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Yes... that’s what Im talking about. I’m looking for a used wing to cut ports in it to channel the air flowing along the roof, down onto the rear window. You used to be able to get side winglets that did the same thing. I can’t figure why designers aren’t considering this as a problem to deal with but hey....I like to see what’s behind me.
It's a drag, as we used to say. Like pulling a small parachute. The flow isn't enough to prevent fine dust and dirt. I suspect there is electrostatic charge as well where dirt is attracted to the glass, but not sure of this.
 

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Love to see what you do here. We had similar to pictured above years go on multiple blazers and Suburbans. I debated building one off the Prinsu rack to try and help clear the dust but it's so far back there that it wouldn't look right and would interfere with the lift of the rear gate. Next idea was clearing holes through for wind flow. Unfortunately it's a double wall plastic so you'd need a way to sleeve the holes through both ends. I'm not good with welding or forming plastics so didn't go any further. Curious what you come up with. Living up in wheat fields lots of dust and the back of car gets horrendously filthy while rest of car is clean. Yes, it's a bit annoying. Curious what you come up with and how it works.

Best of luck,

Mike
 

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Discussion Starter #23
Yep, that wing is going to require building “ducting” but you see the problem. I kicked a note to Subaru and got the usual “turning it over to r&d.” Whatever. I’m still looking for a used wing at a reasonable price considering I’m cutting into it. Saw one that was really beat up..... The quest continues.
 

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This is really an unsolvable problem of wind flows on any vehicle which has a more or less vertical rear end. What happens is that the air moves around your car in sort of a teardrop shape. Rounded in the front as your car bulls through it. and tapering to a point behind as the air closes back up. But what this also does is create a semi-dead air space immediately behind the vehicle. It's not motionless in relation to the car, but it's kind of a turbulent area where the air, and anything suspended in the air, swirls around rather than a constant entering and leaving.

This is the reason that the back of cars and trucks get covered with dirt, water, soot, whatever. This is the reason that most SUVs, hatchbacks, and wagons are built with rear wipers. While sedans are not. This is also the reason that it is not legal in some places to drive a hatchback with the hatch open, as it can lead to high concentrations of exhaust gas in the interior (which means if circumstances ever require you to drive with the hatch open, such as carrying an oversized load, do so with the front windows open, so that the driver has clean air, and doesn't become incapacitated by the exhaust).

This is just the physics of how air moves. And nothing can be done about it, without making the rear of the car look like the rear of an airplane. So if you are driving in conditions where this is a major problem, carry something with you to clean the glass.
I solved the problem by repainting my XV the same color as road salt.
 

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Have you ever taped tufts of yarn to the roof/rear window of the Crosstrek to observe air flow at speed? Might be useful before you make plans on a wing that will hurt your mileage. Good luck!
 

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Discussion Starter #26
Actually I taped half a dozen incense sticks on the hood and used a big fan to blow the smoke along the profile. Lol, no I didn’t. I’m not worried about mileage because I’ve only hit the listed mpg once. Haven’t been near it since. As far as upsetting the streamlining, the drag created by the existing rear end wont change much with the change I’m looking at. I’m now beginning to look at checking it out first by simply removing the factory wing, then with the modified wing. Only in the beginning stages.
 

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I live on a gravel road. My desert khaki Crosstrek is the exact same color as the gravel dust! It always appears to be much cleaner from a distance than my dark blue truck or previous bright blue car. I always clean the entire rear window when I buy gas. If it's a build up of dry road dust, I just use the wiper dry. It knocks the dust right off, and I don't go through a lot of wiper fluid, and don't get ugly streaks down the back from the dripping fluid.
 

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Discussion Starter #28
Found a video on YouTube that kind of addresses the problem. The guy even said the wing placement helped keep the window cleaner. Take a look...

Has me thinking.......
 

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Discussion Starter #29
What is critical is the cut of the front of the wing which allows air to blast onto the rear window. Just raising the stock wing will have limited effect. I believe a larger gap with direction or ports will fix that dirt issue.
 
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