Making functional RS brake ducts
11-27-2015, 12:01 PM
#16
Race Car
^^ yes agreed JA ... lots of threads talking about this since the 991 RS
... maybe venting direct to disc means less lift as air isn't entering the well, rather being forced out via the rotor vanes ... (Ahab might know more?)
... maybe venting direct to disc means less lift as air isn't entering the well, rather being forced out via the rotor vanes ... (Ahab might know more?)
11-27-2015, 01:08 PM
#17
Rennlist Member
Not sure on the 964, i will be adding functional ducting to mine.
However if you look at the design on the 997.1 cup (which is about identical to my 997.1RS, i have many of the same cup parts on this car)...
They have:
Huge duct in fender liner that takes air from front bumper, about axle height with a scoop that directs air to the center of the rotor
There is a shield that captures that air and directs to the rotor
There is a scoop on the lower air dam/bumper that directs air under the car to a scoop on the leading control arm directed at the rotor
The cup cars also run a "flick" on the leading edge of the front fender to reduce pressure in the fender (I have these on my car, i'm sure they would fit a 964 too, motorsport part that simply screws to the fender lip.
My RS has no brake fade, brakes run spot on to temperatures specified by Brembo (verified with temperature paint and strips) and the car doesn't push at all... of course the fronts are massive 380mm rotors with 6piston calipers...
Now on the 964, haven't had that out on track YET, but i suspect that i'd worry about brake cooling and temperatures first before wrong about air and lift on the front of the car.
So if you really want to check, just get some brembo brake temp paint, put it on the vanes of the rotor, on the face of the rotor (the edge next to vanes, top side where pads don't touch), put some on the metal on the pads, and use a strip on the caliper.
For race pads:
Brake caliper Paint flashes/turns to white:
-- Green: 430C/806F
-- Orange: 560C/1040F
-- Red: 610C/1130F
Once they reach the specified temp range, they oxidize which turns them green/red: white or an orange/off-white (yellowish tint). If they reach the peak temperature.
Caliper Temp: 140C/284F - 160C/320F, max 180C/256F
Rotor Temp: 450C/842F - 550C/1022F (in pit lane if measured by IR).
Max: 650C/1202F (measured by rotor paint)
Basically we want to flash the green paint and for the most part be in the orange paint range if applied on the disc. We can turn the red paint to white on the rubbing surface of the disc but not in the disc vane itself.
Summary:
On Vanes - Flash Green and into Orange, no Red
On Suface - Flash Green, Orange, Red is OK
However if you look at the design on the 997.1 cup (which is about identical to my 997.1RS, i have many of the same cup parts on this car)...
They have:
Huge duct in fender liner that takes air from front bumper, about axle height with a scoop that directs air to the center of the rotor
There is a shield that captures that air and directs to the rotor
There is a scoop on the lower air dam/bumper that directs air under the car to a scoop on the leading control arm directed at the rotor
The cup cars also run a "flick" on the leading edge of the front fender to reduce pressure in the fender (I have these on my car, i'm sure they would fit a 964 too, motorsport part that simply screws to the fender lip.
My RS has no brake fade, brakes run spot on to temperatures specified by Brembo (verified with temperature paint and strips) and the car doesn't push at all... of course the fronts are massive 380mm rotors with 6piston calipers...
Now on the 964, haven't had that out on track YET, but i suspect that i'd worry about brake cooling and temperatures first before wrong about air and lift on the front of the car.
So if you really want to check, just get some brembo brake temp paint, put it on the vanes of the rotor, on the face of the rotor (the edge next to vanes, top side where pads don't touch), put some on the metal on the pads, and use a strip on the caliper.
For race pads:
Brake caliper Paint flashes/turns to white:
-- Green: 430C/806F
-- Orange: 560C/1040F
-- Red: 610C/1130F
Once they reach the specified temp range, they oxidize which turns them green/red: white or an orange/off-white (yellowish tint). If they reach the peak temperature.
