USA1C5

Anybody got any numbers on how much downforce a stock Z06 makes. Lbs. down on front and rear at a given speed. Lbs. down on a whole range of speeds would be nice to know. Anybody got any numbers?

camarodoctor

A stock Z06 makes no downforce at either end, just some slight lift reduction with the factory aero, biased toward the rear, of course.

However, any net downforce or lift always come at the expense of drag. There is no such thing as a free lunch...

USA1C5

O.K. in other words, when the car is sitting still the amount of weight put on the ground is exactly the same as when moving through the air at say 198 mph, both front and rear. I would think there would be some difference in weight put to the ground, however so slight a difference. I understand the downforce/drag thing. The car does have some drag.

camarodoctor

At 198 mph, both the front and rear exhibit significant lift. GM published some aero data at 300 kph (186 mph) showing a slight lift reduction from the uber-lift associated with the base C6 at the same speed.

However, GM did not publish actual lift numbers, just percentages of lift reduction and comparable front-to-rear ratios (demonstrating the safety of having the front end lift more than the rear, making the car stable in a high speed turn, rather than having the rear end wash out unexpectedly).

I have the SAE paper around my office somewhere. I'll see if I can find any data for you...

EDIT
I found the paper. According to the results, at 300 kph, the C6 Z06 exhibited a total lift reduction of 138 kg for the whole car. The aero devices on the C6 Z06 exhibited over 607.5 kg less lift than a C5 Z06 at 300 kph. Overall, the lift of the C6 Z06 is reduced a slight amount versus no aero effects, but overall, GM gives no information on the total lift to begin with. An Enzo and an F430, for example, have actual net downforce above 300 kph. The best top speed for any car would be achieved with no net lift or downforce. The Ferraris have downforce, the C6 Z06 has lift.

USA1C5

O.K. thanks. It just seems to me if I could increase downforce/increase drag/reduce lift by putting on a bigger rear spoiler (maybe a rear wing) or a front splitter why wouldn't removing stock rear spoiler or going smaller or removing front splitter or going smaller decrease downforce/decrease drag/increase lift. Any data would be interesting to see. Thanks.

camarodoctor

Removing the front splitter will decrease drag slightly and add about 92 kg (upward) of front lift at 300 kph. Removing the rear spoiler will decrease drag and add about 36 kg (upward) of rear lift at the same speed. The important thing to remember is balance. If you add a front aftermarket spoiler lip, you will significantly decrease front lift, but if you leave the rear the same, your car will lose the understeer safety that GM designed into the vehicle's aero and could potentially spin out in a high speed turn when the rear end breaks loose due to aero lift overcoming available traction.

Due to the better aero design of the C6 Z06, the engineers at GM were able to remove significantly more lift compared with the C5 Z06 (over 600 kg less lift at 300 kph) whilst maintaining the same approximate drag coefficient (Cd = 0.342). (Of course, the C5 Z06 is a little better streamlined overall with the same Cd due to the slightly smaller frontal area versus the C6 Z06, where C5 Z06 CdA < C6 Z06 CdA). The real evidence that GM has a great aero design with the C6 Z06 is the increased air flow to front radiator and vented brakes with the same Cd as the C5 Z06.

If you add a large front spoiler lip, I would recommend adding a full width rear spoiler to counter the difference. This balance is seen on the new ZR1 and has been wind tunnel tested by at least one forum vendor (MTI Racing in GA) on some of their aero packages.

USA1C5

O.K. thanks again for all the good data. Interesting stuff.
What I'm having a problem understanding is the difference between reducing lift and adding downforce. If my splitter and rear spoiler are reducing lift why is that not the same thing as adding downforce? One would think even the windshield would create downforce. If I stick my hand out the window at the correct angle, I can create downforce or would you say reduce lift?

Onerareviper

Extensive wind tunnel test shows the '08 Viper ACR produces 1,000 pounds of downforce at 150 MPH.

linutux

If you put a C6Z on scales in a wind tunnel and simulated 300kph, the car would weigh LESS than at 0kph. The aero components(splitter, spoiler) do not generate enough 'downforce' to fully counter the cars natural lift. They simply reduce the lift.

To negate ALL the lift and generate effective downforce, thus making the car weigh MORE at 300kph, you'd probably need a louvered/vented hood like the WC hood AND a well designed undertray, plus a reworked splitter and spoiler.

Does anyone make undertray components for the C6Z?

LTC Z06

See the FAQ for the facts.

John Shiels

reducing lift and reducing downforce is the same

John Shiels

where did that data come from? thanks

John Shiels

usually but not always from what I have read

USA1C5

Do you mean reducing lift and adding downforce is the same thing. If you add downforce arn't you reducing lift or if you reduce downforce you add lift?

LTC Z06

Did you see the FAQ?

John Shiels

yes to both

USA1C5

Yes, Thanks. My problem was seeing the difference in reducing lift and adding downforce, they seem to be similar to me.

USA1C5

LTC Z06

Engineers make a distinction between lift reduction and downforce. Lift reduction is anything (splitters, spoilers, undertrays) that fight the air that goes under the car trying to lift it up; downforce is created by inverted wings that produce negative or reverse lift to keep the car on the ground.

John Shiels

books I have read say same thing I'll grab the title later. But I can see where some may say that. Really no difference to me anyway they all create downforce.