another DIY brake duct
 

cut out the fake ducts up front and plastic-welded in some modified funnels. 2" silicone duct from there, around the radiator to the inside, then out the side to the outboards. i cut the stock brake dust cover and welded on a 2" steel pipe and repainted it. worked out pretty well i think. it could be improved in a few ways... better / more open incoming duct... and a better end piece that blows it more directly on the center instead of right now its slightly off. but it should be better than nothing. cost was a couple bucks for the funnels, 80$ for the silicone ducting, and like ... i donno, 50c for the steel tube maybe? oh and the hose clamps... those must have been at least $1.


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That's pretty neat, interested to see how they perform.

My only gripe is that the plastic vent looks a bit tough, but nothing that 20 minutes and some sandpaper or a file couldnt fix

yeah, i really should have just used a hot knife and done it myself. my brother went to town opening them up with a scalpel. it's not super noticeable in person unless you look for it. once i stop being lazy i'll print some molds and make a new set of the scoops in carbon fiber and make it look nicer. i just have to fix my printer first, which is kinda a pain in the ass.

Very nice man! Where did you buy the hose and stuff?

the silicone duct hose is from amazon. there was only one seller with prime and the hose looked nicer than the others. and then there was like a ton of weird other brands that didn't look as nice. so i paid the premium price of $80. oohhh la, la. I picked up the funnels from harbor freight while i was getting a little belt sander for my brother who started making knives. (guess what he was using to cut the backing off the fake vents? lol) i had the steel tube and other shit laying around.

nice job!

Why not just take of the disk shroud?

If you remove it you have to fabricate something else to attach the outlet from the hose to. The OEM shield is convenient since it's already the right shape/size, and is already drilled to mount behind the hub.

i looked through probably thousands of photos online and i came to the conclusion that it looks better in silver. please excuse my shit welds

https://i.imgur.com/C65RqZY.png

Nice setup man. That hole in the fender liner is already there, right? Any pics of how the hose was routed around the radiator?

No, my point was that if you want to improve heat loss from the disks then why not remove the shrouds?

That doesn't actually help as much as you would think. Vented rotors are cooled much better by directing air into the center and letting it flow out through the vanes.

no you gotta cut the hole but it's pretty easy and they have spots for you to cut out that make it look like its factory. and its not the fender liner, its the one right above the lower control arm. i'll try to grab some pics of the inner routing later today

i'm sure there is plenty of airflow on the surface with or without the shrouds. they have little vents in them as well. the rotor itself with the little vanes inside acts like a pump, when they spin the air around because the rotor is spinning, it pumps air through the center of the rotor. getting positive pressure going into that pump makes the pump vastly more efficient. more pump == more heat go bye bye.

OK, you are on your own.

Tiny bit of wee going down my pants from laughing.

Keep it up.

I thought about this a lot more and did some napkin math and I'm even more confused now. let me illustrate some points and make no clear conclusion.

1. the rotors obviously pump air.

2. the rotors pump a lot of air. doing napkin math, the ducts are about half the size they need to be in order to provide enough air to the rotors that there would be positive pressure before the entrance to the rotor at 80mph.

3. when the rotor is pumping, and the shroud is in place, the rotor pulls air from the area that is shrouded. that means it pulls air over the surface of the rotor, then pumps it back out through the inside. this should be substantially more air flow / cooler air over the back rotor surface than it would see simply spinning by itself in standing air that wasn't being pumped.

4. if you remove the shroud, it should improve the rotor's pumping effect, which should help cool the inside of the rotor a lot. but you lose some effect of the pump on cooling the back surface of the rotor. however you dramatically increase the back surface of the rotor's radiative cooling capability. another side effect of going without the shroud is that the air going into the center of the rotor is cooler.

5. because of 3 and 4, running without a shroud will cause a higher heat differental in the back rotor surface, but should cool the front rotor plate better and give more even cooling on one side of the rotor versus the other.

there might be some impact on rotor life regarding heat differential... it might be that one way is better than the other. i suspect cooling from only the center would be more prone to cracking but i'm not entirely sure if the difference between one side of the rotor to the other would really be that high that cooling only on the inside and decreasing cooling on the rotor surface would have much of an impact on cracking...


so now i have no idea if the shroud is beneficial or not. at least it helps keep the dust down?

starting to lean toward the idea that it should be minimal shrouding.

That many bends is going to have an impact on the flow rate due to all the back pressure.

No back pressure. What from? Restricted flow maybe.

But not enough to make a gnats difference?

The bends cause a change in direction of the air. Body at rest stays at rest. Every action has equal opposite reaction. That means every change in direction requires energy. In other words the bends create a flow restriction. It's not massive but I would expect it to be at least 5 percent in my case

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And you can lead a horse to water but a pencil must be lead.

... what?

Bends in piping can create pretty significant reductions in flow, especially when that flow is not pressurized (the air flowing through is not pressurized or barely pressurized). Air will take the path of least resistance and if there is less resistance sliding sideways over the front of the bumper versus going though a long tube with numerous bends, it will take that path. I have only enough knowledge in this area from years of playing with aquarium piping and studying aerodynamics to get myself in trouble, but someone with more knowledge in fluid dynamics should chime in.

You might do some string testing to see if you are getting adequate flow.

I hope you are successful as routing on this car sucks and I am interested in doing something similar, I just have a feeling it won't be sufficient for heavy tracking by an advanced driver.

Shrouds do a lot, they 'shroud' heat from other areas, direct flow, even increase downforce if done right.

This is pretty much how it's done.