This one is long overdue…. I have been wanting to add functional brake ducts to my 993 for several years, but never really had the time or wherewithal to develop a clean end to end solution….. Well that all changed last year when I wiped the nose off the car in a major “off”. Having the bumpers, fenders and suspension off the car afforded me a great opportunity to see all of the possible pathways (even tried routing through the trunk and frame rails) as well as cycle the suspension through its range of travel. Here is what I came up with and so far have been pretty pleased. It was a simple install and while it does limit turning radius some, it is really not that bad.

All that being said, we did a little experiment and left both control arm scoops in place, blocked off one of the ducts, and ran a couple of hard laps around the track to build as much heat in the brakes as we could. The results were less than stellar, rotors with no duct came in at 825deg, the ducted rotor was 750deg. To improve you would need to jump to a 3in duct, but there just isn’t room for it.

First problem to solve: How to attached and route air to the vanes of the rotor. Having the complete suspension assembled on the workbench was nice. You can clearly see that Porsche left an opening right under the caliper sized just right for a duct. Just need to make some kind of bracket to attach a hose to and direct air through this gap to the rotor vanes. This took a ton of trial and error, but here is what I came up with… Its really a pretty slick little piece.




Second problem: How to route the hose. I’ve seen quite a few folks route the hose along the bottom of the oil cooler, but if you look at the airflow, this is where the cooler is doing most of its works, and I hate to have a duct blocking this part of it. Besides, it makes for some pretty sharp crimps and bends in the hose. But after putting the suspension on and cycling through its range of travel, there is actually more room up a little higher, and there is a nice little crease above the frame rail where you can tuck the major girth of the hose into. And even better , it makes a straight shot to the duct in the bumper. We just need to make a little protection plate to guard the hose from rubbing on the tire at max steering angle. You could crimp the hose a little here and get all of the steering, but that would defeat the purpose.

Step 1: Make the mounting brackets for the rotor. I used 22 gauge aluminum.
Cut out the shape per the template using tin snips
Fold it down the middle at something like a 20deg angle. This will give the right shape to fit behind the caliper.
Then fold the mounting tabs back to straight..
Now the hard part, round out the hose end. I was lucky and had a piece of 2.5in exhaust pipe lying around. I used a body hamper and gently worked the aluminum around the pipe making a perfect tube.
You could probably stop here, but I chose to weld the seam of the “tube” and tack on a couple of “ears” to give a little more strength. (I am a terrible weldor, and 22ga alum was the limit of my ability)




Step 2: Make the protection plate. I attached the drawing for the profile of the protection plate. I cut this out of cardboard and worked the aluminum by hand until if fit the profile template.



Step 3: You will need to remove a couple of inches of the mounting flange for the fender liner (not really a big deal)


Step 4: Rivet the protection plate in place. Use a short piece of hose set into the crease above the frame rail as a guide, and Rivet the plate in place as far forward as possible. Be careful, this really does need to be all the way forward, otherwise the tire sidewall will be rubbing on the sharp edge of the plate rather than the side.

Step 5: Modify the top plate of the oil cooler and ac shrouds to allow the hose through. Sorry no pictures here, I simply bent the back edge up a little bit and slipped the hose through. You could probably do a little better job and notch them for a cleaner fit.

Step6: Mount the rotor mounting plate. The plate mounts between the caliper and upright. Undo the two caliper mounting bolts, slide the plate in place and re-install the bolts. Be sure to torque them back to spec….


Step 6: Attach the hose to your bumper. I found it was much easier to start here, attach the hose to the bumper then feed it back to the caliper rather than the other way around. It may be helpful to remove the splitters so you have better access from underneath.

 

again nice job!, as an alternative the chassis cavity which has an exit to the right and down of your circle can be used instead of the ducts run past the coolers. The small ducts really need big blowers to be effective but any thing does help.

 

Great job. Looks like a very nice instal with very few kinks to obstruct air flow. We took a different route through the unibody (as Bill described). Very similar approach to mounting the ducts to the hub assembly; however, we kept the backing plates to help airflow across the rotor.

 

Beauitful detail

 

Excellent writeup. Did you do a run without the scoops? I wonder if the larger area (without the scoops) could draw more air. The hose diameter looks to be larger than the mouth of the scoops. Should be fairly easy to test.

 

Hey Glen....
I tried this but could not for the life of me figure how to get air into the framerail.... the bumper shocks penetrate pretty far back and I would have had to make some pretty severe turns to get in.... Would love to see how you did that...

Actually the beauty of the mounts is they reach under the caliper, and it you look carefully (I didnt get a good picture) actually reach into the rotor and guide the air right up into the vanes...

 

by scoops you mean the ones in the bumper? They are pretty close to the right size. I havent tried to run with out them.... There is a whole other writeup on what it took to get them to work.

The test we did was just a quick run while we were doing suspension tuning. I had a pro driving the car and he was coming in "hot" so we didnt loose temp in the tires and only had 100feet from the last turn to pit in... I suspect if he ran the whole straight the results at the end would be wider.... But honestly I never really had trouble with overheating, Im just trying to keep them as cool as possible to get the most life out of the rotors.

 

Yes, the ones in the bumper. I thought it might be interesting to take one off, do some lapping and see if there is a difference. Every little bit helps.

This is what I'm talking about:

 

here's a nice way to do it
964/993 brake cooling

 

also blow the rotors out w/ compressed air after each event, be sure to have at least a filtering mask

 

Very.. Very cool...

 

I could actually do that.... The scoops I have dont actually have an attachmnet for the hose, so I built a box that goes behind the scoop and scoop seals to the box, so I can simply remove the scoop.... Ill try it next time im out, probably going to be Nov before I hit the track again.

 

Very cool indeed. I have seen another 993 with a similar set-up with these powered ducts in the front trunk. Very nifty (and costly) set-up. Too bad my 24 qt CoolSuit takes up the entire front trunk (and provides a nice 40+ lbs of ballast)

 

Cool, please keep us posted. Might be interesting to see if it has any impact.