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      03-14-2013, 01:35 AM   #29
Vic311
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Drives: 2011 e92 M3
Join Date: Dec 2012
Location: NY

Posts: 1,469
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Speed of shifting isn't measured by units of power rather by milli-seconds..your formula is extrapolating data not measuring it.

Would you measure air temperature by air pressure units or speed/acceleration by units of weight?

You can choose to look at it this way, but to make a statement that a DCT is good for 25-50 hp is just silly.

Quote:
Originally Posted by swamp2 View Post
Yes, really.

Try a search on the forum if you are curious. Many threads and posts, both from me and some others arriving at our conclusions using both simulation, formulas, testing and magazine results.

It comes down to shift time reduction. If you assume the DCT can shift in about 50-100 ms which is a very reasonable number supported by a large variety of evidence, along with the fact that a good MT shift is probably in the 0.4 s range, just do some simple math. You save about 0.6 seconds over two shifts in the quarter mile. The math really is that simple time saved shifting directly translates to just about the same time spent over a certain fixed distance. For a 3700 lb car use the basic formula for a 1/4 mi time:

ET = 6.1178 (weight/hp)^1/3 (ref:http://www.stealth316.com/2-calc-hp-et-mph.htm , weight in lb, hp obviously as hp)

And you will find almost a 63 hp requirement to have this much gain!

This is a very rough version, I don't think the difference is trult that large, it is however, quite significant, no matter from what source you draw your conclusions.

Bottom line, if you line up two M3 with equivalent drivers, tires, road, launch, weight, one with M-DCT and one without. The M-DCT car will very decisively pull on the 6MT car. There is even a big enough difference that the 6MT driver could be quite a bit better and the M-DCT would still have the advantage.

Similar advantages exist on a track due, especially when 3rd gear is used a lot, which on many track it is. There is 12% more torque to the wheels comparing both cars in 3rd gear simply because of the gear ratios.

back at ya...
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