Cooling Fan CFM

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David Langston
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Joined: Sat Jul 27, 2013 7:28 am
Location: United States, North Carolina, North Carolina

Cooling Fan CFM

Postby David Langston » Wed Oct 02, 2013 1:50 pm

I have searched the forum for the answer to this question but all I find is the "highest you can". I have a two radiator setup approximately (13" x 21" each). Does anyone have any experience with this setup or something similar?

I was looking at a 12" SPAL (puller), one is rated at 867 CFM pulling approximately 7 amps. The other is rated at 1328 CFM and pulling 13 amps. The larger fans is almost double the price as the smaller one.

I was planning to add another battery for the fans and the water pump as I need to add some weight anyway.

Any help or experience would be appreciated.

David

Scott Newton
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Location: United States, New York, Chittenango

Postby Scott Newton » Wed Oct 02, 2013 2:20 pm

For solo or road racing? For road racing, you shouldn't need a fan (assuming your radiators are properly ducted).

For solo:
1) Put one of the 800cfm fans on each radiator
2) Make sure the fans are properly ducted
3) Plumb the radiators in parallel
4) Plumb in an inline electric water pump
5) Run the fans while the motor is running
6) Run the fans + pump while the motor isn't running

This is the setup I have, and I can get the water temps down to ambient temp + ~10 degrees between runs and rarely see more than a 20 degree temp rise during runs.

Scott Newton
Site Admin
Posts: 532
Joined: Mon Dec 29, 2008 9:01 am
Location: United States, New York, Chittenango

Postby Scott Newton » Wed Oct 02, 2013 2:28 pm

For the battery, if you figure each fan is drawing ~7A, while on course you should only have about a 14A draw. If you got a 14Ah battery you should be able to run the car on course with the fans running for about an hour. Then use an aux battery in the paddock for running the pump & fans.

I have an Odyssey P680 onboard battery, and a small "lawn and garden" paddock battery, and I have never had a low battery issue. One time I even left the car by accident with the pumps and fans going on the paddock battery for two hours between heats, and came back to find them churning along without any issue. I intend to downsize the P680 this winter as it's proving to be complete overkill, and I need to loose some weight.

David Langston
Posts: 40
Joined: Sat Jul 27, 2013 7:28 am
Location: United States, North Carolina, North Carolina

Postby David Langston » Wed Oct 02, 2013 6:05 pm

Scott Newton wrote:For solo or road racing? For road racing, you shouldn't need a fan (assuming your radiators are properly ducted).

For solo:
1) Put one of the 800cfm fans on each radiator
2) Make sure the fans are properly ducted
3) Plumb the radiators in parallel
4) Plumb in an inline electric water pump
5) Run the fans while the motor is running
6) Run the fans + pump while the motor isn't running

This is the setup I have, and I can get the water temps down to ambient temp + ~10 degrees between runs and rarely see more than a 20 degree temp rise during runs.


Good, that will be much less expensive and easier on the battery. I have one question about "properly ducted". I assume you mean a type of shroud that will pull air from the entire radiator versus just under the fan. I guess you could duct the discharge side if it was in a tight area, but just want to confirm.

Thanks for the info, just what I needed.
David

Scott Newton
Site Admin
Posts: 532
Joined: Mon Dec 29, 2008 9:01 am
Location: United States, New York, Chittenango

Postby Scott Newton » Wed Oct 02, 2013 6:08 pm

David Langston wrote: I assume you mean a type of shroud that will pull air from the entire radiator versus just under the fan.


That's the idea.

David Langston
Posts: 40
Joined: Sat Jul 27, 2013 7:28 am
Location: United States, North Carolina, North Carolina

Postby David Langston » Wed Oct 02, 2013 6:11 pm

Scott Newton wrote:For the battery, if you figure each fan is drawing ~7A, while on course you should only have about a 14A draw. If you got a 14Ah battery you should be able to run the car on course with the fans running for about an hour. Then use an aux battery in the paddock for running the pump & fans.

I have an Odyssey P680 onboard battery, and a small "lawn and garden" paddock battery, and I have never had a low battery issue. One time I even left the car by accident with the pumps and fans going on the paddock battery for two hours between heats, and came back to find them churning along without any issue. I intend to downsize the P680 this winter as it's proving to be complete overkill, and I need to loose some weight.


That is good to know, I was looking at the P680 and the P545. I may just go with the larger one as I do not have a weight issue, but that is a good thought. If I had to add weight, it could be in a more advantageous location.

I appreciate the info, always something new to think about.
David


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