Coefficient of drag for Callaway Corvettes

[Brangeta]

I found this interesting website that has the coefficient of drag for the Callaway Corvettes as well as several other Chevys. I don't know the reliability of the data here, but based on what I mentally think of the aerodynamics of the cars listed... I'll say I believe it.
http://www.mayfco.com/chevy.htm
Anyone know what the other calculations are? I'm not a physics/engineering guy. :confused

 

[Aurora40]

I would have to say no way a C4 with an aerobody has a .26 Cd. The top half of the car is unchanged, as is the underbody. I would think any improvement would be small, I thought the main thing the aerobody did was provide some downforce for high-speed stability (well that and look cool).

The other measure is just the frontal area in either meters squared or feet squared. The aerodynamic profile is Cd multiplied by frontal area. So for example a car with a worse Cd can have the same aerodynamic drag as a larger car with a lower Cd. The C4 had a rather average (maybe on the low side for the time) Cd, but of course it has a very small frontal area, and thus could go pretty fast even with the relatively low powered Crossfire motor.

So for a given Cd X frontal area, it takes a certain amount of horsepower to go a certain speed. The right gearing makes a real-world difference too because it's how much power you are making at whatever rpm you are stuck at at top speed, not how much power your motor can put down at its peak RPM (i.e. you want to gear it so it's at the power peak when you hit that peak speed)

 

[CallawayC8]

I don't really remember what the numbers were, just that the Aerobody vastly improved them. The main problem with the C4 was the lower body section. The trend in the late 80's was to diminish the side profile by wrapping the lower body under the beltline. This made it look slim, and made the tires look huge, as they "poked out" from out of the car. This is the number one detail that kills the aerodynamics of the car.

The Aerobody essentially fixed all of the lower body drag by fairing in the wheels, and providing a smooth flow of air from the front facia to the rear facia. It did, however, make the side profile look heavyer, as you saw the entire side of the car now, as opposed to it wrapping down and reflecting shadow into the side.

I hope this helps,
Anthony

 

[*89x2*]

...I heard the Chevy stylists were fans of the AeroBody too -

...and if you look closely at the C5's nose, you will see cues from the Callaway AeroBody styled into it :W

...the way the corner lamps wrap around and the openings, show they enjoyed the style Callaway had

 

[Brangeta]

Interesting. I remember going to a lecture last year sponsored by Toyota that said the Toyota Prius had a lower coefficient of drag than a C4 or an Acura NSX. Nuts huh? ;squint:

 

[Aurora40]

Interesting. I remember going to a lecture last year sponsored by Toyota that said the Toyota Prius had a lower coefficient of drag than a C4 or an Acura NSX. Nuts huh? ;squint:

The GM EV1 had a Cd of .195, the lowest of any production car in history I believe.

...and if you look closely at the C5's nose, you will see cues from the Callaway AeroBody styled into it :W

Also if you look closely at the C5's development, they spend considerable time on the aerodynamics, and only achieved a .29 Cd. I just can't believe Callaway could put a lower body kit on a C4 and knock the Cd from .32 down to .26.

 

[redb2k's]

Aerobody

The Aerobody added at least 5 mph to the top speed, So it must really help.

 

[CallawayC8]

Remember guys that the C4 was a considerably smaller car than the C5, with a smaller frontal area, so cleaning up the lower body will really help its drag. Also, factors like wide wheels KILL aero, so its not that amazing that a Prius will show good numbers. If you put skinny wheels and tires on either Vette, it will show some impressive numbers. I think if you read any literature on C4 or C5 aero traits, they always note that the numbers were achieved, to their amazement, with wide tires.

Anthony

 

[*89x2*]

Remember guys that the C4 was a considerably smaller car than the C5, with a smaller frontal area, so cleaning up the lower body will really help its drag. Also, factors like wide wheels KILL aero, so its not that amazing that a Prius will show good numbers. If you put skinny wheels and tires on either Vette, it will show some impressive numbers. I think if you read any literature on C4 or C5 aero traits, they always note that the numbers were achieved, to their amazement, with wide tires.

Anthony

Anthony, not just a smaller frontal area, but it did not have that wide-butt of a C5

For the same reason a ZR1 will be slower than an LT5 in a base Corvette, size does matter when punching a hole in the atmosphere hnoes

 

[Aurora40]

Remember guys that the C4 was a considerably smaller car than the C5, with a smaller frontal area, so cleaning up the lower body will really help its drag.

The Cd though is not related to the size. You could scale up a C4 (or anything) to double the dimensions and it would have the same Cd. The actual drag would of course be more.

And absolutely the wide tires have a penalty. Though the aero car has the same tires. I certainly don't have proof the aerobody doesn't have a Cd of .26, so if anyone wants to believe that, feel free.

I'd think a change like that would have a pretty noticeable impact on highway fuel economy and on top speed.

 

[Aurora40]

Anthony, not just a smaller frontal area, but it did not have that wide-butt of a C5

LOL! The rarely discussed but still important rearal area.

 

[Brangeta]

Whatdya think the Cd of this car is?

:L

 

[redb2k's]

Whatdya think the Cd of this car is?

:L

I think with a different engine/driveline setup and longer wings it would fly.

 

[CallawayC8]

While it may be somewhat slippery, it has several flaws. The high ridgeline at the base of the windshield will cause turbulence that will continue down the entire surface. Once airflow is disturbed, it is very difficult to get it to re-attach to the surface. Vortex generators ahead of the suspect area would help.

Also, the catwalks that extend to the rear wheels will cause a great deal of drag at the intersection. Whenever you have two different boundary layers that are creating drag, (one being the body/fuselage, and the other the catwalk) they will cause a dramatic amount of drag at the intersection. This is why old WW2 fighter planes (subsonic) have huge fillets behind the wings. They effectively blend the wing surface into the fuselage surface so that the air only sees one surface.

It will of course, still have good aero due to its small frontal area, but it is not perfect. It looks very sleek, but the air knows better.

Oh yeah, the NACA duct will not pull air properly where it is located, due to boundary layer issue mentioned above...

A