LSOHOLIC

I've been considering doing some standing mile events. And the events like the Spectre 341 Challenge really interest me. I own a C5Z that puts (NA)450ish to the tire. My question is about the aero mods needed. Aero-dynamically speaking, at what point (MPH) will I need to start looking into this?? Of course my HP will only increse in the future so I'm looking to grow into the mods. My question is about splitters, rear diffusers, heat extracting hoods, spoiler/wings and all the stuff I've still yet to learn about. I've got the car pretty light and I think that would be an advantage over some of the competition. Basically what are the limits of the stock body C5Z?? Thanks in advance..

AU N EGL

Aero mods only slow you down, and provided better or more down force for high speed corners. for straight speed the less aero may be better.

Setting up the proper rake on you car may be more important for a 1 mile run.

Do a google search for aerodynamics.

There is a great SAE research study on the C5 aerodynamics.

Jason

Tape your seams, shave your mirrors and radio mount. De-badge and fill in the holes. Good coat of wax.

John Shiels

With the Spectre 341 event wings may be more appropriate. I would guess 60-70 down-force starts kicking in. Do I feel it at that speed, doubtful. As Tom said you can buy the SAE C5 papers.

geerookie

Get this. It was done for the SCCA. $15 and it will show you the facts about C5 aero. It also shows you what you can do and what kind of penalty you may pay in drag.
For instance, the C5 has lift on the nose in stock form. The faster you go the lighter it gets and as John said it starts around 60mph.

AU N EGL

Here you go

http://papers.sae.org/2002-01-3333/

Paper Number: 2002-01-3333
DOI: 10.4271/2002-01-3333

Author(s):

Larry Kubes - General Motors Corp.
Jim Spaulding - General Motors Corp.
Dwight Woodbridge - General Motors Corp.

Abstract

This pager 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 this 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 2.5cm rear and 5.0cm front reduced drag by 326 N (73 tb.) 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.

Last C5

Thanks! Great paper to have, however it doesn't say anything about the extractor hoods. Do you know of any studies or available information regarding the extractor hood? I'm assuming they're not just for show and shine as the factory teams use them.

AU N EGL

http://www.corvetteracebodies.com/corvetteracebod.htm

watch this video

http://www.corvetteracebodies.com/wi...2-06%20012.mpg

C6 World Challenge Hood in Carbon Fiber

davidfarmer

For a standing straight line, just tape the seems, seal the brake light openings, and go. You don't want downforce or drag. If you cam make a mike with less cooling, decrease the radiator opening

John Shiels

341 he is running or wanting to is far from straight. I agree straight line just go! Taping the seams will help.


Few years back LPE have a vid at 200 mph and you could see the hood lifting way up I mean a lot! Putting vents will take the pressure off the hood but also create drag.

briannutter1

I was on the winning team for the 2007 Maxton Mile Hot Rod event and we spent a day in the a2 windtunnel prior. Corvette Fever or Vette magazine did a GREAT test at the A2 tunnel that you can google results on to see real numbers for c1-c6 cars.

You will not need "downforce" in the back, but anti-lift at the front. Running the car at a pronounced rake from front to rear can reduce front lift and drag to some extent as it closes off the air that would be hitting the "ugly" underside of the car. Beware some tracks can be bumpy and hitting one at speed with minimized shock travel will wipe you out if you go too low.

Your best bet is a pro stock style spoiler that is adjustable, but run nearly flat. This doesn't add frontal area, adds a bit more surface area to the back deck to re-attach ariflow that comes off the canopy, but most importantly extends the wake further behind the car. It's critical as the rear wake CAN and DOES move up underneath on most cars...which can make cow-catchers and side plates actually INCREASE lift by packing/trapping more air under the car. I would have never believed that until I saw it with my own eyes. Make the sheetmetal spoiler the absolutely Longest (front to back) allowed by the rules...I remember about 10" or so off hand. Side skirts will "Probably" help if you've done the rear pro stock wing.

