AERO/GEN1 Camaro ASA stock car

I am in the midst of a race car build which can be found in the project section..."Gen1 Camaro/ASA Stock Car build".  In short, this is an 2001-ish ASA Late Model Stock Car that had a Monte Carlo body on it.  I've modified the cage to fit a fiberglass, Gen 1 Camaro body.  

The goal is to race in ST1/TT1 in NASA Mid Atlantic.

The rules for aero in ST1 are pretty open, so in my minds eye, I see splitter, canards, a wing and skirts.  I have fabricated and attached the skirts at this point, but I'm looking for advice on how to proceed with developing from the aero point of view.  The car currently has a fairly stock ls1 in it, so i don't have massive horsepower to work from at this point.  I have not put it to the dyno but it was said to be making about 420 hp which seems about right for the ASA specs of yore and that's about what my massaged C5 is making.  I also have not scaled it yet, but I believe it will come in around 2650 lbs with driver.

NOT A TA suggested I start a thread here to answer some of my musings.  Below is an image of the skirts I've attached.  Along the way, I will be fabricating a splitter.  I have been in communication with Johnny at Nine Lives Racing about a wing design.  I am working on the best method for bringing cooling air in the cockpit (this thing is going to get warm inside).

I'm a blank canvas and ready to absorb aero knowledge...I know a trifle about it and have a basic understanding of high/low pressure and their effects on the car.  It was suggested to me early on to test the car with little/no aero and go step by step....I'd like opinions on that as well.  One alternative would be to build a splitter (because I know I will want one), continue with my skirts (because that's the best way I can figure to attach the body) and put on an original "duck tail" lip on the rear and see what happens....then add the wing as needed.  Or...just go for it.

Link to build thread https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/gen-1-camaroasa-stock-car-build/177739/page1/

Are you allowed to have the splitter continue rearward to an under tray/flat bottom?

We got on the subject of cabin cooling in the build thread and someone posted pics of the early 70's era ram air scoops that were used on the A pillar. While they've got the vintage cool look going for them I suspect use of them stopped because of high drag. Here's a pic I took while I had some time to spend with a modern era World Challenge car. Note the air ducts built into the hood. They had it set up to get air from ahead of the core support & channel it through the hood to vents in the cabin. Not suggesting this design would necessarily be good for your car but it might be an option or lead to other thoughts.

[URL=https://app.photobucket.com/u/NOTATA/a/eb4f49cb-c2d4-4ddd-ad6c-d203fd6bdf62/p/5c26b9ef-85b2-4e24-ade1-dc8d92fa7520][/URL]

In reply to NOT A TA :

I am taking a "non-production vehicle" penalty as a tube frame. So I am restricted to how far out a splitter can go but there is no restriction on undertray or flat floor. 

The way the car is designed, it is pretty clean underneath also.. The exhaust is above the bottom floor and exits through the passenger door. 

Are you allowed a rear diffuser and if so are there any restrictions on it?

"Aerodynamic devices and/or modifications may not protrude more than six (6”) inches from the vertical plane from the ground to the widest part of the right and left sides of the vehicle’s body.
Front wing/spoiler/foil/splitter may not protrude more than 12 inches in front of the outermost edge of the front bodywork/fascia, and may not be higher than the lowest part of the vehicle’s hood."

Taking the tube frame/non production vehicle ding exempts me from a lot ( but it is a big ding) but these rules apply to all. Since we are going to be wheel to wheel racing, I don't know that I want to be hanging out too far anyway. 

Sounds like a full splitter to rear diffuser is in your future! They don't even say no tunnels? Do you have a link to the rules for the class?

Since you mentioned you have limited knowledge about race car aerodynamics I'll suggest  you get one of either McBeath's or Katz's books.

Race Car Aerodynamics by Joseph Katz

Competition Car Aerodynamics by Simon McBeath

The Katz book is a bit more technical and has more of the math involved and the McBeath book is a bit more for the average Joe but they both cover pretty much the same topics. You can buy one of the books on Ebay used, read it, then read it again with a better understanding, then sell it on Ebay for basically the same you paid for it so all it costs you is a couple bucks shipping. Make sure the seller you buy from uses USPS Media Mail for the really cheap shipping rate. Either book will provide you with the basics and you'll be better able to discuss the topics as you progress with the project.

