C6400hp

I believe it was KB aero biscuit that said it.
in this thread here.
http://forums.corvetteforum.com/auto...-please-4.html


tell me why he is wrong.

AU N EGL

Here is the link to the SAE paper on C5 aerodynamics I posted a few times
http://www.sae.org/servlets/productD...D=2002-01-3333

"Abstract:
This paper documents a one shift (10 hour) wind tunnel test program conducted on a Corvette C5 prepared for Sports Car Club of America (S.C.C.A.) World Challenge racing. The testing was conducted at the Canadian National Research Center in Ottawa, Canada. Specific areas of test included front fascia and under tray, rear air discharge, rear wing configuration and angle, B-pillar configuration, and ride height. Standard wind tunnel test procedures were followed. In total twenty-six separate configurations were evaluated. Data for front and rear lift, total drag, and lift/drag (L/D) ratio are provided for each test configuration. The cumulative effects of the aerodynamic changes evaluated in his program, calculated at 192 KPH (120 MPH), increased front down force by 318 N (72 Lb.), and rear down force by 770 N (173 Lb.). Lift/drag ratio was improved from -0.597 to -1.016. These changes increased total drag by 381 N (86 Lb.). Further testing lowering ride height 2.5 cm rear and 5.0 cm front reduced drag by 326 N (73 Lb.) and resulted in a L/D ratio of -1.247. Although data are specific to the Corvette C5, the general principles studied may be applied to any production-based racecar. These modifications should be validated on the racetrack prior to competing to ensure the handling balance can be optimized for the driver and car combination. "

Great $14.00 investment in your car

wtknght1

Mark Guisti at Phoenix uses a GM part numbered tool to measure the correct suspension angles and subsequent ride heights - both F and R.

LehmanZ06

IMO-----as long as the lower suspension control arms are not lower than parallel to the ground---THEN you are fine.

If lower than parallel then possible problems.

Note(I also have a slightly stiffer front spring to better control the front)

gkmccready

Parallel at static ride height, or at full compression?

gonzalezfj

DING!!! We have a winner!!!

That's exactly how my car ride height and rake were set up (although Mark didn't do it personally).

Can't beat proper tools and engineering support.

Frank Gonzalez

gonzalezfj

That thread is many pages long and I did not take the time to read all the posts. You asked for an explanation, here it is:

For maximum downforce and minimum drag, the high pressure air needs to go on top of the car, not below it. High pressure air below the car (applied to the entire area under the car) creates lift, a highly undesirable situation at high speeds.

In addition to creating lift, the high pressure air creates drag because the bottom of the car is anything but smooth, what with all kinds of things protruding into the air path. The top of the car is smooth and shaped in the wind tunnel to minimize drag.

Many race cars use louvered hoods to extract high energy air from the engine compartment. Air comes in through the radiator and below the chin spoiler. If you can make some of it exit through the louvers (rather than run all the way to the rear under the car), you have reduced the amount of lift and drag.

There are also a number of techniques to help extract air and create downforce at the rear. These usually are based on the Bernoulli effect (increasing the air velocity lowers its pressure) and look like extractor (difusers) at the rear of the car. Look at many Ferraris and some MB cars. These are somewhat effective and help decrease lift at the rear of the car.

Hope this helps.

froggy47

I read the whole post, some pretty well tested & reasoned statements on why an air dam trim could be putting the whole package back to an OPTIMAL clearance. Especially what KB Aero Biscuit had to say. Think of it like a wing on an airplane/jet. There is still "some" air passing underneath.

drivinhard

Backing up to more of a 40,000 ft view (or question) here.

Is the biggest thing we are after is simply dropping the CG of the car?

Based on my (limited) experience, going way low and with (production car) suspension pieces and you are starting to introduce less than optimal geometry, bump steer, etc.

I'm not attacking either view BTW, I'm genuinely interested in a healthy discussion of such, as I've gotten a variety of viewpoints over the years.

fatbillybob

I'm sure this is true but tells us nothing. A ride height is a simple measurement from ground to a known referrence point front and rear. Suspension angles then become automatic within the tolerences of build variances. It is too bad no one can or will tell the numbers. Ride height is a good place to start but there are still a zillion other variables to a good handling car.

touring2

got mine back from a tuner at 4 3/4 inches all around. was 4.0 when I took it in. He went lower than I asked him to, based on earlier posts(thank you Subdriver, White Knight). handled better than before, no snap oversteer, or bottoming out. Still, looking for Phoenix's magic ride height per previous (old post)
Anybody? Anybody? Buhler? Buhler?

Dan H.

I had a track/street alignment done at County Corvette. They lowered it 8mm.

Bossdog

I am preparing my 2001 Z06 for track use this spring. This vehicle has been used for track use in the past but the seller partially de-tracked the car prior to sale.

The car has Pfadt Featherlight Coliovers. Street tires are on right now, 305/30/19 rear and 275/35/18 in the front. The current ride height as measured just in front of the front puck lift point is about 4.125, slightly higher on the drivers side. Rear measured just behind the rear puck lift point is 4.25", again just slightly higher on the drivesrs side.

I will be running 315/30/18 square for track set up.

My plan is to install the track tires and adjust ride height (same measuring points) to 5.5' front and 5.75 rear. Then take it to be corner balanced and aligned. The starting point is about .5" lower than stock.
Camber -1.5 to -1.6, toe -.06 front, -1.1 or so camber, +.05 toe rear.

Please weigh in on my plan, sound or flawed? for a car that is primarily track use but driven to the track.

Soloontario

Sure would love to know what the "magic" number for ride height is and at which spot, the jacking points or the centre of the control arm bolts.

I don't know where my car started out (bought it used and have messed with both ends since) so would love to go back to stock and start over.

BTW, I assume the "magic" ride height numbers are based on tires that are staggered like OE and that those of us using square setups either have to lower the front or raise the rear (or both ??). The obvious other issue is that using tires of non stock sizes changes things a lot (Nitto NT01 315s come to mind as they are quite a bit shorter than the stock C5Z rear. Sport cup 2s in 295 sizes are even shorter).

Bossdog, you will want more neg camber front and rear if you can get it, particularly for a 315 square setup. Without it, you will find some pretty uneven tire wear.

Nowanker

My $.02....
probably depends on the track.
Dead *** smooth/really bumpy?
Test, test, test.

l98tpi

As mentioned several years ago; corner balance the car then set your alignment- more neg camber in front and I assume you are going to toe out in the front? Make sure to toe in on the rear. Start there and adjust accordingly.