Some interesting aerodynamic info

[cudabob496]

wow, below the door, there is a flat area, about 2 inches wide, that runs from the front
wheel well to the rear wheel well. Perfect place for mounting a 3 inch side skirt.

[MTS-Challenger]

I used 4" vinyl wall base trim for side skirts on my 83 TransAm. Worked great!

[miamivice]

I used 4" vinyl wall base trim for side skirts on my 83 TransAm. Worked great!

Seriously?  How did you mount it?   I have an 87 TA that came from the factory with some side skirting, almost same material.   I also have a 88 GTA that either didn't come w/ it or it was removed at some point.  Never thought to bother to add it, but curious how this worked out

[MTS-Challenger]

Seriously?  How did you mount it?   I have an 87 TA that came from the factory with some side skirting, almost same material.   I also have a 88 GTA that either didn't come w/ it or it was removed at some point.  Never thought to bother to add it, but curious how this worked out

There is 3/4 - 1" vertical lip along the underside of the rocker area (same as the Challengers) , I just used some sheet metal screw with washer every 6-8" for mounting so the skirt would extends down below the rocker panel.  I also had to angel cut the front leading edge near the front tire to help go over speed bump. Car was so low the vinyl skirt would rub and push out on speed bump and driveways. The cool part is the vinyl is cheap to replace.


The factory Trans Am skirts are mostly for looks as these are just added over the rockers and door and didn't hang low enough to get good ground effects (also had a 87 SSA).

My TA was an 83 MSE - Motor Sport Edition (#55 of 150) Mecham SSCA (very rare bird), it already had the SCCA front and rear spoilers but no skirts for the 83 year, so I added the vinyl for the sides (and low) to help with the down force. Corning G force on these cars was already at a close .92 from Mecham.
http://www.firebirdgallery.com/dkmlot10.htm
(fyi - mine looked like #147 on the link page)

[cudabob496]

I used 4" vinyl wall base trim for side skirts on my 83 TransAm. Worked great!

great idea

[cudabob496]

ok, bought a 10 ft sheet metal rain gutter from Home Depot for $6.
Cut lengthwise, and mounted one section under side rocker panel,
to act as side skirt.  The section in the picture now is about 5 ft long, and held
on by 6 sheet metal screws (#12s I think).  Will complete this side, and the other,
then paint satin black, so hardly noticeable, but a sturdy 3 inch side skirt!

Basically will run from front wheel well to rear wheel well.

The gutter has a sharp straight side, and a curved side. I choose the curved side
for safety, as the straight side would be like a giant knife!! Slip off the jack, and you would
get the big ginzo knife!!

Above the skirt is the normal chrome side strip that came on 72 Cuda's.

So, when this is done, will have front spoiler and splitter, belly pan from splittler to oil pan,
belly pan from header collector to mufflers, diffuser in back, and these side skirts.  All of which, from a short distance,
should not stand out at all, as to distract from the normal Cuda look.

since about 14% of air drag comes from front tires, last aero project will be to continue the front spoiler around each side
to deflect air away from tires.  Still thinking about how to do this.

['Cuda Hunter]

Love your project.  Thought I would post a pic of a duster from carlisle.  From Ravage's pictures.
Just reminded me of what your doing.

[cudabob496]

that boy is ready to run at the Bonneville Salt Flats!!

I like his cold air induction system!  That's a horsepower adder!!

On a Cuda, there is an upper and lower portion of the entire front, where air
can enter. The lower portion has the running lights. Wonder if the lower portion
can be blocked off, and the car still stay cool. Probably won't do it though, since
it would change the stock look to much for me.

Obviously a Cuda with the nose of a Superbird would be the ultimate Cuda aero machine!

by the way, just realized that instead of ordering sections of sheetmetal, to make things,
I can get it cheaper by buying cookie trays at Walmart, and cutting them up! Or one of their
$8 2ft by 4ft drip trays for under a car! Good sheet metal sources.

[falkenracing]

I wonder where it would be most beneficial to block of the front, the upper or the lower portion you're talking about?
With the splitter in fron, there have to be some good air presure down low, wich might allow for a smaller opening over all. But on the other hand, slow speed, normal driving, the inlet might get to small for cooling the engine in traffic and such.
And then again, I'm just a mechanic with no experience at all when it comes to this, but I have a feeling I've read about this before.
This thread is inspiering to say the least.

[cudabob496]

I wonder where it would be most beneficial to block of the front, the upper or the lower portion you're talking about?
With the splitter in fron, there have to be some good air presure down low, which might allow for a smaller opening over all. But on the other hand, slow speed, normal driving, the inlet might get to small for cooling the engine in traffic and such.
And then again, I'm just a mechanic with no experience at all when it comes to this, but I have a feeling I've read about this before.
This thread is inspiering to say the least.

