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Old 03-06-2018, 02:24 AM   #41 (permalink)
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Quote:
Originally Posted by Tango Charlie View Post
What if we (somehow) ran a duct from the inner wheel well back to the rear of the car into a low pressure area.
Skin friction on the inside of the duct would likely steal all of the gain, Probably better to exhaust the front wheel wells like the Viper does. Turbine blade rear wheels could pull air from outside the body across the brakes, and out the low pressure area at the rear of the car, though, again, I don't know if the gain in efficiency at the rear of the car would be more than the power lost sucking the air through the wheels.

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Old 03-06-2018, 12:41 PM   #42 (permalink)
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This describes Morelli's FIAT Punto.

I can't find a picture onsite that isn't Photobucketed, but here's a relevant link: Simple Reduction of Drag due to the Wheels of Road Vehicles : Regert. 2nd hand is hearsay but it suggests:
Quote:
Adding a centrifugal fan to the rear wheels so as to draw air from the outside through the wheel yields a 5kW savings for the 240 W expended (20.8:1 advantage) by the following:

a: narrower wake due to air suction
b: a major decrease in base drag
c. suppression of jetting vortices by means of the Coanda effect.
Also:
Quote:
Probably better to exhaust the front wheel wells like the Viper does.

This plows the air out from under the car, and constitutes the outer fence of a diffuser.
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Old 03-06-2018, 01:20 PM   #43 (permalink)
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It occurs to me that cooling air for the brakes is often ducted from the air dam, I've seen that on a lot of track-only cars. Perhaps this would contribute to higher pressure in the wheel wells and ducting up would help cool the brakes more effectively.
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Old 03-07-2018, 11:25 PM   #44 (permalink)
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Back to the original question: On race cars, front fenders are vented on top to reduce lift. Jim Hall started it in 1966 (Chapparal 2E--the first high winged race car, among its many other innovations). For about a year, he let people believe the vents were to control tire temperature; clever guy, that Jim Hall.
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Old 03-08-2018, 08:04 AM   #45 (permalink)
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Quote:
Originally Posted by JackMcCornack View Post
Back to the original question: On race cars, front fenders are vented on top to reduce lift. Jim Hall started it in 1966 (Chapparal 2E--the first high winged race car, among its many other innovations). For about a year, he let people believe the vents were to control tire temperature; clever guy, that Jim Hall.
Interesting, I guess somebody had to be first.

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More Areodynamic & Air Management thinking - Wheel well body vents - FFCars.com : Factory Five Racing Discussion Forum
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Chaparral 2e front wheel well vents
CAR blueprints - 1967 Chaparral 2E Can Am OW blueprint

This is the earliest front wheel well venting that I remember ever seeing. Mid/late 60's. I had the slot car version at the time. Jim Hall worked closely with GM Engineers providing back door support, so the aero ideas might have even come from GM.
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Old 03-10-2018, 01:13 PM   #46 (permalink)
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duct

Quote:
Originally Posted by Tango Charlie View Post
Thanks, aerohead. I hadn't thought of the rain aspect. That would be a sight to see!

Racecars are so beguiling. They look so sleek and sexy, yet so many of their features don't translate to FE on our daily drivers.
But
What if we (somehow) ran a duct from the inner wheel well back to the rear of the car into a low pressure area...
The size of duct to make a difference would probably make it not feasible.
Without a pressure profile for the car,you'd be running the risk that air from behind the car would actually flow 'forwards' in the duct, towards a relatively lower pressure area up front.
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Old 03-10-2018, 03:57 PM   #47 (permalink)
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Similar to the hood 'vents' on the MGA. They flowed opposite to expectation.

There was an advertiser in Hot VWs in the 80s that had a picture they ran every month of Beetles racing in the rain. The rain flying off the windshield at right angles to the air flow reached two or three feet in the air! Would that I could find that picture today.

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