Functional Aero Parts and their effects ?

[CSG Mike]

I'd recommend you get spats for the side of that splitter, and you'll most certainly want a wing to balance it out.

[dradernh]

Originally Posted by glamcem

Do you have any experience with FRS/BRZ platform? Can you recommend any spoiler/wing upgrade that can go with a lip spoiler that I can combine with it?

Nope. I haven't purchased one yet, so I can't help you with specific pieces for a twin. The principles, of course, are the same when talking about production-based passenger cars.

If you'd like to understand those principles, I recommend Competition Car Aerodynamics by Simon McBeath. It is written in plain English, and it has more than enough in it to answer your initial questions, as well as the ones you'll have later. The information in it will enable you to make much more informed choices, which will save you money in the short and long runs. It's pretty easy to buy a bunch of pieces that don't meet your real needs.

Re: Flat Bottom & Diffuser - don't bother with the latter unless you've installed the former. Every professional I've dealt with has made that perfectly clear. Air that is tumbling along underneath the car is not going to attach itself to the face of the diffuser just because it's there. I'd put that pair of aero pieces at the bottom of any list you're making.

Re: "I am on the fence of adding an extension to the front lip like my friend did to his MX-5 since I believe it will improve the air flow for the brake ducting..." - air flow in that region of the front bumper cover isn't well understood. This CFD graphic is a useful illustration:


Re: "We know a local guy who can fabricate a custom abs lip like in the picture below" - know that MDO (medium density overlay - used for outdoor signs (think highway signs)) can be worked into any flat shape you want; it's easy to work with, not expensive, can be painted, and it's great for putting a radiused leading edge on the splitter; this graphic shows why you want that radiused edge if you're after maximal downforce from the splitter - i.e., it results in a 'hot spot' of strong low pressure and the passing air being attached to the underside of the splitter, thereby increasing downforce and reducing drag:

[plucas]

A radius is not required for a splitter. To do it right, it would be an airfoil shape and continue far back. However, this is not economical as it would probably cost $1000+ to make. A sharp leading edge isn't always a bad thing

Sharp edges can create vortices. Vortices can be used to create downforce as shown below.



That vortex above created a lot of downforce across the splitter.

[ZionsWrath]

What about Nur spec wing, I have to admit i kind of want it even though its kind of over the top

[CSG Mike]

Originally Posted by plucas

A radius is not required for a splitter. To do it right, it would be an airfoil shape and continue far back. However, this is not economical as it would probably cost $1000+ to make. A sharp leading edge isn't always a bad thing

Sharp edges can create vortices. Vortices can be used to create downforce as shown below.



That vortex above created a lot of downforce across the splitter.

At what cost?

[gramicci101]

APR makes a genuine splitter as opposed to a front lip. I'll leave it to @CSG Mike and @plucas to argue about the science of it.

http://ft86speedfactory.com/apr-fron...r-brz-432.html

[CSG Mike]

Funny, I was at APR this morning...

[gramicci101]

Originally Posted by CSG Mike

Funny, I was at APR this morning...

... Really? Ask them if they'd be open to making some of their stuff in FRP or urethane. I like their products, I just don't want to pay more for CF only to paint it to match my car.

[plucas]

Originally Posted by CSG Mike

At what cost?

APR's splitter is flat, not something with an airfoil shape. So I stand by my statement and that is why APR's splitter is economical.

I wouldn't think the FT86 owners could support a splitter that expensive.

[gramicci101]

Plucas, I'm also trying to understand the mysterious world of functional aero. In a hypothetical world where money rains from the sky, would it be better for a dd/weekend warrior to have a completely flat underbody similar to nascar, or one with Venturi tunnels similar to supercars and formula 1?

[plucas]

Originally Posted by gramicci101

Plucas, I'm also trying to understand the mysterious world of functional aero. In a hypothetical world where money rains from the sky, would it be better for a dd/weekend warrior to have a completely flat underbody similar to nascar, or one with Venturi tunnels similar to supercars and formula 1?

First, Nascar does not have a flat underbody.

To answer your question, neither. If you completely seal the bottom with a flat underbody or with tunnels, you will have to make huge unpgrades in cooling like to your transmission and rear differential. It also makes it a pain to work on. Now if it was mainly a weekend warrior with some street driving, that would be different.

The big issue with underbody aerodynamics is that it is very sensitive to ride height and pitch. This is not as big of an issue on a car that has stiffer suspension since ride height and pitch doesn't change to as big of a degree. Take a look below to see what I mean....


Shows how much ride height can change around a track (race car)


Ride height sensitivity (x-axis: Rear Ride Height, y-axis: front ride height, z-axis: coefficient of lift total)

Now between flat bottom or tunnels... Tunnels are far superior for making downforce. I can get more into it if you'd like but I will cut it off there. I think for most people, a good splitter and diffuser will do the most good. Also on the FT86, you do not need a perfectly smooth underbody to see the benefits of a diffuser (like Driveway Labs). The underbody of the FT86 is pretty decent. You won't get all the efficiency out of the diffuser since it will see some dirty air, but it is better than nothing.

[gramicci101]

Thank you; that was interesting. I assume the unit of measurement in the first graph is millimeters? It's curious that the rear moves so much (15-70) while the front only moves from 8-35, although I would attribute that more to suspension, if I had to guess. I can see what you're saying about the aero being sensitive to ride height and pitch though. With softer suspension, the car could rock back enough to get a lot more air than desired underneath it, causing potentially unwanted effects. I suppose that's where the tunnels could come in, as it would channel the air into a consolidated, faster stream and generate more downforce. I wonder how fast you have to be going for those to become effective though.

[CSG Mike]

Originally Posted by plucas

APR's splitter is flat, not something with an airfoil shape. So I stand by my statement and that is why APR's splitter is economical.

I wouldn't think the FT86 owners could support a splitter that expensive.

I meant more in terms of drag, not monetary >.<

[CSG Mike]

Originally Posted by gramicci101

... Really? Ask them if they'd be open to making some of their stuff in FRP or urethane. I like their products, I just don't want to pay more for CF only to paint it to match my car.

They stopped because they only do CF in-house, and the QC for FRP/Poly was a nightmare in the past.

Which piece were you looking for?