THE Ducting / Heat Transfer Thread
07-13-2007 | 05:52 PM
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From: Houston
THE Ducting / Heat Transfer Thread
Hello 8'ers:
I've spent a lot of time recently thinking about how to better track-prepare my car for DE and to a lesser extent autocross. I've tried to compile all of the useful information on ductwork in one place, so that someone searching for information pertaining to this topic can get all of the destratified information in one place without having to scour the eleventy-billion threads that are tangential or integral to this topic, just for one useful picture. Many of the phrases will seem exactly the same as you've seen elsewhere on the site...because they are!
When I say ducting, I mean specifically [for now], ducting to the front brakes and oil coolers.
Here's some background, for those of you who haven't had a chance to dig through all of the threads:
Mesh: The general consensus is that although screens such as those made by RB will protect your Oil Coolers, Radiator, AC Condenser, etc, and are also aesthetically pleasing to some, they slow down velocity of air passing over your heat transfer components to a sluggish pace, lowering their efficiency. I would love to see data on this, but was unable to find anything. [i.e. 75mph air drops to 4mph after a screen before hitting face of radiator, etc]
Aerodynamic Drag: There's no way for me to measure it. As a rule of thumb, more airflow is good, but there's a point that you've got diminishing returns. For example, many race teams believe that you only need 1/4 the surface area of the heat transfer surface in an opening in order to effectively cool it. Thus, one could argue that body kits make no difference other than adding weight and causing more drag. I've seen some wind tunnel data on the subject but am unfortunately unable to share it. On an RX-8, I'd shy towards more airflow because at the level of competition I'm at the aerodynamic drag is negligible, whereas the heat of the rotary is not. Bigger is better?
I'm going to quote a local race-prepper that got involved in a "Body Kits: Function or Fashion" thread on a forum I frequent, because he's seen a lot more of the data I referred to.
Oil Coolers: [dubbed down for the even-more-ignorant than me, square one]
The right opening (above plate) is an oil cooler. Pictured is a mesh screen I installed because both sides (oil coolers and ac condenser) were getting beaten to **** by rocks and bugs, and I don't own a fin comb.
Then I read some data about change in air velocity [that I can't find now] when it's forced through a seemingly negligible latticework of grille, and immediately ripped them out, as I'm extremely harsh on the car in various track events and need that airflow.
Next picture:
For examples sake, this is the front fascia. I used to have my license plate and bracket as pictured [bugs bunny position, if you will]. As mentioned by someone else on this forum, "In the enduro race on Best Motoring International...there was a rather LARGE difference in water temps on the rx8 when they added the front license plate to the car. Of all the car's (with front plates added), the Evo had the least change in temps, due to the side mount (didn't block anything).
They had two sessions, one without plates, and one with plates. For those interested, check torrentspy and search for best motoring, and download the enduro race."
With this in mind, I've got to add that only the bottom 1/2 of that black matte bumper insert is open to airflow. Thus, if 5" ^2 of license plate is covering open inlets, it goes to show that minute changes to the front fascia of your car can have dynamic results.
The point I'm trying to make is, if you've got too little, bigger is better, at least to a point - and I wanted to reinforce that even the smallest of changes can have drastic effects. I'm sure that the airflow versus heat exchange levels off sharply at a point (all the way to bumperless) but I can think of several examples where car designers/engineers have dropped the ball. I don't pretend to be as audacious to say I'm smarter than someone who does it for a living, please don't quote me as saying that.
The 1/4 surface thing I mentioned above intrigues me. Reference the size of these coolers to the size of the inlet in the first post:
No bumper: [jacked from "Surgery has begun" thread]
Remember, the vast majority of us don't have the Mazdaspeed bumper, so Mazda deemed that seemingly small opening as enough for these coolers.
The only reason I'm dwelling on aerodynamics/airflow is it's the only resource I can tap for free (you can get as much air as you want), and because when it's hot outside and I track my car, my dash lights up like a Christmas tree. Heat is the only thing that can screw pretty much everything in your car up at once. (oil, water, brakes, tires, IAT, hell even melting parts of your car - ask me how I know)
I'm not even to the point after years of tracking my car that I can utilize it to its full potential, so making huge changes will hurt rather than help, because i'll have to adapt to them. I've just got to make sure my car lasts that long, which is where cooling comes in.
Enter, what I deem is a logical modification. A lot of threads deal with adding a 3rd oil cooler in series, but without quantitative data on that, or an experienced failure in my car's coolant system, it's VERY hard to justify, even as a prophylactic measure. Thus, I propose better ducting.
Background on oil coolers/fender gills/fender lining/brake ducting:
Example: The RX-8 comes with "fender gills" from the factory. They even make replacement fender ducts, as pictured:
[pick jacked from other thread]
It would follow that they would vent heat from the engine or brakes, anything. Wrong.
Here are, in my mind, some of the most genuinely important pictures that you can take of your car: *Note that these temperatures are relative*
Engine pics with cover on
Engine pics without cover
The money shot
It can be clearly seen that the fender vents are NOT functional. One might want to find a way to duct hot air into the empty fender to allow for lower underhood temperatures. Unfortunately, upon further investigation:
The bridge from the engine to the fender is smaller than a Reese's cup. I assume no one is willing to mess with the structural rigidity of the car, or void their warranty. I see 2 options, the ghetto, and the elegant.
