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Old 12-22-2008, 08:10 PM   #31 (permalink)
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Hello,

The very front of the car (the grill and bumper) is a high pressure zone, and it deflects much of the air flow up and over much of the hood; making the hood a low(er) pressure zone than the front. On my xA, which has the hood sloped down, this is still the case. The upper half of the windshield is also high pressure; but the base of the windshield is a low(er) pressure zone, as well.

The reason I know this the case on my car anyway, is when there is loose (light and fluffy) snow around the windshield wipers, it stays put; unless there is a gust of wind from the side.

In any case, the back of the hood/base of the windshield is a lower pressure zone than under the car. There are other threads that quote aerodynamic reference books showing that intake down low on the front and the exhaust on the back of the hood is the most efficient way to move air through a front radiator.

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Old 12-23-2008, 02:21 AM   #32 (permalink)
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autospeed had a great article on bonnet vents.

however i'm inclined to think from their results and from the placements of functional vents on production cars half way the hood is a better place the pressure difference with the front is much greater there than just ahead of the windshield. the back of the windshield is generally the place where the interior cooling air INTAKES are.

perhaps raising the hood at the back might still work because of the sheer size of the resulting gap, but relative small extractors early on the hood can do the same thing
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Old 12-23-2008, 09:44 AM   #33 (permalink)
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If I had time, money, and a workspace I'd be working on a way to duct my rad. I mean, look at all this space:



If I could move the top supports out towards the front, I could angle it nicely to duct it out to the hood. Forget money, I just need time and a workspace. *sigh*
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Old 12-23-2008, 12:58 PM   #34 (permalink)
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Coroplast would make some nice ducting material, applied with duct tape.
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Old 12-23-2008, 03:09 PM   #35 (permalink)
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Quote:
Coroplast would make some nice ducting material, applied with duct tape.
badum bum
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Old 12-24-2008, 02:10 AM   #36 (permalink)
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is that a concrete undertray? seems like any sort of ducting might include or double as one too
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Old 09-10-2013, 05:31 PM   #37 (permalink)
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Another article on Radiator ducts, is about aeroplanes, but principles are the same, thought it best to tag on this thread:
Contrails ! Radiator aerodynamics

Regarding adjustment of mass flow, thought this comment was relevant:
Quote:
In theory, it should be necessary to alter the intake opening at the same time as the exit.
In practice, it has been shown that once the intake cross section is 30 to 50% of the radiator block frontal area, the volume flow depends only on the exit area.
Hence the regulation by control of the exit area by means of cowl flaps, preserving the static pressure at the front face of the radiator.
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Old 09-10-2013, 05:43 PM   #38 (permalink)
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Quote:
Originally Posted by lunarhighway View Post
is that a concrete undertray? seems like any sort of ducting might include or double as one too
probably see a 10% improvement from concrete to maybe,.........oh I don't know..........


2x4s.........
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Old 09-10-2013, 05:44 PM   #39 (permalink)
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sorry..........

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