[BrianMN]

Originally Posted by zsapphire7

what material did you use to make the underbody and splitter?

The first version of the underbody and diffuser is made of 1/8" ABS Sheet plastic, which can be maluable but still hold its' shape well. The front splitter is made of 3/8" High Density PolyEthylene, which is quite strong and rigid

[nafoo]

Any photos further away from the car? I want to do this just because I think it looks cool... jk ...

[spacemonkey1112]

BECAUSE RACE CAR!!! jk. but seriously. just reading through this thread, i've grown a much deeper understand about aerodynamics. Thanks a lot and I can't wait to read up on whats to come!

[turb0mik3]

This information is PURE SEXXXX!!!! You beat me too it because ER is doing this EXACT same thing once I get my car back fro the dealership. SO SICK!!!

[turb0mik3]

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.

[BrianMN]

Originally Posted by turb0mike

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

[kenneth]

What you say about the wings make sense! I have been wondering whether the diffusers you have fabricated would be accepted at road course events such as the BMWCCA or PCA HPDEs ?

[BrianMN]

Originally Posted by kenneth

What you say about the wings make sense! I have been wondering whether the diffusers you have fabricated would be accepted at road course events such as the BMWCCA or PCA HPDEs ?

Yep, so they are definitely 'accepted' at any and all PCA/ACNA/BMWCCA events, and all of the NASA events as well.

The only series I know of that bans diffusers is the Continental Grand-Am/Rolex Sports Car series.

[kenneth]

Originally Posted by BrianMN

Yep, so they are definitely 'accepted' at any and all PCA/ACNA/BMWCCA events, and all of the NASA events as well.

The only series I know of that bans diffusers is the Continental Grand-Am/Rolex Sports Car series.

That is very good news. How far are you from commercializing this product?

[turugara]

Originally Posted by kenneth

That is very good news. How far are you from commercializing this product?

+1
Kickstarter or partner with a vendor?

[turb0mik3]

Good explanation regarding the downforce and drag, but I am talking about downforce in different directions as well. I am trying to wrap my brain around how you produce "downforce" from an undercarriage during extreme braking or highly banked (or not-banked curves). I sort of understand the pressure points as you stated, but might need some clarification. I would assume most of the undercarriage stuff is to reduce the drag, but I don't know how making the bottom of the car super slick and the back creates downforce, that just seems not logical. I do know that the rear diffuser literally "pulls" air out from under the car, but I think that would be a rather large drag reducer. Yes, the front splitter is making downforce but the underside of the car doesn't seem to produce a lot downforce and the rear diffuser (which is nice and I will have one soon) seems like it wouldn't at all either, only help with drag. Perhaps there is a correlation to when you reduce drag it converts into some form of downforce?

I have another question for you as well. You may be able to computer simulate the drag effects and what not of your underbody carriage and rear diffuser, but most of the wings and their drag is almost minuscule to the effect of cornering and braking capabilities. I shaved 5 seconds off a lap time with JUST adding the wing (I had a front splitter before that). I would increase my speed around certain corners by almost 6-7mph. I lost 5mph down a straight at 145mph and yes that does cost time, but two things 1) What % of most tracks are straight vs. turns 2) the amount of time you gain in braking is 5x more important than the 1 second you add from loosing 5-10mph (if that). Also, as you probably know, you can change the angle of attack on almost every wing. My APR wing is almost always at neutral position, so the amount of drag is not that much. I have been experimenting and even find to have a slightly greater angle of attack is beneficial to not having any wing at all. Most of the cars in the BMW CCA/NASA and what not have wings because of this importance.

I think you have done a great service to us with the testing and I am going to be doing the exact same thing to my car in the upcoming month. I just think you should go to the track and post a time with the current setup and THINK about getting a wing and seeing the difference.

Once again great discussion, but I just think the amount of drag you are talking about is so minuscule compared to the effect around corners and braking.


^^^ I think that is the perfect setup IMO.

