Anyone have Aero questions?

First post, but this seemed the best place to ask.

Ive got a ZZW30 MR2 which is "done" so I'm planning the next headache to keep me busy. And that's making it more aerodynamic. I recently got my hands on a decent looking carbon fiber wing, but no uprights (is that the right term?) 

How can I determine the best height of these uprights? Here it's sitting on the engine lid about where the bottom of the uprights would be. My guestimates are around 8-10" above the lid.

I also plan to mount the uprights to that center support bar between the shock towers, though it won't put the wing all the way at the back of the car.

Is my thinking right or wrong that it's better being mounted to the chassis directly versus having it as far back as possible?

The other phase is the bottom of the car, as I plan to smooth it out as much as possible and try to adapt a Lotus Elise rear diffuser. The front bumper area actually looks fairly well designed but under the cabin looks like it needs some help. I have a huge section of plywood I was going to try and flatten the center section to prep the rear for the diffuser.

Is this area "flat" enough or does the belly pan brace ruin it? 
Notice how it's a pocket, sort of?

Do I Extend skirts on those edges, or just flatten that whole area?

I've essentially built a budget Elise so I plan to keep stealing their parts and ideas lol

Bonus pics of the car itself:

Thanks

Simon

If the engine cover/trunk lid is strong in the area where the bumpers are (won't flex much) you could move the supports back to that area and attach to the lid directly instead of the structure between the shock towers? Then you could open/close more easily.

8" seems like it might be kinda low causing the wing and rear spoiler to work against one another. Do you know others with a similar car with wing set ups? Any CFD studies done on similar cars?

If you use your plywood mounted flat up to the bottom of the frame rails would the braces interfere? Hard to tell in pic. Is the plywood wide enough to stick out on the sides by the rockers?

If you are able to mount plywood to bottom of the rails would you be able to transition to the Elise diffuser cleanly?

Will the plywood/diffuser restrict engine cooling? I've seen that the Lotus use NACA ducts in the flat area ahead of the diffuser for some reason.

Can you install the Lotus diffuser so it's at a similar angle as it is on an Elise? Need to cut out a section of the rear bumper cover?

This guy is the only one I've seen in the aero forum sections around the Internet that has done similar things to what you want to do https://www.trackhq.com/forum/the-equipment/aerodynamics/7120-i-finally-got-a-wing-results-inside

https://www.trackhq.com/forum/the-equipment/aerodynamics/7042-home-brewed-ground-effects

NOT A TA said:

"I'm thinking of taking air in under the nose, and blowing it out into the wheelarch and through louvres above the wheels, 917 style. "

Why do you want to do this ^^^?

I think what they did with the GT3 might be more appropriate... and maybe what Rigante was proposing?  The 356 already has the little grills next to the turn signals.  I'm just not sure there's enough volume to stuff a radiator on each side in that space in the fender in front of the wheel and below the headlight.

NOT A TA said:

(1) If the engine cover/trunk lid is strong in the area where the bumpers are (won't flex much) you could move the supports back to that area and attach to the lid directly instead of the structure between the shock towers? Then you could open/close more easily.

(2) 8" seems like it might be kinda low causing the wing and rear spoiler to work against one another. Do you know others with a similar car with wing set ups? Any CFD studies done on similar cars?

(3) If you use your plywood mounted flat up to the bottom of the frame rails would the braces interfere? Hard to tell in pic. Is the plywood wide enough to stick out on the sides by the rockers?

(4) If you are able to mount plywood to bottom of the rails would you be able to transition to the Elise diffuser cleanly?

(5) Will the plywood/diffuser restrict engine cooling? I've seen that the Lotus use NACA ducts in the flat area ahead of the diffuser for some reason.

(6) Can you install the Lotus diffuser so it's at a similar angle as it is on an Elise? Need to cut out a section of the rear bumper cover?

(7) This guy is the only one I've seen in the aero forum sections around the Internet that has done similar things to what you want to do https://www.trackhq.com/forum/the-equipment/aerodynamics/7120-i-finally-got-a-wing-results-inside

https://www.trackhq.com/forum/the-equipment/aerodynamics/7042-home-brewed-ground-effects

 

I numbered your questions to try and keep it inline, hope it helps...

(1) Definitely an option, and much more logical 

(2) I've watched some of that Julian guys' aero videos and 8" seems to be a mix of high but not too high. I also found this video, which seems to be helpful https://youtu.be/vB1iAnpuHR4

(3) It wouldn't interfere, the bottom of the brace is just shy of the bottom of the frame rails, in height/ depth

(4) That's the plan, to have it totally smooth all the way beginning of the diffuser.

