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> Another silly idea, ducted fans for a radiator!
TonyAKAVW
post Nov 10 2005, 05:36 PM
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So I've been thinking about different ways to get air up to the radiator in the subaru conversion where the radiator is in the engine bay. The standard way to do it is to have a couple of normal radiator fans sucking air from beneath the car.

Here's another idea... What if I constructed an array of ducted fans as in the diagram below. Basically they would force air up the shroud and through the radiator. One advantage to this is that it would take advantage of the entire surface of the radiator, rather than a round section that a fan would push through.

Something I'm trying to figure out is the conversion between thrust and CFM of air moved. Most of these fans are for hobby RC airplanes and are rated in ounces of thrust, rather than moved volume of air.

-Tony



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Andyrew
post Nov 10 2005, 05:42 PM
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What do they equal in CFM?

I would want some forced air in there as well... like a scoop, like scotts..
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bondo
post Nov 10 2005, 05:42 PM
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QUOTE (Andyrew @ Nov 10 2005, 04:42 PM)
What do they equal in CFM?

I would want some forced air in there as well... like a scoop, like scotts..

A PVC elbow for each fan! (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)
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WRX914
post Nov 10 2005, 05:46 PM
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Looks like it should work...

Would the fans be on constantly? If so, what are your plans around the fan noise?
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lapuwali
post Nov 10 2005, 05:47 PM
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I've ruminated on a chimney-effect idea, which it looks like you may have room for. Duct the outlet so the air has to rise, and esp. if you made a crude venturi at the exhaust end, you should get a natural convection draw using no power at all. If it exhausted just aft of the rear window, you should get even more of an effect at speed, as that should be a significant low pressure area.

I have a pet theory that too many people spend too much attention to the inlet side of the radiator and ignore the outlet side.
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Mueller
post Nov 10 2005, 05:47 PM
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do you still plan on installing "puller" fans to the radiator?
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SLITS
post Nov 10 2005, 05:48 PM
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Add a couple more and you could have a 2J Sucker Car (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
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TonyAKAVW
post Nov 10 2005, 06:01 PM
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I had actually thought of having the exhaust of the radiator ducted up to a GT-style engine lid and exiting right below the rear window. Instant defogger and a good place to exit the air. It wouldn't take a whole lot more sheetmetal work to make an exhaust shroud. Fiberglass would be a nice way too.

The whole idea here is that I want to get away form having to use a scoop. The thought of having a scoop below the car worries me a little. Especially if I want to ever lower the car (which I do).

Fans on the exit side would be a good idea too. However at this point I'm starting to suck up a lot of amps to drive all these fans. The ducted fans each seem to draw something like 10 amps, but that could probably be throttled back a bit with a PWM controller.

This particular fan pushes nearly 10 oz of thrust, but what does that mean? And it also draws 12.5 amps. I could easily fit 7 of those, so that is up to 87.5 amps, or 1050 watts. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

-Tony

edit....

Yes. about the sound. I think the sound of these would dominate over the sound of the engine... that would suck. literally..
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Aaron Cox
post Nov 10 2005, 06:04 PM
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QUOTE (bondo @ Nov 10 2005, 04:42 PM)
QUOTE (Andyrew @ Nov 10 2005, 04:42 PM)
What do they equal in CFM?

I would want some forced air in there as well... like a scoop, like scotts..

A PVC elbow for each fan! (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

LMFAO! (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)
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Andyrew
post Nov 10 2005, 06:15 PM
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what if you shrouded scoops to the sides of the car? put some mesh in it, and throw some fans in it?

also what about dirt, leaves and ect? The fans would just suck those things from the ground if they are aimed at the ground...... Especially at low speeds.
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jim_hoyland
post Nov 10 2005, 06:17 PM
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Tony,

I've got a couple of in-line Detmar brake duct fans that might fill the bill. PM me if interested
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Rand
post Nov 10 2005, 06:18 PM
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The stock air-cooled setup pulls the cool air from above and exits below... Isn't part of the reason because of the difference in air pressure between the underside and top of car - especially at speed? In other words, by trying to pull cold air from below and exit at top, are you fighting the natural air pressure? Wouldn't the air flow considerably easier from top to bottom? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif) I dunno, just throwing more ideas around...
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jd74914
post Nov 10 2005, 06:21 PM
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it seems like it should be a low pressure area behind the targa bars so I would think that air would like to rush that way (IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)
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Aaron Cox
post Nov 10 2005, 06:22 PM
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QUOTE (Rand @ Nov 10 2005, 05:18 PM)
The stock air-cooled setup pulls the cool air from above and exits below... Isn't part of the reason because of the difference in air pressure between the underside and top of car - especially at speed? In other words, by trying to pull cold air from below and exit at top, are you fighting the natural air pressure? Wouldn't the air flow considerably easier from top to bottom? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif) I dunno, just throwing more ideas around...

i thought there was a HUGE negative pressure at the rear window....

IE air rushing over the targa sucks air from the engie bay (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif)
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Rand
post Nov 10 2005, 06:24 PM
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The expanded metal grill in the engine lid is the air INTAKE on a stock 914, is it not? The impeller is above the engine seal, so it sucks cool air from above, right?
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Aaron Cox
post Nov 10 2005, 06:25 PM
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QUOTE (Rand @ Nov 10 2005, 05:24 PM)
The engine lid is the air INTAKE on a stock 914, is it not?

makes sense... but id think of it like a cowl induction on a nova (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

or the air flaps under the 914, that create yet another neg. pressure area.
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Andyrew
post Nov 10 2005, 06:28 PM
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the expanded metal grill in a stock 914 has a raintray under it..

the air inlets on a 914 are the small grills about 2x4 inches on each side.

IIRC

havent seen a stock 914 in a while (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
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TonyAKAVW
post Nov 10 2005, 06:29 PM
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It is the intake, but its probably not the best area for an intake...

Scoops on the side would be great, but the ducting gets complicated pretty quickly. Also, I'm not so sure I want ducts on the side of my car...

I know that way back when, someone had numbers and measurements around the 914 for air pressure while driving...

-Tony
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Aaron Cox
post Nov 10 2005, 06:30 PM
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QUOTE (TonyAKAVW @ Nov 10 2005, 05:29 PM)
I know that way back when, someone had numbers and measurements around the 914 for air pressure while driving...

-Tony

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Rand
post Nov 10 2005, 06:31 PM
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Yes Andyrew, but there is a gap all the way around the rain tray so air still comes in above the tray and around all sides. While it can be argued that removing a tray will increase air intake, the tray doesn't block / restrict air flow to just the 2x4" sides.
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