Functional Aero Parts and their effects ?

[gramicci101]

Originally Posted by CSG Mike

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

Maybe it's a short track with a lot of corners?

Originally Posted by CSG Mike

Which piece were you looking for?

I would love a full lip kit with rear side skirts, but I'm just not going to pay that much for show instead of go. There are polyurethane lip kits that look pretty nice without breaking the bank, so that seems like a better route.

[dradernh]

Originally Posted by plucas

A radius is not required for a splitter.

That's why you don't generally see radiuses on the splitters sold to amateurs/hobbyists.

Originally Posted by plucas

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.

I like your thinking, and when I was still considering every imaginable possibility, I took a hard look at that wild idea for a moment, but a number of show-stopping impracticalities scotched it immediately (e.g., drag, really low bang for the much-higher-than-$1K buck, raised ride height yielding even more drag). PITA-wise, I was not unhappy to skip that exercise.

If I couldn't get enough front aero on a car, I'd just hang a $150 sprint car front wing off the front of it. At least until NASA banned it anyway.

Originally Posted by plucas

A sharp leading edge isn't always a bad thing.

Absolutely - it's still a splitter. While it yields less downforce, which is the purpose of the exercise, it does take up less space, so that's something at least. Plus, most off-the-shelf units come that way.

Originally Posted by plucas

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.

I'm confused. Are you suggesting that a thin splitter with no meaningful radius on its leading edge is the means to maximizing splitter-generated downforce? That is, slowing down the air passing across the bottom of the splitter by allowing it to separate from the splitter surface, or not attach in the first place, will lead to the splitter producing more downforce?

[glamcem]

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.

Looking at the APR piece and the custom made ABS plastic splitter, I cannot see a big difference so I think I can just use the custom made splitter



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


Do you think using this type of splitter ( for feeding more air to the brake ducts from fog lights) is a bad idea? FWIW, my car will be dropped about 1.25-1.5" when I receive my coilovers

[gramicci101]

Originally Posted by glamcem

Do you think using this type of splitter ( for feeding more air to the brake ducts from fog lights) is a bad idea?

That's not what splitters are for. Splitters are there to cleanly split the airflow and create a low pressure zone under the front of the car, increasing downforce.

For brake cooling, the positive pressure on the duct inlet that you get from driving forward will force cool air through the duct and through the brake rotor.

APR tech article on air dams and air splitters

[glamcem]

Originally Posted by gramicci101

That's not what splitters are for. Splitters are there to cleanly split the airflow and create a low pressure zone under the front of the car, increasing downforce.

For brake cooling, the positive pressure on the duct inlet that you get from driving forward will force cool air through the duct and through the brake rotor.

APR tech article on air dams and air splitters

Thanks for the link.

This is an excerpt from the link you provided

The splitter (or air dam) itself does not actually create downforce. What the splitter does is that it increases the area over which high pressure can build up. The more high pressure there is above the splitter, the greater the net downforce there is. Additionally, if there are openings in the front bumper (above the splitter or lip) for brake ducts or radiator cooling, this increased air pressure will encourage more air to flow into these openings.

[gramicci101]

Correct, but that's a side effect of creating lower pressure under the car.

[glamcem]

back to topic, I think I should've stated what I am trying to accomplish a bit more clearly.. my apologies..

I am just trying to use a functional splitter that I can benefit from added air through the radiator and brake duct openings ( fog lights will be removed) and add some high speed stability.. In the meantime I don't want to hurt the high speed stability/ corner stability negatively..

As I read, BRZ Limited spoiler is still functional and reduces the drag coefficient. by 0.01 (marginal maybe but still functional)

[gramicci101]

I think CSG Mike hit on it earlier then. I'd get the APR air dam and splitter, and the Driveway Labs type 1 rear diffuser. It's one of the few that is a genuine rear diffuser instead of a bumper garnish. It's also available at FT86 Speed Factory.

Beyond that, maybe canards or something similar. That's for more knowledgeable people than me to discuss, though.

[plucas]

Originally Posted by CSG Mike

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

Ahhhhh splitters USUALLY decrease drag a little or are drag neutral when applied to a street car. This all depends on the design of course and how much downforce you want to create with it.

Originally Posted by dradernh

I'm confused. Are you suggesting that a thin splitter with no meaningful radius on its leading edge is the means to maximizing splitter-generated downforce? That is, slowing down the air passing across the bottom of the splitter by allowing it to separate from the splitter surface, or not attach in the first place, will lead to the splitter producing more downforce?

That is not what I am suggesting at all. A radius leading edge is good and provides benefits. You do not want to slow down the air under the splitter as that will create higher pressure. However, some separation can be a good thing in the term of creating vorticies. Vortices can be very powerful at creating downforce. The problem is controlling vorticies and getting them to go where you want them. I guess what I am getting at is the saying "there is more than one way to skin a cat". The problem I notice when online is a statement is made about some device aerodynamically and it is taken as the gospel in every situation.

If you want to really understand automotive aerodynamics when it comes to performance, I would look into vorticies. This is why F1 cars look so complicated and minor damage to the front wing is so detrimental to the performance of the cars.

