gaspeddleZ07

I'm going to be using my C4 Z07 for TimeAttack in Ontario this year, so having cool brakes is critical. I ordered the MAM units and must say I was somewhat underwhelmed with the ducting provided. So I ordered up some 4x6 ducts to see if I could recreate on my C4 what worked well with my Firehawk
http://forums.corvetteforum.com/albu...ctureid=131233
http://forums.corvetteforum.com/albu...ctureid=131234

I hadn't realized the difference in the size of the spoiler so it was going to be a challenge to have the larger ducting work under the chin of the C4
http://forums.corvetteforum.com/albu...ctureid=131223

I cut the duct so the top of it was sandwiched between the spoiler and the facia, and would also use two of the spoiler mounting screws to help hold the top of the duct in place. Wanting additional strength on the bottom edge I heated the duct in boiling water and folded it over, then attached the sides with 3/8" bolts.
http://forums.corvetteforum.com/albu...0&ref=gnr-next
http://forums.corvetteforum.com/albu...ctureid=131225
http://forums.corvetteforum.com/albu...ctureid=131228
http://forums.corvetteforum.com/albu...ctureid=131229
http://forums.corvetteforum.com/albu...ctureid=131230

I haven't hooked up the ducting yet, but it seems to hang only about 1/2" lower than the original spoiler so should survive day-to-day life.
http://forums.corvetteforum.com/albu...ctureid=131231
http://forums.corvetteforum.com/albu...ctureid=131232

I'll post some additional pictures once the plumbing is further along to the hub!

Thanks for a great forum so I could see what others were using and thought I'd share what I'm trying

rithsleeper

So far looks good. These c5 guys are hard to impress unless you install a kit. Ive basically finished my rework and have sucessfully tested my second try. However ill tell you if you have an ac system you wont be able to find a good way to plumb it with 3" hose. I had to shape and make a fiberglass duct that got thin to clear the tire when at full turn and it still rubs a little. It is about 2" wide. And runs up along the wheel well. C4 is much harder than a c5 to fit the ducting. If you dont have all the ac lines then its a round about way but straight forward plumbing. Either way you definately need the brake cooling even on street tires I would start getting fade on lap 3 with c5 brakes.

Bill Dearborn

Don't know what the distance is from the rear of the duct to the tire but you may be a little too close to the tire with the duct placed there. I had an 86 which had a taller air dam. 84-90 air dams were just a little taller as the body mount didn't curve down quite as much as the 91-86 cars. I was able to drill a 3 inch hole in each outboard air dam right next to the center section and RTV 3 inch duct hose into the opening. This gave me practically a straight shot toward the wheel well which helps air flow. Then I used cable tie wraps (with adhesive tie wrap mounts attached to the bottom of the fascia) to hold the ducting to the bottom of the fascia and ran it to the stabilizer bar and from there past the wheel so the duct was aimed at the front of the brake rotor.

The ducts worked well and I never needed to put spindle ducts on the car. Each time I hit the brakes coming into a corner I could see a puff of brake dust come out of the front wheel wells. Based on that I assumed I had excellent air flow to cool the rotors and calipers.

Bill

gaspeddleZ07

The ducting part seems more challenging... I was looking at one of the Z06 ducts and they're cheap so might try one of those to see if I can make that work. Definitely will require extra thought!

I'm hopeful I'll have enough room before the tire. It's offset more than I'd like, but allows me to secure it with two bolts on the top rather than one... we'll soon see!

RedLS1GTO

It doesn't have to be a kit. It DOES have to be something that isn't going to throw shrapenal all over the track when it comes apart.



To the OP, It looks like you have done a pretty good job of making everything but I think you might run into some issues with your ducts being that low. It won't take too many hits on the ground, even "light" hits to destroy the inlet. If you grind down the bottom edge you effectively lose all airflow that the duct is designed to give.

You seem to be pretty decent at fabrication, so if you do end up having issues, you could always try a different approach.





Personally, I think that unless you are using spindle ducts to get the air where it really needs to go, you are wasting time and effort.

1991Z07

That is exactly the plan I had for my track car...it made the most sense to me since marker lights aren't required anyway...

Being up that much higher also means you don't run the risk of picking up track debris and throwing it into your rotors.

A rock tossed in there would NOT be pretty

How well do yours work? Any issues with rotor temps getting too low?

I figured if the side marker lights weren't enough, I could always take the turn signal lights out of the front of the bumper and plumb them in as well.

But a little "Gourney flap" on the outside edge to catch the boundary layer and direct it in could increase the efficiency as well.

Kubs

Like mentioned the 84-90 Z51 spoilers are taller and I was able to make them fit no problem. I dont have the best pictures of the ducts, but here are some where you can see them:

RedLS1GTO

Before I installed them I was trashing pads and rotors. Since they were added I haven't had even a slight heat related issue.

I didn't collect numbers and it is about as un-scientific as it gets but I did use a big compressor and some smoke to make a mini parking lot air tunnel. The flow into them was very good and the flow through the ducting passed the eyeball test. NACA ducts do a great job of "pulling" air in if you can get the right AoA and the marker lights are at almost the perfect angle from the front of a C4.

larryfs

I used the small diameter Ecklers kit for many years. Worked fine. At speed, it's more than enough air.

