And if so, how much?
I know they would in real life, but do they in Forza? If I had a Skyline for example, I would’ve thought the order of downforce would be No Aero (remove wing) < Stock Wing < Aftermarket Wing < Forza Wing. Would a Porsche with a stock wing have more downforce than a Ferrari 360 with no wing for example? If anyone knows or has any ideas on how to accurately test this, that would be great.
Stock aero provides usually 10llbs front and 25-50lbs rear downforce depending if you have rear spoiler or only rear bumper.
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Nice! Thanks, how did find this out?
Reverse engineered 
Adding aero and thus downforce need to be compensated with increased spring rates, the relation is linear. Thus from the amount of increased spring rates you can deduct amount of added downforce. Now for stock aero there are cases where you can remove stock front and rear aero kits, from the difference in required spring rate you can deduct stock aero downforce levels.
I actually reverse engineered today and I got 10lbs(at rear) from rear wing removed and 20 (at rear) from stock rear wing on the same one car. Another car had about 100 lbs from stock wing + diffuser.
100lbs rear stock aero does not make much sense as it should be lower than race aero which starts usually at 75 rear.
To verify you ay check calculated top speeds for stock and race aero kit.
its the diffuser what does id say 80lbs. 20 for stock wing. The diffuser is no or very little drag.
Stock rear diffuser provides 25lbs downforce definitely. Something must be off with your calculations.
Like a massive stock diffuser on a race car or expensive sports car.
Stock aerodynamics are dramatically different for each car. Some even have a little lift at high speed.
Nothing I have seen in the last few Forza games leads me to believe that a general “rule of thumb” or downforce number can be applied across the board. Cars and the effect of their parts are just too different.
FWIW,
I also set up real cars and just because someone adds a splitter, diffuser, wing, spoiler, wickerbill, etc, that doesn’t mean your net will get you actual downforce. Too many other variables to make a blanket statement.
Scott
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All non-adjustable stock and street aerokits provide 10lbs front, 25lbs rear wing (if existing) and 25lbs rear bumper downforce no matter how big they are rendered in-game.
Non-adjustable sport aerokits provide 40lbs front and 70lbs rear wing and 50lbs rear bumper downforce again no matter how big they are rendered in-game.
This is due to the fact that non-adjustable aerokits should provide less downforce than the race aerokit which usually starts at 50 front and 75 rear wing.
You can simply verify this by comparing calculated top speeds for different aerokits.
Thanks but I also mean diffusers and wings that is apart of the car and cannot be removed or adjusted.
If they cannot be removed or adjusted how can you possibly determine the downforce they provide?
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Maths.
I test a cars aero with a rear wing and work out its aero % difference and then remove the rear wing and test the balance with the front wing.
front wing rear wing
227 d+ 206
129 d
This says that the diffuser downforce is about 225 lbs.
But I forgot the stock rear wing is 20 lbs.
front wing rear wing
227 d+ 206
129 d+stock rear wing
front dif rear wing total balance
227 225 206 431 1.8986784141
129 225 20 245 1.8992248062
so the diffuser of the Audi R8 '16 generates 225 lbs of downforce.
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Some good dialog going on here about the impact of the diffuser… anyway, @ uber, as I look at your numbers (and trying not to get to “anal” with this), if all i correct, then I would agree with you that the DF produced by the diffuser (excluding the stock rear wing weight) would be 271. Basically, if you look at the 2 points {[for a line, y=mx+b] (x1:x2, y1:y2), where x1=129, x2=227, and, y1=0, y2=206}, this would yield a slope(m) of ~2 with an intercept(b) of ~271 (which is the DF). This aligns with your assessment!
When you simply add the 20 lbs of the diffuser, the points are x1=129, x2=227, and, y1=20, y2=206…the slope(m) is now 1.9 with an intercept(b) of 225 (which also aligns with your finding), now are you not looking for balance? If so, then, for FDF = RDF, and if car is already balanced prior to adding any wing (front or rear) this would mean that the diffuser would weigh about 250 lbs. (250 calculated by using the line equation, having FDF=RDF, so, 1.9-1.0=0.9, then, 225/0.9=250). Or, is the initial car (without the front and rear wings NOT balanced? Thanks!
Sorry for all the math, yet, was trying to understand what you guys were trying to achieve.
PRKid
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I ment 225, I edited it.
Got it! Thx!
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