Some interesting aerodynamic info

[cudabob496]

On my 72 Cuda, I've removed the gas tank and have a fuel cell in the trunk. Have also removed the
rear valance. I'm building a rear diffuser now to install under the trunk area. It will be black, so shouldn't stand out too much. Will be angled from the bottom of the pumpkin to the rear bumper. All in the interest of going faster. Heck, the Viper has one!  There's some good discusions below on aerodynamic mods.  Seeing the Cuda (an earlier post) going over 200 mph maybe planted "a seed". Didn't the T/A Challenger have "eyebrow" spoilers? Also thinking about a front wind splitter, as my car gets squirly above 90 mph. Keep in mind about 30+ percent of engine power goes to just overcoming aerodynamic drag. (I recognize you "stock" purests will not find this very interesting)

http://aprperformance.com/index.php?option=com_content&task=view&id=69&Itemid=47

Below, click on "What is a diffuser" or "What is a splitter"

http://aprperformance.com/index.php?option=com_content&task=view&id=21&Itemid=44

[RCCDrew]

Cool project!

['Cuda Hunter]

Cool articles.  Thanks for posting that up.

I was considering building a diffuser for my 67 out of steel. 
The price for the viper fiber is up there. 

Are you planning on making your own diffuser?  Or are you purchasing one of the fiber ones?

[cudabob496]

Cool articles.  Thanks for posting that up.

I was considering building a diffuser for my 67 out of steel. 
The price for the viper fiber is up there. 

Are you planning on making your own diffuser?  Or are you purchasing one of the fiber ones?

Making it out of thin but strong 7 layer plywood.

[brads70]

similar idea....   http://www.protouringmopar.com/showthread.php?1427-Need-some-opinions-on-how-this-looks

[RCCDrew]

What about ABS plastic?

[cudabob496]

well, got it in, and painted.  $25 of material.  Board angles
up from bottom of pumpkin to rear bumper.  Have 3 strips of metal 7 inches apart, 3 ft long,
and two inches high, to help direct airflow. For now board is only 2 ft wide,
and about 3.5 ft long, and nestled between the dual exhaust pipes. With this
initial mockup, can now cut a piece that is wider and wraps around 3 inch exhaust pipes.
On each side of pumpkin, there is a small pipe bracket on the board, through which I passed large tie wraps,
and have tie wraps around axel. Tie wraps are the big ones, with 175 pound breaking strength.
Was gonna use large hose clamps.  Tie wraps allow suspension to flex. Other end of board bolts
to upper bracket that held rear valance. Jury rigged, but should stay in place. Time to hit the road, and see
if anything falls off.
 

['Cuda Hunter]

Love to see some pics!

[Surfmichaels]

Admittedly most of my aero ideas come from f1 but i thought that a diffuser loses exponential efficiency the higher up it sits, and that a flat floor and a very low front splitter were needed to drive it. I wonder what the nascar cars of that generation used for high speed stability. Although those devices may help aero balance I can't imagine it playing a big effect on total drag much at all, there are simply too many other aero design issues with cars of this era.  Still will look awesome though! Pics!

Edit: good slightly more detailed diffuser link http://www.racecar-engineering.com/technology-explained/diffusers-engineering-basics-aerodynamics/

[cudabob496]

Admittedly most of my aero ideas come from f1 but i thought that a diffuser loses exponential efficiency the higher up it sits, and that a flat floor and a very low front splitter were needed to drive it. I wonder what the nascar cars of that generation used for high speed stability. Although those devices may help aero balance I can't imagine it playing a big effect on total drag much at all, there are simply too many other aero design issues with cars of this era.  Still will look awesome though! Pics!

Edit: good slightly more detailed diffuser link http://www.racecar-engineering.com/technology-explained/diffusers-engineering-basics-aerodynamics/

I find that a stock E-body can get really squirly at high speed.  A few years ago I installed a 4 inch front spoiler on my Cuda, and that helped
settle things down quite a bit above 80 mph.  But you are right, there are other things that should be done to take full advantage of a diffuser. With my gas tank out, and no rear valence, there is a big void in the back of my Cuda, and all you see is the rear differential.  It looks "dragster" cool, but probably not very aerodynamic. Maybe like pushing a brick, with a large negative pressure area in the back.

I'll also see if there are areas under the car where a flat panel might be installed, to minimize under car turbulence.
After all, I'm retired, and there's nothing else to do!

[cudabob496]

Love to see some pics!

Yes, tomorrow I will try to get one.  When I drive it, will also report if I feel any difference in high speed handling.

[dodj]

Admittedly most of my aero ideas come from f1 but i thought that a diffuser loses exponential efficiency the higher up it sits,

True enough. Any diffusers I've seen are only for looks.
Nothing wrong with experimenting though!
 

[Surfmichaels]

I think what your doing is a great idea, I plan to road race my car and have been thinking a lot about high speed balance, just wanted to add as much info as possible. I've focused, for now, on a good alignment set up that includes new UCA to allow as much caster as possible (camber?) then I got a repop trans am size front spoiler that I believe will help with some of the front end lift issues, and will give a good platform for cooling ducts if needed. Love to hear more feedback as you get it on the road.....


These are for modern cars but the concepts are applicable even if their solutions are less relevant...
http://www.autospeed.com/cms/A_2455/article.html
http://www.autospeed.com/cms/A_2456/article.html
http://www.autospeed.com/cms/article.html?&A=109937

[cudabob496]

I think what your doing is a great idea, I plan to road race my car and have been thinking a lot about high speed balance, just wanted to add as much info as possible. I've focused, for now, on a good alignment set up that includes new UCA to allow as much caster as possible (camber?) then I got a repop trans am size front spoiler that I believe will help with some of the front end lift issues, and will give a good platform for cooling ducts if needed. Love to hear more feedback as you get it on the road.....


These are for modern cars but the concepts are applicable even if their solutions are less relevant...
http://www.autospeed.com/cms/A_2455/article.html
http://www.autospeed.com/cms/A_2456/article.html
http://www.autospeed.com/cms/article.html?&A=109937

Some great info!!

[cudabob496]

needs more paint and some rework, but you get the idea.
Will probably make fins larger.

The 200 mph Cuda posted earlier had the exhaust tips right at the bottom of the diffuser.
If I did that, could eliminate the two 3 inch lines going to the large tips.  And, make the diffuser
a lot wider. Just don't want to cook the fuel cell.