Have you ever noticed on NASCAR...
Have you ever noticed on NASCAR Sprint Cup cars the sharp edge where the rear quarter-panel meets the back of the car? That's a trick that has been used for years in racing to help the air flowing down the side of the car to separate cleanly from the body with a minimum of turbulence. Corvette designers used the same concept here.
The C6 is also the first Corvette since the C1 not to have hide-away headlamps. That cut down on our number of tests, but we made up for it by throwing in two cars once again. This time we decided to test a convertible (also owned by John Walton) against a hardtop (owned by Jimmy Kontoulas). As you might expect, the ragtop fared worse in the comparison. CDA for the convertible came in at 7.41 with passengers, compared to the hardtop's 6.99, but it still did better than the C5's 7.70 with the headlights up. The most interesting part of the comparison came when we compared the lift numbers. Although slight, the convertible actually turned in lower lift numbers. When comparing the hardtop C5 to the hardtop C6, the C5 actually has better drag numbers until you put the headlamps up, and then the C6-with its clear lens covers-wins. It turns out that the C6's "homage" to the original Corvette not only looks good but adds performance, too.
Know Your Codes
In the chart, we listed both CD and CDA, and unless you're a professional aerodynamicist or just really good at Jeopardy-type trivia, the difference is probably a bit confusing. CD stands for "coefficient of drag" and is a measurement of how much drag a particular shape produces regardless of size. CDA stands for "coefficient of drag area," and is simply the CD multiplied by the frontal area of the vehicle. Theoretically, a C6 Corvette and a Matchbox-sized scale replica should have the same CD. CDA is a better real-world number because size does come into play when we are talking about drag in terms of how much horsepower is required to reach 100 mph. So even though one car may have a slightly worse CD than another, it can actually be more aerodynamically efficient if it's smaller and has a better CDA.
The convertible C6 did have...
The convertible C6 did have aero disadvantages compared to the hardtop C6, but it may not all be blamed on the cloth top, which fits snugly to the windshield and is relatively smooth. One culprit may be the sharply sloped rear glass.
Notice how the headlamps on...
Notice how the headlamps on this convertible C6 cause no disruption at all to airflow. Also, one of the big aero advantages with modern automobiles is flush-mounted glass, which provides no harsh transitions to create turbulence in the air.
Now compare the flow on the...
Now compare the flow on the hardtop C6 with the fastback glass. It doesn't require a trained eye to see that the flow of air is much cleaner.
The wide haunches of the Corvette's...
The wide haunches of the Corvette's rear quarters create a type of "shelf" that helps keep the air flowing around the side windows on top of the car and guided toward the rear deck, which helps create a bit of downforce.
Coefficient Of Drag Basel...
Coefficient Of Drag Baselines
Coefficient Of Drag Area ...
Coefficient Of Drag Area Baselines