The ghetto approach deals with brake cooling. With black matte plastic in the wheelwells, a lot of the heat from the rotors and calipers is trapped. There are actually vents from the engine/oil coolers INTO the wheel well:
The obvious solution is to cut holes behind the wheel, fab up some ducts to the gill. It would work trusting that you're traveling in a forward direction. I would really love to mock up a proof of concept caveman airflow test to make sure that hot air from the brakes would be forced through the ducts and not forced down, before I cut up my car. The drawback is that there's a floor to these vents, so dirt, mud, and small furry animals would take up residence there. Here is a DIY for this method, and I think that it was executed nicely.
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-brake-cooling-ducts-track-use-83801/
another method
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-brake-cooling-ducts-96296/
And again, once it's done, everyone else is happy. No one took data! When I can think of a scientific way that would allow me to heat the brakes to a comparable temp, then measure temps, I'll do this mod.
The latter method involves custom fiberglassing/tubing/pvc/dryer hose/Mil Spec flex tubing, that would create a duct from behind the oil cooler (anterior of the fender, and pictured above).
I think fans pulling air through would add to this proposed system.
The beauty is...both methods could be done. Unfortunately, I'm not sure how much heat the poor fender could take (depending on efficiency of the gill, of course) so we shall see. I do NOT think that simply putting some Mil Spec Flex tubing behind the oil coolers (with 7" fans or something to suck air in) and just "dumping" the hot air into the fenders is the best plan, you're just adding warm air to the system. A turndown might work, depending on the strength of the fan (seems like air would be forced in the wrong way).
I've spent a lot of time recently thinking about how to better track-prepare my car for DE and to a lesser extent autocross. I've tried to compile all of the useful information on ductwork in one place, so that someone searching for information pertaining to this topic can get all of the destratified information in one place without having to scour the eleventy-billion threads that are tangential or integral to this topic, just for one useful picture. Many of the phrases will seem exactly the same as you've seen elsewhere on the site...because they are!
When I say ducting, I mean specifically [for now], ducting to the front brakes and oil coolers.
Here's some background, for those of you who haven't had a chance to dig through all of the threads:
Mesh: The general consensus is that although screens such as those made by RB will protect your Oil Coolers, Radiator, AC Condenser, etc, and are also aesthetically pleasing to some, they slow down velocity of air passing over your heat transfer components to a sluggish pace, lowering their efficiency. I would love to see data on this, but was unable to find anything. [i.e. 75mph air drops to 4mph after a screen before hitting face of radiator, etc]
Aerodynamic Drag: There's no way for me to measure it. As a rule of thumb, more airflow is good, but there's a point that you've got diminishing returns. For example, many race teams believe that you only need 1/4 the surface area of the heat transfer surface in an opening in order to effectively cool it. Thus, one could argue that body kits make no difference other than adding weight and causing more drag. I've seen some wind tunnel data on the subject but am unfortunately unable to share it. On an RX-8, I'd shy towards more airflow because at the level of competition I'm at the aerodynamic drag is negligible, whereas the heat of the rotary is not. Bigger is better?
I'm going to quote a local race-prepper that got involved in a "Body Kits: Function or Fashion" thread on a forum I frequent, because he's seen a lot more of the data I referred to.
Originally Posted by CC
in certain applications, that big park bench wing actually reduces rear c/d values on the car and when trimmed right can have virtually zero input on downforce or add hundreds of pounds of load to the rear geometry.
VG's on the rear roof line in a specific angle pattern were wind tunnel proven to shift the drag stall point out and away from the rear of the car, which was formerly a lift generating zone, so the car tracked safer and straighter at speed.
front air dams provided exceptional improvement on front end lift, but were only as good as the ducting which tied them to the vehicles core supports, as running w/ out that ducting induced stall zones in front of the radiator that would likely lead to a car having overheating issues.
hell even simple air trip strips along the front windshield have shown excellent gains in smoothing air flow over the initial transition from a high pressure windshield area to the relative low pressure are of the top of a roof.
i'd agree that 80% of the bodykits out there are just guys w/ fiberglass and carving foam making somthing that is asthetically pleasing, but then again i always thought park bench wings were a retarded thing too, so who knows what can be achieved with a little R&D and part massaging.
VG's on the rear roof line in a specific angle pattern were wind tunnel proven to shift the drag stall point out and away from the rear of the car, which was formerly a lift generating zone, so the car tracked safer and straighter at speed.
front air dams provided exceptional improvement on front end lift, but were only as good as the ducting which tied them to the vehicles core supports, as running w/ out that ducting induced stall zones in front of the radiator that would likely lead to a car having overheating issues.
hell even simple air trip strips along the front windshield have shown excellent gains in smoothing air flow over the initial transition from a high pressure windshield area to the relative low pressure are of the top of a roof.
i'd agree that 80% of the bodykits out there are just guys w/ fiberglass and carving foam making somthing that is asthetically pleasing, but then again i always thought park bench wings were a retarded thing too, so who knows what can be achieved with a little R&D and part massaging.
