All Things Mk5 > Performance Modifications
Brake Ducts
the bruce:
--- Quote from: rex on February 18, 2013, 09:44:05 am ---Yes, the area where the air exists is smaller, but the same amount of air travels through there.
Because the exist is smaller than the intake, the air will travel faster through the exist.
--- End quote ---
Unfortunately it will not be the same amount, Vlad. :sad1:
--- Quote from: rex on February 18, 2013, 09:44:05 am ---I am not sure this way really solves what I want to do... I want to direct the air towards the disc vanes / disc bell and NOT directly on the inner side of the disc.
--- End quote ---
Yes, of course. Directing the air flow into the bell is your major target, but the 2nd
one will be to get much air in as possible and even more so if you keep the shields
which inhibit the cooling of the rotors inner face.
That's why I suggested it that way keeping the full amount of air flow.
--- Quote from: rex on February 18, 2013, 09:44:05 am ---I agree, but the only reason to keep the dust/mud guard (shield) is that my car is is still a daily drive and a lot of dirt/dust will get to the discs and calipers...
--- End quote ---
I know. You won't need the shields in the summertime though. The better way would
be to remove them in the summertime (when your tracking) and fit them in the winter
if you feel a need. I didn't even miss them in the winter (you might know there's lots
of salt on German Autobahn).
--- Quote from: richwig83 on February 18, 2013, 05:50:40 pm ---It might make the air leave the pipe quicker but it will reduce volume of air flowing out the end. Which ones most important?
--- End quote ---
Agree. That's been my consideration. The air will accelerate at the narrow area, but
drag will increase at the same time (according to Bernoulli and Newton - continuity of
momentum). As a consequence there must be less volume in the end.
--- Quote from: rex on February 18, 2013, 06:42:28 pm ---IMO, the more air I can get into the rotor vanes and/or in the disc bell, the better.
--- End quote ---
That's indeed the point. I'm pretty sure with deflectors similar to what I suggested
you will get at least the same amount of air into the bell as you get with the one
you proposed (I believe even more). The 2nd benefit would be the disc face also
gets some air.
Keep in mind if you keep the shields the inner face of the rotor will get hotter than
the outer face causing 'shielding' or even warping.
At higher temps in the 500° C area heat radiation plays a major role compared to
lower temps. With a dust shield on one side the disc will not just get hotter, it will
also have a very unequally temperature distribution.
DaveB@Vagbremtechnic:
Some good work Rex, I can't help but think after enjoying your videos that you've outgrown the NQS kit and should maybe buy an AP offering.
Some thoughts....
Standard discs are straight vaned and not directional and curved.....this means they will distribute any air that's introduced in that area but they are ineffective at creating a low pressure area behind the disc to encourage flow....they blow but don't suck simply put
THIS WILL BE THE BIGGEST ISSUE....some directional discs without ducting will work similarly to straight vane discs with ducting
ANY cooling even the wheel arch mod is better than none
Any air introduced should ideally find itself behind the hub area only, only cool the back ace directly if you ave front face cooling too this can be via a device on the wheel or via vents milled onto the back of the bell which line up with the rotor vents
Ditch the dust shields
Regarding ducting I tried every which way to get the phaeton ducts to work, I ended up grinding that much of them away they didn't resemble ducts anymore. John from rally tech near us then decided to take pity on me after having a laugh at my creative skills and suggested a scoop/shield idea straight from the WRC cars that he does all the carbon for.
They've moved away from ducting generally and started using scoops, they're lighter and less complicated.
So i find myself with a 2011 TTRS front subframe complete down the side of my house which growls at me every time I walk my dog because I haven't done anything with it for three month, plan is to develop an integrated scoop/shield in carbon that's simple to bolt on ........problem is Rex it can only work from about 330-390mm rotor size.
I wouldn't worry too much about the volume of air and Mr Bernoulli this isn't Formula 1 and if it got to that stage where he featured then the pads would have given up 2 miles ago and all the rubber seals on the Calipers would have melted.
There also doesn't seem to be much point in doing anything complex to straight vane discs.....its like spending a fortune on developing a turbo for a 650cc engine when you can just drop in a 2.0 and go,just as fast......when you turbo (duct) the 2.0 engine (directional rotors) is when you will see the results....make sense?
