Making Brake Ducts

[joeo]

I've been trying to come up with a nice way to make effective (not necessarily attractive!) brake ducts for the factory 135i brakes. I've been getting excessive, and uneven pad wear at the track which I think may be caused from heat (duh), but also localized boiling of the fluid right behind some of the pistons which would explain the uneven wear.

I started off trying to make it work with 3" hose and found these parts that I was able to bend/cut to fit the factory dust shield mount points.
http://www.summitracing.com/parts/aaf-all42117

I'd like to get it to blow on the vent inlet of the rotor, but it doesn't seem to be very possible.





I wanted the same looking duct on both sides. The passenger side has the oil cooler which complicated placement. I decided on a very thin, but very wide vent to capture a lot of air from underneath the car and direct it into a 3" hose.

It started to look like this (bottom removed) - using factory mounting points. I discovered that working with sheet metal involves cutting yourself.



Bottom installed:


The 3" hose is just a bit too tight, and I was able to push/shove/bend it into place, but I think 2" hose (can't seem to find 2.5"), might be the better way to go. If I go to the lock (steering), it will rub; not that I ever steer that far on track.



The vent was too low and would scrap on some bumps, so I modified it more to make the back end narrower. The amount of air that comes out of the 3" hose feels pretty good (ran the hose into the cabin and drove around; possibly getting odd looks from neighbors).

Thinking of redoing it all with 2" hose now and instead of using the 3" dust shield, just cut a 2" hole in the factory shield and use a 2" flange.
I used the aircraft spruce flanges:
http://www.aircraftspruce.com/catalo...uctflanges.php
Currently looks like this:



Thoughts/comments/help appreciated. Thanks!

-Joe

[Suprgnat]

Originally Posted by joeo

The 3" hose is just a bit too tight, and I was able to push/shove/bend it into place, but I think 2" hose (can't seem to find 2.5"), might be the better way to go. If I go to the lock (steering), it will rub; not that I ever steer that far on track.

Aircraft Spruce has 2.5 inch hose good to >550°F
http://www.aircraftspruce.com/catalog/appages/scat.php
http://www.aircraftspruce.com/catalog/appages/sceet.php

[Nugget]

Interesting work, keen to see how effective it is.
I bought a complete brake duct kit off another member, pics here.
But since I got my Stoptech BBK I don't have any issues with fade so never got around to installing it.

[Ginger_Extract]

Interesting. Have you thought about debris getting picked up in the ducting? What about installing a cut of mesh/grating near the mouth of it?

[Ginger_Extract]

will the factory dust shields have enough surface area/accept a 2" cut. It's been a while since I have futzed with them, but I do not recall the heat shields being particularly large. That aircraft site is awesome! I just happen to have some 2"ID/2.25"OD HVAC ducting laying about the garage. If you had to approximate, how much length is required for ducting per side. Would 3ft of ducting be enough? I'm trying to gauge based on the pictures, and that sounds about right to me.

[joeo]

Shoot - already bought some 2" hose! Thanks for the link; not sure why I forgot to check their site for ducting.
In testing, I have picked up a leaf; I just figured for a track event, I'd make sure they were clean.
The factory shields are large enough for a 2" cut; 2.5" might be too large, will need to measure. I ran the hose from the front to the back underneath the suspension, then 180 degrees back. It was the only way to fit 3" hose and still be able to turn lock to lock without the tire hitting the hose. Right now at the lock the hose is so compressed that it pushes the dust shield plate against the rotor; that's why I was/is thinking of going to 2".

The other thing I've been thinking about is spraying a fine mist (maybe 1-10GPH) of water directly into the rotor vent tied to the brake lights using a shurflo pump.

[Ginger_Extract]

Originally Posted by joeo

Shoot - already bought some 2" hose! Thanks for the link; not sure why I forgot to check their site for ducting.
In testing, I have picked up a leaf; I just figured for a track event, I'd make sure they were clean.
The factory shields are large enough for a 2" cut; 2.5" might be too large, will need to measure. I ran the hose from the front to the back underneath the suspension, then 180 degrees back. It was the only way to fit 3" hose and still be able to turn lock to lock without the tire hitting the hose. Right now at the lock the hose is so compressed that it pushes the dust shield plate against the rotor; that's why I was/is thinking of going to 2".

The other thing I've been thinking about is spraying a fine mist (maybe 1-10GPH) of water directly into the rotor vent tied to the brake lights using a shurflo pump.

I would be worried about wetting a hot braking system off track. The rapid temp change could cause premature heat cycling, and lead to more cracking of the rotors.

[Ginger_Extract]

Is your intake vent just some pieces of scrap alum. fastened/bonded together? I have a pretty good mental picture of what I could create with the pieces I already have, I just have to wrap my mind around the intake part of the system. I currently have the car up on stands for the coil over swap, I will mock up a dummy ducting system and take some notes/pictures.

