You can calculate torque at the rear wheels but maximizing torque at the rear wheels is EXACTLY the same as maximizing delivered horsepower. It's basic physics and you can prove that in two or three lines of math. So, it's much simpler to think in terms of staying as close as possible to the horsepower peak of the engine by proper gear selection. For GT3's, where the horsepower is at the top end, it means holding the gear to redline.

 

Since horsepower is simply a mathematical construct derived from measured torque, I can't argue with you there. All I was pointing out is that not all engines, and certainly not all drivetrains, are engineered so that maximum acceleration occurs by shifting at redline. I would take it as a given that it should be the case with sporty cars, particularly GT-models Porsches, but a set of poorly-chosen gears can make redline shifts a far-from-optimal proposition.

 

I've never mathed it out but I think it would be interesting to calculate the area under the curve (tq and hp, between the shift points), to be a true'er indicator of 'real' power. No engine sits at it's peak power (or torque). It just passes through. An area under the curve type quantification would better characterize the real power you actual use when driving hard. Being shift point to shift point (figure shifting at redline just to be consistent), you would I supposed get a slightly different value at each gear.

Full disclosure, I'm a mechanical engineer (well, now I just boss other engineers around) so I should be able to do this. It's not that hard really. It would be interesting to see now these area under curve quantities compare. Might help explain how some cars perform better or worse than expected. Of course many other factors come into play, but I think this would be a better way to get a useful charaterization of the working power of an engine.

Anyone got the number for SAE?

Jon