Quote:
Originally Posted by Sgop335
No problem guys. I graphed this in excel w data from my car. As mentioned earlier acceleration curve has same shape as the torque curve (i can demonstrate that) but their values vary vastly gear to gear due to gear ratio as shown below. Based on the analysis below One may appreciate high revving cars and in general the importance of transmission, gear ratios etc.
The analysis is a reasonable representation and explains the basics but obviously has assumptions.
1. No traction loss
2. Gear ratios used are 6spd auto from 2007 e92
3. Redline 7k, and no ecu nannies like torque limit
4. Shape of curve below will vary based on your tune etc.
5. No drag (altho drag will only make the higher gears worse)
and few more im sure
Graph below shows acc on yaxis and rpm on x. The shape of the curve which mirrors the torque curve will depend on your car. I have shown dashed lines to demonstrate if the torque falls off at a faster rate after 6k.
Well i think the graph shows it, riding on 1st acceleration is the highest, you can go 6500rpm+ on 1st and still have higher acc than anwhere in 2nd! notice this shift point advances forward (meaning shift rpm keeps dropping as can clearly be seen by the arrows) as you move UP thru the gears since the acceleration in the next gear keeps getting closer. Make sense?
Also notice the dashed lines - if your torque falls off quicker obviously the shift rpm reduces as can be seen clearly.
Something missing in this whole graph? HP.
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Sgop335
Thanks for the detailed info and graphing it. I think I understand the concept.
For a dummy like me, can I have a dumbed down answer?
I have custom tunes with stage 2+ hardware + inlets and have 1 93 octane map and one e60 map on and E90 n54 xdrive auto car.
For power levels in this range, what would the optimal shift points be (for the drag strip) for each upshift?
Maybe 5,800 RPM's? Maybe a bit higher for the 1 --> 2 shift?
Thanks!