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Old 05-06-2009, 01:46 PM   #1
dunk
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Default Exotic Brake Cooling Ideas

I'm bouncing around the idea of planning a 2gph water injection nozzle in each brake duct. I've found some examples of this done with success on racecars in the past, however have seen very little current data. I'm willing to be the lab rat here.

Any thoughts from NASIOC?

-Duncan
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Old 05-06-2009, 01:56 PM   #2
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you need more cooling?
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Old 05-06-2009, 02:15 PM   #3
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I say go for it!!

Are you planning to trigger flow demand based off of current from a brake line pressure sensor? It could be variable and progressive.

How did you come up with 2GPH flowrate per brake (assuming just the fronts)?
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Old 05-06-2009, 02:17 PM   #4
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did you already consider a fan? Someone suggested that those "electric turbochargers" use model jet airplane engines. I looked into them and you can get over 850 scfm from medium-large units that fit in a 3" tube. They don't build pressure very well and bigger units require too much power to justify as a supplemental turbocharger, but that should be more air than typically flows in brake duct hose at >70 mph. Could do some math...

Frank
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Old 05-06-2009, 02:31 PM   #5
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I've never done a water cooled brake system but I would imagine you'll only see a worth while benefit from injecting water into the rotor hat area or inject into an airstream the feeds into the rotor hat area.
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Old 05-06-2009, 02:32 PM   #6
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Quote:
Originally Posted by Frank A View Post
did you already consider a fan? Someone suggested that those "electric turbochargers" use model jet airplane engines. I looked into them and you can get over 850 scfm from medium-large units that fit in a 3" tube. They don't build pressure very well and bigger units require too much power to justify as a supplemental turbocharger, but that should be more air than typically flows in brake duct hose at >70 mph. Could do some math...

Frank
he already has a fan on there.. hahah thats why i asked if he needs more cooling.
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Old 05-06-2009, 02:34 PM   #7
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When you are not racing, you can adjust the nozzles to spray your tires with soap water, and do AWD burnouts without fear of breaking your shizz.
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Old 05-06-2009, 02:49 PM   #8
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My only theoretical concern would be if the mist/air temp is too cold, you might do some warping damaging due to the rapid change in temp. I'm thinking going from glowing red rotors to spraying them down with a garden hose as an extreme example...
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Old 05-06-2009, 03:07 PM   #9
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Originally Posted by generalee69 View Post
My only theoretical concern would be if the mist/air temp is too cold, you might do some warping damaging due to the rapid change in temp. I'm thinking going from glowing red rotors to spraying them down with a garden hose as an extreme example...
I did the basic math and at rotor temps over a 1000 degrees the water will be steam long before it touches the rotor face.

-Duncan
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Old 05-06-2009, 03:09 PM   #10
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Originally Posted by Homemade WRX View Post
I say go for it!!

Are you planning to trigger flow demand based off of current from a brake line pressure sensor? It could be variable and progressive.

How did you come up with 2GPH flowrate per brake (assuming just the fronts)?
I picked 2gph out of a hat. It seemed a reasonable size based on the flowrate and tank sizes needed to sustain 45 minutes of operation. I'm going to dig through the Trackmate data and see how many minutes of braking I do per x driving time. I'll use Summit Main for a data point since it's the worse out of all the tracks I drive.

I was going to use a simple on/off using the brake switch to keep the cost and complexity down.

-Duncan
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Old 05-06-2009, 03:11 PM   #11
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Quote:
Originally Posted by STi-MAN View Post
you need more cooling?
Wouldn't hurt. My rotor temps are still hotter than I'd like. Before the next track day at a minimum I'm going to .

Remove the fans from the primary ducts (restriction at speed)

Hook them back up to the lower RCE ducts (currently not hooked to hose)

This shold give me both a low and high speed system.


Doing the water injection would be cheap using parts from Mcmaster and I just thought it would be interesting to compare how well it works.

-Duncan
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Old 05-06-2009, 03:49 PM   #12
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Hey Dunk,

I did some research on this a while ago. You need the nozzles to be fairly close to the beginning of the ductwork as opposed to right next to the rotors.

-Clint
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Old 05-06-2009, 05:45 PM   #13
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Originally Posted by Turn in Concepts View Post
Hey Dunk,

I did some research on this a while ago. You need the nozzles to be fairly close to the beginning of the ductwork as opposed to right next to the rotors.

