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      07-07-2012, 07:55 PM   #152
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Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

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Originally Posted by m3alabama View Post
...another problem that gets to me is when people say an engine torque peak is where it creates max thrust. arggg as its the peak engine power equals peak thrust
Well you and these folks may both be correct or incorrect. The devil is in the details on what statement is being made.

The two facts to keep in mind do seem somewhat contradictory. You must separate in gear vs. at any given speed.
  1. The maximum instantaneous acceleration (force or thrust) occurs in each gear occurs at the rpm where the engine makes peak torque. This kind of sounds like the "incorrect" statement you are referring to. If stated this way it is 100% correct.
  2. At any given speed one can maximize acceleration by maximizing power output (this is basically equivalent to saying downshift until there is nearly no rpm left to find the maximum acceleration).

(Note, there are some corrections to these principles for parasitic drive train losses and inertias, however, from both a practical and theoretical perspective they are basically true.)

Another way to see this is that it is almost always better to downshift to gear n-2 or n-2, etc. from gear n even if you are in the rpm range of peak torque and peak acceleration. Why? Common sense informs us that the lower gears are better due to much more gear multiplication much more wheel torque and hence much more acceleration.