RE: ur last post olddreagger

I measure all over the brake...have found that spot always be the hottest, so I use it as a reference for temp reduction. Brake/wheel is a wholistic heatsink system, cooler anywhere cools everywhere by thermal conduction. I'm trying to reduce the overall system temp by cooling where I can... introducing cooler air pointed at the existing factory shield 'scoop' serves the purpose without the cost and complication of the next step, a backplate. For my use (non-racing) I have no need for that considering current results. FYI: 980 degree paint http://g2usa.com/brake_caliper_paint.shtml

 

Spin--that temp referance makes sense. Good data you are collecting. Thermal conduction cooling happens but often thats not fast enough. Much more efficent to direct that air to the disc itself. I think I have thought of a way to see some effect from your mod. Tell me what you think.
Just hook up an external temp sensor to a stable point in the wheelwell as close to the wheel as you can thats stable/firm. Run a session--measure from inside the car what the wheelwell temp is during the session with your mod cap on. Then do another session with the cap off. See if the wheelwell temps change. This is not a completly accuate way of measuring true temps but it would be a cheap way of seeing any large differance. Your can get one of those inside /outside temp monitors from Home depo for less than $10. I did this on air intake temps and it gave some crude data. Be interesting. Thoughts? I'm listening to you and i hope i am wrong--butttt I dont think so at present.

I have a kinda of a smaller version of your diy on my car. Except it is not for the brakes. Its to help airflow through the oilcoolers by creating a vacumn behind them (at speed of course). So far even on a track day in which ambient temps are over a hundred --my oil temp has never gotten over 230F nor water temp(somewhat affected by the oil temps) over 210F.
DSM I dont think that the wheelwell air is stagnant. If it was then you are right. But I dont think it is. The brakes would never cool if it was. Lots of heat (LOTS) is generated by the brakes when on the track. If the ww air was not sufficently moving our brakes would not last 3 laps.
olddragger

 

You going to share that DIY with the rest of us?

 

Guess we'll just agree to differ . The mod works to my satisfaction, and I'm happy. Spending more t&$&energy on it will have to wait til my next life. No problem, each to their own. If you ever get to doing something like it yourself, let us know your findings. Cheers.

 

Understand. If you are satisfied with it then that is all that matters. Intersting sharing of views though. If you are ever down Ga way let our grp know.
olddragger

 

ayyayaayyayayayayy

 

Ducting won't do anything unless there is a way to get all that air out from the wheel well, otherwise it will just stack up in there...

 

Little bit of an over-statement IMHO, i mean after all you have the wheel spining and thats going to move the air around there quite a bit, not to mention that you have the brake vents directly behind the wheel well.

Moreover, i did a brake duct diy BlueRen, shot it with a pyrometer and got results similar to spin9k something like a 150deg drop, heres my thread: https://www.rx8club.com/series-i-do-yourself-forum-73/diy-brake-cooling-ducts-96296/

 

And when the air stacks up, the pressure will increase. When the pressure increases, Pv=nRT tells you that the temperature goes up. Since the air stacks up forever, the pressure goes to infinity, and thus so does the temperature!

Don't put ducts to your wheels! Your brakes will overheat and melt from all the pressure!

 

I didn't say that there was no way for the air to get out little by little, i was trying to imply that the "ducting" might be better served on the back of the wheel well...you would probably see MORE of a temp drop that way. Not to mention that your ducting setup completely circumvents the Gurney flaps in front of the wheels.

 

The flaps are there so that the front wheels have less windresistance against them at high speed, i am doing nothing by sticking another object infront of it other then assisit it to block more air from hitting the front wheel.....

EDIT: if you mean that im having air hit the front of the wheel by scooping it up, im not, the duct is aimed at the brakeshield/rotor assembly and at most is hitting the sidewall of the tire during a hard turn.

Next time you drive your car hard feel the brake vent behind the front wheels you'll notice that the air their is significan't hotter as engine and brake heat are vented though there.

 

I'm not trying to start anything but if you are scooping up more air and ducting it behind the wheel, with no way of extracting that increased influx of air, you will be creating a situation where pressure builds up. Your system would work more efficiently with an added "exit".

The flaps direct the air down and then under the tire, so by taking some of that air before it is redirected under and instead moving it behind the tire, there is necessarily some build up of pressure. I also thought that the vents behind the wheels were for engine compartment heat extraction only, but i could be wrong there.

 

Anyone just remove the dust shield from the disc? I think that may help more than uncommitted air toward the disc at speed. Key words here is "at speed". At relative low speed this mod probaly does have some benefit. Some is better than none.
Just take the dust cover off--you will get more cooling.
olddragger

 

The wheel has at least 1 sq ft free, open area. Any air you push into there will flow right out.