-Clint
Clint,

Return my call when you get a chance.

-Duncan
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Old 05-06-2009, 07:31 PM   #14
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Well, they do this alot in the big semi truck racing down under. But i know for awhile (maybe they still do) WRC cars had watercooled calipers as in water flowed through them.

There was some talk awhile ago and some people brought about the hypothesis of steam forming under the pads and causing loss of braking power.
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Old 05-06-2009, 08:42 PM   #15
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Quick temp fluctuations have different effects on different materials. Also, different brake compounds work more effectively at different temperatures. So, finding a pad that can handle quick thermal cycling and do its job effectively.

Good luck and let us know how it works.
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Old 05-06-2009, 08:56 PM   #16
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Quote:
Originally Posted by rexspeedworthy View Post
When you are not racing, you can adjust the nozzles to spray your tires with soap water, and do AWD burnouts without fear of breaking your shizz.
this.
needs to happen
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Old 05-06-2009, 08:58 PM   #17
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Why not go to the 4" fans with the 3" reducer?
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Old 05-06-2009, 09:09 PM   #18
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Originally Posted by Token-Negro View Post
Why not go to the 4" fans with the 3" reducer?
You're no fun.

I don't have the room to package it all in front of the brake duct inlet. I'm debating putting the 3" fan parallel to the main duct, with a y junction into the main pipe. This would probably involve the least fabrication.

-Duncan
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Old 05-06-2009, 09:42 PM   #19
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Duncan, why are you having so many brake cooling problems? How much does your car weigh? How big are your rotors? What pads do you use?

I figure our cars can't be too far off on weight and top speed, and I have no problems with brake fade.
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Old 05-06-2009, 09:55 PM   #20
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Quote:
Originally Posted by Turn in Concepts View Post
Hey Dunk,

I did some research on this a while ago. You need the nozzles to be fairly close to the beginning of the ductwork as opposed to right next to the rotors.

-Clint
This would make sense. Applying some sort of cooling fluid directly to the surfaces of the caliper or rotor could cause the metal to expand and contract to fast and to much This could cause the metal to crack. This is a really good idea though. You've got to post some pics when you work out the details. I wonder if there is way to use a flexible bladder?
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Old 05-06-2009, 10:03 PM   #21
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why not just have a small nozzle spray something like C02 on it?
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Old 05-06-2009, 10:33 PM   #22
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Quote:
Originally Posted by wallyman424 View Post
Duncan, why are you having so many brake cooling problems? How much does your car weigh? How big are your rotors? What pads do you use?

I figure our cars can't be too far off on weight and top speed, and I have no problems with brake fade.
Problem is subarus are very front heavy so the front brakes do most of the work. I've gone through countless brake setups up front, including several sets of rotors, a couple different calipers, and a ton of pads. I still have my stock rear rotors and calipers (5 years old) and they are completely fine.
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Old 05-06-2009, 10:42 PM   #23
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Quote:
Originally Posted by wallyman424 View Post
Duncan, why are you having so many brake cooling problems? How much does your car weigh? How big are your rotors? What pads do you use?

I figure our cars can't be too far off on weight and top speed, and I have no problems with brake fade.
As Dan said, Subaru's are tough on brakes.

Car weights 3250 - race weight
Rotors are 13.3x1.26.
58% of the weight is on the front of the car.

It's not a fade issues as the brakes hold up fine. I'm just going through front rotors a lot quicker than I'd like. VIR is not so bad, but Summit Main kills them.

-Duncan
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Old 05-06-2009, 10:43 PM   #24
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Originally Posted by boost junkie View Post
Problem is subarus are very front heavy so the front brakes do most of the work. I've gone through countless brake setups up front, including several sets of rotors, a couple different calipers, and a ton of pads. I still have my stock rear rotors and calipers (5 years old) and they are completely fine.
I've had the same set of race pads in the rear for about 6 events now. I've never replaced the rear rotors.

I'm on the fourth front caliper setup.

-Duncan
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Old 05-07-2009, 12:10 AM   #25
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I want to see the water injection too, buuut, have you considered switching to one of the newer ceramic-based pads like the Ferodo DS2.11's? I understand the ceramic-based stuff is gentler on rotors. Since you say the rotor temps aren't too high, you may have room to switch to a softer pad. How hot is "not too hot"?

If you're running stoptech's you could switch to the 355mm rotor, assuming you use 18" wheels...

Frank
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