(5) I've also seen the NACA ducts, but also don't know what it's for. Possibly the oil cooler that the Elise have for the 2ZZ which Toyota doesn't have for its own 2ZZ

(6) The angle will be identical and whatever needs to be cut will be cut (bumper or whatever else is in the way)

(7) He is also on Spyderchat, though the linked forum seems like a fun place to be. Might have to sign up there too haha 

It almost seems like the flat underbody would be a larger benefit than the Wing. That's why Im here doing "research" before I start hacking body panels. I'll be at Streets of Willow this weekend for the AROSC driver school. I've done it in the past and figure I'm ready for the Intermediate group but no roll bar means I'm with the rookies/ newbies. All good, first time on track with this car and it's my first mid-engine car so why not start from scratch 

In reply to 2mAn :

Awesome build! I'll definitely be following your progress. 

If you can trace the wing profile, there's a lot you can do with free tools (javafoil) to find an estimated best angle of attack and to help estimate the total downforce and drag the wing will create. That will help with engineering the mounts and such. I ended up doing similar with a wing in this thread:

https://grassrootsmotorsports.com/forum/off-topic-discussion/can-anyone-take-a-photo-and-turn-it-into-a-plot-of-points-xy-axis-wing-profile-content-inside/175500/page1/

The Julian guy is a street car guy not interested in the same things we want for track cars. Mostly says I make videos and wrote a book, buy my book.

I'm in a hurry and be back later but I'll leave this for now.

https://www.youtube.com/watch?v=H8EX_ZcrdxA&list=PL6R7zR4ZbGkOny_RGsc2V3DULdd2SPwSU&index=8

If you can attach to the bottom of the frame rails and to the brace (using spacers) it should be pretty easy to create a flat bottom.

Will you have a splitter up front? Does the car under steer at speed without any aero modifications? Find out this weekend!!!  If so, reducing lift/creating down force at the rear may make it worse unless changes are made at the front to reduce lift. Gotta keep your balance! The stock Lotus rear diffuser and under tray were designed by folks waaay more knowledgeable than we are and engineered knowing where they wanted the center of pressure to achieve the balance they were designing for on that car.

I would investigate what the NACA ducts were for on the Lotus to hopefully prevent issues resulting from your under tray/diffuser installation potentially limiting cooling. You may need to install a similar oil cooler?

That forum where I linked the MR2 aero project is kinda quiet now. Several years ago it was one of very few forums with an aero section. My project is posted there and I keep saying I'm going to post it here but haven't done it yet because it'll take hours to move and bring up to date. https://www.trackhq.com/forum/the-equipment/aerodynamics/9416-very-old-bird-gets-updated-aero

I mentioned the flat bottom sticking beyond the rockers because the rounded rockers will probably let air roll under the side of the car, possibly reducing the effectiveness of the flat floor to some degree

Im going to start my own thread for my car to not take over this thread

In reply to NOT A TA :

I'm looking for the least disruptive way of getting decent airflow through the radiator. Most modern cars do something along these lines, but as i said i'm totally open to ideas. the little horn grilles are too small but an inlet under the nose wouldn't be seen easily on the street. Rod Emory louvers the tops of the fenders and what I'm aiming for is a bit of the pumped up feel of a modsports car/ 70s circuit racer like Retropower are doing with their minor, with a bit of Singer thrown in


special saloons

In reply to Rigante :

So Sleepy was thinking what you were thinking! Nothing says all the air you need for the radiators all has to come from one place. Perhaps a combination using the small horn grills along with a small unobtrusive scoop under the front? Need to calculate the duct opening size necessary for the radiator and that's probably dependent on multiple parameters like exit duct, fan, core size, etc.  I like fender louvers. Here's some on a GTM I've been doing bodywork on. They're "add on" louvers that were really rough to start with but they'll look nice when I'm done and the car's in paint. .

[URL=https://app.photobucket.com/u/NOTATA/a/9431e992-e7d7-4375-ab32-667aefbfe51c/p/40eb8d11-ec59-41b8-ad33-5b98f467f0c8][/URL]

[URL=https://app.photobucket.com/u/NOTATA/a/9431e992-e7d7-4375-ab32-667aefbfe51c/p/2412a3b9-37a5-4251-8d2f-447747902cea][/URL]

love that GT40, what a monster, i can CAD and 3d print moulds, but plan on sculpting the fenders in foam then scanning them in. It's all theoretical for now, but i have a great price on a grp shell 

In reply to Rigante :

Update? Did you get the shell?

Here's an interesting one for ya:

I have a horizontally mounted oil cooler on my car.  It is mounted on the bottom of skid plate at the front of my car.  It works by pressure differential since the air running under the car is low pressure and the car in the air dam is high pressure. 

I have gotten it to work quite well as it drop the oil temp nearly 30 degrees when cruising at 80 mph.  

I am working on reducing the amount of drag the system creates and if I can improve flow through it at all, I would like to do that too.  

I added in the picture a "duct" BMW makes for their oil cooler which is mounted the same way.  Would making a diy one of these be advantages for the flow? I have a cover I place over the cooler so it does nothing for street driving so I can I keep the oil warm.  I only take off the plate at the track.  Would making a louvered cover be more beneficial than no cover at all? 

