh, BTW, one "G" is 9.8m/s^2.
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03-26-2008, 10:51 PM | #90 | |
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1. How close are your flywheel mass and radius? I know we don't have actual numbers and I know you are using estimates, but what is your guess? 2. The clutch friction will cause energy to not be conserved. However, even with a lossy joining of spinning disks angular momentum will be conserved. This is the begining of the correct calculation but since you have linear and angular momentum/energy it is a bit more complicated. I don't think you can even calculate the velocity change without a reasonable estimate of the total clutch back moment of intertia. 3. Even if energy were conserved, E = .5 * m * v^2 as you stated, but didn't you leave off the 2? So you are off by sqrt(2) = 1.4 in the 20.32 number. It is 1.4 x larger. 4. Footie either does not own a calculator or does not even understand the concept of a percentage (see the recent top speed threads), don't even bother with the forumlae and physics. @ersin: Come on I expect better from a fellow physics person |
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03-27-2008, 12:26 AM | #92 |
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I will be driving mine sometime during the week of April 7th.
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03-27-2008, 12:38 AM | #93 |
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The Veyron doesn't have the jerk because they don't want it. With 1000 HP, any slight increase in acceleration would cause it to lose traction instead of accelerate. The F1 cars also have seamless shifts because of their massive HP:weight ratios. Any slight jerk will cause unbalance.
So, if you have ENOUGH HP, you want smoooooth. If you don't have enough HP, you want all that energy transferred to the wheels during gear shift. In theory, the best tranny is the CVT. The CVT would give you NOTICEABLE improvement over the DCT. Only problem is that the CVT has not yet been able to handle the torque. Maybe one day, M3s will be CVT. How boring would that be? LOL. Maximum HP all the time during S6 mode and you can have an "E" mode for maximum efficiency for fuel economy to prevent the gas guzzler tax. |
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03-27-2008, 12:43 AM | #94 |
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So I'm lazy. It's late. I need to get some sleep. Good night.
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03-27-2008, 12:43 AM | #95 | |
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I am just guessing on the flywheel dimensions. I have seen a number of them out of cars so its probably not that far off. Weights typically run 10-22lbs. Still its really hard to estimate I since the shape is far from ideal.
Clutch friction (and tire slip) will consume some of the energy. The calculation is much more complex. You have an unknown additional mass in the engine. There is the fact that the clutch engagement needs to be treated more like a physics collision (inelastic) and conservation of momentum needs to be addressed. 4: Yes. I simply wanted to make it clear that the energy has to go somewhere. I figured even footie could understand that. If you could easily just make energy disapear then things like falling off building wouldn't be a problem. Quote:
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03-27-2008, 12:45 AM | #96 |
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Precisly you want as much energy transfered to the rear wheels as possible WITHOUT causing more than a 4-12% tire slip (depending on tire type).
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03-27-2008, 01:58 AM | #97 |
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I think we are all missing the point here. Lets stop trying to guess and hold out for a week or two. My guess is that if you want DCT to be seamless it will be with no serious impact on acceleration. The big question is whether the Auto mode would be a failure like the one in the SMG cars. After all we would all like the convenience of an auto from time to time.
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03-27-2008, 02:21 AM | #98 | |
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One point to clarify is that when you use a bit of science (be it engineering, math, physics, materials science, etc.) along with knowledge about similar cars or components, throw in some simulation and just good old common sense you really can get pretty darn good "predictions" about the future. I think being able to make such predictions is enormously rewarding. Sure we get to stroke our own egos a bit when we get it right, but that is simply part of what makes it fun. So in short, we (especially the M-DCT "club") are excited and anxious and having some fun. Hence the answer is no, we won't just wait. As to your big question - I think it has already been answered. My "guess", as well as that of the majority of whom I believe to be "in the know" here, has been all along that the auto mode in the more comfortable settings will be incredible and incredibly better than SMG - very much a match for a good automatic. This has been more or less confirmed in multiple locations. First in early speculations, next in the big M-DCT press release from BMW, next in my post about my visit with a dealer in Frankfurt and lastly partially confirmed again right here in this thread. |
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03-27-2008, 03:39 AM | #100 | ||
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Enigma and Swamp,
You guys are still think of DCT like you would SMG, eg. one clutch controlling all of the gears. The jerk is engineered, please go and get a bit of advice on DCT and dual clutch technology before ranting. Quote:
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P.S. And not a jerk in sight. |
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03-27-2008, 04:26 AM | #101 |
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In manual mode and in setting S6, jerkiness is a must.
Would be a big F..... mistake from BMW if it was smooth gearchange in S6 mode. I want to feel Im driving. Its more important that automatic mode is smooth than the fastest setting in manual mode. |
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03-27-2008, 06:23 AM | #102 | |
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I'm just praying that there is no noticable delay between pulling the paddle to the shift actually happening (especially in the fastest modes) |
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03-27-2008, 06:35 AM | #103 |
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I have seen weights of the Bugatti up to 4300 lbs which is a good deal and the car is 6" shorter in length and 9" shorter (height) than the M3. So likely the tranny is a good bit more robust, likely weighs a lot more than the M3s. I think part of the DCT is not wanting to add too much weight to the car and likely on the Bugatti the weight was not as big a deal as it has more than double the power to throw around.
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03-27-2008, 06:36 AM | #104 |
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03-27-2008, 08:03 AM | #105 | |
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03-27-2008, 08:05 AM | #106 |
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Good Job with the review translation South. I think I speak for all when I say you bring great contributions to this forum.
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03-27-2008, 09:27 AM | #107 | |
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I test drove a Toyota Highlander Hybrid that had CVT. It sounded and felt like the thing was constipated. Strain, strain, strain. I hated it! Bleh.
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03-27-2008, 10:57 AM | #109 | |
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Why don't you start a thread on a how the 6MT knob feels, is it touching your soul? Are you intimate enough with the car?
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03-27-2008, 11:41 AM | #110 | |
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Best regards, south
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