I took my car out today, with it being 100 degrees out.  wanted to try out the new side skirts. The temp needle was steady at 200 when cruising.  I think the new front splitter definitely has increased front pressure, to hold the car down more, and to force more air through radiator.  As far as blocking one section of the front, problem is both sections, when you look straight at them, contain radiator and trans cooler surfaces, so gonna have to be careful on this one. I'm sure in the winter, when its 40 degrees out, there would not be a problem in blocking off one of the two front sections.

As far as all the aero mods now, the car is steady as a rock at higher speeds, and seems to be a little faster, given all other things the same.
But I mainly like the high speed stability.  And the mods aren't really noticeable from a distance.

just a mechanic? that takes skills and brains!!

[falkenracing]

Have a vauge memory about a duct being used (did read a couple of books on race car engineering years back) wich was smaller in size up front, and then expanded to cover the complete area of the radiator further back. This was used when the front was blocked of like i mentioned. I wonder if that could be effective enough to work in an "everyday" road car, or is just for racing. That and the addition of a couple of ducts to vent air from the engine bay right behind the radiator to get rid of the under-hood pressure and aid the cooling by creating a larger pressure difference would be interesting enough to see or hear some experience about.
Not that I think this is something one would have to experiment with, it's more of an open thought when we're discussing the subject.

[cudabob496]

Have a vauge memory about a duct being used (did read a couple of books on race car engineering years back) wich was smaller in size up front, and then expanded to cover the complete area of the radiator further back. This was used when the front was blocked of like i mentioned. I wonder if that could be effective enough to work in an "everyday" road car, or is just for racing. That and the addition of a couple of ducts to vent air from the engine bay right behind the radiator to get rid of the under-hood pressure and aid the cooling by creating a larger pressure difference would be interesting enough to see or hear some experience about.
Not that I think this is something one would have to experiment with, it's more of an open thought when we're discussing the subject.

good chance that whats works at 100+ mph, would not work in bumper to bumper traffic.
yep, relieving under hood pressure is a big positive.  Old racers would jack up the back of the hood
2 or 3 inches, and gain 2 tenths of a second in the quarter mile. Plus, you would get better cooling.

[cudabob496]

found this on the net:

The force of aerodynamic drag (Fd) regarding an auto is the product of the drag coefficient (Cd) times the frontal area (A), multiplied by the square of the velocity. Overcoming Fd requires a propulsive force rising as a cube of velocity. An ordinary car traveling at 40 mph may require 20 horsepower to overcome aerodynamic drag, but this would rise to 160 hp at twice the speed (80 mph).

So, all these little mods we do, like spoilers, under trays, diffusers, wings, etc, must be reducing the Cd, which therefore is giving us a perceived hp
increase.

so, if my Cuda is at 100 mph, it may be consuming 100+ hp just to maintain that speed, due to aero losses.  I guess all the other engine horse power is being consummed by the internal engine and drive train friction, and friction of tires on the road.  Add aerodynamic drag, and what's left over must be brake horse power.

[brads70]

I found it interesting how I noticed my fender mods changed the airflow . It used to be when a bug would splat on the mirror it would come in the car now no air comes in the car till about half way down the door. There is actually a vacuum at the mirror area.
I have a buddy that used to crew on a Nascar team back in the day and he tells me that when the car cleared tech inspection they would yank on the front fenders on top of and in front of the wheels pulling them out an inch or two. He claimed it would add a few MPH on bigger tracks like Daytona etc...

Also interesting ( as Neil pointed out while talking about this at Carlisle) that the 71-74 Chargers had this shape from the factory.  Ever wonder why Petty etc... chose that body style...

I get making prototypes out of wood etc... but I'd suggest you can buy painted aluminum and plastic by the 4x12 sheet really cheaply .
http://www.allstarperformance.com/product.htm?prod=155
http://www.allstarperformance.com/product.htm?prod=147

Wood absorbs water , oil etc... and burns and rots.

[cudabob496]

was researching flammability of HDPE. Below, it looks like
the same as plywood. Wonder if it melts. I've got some
hot exhaust down there. Boy, could I use a lift in my garage.


In order of increasing Time to Ignition, the results of the ASTM E1354 Cone
Calorimeter evaluation are: Cormier RPVC, 24 seconds; Cardboard, 34
seconds; Sanicover, 42 seconds; Griffolyn, 43 seconds; Fabrisoil, 44
seconds; Typar, 52 seconds; Air Space Saver, 77 seconds; Plywood, 151
seconds; Plexiglass, 156 seconds; Red Oak, 266 seconds; and Dry Wall,
infinite (non-combustible).
 
(OK, found it, HDPE melts at 266 degrees F.)

Aluminum would be nice.  Only minor concern would be if something came off, would it break easily, or
would it cause a lot of damage.  Perhaps another advantage of initally using the .33 inch plywood.
But alum would seem to be the way to go!
Ya, gonna watch for any oil buildup on the wood!