10-08-2013, 03:50 PM | #89 | |
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Regarding the straight line acceleration debate, if you stumble across any sources with trap speeds of equivalent xDrives and RWDs at various intervals over a quarter mile, I'd be curious to see at what point the RWD starts posting faster speeds on it's way to overtaking the xDrive...
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10-08-2013, 03:57 PM | #90 |
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300hp, there's no argument. No one's disputing the fact that nearly all automotive reviews indicate that xDrive is quicker off the line and on a limited run around the track. All people are saying is that this does not necessarily mean that the AWD is quicker overall. I can be the fastest man in the world in the 100 yard dash; it doesn't mean I'm the fastest over a mile.
If you want to refer to magazines, take a look at this article: http://www.caranddriver.com/comparisons/why-we-nixed-the-awd-bimmer-page-4 . It basically says that the AWD is faster off the line--0-60, 0-90, 0-100--but if you continue to accelerate beyond that, the RWD will overtake it. Why? Because the AWD launches quicker--i.e. has a quicker initial burst--it takes an initial lead over a car with the same engine. Why does the RWD overtake it, because if you move past that initial burst, it is a little faster. Period. AWD is faster in short sprints. RWD is faster in the long run. Can you agree with this? |
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10-08-2013, 04:17 PM | #91 | |
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ATS The awd was wearing all seasons and the rwd was wearing summers. Both ATS have one of the best suspension setups this side of the Corvette. Both were tested by motortrend on their testing grounds. Bottom line is the ATS AWD was handicapped by the all seasons but the results are actually pretty good for the AWD IS350 I think both awd and rwd were wearing similar tires, its possible the awd was wearing all seasons since this is typically how Lexus options them. Both cars tested by motortrend however in this case, the AWD has a 6 speed auto and the RWD has a sport suspension and an 8 speed auto. Bottom line is the AWD was handicapped by the all seasons, transmission andlack of sport suspension and here again the results are actually pretty good for the AWD If you have time take a look at figure 8 times compared to track times for cars in the Best Driver Car 2013 to see how predictive that figure 8 test is. Thanks for being open minded about this
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10-08-2013, 04:28 PM | #92 | |
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I have no interest in the which is better argument. However I am putting some of the theories that have been put forward to task to see how real world observations support or conflict with these theories. So for example we know that xdrive reign ends at 120mph, so lets look at this more closely 0-60 xdrive leads by 0.2s time taken for rwd to eliminate lead 18s speed at which lead is eliminated 120mph Would you not agree that it seems to be an eternity for this 0.2s lead to be elimated, the two cars are almost about to reach the speed limit if optioned with speed limit increase option. If not I think that limit is around 120mph. I have even posted times for other rwd vs awd comparisons from 45mph to 60mph, eliminating the awd traction advantage. I then posted figure 8 times for the same cars comparing rwd and awd. Agreed Figure 8 is just one test but if you ask yourself the question, how predictive is this test, I promise you if you take the time to look into it further the data is interesting. I have not said AWD beats RWD around a track, what is more useful is the track data which these lazy journalists seem not to do when they have both cars
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10-08-2013, 04:31 PM | #93 | |
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I recall quite a range of 0-60 test results from various magazines, ranging from 4.6 seconds to into the five second range. I appreciate this is vague; I do not find bench racing interesting. I am sure however there are others who can regurgitate the numbers precisely. This large variable range is for one individual car variant, an AT RWD 335i.. These results are well over the 10% variability I referenced earlier. The numbers are not consistent even for a single car. Accordingly, one cannot compare test numbers across platforms and claim the numbers "prove" one is faster or somehow better. Only general conclusions can be supported by the data, and then only if the difference is substantially greater than 10% - 15%. A 0.1 or 0.3 second differences is absolutely meaningless and well within testing error/variability. On the other hand, one can amusingly "prove" a 335i F30 AT RWD is faster than a 335i F30 AT RWD. Or much slower. Weird, huh? Back on the specific topic, if one cannot feel or experience the increased understeer of xDrive over RWD and/or do not care - buy the xDrive if you otherwise want it. All of this is academic if you cannot tell. For me, the increased sense of plowing through turns caused by xDrive is immediate, pronounced and obvious even on slow turns. It is increasingly annoying with speed, such as an entrance clover-leaf. I can easily go 50 MPH with either xDrive or RWD in these circumstances, but the RWD feels as if it is only using 50% of its cornering capability; the xDrive complains that it is using 75% or more of its ability. I find this frustrating. Others do not sense it and/or do not care. Yes, if the front wheels of the xDrive begin to actually slip, the system will direct less torque to the front wheels, decreasing understeer. But this is a band-aide, only responding to the condition xDrive itself created. Plus, the xDrive car feels dreadful at this point. Full understeer has been invoked and the car is now reacting, changing its FWD and RWD drive balance. This further unsettles the car mid-corner - the worst possible time for this to occur. The technical term for this is "yucky." With RWD, this issue never arises. The full traction of the front wheels is always available to turn the car. It will always feel more willing to turn because it is, in fact, more willing. |
