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Old 01-28-2008, 06:08 PM   #1 (permalink)
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Cooling system drag

Does anyone have any numbers on roughlyhow much drag the cooling system drag accounts for on cars? A percentage, or actual numbers for any car would be great.

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Old 01-28-2008, 06:24 PM   #2 (permalink)
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I used to have a link that talked about it, but I've since forgotten. Something like 10-20% or such? I forget exactly.
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Old 01-28-2008, 07:48 PM   #3 (permalink)
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Autospeed quoted a paper written by Volvo’s Dr Simone Sebben (SAE paper 2004-01-1307) about an un-named vehicle with a total drag coefficient of 0.29.

The list of parts of the car and their contribution to total drag show the cooling system as the worst offender:

Parts ... Percentage of Total Drag

Cooling package (including radiator, intercooler, oil cooler, etc) ... 33.4%
Exterior ... 31.7%
Front wheels ... 13.1%
Rear wheels ... 6.9%
Floor ... 6.9%
Rear Axle ... 3.1%
Engine ... 3.1%
Front Suspension ... 1.4%
Exhaust ... 0.7%



Source: Modifying Under-Car Airflow, Part 1

The only red flag in that data to my eyes is the label in the graph: "including radiator, intercooler, oil cooler, etc". If the vehicle in question actually has all those components, it likely has more cooling system drag than our small cars, which only have radiators.
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Old 01-28-2008, 08:02 PM   #4 (permalink)
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I spent some time wondering where/how the cooling system creates drag.

The only thing I can figure is, they would put a complete grill block over the grill and measure the drag vs. "stock" in a wind tunnel. Maybe remove the fan so you don't have whatever turbulence it adds.

If so, then anyone running a grill block is doing much better than the typical car. That's not news of course, but my point is that just because your car still has a cooling system doesn't mean that it's an aerodynamic disaster.
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Old 01-28-2008, 08:25 PM   #5 (permalink)
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Wow.
I just read the article, and also the "part 2" article referenced in part 1.
Part 2 is at http://autospeed.com.au/cms/A_2456/article.html

Part 2 takes us away from the cooling system drag question and deals with undertray design, construction, and benefits. Well worth reading. And their experience closely follows my own, though with a very different car.
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Old 01-28-2008, 08:34 PM   #6 (permalink)
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Yeah - Autospeed is great. Someone there is a bit of an aero aficionado, and they've done more than a few aero related articles. Their DIY fearlessness is cool too.
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Old 01-28-2008, 10:27 PM   #7 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Yeah - Autospeed is great. Someone there is a bit of an aero aficionado, and they've done more than a few aero related articles. Their DIY fearlessness is cool too.
That is Julian Edgar.
A car nut from way back and he knows his stuff as well.

The Prius was an ongoing project and it has been turbocharged and had extensive software mods to the vehicle as well.

An interesting project and I am sure Toyota followed this closely even if they didn't admit to it !

Cheers , Pete.
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Old 01-29-2008, 10:01 PM   #8 (permalink)
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Pete: sounds like you know the guy. Maybe?

I enjoyed reading his Prius turbo project as well.

Darin

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