Car Guys, Assemble!

[Skuzzy]

I'm not 100% sure what most diffusers are intended to do, but if you want underbody airflow to direct upwards you need it to stick to the surface longer.   A strip of tiny vortex generators might do the trick better than a traditional diffuser.  You could measure the exit airflow direction with some bits of yarn taped to the back of the car, if you don't go all the way and measure actual downforce with either a pressure sensor or something to gauge ride height (spring compression as speed increases).

The diffusers help shape a laminar flow from under the car and pull the air up as it leaves the rear.  It does hold the air a bit longer than the standard rear end does.  Yes, vortex generators might have to be involved as well. A lot of that design will depend on the actual flow.  Yes, lots of yarn/paper strips are involved.

Once I get the manometers placed, I'll have a better idea where the various pressure points are and then can formulate a plan of attack.

I know I am going to have to create a foil for the top of the windshield to release the pressure as it curls over the windshield.  I have an idea for that basic design already.  Just need to test the shapes.

[eagl]

Don't take this the wrong way, but a Miata and a cobra share the same basic roadster shape...  There was a shop trying for years to put together a 200 mph Miata and they were pretty much foiled by aerodynamics.  You just can't make a car shaped like a roadster go that fast without serious aero problems.

[Skuzzy]

Don't take this the wrong way, but a Miata and a cobra share the same basic roadster shape...  There was a shop trying for years to put together a 200 mph Miata and they were pretty much foiled by aerodynamics.  You just can't make a car shaped like a roadster go that fast without serious aero problems.

I agree. There is a limit to what can be done, but the Cobra has a lot of room for improvement.  It has always been an aerodynamic brick.

Most of what I want to accomplish to to help make the cockpit a bit more civil.  I do not see myself needing to go faster than 180MPH, but if I do want to go that fast, I want to know the car is going to stick to the road.

You are absolutely right there is only so much you can do, without an extreme violation of the basic design.

[eagl]

I may be mistaken but I think for a diffuser to really work well, the airflow under the car has to be managed and kept smooth the whole way from front to rear.  You don't have any laminar flow to work with under a car that doesn't have managed airflow front to back.  Since you're building from a kit you may be able to do that but you'll need to add removable underbody panels from the front air dam to the diffuser, and figure out how to eject radiator/engine bay airflow out the sides or top.

[Skuzzy]

I am placing a full length body pan under the car and a stealthy air dam around the front and along the sides (behind the side pipes).

Yes, I have to start from the front and manage the air flow all the way to the rear to have any chance of making a dent in the brick, that is the Cobra.

[eagl]

It sounds like you have some good ideas on making the cockpit livable.  I recall one of the euro roadsters would pop up a screened panel behind the cockpit above a certain speed, and apparently it almost completely eliminated buffeting up to high freeway speeds.  I've seen various convertibles with what looks like screen door mesh between the front seat headrests...

[eagl]

I am placing a full length body pan under the car and a stealthy air dam around the front and along the sides (behind the side pipes).

Yes, I have to start from the front and manage the air flow all the way to the rear to have any chance of making a dent in the brick, that is the Cobra.

I think your advantage is that you're not going to have to be paranoid about trading downforce for overall drag.  Race car designers can't just go nutso keeping the car planted because it'll drop their top speed.  If you lose a few top end mph in your cobra as a result of making it stick to the ground, you've probably still met your design objective.

[Skuzzy]

It sounds like you have some good ideas on making the cockpit livable.  I recall one of the euro roadsters would pop up a screened panel behind the cockpit above a certain speed, and apparently it almost completely eliminated buffeting up to high freeway speeds.  I've seen various convertibles with what looks like screen door mesh between the front seat headrests...

That is popular to do and does work.  Many of the Cobra owners place a fixed piece of acrylic, attached to the roll bar, for that function.

I am going to try and get the ari flow as smooth as I can, as it moves around the windshield.  If I can manage that, it will go a long way in reducing the buffeting and if I can find the points to move air from a high pressure area to the low one on the rear deck, I might just be able to create a near laminar flow over the top of the car.

Heck, it's a goal.  Might not be attainable, but it cannot get worse than it is.

[CAP1]

Another issue with the 11s had were number 8 cylinder popping when folks would add a mild power adding tune to the car.  I have read several instances where 11 owners had their engine go kaput and Ford wouldn't honor warranty since the car had an aftermarket tune.  Ford seems to have figured it out for the last three years though.. I haven't read too many instances of engine failure.