Airdams are a good thing if the underside of your car is really ugly. ours aren't terrible. Spend some time fairing/smoothing in behind the airdamn to the front frame underneath the car might be worth a very small amount

Do the same in the back by the rear axle and rear facia. What goes on BEHIND the car is several more times important that what happens in the front. 7 to 14 degrees of rake angle is a general zone to reduce flow seperation (drag vortices). If you look at the "frontal" silouette underneath the rear of the car, this would give you a good chance of making an undertray/diffuser that's functional. Extending this tray outwards by the same amount the pro stock wing does will help as well. Effectively lengthing the car.

Side mirrors off. Taping up seams did nothing for us unless it was to seal off radiators or ducts that were placed in bad areas. Speaking of which, hood ducts behind the front wheel arch center are usually a bad thing because of the high pressure zone in front of the windshield. The front bumper area is a high pressure zone as well. There is a sweetspot on corvette hoods in front of the wheelarch center, but behind the bumper molding that has fast airspeed over the top (effectively suction) that might bleed some high pressure out from under the hood. a wickerbill would be helpful above these vents It's VERY touchy to find the area without a windtunnel, you may do more harm than good. Look at the c4 Callaway sledgehammer as an example.

A small wickerbill at the front leading arc of each wheel well that doesn't extend out further than the tire's siloutte may reduce a bit of lift without adding frontal area. Running narrow tires will help more than they hurt at the launch.

The air coming off the short rear window of a c5z tumbles down onto the back deck. You may want to try some turbulators like the evo 8's have. "Airtabs" is a brand that may work as well and used on semi-trucks, but have a completely different design to achieve the same thing.. This might be something worthy of a string test coming off the rear window.

If you have $2k or so to spend in the A2 tunnel, it will be the best day (or half day) of your life. Just make to go in with things "modular" and adjustable so you can easily test a number of configurations with each "pull".

your 5th gear is good for 172 at 6500. Likely your powerpeak is about the same..which is good for the standing mile. With your power curve, determine if you're going to loose a lot of power at 7k rpm/184-ish mph as it can become the "end of the line" for valvesprings and hydraulic rollers. A custom 6th gear ratio from Liberty isn't god-awful expensive and it can align your 200mph target with your engines hp peak. You will need more power to do that in the standing mile, but you might achieve it with perfect gearing on an open road with 450whp and the aeromods listed above.

Sorry to write a book. it's a little disjointed and time for me to go to bed.

AU N EGL

good stuff Brian

any pics of your Maxton mile ride ?

LSOHOLIC

Thanks a bunch. This is some great info. So for a road course situation the down force would be needed more in the turns ?? But at what speed is the downforce utilized ?? I have yet to read the SAE paper but I'm doing going to tonight.

AU N EGL

Even with my front 2" splitter and 1" rear spoiler, it makes a difference at speeds from 50 mph and up.

also noticed lower top speeds with the added air resistance.

Rake was the or is the biggest factor in aero performance.

Jason

New favorite thread.

AU N EGL

Guess car this is ??

drivinhard

sperkins TTA car

AU N EGL

Yah like the Tech inspectors are blind . ..

Aaron Pfadts ST1 car

John Shiels

how fr forward does it go?

drivinhard

no points mod in PT/TT is an undertray up to the front axles.

the skirts (stock) pretty much lay over at speed in a C5, I'm having a hard time finding what advantage you could get with an undertray from the nose back to the front axles. with the leafs, you'd only be able to have it at the center (in front of the leafs)

no illusion we could create any amount of downforce with it, but just keeping air out from under the nose would be nice.

also with an airbox, (+1) you can also vent hoods/fenders, etc under that same point. (something I am not doing)

TM says 117 mph coming off T12 at RA, @ 117 mph there's gotta be some aero we can take SOME advantage of. same for the VIR esses.