Let's Talk Aero

[flyhalf]

Hello guys.
I'd like to copy and paste my post from another forum that I believe is very pertinent with this post


"Coming from a Challenger SP16 where aerodynamics wasn't the "big thing "to do,
I bought a GT 18 PP with supercharger.

I'm definitely ok with the power but the reason why I bought this car is cause I do track day (ONLY ROAD COURSE) often. THAT'S THE REASON WHY GOT MY MUSTANG! ( not the only one actually

)

So here is the question.
What are the best after market "aero gadget to install in a GT18 PP (NO MAGNARIDE) ?
I MEAN WITH REAL DOWNFORCE FUNCTION.

IMO the focus should be on:
1.better front splitter
2.air dams under for better air flow ( away from the front tires and canalize air on the diffuser
3.side skirts.
4. flat floor
5. diffuser
6. rear WING or SPOILER

I have 3 months to improve m Knowledge of this car and where to buy after market things.

PLEASE SHARE YOUR THOUGHTS and advice.

thanks
Fly

Ps. i'm italian ,sorry for my english

 

[stuntman]

#6 (wing, not spoiler) then #1 shortly thereafter.

 

[Olaaf]

Somehow I don't think you're guessing and welcome to TMO. How's the track scene in Singapore? Any opportunities to drive the F1 track in the Marina when they close it down for the race in September?

Did a bit more digging, and found this topic covered in a master's thesis by a guy named Bastian Nebenfuhr at the Chalmers university of technology (Sweden), fluid dynamics division. Here he worked with Volvo in both wind tunnel and CFD analysis on an XC90 on aero-acoustics regarding the side mirrors.





No track time in Singapore, closing down the city for F1 is a serious deal and they only let pro support teams (Carrera SuperCup, TCR, etc.) run. Though, i've been able to see two F1 races in my time here. Right over the border in Malaysia there are a bunch of tracks (no safety equipment? no problem!), and in Thailand there are about a dozen. Indonesia has a bunch, but mostly for bikes. I'm headed out to Chang circuit (Buriram) to rent a Porsche Cup car for a track day. I mostly head back to the US a few times a year to race my mustang.

 

[Olaaf]

Convertible? That Cd is a little high for a coupe.

I'm evaluating the coefficients on a larger area than that of the frontal area of the car. I do this as an apples to apples test when putting on different aero elements at different heights- like running a wing much higher than the roof line, or running dihedral endplates on wings for example, or switching out a mustang for a smaller or larger car. The actual number isn't the really important part in CFD, it's the deltas that matter. So, this number is high, and it's not the true number for the actual car, but for a simulation looking for delta's, it's perfectly fine for my purposes. When i get closer to my final aero workup, i'll tweak the frontal area to match reality and get more realistic numbers for the aero map.

But, this is a good point for consumers. The definitions of the tests are so very important. Look at APR's wing data for example, they measure free stream drag and DF- as if the wing is sitting on the racetrack not attached to a car. Or, check out superlight aero http://www.superlitecars.com/aero/ - look at the streamlines in the lower left picture- running over the wing and car and and then going DOWN? like, did they flip the wing upside down?

 

[stuntman]

If your Deltas are accurate then the % of the total drag is not correct. Without putting an actual car in the tunnel to cross reference, how do you know the Delta's are proportional or correct if the total is so far off?

You know what they say, junk data in = junk data out.

 

[Olaaf]

If your Deltas are accurate then the % of the total drag is not correct. Without putting an actual car in the tunnel to cross reference, how do you know the Delta's are proportional or correct if the total is so far off?

You know what they say, junk data in = junk data out.

The geometry will stay the same, but the Reynolds number will drop when the evaluated area drops, and the delta will be proportional. This is exactly how you can evaluate a 60% scale model in the wind tunnel and know that the forces will be proportionate on the full scale model.

For wind tunnels... Pipe dream for an amateur racer like me. In openFoam i'm modeling a moving floor and rotating wheels, and can add cross air flow for yaw analysis, and even place another car right behind my main car model to check for the drafting effect on drag and lift.. That right there is a $10,000 an hour wind tunnel, not the $600 hour one. So there are things you can do in CFD that are not possible in the tunnel.. F1 teams have 30 units of testing per month, and each unit is either a teraflop of CFD or 1 day in the tunnel.. Guess which way they spend most of their units?

 

[VoodooBoss]

@Olaaf post a photo of your Mustang race car (or any other race cars you may own) when you get a chance.

https://trackmustangsonline.com/threads/member-introductions-introduce-yourself.3503/

 

[flyhalf]

Let's go back to aero.
Do you guys have data on this?

https://www.steeda.com/steeda-s550-functional-race-wing-2015-all-476-steeda-wing-15

Sent from my LG-H872 using Tapatalk

 

[Olaaf]

Let's go back to aero.
Do you guys have data on this?

https://www.steeda.com/steeda-s550-functional-race-wing-2015-all-476-steeda-wing-15

Sent from my LG-H872 using Tapatalk

That "wing" is just for looks. Watch this video, start at 1:50 if you are pressed for time:

 

[stuntman]

That "wing" is just for looks. Watch this video, start at 1:50 if you are pressed for time

But it says functional in the name!!

In all seriousness, the older straight Steeda wing (well, the whole span has a slight arc to it that followed the trunkline) was quite effective and made well over 100lbs of downforce. Does it make as much downforce as a better profile in cleaner air up high? No, but it was still a very functional piece that wasn't too visually aggressive.