In reply to NOT A TA :

Very interesting. As you said, this exact design would not be a realistic option but, isn't there high pressure at the base of the windshield?  
would it be effective to have vents at the base of the windshield duct into the cockpit?

In reply to jh36 :

Yes, high pressure at base of windshield, that's where the air is taken in on the stock Camaros for the HVAC.  However if there's an engine compartment fire it could get bad in the cabin very quickly if there's fuel involved and it has a quick way to blow through the firewall.. Steve Stafford may have some suggestions for you when he finds this thread. He's an aerodynamicist currently working in NASCAR on the Toyota Cup Cars and I'm sure he's pretty familiar with the chassis design you started with.

https://nasa-assets.s3.amazonaws.com/document/document/20305/ST1-4___SU_Rules_2020--v14.2--2-11-20.pdf

Here you go!  The rules cover several performance classes, so it can be a little cumbersome to navigate. We should be in ST1 and will be taking the "non-production car" penalty. The way I read it, the undertray is free if you take the penalty. 

regarding the books....I'm on it!  Thanks for the tips. 
 

regarding the windshield high pressure, you have started my wheels turning, and it's good to figure out the plan sooner rather than later. The one piece front does have a hood, but it is longer than stock and there is no literal cowl. The firewall is in the ASA stock position still but there is a gap between the top tubes where I removed the stock car dash. My plan is to fill this gap with aluminum and heat shielding...adding some ducting to sleeve into the hood would be pretty simple by lifting the hood straight up on removal. 
 

I look forward to other experts chiming in. This forum certainly is a great resource. I appreciate your help. 

The world of Simon McBeath is vast!  Many years ago I absorbed all I could from Carrol Smith's books. These look similar, but maybe more modern and specific. 
I see there is a book on Downforce and one on Aerodynamics. The Aero book is more recent so I assume it covers all the bases. 
also available as an e-book but I do like page turning. 

The rear edge of the hood where it meets the cowl is an area where you'll have some things to figure out. Will the intake for combustion be from an opening at the rear of the hood that's sealed to the intake? Will the hood be sealed to the cowl to prevent high pressure air at the windshield base from entering the engine compartment?

jh36 said:

https://nasa-assets.s3.amazonaws.com/document/document/20305/ST1-4___SU_Rules_2020--v14.2--2-11-20.pdf

 

Here you go!  The rules cover several performance classes, so it can be a little cumbersome to navigate. We should be in ST1 and will be taking the "non-production car" penalty. The way I read it, the undertray is free if you take the penalty. 

regarding the books....I'm on it!  Thanks for the tips. 
 

regarding the windshield high pressure, you have started my wheels turning, and it's good to figure out the plan sooner rather than later. The one piece front does have a hood, but it is longer than stock and there is no literal cowl. The firewall is in the ASA stock position still but there is a gap between the top tubes where I removed the stock car dash. My plan is to fill this gap with aluminum and heat shielding...adding some ducting to sleeve into the hood would be pretty simple by lifting the hood straight up on removal. 
 

I look forward to other experts chiming in. This forum certainly is a great resource. I appreciate your help. 

I'll go have a look at the rules so I'm familiar.

McBeaths Competition Car Aero should give you a good overall. I bought the newest versions of both books a couple years ago as a review and to update myself and compare them so I'd know more about the content of the current versions of each when recommending them on forums like this and then as suggested I sold them.

I've been interested in fluid dynamics since I was a little kid and studied in various ways through life.   I certainly wouldn't consider myself an expert in race car aerodynamics and my hope was that by starting this thread real experts would chime in.

If the section of the cowl area you need to put sheet metal in is part of the firewall separating the engine compartment and cabin I would not use aluminum. It melts way too fast, better to use steel.

I do have my own aero project I'd started long before this section of the forum was started and I'll start a thread about it.

In reply to NOT A TA :

Steel it is. Plus, I have a good stockpile of it at the moment. Thanks!

In reply to NOT A TA :

"I do have my own aero project I'd started long before this section of the forum was started and I'll start a thread about it."

Please let me know when that hits the forum. I'd love to learn from your project and maybe avoid some ignorant questions as I proceed. 

