FR Aero Test Project

[BarbecuePete]

Damn, I was going to write something really clever here, with lots of equations and all, then I crunched the numbers and it turned out that Forza's aero-weight is calculated when the car is reversing at 8mph (and that was using a simple relationship - it would have been worse if I'd started using geometric curves!)

Something tells me I've missed out an ultra-important variable somewhere

What variables are you currently using Spiny?

Im just thinking of the top of my head that if you set a cars springs to 100% SWR (So the cars body weight is taken out of the variables) and then ran the car without the Aero and watched on the telematery how much compression you get on the springs as speed increases then re ran with the full aero and noted the compression values again, this should (In my head anyway) give 2 sets of figures that if you put them on a graph would start at the same point and then get further apart as the speed increases, showing the increased compression on the springs as a result of the downforce being applied... it should then be possible to work out how much downforce is being applied as we know the spring strength and everything else has stayed the same...

Of course I could be completely wrong but just thought I'd throw it out there and see if it sparks anyone elses thoughts into a eureka moment... lol

[Spiny Anteater]

I'm afraid my calculation was much simpler (and the results suggest less accurate). I merely used the 'g' ratings for a single set-up, then assumed a simple linear relationship between speed and downforce (purely to get an idea for if I was on the right tracks). Then, I multiplied the g-rating by the weight of the car to get am idea of how much "weight" that g-reating represented. So, for say, a 2000lb car with a g-rating of 1.50, I would say that it could grip with up to 3000lbs pushing sideways. I then extrapolated back from the g@60 and g@120 figures to get the speed at which the difference between the "sideways force" and the weight of the car equalled the total value given for front and rear aero.

I knew this method was simple, and not perfect. Unfortunately, the result of -8mph suggests a severe flaw in that method, probably not least that it doesn't account for any aero downforce provided by the car's bodywork.

[BarbecuePete]

Im not sure if lateral grip is the best way to mesure the downforce, I think there are too many variables like tires and the cars own basic handling capabilities, you can apply the same amount of downforce to 2 different cars but you get different results for lateral G in the benchmark screen... I'll see if I can get some data tonight for the spring compressions in the telematery screen... it should be that as you go faster more downforce is applied and so the springs are compressed more, it should also give an idea to how the down force is being applied, Maximum rear downforce values are usually higher than maximum front downforce, so if it is being applied to the car in the same way the rear springs should compress more than the front springs... I'll be using 100% SWR springs with a 50 /50 bias to keep variations to a minimum...

[bimmerlovere39]

I can say for sure that the numbers we see in the tuning screen are the downforce made by the wings and not the net downforce.

For instance, my E30 M3 runs about 100lbs of downforce, and 100mph it is at the same ride height as it is at 0mph, which means that the car is aero neutral - all that downforce only cancels out the inherent lift.