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Old 03-30-2009, 07:50 AM   #1 (permalink)
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grill "shield" rather than block?

would it be possible to create a grill shield, rather than a full grillblock?

something that sits in front of the grill, but doesn't actually reduce the open area of the grill, or at least doesn't seal the grill but rather prevent a direct ram effect.

the idea is that at speeds the air would not be rammed into the grill but bounce of the shield, skip over the openings at the side and continue around the car, just like a full grillblock

at low speeds when airflow is requires and the fan kicks in it will suck in the air along the sides, as if the block would not be there.


now is this possible?, because the pressure in front of the car will be higher than the pressure in the engine bay, so will air still be forced around the block and enter the radiator, or will the air in fact skip over the edges...

does anyone know the science behind it?

also as an extention of this it might be possible trough a removal of my grill incert etc, to relocate my topgrill opening from a forward faceing position to an upward faceing position... this would bring it into an area where the flow accelerates over the hood... this might bring the pressure below that of the engine bay so that at speeds the air entering the bottom grill would be sucked out trough the topgrill... it would pass over the radiator rather than trough it...wich seems like a much lower drag path... would this be desirable, from an aerodynamic perspective and how much would this impact cooling?

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Old 03-30-2009, 09:33 AM   #2 (permalink)
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I would think it would be possible, but not as effective as a partial grill block. Try it out and get back to us.
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Old 03-30-2009, 12:25 PM   #3 (permalink)
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You have to get air through the radiator to use all the surface area it is designed to provide. Adding turns and reducing pressure differentials will reduce air flow and require power from the fan and engine. To minimize losses, use ram air in and low pressure extraction, with a continuous smooth duct, and control the size of the entrance, reducing it in winter.
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Old 03-30-2009, 12:49 PM   #4 (permalink)
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maybe i should specify what my personal goals are and why i'd like this setup to work.

my car already has an optimised grill with a small lower grill and a partly factory blocked topgrill that sits rather deep, further blocking from behind on the topgrill alone worked nicely (i haven't touched the bottom one), but it showed that on a normal day with nice weather the car will get very hot only when stuck in traffic and not moveing... at a normal speed the temp will brop and stay quite acceptable... so basically what i'd need is an additional air intake for those occasions when the fan comes on. these are very rare so even if a grillblock would increase the fan on time it's still a fraction of my overall driving. still when it does come on i want it to be able to do it's job.... i'm not to keen on relying on electronics for this; but as there's no ram effect when the fan comes on the new opening would not have to be set up for this... the fan should just be able to suck in the factory spec ammount of air.
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Old 03-30-2009, 01:03 PM   #5 (permalink)
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Kinda like this? My former daily driver, now semi-retired.



This one's 2.7 mm lauan plywood (about 1/8 inch for the metrically challenged), primed with oil-base house primer and then an appropriate shade of blue automotive touch up spray paint. It flexes easily; is mounted onto stud blocks on the radiator support at the four corners. Those four points force the curve.
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Old 03-30-2009, 03:46 PM   #6 (permalink)
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sort of

in my case i think it might look like this


in this pic you see the actual open grill so the open area of the top grill is much smaller than it visually looks, therefore if the "shield" would stand only a short distance before the grill, the resulting opening would be about the same as the open grill. you also see that the totall grill opening on my car is really not that big so i have to be carefull as the car gets hot pretty fast
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Old 03-30-2009, 05:29 PM   #7 (permalink)
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i did something like this

http://ecomodder.com/forum/showthrea...lock-7508.html
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Old 03-30-2009, 07:06 PM   #8 (permalink)
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shield

Ford of Australia created a grill in the 1980s which behaved as you describe.As velocity increased,the airfoil sections which made up the grill would begin to stall.The turbulence created a formidable barrier to increased flow volume,effectively pinching off the airstream to the required minimum.
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Old 03-31-2009, 03:29 AM   #9 (permalink)
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that's the sort of thing i'm looking for....you wouldn't by any chance have a picture off this setup? i've been looking for images of stalling wings for inspiration but a totally different leading edge would be needed for the sort of separation a grill would require.

i assume some premium carmakers comming out with low drag cars secretly employ these tricks to arrive at such a low Cd with quite large grills
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Old 03-31-2009, 04:11 AM   #10 (permalink)
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I think that was the XE Falcon -
Ford Falcon XE

Ford still make Falcons here in Australia.

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