I have my first track day on the new turbo setup and of course I haven't sprung for a big brake kit yet. To help give the stock size rotors a chance I fabricated some brake cooling ducts. This is nothing new, but I was intrigued that all the commercially available plates pretty much just blew cool air on the backside of the rotor. Maybe it works, but it's very common on non-miata chassis' to enclose the center of the rotor and force the air through the vanes, this promotes even cooling.

I want to run traction control in the future otherwise I would cut the abs sensor tab off and make for a better inlet.



I then added a lip that fits inside of the rotor ~1/8"


sorry for the potato pic, in a hurry to get these done


Squished a piece of 3" exhaust tubing and started hacking it to fit.






The angle of the dangle is super critical, you have to aim the outlet pretty much right on top of the tie rods and out towards the wheel as far as you can so you can still turn without tearing up the hose.


You'll notice there is a gap between the brake bracket and the backing plate. I almost sealed this up but decided to leave it as it will cool the caliper well. Might experiment with it later.



Again potato cam pics and bad lighting...... lock to lock




Again....in a hurry so I just stuffed the hose inlet into the openings left from my radiator ducting. I'll make a proper inlet that seals to the nose later.


So we'll see if the carbotechs turn to dust under the pressure of 200+hp.

 

Adding results from my build thread:

They didn't fade......ducts worked great. I was a good 5 seconds off the spec miata track record but I was carrying way, way more speed than any miata should, and then slowing more than a spec miata would as well. I would say I was pretty hard on them. A more experienced friend blew through a set of DTC-70's in his vette over the two days, so the course was pretty hard on brakes. I was bleeding off speed from 125 to 45mph into turn one, and again from 100ish to 45 in 4. As a comparison a SM would be around 105-110 into 1 and maybe 80mph through 4. I did burn through ~40% of the carbotechs, unfortunately it was the last 40% of the pads so I was done with one session left. I had another set of pads, but I was burnt too, so I loaded it up while she was still in one piece.

After event inspection I found tire clag inside of the rotor stuck to the vanes. So they are moving enough air to carry that rubber down a not smooth flex duct. I bled the brakes and was surprised that the fluid wasn't as dark as I thought it would be. Swapped on some G-loc (same compound as carbotech's) and was surprised when the squeel went away. The G-loc's use a solid pad, where the carbotechs had a dust groove. Hopefully I'll get back on track again next month.

 

Nice work.

Looks really good. I have no idea why most of us don't do the inner vent like yours....to much hard work maybe..

Another project to play around with....i must start using my welder soon!

 

Don't the rotors want to naturally flow from the inside to the out? Are you trying to force air the other way?

 

Looks like in to centre of rotor out to me....?

 

I think most people running ducts on Miatas have already gone with big brake kits using rotors on hats. Unlike a stock rotor, those typically have a bunch of holes between the rotor and the hat so I don't know if the enclosure idea would work or not. For example:



Also note that with the larger rotors the duct hole is pointing much more into the center of the rotor, rather than just at the rear face.

--Ian

 

Correct, I'm forcing air into the center out through the vanes. I can't see how air moves through a strait vane rotor otherwise. There's nothing about it spinning that promotes airflow. One of the biggest advantages of a big brake kit other than the thermal mass of the larger rotor is the fact you can get a curved vane rotor and get some air flow.

I keep eyeing a BBK of some sort but you're right most of them have a scalloped hat like that, I'm sure I could come up with a plate that blocked these holes but seems like more work. I'd like to think that even with the air leakage out the holes you would promote airflow through the rotor and cool the outboard face of the rotor some. I personally don't like blowing air on only one side of the rotor, good way to turn it into a cone and promote cracking.

 

Even with straight vanes, it's still a centrifugal pump. Directional vanes and ducts make a lot more airflow, though.

 

Turbos originally had straight vanes

 

Why not utilize fog bezels for duct, and then box/seal the airdam

 

Passenger fog feeds the oil cooler, driver's side feeds the turbo inlet. Otherwise that would make the most sense.


On the whole strait vane thing, centrifugal pumps rely on the fact the water/air/ECT. Enters where the vanes are big and exits in a single spot where the vanes are small. With the vaned area actually getting bigger towards the outside and the fact it's open 360 degrees I'm not sure how much of a pump it actually is. You got me thinking though, might try turning the rotor on the lathe to see how much air actually does come out through the vanes.

 

Sounds like a reasonable test.

 

Something I've always thought about doing. looks #neat.

 

Straight vane centrifugal pumps actually work fine. You usually see them in higher pressure, low flow applications. Straight vanes also allow the impeller (rotor in this case) to work when spinning either direction. That said, a curved vane is certainly more efficient.