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Old 11-13-2018, 11:07 AM   #1 (permalink)
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Block grille BMW e36

Hello, I have a bmw e36 and wich it's the Best option for aerodynamics:
Block the upper o lower grille.



I guess it's better to cover up.
But above, the most direct air reaches the radiator.
But if I Block the lower grille, less air will pass under the car.

Any opinion?

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Old 11-13-2018, 11:21 AM   #2 (permalink)
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Its usually better to block the upper grill.
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Old 11-14-2018, 08:58 AM   #3 (permalink)
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As I understand it, at speed (while traveling down the road) there is an air pressure build-up at the front of the car as the air is compressed.

A lot of that pressure is at the lower chin because the air at the top part of the front has an easy escape path up and over the hood, there is acceleration of the air and lowering of pressure when this happens.

Meanwhile the air attempting to escape under the car is not allowed to expand or escape and remains compressed under high pressure.

Look at your radiator, all those little fins.

Do you think air is going to easily pass through if there is no pressure behind it to back it up?

Or do you think higher pressure air has a better chance of being pressed though it?

NASCAR Computational Fluid Dynamics (CFD) Surface Pressure Plot
https://robrobinette.com/S2000Aerodynamics.htm

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In the CFD pressure plot above note these standard pressure areas common to most cars: very high pressure (red) bubble on the nose of the car, the slight low pressure (aqua) over the hood, the moderate pressure (yellow) bump at the hood/windshield junction and the very low pressure (dark blue) area above the roof of the car where most of the lift is generated. Graphic by Michael Waltrip Racing.

Short answer: Upper grille block is the norm around here.
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Old 11-17-2018, 10:03 AM   #4 (permalink)
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Thanks all.
Now I blocked the upper grill and put 1" diffuser front wheels.





The car has dropped about 2inch, and has m3 style front bumper.
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Old 11-17-2018, 01:15 PM   #5 (permalink)
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Any gains?
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Old 11-18-2018, 05:57 AM   #6 (permalink)
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Any gains?
At the moment only a few km traveled. And here the weather is too variable.
I need tested with more km. I would like to achieve 35mpg on winter.
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Old 11-18-2018, 08:29 AM   #7 (permalink)
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https://youtu.be/NmzLaaFQjiQ

You could always try this.
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Old 11-18-2018, 08:52 AM   #8 (permalink)
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Quote:
Originally Posted by teoman View Post
https://youtu.be/NmzLaaFQjiQ

You could always try this.
Haha, funny video, but my motor is NA. 1.796cc 16v 140hp.
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Old 11-18-2018, 09:28 AM   #9 (permalink)
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You could do it to the radiator. If your commute is diverse, or you have that one hill that has the potential to overheat.
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Old 11-18-2018, 03:24 PM   #10 (permalink)
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Quote:
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You could do it to the radiator. If your commute is diverse, or you have that one hill that has the potential to overheat.
Ah okey. Is a good option. But first, If overheat I can do a box to flow all air of the low grill, to the radiator.

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