[CSG Mike]

I generally dislike diffusers for the average user.

They're VERY easy to damage/destroy.

[CSG Mike]

[ame="https://www.youtube.com/watch?v=fMwK136xeHY"]Greddy Turbo BRZ and SoS Supercharged S2k at Buttonwillow 13CW - YouTube[/ame]

Fast forward to about 2:50

[leicaboss]

Originally Posted by dradernh

That's a big subject! I can tell you that I devoted considerable time and expense to aero study, fee-based consultation, parts fabrication, and on-track testing. I'll summarize by saying it was well worth it because the result let me go through corners faster, and with much more confidence. PM me if you're interested in further specifics.

You're correct that you've got to balance the front/rear downforce. That's part of tuning the car's overall setup to meet the needs of the driver, so one size will not fit all. Some want a loose car, and some a neutral car; few want a tight car - they're just slow.

The photo below shows our results, and includes the following aero mods:

1) Well-vented hood, with one large pair located just behind & above the coolant radiator;
2) Shrouding so all air entering the front of the car is forced through the radiators;
3) Front & rear tire deflectors (v. hard to see in the photo);
4) Canards/dive planes;
5) Splitter supported by four turnbuckles, and adjustable from 3"-9.5";
6) Motorsports wing adjustable from -2° to +10°;
7) Wing uprights made for this car and wing; and,
8) Supporting structure for the wing uprights in the trunk that is welded to the frame rails - the uprights are bolted to the structure and can be moved a few inches longitudinally to adjust wing placement over the rear of the trunk lid.

Note that splitters and wings must be mounted rigidly enough that you can stand multiple people on the splitter, and so that you can use the wing to push the car, both with no deflection whatsoever. You will have a very slight side-to-side deflection of the wing.

Awesome reply! Just curious, what are some good ways to make sure a mounted splitter (well, in turn the bumper) can be secure? I realize the splitter provides downforce, but how can I make sure the bumper doesn't just decide to pop out from its clips (under the headlights)?

[dradernh]

Originally Posted by leicaboss

Awesome reply! Just curious, what are some good ways to make sure a mounted splitter (well, in turn the bumper) can be secure? I realize the splitter provides downforce, but how can I make sure the bumper doesn't just decide to pop out from its clips (under the headlights)?

Thanks!

Because I have yet to acquire my twin, I don't really know how owners are going to be supporting these assemblies. I'm certain, however, that an assembly with a splitter of any length is going to need to be firmly affixed to the bumper beam (or its equivalent) as well as to another strong set of mounting points on the underside of the car.

I can describe what was done on the M3:

1) The trailing edge of the splitter was well-supported (see the first photo below);
2) The bumper cover's OEM attachment points were retained, and are:
2a) Two tabs on the inside of the cover at the top trailing corners that were tied to the leading edges of the wheel wells with small sheet metal screws;
2b) Four bolts with 1" washers attached at the points in the photo in my first post where the turnbuckles are anchored through the cover and to the bumper beam; and,
3) Four screws ran from the bottom of the splitter and through the bottom of the bumper cover (these are the screws on the left in the first photo below) - IIRC, they screwed into something that held them fast that had been added to the inside of the bottom of the cover (I don't do my own work, so I'm a bit fuzzy on that part of the assembly).

This was for the first splitter we put on, and that's the one in the first photo below. It's 1/8" or 3/16" aluminum plate. The adjustable splitter came later, was added below the first splitter (a temporary arrangement during testing), and the turnbuckles were used to support it from above. The original aluminum splitter had no simlar support from above - it should have had, but it didn't.

The entire bumper cover/splitter assembly was removable in just a few minutes as the only screwed/bolted connections to the car were the screws and bolts listed in #2 above. Note that this implies that the brake ducts were not affixed to the bumper cover, which was the case; they were mounted in place in a fashion that allowed them to do their jobs without requiring any disassembly before removing the bumper cover/splitter assembly. This mounting arrangement can be seen in the second photo below.

You can see here that the trailing edge of the splitter is supported by a pair of massive tabs held in place by stand-offs bolted to the swaybar mounts. That was another temporary arrangement. Of course, almost everyone here is going to be buying off-the-shelf units that will have undercar support solutions baked into them, so this kind of one-off fabrication won't be necessary.

Brake Duct Mounting sans Attachment to the Bumper Cover

[gramicci101]

Originally Posted by CSG Mike

I generally dislike diffusers for the average user.

They're VERY easy to damage/destroy.

Originally Posted by CSG Mike

Fast forward to about 2:50

I think that was his rear bumper, not a diffuser. I can see what you're saying though, it hangs down a lot further than the OEM departure angle was designed for, and on a street that could have adverse effects. I had been considering a Driveway Labs type 2, because it follows the car's lines more closely, but then I decided that I just don't play those kinds of games and it would only be an aesthetic mod for me.

I love watching your videos. Yours and @ATL BRZ's are always fun. There's some nice sideways S2K action at 2:14, too.