The right opening (above plate) is an oil cooler. Pictured is a mesh screen I installed because both sides (oil coolers and ac condenser) were getting beaten to **** by rocks and bugs, and I don't own a fin comb.
Then I read some data about change in air velocity [that I can't find now] when it's forced through a seemingly negligible latticework of grille, and immediately ripped them out, as I'm extremely harsh on the car in various track events and need that airflow.
Next picture:
For examples sake, this is the front fascia. I used to have my license plate and bracket as pictured [bugs bunny position, if you will]. As mentioned by someone else on this forum, "In the enduro race on Best Motoring International...there was a rather LARGE difference in water temps on the rx8 when they added the front license plate to the car. Of all the car's (with front plates added), the Evo had the least change in temps, due to the side mount (didn't block anything).
They had two sessions, one without plates, and one with plates. For those interested, check torrentspy and search for best motoring, and download the enduro race."
With this in mind, I've got to add that only the bottom 1/2 of that black matte bumper insert is open to airflow. Thus, if 5" ^2 of license plate is covering open inlets, it goes to show that minute changes to the front fascia of your car can have dynamic results.
The point I'm trying to make is, if you've got too little, bigger is better, at least to a point - and I wanted to reinforce that even the smallest of changes can have drastic effects. I'm sure that the airflow versus heat exchange levels off sharply at a point (all the way to bumperless) but I can think of several examples where car designers/engineers have dropped the ball. I don't pretend to be as audacious to say I'm smarter than someone who does it for a living, please don't quote me as saying that.
The 1/4 surface thing I mentioned above intrigues me. Reference the size of these coolers to the size of the inlet in the first post:
No bumper: [jacked from "Surgery has begun" thread]
Remember, the vast majority of us don't have the Mazdaspeed bumper, so Mazda deemed that seemingly small opening as enough for these coolers.
The only reason I'm dwelling on aerodynamics/airflow is it's the only resource I can tap for free (you can get as much air as you want), and because when it's hot outside and I track my car, my dash lights up like a Christmas tree. Heat is the only thing that can screw pretty much everything in your car up at once. (oil, water, brakes, tires, IAT, hell even melting parts of your car - ask me how I know)
I'm not even to the point after years of tracking my car that I can utilize it to its full potential, so making huge changes will hurt rather than help, because i'll have to adapt to them. I've just got to make sure my car lasts that long, which is where cooling comes in.
Enter, what I deem is a logical modification. A lot of threads deal with adding a 3rd oil cooler in series, but without quantitative data on that, or an experienced failure in my car's coolant system, it's VERY hard to justify, even as a prophylactic measure. Thus, I propose better ducting.
Background on oil coolers/fender gills/fender lining/brake ducting:
Example: The RX-8 comes with "fender gills" from the factory. They even make replacement fender ducts, as pictured:
[pick jacked from other thread]It would follow that they would vent heat from the engine or brakes, anything. Wrong.
Here are, in my mind, some of the most genuinely important pictures that you can take of your car: *Note that these temperatures are relative*
No heat from the A/C line, that's BS. No heat from the throttle body that's BS. Go drive for 20 minutes and then open the hood and touch them and I'd have 3rd degree burns.
Engine pics with cover on
Engine pics without cover
The money shot
It can be clearly seen that the fender vents are NOT functional. One might want to find a way to duct hot air into the empty fender to allow for lower underhood temperatures. Unfortunately, upon further investigation:
The bridge from the engine to the fender is smaller than a Reese's cup. I assume no one is willing to mess with the structural rigidity of the car, or void their warranty. I see 2 options, the ghetto, and the elegant.
The ghetto approach deals with brake cooling. With black matte plastic in the wheelwells, a lot of the heat from the rotors and calipers is trapped. There are actually vents from the engine/oil coolers INTO the wheel well:
The obvious solution is to cut holes behind the wheel, fab up some ducts to the gill. It would work trusting that you're traveling in a forward direction. I would really love to mock up a proof of concept caveman airflow test to make sure that hot air from the brakes would be forced through the ducts and not forced down, before I cut up my car. The drawback is that there's a floor to these vents, so dirt, mud, and small furry animals would take up residence there. Here is a DIY for this method, and I think that it was executed nicely.
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-brake-cooling-ducts-track-use-83801/
another method
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-brake-cooling-ducts-96296/
And again, once it's done, everyone else is happy. No one took data! When I can think of a scientific way that would allow me to heat the brakes to a comparable temp, then measure temps, I'll do this mod.
The latter method involves custom fiberglassing/tubing/pvc/dryer hose/Mil Spec flex tubing, that would create a duct from behind the oil cooler (anterior of the fender, and pictured above).
Originally Posted by RG
Relocate the rear bracket that holds on the oil coolers. Make a fiberglass duct that goes from the back of the coolers, over the wheels, and out of the vents. Oil cooling would benefit from it. IF you can cool the oil better, you are cooling the engine.
