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Old 11-24-2014, 05:26 PM   #21 (permalink)
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Quote:
Originally Posted by 2000mc View Post
I think the bottom breather setup, simmar to the corvette, is about as different as you're going to find with a radiator in the typical placement. Many race cars will use that location and duct air out the hood...
The race version of the car has an unusual bumper with a significantly smaller grill than the road version:





Of course it probably wasn't designed for fuel efficiency, but low drag would have been important.

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Old 11-24-2014, 06:57 PM   #22 (permalink)
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alternatives

Quote:
Originally Posted by Nigel_S View Post
Yes, fun

I wasn't expecting an answer specific to my car or even a general one for the model, just wondering if anyone had looked into the alternatives and what is worth trying. Looks like everyone takes the cooling air in through the grill though and have never tried anything else!
For the traditional radiator placement,the lowest entropy approach is to utilize the ram pressure and thereby maximize the pressure differential available.Cooling systems which contribute no more than 2% to overall drag can be realized in this manner.
Harvesting air from any other location implicates the addition of artificial pressure and starts to violate the second law of thermodynamics, as far as efficiency goes.
It's the tyranny of singularity in action.
If your fan ever fails,you've conceivably just trashed a $3,000 long block.
It's the primary driver for 'traditional' systems.
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Old 11-24-2014, 08:19 PM   #23 (permalink)
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Originally Posted by aerohead View Post
For the traditional radiator placement,the lowest entropy approach is to utilize the ram pressure and thereby maximize the pressure differential available.Cooling systems which contribute no more than 2% to overall drag can be realized in this manner.
I think 2% drag is still consuming more energy than the fan is consuming even if you take into account the inefficiencies of generating the electricity, however I'm making a lot of guesses to get to that and I'm not sure how much drag use of the fan could save, hence the question...

Quote:
Originally Posted by aerohead View Post
Harvesting air from any other location implicates the addition of artificial pressure and starts to violate the second law of thermodynamics, as far as efficiency goes.
It's the tyranny of singularity in action.
If your fan ever fails,you've conceivably just trashed a $3,000 long block.
It's the primary driver for 'traditional' systems.
Thankfully the designers of the car decided to remove that singularity and installed two fans which operate at different temperatures and off different sensors, plus I have a coolant over temperature alarm, plus if the temperature continues to rise the coolant pressure cap will release a cloud of steam and soon after that the low coolant alarm will illuminate. Only if you continue to drive after all that will you cause any damage.
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Old 11-24-2014, 10:12 PM   #24 (permalink)
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Quote:
Originally Posted by Nigel_S View Post
I have a variable speed fan that keeps the coolant returning from the radiator 10 degrees C below the thermostat opening temperature thus allowing the thermostat to mix warm and cool coolant and keep the engine temperature constant.

In normal running the fan stays off for 10-15 minutes and then runs slowly, if I go up a steep hill it speeds up. The amount of power used is typically 15W while the grill block appears to be saving several KW. So even though alternators aren't 100% efficient it doesn't matter as long as I save more than I use...


Thanks for the search tip, helps to know what to search for.

They still seem to have the intake in the high pressure area though, and in a place my car doesn't have. The obvious places to put a hole and maybe flap on my car are in the lower grill block or in the undertray in front of the radiator which is a low pressure area so would need some extra effort from the fan possibly in return for gains in aerodynamics.
A variable speed fan which controls the outflow coolant temperature.
WAAAAAY NEAT!!!!!! and first I have read about that being a factory design.

It means you have avery stable temperature of the coolant entering the engine, which without that system can vary by as much as 90 degrees sucking heat energy out of the engine when it's cold.

I would consider blocking the upper grille, which looks like it is integral with the hood and opens with same.

We think of cooling fans as either on or off, yours is a generation advanced from the old all or nothing fans.

Whatever you do block, start gradually, so as to avoid compromising the integrity of the super neat system you have already. Basically when temps drop below a certain point you want to restrict airflow due to the much cooler air flowing.

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mech
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Old 11-25-2014, 01:15 AM   #25 (permalink)
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Quote:
I wasn't expecting an answer specific to my car or even a general one for the model, just wondering if anyone had looked into the alternatives and what is worth trying. Looks like everyone takes the cooling air in through the grill though and have never tried anything else!
Well, no. 2000mc covered a lot of the examples I can think of. I will add the Edison2 that uses a gill-slit at the widest part of the body where the air is moving the fastest and is still in laminar flow. And of course my car is completely sealed in the front and take in air under the backlight. Here's someone who was looking at front engine/rear radiator:

http://ecomodder.com/forum/showthrea...ery-26356.html

Two-pager from 2008

http://ecomodder.com/forum/showthrea...anks-5796.html

...and

http://ecomodder.com/forum/showthrea...ear-21405.html
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Old 11-25-2014, 07:25 PM   #26 (permalink)
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2%

Quote:
Originally Posted by Nigel_S View Post
I think 2% drag is still consuming more energy than the fan is consuming even if you take into account the inefficiencies of generating the electricity, however I'm making a lot of guesses to get to that and I'm not sure how much drag use of the fan could save, hence the question...


Thankfully the designers of the car decided to remove that singularity and installed two fans which operate at different temperatures and off different sensors, plus I have a coolant over temperature alarm, plus if the temperature continues to rise the coolant pressure cap will release a cloud of steam and soon after that the low coolant alarm will illuminate. Only if you continue to drive after all that will you cause any damage.
The 2% is the passive penalty when driving at 40-mph or above,when no fan is necessary.It is just for the friction and turbulence of the heat exchanger and ducting.It represents the 'ideal'.The minimum of which cannot be improved upon.
The electric fan(s) remove the fans parasitic from the engine,and put it on the electrical system.
The 2% + loss is still there,plus any inefficiencies of the alternator drive,the alternator itself,powering the electric motor of a given efficiency,driving a fan of a given efficiency,through a restriction of some static pressure differential which would be dependent upon design.If you don't take advantage of the ram air,it is scientifically impossible to achieve lower than a 2% loss.

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