93Rubie

This is going to come in hand in the future.

gaspeddleZ07

I was thinking of the NACA duct on the cornering lamp as well but decided against it with the headlight and hood prop rod getting in the way.

I've not had scraping issues in the past so we'll see how an extra 1/2" works in day-to-day + tracking!

I do have to admit that plumbing the hose will be a challenge so we'll see what works... a good reason to start in January LOL!

RedLS1GTO

If it was a dual purpose track/street car that would probably be a pretty big annoyance. To open the headlights the hood had to be up (no biggie since mine was track only). I modified the prop rod so that rather than it folding with the hood, I removed it when the hood was down. When I raised the hood I clicked it back on.

gaspeddleZ07

Making some progress on my brake ducts. I had bought a couple of Z06 ducting as I was considering drawing air directly from the fog lights, but it seemed very time consuming once everything was moved... so I hacked the crap out of them and used it basically to create clearance around the wheel. It's mounted using one of the fender bolts and I'll just put a piece of tape over the hole. It seems to work but not track tested yet.

1991Z07

Hmmm...the above shot with tire wouldn't work for me...

I have rub marks on the liner right where you have the Z06 duct secured, so it would limit my wheel turn in a bit.

Hopefully it works for you.

I'm working VERY hard to avoid hoses under the car in harms way...I'm going to use an old Callaway trick from their B2K turbo cars - using the frame rail as my duct. A hole saw used in the right place...with a round piece of steel pipe welded just inside the hole (for strength)...and I think it'll work just fine. Feed it with NACA ducts from the side marker lights like RedLS1GTO did...but also add the front bumper lights to it for more airflow.

My build is a permanent track car...I can see why nobody would want to do it for a street car.

Can't wait to hear how yours does at the track

jaa1992

Have you checked your ruleset?
I know for NASA what you propose is not allowed.
There was lots of discussion last year about it. Can't put a hole in a frame rail big enough to do what you want.

1991Z07

I don't race in NASA...so their rules don't apply to this build. I race NCCC and do track days (HPDE), and am wanting to step into Open Road Racing.

For NCCC, it is an RP car and I can do frame mods like this. For Open Road Racing they only look at the safety aspects of the vehicle...as long as I don't weaken the frame by doing my mods they are cool with it.

I don't particularly want to be in close proximity to other cars with an opportunity to rub paint with this car. It's a '92 ZR-1 body...and body parts are "difficult" to come by (to say the least).

But...I CAN get a 335 inside the rear fenders...and will need every bit of rubber I can get to keep the LS7 from lighting up the tires every time I press the go pedal.

The car's safety equipment however WILL conform to (nearly) all sanctioning organizations...so whomever buys it from me won't need to spend a lot on that aspect.

A few items might need to be changed to conform to the rules of the sanctioning body they decide to compete in...but that won't be my problem.

So, in other words...I don't care what NASA says I can do about brake vents...I don't intend to race it in their organization. I might do some HPDE's with them, but they don't care about brake ducting for drivers events...only safety items.

Have not seen anything in SCCA TT rules to disqualify this modification either.

And looking at February's modified SCCA GCR (even though the C4 doesn't qualify for competition):
9.1.5 Production Category Specifications

Section 7
i. Brake Ducting
1. Brake air ducts can be fitted.
2. The front brake duct inlet(s) must not extend to the side
beyond the centerlines of the front wheels, or forward of
the forward most part of the front of the body or front air
dam.
3. Rear brake duct inlet(s) must face forward, they must be
located no more than 24” forward of the rear axle centerline
and must not extend to the side beyond the centerlines
of the rear wheels.
4. Backing plates and dust shields are unrestricted.

In 9.1.9.2. Touring (T2-T4) Category Specifications

Section 6
5. Any brake ducts are permitted, but they must serve no
other purpose. Fender liners may be modified solely for
routing and attachment of brake ducts. Duct intake openings
may only be created by the removal of an auxiliary or
fog light assemblies. A total of 2 light assemblies may be
removed. The stock headlamp location is not permitted for
brake ducting. If car is not equipped with an auxiliary or
fog light assemblies, 2 alternative duct openings may be
created by the removal of 2 sections up to 14.5 square
inches of stock false grills originally located in the front
fascia. No part of the fascia may be modified. The ducting
must not be visible from outside the car.

Haven't been able to find anything on frame modifications pertaining to this in there yet...and used the search function pretty extensively, too.

l98tpi

Do you have additional Picts showing the routing of the ducting to the rotor? I like this set up. I remember when you posted about it a few years ago. I think the op's style is nice too, but my tire would rub the ducting with the way that is routed.

jaa1992

I wasn't trying to tick you off
I was just pointing out that there are some sanctioning bodies that don't allow the modification. It may help others.

If it works for the folks you run with good deal. But you gotta post pictures

gaspeddleZ07

Agree... but this seemed to minimize rubbing... didn't see many more options as almost everything was catching/binding/rubbing against something more dramatic. I'm on road courses so haven't needed to be full lock very often so it should work! We'll see in a couple of months!

1991Z07

It's all cool...I'm not upset. You have to pick your battles when building a car. You can't make one fit all the molds...so you build it for where you expect to run it.

There will be a series of posts on the build, so stay tuned.