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Old 11-03-2018, 08:53 AM   #1 (permalink)
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Radiator airflow - above or below?

Imagine if you will that your car has an engine behind the driver and a radiator up front in the nose.

In a perfect world of choices, do you vent the rad into the airflow above the hood, or under the car?

Below is a video where they chose to dump the air under the car. Just watch it for a few seconds, sorry about the ad.

https://youtu.be/63-oQq6XLhI?t=164

And below is venting for a front mounted oil cooler, a situation seen on many exotic racing cars (radiator typically) going back to the 1960's.

My version of the thru the hood venting... - Pelican Parts Forums



I imagine that dumping air below into an already compressed and often disrupted airflow and under low flow high pressure as shown in the first example with video is better than introducing more flow over the hood - up to a point. That point comes at high speed...........guessing normal highway speeds and beyond where uplift can be a problem.

At that point, safely and handling trump smooth aero over the top of the car's hood.

Down-force, it's a good thing in moderation.

Above or below, that is the question.

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Old 11-03-2018, 10:57 AM   #2 (permalink)
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No need to imagine anything. My dad first car - Skoda 105 - had exactly this setup. Rear engine, front radiator, air vented under the car. The reason behind was generous luggage space (boot) in the front. The price was (well known) lift on the front axle at high speeds. But, hardly anyone drove more than 80 km/h at these times anyway. (there was a joke that 105 does not refer to engine ccm, but top speed, downhill with rear wind)
Some Triumphs have vented through wheel well, iirc

Last edited by seifrob; 11-03-2018 at 01:00 PM.. Reason: added units km/h not to confuse you MPH oriented oned
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Old 11-03-2018, 11:50 AM   #3 (permalink)
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Quote:
Originally Posted by seifrob View Post
Skoda 105
I did a graduate course study in the Czech Republic in the early 1990's.

My course instructor drove a Miata back home and had three of us students in a Skota on some country roads near the Polish border. He said the handling was great considering how much weight we had in the car.

I suspect the downward venting Porsche is a burning tire patch 0-60 car based on the early part of the video.

I don't think this was intended as a high speed track car, rather it is an attention getting tire smoker.

The only down force he is concerned about is his foot on the gas pedal.
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Old 11-03-2018, 12:11 PM   #4 (permalink)
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Hucho would vent the radiator airflow over the bonnet

Vekke had such a set-up on his Seat Ibizanope, make that a Cordoba station wagon

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Old 11-03-2018, 12:19 PM   #5 (permalink)
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above or below

For the 1976-78 CNR 'banana' car,Morelli and Pininfarina did both.
Four extractors,2-up,2-down,were positioned,oriented,and sized,such that the air escaped into lower pressure air,blending at exactly the same velocity as the adjoining air stream,for a 'seamless' merge,and lowest drag.
It's the best cooling system I've ever seen for a 'passenger' car.
For racing cars,the Olds AEROTECH would represent a good illustration of ideally-ducted,airtight design.(it's a ground-effect car,so all aspirations occur on the upper body).
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Old 11-03-2018, 01:06 PM   #6 (permalink)
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Quote:
Originally Posted by kach22i View Post
I did a graduate course study in the Czech Republic in the early 1990's.
Lucky you! These were wild, dangerous, but wonderful times. A lot of euphoria in the air, adventure without borders.

And I bet you felt like in some wild dream set 40 years back.

Last edited by seifrob; 11-03-2018 at 01:17 PM..
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Old 11-03-2018, 08:10 PM   #7 (permalink)
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Quote:
Originally Posted by seifrob View Post
Lucky you! These were wild, dangerous, but wonderful times. A lot of euphoria in the air, adventure without borders.

And I bet you felt like in some wild dream set 40 years back.
I was recently married but did not mind looking at the beautiful Czech women, and the architecture that I was there for was very cool too.

I was told it changed quite a bit from just a year or two prior by one of my classmates, I can only imagine the pace picked up even more after I left. I loved that it was not spolied but did eat at the New York Pizza and McDonalds near the end of the six weeks. Only so much goulash an American can eat. I do remember the pivo, Děkuji.

Regarding the topic, I wonder if the Aerotech intakes and exhausts would work half as well under the belly.

Photos of 290mph speed record shattering Oldsmobile “Aerotech” : theCHIVE



FYI: Aerohead, some of our old Photobucket images seem to be reappearing.

https://ecomodder.com/forum/showthre...e-29689-6.html
Quote:
Originally Posted by aerohead View Post
Morelli spent $100,000 or so at Pininfarina to optimize the extractors on his 1978 CNR 'banana' car.
Another image from page one of that old thread.

Quote:
Originally Posted by freebeard View Post
My mention of pic#1 was distracting; I meant what range of vehicles are you considering. I assume front-engined and water cooled.



.................
From page 5:
Quote:
Originally Posted by aerohead View Post
If you look directly above the front wheel,near where the windshield edge would be,you'll barely make out a slot which is oriented with the color dye solution.
I believe that there are corresponding slots below as well.
Morelli divided the cooling air coming out of the engine bay into 4-different streams and experimented with duct size and geometry such that the air escaping out these slots blended perfectly with the surrounding flow field.
An isobaric/velocity contour map was created by pressure tap and velocity pressure measurements (you see this today in color CFD mapping),and working with Bernouli's Theorem,arrived at duct sizes which provide the air volume at a matched velocity,given the pressure environment its flowing into.
This cannot be modeled analytically yet and must be done by trial and error in the tunnel.(very expensive!)
If you get it wrong:
*air can flow into the exits
*jets can be formed which trigger shear-induced vorticity,eddies,turbulence
*Transverse-vectored jets can contaminate the boundary layer,trigger separation,along with the formation of form additional vorticity.
My opinion is that 'nailing' this sort of thing is completely outside the scope of what individuals can pull off without major money.
*air can stall within the duct
EDIT:
Click on the images in this website link below, they get huge and you can see every detail of the "banana car".

Concept Car of the Week: Pininfarina CNR-PF (1978)
by Rufus Thompson 12 Oct 2012
https://cardesignnews.com/media/impo...86/252086.html

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1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
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Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html

Last edited by kach22i; 11-03-2018 at 08:43 PM..
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