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Old 09-14-2019, 12:44 PM   #2 (permalink)
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Originally Posted by hat_man View Post
Hello again everyone.

Having an hour drive to work everyday on the same roads sort of puts me in "auto pilot" and I can let my mind wander through crazy ideas. This is another one. I have no clue if it has any merit at all, but I thought I would at least share it and maybe learn something new again from you all.

This came from reading the thread about tire deflectors and spats here:

Seeing the pictures of how short vertically some of the stock deflectors/spats are on some of the cars in the pictures, while maybe not the perfect shape or height, they must have some advantage or they wouldn't be there. Some only looked to be 1 1/2" tall at most. So that got me thinking, if such a short piece of plastic can move enough air from the front of the tires, can the same concept be used in other places for some small advantage.

So this is what I came up with. If you used something like aluminum angle trim (mainly because it's cheap and easily installed) on the underside of a front under tray, could it help? Some people (me included) don't have the skill or ambition to fabricate a full length under body tray. But may try a half or just front tray that extends to just behind the front wheels. The picture probably explains where my head is at better than my words. Dotted lines = longer tray/longer deflectors.

If you extend the "deflector lines" out they would be just outside the rear tires, similar to the large deflectors you see on semi trucks. So, just how far off base am I? could this help keep some of the air away from the under body stuff like differential and rear bumper on older vehicles or pick up trucks?
The 'spats' cause the air to jump the wheelhouse tire-flop void under the car (upside-down) then re-attach to the belly pan sections immediately aft.
Unless you have a streamlined structure back there,there is no surface on which the airflow can reattach to,and you just have turbulence and drag.
If you had belly-pan up to the rear axle area and a rear bumper as low as the belly,you could get the air to create a pool of dead air within that span without any spat.However,for the lowest drag,you'd want to fill this area in with at least a level panel.Subaru tested this in 1985 and it was shown to definitely lower drag.An up-swept diffuser would be the best.
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