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Old November 29th 2011, 13:07
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Jadewombat Jadewombat is offline
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Join Date: Jun 2010
Location: Houston, TX
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Quote:
Originally Posted by beetle1303 View Post
Did a tiny bit of research thought...
most importantly

the air cooling the brakes is the air flowing under the car.

This is true for every vehicle that has enough ground clearance ( us for example). the opposite is true for purposely built track cars (i.e lmp class, gt2/3, and road going versions such as the radical sr3 etc)
Imagine top view of the car and the front at the top. the air goes under the front valance/splitter, under the front section (along the front wheel wells) and then it gets sucked outwards each side, due to the vortices created by the rotating wheel. Going super low requires another means of providing the brake disks of cooling air ( naca ducts on the bottom of the front splitter/ air intakes on the front surface of the car). In plain words the wheel works as a "fan" and sucks air out through its self (weird wheel covers on 934/5 P cars etc)

Jadewombat: if I understand your testing correctly there is a possibility that the positive value that you get is due to the flow reduction caused by the louvres on the front valance. Sounds weird doesn't it?? The louvres actually by letting air flow through them act like a "see through" fabric...its there supposedly covering up something but actually you can see through...
but what you see is a differentiated image of the original. If you had the normal front valance maybe you could still gain negative values (due to high turbulence) in the same area...

Chris
Well, did some more testing. I put my off-road and snow tires on the car as I'm having the five spokes updated with semi-slicks for this weekend. Anyhoo, I decided to test with the louvers completely blocked off and see what happened. Mind you, this was different than with the 215/55 16 sticky street tires I had before and the rallycross tires put the car higher off the ground. Even so:

-Louvers blocked off pulled -1" of vacuum under the car just behind the front sway bar
-Open louvers was not even registering under the car " " " (I'm guessing this was because I'm higher off the ground than before when I tested)

So, what next I thought to improve the front area?? High positive pressure in that are behind the louvers or no pressure and send all the air down and below the car. My first thought is sending that air below the car will cause lift, but it may be smoothing out airflow though reducing drag? I've decided to split the difference and installed some screen material just behind the louvers to let some of the air pass through.



In case you're wondering why I don't just install an air dam, my driveway is way too steep. Will retest once I get the front end aligned. I also drilled the inner edge of the fenders, trying to shave as much weight as I can and hopefully vent more of that trapped air out from under the fenders.

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'66 Bus(11-window, CLK rims, disk brakes, IRS, bags, hydr. clutch, Super-1600 w/injection)

Last edited by Jadewombat; November 29th 2011 at 22:46.
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