View Single Post
      03-26-2008, 05:13 PM   #70
swamp2
Lieutenant General
 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

Posts: 10,142
iTrader: (1)

Quote:
Originally Posted by T Bone View Post
The Cartest2000 simulations don't support significantly faster acceleration for the MDCT.....the reason the MDCT is faster is quicker shift times and not gear.
Depends on what you mean by significant and depends on the particular contest as well.

BMW has released official acceleration differences, but yes only to fairly low speeds and indeed a couple tenths here or there. However, my CarTest runs are quite consistent with BMW results. We are only talking about a couple tenths advantage up to 100, past 100 at 120, 140 and 150 the time to speed advantages grow to about 0.5 to 1.0 seconds. However, time to speed contests to Vmax are won by the 6MT. It is all put in much better perspective looking at simulation results for distance vs. time, M-DCT will have about 100' or 7 car lengths at 150 mph. It should get the jump right from the start and continue to pull away most noticably at each shift.

On to what matters more, shift times or transmission ratios. You need to be really clear to make this comparison. Are we talking about time to a given speed, in gear roll ons with time for speeds 1 to speed 2, distance ahead in a race, etc.? What I can say is that simulation indeed supports your claim that MORE benefit comes from the shift time advantage as opposed to gear ratio differences for timed acceleration runs to a given speed.

For in gear time, from speed 1 to speed 2, without allowing gear shifts M-DCT really exhibits a significant advantage over 6MT. All of this is obviosuly from gear ratios. Lastly giving both cars a chance to use the most appropriate gears this advantage grows even stronger for times from speed 1 to speed 2 ALLOWING shifts. Here both the shift times and gear ratios really contribute.

As you know when in the 400-500 hp range it takes a huge addition in power to make even minor improvements in performance. Simply the law of decreasing marginal return. 20 hp is absolutely significant and I stick by my conclusions that M-DCT is good for about an equivalent +20 hp, +20 ft lb compared to 6MT.

Cheers.
swamp2 is offline   United_States
0
Reply With Quote