I have a question that has been bugging me for a while now.
As far as i know the difference in aerodynamics between C5 and Z06 lies in the back of the car - the back window that area... right?
If this is right and C5 has a better aerodynamics, why when i look at the pics of C5R racecar i see the back very similar to Z06 back, it seems to be sort of in the middle, not that short as Z06, but not as long as C5?
Am i missing something? I would assume C5R should have the best aerodynamics ever from all corvettes.
The rear aerodynamics of the C5 Coupe are better than the Z06. The reason is the rear hatchback of the C5 Coupe. The hatchback glass allows a better non turbulent flow and less drag. This will produce about 5 MPH more on the top end. But it is ONLY significant in the wind tunnel.
Here's why: there is a trade off.
1. The hatchback glass is massive and heavy.
2. In addition the Z06 (at least on the '01) glass is thinner still
and therefore even lighter than the FRC glass.
3. With the Z06's supierior power, torque and acceleration due to the closer ratios in the box; the Z06 is quicker in almost every instance.
4. The aerodynamic effect of the hatchback glass is only advantageous above 150 MPH.
So the Z06 will get to and be around the next corner before the C5 Coupe gets there. There are only 2 places where the hatchback glass would render the C5 Coupe superior in top end speed and that would be at Bonneville and on the Mulsanne Straight at LeMans....if it had time to overcome the Z06's faster acceleration.
The C5R uses light weight and strong Lexan for the back glass...and you are right in that it is somewhat shorter glass than the C5 coupe. But it has to be. It sets up the air flow for the C5R rear wing. Besides the whole body of the C5R is totally different than a production car. Therefore the C5R's aerodynamics are derived differently than the production cars. It also has a front splitter, hood louvers, a wider body, wider gill vents and undertray in the rear and a complete carbon fiber lightweight body.
The wing rules and specs have to conform to a certain size "box" located within a specified distace of the rear fascia. Pratt & Miller also chose to develop the wing in an "all inclusive box". ie. They took all the different wing rules from all the different sanctioning bodies and made a "box" to conform to everyone's rules. This was done to balance the car and set up using only 1 aerodynamic envelope....That way the drivers only had to deal with 1 set of handling parameters; development and tuning is much easier....only having to deal with changing tracks rather than different wings, tracks and different aerodynamics.
Using the same (longer) planiform as the C5 Coupe hatchback glass would necessitate moving the wing further back to make it effective....but placing it's location too far back to meet most sanctioning body specifications. .....Remember the "Long Tail" Porsches?
You can even see the shaping of the C5R wing's leading edge to conform to the laminar flow off the "semi - hatchback" glass. The current '04 C5R wing has been further developed to have more curvature and downforce and like previous ones is tunable in adjustment and by the addition of airfoils (wickerbills).
That was some great insight DJ Worm but I don't think the coupe is faster than the zo6 at top speed, here's why:
1. Although the coupe does have an aerodynamic advantage over the z06 with the lower Cd, .29 to .31, the z06's additional power outweights the aero advantage of the coupe.
For example, the equation used to calculate power needed to propel a car at a certain speed is:
Power=Cd*air density*car frontal area*speed^3. If we solve for speed we can find out which car would go faster!
The two variables we are dealing with are Cd and Power.
Zo6: Cd .31 & Power 405hp
Coupe: Cd .29 & Power 350hp
Solving the equation for speed is (2*Power/(Cd*Dens*Area))^.33
This leaves the coupe at a top speed of 187 and the zo6 at 192, a good 5 mph ahead of the coupe. Now granted these are theoretical speeds and are higher than in real life. The reason for this is road friction, which will knock both cars down about 15 mph (172 and 177).
2. The real reason I don't think the coupe is faster is because in high speed testing the z06 has been the faster car. I've seen a coupe do 170, I've seen a z06 due 175 under test conditions.
Although I was lazy and left out some calcs including redline considerations these are two reasons why the z06 is faster than the coupe.
2
AND...the thing that disturbs me most is that neither of you, and you in particular DJWorm, failed to include in your dissertations and calculations the inherent advantages and functionalisms of the BSM. Shame on you two!
That's crazy. My wife's G35 Coupe is more aerodynamic (.29 Cd -- .28 with the aero package that we didn't opt for) than my Z06. By looking at both of them in the garage, you'd think that the Z06 would have the edge too because it sits so much lower.
being lower is only one part of being more aero. the Z has a much greater frontal area than the G. the Z is also wider and longer with larger tires. many cars especially 4 door sedans are often much more aero than pure sports cars. .29 is one of, if not the lowest cd's of any sports car!!
Originally posted by camshaft I've wondered, but never bothered to ask, why did they change the back for the Z06 rather than have the glass slope all the way back?
Austin
In a word, RIGIDITY. The FRC is a much "stiffer" platform than the coupe. Remember, the Z06 was primarily built with racing in mind.
Originally posted by camshaft I've wondered, but never bothered to ask, why did they change the back for the Z06 rather than have the glass slope all the way back?
Austin
They didn't change it. The Z06 is based on the C5 fixed roof coupe (FRC). The reason they did this is due to the fact the FRC affords a stiffer chassis and is also lighter. The coupes rear hatchback glass adds to the weight although it is slightly more aerodynamic.
They chose the FRC to market to the "extreme performance enthusiast" segment and by using the FRC with its above attributes in addition to the LS6, even more weight reduction, suspension tweaks and renaming it Z06, they were able to increase sales; which for the two years the FRC design was available prior to the Z06 it was not selling as well as the coupe or vert models.
In a word, RIGIDITY. The FRC is a much "stiffer" platform than the coupe. Remember, the Z06 was primarily built with racing in mind.
That explains why they didn't put the pass throughs on the seat backs so you can run harness belts through them like on the Coupe.
Seriously, the hard top is more rigid and lighter than the coupe. Plus, it looks a ton better IMO. I haven't liked the Corvette for a long time until they came out with the FRC and the Z06.
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