Quote:
Originally Posted by CanAutM3
The acceleration times from 0-40km/h and 0-60km/h in post #164 also seem over-optimistic for the F8X. It would mean average acceleration of 1.5g and 1.25g respectively. I am not sure street tires would support this on a RWD car.
Could this be explained by some sort of roll-out? |
Rollout has nothing to do with graph based outputs from CarTest, again rollout is just "bookkeeping" used for tabular data. Rollout simply starts all timers when the car has traveled 1'. I agree that the acceleration numbers are large and impressive and only possible through both weight transfer and good tires. I have not modified the tire parameters compared to any of the other sims I've presented.
Comparing the times to speed from CarTest for the F10 M5 vs. Fastestlaps (last table) does indicate some pretty substantial overprediction of the very initial (1st gear) acceleration by CarTest (0-40 km/hr results). Here I have disabled the 1 foot rollout, using 0 feet (more in keeping with the way anyone reporting km/hr figures would most likely be testing).
The second set of results in US customary units turns the 1' rollout back on and shows a much better correspondence with most test results. Perfect nope, a bit slow on the 1/4 trap, a bit quick on the time. Of course bear in mind this is just one data set, and it is typical for CarTest to more calculate a best possible sort of time. Also note I have used 580 hp and 520 ft lb torque, substantially underrated and loosely consistent with dyno and actual test results (esp for a car this heavy).
Some quick changes with the tire parameters in CarTest did not effectively lower the peak acceleration in first gear (puzzling - it is as if the simulation is using a fixed friction coefficient during the case of spinning tires which is also inaccessible to the user). I'm open to suggestions for improvements. Heck buy the tool yourself, it is inexpensive and the author offers basic email tech support. Good support for the basics but unwilling or unable to dive as deep as you and I have in some discussions (like losses).
Simulation certainly ain't perfect but it does always beg the (hopefully) obvious question as to what THE test based time is for any metric. There is no one "correct" single time.