The beauty is...both methods could be done. Unfortunately, I'm not sure how much heat the poor fender could take (depending on efficiency of the gill, of course) so we shall see. I do NOT think that simply putting some Mil Spec Flex tubing behind the oil coolers (with 7" fans or something to suck air in) and just "dumping" the hot air into the fenders is the best plan, you're just adding warm air to the system. A turndown might work, depending on the strength of the fan (seems like air would be forced in the wrong way).
07-13-2007 | 05:52 PM
#2
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From: Houston
Finally, something I'm throwing in at the last second, brake ducting the non-ghetto way. I've never seen a comparable product for the 8, but here are some Forge brake cooling for Evo (without brake ducts).
This kind of negates the dryer hose method, although someone here at the rx8club cited 150* drops (using a pyrometer, perhaps Polak) using the ghetto cut fender/add gutter method.
Thus, backing plates (dust shields) are a good option. Speedsource will sell them to you.
They're pricey.
Someone mentioned the quality of the Speedsource/Mazdaspeed plates on the other forum, when I posted them up for consideration:
I'm not sure if this is valid or not.
We pay what, $300 for plates? My only argument is that they seem to work pretty damn well for Speedsource.
With this said, please add what you can, to this Noob's guide for cooling, I suppose. I'm sure I missed about 40 relevant topics, like radiators, and I would be delighted if ya'll let me know. My only request is that we keep hearsay and OT chatter to a minimum and provide DATA when you can.
Originally Posted by ? Jay Goldfarb perhaps?
The fact is, unless you are ducting air directly to the center of the rotor, allowing it to flow out through the vanes, your cooling effect and performance enhancement is somewhere between diddly and squat.
Thus, backing plates (dust shields) are a good option. Speedsource will sell them to you.
They're pricey.
Someone mentioned the quality of the Speedsource/Mazdaspeed plates on the other forum, when I posted them up for consideration:
Originally Posted by CC
so why is whoever makes those backing plates with dutcing too lazy to unbolt them the proper way rather than cut it. Upon re-welding unless he's following very specific welding techniques that whole back plate can heat deform.
Originally Posted by CC
I think we may be looking at different areas. In the photo below is that same part, the red box indicates a cut and re-welded area, which has no matching cut and re-weld area above it that i can see. In addition to the fact that i'm sure whoever produces these parts doesn't make enough to afford a 100k+ dollar press to stamp out these things new, so they look like they have been unbolted and cut, as indicated by the red box, then the green box appears to be the deformation of the metal (though flattened back out as best as the builder could manage) from having cut and pried the plate off, and then the purple circles look to be spot welds for that tubing which looks to essentially be rolled over sheet steel.
That part will work for its intended purpose, just not optimally, i'm guessing whoever makes them has a hard time getting to a bolt or nut on the hub that plate is affixed too, which makes removing the hub for a proper backing plate uninstallation difficult. Thus they cut it for removal, and now having full access to whatever the source of problem was, can re-assemble in the proper order after welding the plate back up.
Honestly though, if built on a case by case basis, a part like that could be fairly easy to fabricated on a car, or just don't be lazy and remove the plate the right way. Either way, simple enough to build, just need the car on a lift and go.
That part will work for its intended purpose, just not optimally, i'm guessing whoever makes them has a hard time getting to a bolt or nut on the hub that plate is affixed too, which makes removing the hub for a proper backing plate uninstallation difficult. Thus they cut it for removal, and now having full access to whatever the source of problem was, can re-assemble in the proper order after welding the plate back up.
Honestly though, if built on a case by case basis, a part like that could be fairly easy to fabricated on a car, or just don't be lazy and remove the plate the right way. Either way, simple enough to build, just need the car on a lift and go.
With this said, please add what you can, to this Noob's guide for cooling, I suppose. I'm sure I missed about 40 relevant topics, like radiators, and I would be delighted if ya'll let me know. My only request is that we keep hearsay and OT chatter to a minimum and provide DATA when you can.
07-13-2007 | 06:51 PM
#3
An RX ate my baby
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From: A swirling eddy of electronic mayhem
Nice thermal pictures.
What I have to add here is just engineering pragmatism. I'm an electronics engineer by trade and I care about temperature and heatflow in the products I design.
The advice I have to offer is this:
Consider whether it matters if a location gets hot before you go trying to cool it off. Sometimes in doing this you rob the airflow from another needed area.
It obviously matters on the oil coolers, and on the AC if you are trying to stay cool in a hot climate.
It may not matter on the brakes. The brakes in the RX8 are freaking huge and really good compared to almost any other car. If you are autocrossing your car, you have time in between runs to cool the brakes and the low airspeed of the car doesn't put much air flow against the brake rotors. The extra unsprung weight of ducts will not shave any time off your lap.
However, in road racing it may make some difference if you are seeing brake fade.
The difference in brake pad life between a 50 degree temperature difference is probably pretty small.
I wouldn't needlessly cool things.
Finally, when you see hot spots right next to cool spot in your thermal images, that's not necessarily bad. It probably means that you are getting enough air flow that the heat is getting out of the area. Big blobs are probably bad.
