JerryTX

Anyone have pics on a C6 (or even a C5) of NASA legal mods to the fenders and liners? I'm ST2 now and have an eye on ST3 so I don't want to pick up the aero penalty for a big wing and large aftermarket splitter. I have a narrow body C6 (can't afford full widebody and wheels to go with) and I am in desperate need of more front end grip. I have a vented hood, Z06 nose, ZR1 splitter, and it helped some but not enough. I am adding an undertray this week which is also allowed. The pertinent part of the rules state:

I cut and pasted the pertinent part of the rules with regard to venting fenders and nose. Full rules are here:

http://www.nasaproracing.com/rules/Super-Touring.pdf

ST3 only The addition of non-OEM aerodynamic aides or modification of OEM body lines (unless specifically stated otherwise in these rules), will be assessed a Modification Factor to the “Adjusted Weight/Power Ratio”. In this case, non-OEM is defined as any part that does not come from the vehicle manufacturer either as a standard feature, a factory option, or on a factory optional trim model/package of that generation of the street-legal (in the U.S.A.) version of the vehicle.

A. Every vehicle must retain its unmodified:
1) OEM frame rails and/or Unibody, and Sub-frames
2) Strut towers
3) Inner/inboard side of the fender wells
4) Rocker panels
5) Transmission tunnel
6) Floor pan
7) Windshield frame location

The following are permitted exceptions:

Plastic fender liners may be modified and/or removed. The front, top, and rear aspects of the fender well may have modifications to allow vent holes for aero and/or cooling purposes

The following are additional permitted exceptions to above above:
1) Undertray/belly pan forward of the centerline of the front axle.
5) Hood replacement/modification for venting and/or weight reduction
6) Removal/cutting/drilling of the fascia for engine cooling, air intake, and brake ducting purposes.
10) Headlamp, headlight covers, and fog lights may all be removed. The holes may be left open, used for brake ducts, or must be covered with material that replicates the shape of the OEM light/cover, leaving the shape of the OEM fascia intact.

Thoughts or pics? I think I can cut slats in the top and rear of the fenders but I'm looking for ideas on how to execute this.

jimtway

Check out Run Cool Hood Louvers at Hoodlouvers.com. Link in my signature.

Solofast

I would leave the fender liners alone, while you can suck some air out of the top, there is more to be had by working with the front facia and front wheel well opening. The lowest pressure on the entire front of the car is at the front of the front wheel opening. You need to create some gap there but bulging out the opening and creating a gap that will allow this low pressure air to suck down the front end...

Think about bending the front facia out just ahead of the opening. The C6Z has a Gurney flap or small lip spoiler (like a half an inch wide) along that edge, it starts at about an inch wide and tapers up as you go up the fender. That will greatly increase the front end downforce and do a lot more than venting the top surface.

The key is getting enough area between the tire and the edge of the facia to let the low pressure area there do the work. Some slight massaging there and the lip spoiler/C6z part will go a long way to killing the front end lift.

Coupled with what you are already doing and have planned it should make a difference.

JerryTX

Good idea, but I don't know that I can do it, I'll look into it for the front:



What about for the rear? Looks like a huge opportunity to be a parachute!

spazegun2213

Honestly, you are just going to have to stick with what the corvette allows as far as aero. You can always try really taping up the front end to make sure you are not losing any of that pressure into the fog lights or anything like that.

But if you want more down force you are going to need that wing and front splitter. Why are you thinking ST3? I'd bet your car has plenty of power for st2, and aero will be much cheaper than the wide body (and give you more in return).

JerryTX

So no budget for wide body (and corresponding 3 sets of wheels) and no budget for proper Aero means working within the rules. I can't tape the nose, but I can repurpose the fog lights for brake ducts which I did. I can also effectively convert to a front breather only by virtue of the undertray. I do have enough power for ST2 or ST3; currently I'm exactly 3300lbs and 8lbs/hp which is ideal for ST2 minus the fact I don't have big wing and front splitter. A detune and minor aero (hood/ZO6 nose and vented fenders) and I have the opportunity to run ST3 at 9lbs/hp versus a similar car with big splitter and wing has to be 9.5lbs/hp. It is the one class that recognizes the wing/splitter as significant changes and provides some relief for those that don't have them.

