Project little red, part deux

[Clark Griswald]

I previously did an upgrade that included air ducting for my brakes, front and rear. All the parts where hand fabricated.

Here is the post on that saga.
http://www.pelicanparts.com/ultimate/Forum3/HTML/012020.html

The rear cooling turned out great. But I was not happy with the fronts. Ground clearance was not adequate. Last trip to the track proved this to be true on the first off-track excursion. Plus I learned a lot while doing the work, and saw so many opportunities for improvement.

I even considered purchasing the available CoolBrakes kit. But being stubborn I never say die. Plus I was convinced I could do better than coolbrakes.

So, I had another go at it.


I see several design flaws with coolbrakes. The goal of the kit is to drive as much fresh air into the eye of the rotor as possible. The more air flow, the more cooling. Yet the kit falls on several points.

Here is the coolbrakes kit:



The biggest problem is in the scoop. First notice how small the cross section of the scoop becomes where it joins the round tube. It looks very restrictive.

Second the scoop forces an abrupt 90 degree change of direction where the scoop joins the hose. This pretty much kills any ram-air effect.

Thirdly the junction between hose and shroud is much smaller than the size of the hose. Again restrictive.

Lastly, the scoop mounts fully underneath the control arm. Because of this height of the scoop opening is limited to provide ground clearance. Limiting the overall opening size and effectiveness.

With all those design flaws, how could I not do this one better? So tin snips and torch in hand, I did just that.

Step one was to build a better scoop. I decided that mounting the scoop in front of the control arm would allow me to solve the coolbrakes limitations.

Mounting in front lets the scoop sit a little higher, enabling a larger front opening. It also allows a smoother transition from scoop to hose, without 90 degree bends.

Here it is:



The scoop clamps to the angled stay that triangulates the control arm. The size of the opening is a good bit larger than coolbrakes.



I rounded off the connection to the hose. Turns out wire wound hoses don't like to clamp to rectangular pipes.

Next up, the shroud.



Looks a lot like coolbrakes, but I angled the pipe into the round plate. The angle enables a larger air passage.

The problem is that the strut is right in the way. By coming in at an angle, I was able to sneak behind the strut and make a much larger air passage.

Here is the shroud installed:



You can see the air passage is very large. As a reference point, you can see it is at least 50% larger than the hole for the spindle. Refer back to the picture of coolbrakes and you can see they are about the same size as the spindle hole.

Here is the backside of the shroud:



You can see it fits into the back of the rotor very tightly. The air is delivered to the hub very well.

Hear is a shot of the full deal, installed:



You can see how the scoop clamps to the control arm. The angle of the scoop creates a larger opening cross section. Nothing but smooth transitions all the way back to the shroud at the rotor eye.

Here is the view from the front underside:



The scoop provides plenty of ground clearance. It is not the lowest point on the suspension. Yet it still hangs down in the air stream under the car.

The problem with coolbrakes is that it mounts under and behind the control arm. That really limit the size of the scoop opening while still maintaining decent ground clearance. You can see that my scoop mounts about 3/4 inch higher, allowing that much larger of an opening.

This time I am pleased with the results. I think I bested the coolbrakes design. Now I have a really solid brake cooling solution front and rear.

I am heading off to Willow Springs tomorrow for three days of brake abuse. This will be good test.

[emcon5]

Looks great Chuck, Have fun at Willow.

Tom

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82 911SC Coupe

[89911]

I believe the only way to get adequate air flow is to have the openings directly in the bumper ala RS bumpers that allow the clean air to be driven into the rotors rather then scooping the turbulent air underneath. I have a cool brake kit on my car but will be installing a direct cooling system on an 87 coupe this winter with RS bumpers with the brake duct openings. It seems the only way your going to get enought air with the scoops underneath is to have them low enough below the front valance. When there that low, we all know what eventually happens to them. Best of luck Clark, your digital photo's and presentation is, as always, top notch.

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8 9 9 1 1, The last of the line.

[Clark Griswald]

My first try grabbed the air under the valence. And those scoops where great, but getting the air back to the brakes is the problem. Noplace to route the hoses and still maintain ground clearance.

I think the only way to do that right is to plumb the hoses through the trunk. That's fine for a full-on race car, but I am not willing to do that kind of surgery for a dual purpose car. Defintely the best race solution is RSR valance with hoses through the trunk.

[old_skul]

Clark...regarding the "abrupt change in direction". That will slow the flow of air somewhat through additional friction, but the bulk of the effect will be air turbulence.

Since your original intakes are trapezoidal, with the wide part at the leading edge, the net effect at the rear is positive pressure. Since there's incoming air at the front, the positive pressure moves air through the hose and to you brakes.

The openings, be they smaller or larger, probably didn't change things much either. Positive pressure overcomes all that.

The big improvement you made is the new, improved, "big honkin'" scoops in the airstream. The larger the cross section of the intake, the larger the volume of air you'll move through the system.

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9 RIP
The Porsche Owners Gallery

[Jack Olsen]

That looks great, Clark. Are you going to be at Willow this weekend? Big Track and the Alfa event, or small track POC?

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Jack Olsen
My Rennlist page • My Pelican Gallery page • My Porsche Owners Gallery page

[Clark Griswald]

I'll be on the short track with POC on sat/sun. And with a different club on Friday.

[Jack Olsen]

If you get a chance, come over and say hi at the big track. There are going to be five or six (mostly early) 911s giving the Alfas a run for their money.

And when is your brake cooling kit going into production? You've got me thinking about something similar for my transaxle cooler.

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Jack Olsen
My Rennlist page • My Pelican Gallery page • My Porsche Owners Gallery page

[orbmedia]

Alfas? Jack c'mon you shouldn't have any problems with them. Unless of course you can't see on account of the smokescreen they eminate.


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[rob911]

Great article, has this made it into the new "101 projects for your 911" yet?

I have been day dreaming about a similar project myself.
I did wonder about picking up stones and gravel and firing them into my brakes. Does this ever happen? I thought about a mesh in the hose to catch them with a hole in the bottom of the hose (upstream side!) to allow them to escape.

How did the brakes fare on the track?