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      04-25-2012, 10:18 PM   #50
BrianMN
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Drives: 4 Door Family Sedan
Join Date: Sep 2009
Location: Minneapolis

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Quote:
Originally Posted by turb0mike View Post
I would also like to put in my $.02. I appreciate you doing all of this work and data collection but where is the wing? Other than the front splitter, the wing should probably be the next thin you look at in terms of creating downforce in the car. Also, need light weight 18"s and fat rubber, not 19s.

You also don't want to 'lower' the car too much because you then compromise the rear control arms too much so the travel distance and suspension geometry is off. Trust me, I added handling by raising my car 3/4 of an inch all around lol.
Thanks for the kind words. I have a couple explanations that will help paint the picture

For this discussion, all data I'll reference is at 100mph; zero wind, "track" setup.

Regarding the wing- A thorough analysis of a wing would show, for a 400hp (track power is only at 400hp) the benefits of a wing will not be worth the costs (i.e. drag) unless you're adding the wing as the last aero piece with a primary purpose to "tune" the aero system. First of all- let's put downforce in perspective. The best wing on the market, likely the Aeromotions airfoils, can only produce ~1500newtons (330lbs) of downforce on the most effective AoA at 100mph; whereas my full underbody aero system is showing ~640lbs of downforce over stock (~500lbs of absolute downforce) Plus, my underbody system is in no way perfected...if someone more experienced and knowledgeable than me were to build something like this it could likely reach 8-900lbs at 100mph. Most of the road course racecars achieve their high downforce numbers by underbody systems; not wings or canards. This downforce from the underbody is created with minimal drag; and the diffuser actually reduces much drag at the rear end of the car. Wings and canards can work wonders with tuning an aero system; and really belong on any car that is trying to be competitive in a road course racing series.

So the downsides of the wing- Whilst 300lbs of downforce at 100mph sounds great; that comes at the cost of drag; close to 225n at the most effective AoA. Most of the tracks I go to are very high speed; averaging speeds of 95 for one track, and 85mph for the others. Because of this and the engine only having 400hp, the drag would reduce top speeds by 5-8mph on the straights, and likely add a few seconds to my laptimes. In general, the additional drag is simply not worth the 300lbs of downforce.... especially on a car that only has 400hp, and for many people has heat issues. You can obviously adjust the AoA down to 0*, which will still produce around 220lbs of downforce; but that is still not a huge gain and still results in 125n of drag.

That said, a wing is a great addition to a car that is already setup with a functional aero system and the power to make the benefits come to fruition. If I could justify the $5-7k for an Aeromotions Dynamic wing, I would get that in a heartbeat

My splitter is producing ~150lbs of high pressure on the top of the splitter, and roughly 100lbs of downforce from the lower pressure underneath at static acceleration; but that is very dependent on ride height and position of the car (accelerating vs static vs. braking)

My track wheels are 18' forgestar F14s, and last year I made the switch from Hoosier R6s to Continental Slicks.

Regarding ride height- much of my data acquisition has revolved around ride height and rake. The sweet spot I've found is with the splitter at 4" above the ground, the front fender well 24" above the ground, rear fender well 24.5" above the ground. Any lower in the rear ends up "choking" the rear diffuser at its' entry point.
I can't say that I have noticed or can agree about the rear control arms having handling issues, as long as you have the solid/spherical end toe arms and every bushing/arm possible. I suppose it could become an issue with OEM toe arms and rubbber bushings. The AST suspension definitely helps as well. Hopefully I'll be upgrading to a set of JRZs in the future as well; so that'll make another quite substantial improvement.

Wow, what a long post, haha I definitely enjoy talking about this kind of stuff, as I/we can never stop learning new things regarding aero and suspension!

Cheers,
Brian

Last edited by BrianMN; 04-25-2012 at 10:24 PM.