Just reread, I paid 1400 for my APR 67"er. :-)

[BrianMN]

I'll respond in a but more detail later, but basically I'd suggest spending a few hours (or many many many hours) reading up on aero. Also spending time with some local aerodynamicists will help for some q & a. Some of this stuff doesn't seem logical until you get a full understanding of what is actually happening. to sum it up- making the underbody smooth and flat accelerates air. Accelerated air = lower pressure, lower pressure literally sucks the car down to the ground. please note- this ONLY works when you have a full and complete underbody system. Just slapping on a diffuser will yield 180lbs of downforce and only ~20lbs of drag (yes this is what i spend a full night testing)

Again- check out the stats of your APR wing. Unless it's a dynamic wing (meaning itll flip up to the highest aoa for braking) it's effects aren't going to be ultra impressive. It will certainly help, and definitely give a very noticeable improvement in "stability" throughout the entire track... And whilst it will improve confidence and consequently laptimes, it is not due to substantial downforce...especially if you're running it at 0*

Check out some of the f1 technical forums, corner carvers, and some of the long journals available in PDF form... That'll help get going. Please don't think I'm just a nay sayer for wings... I have a decent level of experience with an EvoX going from stock wing to a static to a dynamic Aeromotions wing, and it was certainly a nice bump in confidence and a huge improvement in braking (only the dynamic) but nothing compared to actually sucking the car to the ground from underneath. While the ER 135 might look cool, I can spot quite a few things that are flawed. To be fair, they probably weren't going for a complete aero system, rather just the "basics". The wing alone is not nearly as effective as it could be given the placement. If you truly want your wing to WORK, check out the DTM cars and alms cars and see how they have the wing off the rear of the car. When I do a wing, I'll be doing it the most effective and worthwhile way.

Mike- when you get a chance, can you do me a favor and snap some pictures of how you have your main hoop attached to the floor? I'll be doing a similar roll bar soon and am curious to see how you've attached yours.

Cheers,
Brian

[FrankiE90]

brian how has she been hold'n up on track days?

[Rotary Rocket]

BrianMN,

Very nice job on the areo package, keep up the good work.

Where can I purchase the front lip you added before fabricating your splitter?

TIA.

[BrianMN]

Hey Guys,

I've been collecting a ton of data from the track events the past few weekends [too much, in fact] but I simply have been too busy to organize and do an updated writeup.

A rather humorous update from the first track event: The cables that I had holding up the splitter failed on the first session with speeds above 150 All of the logging and testing I had done was only up to 100-110mph, and the cables had been plenty strong for that... Once the higher speeds came, along with exponentially higher downforce, the cables simply could not hold. A pretty good problem to have!

Overall, I was able to comfortably increase speeds through high-speed corners by 3-5mph...all with significantly more confidence.

MUCH more to come!


BIR May 7th by MDM Enterprises, on Flickr


BIR May 7th by MDM Enterprises, on Flickr

Along with some fresh rubber

BIR May 7th 3 by MDM Enterprises, on Flickr

[TSM330i]

Subscribed!

Can't wait to see all the data from the track.

Selling the rear diffuser any time soon?

[BrianMN]

Originally Posted by TSM330i

Subscribed!

Can't wait to see all the data from the track.

Selling the rear diffuser any time soon?

Thanks!

In a nutshell, the track data has "validated" what I had calculated the downforce would be at 140mph, which turned out to be roughly a delta of 765. The only gap in my testing is that I was only able to do 15 data points, compared to the normal 35-40. Also, at the first day it was quite windy with scattered showers and I noticed a bit too much turbulence to be confident in the readings.

[FrankiE90]

so above 150 those side cables u had snap'd off.
are u gonna put the heavier rods in place of the outter cables or
just keep em off?


any video footage, by chance?
Bimmer looks track clean!
job well done.

[BrianMN]

Originally Posted by FrankiE90

so above 150 those side cables u had snap'd off.
are u gonna put the heavier rods in place of the outter cables or
just keep em off?


any video footage, by chance?
Bimmer looks track clean!
job well done.

Nope, originally all 4 of the supports were cables...then when they broke I had the two heim-joint supports that I put in the center to hold more of the weight. One I did that and replaced the cables, the side cables stretched out the first session, but then held strong the rest of the days/events.

[prelude2perfect]

Garbage.... All of it.... Pure Garbage.


Damn Ricer

[nafoo]

Originally Posted by prelude2perfect

Garbage.... All of it.... Pure Garbage.


Damn Ricer

Not sure if serious ;D

[GOTMH8N]

Damn good stuff here!