Also,  would adding some sort of diy turning vanes above the cooler help direct air through the cooler or does this not matter as it's mostly relying on pressure differential and not really "flow" per se.

  I've added some pictures so you know what I'm talking about. 

In reply to Bmsluite :

the only way to reduce drag on a system like that is to reduce the flow to it. the Grill area of a gar is 30% of your overall drag. reduce your grill opening and reduce the drag.  

I see that you have a low downforce and a medium downforce kit for the NA/B Miata. Does this infer that a high downforce package is on the way?

In reply to mistanfo :

the Medium DF kit uses the core component needed to make a high downforce kit. 

You're only a dual element, splitter ramps, and canards away.

In reply to mistanfo :

the Medium DF kit uses the core component needed to make a high downforce kit. 

You're only a dual element, splitter ramps, and canards away.

Yes, skirts do in fact work even when used without a flat floor. The operational effect is to reduce the amount of air rolling up under the car between the front and rear wheels. By doing so, the low pressure at the back of the car is effectively used to create a low (lower than the pressure on top of the car, on average) pressure under the car, and therefore downforce. They work better when the bottom of the car is relatively free of stuff hanging down in the air-stream and they work the best when you can keep them close to the ground. If the skirts are up off the ground very much, the effect is to roll up a vortex along the bottom edge as the air tries to go around the sharp corner. This does create some local low pressure, but vortices are draggy by their nature (lots of work spent rolling them up).

We have the ASA Camaro project basically together with splitter, skirts and wing. I've done some moderate laps and the car feels predictable and planted at speed. 
The wing is set as seen below.

First question: Is the wing set reasonably as a starting point to your eye (if you can tell from these pictures)

Second question: I think of the splitter/wing sort of like front/rear sways. I set the front and adjust the rears. So, the splitter is set, and wing is adjustable. Is that logical?

Third question: The only way I know of to optimize the wing/aero is to go faster and adjust. I know I'm missing stuff. But what?

Johnny and Marcus...thanks for making great, reasonably priced gear for our sport. 
 

stafford1500 said:

 They work better when the bottom of the car is relatively free of stuff hanging down in the air-stream and they work the best when you can keep them close to the ground. If the skirts are up off the ground very much, the effect is to roll up a vortex along the bottom edge as the air tries to go around the sharp corner. This does create some local low pressure, but vortices are draggy by their nature (lots of work spent rolling them up).

What would you consider "low to the ground?".  I'm thinking about adding skirts to help the diffuser and hopefully put some downforce as far forward as possible.  We will also be enlarging the front splitter,

YoursTruly said:

In reply to jh36 :

For your first question about wing angle, remember that flow will want to stay attached to the roof as it passes over the car. This means that the wing angle relative to the ground and the wing angle relative to the airflow are not the same. Stated another way, the effective angle of attack may be a couple degrees steeper than the static AOA.

I am no expert, but this is where a wickerbill or gurney flap can come in handy. It can increase the amount of downforce without necessarily increasing AOA. 

All that to say, I think you are at a good starting point because it is very easy to set the wing too steep. My understanding is, the 9 Lives airfoil gets far less efficient over 5 degrees AOA. 9LR can feel free to correct me.

I am starting mine at 3 degrees with a 1/2 gurney flap.

That's very helpful...thank you. I found some data on the 9LR wing with/without the GF and that is something to consider for sure. Looks like 5 degrees is a good stopping point and the GF can add more downforce without the addition drag of going to 10 degrees or so. Good stuff. Your 3 looks like a great spot to be in. Thanks. 

In reply to YoursTruly :

That is excellent news.  Thanks for sharing...I am looking into the gurney flap currently...looks like the way to go.  Well played.

I have a stripped and modded '89 Mustang LX that I use for track days. It's very much an ongoing project. While the nose of the car is a project in itself I would like to take some small steps in the rear. I was thinking about a gurney flap on the stock LX spoiler but my searching only turned up an AutoX mustang with a very large (~6") flap. It seems that I am sailing sparsely charted waters. My basic idea was a vertical strip across the back edge of the stock spoiler. What is a good starting height? Put another way, what's a ballpark 'minimum' height to be effective at all?

This is my first foray into aero stuff and things so I am looking at this as an ongoining learning experience. What am I missing?

How would you go about cleaning up the air flow over the roof to decklid transition on a porsche 914. Ive seen vortex generators there and air being ducted from the side of the car to the highly turbulent area. i don't know that either are helpful given the lackluster factory design.  If you are unfamiliar, its the same concept as the back of the cab of a truck with a tonneau cover. im looking to clean up air flow over that area for primarily reducing drag and cleaning up airflow towards my future 9lives dual element ive got my eyes on. 

Side question: does the open engine grill by the back glass change much there given the airflow is pretty negligible there?

In reply to Tazz9924 :

Can you extend the roof? Have you measured anything? A wool tuft test for the intended wing position would probably be the first step.