Aerodynamics of a Turd

[rdorman]

Hey DV. Did you look into the aero modifications made to a COBRA called the 'Turd' when designing DVII? The car ran one race, well, part of a race . Nassua speed week I believe in '64. 500 horsepower all aluminum, experimental V8. It was blowing everyones doors off until the engine let go ( I think it was the engine ).

But the interesting part was the way the exhaust from the radiator was set up. The entry to the radiator was sealed (between the 'snout' and the radiator as usual to force all through the radiator, snout was open). Aft of the radiator, ductwork carried all air exhausted from the radiator upward towards the front of the hood lid and exhausted the air back into the air stream through two louvered triangular (sort of) vents. Fresh air for the engine was picked up in front of the hood by lowering the body work in front of the hood to below the level of the hood where it was fed to the engine (bad sentence, I know). About where you have the NACA duct.

Venting the air from the radiator out the hood seems to be a great idea so long as you can accelerate it enough and have enough vent area. I know the outlet needs not be as large as the inlet but I am not sure what sort of inlet/outlet ratio would be appropriate.

I would probably reverse the hood scoop to pick up air from the base of the windshield as you have it reversed. (I know, it doesn't feed your V10 monster from the scoop!)

The Turd never raced again as far as I know. I beleive it was kept as a test car.

Any body ever run a rear lip spoiler with success?

Any body know the basic formula for calculating wing lift? Assuming clean air etc. Seems to me, that at its most simple, it would be a function of the volume of air above and below (different length path) as well as the pressure (weight) of the air. Just a simple wing approximation is all I am looking for.

[petek]

>>. I know the outlet needs not be as large as the inlet but I am not sure what sort of inlet/outlet ratio would be appropriate.
<<

Hmmm... I thought the outlet had to be larger than the inlet in order to have a lower pressure area on the outlet than on the inlet. Hmmm (again) ... or perhaps the inlet has to have a higher velocity of air flow (lower pressure) than the outlet (lower velocity).

Ack! Anybody know for sure?

petek

[rdorman]

I believe it is the latter petek. The air entering the radiator will slow creating a high pressure area in front of the radiator. The exhaust side has to re-accelerate the air flow to the velocity of the surrounding air in order to have hope of re-interducing the exhaust air cleanly. The air being heating comes into play as well.

Time for me to dig up Tune to Win again It just seems as though that amongst others aero issues, the Cobra body just cant get rid of a the air coming in through the nose.

Can't forget the diffusers where needed?

Maybe I should stop thinking about it so damn much and just build the thing!

Do you have the small block tunnel and firewall? If so does it add a lot of room? How is the car coming? Then again, I can just go out and check your site out!

[petek]

Ya know ... I've got this Motorola MPX4115 sensor sitting here (from a altimeter and telemetry project I did a couple of years ago). Perhaps I'll just cobble together a circuit with a range of 15kPa to 115kPa and check the pressure in front and behind the radiator in my little Neon ...

... then again, HEY Enzo, don't you have a mechanical engineering background? So what's the answer on the pressure, velocity, and heating effects? (I'm just a poor EE who doesn't even remember thermal dynamics or fluid flow!)



petek

[Dominik]

Guys,
what is going on here?

An aerodynamical thread w/o me? I like to learn more here!

I am an admirer of the Turd as well. There is a thread about that car (you may already know):
http://www.clubcobra.com/forums/show...threadid=11523

Don't think too much about air entering the radiator vs. exiting.
The idea once was just to keep the heat from the radiator away from the engine.
On other cars where the air is supposed to exit under the car nobody took total air volume into account - I think.

This rerouting causes tremendous heat at the windshield though!
Just ask a GT 40 driver.

And again, I am still supporting the idea to let some air move through the engine compartment, instead of forcing it all through the radiator.

That way your footwell won't heat up as much, plus your engine is able to radiate it's share of the heat - about 15% via the metal surface. (Radiator: 30%)

Desert Heat (at the end)

On todays cars the engineers try to keep coolant temp in a very narrow range, say 10K, to get a more uniform air/fuel mixture for the engine mangement system.
They almost seal the engine compartment and regulate via fan.

Aerodynamics may be a point here as well, keeping the engine compartment turbulent free. But at what price?

Todays cars need a/c ON even at moderate ambient temperatures plus need various additional fans to cool accessories like starter or intake valves ...
(Soon they need a fan to cool the fan...)


Dominik

[rdorman]

Great pics from Turk on the flip top! I scanned the four pages of posts but did not find the owners name nor how to contact him. If some one could help out here, that would be great. I was wondering how effective the routing of the radiator proved to be and what, if any, overheating problems he had.

Thanks again.

[Dominik]

Cal Metal wrote:

"Ric Mason of Carson City, Nevada (general vicinity). Someone on this forum lives close by his home and knows him personally."

I think he's the owner.

Dom