mikegarrison

So what is the consensus on installing a debris screen? I'm planning on putting in a faux duct system this winter. How important (or not) is a debris screen to keep leaves and chunks of tire and whatever out of the ducts?

jvils

Not sure if it's required, but it can't hurt. I've put my arm out a couple times to wave ppl by (yeah, I'm too slow). When someone's in front of me, it feels like my arm is getting sand blasted. Plus the dozens of rubber marks all over the front of the car... there's a lot of rubber flying around.

Anyway, update on my diy setup. The last event I went to I did 5 sessions. One was a 45min session absolutely man-handling the brakes; not a hint of fade, and I was trying to overheat them (short of riding the brakes). It was AWSOME.

cbender

No need for one whatsoever, Mike. I've never gotten anything more than a few small leaves in the ducting -- and they always seem to work themselves out by the end of my next trip if I forget to pull them out. Nothing more substantially -- small gravel, etc. -- have ever gotten into them.

CB

HOTRODS2000

I leave my screens in on the street and take them out for track days. I don't want the screens to reduce any cooling I can get on the track.

depletedUfoot

This is the next mod I want to do to my MY00, so I am very glad I found this thread. There are some great ideas out there.

Couple points. I don't understand how venting the side of the rotor could lead to thermal gradients across the face of the rotor. If your wheels weren't turning, then you could do it, but with wheels spinning, the cooling effect will balance out very evenly.

You will certainly have gradients through the thickness of the rotor (from the inside face to the outside face), and that's probably unavoidable. Then you're relying on the conductivity of the metal to keep moving the heat over to the cool side, where it can be removed. But a standing gradient will set up and stay there until you stop.

This gradient will cause the rotor to warp slightly -- the hotter side will expand more than the cooler, causing the rotor to cup outwards. Somebody mentioned that the outer surface can radiate much more efficiently than the inner, so maybe that helps to minimize this effect.

Second thing, there's a lot of talk about getting the most air through the ducts. A few basics are important to understand. Diameter is definitely important, but so is overall length, bends, smoothness of the inside of the duct, air pressure at the inlet, and not to be forgotten, the size of the openings at each end. If you have a clean 3" path the whole way, but have 2" openings at both ends, you could be wasting that 3" line.

Of course, if you're fighting sharp bends and long runs, then it probably pays to use the larger duct. But the point is to think about all the constrictions. The smallest opening you have dictates the maximum flow.

The best setup I saw in this thread is Jvil's (near bottom of page 4). He ran the 3" ducts from the center, under the car, with almost no bends directly to the dust guards. That's the way to do it if you want a lot of flow. Just have to figure out how to keep from ripping the inlet ducts off.

mikegarrison

Impinging air on the outer surface of the rotor won't work nearly as well as cooling it from the inside. Trust me on this one, or go out and measure it yourself if you want to. There will be radial thermal gradients on the cooled side of the rotor, and there will be gradients across the weakest part of the rotor (the vanes connecting the two sides. It's a much better idea to dump the air at the hub of the rotor.

And yes, there is more to pressure drop than just the size of the duct. But most everything else (bends, constrictions, duct length, etc.) is very sensitive to the air velocity. And bigger tubing means slower velocity (for the same amount of air), and thus (other things being close to equal) less pressure drop. So more flow.

mikegarrison

OK, question #2 regarding screens and the like. Do any of you who don't use screens use your car as a daily driver? Also, does anybody have any problem in rainy conditions? I'm still strongly tempted to use screens and/or blanks that would protect the ducts in daily driving and only open them up for the track. Anybody have a "con" experience that suggests that would not be a good idea? Or is that just overly conservative?

MadDane

I have / use 2" brake ducts and have for close to 2 years.

I have the coastal metals stainless screens and only remove them for track events (approx 8-12) per year.

I have only found leaves in mine, and only because I was lazy and left the screens off for several days after a track event.

For what it's worth.

Claus

jvils

Thx. On the track I had no rubbing/bottoming out at all. Car's at stock ride hide, tho. Sebring is a very bumby track, but I had no clearance issues. On the street it was a different story. I got lazy and left them on for the drive home. The inlet scraped a couple times, and pulling onto the driveway I ripped out the front twist ties, but no issues with the ducts or the splash gaurd, they are fine. Well, the duct is a bit chewed up, but the mounting holes are fine.

BTW, my car's back to stock. My setup is for sale if anybody wants it. $25 + shipping.

1 center duct with dual outlets & two 3' sections of 3" ducting (hose-clamped on to outlets as seen in pix pg4)
2 Single outlet ducts with 3" outlets (was to be used w/faux ducts if center solution didn't work) These were never used
1 6' (approx) section of 3" ducting left over, was not used
Enough twist ties to install it a couple times

let me know if anyone is interested.

cbender

Mike, my car doesn't see much daily driving or rain, but I really don't think this is an issue. No matter how you run the ducting, there's likely to be enough upward slope to keep anything that's not very light (like leaves) from getting very far, and the ribbing on the ducting seems to snag the leaves anyhow. Just my two cents, but I don't think you need to worry about this, and you can always jack the car up, pull the ducting off the dustshield and see if you've got a problem after running the ducts without a protective screen for a few weeks. That way, you can save yourself from solving a problem you may not have. Get some data first before you drop some bucks on it.