View Single Post
      08-24-2008, 02:37 AM   #28
e46e92love
Brigadier General
e46e92love's Avatar
United_States
236
Rep
3,303
Posts

Drives: e92 ///M3; X3 (wife's)
Join Date: Nov 2007
Location: The East Side of Things

iTrader: (0)

Quote:
Originally Posted by swamp2 View Post
@Art and lucid: There is much interest in a greater resoultion of the accleration profile during the shift and hence you need many sample points across the event. 300 Hz is marginal given Nyquist to capture a great deal of the actual dynamics during the shift. I think longer term, if shifts get much quicker than 30 ms 500 Hz would be a good sampling to stick with. I am not very interested in the frequency content myself, enlighten me.



D3 is shifting faster by design. When it comes to perception the shortness is directly related to the smoothness. You can not add any appreciable change in velocity if the duration is incredibly short, again ΔV = a x t, if goes to zero so does ΔV. In the extreme who cares if a shift is slurred across 10 seconds if the acceleration were actually higher than during the non shifting period. Very likely non physical here but you get the point.

D modes are:
-Mathematically more jerk (surge)
-Psychologically smooth and very little surge
-Very short in duration

S modes (S4->S6, i.e. those that have surge) are:
-Mathematically less jerk (surge)
-Psychologically rough with great surge
-Significantly longer in duration

It is slightly contradictory, S4->S6 FEEL faster but aren't. The exact same phenomena happens with the shape of cars torque curve. Lumpy/peaky can feel fast but not be as fast.
So if you want the best shift times, i.e. the best performance times out of your car you leave it in D3 rather than S4-S6? Assuming you shift at all the optimum RPMS, it seems the best performance should come from S4-S6.
__________________

"...it's not about the money and not about the brand of the car, it's about handling,performance and passion......And that, no other car has all together like an M3........when you talk about the most complete car the M is invincible." --Tony Kanaan.
Appreciate 0