Caliper Temp: 140C/284F - 160C/320F, max 180C/256F
Rotor Temp: 450C/842F - 550C/1022F (in pit lane if measured by IR).
Max: 650C/1202F (measured by rotor paint)
Basically we want to flash the green paint and for the most part be in the orange paint range if applied on the disc. We can turn the red paint to white on the rubbing surface of the disc but not in the disc vane itself.
Summary:
On Vanes - Flash Green and into Orange, no Red
On Suface - Flash Green, Orange, Red is OK
11-27-2015, 05:36 PM
#18
^^^^ very good info. ^^^^
I've got some experience of brake cooling but only with carbon/carbon discs and pads. All done in a very complicated (as in mind boggling) way so as to eek out as much aero performance as possible then brake cooling is secondary
In a nut shell it all about directing air flow to cover the centre of the disc through the vanes and radially out, pad to disc contact area the and the disc faces.
Best place to pick up air is the high pressure areas on the front bumper, sort of about where RS ducts are or if you want stealthy the outboard corners of the front bumper opening. The high pressure area inside the wheel arch won't have a high flow rate and will be a hotter temp. than ambient.
I found this the other day, right diagram on page 59 explains the principle far better than I could explain with a few words
http://www.apracing.com/%5Cdrawings/...ke%20Discs.pdf
I'm pretty sure most lightened 964 cars don't need Big Red's to stop well on trackdays, just Big Air ducted to the right places.
I've got some experience of brake cooling but only with carbon/carbon discs and pads. All done in a very complicated (as in mind boggling) way so as to eek out as much aero performance as possible then brake cooling is secondary
In a nut shell it all about directing air flow to cover the centre of the disc through the vanes and radially out, pad to disc contact area the and the disc faces.
Best place to pick up air is the high pressure areas on the front bumper, sort of about where RS ducts are or if you want stealthy the outboard corners of the front bumper opening. The high pressure area inside the wheel arch won't have a high flow rate and will be a hotter temp. than ambient.
I found this the other day, right diagram on page 59 explains the principle far better than I could explain with a few words
http://www.apracing.com/%5Cdrawings/...ke%20Discs.pdf
I'm pretty sure most lightened 964 cars don't need Big Red's to stop well on trackdays, just Big Air ducted to the right places.
11-28-2015, 12:38 AM
#19
Race Car
DISC COOLING.
A good source of cooling air should be supplied preferably through the up- right to the disc throat. A typical venting cross section of 100cm2 (16in2) is usually sufficient. The pick up should preferably be in an area of clean high pressure air flow and the ducting should be arranged to avoid sharp bends or changes in section which may choke the air flow. Careful design of the Mounting Bell is important in achieving effective disc cooling and avoiding problems. Typically 80% of the airflow should be directed up the disc vents and 10% up each face of the disc. This ratio can vary consider- ably in practice but it is important that both disc faces are cooled equally by adjusting the air gaps. Unequal face temperatures can lead to disc distortion and a long pedal. Lightening holes in the bells should be avoided as available cooling air can be lost without cooling the disc.
Thanks Cpt! SW's point also covered. Not so simple to get air to both faces and doesn't mention the 'high pressure inside tire well' idea much.
A good source of cooling air should be supplied preferably through the up- right to the disc throat. A typical venting cross section of 100cm2 (16in2) is usually sufficient. The pick up should preferably be in an area of clean high pressure air flow and the ducting should be arranged to avoid sharp bends or changes in section which may choke the air flow. Careful design of the Mounting Bell is important in achieving effective disc cooling and avoiding problems. Typically 80% of the airflow should be directed up the disc vents and 10% up each face of the disc. This ratio can vary consider- ably in practice but it is important that both disc faces are cooled equally by adjusting the air gaps. Unequal face temperatures can lead to disc distortion and a long pedal. Lightening holes in the bells should be avoided as available cooling air can be lost without cooling the disc.
Thanks Cpt! SW's point also covered. Not so simple to get air to both faces and doesn't mention the 'high pressure inside tire well' idea much.