What I have to add here is just engineering pragmatism. I'm an electronics engineer by trade and I care about temperature and heatflow in the products I design.
The advice I have to offer is this:
Consider whether it matters if a location gets hot before you go trying to cool it off. Sometimes in doing this you rob the airflow from another needed area.
It obviously matters on the oil coolers, and on the AC if you are trying to stay cool in a hot climate.
It may not matter on the brakes. The brakes in the RX8 are freaking huge and really good compared to almost any other car. If you are autocrossing your car, you have time in between runs to cool the brakes and the low airspeed of the car doesn't put much air flow against the brake rotors. The extra unsprung weight of ducts will not shave any time off your lap.
However, in road racing it may make some difference if you are seeing brake fade.
The difference in brake pad life between a 50 degree temperature difference is probably pretty small.
I wouldn't needlessly cool things.
Finally, when you see hot spots right next to cool spot in your thermal images, that's not necessarily bad. It probably means that you are getting enough air flow that the heat is getting out of the area. Big blobs are probably bad.
07-13-2007 | 07:41 PM
#4
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From: Houston
IIRC you love ripping off fenders, seats, whatever, in order to placate other posters.
It brought a smile to my face, as you did it in several threads.
"BRB 5 min guyz"
Next post: Picture of torn down seat.
All valid points, if it ain't broke, don't fix it. However, I do get horrendous brake fade at my DE's (4 22 minute sessions a day, 2 days straight, 2 quarts of oil per day, 82 miles for 11.7 gallons of fuel, it's pretty hot, especially in 95* Texas).
I'd also point out again that I tend to believe that if successful race teams like Speedsource see a need, then it's worth investigating.
Granted, I forgot to mention that there's no reason to hack your car apart as I somewhat suggested till you've changed out all your fluids, run water wetter, etc.
Abbid, does this belong here or in Competition/Racing?
It brought a smile to my face, as you did it in several threads.
"BRB 5 min guyz"
Next post: Picture of torn down seat.
Originally Posted by corners
However, in road racing it may make some difference if you are seeing brake fade.
I'd also point out again that I tend to believe that if successful race teams like Speedsource see a need, then it's worth investigating.
Granted, I forgot to mention that there's no reason to hack your car apart as I somewhat suggested till you've changed out all your fluids, run water wetter, etc.
Abbid, does this belong here or in Competition/Racing?
07-13-2007 | 10:02 PM
#6
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From: Houston
Can anyone with experience in fluid dynamics comment on whether or not a duct behind the oil coolers would have any effect? And if so, how might it be most efficiently crafted?
07-13-2007 | 10:17 PM
#7
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From: USA
I wouldn't put much value into the fact that Mazda made the stock bumper with small openings for the oil coolers. Remember they also shipped cars with just one oil cooler for some regions/models. From what I recall, the automatics that only had one oil cooler and had engines replaced were retrofitted with a second cooler. It sounds like they underestimated how much cooling the car might require in some regions.
07-14-2007 | 12:27 PM
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From: CT
Btw if you're curious how much the oil cooler screens restrict airflow, you'll be able to find it in the book, Flow Resistance: A Design Guide for Engineers by I. E. Idelchik. It has loss coefficients for any restriction you can imagine. Unfortunately I don't have a copy, otherwise I'd post the info
07-14-2007 | 12:53 PM
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From: Houston
Btw if you're curious how much the oil cooler screens restrict airflow, you'll be able to find it in the book, Flow Resistance: A Design Guide for Engineers by I. E. Idelchik. It has loss coefficients for any restriction you can imagine. Unfortunately I don't have a copy, otherwise I'd post the info
Stay tuned.
07-14-2007 | 04:54 PM
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ok so now you know HOW the car cooling works, and with some quick searches you can find average temps (oil, water etc)
you need to figure out WHAT temps you want to lower/manage. ie do you wanna lower oil temps? water temps? both?
once you know that, its gonna be really simple to implement it.
seems like, looking at the thermal pics, that theres nowhere for the air to go after its gone thru the radiators
you need to figure out WHAT temps you want to lower/manage. ie do you wanna lower oil temps? water temps? both?
once you know that, its gonna be really simple to implement it.
seems like, looking at the thermal pics, that theres nowhere for the air to go after its gone thru the radiators
07-15-2007 | 05:19 PM
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First, know what the spec temp is. None of the posts I've read have mentioned them. What type of brakes do you have? What is their optimum temperature range? Are they running too hot at a particular track? Too cool? Have you noticed they run at different temperatures at different tracks? If you think cooler is always better, your mistaken. That's why many top-end race cars have variable air vents, especially on the brakes.
Get real data, then deal with the specifics. By taking shots in the dark, the chance you're going to improve your performance is slim.
Get real data, then deal with the specifics. By taking shots in the dark, the chance you're going to improve your performance is slim.
07-15-2007 | 09:17 PM
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First, know what the spec temp is. None of the posts I've read have mentioned them. What type of brakes do you have? What is their optimum temperature range? Are they running too hot at a particular track? Too cool? Have you noticed they run at different temperatures at different tracks? If you think cooler is always better, your mistaken. That's why many top-end race cars have variable air vents, especially on the brakes.
