FORUMS
 5


05202010, 07:55 PM  #24 
Brigadier General

That's great. Hey, what's your indicated speed at exactly 3K rpm? It's 72 mph stock in 6th. My numbers suggest 85 mph, but don't know if I did it right. That'd have been PERFECT to me but from the factory; am not going to spend on that. Take care.


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05202010, 08:19 PM  #25  
Major General

Quote:
Tire diameters are: std. calculation: Without tolerances: [(265 x 0.4) x 2 + (18 x 2.54)] * pi = 2.10 m Michelin website: 63,360 divided by revolutions pre mile = rolling circumference in inches: For the 265/40ZR18 PS2 Michelin states 790 revs per mile so 63,360 / 790 = 80.202 inches = 2.037 m. Also, you can add a drag calculation to get Vmax as well. The M3 is first limiter limited and if removed drag limited. The tricky part of getting a Vmax calculation correct is knowing drivetrain and tire losses. See my post here.
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E92 M3  Space Gray on Fox Red  MDCT  CF Roof  RAC RG63 Wheels  Brembo 380mm BBK   Vorsteiner Ti Exhaust  Matte Black Grilles/Side Gills/Rear Emblem/Mirrors   Alekshop Back up Camera  GP Thunders  BMW Aluminum Pedals  Elite Angels   XPEL Full Front Wrap  Hardwired V1  Interior Xenon Light Kit  


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05212010, 06:08 AM  #26  
Second Lieutenant

Quote:
E36 M3 EVO 6 speed with 3,23 diff and 0,87 6th gear ratio could do theoretical 330 km/h (roughly; I don't remember exactly) E46 M3 6 speed and SMGII with 3,62 diff and 0,87 6th gear ratio could do theoretical 330 km/h (roughly; I don't remember exactly) Now E9X M3 only do theoretical (probably real) 302 km/h (which is better than previous 6MT final drives in terms of performance since it is possible to hit 302 km/h with a delimit M3 ) I had 3,64 Schnitzer shorter diff on my E36 M3 EVO coupe. I could hit the rev limiter in 6th gear, which was at 7600 rpm. It does 298 km/h real speed. (I'm talking about euro spec 321 hp M3 with full SS exhaust) Last edited by pride355; 05212010 at 06:49 AM. 

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05212010, 06:21 AM  #27  
Second Lieutenant

Quote:
This kind of therotical top speed (that is 302 km/) is really not BMW style. 

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05212010, 06:26 AM  #28 
Second Lieutenant

Tall gear ratios of 3th  4th and 5th gear used to bother me a lot when I had E36 and E46 M3s. On the other hand my 911 Carrera S had shorter 3th  4th  5th and 6th gears and only these gearings were enough to make the car faster than E46 M3.
Carrera S had a 308309 km/h top speed in 6th gear at the rev limiter which was just perfect. BMW used to have always 5 performance gears + over drive (in E36 M3 EVO, E46 M3, E46 M3 CSL, E39 M5) Now, with the DKG, it has 6 performance gears + over drive and 6MT E9x is just in the middle; not too short not too tall. 
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05212010, 06:31 AM  #29 
Second Lieutenant

Since 6MT will be revving higher in 6th gear, at lets say 180 mph, than DKG in 7th gear, stock vs. stock 6MT car would probably have higher top speed. (if we assume both cars are delimited)
However from 70mph to 170mph, with gear ratios advantage, DKG equipped car would be faster than 6MT. 
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05212010, 06:38 AM  #30 
Second Lieutenant

Here is a picture of my ex E46 M3, doing approx. 268 km/h (roughly 167 mph) @ approx. 7700 rpm WHICH means approx. 282 km/h (roughly 176 mph) @ 8100 rpm; in 5th gear.
BTW, I did 298 km/h ~186 mph in 6th gear (with the speedo error ) The Car had Superchips software and SS Race LTW exhaust. Last edited by pride355; 05212010 at 06:47 AM. 
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05212010, 09:29 AM  #31  
Major

Quote:
First I calculated the theoretical top speed following this: Quote:
Then what I have done is to apply a 15% "tyre distorition factor" (which basically is a manual factor adjusting for tyre compression at higher speeds) in order to come to an approximated true top speed. The 15% figure came by comparing my theoretical speeds at redline for each gear of the DCT versus the actually measured true speeds for a stock DCT as these were measured by GPS equipment from a reliable Greek auto magazine. I was happy to see that my 15% correction factor was uniform accross all DCT gears and yielded the same true speeds as those measured by the magazine. Then I applied the empirical 15% distortion factor to all gears of the 6MT. The true top speeds I came up with are 302.3km/h for the 6MT and $321.4 for the DCT (assuming no electronic limitation). Last edited by gr8000; 05212010 at 09:34 AM. 


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05212010, 09:39 AM  #32  
Major

Quote:
I would be helpful if I could upload my spreadsheet here but this forum does not offer this functionality yet... 


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05212010, 10:18 AM  #33  
Second Lieutenant

Quote:
I was only refering to gear box  diff  tire diameter calculation.. 

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05222010, 02:42 AM  #34  
Major General

Quote:
Coincidentally our calculations (mine based solely on hp (with losses) and drag alone) agree quite closely. Your 302 km/hr is 187.6 mph, I get 186 mph.
__________________
E92 M3  Space Gray on Fox Red  MDCT  CF Roof  RAC RG63 Wheels  Brembo 380mm BBK   Vorsteiner Ti Exhaust  Matte Black Grilles/Side Gills/Rear Emblem/Mirrors   Alekshop Back up Camera  GP Thunders  BMW Aluminum Pedals  Elite Angels   XPEL Full Front Wrap  Hardwired V1  Interior Xenon Light Kit  


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