Brake duct tubing size - changing dia mid-run?
02-23-2018, 01:30 PM
#1
Nordschleife Master
Thread Starter
Brake duct tubing size - changing dia mid-run?
Ok so it's been a long time since I had fluid dynamics classes.... and don't remember any of it.
Looking at doing brake ducting on my Cayman. Found a guy doing some cool custom pieces that convert the fog lights to tubes.
He's suggesting using 1.5" tubing... merely from a "fit" perspective.
I have Olsen Motorsports front backing plates (basically custom front backing plates that have scoops on them) - in addition, these ducts have provisions for mounting up ducting. They are set to collect 2.5" tubing.
I know as I change tubing diameters, it will change how the air flows. I'm concerned I may cause the air to stall..... I guess, maybe I'm overthinking it, but is there any practical examples/advice/evidence out there to suggest that, if I run 1.5" tubing for most of the run, then merely adapt to the 2.5" at or near the mount on the rotor... that I'll cause issues or make the whole concept ineffective?
Looking at doing brake ducting on my Cayman. Found a guy doing some cool custom pieces that convert the fog lights to tubes.
He's suggesting using 1.5" tubing... merely from a "fit" perspective.
I have Olsen Motorsports front backing plates (basically custom front backing plates that have scoops on them) - in addition, these ducts have provisions for mounting up ducting. They are set to collect 2.5" tubing.
I know as I change tubing diameters, it will change how the air flows. I'm concerned I may cause the air to stall..... I guess, maybe I'm overthinking it, but is there any practical examples/advice/evidence out there to suggest that, if I run 1.5" tubing for most of the run, then merely adapt to the 2.5" at or near the mount on the rotor... that I'll cause issues or make the whole concept ineffective?
02-23-2018, 02:11 PM
#2
Should work okay. The larger diameter will cause the average air velocity to drop, but the total air volume delivered will actiually be higher ( slightly) than if you ran 1.5 inch tubing the entire way.
Of course, larger tubing the entire way would work better, if possible.
Of course, larger tubing the entire way would work better, if possible.
02-23-2018, 02:32 PM
#4
Nordschleife Master
Thread Starter
02-23-2018, 04:16 PM
#5
Addict
Rennlist Member
Rennlist Member
I know as I change tubing diameters, it will change how the air flows. I'm concerned I may cause the air to stall..... I guess, maybe I'm overthinking it, but is there any practical examples/advice/evidence out there to suggest that, if I run 1.5" tubing for most of the run, then merely adapt to the 2.5" at or near the mount on the rotor... that I'll cause issues or make the whole concept ineffective?
02-23-2018, 09:02 PM
#6
Rennlist Member
I'm wrapping mine up tomorrow will post pics in my SPC build thread (Cayman FORUM) I plan on putting 2.5 naca ducts in the radiator shrouds. I think there is enough room..
02-23-2018, 10:51 PM
#7
Rennlist Member
Little knowledge of fluid dynamics here but I would assume the veining within the rotors creates a bit of a draw on the system as well.
Have a pair of AIR fog light ducts with hose and backing plates on my 951 with no complaints...but no data to support.
Have a pair of AIR fog light ducts with hose and backing plates on my 951 with no complaints...but no data to support.
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02-26-2018, 03:35 PM
#8
Rennlist Member
You’ll be fine. The mass conservation principle assures you that with changing the diameter, the mass flow rate will be constant, ie the same amount of air that went into the pipe will come out of the pipe regardless of a diameter change. If the pipe were very very very small you’d have boundary layer friction that slows it down but that should not be your concern.
yes, the veins are being fed by incoming air flow. its effectiveness is based on the density of the air it has access to. faster you go, the higher pressure the air is at the inlet area of the brake rotor annulus.