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      04-07-2012, 11:20 PM   #1
joeo
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Water Cooling Calipers

Wondering if anyone has considered using a very fine water mist in the brake ducts to cool the calipers during track events.
I used to build water injection kits when I owned a 1991 MR2 turbo, but these same parts could be used to make a very fine mist to cool the air leading to the rotor/caliper.
Apparently they use misting in the brake ducts for Australian V8 super cars.
Quote:
http://www.v8supercars.com.au/Portals/v8/R...v%20C_Final.pdf

"10.1.13 In order to provide air for the cooling of the brakes of each wheel, it is permitted to
fit a duct to each wheel which must comply with the following:
10.1.13.1 the intake for the front brake ducts must only be the brake duct opening
in the approved front bumper.
10.1.13.2 the intake for the rear brake ducts must be situated wholly within the
perimeter of the bodywork and not below any point on the lower edge of
the front bumper.
10.1.13.3 forced induction or extraction systems are not permitted.
10.1.13.4 any system or device which varies the air flow in such brake ducts is not
permitted
10.1.14 A system which sprays a mist of water into such air ducts is permitted. The
reservoir for this system must be wholly located in the boot/luggage compartment.

10.1.15 Brake calipers incorporating liquid cooling/recirculating systems are prohibited."
Perhaps if the mist is fine enough (about 1.0GPH) it would be enough water to cool the brakes without causing cracking of the rotors.

-Joe
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      04-08-2012, 04:27 AM   #2
jsmonet
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if you're keeping it moving, great. just throw in a speed-activated cutoff switch so you're not dousing them as you're coming to a stop.
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      04-09-2012, 12:23 AM   #3
uberschnell
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Or just buy a BBK and be done with it.
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      04-10-2012, 08:37 PM   #4
joeo
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The stock BMW brakes (in my experience) are fine - they still work even after the dust boots melt away and the calipers turn a funky color. It could be significantly less expensive to cool them with water.
What I'm wondering about is if it would be best to:
1. Mist the air with a very fine water spray leading to the rotor/calipers.
2. Directly spray the rotor.
3. Directly spray the caliper.
I did some math that I think is correct:
http://cybrina.mine.nu:8080/BrakeCalcs/

You specify vehicle weight, front and rear rotor weight, and start and end speed. The app calculates the temperature rise of all 4 rotors.
I know the front rotors weigh around 21.6lbs - anyone know how much the rears weigh?
What's interesting is the temperature of the rotors will rise about 50 degrees F if you stop from 50MPH. However if you slow from 100MPH to 50MPH the rotors will increase in temperature by about 150degrees.
I'm pretty confident that the temp rise is correct, but the amount of water required that I'm calculating might not be right yet.

-Joe
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      04-11-2012, 09:39 AM   #5
Focusedintntions
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Joe,
In order to do this well it would seem you'd need ducting...which is something we need anyways....I'm confident with ducting we'd have enough cooling and not need to water things down lol
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      04-11-2012, 04:35 PM   #6
fourtailpipes
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i had considered trying this until i saw that it's not permitted for NASA TT. i don't think it's a bad idea. it's all in the execution.
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      04-11-2012, 07:05 PM   #7
joeo
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I'm not as convinced that ducting alone will solve the melted boots/discolored calipers issue. If I slow from 135MPH down to 50MPH all four rotors will increase in temperature about 330 degrees F. That's making the gross assumption that the front and rear do the same amount of work, which they don't - it's much worse for the front. Do that 4 times in a row, and you're at 1320 degrees!

With those RB rotors which weigh less, the temperature rise is even higher. No doubt ducting will help - and I think misting the air with high pressure water will help that as well. I'm still wondering if hitting the rotors and/or calipers directly with mist is a good idea or not.

Most track organizations will not allow any sort of fluid to spill on the track - so the water will have to be consumed in the process, or the mist fine enough that it evaporates.
Sorry for the old video, but this is the type of misting I have in mind:

http://lovehorsepower.com/Videos/MR2/WI_Nozzle_Demo.MPG

-Joe
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      04-14-2012, 12:05 PM   #8
GaryS
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Quote:
Originally Posted by joeo View Post
I did some math that I think is correct:
http://cybrina.mine.nu:8080/BrakeCalcs/
This is cool. Where did you find the formula?
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      04-14-2012, 05:22 PM   #9
joeo
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I found this formula a couple places including:
http://www.pirate4x4.com/tech/billav...hermalCapacity

The water calculations were done by myself using latent heat. They don't take into account the amount of energy required to raise the temperature of the water - only the amount to state change the water.

-Joe
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      04-14-2012, 07:40 PM   #10
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JOEO-Ducting will provide immense amounts of cooling. After working with Grand-Am cars which have constant brake temp readings I can tell you that between braking zones cars with proper ducting compared to no ducting usually would see temperature drops of about 15% before the next braking area. If ducting is done properly you should never get your brakes hot enough to boil the fluid and should NEVER get them hot enough to brake bolts! If you are braking bolts you likely have other issues than overheating. After all that is said though I am curious to see how well misting water on the rotor would work. Post some pics when you have a chance! Great to also see the base of knowledge present on this forum!
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      04-14-2012, 09:04 PM   #11
joeo
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Never had any issues with braking bolts! The dust boots on the stock calipers melt away and the caliper itself turns a yellowish color. The brakes still work fine. I've never had any issues with fade (I use ATE fluid and change frequently). I actually think the stock brakes are very good except for the dust boots.

That said, others have had issues with the ceramic 'caps' crumbling away. I have not personally had that issue, but I suspect temperature could be a cause there as well.

No idea where to mount said misters yet.

-Joe
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      04-15-2012, 08:03 AM   #12
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I agree that the brakes are great for modulating which is rare in a BMW. My piston caps are almost completely gone and I will be replacing with the Stoptech piston repair kit. The misting devices on the Australian cars are located about two inches inside the ducting pipe.(at least on the two cars that I have seen) I am sure it would be possible to mist without ducting but would likely not have as great of effect. The ducting kit I am working on is almost complete (after the eight prototype, which can be frustrating and has been expensive but will be worth it as I am already seeing temperature drops of 18%)
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