Get real data, then deal with the specifics. By taking shots in the dark, the chance you're going to improve your performance is slim.
Get real data, then deal with the specifics. By taking shots in the dark, the chance you're going to improve your performance is slim.
My brakes (Hawk HP+ on stock rotors) have noticeable fade on the only track that I run DE's on, Texas World Speedway, and that's enough for me to want to START taking baselines and to try and combat that fade in the future. I don't own a pyrometer, so I was hoping someone else could chime in that does own one.
You must understand, this thread was meant to start discussion, and make it easier for people new to this to get information about a stock RX-8. I didn't ever pretend to know anything definitively, and I stated that multiple times.
Last edited by Michael; 07-15-2007 at 09:20 PM.
07-15-2007 | 09:18 PM
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From: Houston
I actually priced out that insert for that exact purpose, until I actually took a closer look.
07-15-2007 | 11:40 PM
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From: Northern Virginia near DC
I'm waiting on my oil pressure, oil temperature, and water temperature gauges at the moment, to get a baseline.
My brakes (Hawk HP+ on stock rotors) have noticeable fade on the only track that I run DE's on, Texas World Speedway, and that's enough for me to want to START taking baselines and to try and combat that fade in the future. I don't own a pyrometer, so I was hoping someone else could chime in that does own one.
You must understand, this thread was meant to start discussion, and make it easier for people new to this to get information about a stock RX-8. I didn't ever pretend to know anything definitively, and I stated that multiple times.
My brakes (Hawk HP+ on stock rotors) have noticeable fade on the only track that I run DE's on, Texas World Speedway, and that's enough for me to want to START taking baselines and to try and combat that fade in the future. I don't own a pyrometer, so I was hoping someone else could chime in that does own one.
You must understand, this thread was meant to start discussion, and make it easier for people new to this to get information about a stock RX-8. I didn't ever pretend to know anything definitively, and I stated that multiple times.
You should be able to get a fair pyrometer for under $100 on eBay. I have a needle-type one that I use for tires -- it helps. I don't need any brake work (yet) but when I jump up to R-compounds then it'll certainly be an issue.The thing with the pyrometer is you need to check temps the second you get off the track (in the pit lane if possible). Of course it's better to have built-in sensors on the brakes themselves, but I think that's a little steep for most of us.
07-17-2007 | 09:28 AM
#16
Momentum Keeps Me Going
Joined: Sep 2002
Posts: 5,036
Likes: 4
From: Colorado
Finally, something I'm throwing in at the last second, brake ducting the non-ghetto way. I've never seen a comparable product for the 8, but here are some Forge brake cooling for Evo (without brake ducts).
Quote:
Originally Posted by ? Jay Goldfarb perhaps?
"The fact is, unless you are ducting air directly to the center of the rotor, allowing it to flow out through the vanes, your cooling effect and performance enhancement is somewhere between diddly and squat."
This kind of negates the dryer hose method, although someone here at the rx8club cited 150* drops (using a pyrometer, perhaps Polak) using the ghetto cut fender/add gutter method.
Quote:
Originally Posted by ? Jay Goldfarb perhaps?
"The fact is, unless you are ducting air directly to the center of the rotor, allowing it to flow out through the vanes, your cooling effect and performance enhancement is somewhere between diddly and squat."
This kind of negates the dryer hose method, although someone here at the rx8club cited 150* drops (using a pyrometer, perhaps Polak) using the ghetto cut fender/add gutter method.
- Why leave out the "ghetto" method as you call it? It is a useful track cooling aid.
- The "ghetto" cut fender/add gutter ducting I use works to the extend it lowers temps, but it's also 100% invisible, so .... so who cares and how is it "ghetto"... because it cost less than $20 complete both sides in just a short me? Ok by me if so.
- I did the original DIY https://www.rx8club.com/showthread.p...ght=brake+duct on the "ghetto" method - I don't remember if i said 150 degrees, but if 150 degrees is between diddly and squat, so be it. I don't have the luxury of a gutted chassis to route hoses that SpeedSource has.
- The EVO you show with the beautiful welded duct work (but no shield) has no other passive air flow cooling - so it looks essential for any cooling at all with that BB setup. Of course the fancy duct brings it directly to the center of the 2 piece rotor, which is nice
On the other hand, our OEM shields have useful built-in air gathering vane, that does a fairly decent job at bringing cool air onto the rotor surface of a solid rotor or to the rotor/center of a 2-piece. The DIY simply increases the flow to that air gathering area somewhat at speed.
Except for this missing info , a nice compilation of thread quotes and pics BTW. Great idea
Last edited by Spin9k; 07-17-2007 at 09:30 AM.
07-17-2007 | 10:25 AM
#17
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From: Houston
- The "ghetto" cut fender/add gutter ducting I use works to the extend it lowers temps, but it's also 100% invisible, so .... so who cares and how is it "ghetto"... because it cost less than $20 complete both sides in just a short me? Ok by me if so.