Pressure extracts itself. You don't have to pull something out if you're pushing it in. Yes, an exit duct would increase the total flow, but this is like saying two dollars is more than one. It doesn't mean the first dollar is worthless.

 

It isn't worthless, but I would say a 100% increase (from 1 to 2) is nothing to sniff at...

 

sniff

 

wise acre...

 

Both threads on ducks are in the right direction, but fall short. I used to track a 911 and I had installed a ducking system that had a special backing plate that tubing was attached to. Air was forced through the center of the rotor creating equal cooling to both sides of the rotor. No one is making such a kit for the 8's yet. I am trying to convince Cam at Pettit to fabricate one for my track car. With the backing plates removed front and rear, but no additional ducks yet, I am seeing temps in the 900 degree range fronts and rears both. Used the temp paint that yields different colors to show range. Admitted I run very hard, but these temps have to be brought down. Tired of cracking rotors. I have stoptech on front and factory on back. Use stoptech sloted rotors on all wheels. If anyone knows of someone working on a backing plate cooling system, please let me know

Jay
Instructor with NASA, BMW CCA & POC

 

Not to be a jerk, but isnt' that cracking a common problem with stoptech rotors in track situations?

 

Speedsource has backing plates for the 8 with integrated inlets for the ducts. I think TeamRX-8 has talked to them/seen them. I'm not sure they will fit my application...so I'm hoping that Team will try it out first...problem is there is no incentive fo him to do it for Autocross......

 

You might check w/Speedsource. I think they use a backing plate with air DUCTS (not ducks lol!). Even without the backing plate, some compromises are less so than they may appear. Unfortunately they are necessary on a street legal car like I have because I don't want to strip it.

I tried to figure a way to have backing plates, but could not find the wiggle room in the wheel well. It's damn tight there, esp. w/9.5" wheels. Only way it appears possible, in a true race stripped car is coming in from the engine bay, going down the suspension a-arm w/the ducting to the backing plate. I would guess anyone that does it, does it like that.

Using my duct method, here's a couple pics that show how I believe I'm providing improved and yes, almost equal cooling, to both rotor plates. First, and a big part of the plan - RB 2-piece rotors center-mount technology to provide air inlets to cool internal vanes on BOTH inboard and outboard faces simultaneously. (Full technology description here http://www.racingbrake.com/main/technology.asp) So right away, the brake shield air-gathering vane at least provides air to three rotor surfaces (2 sides inside rotor face, 1 internal side outside rotor face) and is a significant cooling improvement on the OEM solid version.

I tried to take some pics to show how the ducts I made were constructed to at least point directly at the air-gathering vane on the shield to inhance air flow there. Some disagree on the effectiveness of the duct's air column getting to the shield, but there is no doubt it at a minimum increases air flow through the wheel well area. And I maintain it does a lot more by sending a high-speed column at the brakes.

As for proof of concept, 700+ full tilt brake cycles I performed at Mt Tremblant over 3 days, 3.5 hrs track time, w/NER Porsche Club with no fade evident speaks for itself IMHO. It certainly is not the equal of a true race ducting setup, but it does the job for HPDEs extremely well, if that's what you're looking for (not sure, but if so great!)

pic1 - Looking in through the spokes at a light in the duct itself]
pic2 - A closeup showing the duct and the rotors w/center mounting allowing air to enter at the hub and be expelled outward internally.
pic3 - Showing the air-gathering vane area and it showing through the vent at the hub area.

 

cracking is a problem caused by heat in the range that I am running. I've cracked stoptech, factory and another brand that I don't even now who's it was (most recent on a rear set). I've actually found that the stoptech's have lasted longer. I have problems with the rears cracking where the rotor is the thinest. To balance there is one area usually cut out on the rear side near the hub.

I will give speedsource a call or stop by their shop. It is about 45 minutes from my business and less from my home. Thanks for the heads up.

Jay

 

^^ check them out and report back.....I couldn't really get the skinny over the phone on wether they will fit the larger RB rotors or not.....

 

Dannobre:

Spoke to Sylvan yesterday. His shopped designed the the brake cooling backing plates for the rotors but sales are only through Mazda Speed. You have to be a member (racer) to order through them. NASA Time Trial qualifies, so I was able to order a set yesterday for delivery tomorrow. I will than go to Pettit for install with a funnel type inlet to the inside of the oil coolers. I have the Mazda Speed nose, so all should work well. Only worry about hose between intake and backing plate on a street car. Should be interesting how this works out. I will advise and hopefully take pictures during install.

Jay

 

great info Jay, lets see some pics!