12v high cfa fans/brake ducting

[93RTTurbo]

I've searched, and although I have found information on fabricating brake ducting for cooling the front brakes, I have not seen anyone address the idea of supplementing the ducting with high cfm 12v fans directed at the calipers/pads to improve cooling in hard braking applications.

These are thumbnails, with large pictures not suitable for 56k, of the left and right sides. The SMIC has been removed and replaced with an FMIC, and the fog lights have been removed.

Leaving a nice space for cooling ducts towards the front brakes. Which has been done before, however, my question is, would the additional of a pair of high cfm 12v fans in the ducting produce enough additional airflow to justify the (minimal) additional weight of the fans/relay/ducts and so on?

When the car is being driven hard, there's naturally a certain amount of turbulent air forced up under the wheelwell, which cools the brakes. Although I can't picture a fan of that size (5 inch diameter, estimated) being able to flow enough air to overcome the air currents tumbling around under the wheel well, enough to provide any significant additional cooling, when the car stops, the fan would hypothetically provide additional airflow to cool the hot brakes down significantly faster.

Although it wouldn't have that much effect while actually driving hard, the benefit would come from the shorter period of brake cooldown after the car is stopped, allowing overheated brakes to return to an optimal temperature range more quickly. So on that next run, the brakes are starting out cooler, although of course not completely cold, which is a good thing.

I don't see a lot of benefit for daily driving, but for autocross or other short duration applications where a shortened brake cooldown period would desirable, I'm thinking brake cooling ducts fitted with lightweight high flow 12v fans would be a worthwhile modification. Of course the front dust shield would need to be cut through for a vent, directed at the brakes themselves.

You can see in these photos that my dust shields are pretty ratty anyway, and need replacing. Is it worthwhile to add electric fans in that space, mounted as far rearward, as close to the brakes as possible? I could easily tie them into the existing set of toggle switches on the center console, but a more complete solution would be to use a temperature activated switch to control the fans, as needed.

[Highboosted]

Yep, brake cooling blowers been around for ages, most use boat bilge blowers. Used most often in short tracks where you're hard on brakes and low on speed for brake cooling. Wouldn't provide much brake cooling without actual ducts, though.

Here's a pic of phil's blowers, sort of:

[mehlosTT]

Fans? Can some one post some pics of anyone's bake duct cooling set ups? Surprised that there are no ready made systems out there between all the 3S vendors we have.

[93RTTurbo]

I've seen a few pictures of them on Supras and so on, homemade setups of course. There was a Viper at ECG '05 or '06 with one, no fan though. Never saw anything done with these cars though.

I got the idea when mine was up on the lift a couple weeks ago, installing new crossdrilled/slotted rotors and Stillen brake pads all the way around. When it was lowered to eye level, I realized that I could see all the way through to the dust shield...and amazingly, there was a solid chunk of empty real estate in there, once the SMIC is out and the foglight is removed. Just straight on back, a direct shot to the brakes, as you can see.

So I will look for a shrouded inlet to fit to a piece of ductwork, and see about making one. Without a fan installed, I don't think there will be a significant difference at low speeds since there won't be that much more airflow coming through the relative restriction of the duct, although it would of course be a more directed flow of air. My theory is there will be some benefit gained by funneling air through a duct simply because of the smoother surface it is flowing over, and thereby subject to less turbulence to waste the cooling air out the bottom, the sides, and so on, resulting in a greater volume of cooler air released into the immediate vicinity of the brakes. But is it a measureable benefit? That's what I am interested in. If it isn't measurable, it isn't worth the effort, in my opionion.

I could certainly rig up something to give a relative approximation of comparative airflow to the wheelwell area. But unless it results in not just measurable, but functionally significant changes in brake cooling, it's not something I'd put in there just to say I did it.

At higher speeds, I'd hypothesize that a well designed brake cooling duct could slow the rate of overheating, but that a fan would actually be useless or even counterproductive in such an application, since the volume of air flow in the wheelwell with or without ducting, at high speeds would be far in excess of the fan's flow rate.

My questions are...

Larger duct vs. smaller? Intuitively I would think "more airflow is better" but of course that isn't always so. The important aspect is the velocity of the air as it exits the vent onto the brakes. If it can't obtain enough velocity to overcome the natural air channeling through the area, it can't reach the brakes to carry away the excess heat.

