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      05-21-2010, 09:29 AM   #31
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Drives: E92 M3 - DCT
Join Date: Jul 2008
Location: Athens, Greece

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Originally Posted by pride355 View Post
If the charts located at this link is at the rev limiter, then E9x M3 could do therotical 316 km/h in 6th gear; not 302 km/h which surprised me a lot when I first read it and responded immidiately with the above post.

This kind of therotical top speed (that is 302 km/) is really not BMW style.
The figures posted are an approximation of the true speed i.e. the 302km/h is my "desktop" approximation of the true top speed of a 6MT M3 (assuming no electronic speed limiter). Here is my methodology:

First I calculated the theoretical top speed following this:
Originally Posted by swamp2 View Post
Tire diameters are: std. calculation:
Without tolerances: [(265 x 0.4) x 2 + (18 x 2.54)] * pi = 2.10m
The theoretical top speed for the M3 I came up with based on the above (assuming 19" 265/35 tyre) is 315.4km/h for the 6MT and 335.4 for the DCT.

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; 05-21-2010 at 09:34 AM.