I decided to start a new thread here because this is being discussed in various places. One thing that drives me crazy is car guys talking about car stuff - particularly performance - and believing in old wive's tales (like "always shift at the torque peak for best acceleration"). A knowledge of elemental math and physics allows us to figure stuff out without guessing.
The image below is of my latest iteration of a spreadsheet you can download at
http://www.bmwm5.com/greg/files/M5_Data.xls (27Kb)
I believe the math is correct, but would certainly appreciate it if someone checks me on this. The most waffled figures are the torque ones - I interpreted a dyno chart where 3 members' stock M5's returned very similar results. I multipled the torque figures (and I had to guess within about 10 lbs on those) by 1.15 since the chart shows torque as measured at the rear wheels and we want engine torque, which isn't a victim of drivetrain loss. If someone has the original M5 factory torque graph, I'd love to make these numbers more accurate. I am confident these numbers are good enough to draw many conclusions, however.
One conclusion is that you have more force at the rear wheels in a lower gear, even after the engine's torque has passed peak, all the way to redline, than if you shift early. Argues for shifting at redline every time, and explains why a shorter gear ratio isn't always a good thing.
Making comparisons between the 3.15 and the 3.45 is easy, but drawing meaningful conclusions is more difficult. For example, you'd have to do more work to figure out who wins in a hypothetical run from 0mph to 100mph - this is where the 3.45 guy has more acceleration in a given gear, but also has to shift to the higher gear sooner, and in fact must shift to 4th to reach 100, where the stock car can remain in 3rd. If someone can help me with THAT math - I surely need it. (Math beyond basic algebra was NOT my strong suit in school!)
SO - comments, observations, corrections, supplements, etc - all welcome.
