We did the Fog Light brake duct solution
on our NB1 (the 99 racer). It worked great for us in the great white north…
All prices are by memory but you get the idea... total ~ $240 with shipping from various suppliers.
$20 ebay fog light rings,
$20 Aircraft Spruce 2 1/2" duct flanges (an Emilio recommended supplier), ALUMINUM FLANGES FOR DUCTING from Aircraft Spruce
$30-60 2 1/2" air ducting – a wide range in prices based on temp resistance and quality...
$125 Aluminum brake duct backing plates from ISC, Miata power train
$20 hose clamps, wire ties, screws & nuts, aluminum strip, other stuff.
I merged ideas from 949 (brake cooling duct running - attaching it to the sway bar and end links), ISC, plus I like the fog light rings to keep everything clean. Alternately, forward facing ducts in the rad air inlet should also work…
ISC Brake ducts:
Like – they direct the cooling air at the center of the disk, wheel bearing and the inner pad / caliper. The design forces cold air into the center of the disk for maximum vane effectiveness. Inside face of the disk is not covered so it benefits from any additional air that happens to pass by the 9” 6UL wheel.
Don’t like – the lower backing plate rubs on the lower ball joint boot. I reshaped this for more clearance and had it tig welded. You also have to cut off the wheel speed sensor boss from the spindle so no ABS. Our race regs do not allow ABS so not really an issue for us.
Effectiveness – on a typical summer day for us (75-80 F) we had to tape off about 1/3 of the air inlet as the front brakes were running too cool vs the rear (without the tape we had to continue to adjust the bias throughout the race since the front brakes never really heated up however the rear brakes did changing the front rear balance). At about 95 F or so, it worked fine without tape.
The car has stock NB1 brakes & PF97 pads. No inner fender liners, no brake backing plates front or rear.
Previously configuration WITHOUT air ducts - The front rotors would glow red on one or more braking zones per lap (depending on track). Calipers got hot enough to discolor 750F caliper paint at the outer pad. Engine near stock (RB header + 2 1/2“ exhaust).
The fog light entry and 2 ˝” ducting worked for us, with more HP & larger brakes better ducting & more air flow may be needed.