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914World.com _ 914World Garage _ Aerodynamic Question

Posted by: race914 Mar 14 2006, 02:16 PM

I was watching a special on last years ALMS series at Sebring, and during a pit stop for the Corvette team, you could see the light coming through the front wheel well vents onto the tire.

I had always assumed the vents like on the Corvette C6.R and/or Porsche 935s were to equalize high pressure built up in the wheel well.

Then I recalled the http://www.914world.com/bbs2/index.php?act=ST&f=2&t=46489 thread noted that the front wheel wells are a low pressure area.

Can anyone help out?

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Posted by: ArtechnikA Mar 14 2006, 02:24 PM

it's all relative...

yes, the upper-fender vents (or the aft-fender vents on the RSR's) are to vent the nose and prevent lift.

yes, the wheel wells are low-pressure areas - relative to the front of the spoiler (oil cooler air inlet).

and if the oil cooler is venting into the fenderwell, along with the brake heat, anything you can do to get the hot air out is A Good Thing. which is yet another reason 935's ran with wheel turbines on their BBS wheels...

Posted by: race914 Mar 14 2006, 03:27 PM

Thanks for the reply and putting the 'low pressure' comment in the 'oil cooler' thread into context. I wasn't looking at it from the right point of view.

Your right about everything being relative.

My financial advisor told me it's easy to make a small fortune day trading stocks.... You just need to start with a large fortune!

Posted by: TimT Mar 14 2006, 04:01 PM

Here is some info from Porsche wind tunnel testing.

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Posted by: East coaster Mar 14 2006, 04:06 PM

Wow............facts are cool !!

Posted by: race914 Mar 14 2006, 04:11 PM

Great diagram showing the difference in low pressure areas with & without louvres.

And again I had it backwards, the end objective of the vents are to negate the low pressure areas going over the car, not to 'release' the high pressure in the wheel wells...

Learn something every day!

What is the source document for the Porsche Wind Tunnel testing info?

Posted by: Brett W Mar 14 2006, 04:12 PM

Tim
Where did that info come from?

Posted by: Terrance Mar 14 2006, 04:15 PM

http://www.mulsannescorner.com

Posted by: TimT Mar 14 2006, 04:18 PM

Another set of figures from testing the 936, in this case the louvers are taped,up and drag decreases, and front lift increases.

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Posted by: TimT Mar 14 2006, 04:20 PM

The info I scanned is from a book "Porsche racing cars of the 70's"

By Paul Frere

Mulsannes Corner has some great areo info also.. I had forgotten about that site.

Posted by: race914 Mar 14 2006, 04:31 PM

Thanks Guys... Great info.

I just ordered:

Race Car Aerodynamics: Designing for Speed

and

Competition Car Downforce

Posted by: TimT Mar 14 2006, 04:38 PM

I have both those books, they are very handy and informative. Im not sure if Freres book is still being published

Posted by: lapuwali Mar 14 2006, 04:45 PM

Frere's book is out of print, but Barnes & Noble can order it used through their network. Just snagged a copy.

Posted by: Air_Cooled_Nut Mar 14 2006, 11:52 PM

There's this as well:
http://www.icbm.org/cmgallery/displayimage.php?album=23&pos=5

Posted by: race914 Mar 15 2006, 08:50 AM

QUOTE (Air_Cooled_Nut @ Mar 14 2006, 09:52 PM)
There's this as well:
http://www.icbm.org/cmgallery/displayimage.php?album=23&pos=5

Another good diagram! Gives a good visual on why the 935 front fender louvre placement is slightly ahead of the tire's verticle center.

Anyone done front wheel well louvres on their 914? Got any pics?