AP have some great pics of their GT and LMP ducting recommendations COMPLETELY impractical on a road car but they steer the thought process I'll try to,post them up
DaveB@Vagbremtechnic:
From AP
--- Quote ---A good source of cooling air should be supplied preferably through the upright 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 considerably 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.
--- End quote ---
I'll find some more....
rex:
Thank you very much guys for your information and implication! :notworthy:
There are some interesting thoughts...
1. Dust shields...
Holger, I know you always said to ditch the dust shield and for performance you are 100% right!
a. As far as I know, it is impossible to take the dust shields off the car without taking the disc down (and the caliper). Although this is not a complicated operation I prefer not to take the calipers off the car 2 times per year.
b. The dust shield also provide a good base for mounting the air inlet. Without them I would need to create a bracket to fix the air inlet.
c. The problem with the dust/dirt. In the pictures above you can see the dust/dirt accumulated on the dust shield. Wouldn't it be a problem if all this dirt entered the caliper pistons?
I will look into these problems closely too see if there are simple solutions.
I want to buy a dust shield today to have the hub assembly complete and see if I can solve point a.
2. Buying a new brake assembly (like AP).
Unfortunately my finances are very low and the nqsbbk is very very close to being perfect for my car. Please remember I only have 160bhp and down Hungaroring straight I reach 170kph apposed to fuscobal's 210kph (I think). I abuse the brakes (aka braking like I should) for 7-8 laps at a time and, only after 3-4 rounds, the pedal gets softer. This is why I want to improve the brakes slightly and I do not expect miracles from the brake ducts. Dave, from what you said, I understand that any cooling is good and that I should expect at least some improvement. Did I understand correctly?
Also the nqsbbk fits behind 16 inch rims that no bbk does (for the mk5), relatively cheap discs, pads and maintenance. So, if I can improve the brake fade slightly there are no reasons to go for AP.
3. Having directional vanes or not...
--- Quote ---some directional discs without ducting will work similarly to straight vane discs with ducting
--- End quote ---
This means that ducting is doing something good for the OEM 312 discs...
By the way Dave, did you create that 315x25 AP rotor for the nqsbbk kit?
4. These ducts with other BBK...
Am I correct into thinking that the brake ducts as described above are useful for any BBK (AP PRO 5000 for example)? The way I "designed" these brake ducts they will fit the 312 rotor but can be fitted to any other rotor larger than this.
So if I create these brake ducts I can change the BBK and not have to start from scratch...
5. For street/winter use I intend to "disable" the brake ducts. There are 2 ways:
a. put something over the brake duct intake (from the fog grille).
b. put something to block the air next to the hub.
I am not sure which way I will go but, I hope I can created a cover for point a. Please keep in mind that I want the solution to be nice and tidy and I want to make it flexible so that I can take it off/ put it on in less then 5 minutes.
P.S. About making something complicated, I have some time to kill... And I also find it very rewarding actually doing something by myself for the car and not buying parts.
Any more thoughts/suggestions are welcomed and, again, than you guys very much for your implication so far!
the bruce:
First of all, I agree with Dave. I remember reading AP's advice on brake ducting some
time ago. Of course Bernoulli's principle still applies to fluid dynamics, even in F1.
--- Quote from: rex on February 19, 2013, 07:53:32 am ---Thank you very much guys for your information and implication! :notworthy:
There are some interesting thoughts...
1. Dust shields...
Holger, I know you always said to ditch the dust shield and for performance you are 100% right!
a. As far as I know, it is impossible to take the dust shields off the car without taking the disc down (and the caliper). Although this is not a complicated operation I prefer not to take the calipers off the car 2 times per year.
b. The dust shield also provide a good base for mounting the air inlet. Without them I would need to create a bracket to fix the air inlet.
c. The problem with the dust/dirt. In the pictures above you can see the dust/dirt accumulated on the dust shield. Wouldn't it be a problem if all this dirt entered the caliper pistons?
I will look into these problems closely too see if there are simple solutions.
I want to buy a dust shield today to have the hub assembly complete and see if I can solve point a.
