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03-18-2008, 08:28 AM | #89 | |
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03-18-2008, 11:31 AM | #90 | |
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I did a search last night on some of the crazy people who are mpg freaks and found this: http://www.crxmpg.com/accelmpg.html Accelerating briskly will yield a ~3% improvement in fuel economy versus accelerating slowly. As for the shift times, they matter for pure acceleration but for fuel economy, I don't think they matter at all (or at least it is noise). If MDCT puts in a "Hairy Hippie Legs" mode and it shifts 1-3-5 then sure, this will be more efficient than 6MT. Short of a special alogrithm for fuel economy for MDCT, there should be no difference between MDCT and 6MT (save the gear ratios).
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03-18-2008, 01:52 PM | #91 | |
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03-18-2008, 02:02 PM | #92 | |
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BMW shows the way...
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The downside, of course, is that you get this lunge-pause-lunge thing going, which is not very comfortable for either the driver or passengers. It seems to me that DCT may allow that driving style while still providing smoothness. Imagine! You get to haul some ass while explaining to your S.O. in the right seat that you're saving money, reducing foreign oil imports and attacking the global warming phenomenon, all at the same time. Cool. Bruce |
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03-18-2008, 02:38 PM | #93 | |
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To discredit your theory in favor of mine around shift times..... The steptronic has quicker shift times than a human and you don't see better fuel economy. Sure there are other factors like gearing, weight, drivetrain losses etc... To really think 0.5 seconds for 1st to top gears shift times will result in any tangible fuel savings....the logic doesn't flow.... The quicker you can get your engine to stoichiometric air:fuel ratio of 14.7:1, the quicker you can put the engine in optimal fuel conserve state for a low-load cruise. This is the key to fuel "economy" for the M3. Which means stepping on it until you hit cruise speed, which means 1 gear change for any legal speed limit in most countries..... 0.3 seconds is not going to affect fuel economy either way specially since you are off the throttle for shifting.
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03-18-2008, 03:21 PM | #94 | |
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If you are not doing any shifting in your drive schedule for comparison then of course shifting can not logically play a role. However, don't forget particularly in city driving how much shifting actually occurs, .5 s x big number = reasonable amount of time. Further don't forget the losses during shifting are multi faceted as I posted. You have to lift, and reapply the throttle, there are losses right there. The car definitely decelerates during shifting which is energy totally lost and has to be regained by accelerating, which in turn burns much more fuel than cruising by a large margin. There are some losses from the clutch as well. This debate is testable, just by a DCT owner, but would require great care to get unquestionable results. |
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03-18-2008, 04:51 PM | #95 |
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Help!!! I think I inadvertently drifted onto the Prius forum. J/k
Actually I find it all intersting. If the E92 has two MPG displays like my E36 I will not reset one fo the first 1200 miles or so and report back with my actual mileage on my DCT.
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03-18-2008, 07:42 PM | #96 |
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The Corvettes do have a CAGS system that does sometimes force a 1st to 4th shift, but as you experienced, it does not happen all that frequently. Plus, you can buy a simple after market part for about $25.00 that disables the "feature" if it becomes too much of a problem.
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03-23-2008, 10:33 PM | #97 | |
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See this thread.... http://www.m3post.com/forums/showthread.php?t=128525 16 mpg as I estimated As more data points roll in, it may improve to almost 17. M-DCT will not greatly improve this.
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03-23-2008, 11:40 PM | #98 |
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Still better than the M6. I could not manage more than 11.5. M5 is like a hybrid coming in at 15.
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