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Old 08-07-2006, 09:46 AM   #1
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Radiator Drag

We all know the radiator causes hella drag, right? And we also know that a block is kewl for reducing that drag. However, what I'm wondering is does anyone have any information on how much drag it really is? I'm sure I've seen it somewhere, but I can't recall at all.

Reason I ask is I might be getting a half radiator and I'm wondering if it's worth having my friend fab up some mounts for it.
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Old 08-07-2006, 10:19 AM   #2
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Quote:
Originally Posted by SVOboy
We all know the radiator causes hella drag, right? And we also know that a block is kewl for reducing that drag. However, what I'm wondering is does anyone have any information on how much drag it really is? I'm sure I've seen it somewhere, but I can't recall at all.

Reason I ask is I might be getting a half radiator and I'm wondering if it's worth having my friend fab up some mounts for it.
Eh, do it... then you can get turbo :P

Or just send me the radiator so i can make the turbo-alternator one day
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Old 08-07-2006, 10:28 AM   #3
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I'm pretty sure I could fit a turbo in with the full radiator, but I want the room just for bling factor as well. I'm pretty sure that one day I'll have a budget build crap crx for going to the track with and just pimp this one for FE/EV.
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Old 08-07-2006, 10:38 AM   #4
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One of the SAE papers that I have is dedicated to cooling-related drag. I'll take a look at it later to see if it offers any relevant info.
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Old 08-07-2006, 10:39 AM   #5
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Is it something of a linkable nature? I'd want to read the whole thing just to have the thing read,

Knowledge is empowering, after all.
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Old 08-07-2006, 11:42 AM   #6
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Cooling drag is significant enough that Mercedes has an E class with an active grille to match airflow to cooling needs, rather than always pay the price for airflow for worst-case cooling requirements:
http://www.sae.org/automag/globalvehicles/06-2002/

Active grilles are common on aero-aware concept cars.

For some numbers, try here:

http://www.tfd.chalmers.se/~lelo/rva...icles-drag.pdf

(I'm on dial-up at the moment and didn't want to wait for it to open to make sure the numbers are in there, but I think they are.)
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Old 08-07-2006, 06:20 PM   #7
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I read through some of those papers and haven't found anything particularly pertinent. They focus more on cooling efficiency vs. aerodynamic efficiency, and as such don't say anything like "cooling air requirements account for xx% of aerodynamic drag." I haven't read word-for-word, though. There might be something non-obvious in there that I have yet to find.
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Old 08-07-2006, 07:36 PM   #8
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It's in there...

Quote:
Contribution to drag in a car comes from several factors, but in a general view can be considered having the following elements:

Surface friction, underbody and excrescences 0.08
Normal pressure 0.10
Effects of wheels 0.08
Eng cooling 0.03
Trailing vortex 0.01

Total 0.30
I've also seen an excerpt from a paper discussing Volvo aerodynamics claiming cooling drag represents 30% of total drag (but it doesn't say what kind/shape of Volvo...) I suspect for most of our small 4-cyl non-turbo cars, 10% is closer to the mark.
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Old 08-07-2006, 07:39 PM   #9
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Half radiator here I come!
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Old 08-08-2006, 06:24 AM   #10
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Ever look at the radiators of large semitrailers? They all have what appears to be a canvas with a V shaped notch covering the radiator. At least in winter. Is reducing radiator drag that simple?
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