Quote:
Originally Posted by xwcgt
Ok that explains part of it (the part that the redline is really not 7000rpm, but 6700rpm.. the graph i copied however said to shift at 6500rpm, which didnt make much sense to me.
Next, what do you mean by short shifting. is the 6700rpm the rev limit and also the "short shift" or do you mean to shift at an even lower RPM?
If so, that would not optimize acceleration thrust, as you can see from your graph, every single gear shift has maximum thrust before a shift up to the next gear. (even 4-5 and 5-6th, however, not as critical as the prior shifts)
mostly i want to understand the "blue power band " area highlighted. this is the max thrust force in each gear, but based on the gear spacing vs speed, certainly not the "powerband" for the car... that would be in the higher RPM ranges, all the way to whatever your redline is.
This is because at each shift at 6700rpm the thrust force is lower in the next gear, but you have to shift anyway, because its at its RPM limit.
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the light blue is the max available thrust region for this engine w/ this transmission, as such you get the best acceleration in that region.
the red shift lines are determined at the right end by the red line in the graph, the left ends are determined by the drops inherent in the gear stack. As long as the red shift lines have a positive slope you are gaining the ability to go faster, if the slope is zero then there is no gain in ability to accelerate, as the slope approaches zero the less is gained.
A full appreciation is requires the incorporation of aero data
here is a 993 RS/CS in max downforce configuration which is also max drag, the thrust is net including aero, the trans here is a g50/30 used in 993Cup and RSR, the full benefit of the closer gearing isn't derived because the street toque curve falls off too quickly at higher rpm, this is seen in the shift lines that go to zero slope on the 4-5 shift, the closer to zero slope the more benefit from short shifting
to get the full benefit of this gear stack a motor which sacrifices some lower rpm torque for some more higher rpm torque would be desirable.