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Old 07-18-2017, 10:10 PM   #1 (permalink)
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Windshield on or off for aerodynamics?

I would not, but I heard that you can reduce frontal area and therefore your Cd by removing the windshield and back window so the air can easily flow through the car instead of getting shoved off to the side by the windshield. Does that make sense to you? It does not to me. Thanks

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Old 07-18-2017, 10:14 PM   #2 (permalink)
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Makes sense to me. When my windscreen fell off my 1976 CB750, I had a higher top speed.

Not sure it's legal on a car though.
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Old 07-19-2017, 02:02 AM   #3 (permalink)
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That's why the old sports cars had aero screens. The resistance to air flow by a driver's head must be less than a windscreen. Not very comfortable though. Especially in inclement weather.
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Old 07-19-2017, 02:13 AM   #4 (permalink)
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In Oregon wipers required glass to wipe optional.
For it to work some ducting would be needed or the interior voids would destroy any posability of smooth flow. At the dirt track closing off the interior was reserved for the uper street class , as a performance advantage .Problem the front hole is normally biger than the rear hole + driver blockage. Desine it as a converging diverging duct system.
Most cars would see better results from a trip to the guillotine to remove everything from the window sill up(windshield less convertible).
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Old 07-19-2017, 02:49 AM   #5 (permalink)
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When you think about it, the aero screen and tonneau cover of the 20's and 30's was spot on. Here is a more recent rendition.
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Old 07-19-2017, 05:35 PM   #6 (permalink)
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When I saw the thread title, I thought this was going to be about Jeeps with the fold-able windshields.

I wonder if anybody who owns one cares enough about MPG to have tested the difference.
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Old 07-19-2017, 06:11 PM   #7 (permalink)
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When my buddy rolled his F150 and broke the front and rear glass out, I should have had him track his MPG on the drive home.

Instead all we got was a photo of his windblown hair with shards of glass in his beard. I wonder where that photo went...
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Old 07-19-2017, 10:59 PM   #8 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
When I saw the thread title, I thought this was going to be about Jeeps with the fold-able windshields.

I wonder if anybody who owns one cares enough about MPG to have tested the difference.
Well, I have all I need to do it

But Jeeps aren't typical. For example opening a door at speed, it just stays open at a 20-30* angle, no buffeting, just pretty much rock solid in that position.
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Old 07-20-2017, 03:41 AM   #9 (permalink)
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Quote:
you can reduce frontal area and therefore your Cd
They are two different things. It would be similar to taking the fenders off and running open wheel. Especially if the side windows are down, then the pillars approximate round tubes — more drag.

Tonneau covers and teardrop headrests are traditional. My example would be Bombshell Betty, windshield but no side windows or back window.


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When I saw it it didn't have that weird spoiler under the not-window, but it did have a fence in the diffuser.

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Old 07-20-2017, 06:56 AM   #10 (permalink)
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It very much depends on the car.
Removing the windscreen of a Prius style car would be very bad, as it is part of the whole aero design. I doubt the Kammback does any good without the windows.

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