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11272013, 08:58 AM  #89  
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(correct me if I am wrong, guys) 


11272013, 08:58 AM  #90  
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EDIT: And I'll add that a figure of 34503550 lbs makes absolutely NO SENSE in line with BMW's quoted weight savings. You understand that the 3704 lb figure for the E92 M3 was EU weight correct? Do the math: BMW's listed weight for the E92 M3 was 3704 lbs. EU weight is calculated as the following: Weight of Car with 90% fuel, 68 kg driver, 7 kg cargo. Subtracting the 75 kilograms for driver and cargo, you're already down to 3539 lbs. When you add back the remaining 10% of fuel from the 63 liter tank, you're only up to 3550 lbs  and that's CURB WEIGHT (all fluids, including 100% gas, no driver or cargo). You're claiming we should anticipate that the new M4 might (you gave a range, but that range extends all the way back to 3550 lbs) have the same exact curb weight as the E92 M3...? Last edited by Sapper_M3; 11272013 at 09:34 AM.. 


11272013, 09:09 AM  #91  
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You're talking about weight loss percentages "straight from BMW," but Albert Bierman himself is the source of the 3306 lb speculation. I won't do the math for you, but read on for the "1500 kg" figure offered. http://f80.bimmerpost.com/forums/sho...d.php?t=915648 Now, in Biermann's defense, he never unequivocally states that they ACHIEVED the sub1500 kg goal, but he's the one putting that number out there, and he even uses it as the rationale for costcutting in other areas ("we saved money to spend on cutting weight more aggressively" followed immediately by his unsolicited offering of a 1500 kg weight figure). If the car is 150 lbs heavier than this claim, there will be a lot of unhappy folks, and BMW/M will only have themselves to blame. Car mags aren't coming up with these numbers on their own. 


11272013, 10:28 AM  #92  
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11272013, 10:39 AM  #93  
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3374 lbs in the lightest trim possible wouldn't be a bad figure, butagainAlbert Biermann, the HEAD of development for BMW M, is the guy throwing out the "less than 1500 kg" figure. If they don't intend on delivering a product that at least approaches this, they should expect people to be miffed. Last edited by Sapper_M3; 11272013 at 10:42 AM.. Reason: Clarified that Biermann is the head of BMW M Development. 


11272013, 10:50 AM  #94  
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Power = Work / time Power = Force x Distance / Time = Force x speed In the polar referential: Force=Torque Distance=Rotation Time=Time Work = Torque x Rotation Power = Torque x Rotation / Time = Troque x RPM (agular velocity) Hope this helps 


11272013, 11:09 AM  #95  
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I guess my issue begins with my optimistic (assumption) that some amount of integration of the Torque vs RPM graph would ever give me power, when in reality (I believe now; someone correct me if I'm wrong) it never will. Torque and Power themselves are certainly directly related (in fact, by distance and timethe same variables that make up the rate/angular velocity that is RPM), but the Torque vs RPM curve does not enclose an area equivalent to power. Now a Torque*Angular Distance vs Time graph (essentially a Work vs Time graph), that would be both generally useless for most purposes and PERFECT for giving me power by summing the area underneath the curve. 


11272013, 11:33 AM  #96  
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11272013, 11:38 AM  #97  
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Torque * RPM is indeed power, which is why CanAutM3's math earlier (arriving at reasonable numbers) worked. But the area under the torque vs RPM curve is NOT the power, which is why CanAutM3's math showed summing the area under the torque curve does NOT arrive at a reasonable number. Further Explanation: Torque vs RPM is indeed power, but your formula in this post is incorrect. "P \int T dR" is wrong. Instead, it should be rendered "P \int T*D dS" where D is the angular distance, and S is time (to avoid confusion with the T we used for Torque). Last edited by Sapper_M3; 11272013 at 11:40 AM.. Reason: Changed the variable for "time" to avoid confusion with the "T" for Torque. 


11272013, 11:45 AM  #98  
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11272013, 11:59 AM  #99  
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And despite the relationship between angular velocity (RPM), which is distance/time, you can't perform the integration you're suggesting. To get power you need to integrate Torque * Distance with respect to Time. Integrating Torque with respect to Distance/Time is NOT the same thing. For proof, look up to one of CanAutM3's earlier posts. Doing integration of the curve manually by summing up the area results in nonsensically lower power figures. Try it yourself to see. 


11272013, 12:01 PM  #100  
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Distance in the polar referential is rotations (rads, a nondimensional unit; 1 rotation = 2 pi rads). So rotations in the polar referential is a "real distance". 


