I'm abroad so haven't got access to some proper tools, but I did a quick calculation:
Radius of the first corner 166.5m. Speed at apex 225km/h. This gives a lateral acceleration of 2.4g, interesting! As Cold Fussion said, the drag is immense but the downforce is quite significant, and they have the engine power to go fast anyway so they don't care that much.
If we assume car weight is 1150Kg it gives a lateral force of 27kN. Then its a matter of estimating the friction coefficient of the tyres to get the downforce needed to get around that corner at that speed. I've done calculations using few different coefficient numbers:
- 1: 27kN
- 1.25: 21.6kN
- 1.5: 18kN
- 2: 13.5kN
They have to use Advan A050 tyres in soft or medium, so the argument that they are not on slicks is not really true, since these tyres are really really soft and sticky!
I would say the friction coefficient is in the region of 1.5, so that's roughly about 20kN of downforce.
Now if we take a wetted area of 8.65m^2 (7.8m^2 for factory Evo) and a speed of 225km/h, with 20kN of force, it gives me a CL of 0.97!
Hard to calculate the drag from the data we have, but obviously it will be in the region of 0.5 probably, which gives a L/D ratio of around 2, which is good!
Again these are rough calculations done on my laptop while on holiday so pardon me if I am not 100% precise, feel free to comment and argue!