Hey all. Looking for some input regarding brake duct options for my NC.

I'm looking at adding ducting as I'm about to add a turbo to the car. Target WHP is around 280. Car currently weighs just over 2,600lbs with me in it. Current brake setup is a Keisler Automation BBK up front: Wilwood 4pot Superlite Calipers and 12.7" RX8 Sport front rotors. Stock rear brakes, SS lines all around, upsized 1" master cylinder from an Infiniti G37, Hawk DTC60 pads front and rear for track use.

There aren't any off the shelf ducting kits available for the NC aside from the AWR kit, which uses 2.5" tubing regardless of whether stock NC rotors or the larger 12.7" RX8 rotors and backing plates are used. I remember 949Racing previously saying that 2.5" ducts don't make a meaningful enough effect on brake cooling to be worth installing at all. My question is: Would I see any benefit from using 3" ducting at the air dam inlet, then tapering to 2.5" where the ducting meets the rotor backing plates? My only other idea was to try and find some backing plates with a 3" duct outlet for a 12.7" rotor, then drilling them to fit the mounting holes on my wheel knuckles. I'd rather not go too far down a rabbit hole with this, though, as I have plenty of other things to do on the car as well haha.

As always, any feedback from you guys is appreciated. Thanks!

 

AWR's blow on the inside rotor face only so they are mostly useless...

Im running Foxhole Fabrications on my NB, but I dont think he makes anything for the NC.

 

I know Emilio at some point posted that 2.5" ducts had not nearly enough airflow with the typical bends required to duct to brakes from the bumper - and that 3" was the minimum to have a profound effect.

That said I'm running 2.5" on my car with the AWR style plates and I definitely think they do something (judging from how dirt/water is pushed though the ducting air is definitely being pushed through). Far from optimal though, from what I understand.

 

Copy that, gracias guys. Yeah, I remember 949Racing having a comment about the airflow aim as well. And that what you really want is to have the ducts blowing air toward the hub so it flows through the rotor vanes.

Nate, that's the exact anecdote I remember from Emilio. I gotta imagine 2.5" still does something. Maybe I'll rig those up and actually get some temperature strips to measure before and after effects.

I'm starting to think that making a custom backing plate with a 3" duct inlet would be the optimal answer here. God, I gotta start learning how to weld one of these days...

 

After some digging through multiple forums, I decided to order a pair of C6 Z06 front brake ducts and the AWR backing plates. One user on M.net used a set for his project a while back and it looks like they fit gloriously and silence the fear of front wheels rubbing through the tubular ducting. I'm no engineer but it looks like they'll provide smoother airflow too than corrugated tubing too. The outlet of the Z06 ducts is 2.5" to match the AWR backing plates, but the inlet is 4 1/4". Not sure if I'll get 4 1/4" mounting flanges for the airdam or something smaller (3.5"?) to reduce unnecessary drag.

I saw an old thread where @sixshooter used these backing plates or something similar and blocked off the outer part of the duct facing the rotor face to funnel air towards the hub instead. Think I'm gonna try that too.

 

Those look sweet, I wonder if I could make those work with my setup. Either way, keep us posted!

 

For sure smooth will beat corrugated, on a like-for-like basis. How much closer to 3in they make a 2.5 flow I don't know.

I have just got a BBK, and cooling is on my agenda. I like the boxmount idea of feeding the centre of the disk, that is the inlet area of the vanes.

 

I'll keep the thread updated for sure! Parts are all slated to land Tuesday. I probably won't attempt to install them before leaving for the track on Thursday. Probably. I do have to swap in my track pads at some point anyway, though...

Yeah, the SM/Boxmount cooling ducts are really well-thought out. I don't have any numerical datapoints, but I can say for certain that the pads on my last car lasted substantially longer after adding the ducts.

 

I'm not super convinced things are working well in my car, but I used these: https://www.flatironstuning.com/veru...ake-brake-duct

(my car is an LFX RX8 that tears through brake pads).

I'm using the AWR 2.5" backing plate, but it's 3" hose from the front bumper to the Verus pancake duct.

Mostly contributing to just add to the product knowledge. I assume with 2.5" it's not super effective and my brake pad life seems to bear that out.

 

Yo, thanks for chiming in dude. Good datapoints for sure. What calipers/rotor size are you running? I'm assuming some kind of 4 piston with the larger Sport rotors?

 

I had the Keisler setup but went to the Sakebomb wilwood kit with 325mm x 32mm rotors, after maybe 4 track days with the Keisler kit and stock rx8 rotors. I had a set of R12s with the keisler kit that lasted 2 track days, and then some PFC01 (iirc) that also lasted 2 days. Then i switched to SBG kit. I've had ducting the whole time, but I figure it's not working particularly well because of the path (using the foglight holes in the rx8 bumper) and because of the 2.5" size.

Since then I've tried Ferrodo 3.12s, Cobalt XR2s, EBC SR21s, and something else that I can't remember. I just slapped in some R16s so we'll see how these fair. I get 3-4 days from a set of pads. I'm not running time attack -- it's 5 or 6 sessions at 20min ea.

I'm chalking it up to Heavier-than-I-want-car with small-than-I-want brakes being driven like an *******.

Mostly just commented because I'm waiting for you or someone else to develop some 3" backing plates

 

Dang, you're MURDERING pads haha. Don't know how I missed the Sakebomb 325mm brake kit. I've seen their 323mmx24mm RX8 rotor kit but not the bigger one. Must be new.

I'd also like for someone to develop some 3" backing plates lol. I'm anything but a master fabricator. I should go back and check the Kaiko SuperMiata NC thread again - I know they were working on a proto BBK for that car. Wonder if they're running ducts..

 

This kit here:

https://www.sakebombgarage.com/wilwo...brake-kit-rx8/

 

https://www.miataturbo.net/aerodynam...-ducts-102164/

this was one of those threads about blowing on the face. I don’t think it’s just an efficiency issue. Blowing air through the center vanes would mean the cooling effect is better distributed through the rotor - both sides.

if the vanes are bonded to both sides of a rotor, but only one, external side is getting cooled, differing expansion rates may be causing the failure. I’m just spitballing.

 

I made my own brake ducts with 3" inlets on an NB Miata. I patterned them off a kit I already had installed that had 2.5" ducts. I used aluminum, brazed and riveted the 3" inlets. Had one or two track days on them, and they held up fine.

I taught myself to braze, it's not particularly hard, and did hold up OK on track.

New ones on top.

 

No ABS?

 

No ABS.