This S550 version has a similar cord profile, but with a somewhat twisted "3D" shape to it with the outer edges having a little more Angle Of Attack. I would imagine the downforce wouldn't be too far off their original design.

 

[flyhalf]

But it says functional in the name!!

In all seriousness, the older straight Steeda wing (well, the whole span has a slight arc to it that followed the trunkline) was quite effective and made well over 100lbs of downforce. Does it make as much downforce as a better profile in cleaner air up high? No, but it was still a very functional piece that wasn't too visually aggressive.

This S550 version has a similar cord profile, but with a somewhat twisted "3D" shape to it with the outer edges having a little more Angle Of Attack. I would imagine the downforce wouldn't be too far off their original design.

I like Kyle. I have watched all his videos.
I knew this one and Thanks for sharing it here.
So key word is compromise. Not too high(will increase drag and unbalance the front) not too low(will interference with the trunk and undo the downforce)

Steeda has a twisted race wing which is also a little "out"behind the back.
So it creates in theory low pressure area behind the trunk and in theory increases also the pull of the diffuser.
Once again" in theory" . That is the reason why I was hoping to find some "numbers"


Sent from my LG-H872 using Tapatalk

 

[VoodooBoss]

But it says functional in the name!!

In all seriousness, the older straight Steeda wing (well, the whole span has a slight arc to it that followed the trunkline) was quite effective and made well over 100lbs of downforce. Does it make as much downforce as a better profile in cleaner air up high? No, but it was still a very functional piece that wasn't too visually aggressive.

Years ago a few TMO members and I got a tour of a Grand Am Boss 302R from a Ford engineer and he told us something very similar. The 2012/2013 LS wing (like the one on my Boss 302 in my signature) also has similar downforce. The engineer told us that the pro drivers liked the Steeda wing better because the end plates provided a bit more stability during high speed braking.

 

[stuntman]

The LS wing is less than half the downforce of the original Steeda.

 

[VoodooBoss]

I'm sticking with what the Ford Racing engineer told me.

 

[stuntman]

Cool. I'll stick with the guy who was actually in the tunnel and tested both

The G-stream on the 302S makes a lot more.

And a wing up high can make similar downforce with less drag when trimmed out (more efficient) than a lower mounted wing with worse airflow and more AOA.

 

[flyhalf]

So then we come to the next question.
What's the best wing?
Now inknownit depends from track to track but let's say this" if you would buy one what wpuld you buy?

Sent from my LG-H872 using Tapatalk

 

[Olaaf]

100lbs at what speed?

Pretty sure this is the Steeda "wing":

https://www.alibaba.com/product-detail/Automobile-Universal-RC-Carbon-Fiber-Race_60591720352.html

Full disclosure, i owned part of RHR Performance for awhile, but i wouldn't buy aero parts from anyone unless there is data like this:

https://rhrperf.com/fulcrum-wing-1/

The real question is not what is the best wing, but what are your downforce goals? What are your class rules? If you are not in a race class yet, what race class will you likely be running in a few years? Work backwards from there.

 

[Olaaf]

The engineer told us that the pro drivers liked the Steeda wing better because the end plates provided a bit more stability during high speed braking.

That is likely "butt dyno" speak to explain what they felt, if they indeed did double blind testing. Endplates have impact on the wing aspect ratio by AR = ARactual (1 + 1.9 h/b), where "h" is the height of the endplate and b" is the span of the wing with a corresponding increase of drag due to viscosity induced drag which increases at the square of speed in turbulent flows:

ref:
https://en.wikipedia.org/wiki/Wingtip_device
https://en.wikipedia.org/wiki/Skin_friction_drag

 

[flyhalf]

Good points. So far only hpde.
I always divided in 2 the conversation:
1. Better suspension= better slow turns.
2. Better aero= better stability in medium high speed turns.
Don't looking for max speed on the straight. (For that I'll use hp..

With that wing rhr did a great job improving stability at all speed. (80 miles they declared up to 200lns at only 60mph!) However 2200$ is out of budget.






Sent from my LG-H872 using Tapatalk

 

[Olaaf]

Good points. So far only hpde.
I always divided in 2 the conversation:
1. Better suspension= better slow turns.
2. Better aero= better stability in medium high speed turns.
Don't looking for max speed on the straight. (For that I'll use hp..

With that wing rhr did a great job improving stability at all speed. (80 miles they declared up to 200lns at only 60mph!) However 2200$ is out of budget.

Sent from my LG-H872 using Tapatalk

Here is my advice given from my experience as a car builder, racer, then an engineer for a Global MX-5 Cup team (we won the championship- http://www.flyingratms.com/ and then the part owner of an aerodynamics manufacturer:

Don't touch your car. Hire a pro coach, not those HPDE "coaches" that hop in your car right before your session to make sure you don't crash. Until you can get on a skid pad in a 90hp miata and hold a drift for 2 complete revolutions it's not time to touch your car. I can lap Porsche GT-3 cup cars in my 2006 Mustang GT with only 280 hp @ 3500lbs. I spent 10k for 1 year of professional coaching and it was worth every penny. PM me if you want recommendations.

But....no one follows that advice. Therefore, the next best thing you can do is install a data logger in your car if you are the self learning type and spend money that will make your car more reliable (brakes, brake fluid, etc.) You actually want to be on shitty tires that will slow down your lap times but will teach you car control (and make your components last longer by giving them less load).