--- End quote ---
a) Right, you'd need to remove the caliper first, then the disc.
b) Yes, indeed. That's why I suggested cutting the shield to a minimum to just being
a kind of 'bracket' for the duct.
c) Guess not.
I'd give you my old dust shields for free. I shurely will never refit them. Shipping will
exceed the cost of new shields though.
--- Quote from: rex on February 19, 2013, 07:53:32 am ---2. Buying a new brake assembly (like AP).
Unfortunately my finances are very low and the nqsbbk is very very close to being perfect for my car. Please remember I only have 160bhp and down Hungaroring straight I reach 170kph apposed to fuscobal's 210kph (I think). I abuse the brakes (aka braking like I should) for 7-8 laps at a time and, only after 3-4 rounds, the pedal gets softer. This is why I want to improve the brakes slightly and I do not expect miracles from the brake ducts. Dave, from what you said, I understand that any cooling is good and that I should expect at least some improvement. Did I understand correctly?
Also the nqsbbk fits behind 16 inch rims that no bbk does (for the mk5), relatively cheap discs, pads and maintenance. So, if I can improve the brake fade slightly there are no reasons to go for AP.
--- End quote ---
No doubt - ANY cooling is good. It's hard to tell specific numbers, but as a ball-park figure
I'd expect 50° C lower peak temperatures with proper cooling and a similar amount with
directional rotors.
The softer pedal may come from both fluid boiling and rotor distortion by some amount.
Again, the dust shield prevents the inner face of the rotor from being cooled equally to the
outer face.
A cooler running rotor will also cool the pad better and heat up both caliper and fluid less.
--- Quote from: rex on February 19, 2013, 07:53:32 am ---3. Having directional vanes or not...
--- Quote ---some directional discs without ducting will work similarly to straight vane discs with ducting
--- End quote ---
This means that ducting is doing something good for the OEM 312 discs...
By the way Dave, did you, create that 315x25 AP rotor for the nqsbbk kit?
--- End quote ---
From what I remember Performance Friction made a small number of 312x25 discs for AWE.
Sadly they stopped making them. AP Racing still makes a "Strap Drive" kit for R32 & S3:
http://www.apracing.com/product_details/road_car_upgrades/oe_replacement_disc_kits/strap_drive_kits_and_system/vw_golf_mk5.aspx
--- Quote from: rex on February 19, 2013, 07:53:32 am ---4. These ducts with other BBK...
Am I correct into thinking that the brake ducts as described above are useful for any BBK (AP PRO 5000 for example)? The way I "designed" these brake ducts they will fit the 312 rotor but can be fitted to any other rotor larger than this.
So if I create these brake ducts I can change the BBK and not have to start from scratch...
--- End quote ---
Certainly it'll help with any BBK. Very large BBKs may even make it easier to fit a duct
between hub and caliper instead of the back side of the hub.
--- Quote from: rex on February 19, 2013, 07:53:32 am ---5. For street/winter use I intend to "disable" the brake ducts. There are 2 ways:
a. put something over the brake duct intake (from the fog grille).
b. put something to block the air next to the hub.
I am not sure which way I will go but, I hope I can created a cover for point a. Please keep in mind that I want the solution to be nice and tidy and I want to make it flexible so that I can take it off/ put it on in less then 5 minutes.
--- End quote ---
To me a) seems to be most practical. I even guess blowing some clean air to the rotor
may help to keep it free from salt and water. Keep in mind it's the tyre swirling up
water and salt.
--- Quote from: rex on February 19, 2013, 07:53:32 am ---P.S. About making something complicated, I have some time to kill... And I also find it very rewarding actually doing something by myself for the car and not buying parts.
Any more thoughts/suggestions are welcomed and, again, than you guys very much for your implication so far!
--- End quote ---
I guess we already covered most of the theme. Ducting is good, ducting + directional rotors
is better and a properly vented BBK is best. Now you know how to design the ducts correctly,
but however you do it - it will help lowering rotor (and pad + caliper) temperatures.
It's all right as long as you do any venting. :wink:
BTW,
Vlad consider to get some downforce as Fuscobal does. Your car will run slower on the straight
and faster on the corners. >> Less brake effort, less heat. :signLOL:
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