Edited to add the following: More than anything I am interested in competition to make me a better driver. The car counts suck in ST2 and ST3 in NASATX right now. As it is, I'm running W2W in ST2 due to car counts and will likely double dip on race weekends to run TT3 for a possible chance at a tire.

spazegun2213

its true, and I was one of the people that proposed that major change in the st-3 rules. As aero is 1) not that cheap, and 2) lots of people just don't want to mess with it. That being said, there are LOTS of other things you can do that will shave time off and still be legal for st-3 and st-2 without aero (You also dont need a wide body for the aero, FYI).

I would also hesitate making your car any heavier, mine was about that weight in the old rules and that weight is a KILLER!

JerryTX

I understand I don't need the wide body for aero. I THINK the biggest improvement to my times right now would come from more grip, front first then rear. Less weight would help of course as well but heavy high hp cars always pull on the straights, lighter cars win in turns and on the brakes. I would love a lighter weight car from a brake pad budget for sure! What other areas do you think I should look at to shave time off and stay legal? Losing lots of weight is only an option if its not expensive; I just can't afford to throw a bunch of money at the car. I know the limits of my wallet and other guys can do the lexan windows and carbon fiber this and that, I'm not there. Just trying to play within the rules, be as competitive as possible, have fun and not break the bank. Venting fenders and such seems like it would cost some time with a hole saw and an air jigsaw plus some louvers etc.

JerryTX

I'll look into how I can make the bumper bulge at the front edge of the front wheel, I like that idea. I do not see a flap though on the ZR1 there, only at the front of the rear wheel?

varkwso

I was there when the aero/non-aero rules were being written up by NASA. In the end I think the aero cars will rule at most tracks.

You can put screens/holes in the upper fenderwells that go to vents in the hood. It helps on C5s. The rule of no fenderwell cutting to allow bigger tires or lower profile on the car is still in effect though.

Tape on front should not put you into aero hp/wt ratio in TT/ST3.

spazegun2213

are you running 315's all the way around? I thought even the narrow c6's could. If so anything larger is not going to make much of a difference.

shoot me PM with your email and we'll talk more offline. I know that my car was 3380 with me in it and 250lbs of ballast in the passengers seat (I have a c5 fast back) and I don't have any trick CF or lexan.

spazegun2213

Jerry, you can see the fender "lip" they are talking about here a little.

96GS#007

If you look close, you can see the gurney flap in this shot...



Backside (it's part of the wheel liner)

ErnieN85

it is part of the Zo6 &Grand sport front fender liners. I bought a couple and added them to my Z51 just cut them off and put right over the original

Rob Willis

Not my car, but:

JerryTX

Sent you a PM: My car is 3300lbs with me in it and cool suit and 50lbs of ballast and a full tank of gas minus 5 gallons (1 race). I'm 215lbs so the car is around 3048 with a full tank of gas and no driver/coolsuit/ballast.

Thanks to all for pics of the fender flaps and fender vents, that helps a lot! I like where this is going

JerryTX

Thanks Jim!

sleeper02Z06

So let me get this straight.......

You are saying on a C6 that going to the wider track of the Z06/GS/ZR1 and putting wider tires than the 315's on all 4 corners (ie. all the guys that moved to 345's in the rear with T1 C6's ) isn't going to help him even if he could do it??

Ross, surely you must know something the rest of us don't about physics and mechanical grip!

Joe

geerookie

Headed for the rabbit hole again!
Width isn't the sole answer to mechanical grip! lbs/square inch, if you dissipate the load across to great of a surface area you "float" across the surface instead of "gripping" the surface. Put a 345 tire on a smooth floor, see how much force it takes to push it sideways then add 50lbs of lead shot inside the tire evenly distributed and try the same thing. Now do it with a 205 tire.

The inverse is snow load on a roof.

With tires you look for a balance between mechanical grip and heat capacity.

spazegun2213

No joe, I'm saying that he is not running as wide of a tire as he can right now. with C5's its easy to stuff 315's on all 4, and a little harder with 335's but not impossible. Those CCW's he is running are a little narrow, and I think a small "upgrade" in tire size could not hurt.

Now he has a narrow body so I'm not 100% how hard that is to do, but it sounds like its not as easy as it is on the c5's.