- I did the original DIY https://www.rx8club.com/showthread.p...ght=brake+duct on the "ghetto" method - I don't remember if i said 150 degrees, but if 150 degrees is between diddly and squat, so be it. I don't have the luxury of a gutted chassis to route hoses that SpeedSource has.[/qujote]
150* is progress in the right direction, but I can't qualify it. I'm sure that someone on this website can, though.
150* is progress in the right direction, but I can't qualify it. I'm sure that someone on this website can, though.
Normally there would be a hose connected to the duct on the brake, but it was removed for pictures
Except for this missing info , a nice compilation of thread quotes and pics BTW. Great idea
07-24-2007 | 01:18 PM
#18
Oil and water temperatures
Michael:
Thanks for the interesting discussion.
I put the RB oil/water temp gauges in my car about 2 months ago, and had a chance to run a track day at Gingerman a few weeks ago with them. From driving the last few months on and off track, the temp on both water and oil stays more or less between 180-210 F once the car has warmed up. In retrospect, this is what you would expect in a normally operating vehicle as the water temp is thermostat regulated, and the purpose of the water is to keep the block (and by conduction the oil) cool. I never saw either temp go above 210 at Gingerman.
Brakes are a different story. After 2 days at Gingerman, I now have a pretty strong vibration in the pedal (yeah, I know not to put on the parking brake, and I didn't use it either day). Pads are still stock (or what is left of them). I experienced some fade the first day (nothing excessive, just enough to know they were fading). I did the "ghetto" cooling mod between the 1st and 2nd days, which seems to have addressed the fading on the 2nd day, though as you mentioned there are so many variables it is hard to know for certain.
BTW, I have a stock body (no Mazdaspeed airdam, etc.), though have RB's REVi with the air scoop.
Thanks for the interesting discussion.
I put the RB oil/water temp gauges in my car about 2 months ago, and had a chance to run a track day at Gingerman a few weeks ago with them. From driving the last few months on and off track, the temp on both water and oil stays more or less between 180-210 F once the car has warmed up. In retrospect, this is what you would expect in a normally operating vehicle as the water temp is thermostat regulated, and the purpose of the water is to keep the block (and by conduction the oil) cool. I never saw either temp go above 210 at Gingerman.
Brakes are a different story. After 2 days at Gingerman, I now have a pretty strong vibration in the pedal (yeah, I know not to put on the parking brake, and I didn't use it either day). Pads are still stock (or what is left of them). I experienced some fade the first day (nothing excessive, just enough to know they were fading). I did the "ghetto" cooling mod between the 1st and 2nd days, which seems to have addressed the fading on the 2nd day, though as you mentioned there are so many variables it is hard to know for certain.
BTW, I have a stock body (no Mazdaspeed airdam, etc.), though have RB's REVi with the air scoop.
Last edited by Joe RX-8; 07-31-2007 at 01:03 PM.
07-24-2007 | 02:28 PM
#19
my friends and I have been tracking rx8's for 2 yrs. some of us run the hawks hp plus. i run carbotech xp8's front and bobcats on the back. none of us have ever experience brake fade that i am aware off. and it does get hot here in Ga. We also run on hard on brakes tracks like road atlanta and cmp. therefore i have dropped the ducting thought. My pads last me approx 8 w/e's and each w/e is about 250miles on the track. I am running on the stock front disc's and i have 46K on the car. they were turned in may this year for the 1st time.
now brake maintenance is very important. I have to clean the disc's throughly after a track w/e and i swap back to the street pads. I also swap out most brake fluid before and event. be sure you have a track fluid in there!
i clean the calipers and lube the slide bolts etc.
All normal track prep and usual keep up. My point is ---no fade for us. Oh yea --we are running hoosiers-- 710's and toyo ra 1's. And we use the good braking to help may our times.
olddragger
now brake maintenance is very important. I have to clean the disc's throughly after a track w/e and i swap back to the street pads. I also swap out most brake fluid before and event. be sure you have a track fluid in there!
i clean the calipers and lube the slide bolts etc.
All normal track prep and usual keep up. My point is ---no fade for us. Oh yea --we are running hoosiers-- 710's and toyo ra 1's. And we use the good braking to help may our times.
olddragger
07-24-2007 | 03:00 PM
#20
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From: Houston
my friends and I have been tracking rx8's for 2 yrs. some of us run the hawks hp plus. i run carbotech xp8's front and bobcats on the back. none of us have ever experience brake fade that i am aware off. and it does get hot here in Ga. We also run on hard on brakes tracks like road atlanta and cmp. therefore i have dropped the ducting thought. My pads last me approx 8 w/e's and each w/e is about 250miles on the track. I am running on the stock front disc's and i have 46K on the car. they were turned in may this year for the 1st time.
now brake maintenance is very important. I have to clean the disc's throughly after a track w/e and i swap back to the street pads. I also swap out most brake fluid before and event. be sure you have a track fluid in there!
i clean the calipers and lube the slide bolts etc.
All normal track prep and usual keep up. My point is ---no fade for us. Oh yea --we are running hoosiers-- 710's and toyo ra 1's. And we use the good braking to help may our times.
olddragger
now brake maintenance is very important. I have to clean the disc's throughly after a track w/e and i swap back to the street pads. I also swap out most brake fluid before and event. be sure you have a track fluid in there!
i clean the calipers and lube the slide bolts etc.
