wstaab

Stock C6/Z06 front brake cooling ducts are not very efficient at directing air to the front rotors. The rubber air dam below the front valence is there to direct some air into the ducts from below. They do not work well.
We have mounted a pressure transducer in the left front duct and monitored the pressure differential at 150 mph on the back straight at Road Atlanta. Negligible! This is the same pressure transducer system used to measure airbox pressure on race bikes with ram air ducts in the front fairing.

In fact the ZR1 and all the carbon ceramic brake Z06's remove the rubber air dams and use a deflector on the lower suspension a-arm to direct air to the front rotors. Works well at speed.


Katech has a very nice setup with the ZR1 front splitter, brake duct scoops, and a undertray to seal everything up. Works well at speed.



A different approach borrowed from the NASCAR short track cars is cooling fans in the stock ducts. Advantage is positive air flow to the rotors at low speeds and while driving through the pits. Testing as shown reduction in front rotor temps by as much as 200F after a 20 minute track session.

How to:
Small high efficiency custom fans from a supplier to NASCAR teams.


Mounted in the ducts with rivets.



A relay mounted next to the fuse box with a circuit breaker to control the fans.


A short VIDEO of the fans in action: http://s58.photobucket.com/albums/g2...t=VID00254.mp4

Bill Dearborn

Did you check air flow/velocity through the ducts? Air pressure might not be all that high with good air flow. The better the flow the lower the pressure.

I saw the same type of ducting setup that is on the C6 on several C4 race cars years ago. It seemed to work well and got more air to the brakes than ducts mounted to the spoiler.

Bill

NORTY

Micky uses "in duct" fans on his ZO6. Then again, he drives his car on his own track all the time!

Johnjan

I agree with Bill. Pressure will reduce with increased airflow. Bernoulli's Law. It's why airplanes fly. Motorcycle airboxes are a closed system metered by however much air the engine is using. Different situation entirely.

Close off the outlet of the duct and THEN read the pressure.

wstaab

The theorem of Bernoulli's principle that applies in this situation is not an airfoil but the venturi effect. The Z06/ZR1 brake ducts are a modified venturi. They have a large round opening transitioning into a smaller oblong cross section transitioning into a smaller round opening.
The device I use can measure a pressure differential of 0.001 bar/0.1 kPa positive or negative relative to ambient atmospheric pressure using a static port. The measurement point was at the point the plastic duct connects to the flexible duct. If there was increased airflow there would be a pressure drop. If airflow was being restricted due to the spindle ducts position relative to the brake rotor you would see a pressure increase. In my testing the measured data in the duct was small, less than .1 millibar. Note this car used an aftermarket splitter and had a lower ride height then stock. The front splitter would actually touch the ground braking for turn 10 at Road Atlanta. Results may not be the same for a car with the OEM front splitter and standard ride height.
The fans in the duct work. They reduce brake rotor surface temps as much as 200F on a 90F ambient day. For one session the driver forgot to turn the fans on and the brake rotor temps were in the same range as a car with no fans. One of the concerns was if the fans quit working would they restrict airflow enough to cause elevated temps due to their location in the ducts. That was the motivation for the testing.
Your results may be different.

John Shiels

http://www.suzukaracing.com/1%20Blower.html

in the article

John Shiels

to see the other discussion and prices I got.

http://forums.corvetteforum.com/auto...post1577151411

track junkie

According to this article brake fans can obstruct airflow if not installed correctly.
http://www.stockcarracing.com/techar...rol/index.html

http://www.nascar.com/2002/kyn/tech/...rakes_cooling/

John Shiels

if not installed correctly


that is key in anything.
How many here are running at high speed tracks like NASCAR does? Even a fast track like Pocono Long Course your average speed is way below high speed NASCAR tracks which will be probably well over 150 mph and near 200 average on others. Most cars at HPDE or SCCA racing don't see over 170 on the ed of the fastest tracks for a short time period. The fans I linked to used in NASCAR I think would be good on all the types non-pro Corvette run on.

Bill Dearborn

John, the correct installation mentioned in the articles referenced is to use a Y duct so the fan isn't directly in the path of air coming in from the front of the vehicle. That way the fan doesn't block the air flow. The article also mentions the 35 mph air flow speed that I mentioned in the other thread. Nothing wrong with using a fan just need to know its limitations and where to mount.

From the article:
Spencer cautions, however, that you can harm your overall brake cooling system if you don't install these fans strategically. "Those fans are powered by an electric motor and spin at a constant speed," he explains. "Usually, they move air at about 35 mph. Going down the straights, you can get much more flow than the fans will allow through your ducts, and the fans will actually cause the air to back up and not allow it to get to the rotor. You can keep this from happening by not installing the fans in line with the duct that leads the inlet air to the rotor. Instead, install it in its own path and have the duct from the fan "Y" into the main line. This way you get the best of both worlds."

As for the speeds we see on the track you know better than most we see some high speeds . At WGI there are many sections where the speed is above 100 mph with the lowest speeds being around 60 at the apex of several turns. There are even turns where the speeds are above 100. Slowing from 150 to 160 to enter the bus stop between 80 and 90 and then carrying 90 plus around the carousel into the chute going to turn 6 where speeds get to 110 and then the downhill braking zone to get down to around 60 for turn 6. You can lose your brakes at the end of the back straight but if you lose them going into 6 because you just severely heated them going into the bus stop then you get this result:



This happened right in front of my students car last July. The instructor in this car thought his student lost the brakes going into 6.

Bill

track junkie

The average speed for my old Porsche Cayman S at the Putnam Park road course is 78 mph according to my Trackmate data. I expect average speeds with my Z06 to be around 84 mph.

Average speeds for a Z06 at Road America would be greater than 100 mph.

The air fans are probably best when racing and coming in for a pit stop when installed in the y configuration.

Gary2KC5

Bill if the student lost the brakes it was b/c they were running stock pads and blew through them or had stock brake fluid...Z06's with the basic track prep just don't run out of brakes
The phrase "avg speeds" should not be in this discussion...say you do a 2:30 lap @ RA...you avg 96 mph but you brake in T1 from 165 mph to 70 then in T5 you brake from 165 to 45, then in T8 you brake from 110 to 45 then in T12 you brake from 140 to 70...

but you are only avg 96 mph...tell your 1400 degree front rotors you're only avg 96 mph

Bill Dearborn

I agree. The car was an 06 with just 9K miles on it. It was the driver's first time on the track with the dream car he had just purchased. Fluid may not have been bled in 4 or 5 years, the pads may have overheated but more cooling could have helped.

Bill

track junkie

When considering using a brake duct fan that blows air at 35-55 mph and your "average speeds" are substantially above that, restricting air flow to your brakes below your average speed doesn't make much sense to me.

John Shiels

thanks Bill