11272013, 12:55 PM  #101  
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As has been stated above, BMW has said that a similarily equipped F8x M will weigh 80kg less than a comparable E9x M3. The E9x M3 has also been quoted as having a curb weight of 1580kg (3480lbs), which doesn't include the driver (165575=1580kg). From this we can deduct that the lightest F8x will weigh 1500kg (or a bit less) WITHOUT driver, but WITH 90% fuel and all fluids. So, yes the standard F8x ready to drive, but without driver, will most likely weigh around 1500kg or 3303lbs. Add the driver and we are at 1575kg or 3469lbs. Last edited by Boss330; 11272013 at 01:17 PM.. 


11272013, 02:15 PM  #102  
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11272013, 02:46 PM  #103  
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And as I understand the US weight of 3704lbs, that is the curb weight with the DCT wheras the EU weight is with manual (20kg difference). Add the extra 10% of fuel (US has a full tank) and the 1675kg (EU weight for DCT with 90% fuel and driver) and 1681kg (US weight of 3704lbs with 100% fuel, driver and DCT) makes sense. The extra 10% of fuel probably accounts for the 6kg difference between a EU DCT at 1675 and a US DCT at 1681kg. Deduct the 20kg for the DCT and you end up at 3484lbs (1581kg) US weight WITH driver, or 3318lbs (1506kg) US weight WITHOUT driver! So, a US manual M4 without driver and with 90% fuel should also weigh in at 1500kg Last edited by Boss330; 11272013 at 02:58 PM.. 


11272013, 03:09 PM  #105  
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Sunroof: 44lbs Power seats: ~15lbs NAV: ~12lbs Fold Down Seats: ~3840lbs Ehanced Audio: ~20lbs EDC: ~10lbs DCT: ~58lbs TOTAL 197lbs Most of these are options on the F8X as well if I understand it correctly. 


11272013, 03:40 PM  #106  
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US weight: 1681kg EU weight: 1675kg (confirmed with DCT) Difference between US and EU is 90% and 100% fuel. The M3 has a 63l fuel tank. 10% of 63l is 6,3l. Density of petrol is 737.22 kg/m3 and those 6,3l extra will weigh in at 4,64kg extra weight, getting us to 1679,64kg... Also according to EPA regulations, options that are expected to be installed in more than 33% of the sold cars must be included in the curb weight. I'm pretty sure BMW expected the DCT to be sold in more than 33% of the M3's http://www.gpo.gov/fdsys/pkg/CFR200...86180301.pdf Quote:
§ 86.1832–01 http://www.law.cornell.edu/cfr/text/40/86.183201 Quote:
Last edited by Boss330; 11272013 at 03:47 PM.. 


11272013, 04:06 PM  #107  
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Getting pretty close to that 3704lbs... PS: fixed the DCT line, IIRC 45lbs is what has mostly been quoted in the past. I still doubt we will see many F8X on the street at 3300lbs... 


11272013, 04:13 PM  #108  
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And yes, most F8x will have DCT and a few options, so around 34003450lbs for the majority perhaps? But then again, how many will have the CCB option that SAVES weight 


11272013, 04:54 PM  #109  
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No cars perform acceleration runs without a driver. That leads me to say that weights should always be reported with driver, with fluids, 90% or 100% fuel (what ever you like). I'm not too fussed about 7 kg of cargo. There is not a chance in hell that we'll see a single new M4 with driver weigh in at less than 1500 kg... 1500 kg with no driver, no DCT, no cargo is within about 10 lbs of "80 kg lighter than" 3704 lb assuming it includes DCT. Specifically 1500 + 68(driver) + 7(cargo) + 20(DCT) + 80(difference) = 1675 kg = 3692 lb. I sure hope the 1500 kg figure does not include CSiC brakes... Thus APPLES TO APPLES for a US DCT car is the following: E92 M3: 3704 lb F82 M4: 3528 lb (again simply 80 kg less) Edit: And this 3528 lb should be very close to what the US website/brochure will list. My earliest estimate/calculation of the car's weight was about 3590 back in December of 2010...
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11272013, 05:28 PM  #110  
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Lot's of internet car experts like to talk about good old "areas under the curves"...torque or power. They are largely meaningless physically but the point folks are trying to talk about is somewhat relevant. They are basically meaningless because in any accelerating vehicle rpms don't grow linearly with time and they way they do grow with time depends on gear and drag... Comparing two torque curves where one is always making more torque does indeed have more area under its curve of course said engine is also consistently making more power and that is what matters... I think the confusion generally goes like this: How quickly velocities can grow depends on the work done (ΔE = W, workenergy theorem). When forces vary work must be integrated. You can integrate F*v dt (power vs. time) or F dx (force vs. position). Both expressions contain force the instantaneous force applied to the ground depends on the engines torque. Q.E.D. let's just integrate torque (in some loose definition vs rpm) vs. the only thing we typically see torque plotted against  rpm. To discuss anything in regards to integrating one must carefully distinguish between engine parameters (rpm, rotations, etc.) vs. "real world" parameters (time, distance, etc., these are what the car does, not the engine).
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