Originally posted by undersquare
Actually I think it has to be equivalent, otherwise the car would be too different surely? If the rear downforce were very different the aero balance would be different, that would affect the transition from mechanical balance to aero and everything, the test car simply woudn't represent the race car.
The car has run so far with a very simple single-deck diffuser + 08 wing, they have to be replaced by a double-decker diffuser + 09 wing, and they have to provide the same downforce, that is the only thing that malkes sense.
Meawhile I'm wondering what happens to all the air going into the sidepods through those huge apertures. Mac seem to have gone from needing the least cooling to needing the most. I know there's kers but still. Unless they don't do cooling with all of it, a straight-through tube in that bulky shape and it still has its energy when it exits into the diffuser...
The point I'm trying to make is that McLaren aren't running the 2008 wing because there is something wrong with the 2009 one... I'm running out of ways to express it...
It was in response to this (the bold part) :
Originally posted by wingwalker
Earlier in this thread some folks were claiming/guessing that Mclaren uses 2008 wing cause their final 2009 wing+diff will be as good as the 2008 one, with the reason for not using in in the test being their will to hide it from other teams. So it is a bit magical/mythological in content of this tread. It always sounded like total BS to me, anyway.
thats simply faulty reasoning... compare it to what killfile said, which sounds quite reasonable to me:
Originally posted by killfile
No, it's a reasonable point.
Ultimately, the wing+diffuser combo gives a certain amount of downforce in exchange for a certain amount of drag, so you can produce very similar Cd profiles with quite different aerodynamic setups. They aren't going to be spot on, and you wouldn't want to bet the world on them, but it's generally close enough for testing purposes - in this case, making sure you have enough rear grip to stress-test the KERS and develop profiles for loading and unloading it. It's possibly not something we're seeing from other teams as they either aren't planning radical changes for Melbourne, aren't going to be running KERS there, or aren't at stage with their KERS testing yet.
It is a bit of a gamble for Mclaren through, as the new diffuser arrangement will have different characteristics under braking and acceleration, being inherently more sensitive to pitch.
As to why they'd switch back to the 09-style wings, again, they have to see if they're behaving as per the simulations, both aerodynamically and physically. There was a photo of one of the 09 wings with a set of little gold foil squares on it's supports - these are strain gauges to see how much the supports are deflecting.
That doesn't mean that what McLaren is doing must match the 2008 levels in any way, but it means they have to understand what the 2008 wing does quite well..