In reply to NOT A TA :

The details are not all determined but...

the intake will come from the front, relatively low from the original Nascar design. I will be documenting this modification on the other thread as I get to it. 
 

the hood will have a seal that is a continuation of the firewall. I have to finish all the mounting to show this, but the theory will be a piece of steel with a flexible seal at the top that will stop high pressure entry into the engine compartment. I can likely angle this forward far enough to protect the cockpit from fire, project the engine bay from high pressure intrusion and also have room to duct high pressure cooling air in the cockpit. I'm starting to see how I can accomplish this, again, by lifting the hood straight off and not tilting. 
 

In reply to jh36 :

I have a few threads I'd started on other forums that had aero sections or were marque specific. When I post here I'll combine info from all of those threads. Meanwhile, you could check this one out http://transamcountry.com/community/index.php?topic=71522.0

In reply to NOT A TA :

That was a great read. You have some patience to test that assortment of side vents. You also touched on a couple of points I have wondered about. 

My aftermarket body does not have provisions for fender liners, so I was going to block what I could and vent out the hood and with large-Ish side vents. When I got the car in it's Late Model form, it also did not have them. The construction of the frame and front suspension geometry might make them difficult. 

In reply to jh36 :

This is a topic for Mr. Stafford. He knows all about about those cars and how/why they work aerodynamically. My car is a production car so a lot of things are different than a dedicated race car. There are "tricks of the trade" he might recommend for your car because of the differences in bodies between your Camaro shell and a NASCAR shell plus the relatively loose regulations on your class. I suspect since he hasn't chimed in yet he might be on vacation or something since the race season just ended for him with the championship at Phoenix.

In reply to NOT A TA :

Fortunately, there is plenty of other work to keep me occupied as we wait for Mr. Stafford. I did not see an accelerated education in fluid dynamics coming around the corner at me!  This is quite an enjoyable journey. 

I am picking up enough knowledge to become slightly dangerous.  I thank you.

Most of my racing life has been in Porsche 944’s.  I have experience fabricating various ways to direct air into the radiator and intake, but as a fairly leaky street car, air came into the engine bay from everywhere I’m sure.  Last year I added TrackSpec hood vents, which helped a surprising amount with the way the car tracked, planted and stay composed in high speed turns.

With the “Camaro”, I have a different reality and some different options.

This car has a one piece front end (two piece if you count the detachable hood) made of fiberglass.  There are no penetrations at all in the front of the car at this time.

The NASCAR body radiator and intake funneled in from down low.  Once I fit the body firmly and have the front end also firmly attached, I will know for sure, but I believe it may be feasible to bring the air in UNDER the spoiler and just over the splitter by putting a 1.5-2” space between the two.  If that is possible, is that preferable to cutting higher up? 

If it works out advantageously for air in, it would eliminate cutting the front which would strengthen the front and better keep air out of the engine compartment.  It may be that I need to trim up into the spoiler a little (if the splitter ends up too low) but even that would be preferable to cutting a large hole out of the front.

I plan to leave the traditional grill area closed.  Rather than put the “67 Camaro Decal” on the front, I am planning to put an RS grill on the front with LED headlights in the appropriate spots, behind the louvers.  I would like to attach brake ducts to the front as well, but that would be the only additional holes i would cut in the front.  

I plan to still put vents in the high pressure areas of the hood and fenders to evacuate.  There are no liners at the fenders to keep air coming in from the wheel wells...that is the biggest culprit I see at the moment, but i believe the hood and fender vents should combat that.

Thoughts?

Here is the blank canvas.  I am imagining the airbox just under the front spoiler and the splitter directly under that.  The gaps to either side of the airbox would be filled in with an airdam.  I would not penetrate the front end except to locate brake cooling ducts.  This is all a bit in the future...probably a few weeks out, but something to ponder while making stuffing and Guinness Chocolate Cake in preparation for Thanksgiving dinner.

I'm really interested in what Steve has to say.

Chrome wrap on the "bumper" ?

Have you measured the size of the openings below the bumper if they were cut out? If they're big enough to provide the same area as the air box on the original NASCAR set up they might be a good place to seal a box to the inside of the fiberglass and by attaching a plenum to the fiberglass it would help strengthen it. Paint the inside of the plenum flat black and the openings would look stock to compliment your stock grill.

If those openings below the bumper are larger than the NASCAR air box requires perhaps you could get the air for the brake ducts from those openings also so you don't have to cut individual holes for them.