All normal track prep and usual keep up. My point is ---no fade for us. Oh yea --we are running hoosiers-- 710's and toyo ra 1's. And we use the good braking to help may our times.
olddragger
I was experiencing bad fade with the stock pads/rotors w/ stock wheels on Ecsta SPT's.
For the last two driving weekends I've been running Enkei RPF1's (9.5's) w/ 275 KDW2's along with Hawk HP+ pads all the way around, and the brake fade just has a later onset, but it's still pretty drastic. I only put 83-100 miles a day on the car though.
My only explanation as to why I'm getting fade with the HP+'s and your friend is not is because he's probably a better driver, and spends less time on the brakes? I only run at TWS, [www.texasworldspeedway.com], so it might be more brake-intensive?
EDIT: FWIW:
Gingerman: 1.88 miles
TWS: 2.9 miles
Last edited by Michael; 07-24-2007 at 03:03 PM.
07-24-2007 | 04:28 PM
#21
Momentum Keeps Me Going
Joined: Sep 2002
Posts: 5,036
Likes: 4
From: Colorado
There are obviously a host of possible reasons, including to some extent your driving. The only way to tell is do some measurements as close after track as possible. See what your equipment temps are, where they're hot. Then - Issue or no? Fix and continue. Then look at your rotors and pads, brake lines, fluid. It's a system and affected by each component. Your fade is a symptom, the trouble is finding the cause and fixing it.
Another approach is to upgrade and improve the variious brake components to a known design performance level, add as much cooling as you can and measure, measure to make sure your improving. Work at it until you are satisfied with your work.
You can measure with a probe or infrared type pyrometer depending on how much you want to spend and how precise you want to be. I choose a $50 Sears handheld that goes to about 800 deg F. I't done pretty much what I need, although I have thought of getting the $99 1200 deg one.
Another approach is to upgrade and improve the variious brake components to a known design performance level, add as much cooling as you can and measure, measure to make sure your improving. Work at it until you are satisfied with your work.
You can measure with a probe or infrared type pyrometer depending on how much you want to spend and how precise you want to be. I choose a $50 Sears handheld that goes to about 800 deg F. I't done pretty much what I need, although I have thought of getting the $99 1200 deg one.
07-25-2007 | 07:24 PM
#23
my friends and I have been tracking rx8's for 2 yrs. some of us run the hawks hp plus. i run carbotech xp8's front and bobcats on the back. none of us have ever experience brake fade that i am aware off. and it does get hot here in Ga. We also run on hard on brakes tracks like road atlanta and cmp. therefore i have dropped the ducting thought. My pads last me approx 8 w/e's and each w/e is about 250miles on the track. I am running on the stock front disc's and i have 46K on the car. they were turned in may this year for the 1st time.
now brake maintenance is very important. I have to clean the disc's throughly after a track w/e and i swap back to the street pads. I also swap out most brake fluid before and event. be sure you have a track fluid in there!
i clean the calipers and lube the slide bolts etc.
All normal track prep and usual keep up. My point is ---no fade for us. Oh yea --we are running hoosiers-- 710's and toyo ra 1's. And we use the good braking to help may our times.
olddragger
now brake maintenance is very important. I have to clean the disc's throughly after a track w/e and i swap back to the street pads. I also swap out most brake fluid before and event. be sure you have a track fluid in there!
i clean the calipers and lube the slide bolts etc.
All normal track prep and usual keep up. My point is ---no fade for us. Oh yea --we are running hoosiers-- 710's and toyo ra 1's. And we use the good braking to help may our times.
olddragger
FYI I've run Road Atlanta before (though in a Miata, not the 8), and it's a heck of a fun track. How fast do you get going? If I remember in the Miata, we could hit just over 100 on the back in a mostly stock car. At Gingerman I can hit mid-90s in the straight coming into pit row and the straight along pit row, which is 10-15 faster than my wife can get her Miata up to.
07-26-2007 | 12:33 AM
#24
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Joined: Jul 2007
Posts: 37
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From: Sydney, Australia
just a thought, but most wheel well venting n 'real' race cars is to reduce the wheel well pressure so it isn't screwing up the aero. If you got those vents flowing air/relieving pressure you'd be more likely to get increased airflow through your brake ducts since the only thing pumping air with ducts is pressure difference.
I don't know whether serious folks with front splitters would want to tap into the high pressure at the front above the splitter - itd probably rob some front downforce but give a big increase in air to the brakes.
I don't know whether serious folks with front splitters would want to tap into the high pressure at the front above the splitter - itd probably rob some front downforce but give a big increase in air to the brakes.
07-26-2007 | 11:39 AM
#25
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From: Houston
FYI I've run Road Atlanta before (though in a Miata, not the 8), and it's a heck of a fun track. How fast do you get going? If I remember in the Miata, we could hit just over 100 on the back in a mostly stock car. At Gingerman I can hit mid-90s in the straight coming into pit row and the straight along pit row, which is 10-15 faster than my wife can get her Miata up to.