I was thinking the same thing, maybe he was going downhill with a tailwind?

 

People shouldn't worry about the top speed, look at the Chrysler 300 SRT-8 it does over 170mph and it weighs 2 tons and definitely isn't aerodynamic. I agree on the Mustang comments about stability. My old GT would start to get squirrely around 130 and it probably couldn't go much faster anyway(97GT, don't laugh) it felt like air was getting under the backend and trying to lift it or something. My 02 Z28 never had that problem but I was too scared to try and run aver 140mph because of the cops around here.

 

Think about an airplane with a long pointed nose. The frontal area is small. Now chop the nose off about 5 feet back and now its flat instead of pointed. It presents more frontal area for air to effect. The same with a car. With a car, there are ways to channel the air so that it does not make that much of an impact.

 

I'm no engineer but that's not how frontal area is measured. Its just a footprint of the width and height....3D has nothing to do with it. Its obvious a curved pointed nose is more beneficial, but the issue is what is the definition of "frontal area".

Frontal area is a 2D cross section http://www.v8sho.com/SHO/FrontalAreaCalculationsCd.htm

 

4th gen CD was .33 - interestingly enough, so was the '03/04 Mustang, which I wouldn't have thought by the looks of it. C5 is .29 and C6 is .28, for comparison.

 

This is wrong.

Frontal area as he described it is correct.

It is the MAXIMUM 2D area seen from the front view as projected orthographically.

Frontal area DOES NOT describe the first surface that the object comes in contact with, but the entire area of air that the object must push out of the way - which is the 2D "shadow" he described.

Furthermore, aircraft have lifting surfaces and are much, MUCH faster, so the comparison sort of breaks down there some more. The most aerodynamically efficient shape for a car would be a tear drop, where the blunt end is facing the wind and the after run is long and gradual. Making it pointy is WORSE for a car than the teardrop shape.

And again, the front of the vehicle is never as important as the after run.

To use a double entendre where air is concerned:
It ain't the way you first poke her, it's the way you leave her when you're done.

 

For the Third Gen early Z28's were .36, IROC-Z's were .34, early TA's got .29, the last TA's got .31. The handling thing is no myth, but I wouldn't say they can do it easily.

 

Great thread. I like just sitting back and letting the experts on this chat. Learning quite a bit here.

The 3rd gen handling myth comes from GM taking out the harshness of the F-body's suspension when they did the 4th gen. Because the 4th gen rides smoother, feels much wider, and the steering picked up some weight to it's feel, the 3rd gen feels much snappier and quicker.

Put a stock version of both on the same course, and the 4th gen is actually better handling, though by comparison it doesn't feel like it.

My boxy '85 Special Service Mustang notchback topped out at 136 with just 210 horsepower. 145 with 70 more horses, and the same aerodynamics of the latter 4th gen Camaro sounds perfectly reasonable. But the USE of that wind makes you far more comfortable taking the Camaro to 140 than the Mustang.

On a sidenote (which I find facinating) my current '89 Supercoupe which has the same horsepower as my '85 Stang had & weighs about 600 pounds more tops out 10 mph faster. It also feels far more stable than even my Camaros around 140.

 

I never said that was correct, just that is why people worry about it. Frontal area is the outline of the car as it heads towards you. The air it displaces can be reduced by the shap of the front of the car. Thats why people assume blunt cars have trouble attaing higher speeds.

 

Nobody liked my solution? I thought it looked pretty snazzy for something made in MSpaint.

 

Yep, flow separation is a big component of drag. The longer you can keep flow attached to a body the less drag you will have. Its the same reason golf ***** have dimples. The dimples induce high energy turbulent flow which keeps the flow attached further back along the body and the energy lost due to inducing the turbulent flow is much less than what would be lost to air, hence the ball fly's farther.

I would be willing to bet that whatever the drag coefficient of the 5th gen is, you could probably drop it by 0.2 or so just be redesigning the back end so that there's both a smooth transition back to free stream and a favorable pressure gradient over the length. Looking at the cars profile it looks like there might be an adverse pressure gradient along the back window which could cause premature flow separation. Course doing this redesign would make it terribly ugly for a car.


Right again. People need to understand how drag force is calculated. D = 0.5*Cd*rho*S*V^2 where S is a reference area, rho is the air density and V is velocity. That reference area varies depending on the vehicle you're talking about and is usually the prevalent area. Airplanes use the wing planeform because its the dominant area whereas cars use frontal area.

Aircraft are a whole different ballgame. You have to start taking into account effects from tilted lift vectors, induced drag from vortexes from producing lift and a ton of other factors. Chopping an airplane off 5 feet from the nose will produce increased drag but not because it increased the frontal area. I would explain but it would take a lot more time than I have at the moment and its further complicated by the fact that after studying aerospace engineering for 5 years I still don't completely understand it.

 

The air displaced is fixed by frontal area, velocity and density. How EFFICIENTLY IT IS DISPLACED is represented by Cd. A better way to describe it might be "how little the air is disturbed during displacement" my old fluid dynamics prof used to describe this disturbance of the air as "making the fluid angry" (air is a fluid, btw...).

That's the whole point.

How much air I gotta move is the S (frontal area for a car) * V^2 (velocity squared) * rho (density).

How efficiently I displace it is Cd.

 

Oh I agree it's really close in stock form even if Thirds feel better. But if you evened it out and gave the Third a manual (and maybe an LS1) and the same wheels/tires as the 4th, it would be a sight to see.

 

I thought that was kind of odd because even the 32 valve Cobras weren't able to go 150 back then.

 

A word about limiters, there are Speed limiters and then there are RPM or rev limiters

I don't think there are speed limiters on the Z-rated 4th gen F-Bodies, but there are rev limiters, and rev limiters will keep you from going faster when you reach the upper limit of RPMs. For instance top speed on 6-speed cars is attained in 5th gear, and the top speed point is the point of which the rev limiter kicks in and safeguards the engine from destruction. LS1 have a much higher rev limiter than the ole LT1. Rev limits can be changed with a programmer. The talk of a 162 mph limter on stock LS1s is probably the rev limiter in 5th gear.

Speed limiters are set at a certain speed, usually the speed rating of the factory tires. My old Caprice LT1 had a speed limiter set at 108 mph, and didn't take long to hit it if you kicked down on it on the interstate. After I reprogrammed it I ran into another problem at WOT the transmission would not shift out of 3rd gear so it would hit the rev limiter at 128-129 mph. To go faster I would have to let off half way let it shift into 4th then get back on the gas.

You can really tell/feel the difference in a speed limiter vs.rev limiter. A speed limiter when you reach that terminal speed kills the gas for several seconds, until the car has slowed by at least 5 mph then resumes gas.
A rev limiter when hit is very fast off and on again with the gas. Some of you may have heard people hit the rev limiter at the drag strip doing burn outs, the same goes for top speed runs if you get the RPMs high enough.