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10-08-2013, 04:42 PM | #94 | |
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C&D 4.6 RT 4.9 (however this is w/out 1 foot rollout which they described as 0.3s IIRC, gets you to the same place as the other 2) I threw in the towel on this a while back
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10-08-2013, 04:54 PM | #95 |
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We need some humor around here, maybe lets let this topic go
Sunday night in the Republican household. Responsible Parent: Time for bed! Republican Children: Okay, but I want a cake. A layer cake. With chocolate icing. And sprinkles on top! Next Sunday night. RP: Bedtime. RC: Cake! 42 weeks later. RP: Time for bed! RC: I said I want cake! RP: We've had this discussion for 42 weeks now. No cake. RC: CAKE! RP: No cake. RC: I'll burn the house down! Everybody: Go to your room. I support neither party, but anyone with toddlers can relate to this
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10-08-2013, 05:32 PM | #96 |
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Don't forget the 5.3
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10-08-2013, 05:37 PM | #97 | |
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10-08-2013, 05:49 PM | #98 |
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That was manual transmission
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10-08-2013, 05:53 PM | #99 | ||
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However my point still stands, these two cars are now in a race to the speed limiter around the time this transfer is made
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10-08-2013, 06:19 PM | #100 |
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Has anyone considered that at each gear change the awd has the advantage of putting the power down more efficiently than the rwd. Since the transfer of power happens after the quarter, both cars, which were MT, are now in 6th gear and as everyone expects the rwd then gains it's much needed victory. Drivetrain losses and weight start to weigh in on the awd as it has no more traction cards to play. Isn't this the variable we were missing all along?
Again I am no expert on this but I am just taking a wild guess here
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10-08-2013, 07:35 PM | #102 | |
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http://www.caranddriver.com/features/lightning-lap-2009 Notice that the 335i in this instance was a COUPE. S4 3:10.8 vs 335i COUPE 3:10.8 http://www.f30post.com/forums/showthread.php?t=785729 This is the f30 SEDAN 3:13.2 |
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10-08-2013, 07:49 PM | #103 | ||
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10-08-2013, 07:56 PM | #104 |
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Didn't we have this conversation awhile back about the S4 vs 335i and about the figure 8 times on the S4 was better and you agreed with me?
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10-08-2013, 08:08 PM | #105 | |
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Maybe you wanted to say the slalom numbers which at the time I was dismissing as nonsense since the S4 slaloms badly relative to the 335i but we know that is irrelevant since the S4 tracks better.
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10-08-2013, 09:07 PM | #106 | |||
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10-08-2013, 09:43 PM | #107 |
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AWD has better traction in inclement weather, but DSC and other electronic controls mean that with proper tires, RWD is not the animal it used to be, and can confidently be used on the snow nowadays. Given the mpg hit, I'd rather pass on the AWD except in a place where it snows most of the year...
Speaking of pure performance, AWD does have a traction advantage at corner exit (and could post quicker 'figure' times), but it will understeer more and detract confidence on entrance. It is a matter of weight distribution. AWD is heavier from the front, which is bad. RWD also offers better throttle control mid-corner, one can oversteer the car with the throttle, which is (often, depends on bias) not possible with AWD. |
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10-08-2013, 09:59 PM | #108 | ||||
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However you still seem to be ignoring the rolling start numbers (45-65mph) for the ATS awd vs rwd and the 335i xdrive with PPK vs the 335i rwd no PPK. It does not appear the rwd has more grunt at 45mph than it did at 0mph. (Remember the theory was it's all over for awd when it's a rolling start). I will jokingly suggest that it appears any race that begins in the 0-45mph range will have to head toward the 100mph zone for the transfer to be made. It's a race to that speed limiter all over again. When one says at some stage the lead is transferred its generally a forgone conclusion that the lead was being eaten away until that point. It goes without saying. If I told my toddlers that I will catch up with you I think they understand that I mean even if they start to run I am faster than them. It's common sense
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10-08-2013, 10:00 PM | #109 | |
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10-08-2013, 10:05 PM | #110 | ||
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