When I bought my 2010, I was berated by several for not waiting a few months to get a coyote powered Mustang.  I didn't let my decision nor the picking bother me after reading about all those failures.  My little 4.6 has 57K on it putting 596 measured HP at the fly wheel. Tough little motor.

Just ordered Steeda LCAs (upper and lower), Koni shocks/struts, Hurst shifter, 410 gears and a new diff.  I wore out the factory diff so the car doesn't "really" have posi-traction right now

 my understanding was that it was the computer strategy that the tuners didn't understand. thus, when one would tune a coyote using something that worked on a 4.6 liter...since the coyotes computer strategy was different, it tended to run the rear cylinders lean, and too hot. #8 was the most susceptible. i thought that went for the 012-present too, but i could be wrong.......

 and no....there's not a dam thing wrong with a 4.6 liter, 'cept the fact that ford tanked it from the factory. they easily could've made that engine do what the coyotes do now. stock that is. they take up a lot of room, but i like the ford cammers. a LOT.

 i almost missed the 4.10 gear......don't do it. you'll regret it the first time on the highway. you can drop a 3.73 in there, which'll wake her up a LOT off the line, but you'll still have decent top end for those euro-cars.

[Widewing]

Autobahn flier?

[Rich46yo]

Nice ride Rich.  I don't have to tell you what that '66 Stang is worth now.

I really want a '67 fastback to restore.  I like a '68 too.  The '69s were nice but they started to get a bit bloated

I know. It makes me want to cry. Girls absolutely loved that car. I'll never forget that blue and white vinyl interior with the ponies on it. And it was a quick little son of a gun, being light with a great little engine it it. I had a '67 Fairlane too with the same .289, same paint, I drove it back cross country after I finished my USAF time. Damn nice little car.

I think the '66s and '68s were the best looking early stangs. A buddy had a "Bullit" fastback, exact same color, and another buddy had a regular '68. http://themustangsource.com/timeline/67-68/68/bullitt/

[Hajo]

I think going from a 3.31:1 to 4.11:1 is not a good idea for Autobahn bashing.  A good compromise would be a 3.5x:1, if you could also attach a 6 speed to it.  That should effectively get you off the line better, through the mid range faster and still not compromise the top end.

I am dropping a 3.73 in my Cobra backed with the tall 6 speed Tremec.  The Cobra top speed is not limited by horsepower, just the design itself.  It likes to lift the rear end at over 180MPH.

3.92 rear end in  mine matched with a tremec 6060 6 speed.  My SRT got 25.6 mpg traveling to Virginia last fall and my SRT only had 1500 miles on it beginning the trip.

The newer Chargers and Challengers are making more HP per cu. in then did the old ones made in the 60s and early 70s.  They are also quicker in the quarter mile with air, cruise etc.
that come with them not to mention heavier.  The newer ones also handle much better then the old ones did.  And they actually stop now!  I know.  I owned and drove them starting in 1965.
Dodge engineering is top notch.  Every time I take mine to a show or cruise....first question "have a HEMI in it?"  HEMI says it all.  Not many sit around the campfire with a group
of old car guys and talk about the legendary coyote do they.  They all are nice.   I've owned them all from Z28 Camaros to TransAMs.  Roadrunner etc.  Raced 426 HEMIs also back
in the day.  They were great when you had the throttle to the wall.  But loaded up and stalled oft times when stopped.  440 clearly imho best road power plant for a MOPAR then.
Track.....HEMI all day.  If you've noticed that still is true today.

[Stampf]

They were great when you had the throttle to the wall.  But loaded up and stalled oft times when stopped.  440 clearly imho best road power plant for a MOPAR then.
Track.....HEMI all day.  Why you think that many FORD and Chevy guys went MOPAR then.  They wanted to win.  Super Stock and FX was where the fun was then.

Gospel.

If you ordered a Hemi...your warranty ended at the firewall.

440 was the street choice for the big 4 Mopars.

[Skuzzy]

No doubt the newer engines, from any company, are going to be more fuel efficient.  Fuel injection made a lot of that possible.

That said, I do know some 550HP+ Cobra owners who get over 25MPG in their cars.  They are fuel injected with electronic ignition systems.  Lots of good stuff available, for those old engines, to make them far more efficient than they were in the 60's.

I loved my Road Runner.  Sweetest sounding car I have ever owned.  Those engines were just right.  Heck, my Road Runner got over 20MPG with the six pack setup and would still win at the track.

[Stampf]

I loved my Road Runner.

If I had a dollar for everytime I have said that over the years, Roy...

...I'd be building a Cobra too.