So, what about a fairly large duct, that funnels into a relatively small vent aperture? As the car moves, the air is channeled into the duct, subject to a slight compression with increasing speed, forcing it out at a higher velocity (although of course same mass) at the other end? This would be more than likely a "passive" duct without a fan, as the aperture vent would be too small for a fan.

Another question...is it crucial this duct be as straight as possible, or is the airflow more compromised by lack of smoothness on the inside of the duct? I ask this, because I am deciding whether this can be made efficiently with a piece of flexible duct (much easier to fit yet likely has turbulence causing ridges inside). My goal is maximum air velocity at the aperture vent towards the brakes, for a "passive" system.

A fan based system would rely less on duct integrity, as it would be fitted very close to the wheelwell aperture vent. So I would surmise.

[Highboosted]

The main problem is fitting the duct as so the tire will not rub it at full lock. In our application this is difficult, but not impossible. Quite simply speaking, larger = more airflow. We are not talking about intake ports and filling a chamber, velocity will not reach above forward speed, and there is no "pressure" that the air has to overcome, as there is very little air movement in that preticular region. It goes in the center of the hat, out the rim. this of course shows a huge problem with our stock style rotors which have the "inlet" of the rotor facing the wheel hub, which is completely backwards.

No, don't even bother trying to get a straight duct, thats simply impossible, and the airflow gain is negligable in this type of application. Stick with fire-resistant high temp flexible tubing made specifically for this application.

Even at relatively low speed (50mph), a non-blown duct system will significantly impact rotor temps, so much so as you are required to cover the duct inlets with tape for rotor and pad bedding because the pads will not get hot enough to properly bed in. Even a poorly designed system will all but eliminate brake overheating with proper rotors and pads, unless you're being a complete idiot with your center pedal.

Another ducting option as shown on GrandAm Cobalts, the "smooth duct" option you wanted, but they wern't designed for the smooth duct, just that there was no clearance for normal ducts with the FWD layout (same problems we have):





I think that should cover all your questions. If I didn't cover something, let me know.

[edit]: Just to make sure I was clear, any ducts on our cars will be less effective than normal because of our rotor design. StopTech's 2-piece rotors neatly fix that issue, available through Supercar Engineering, www.supercarengineering.com. Fans are NEVER placed close to the brake, as the plastic would simply melt under the heat. Look at the above pic I posted, that white object is the brake cooling blower.

[mehlosTT]

The CF brake ducts as shown above in the pics is what our cars should have had fab'd a long time a go; inlets at below bumper with a splitter combined, at least for the side mount IC group.

I hope someone realizes the potential sales they could have if they'd make these for our platform. ( Hey SCE or DeftRacing , hint

[93RTTurbo]

Originally Posted by Highboosted

Even at relatively low speed (50mph), a non-blown duct system will significantly impact rotor temps, so much so as you are required to cover the duct inlets with tape for rotor and pad bedding because the pads will not get hot enough to properly bed in. Even a poorly designed system will all but eliminate brake overheating with proper rotors and pads, unless you're being a complete idiot with your center pedal.

If I am understanding correctly, a duct system would be more beneficial to those of us without the "big brake kit" setups, because the StopTech for example, is better designed to disperse the heat effectively. I do have crossdrilled/slotted rotors, although they have just been installed, so I have no firsthand experience with them as far as racing or hard driving conditions. Yet.

The smooth ducting system is sweet! Great pictures. But, with the ground clearance many of us have...that's probably not going to be too practical, unless we want to include "possum bits removal from brake ducts" as part of our maintenance routine.

I'm glad you pointed out the possibility of melting the fans, that close to the rotors. I hadn't considered this.

Next time I put it up on the lift, I really need to take some measurements, as far as wheel lock to wheel lock, and see if there is room to put a vent towards the inner side of the "dust guard"...there's no point blowing any more air at the tire itself. To be effective, the air needs to be directed at the rotors/pads, not just in the direction of the tire or wheel itself.

