Quote:
Originally Posted by Boss330
Your knowledge on these subjects are really impressive!!! Thanks for your input and sharing your knowledge with us!
Would this BMW 523i have a "optimum shiftpoint" at around 4250rpm for max acceleration?
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If you believe I am saying or calculating that a car should shift at the point of peak torque (or highest rpm of torque plateau) you are very much misunderstanding (4250 rpm in this case). One must compute the vehicles thrust (accelerative force) AFTER losses and plot these vs. speed and gear. Since this car is not a performance car getting the actual torque or power curves was quite difficult (I could not find them). Thus I just used known peak values and let CarTest curve fit to construct the entire curves. It did not quite result in a totally flat torque curve between 1500-4250 rpm (which is the spec I could find) but was flat enough, maybe slowly and steadily declining from peak at 1500 rpm to 19X or so ft lb at 4250 rpm. Even finding the gear ratios wasn't fast but I did find those. Using all of this information I computed the ideal (rounded) shift points to be:
1-2: 7000 (redline)
2-3: 6900
3-4: 6700
4-5: 6600 (won't reach here, drag limited in 4th at ~135 mph)
5-6: 6300 "
Hope that helps.
Too much (boring) work to do the other car you mentioned. Build a spreadsheet, run the numbers yourself, if it very insightful and certainly non-trivial.
P.S. What are your calculations Jonjt?
And of course, last but not least, let's get back on topic.