[joeo]

Yes - the vent is made out of sheet metal from the local hardware store and sheet metal screws. I then used RTV to seal it up to make sure all the air is directed toward the hose inlet.
There are two main ways to do water cooling that I've found:
1. Spray into the duct vent to cool the air/get some water onto the rotor.
2. Spray directly onto the rotor vents (center of rotor). To reduce thermal shock you tie the pump (or solenoid) to the brake lights; then you're only misting the rotor under braking. After doing a little math, you really do need a lot of water (way more than 5GPH) to cool a rotor, but even a little can reduce the temperature a good bit.

See here:
https://grassrootsmotorsports.com/fo...s/66689/page1/

[Ginger_Extract]

mocked up my version of the ducting. FYI, 2.25" OD ducting will fit in the stock air channels of the M-Sport front bumper. Is there a good reason why I shouldn't channel it through there? Only thing I can think of, is that with the passenger side, the oil cooler being right next to this air channel could cause heat issues with the ducting.

[3002 tii]

Did you try taking the bumper off to see what other options may be present?

[joeo]

Yes - I've had the bumper off and didn't see anything that was obvious (I'm not expert though). If it was a race-car, and I didn't care about making holes, then there are certainly options!

The problem that I want to solve is having uneven pad wear, excessive pad wear, and the calipers cooking themselves.

[3002 tii]

Originally Posted by joeo

Yes - I've had the bumper off and didn't see anything that was obvious (I'm not expert though). If it was a race-car, and I didn't care about making holes, then there are certainly options!

The problem that I want to solve is having uneven pad wear, excessive pad wear, and the calipers cooking themselves.

Making holes isn't that bad. I cut into some shrouding on my other car but it looks totally OEM and best of all I chose trim pieces that could be easily replaced (for cheap) so going back to stock is pretty simple.

[fboutlaw]

Is there any proof that this is more effective than simply removing the dust shield? Since removing the dust shield, I haven't had over-heating issues with track use.

[joeo]

It depends heavily on the particular track. Slowing a car from 100MPH to 30MPH generates a huge amount less heat than 130MPH to 30MPH. Kinetic energy goes up with the square of velocity.
Some tracks I have no issue with the calipers. Higher speed tracks and tracks that have little time between heavy brake use generate more heat.

Given the number of track cars that use ducting, I suspect it is effective, but I personally do not have any evidence yet.

[TheSt|G]

I would have been tempted to give the F30 brake dust scoop shields a shot before all that tube fabbing.

[3002 tii]

Originally Posted by TheSt|G

I would have been tempted to give the F30 brake dust scoop shields a shot before all that tube fabbing.

F30 shields are better than E8x but they still have their limits. Agree though, I still think there's a cleaner solution if you take the bumper off.

[Nugget]

Originally Posted by TheSt|G

I would have been tempted to give the F30 brake dust scoop shields a shot before all that tube fabbing.

I have these but not sure how effective these actually are with wider wheels.
They don't actually stick out past the barrel of the wheel.

[Ginger_Extract]

Originally Posted by 3002 tii

F30 shields are better than E8x but they still have their limits. Agree though, I still think there's a cleaner solution if you take the bumper off.

The stock M-Sport bumper already has air channels in it, you cannot get much cleaner than making the OEM design work better:

[3002 tii]

Originally Posted by Ginger_Extract

The stock M-Sport bumper already has air channels in it, you cannot get much cleaner than making the OEM design work better:

Not sure if you're agreeing or disagreeing with me but that was my point.

Going through the bumper is much cleaner, whether you take the bumper off or snake it behind the wheel well was not the concern. The point was using the space behind the bumper is preferable. The only potential issue with the design above is that it will most likely rub against any tire that's wider than 235. Even if you zip tie'd the hoses to the control arms I can see it rubbing mildly. For a race car less of an issue but for a daily where you're actually using using full use of steering, you'll most likely have to replace the hoses every season.

[Ginger_Extract]

Originally Posted by 3002 tii

Not sure if you're agreeing or disagreeing with me but that was my point.

Going through the bumper is much cleaner, whether you take the bumper off or snake it behind the wheel well was not the concern. The point was using the space behind the bumper is preferable. The only potential issue with the design above is that it will most likely rub against any tire that's wider than 235. Even if you zip tie'd the hoses to the control arms I can see it rubbing mildly. For a race car less of an issue but for a daily where you're actually using using full use of steering, you'll most likely have to replace the hoses every season.

We shall see how nicely the hoses play with my 255's. lol

[joeo]

Kinda doubt you're going to be able to steer without serious rubbing. That's why I ran the 3" hose the way I did, but now I'm still debating 2".
What size hose is that?
Thanks.