By moving the parting line...
By moving the parting line to the bottom of the bumper cover like on this C5, more air is forced up and over the car, decreasing both lift and drag.
Aerodynamically, the C3 we tested, a '70 model owned by Robert Morgan, doesn't differ much from the C2 split window. In fact, with the headlights up, it actually produces more drag (9.09 to 9.73 CDA). The addition of the tiniest rear spoiler, however, did help produce 13.9 pounds of downforce in the rear (shown as negative lift on the chart). This is the only car that was able to produce negative lift numbers.
Generation Four
The beginning of the "modern era" Corvettes began with the C4 (1984-1996). Fuel injection standard, electronic displays in the dash, the now-famous wedge body design-you name it. The '84 model marked the first complete redesign of the Corvette since 1968, and it showed. Just about everything on this car is an improvement over the previous generation, and that includes the aerodynamic performance.
Incidentally, the '90 C4 owned by John Walton is the ZR1 model outfitted with the four cam/32-valve LT5 engine producing 375 hp. Although the body differs from the base model, the overall effect in the wind tunnel should be minimal. The ZR1 C4, however, improved the CDA over the previous generation drastically. The numbers come in at 7.46 for the C4 versus 8.81 with no passengers and the headlights down. And where the C3 increased the CDA by 1.04 just by flipping up the headlights, the C4 only increases by 0.61. Total lift is also nearly cut in half. The C4 cuts the C3's 136.2 pounds of lift all the way down to 69.3.
By moving the parting line...
By moving the parting line to the bottom of the bumper cover like on this C5, more air is forced up and over the car, decreasing both lift and drag.
Generation Five
Finally, we reach the C5, a generation new enough that some purchasers are still making payments. Produced from 1997 until 2004, the C5 is again a tremendous improvement over the previous generation. Its introduction also marked the debut of the LS1 engine, which has become a favorite of hot rodders everywhere not only for the power it produces, but also for its light weight thanks to all aluminum construction. The C5 not only lost weight versus the C4, it was also better positioned thanks to relocating the transmission back to just in front of the rear axle.
For the C5, we tested two different models. The first was a standard-edition Vette owned by Mark Connolly. The second was a Z06 owned by Tommy Megremis. Surprisingly, the baseline Corvette produced better aero numbers both in terms of drag and lift. Because it has a greater frontal area, the C5 Z06 actually has slightly more drag than a C4 Corvette. Much of this apparently comes from the Z06's redesigned nose. It contributed to more aero lift on the front end versus the standard model, while the Z06 had considerably less lift at the rear end.
Even though side mirrors can...
Even though side mirrors can be made to minimize drag by making them a bullet shape, they still cause significant turbulence in the area directly behind the mirror.
"As a general rule, the base model of any car will have less aerodynamic drag," Eaker says of the surprising differences. "That's because the designer's higher priority is maximizing fuel mileage by reducing wind resistance. Option, or sport, models usually suffer a bit of a drag penalty because they're outfitted with body moldings that give them the look of a race or sports car. What they don't tell you is the look usually outweighs the actual effectiveness of the body changes."
Generation Six
At last, we've made it to the present in our little field trip through Corvette history. Eaker says of the C6, "Here, we're getting to a car with much fewer compromises. In the '60s, the main design criteria was simply to make a car that was fun. In the '70s, they added all the social responsibility that we talked about earlier, and the fun factor really suffered. In the '80s, the technology began catching up, and now we've finally gotten to a stage where the car can be socially responsible with good safety features and respectable gas mileage, and also more fun than any of its predecessors."