Now I'm thinking...although I could be completely off track, since I have never unbolted a front fender to see what is under there, and how much room there is, and so on...vented front fenders, with the vent facing forward (as opposed to the ones designed to channel heat away, or at least look like they do) as a cowl design of sorts...to scoop in cooler air, into a duct that vents directly at the caliper area? Is this too far fetched?

[Highboosted]

Originally Posted by 93RTTurbo

If I am understanding correctly, a duct system would be more beneficial to those of us without the "big brake kit" setups, because the StopTech for example, is better designed to disperse the heat effectively. I do have crossdrilled/slotted rotors, although they have just been installed, so I have no firsthand experience with them as far as racing or hard driving conditions. Yet.

The smooth ducting system is sweet! Great pictures. But, with the ground clearance many of us have...that's probably not going to be too practical, unless we want to include "possum bits removal from brake ducts" as part of our maintenance routine.

I'm glad you pointed out the possibility of melting the fans, that close to the rotors. I hadn't considered this.

Next time I put it up on the lift, I really need to take some measurements, as far as wheel lock to wheel lock, and see if there is room to put a vent towards the inner side of the "dust guard"...there's no point blowing any more air at the tire itself. To be effective, the air needs to be directed at the rotors/pads, not just in the direction of the tire or wheel itself.

Now I'm thinking...although I could be completely off track, since I have never unbolted a front fender to see what is under there, and how much room there is, and so on...vented front fenders, with the vent facing forward (as opposed to the ones designed to channel heat away, or at least look like they do) as a cowl design of sorts...to scoop in cooler air, into a duct that vents directly at the caliper area? Is this too far fetched?

Been out of town working, so couldn't keep up with this. Anyways, as far as the vented fender idea, I don't see that as being possible, and very well impractical with our limited space in both areas for and aft of the wheel at full lock. There's also a wire harness that runs behind the fender. Yes, a duct system would be benificial, but as I said earlier, the stock rotors would make the duct system less effective at rotor cooling. Therefore the ducts will have a greater impact on aftermarket designs such as SCE's WIDE rotors and big brake kits. Generally speaking, though, if you are overheating your brakes, the most likely culprit is the driver. Our stock brakes with proper pads and fluid will shame many a faster car's, and with proper brake usage will last a full day or more at the track without problems. No ducting in the world will help a driver who hammers the brakes from 140-50 MPH lap after lap on street pads and DOT 3 fluid that's 3 years old. Big brakes or not. That was the point of that quoted sentance.

Again, in simple form:

1. A duct system will be more efficient on a car equipped with big brakes or aftermarket rotors with the vent inlet facing inwards.

2. A duct system will also greatly help people who suffer from overheating brakes.

3. A duct system will not solve overheating problems cause from improper pad selection or usage.

4. K.I.S.S. You will find this term everywhere, especially in endurance racing. Stands for "keep it simple, stupid". Self-explanitory, in that the simpler system will out-perform and out-last a more complicated one, over time. case in point: I've seen a race team's chances of winning a race ruined because a complicated brake cooling system that used flappers to control brake temp stuck closed, causing the brakes to catch fire and nearly burn the whole car to the ground.

5. You won't find brake blowers on cars that don't need them. Brake cooling in the pits is better achieved with simple fans/blowers not mounted to the car.

6. Big brakes last longer than your stockers. I've gone through 4 sets of front rotors in one season. Phil (SCE) has yet to replace a StopTech rotor, ever. I've gone through even more pads. If I remember right, Phil is still on his first or second set.

7. Buy a spare set of rotors if you go tracking, preferably non-drilled or slotted (unless the slots don't reach the rotor edge). Drilled ones will crack eventually, and if yours are from ebay, irotors, or race concepts, then they will not make it back home from the track. I will go as far to say they will not last one 20 min. session with track pads. Better yet, I will venture as to say they will not last one hot lap with track pads and R comps.

[MichaelMR2]

yeah, I wanted to say what our High boosted said...save your money on something that's not likely to make much difference unless the car is under special conditions, and spend on a decent set of rotors...which are the root of the problem anyway...

most cars these days(Performence category) that are anything near the weight of ours come standard with ATLEAST 354mm rotors (4+pot) assuming your in america you'd be silly not to atleast go to one of the cheaper 354mm kits as it's so DAMN CHEAP over there!!!