TennesseeZ4

So we wagon folks know how the rear window gets dirty / covered in virtually any type of dust, rain, snow, etc., and requires the use of the rear wiper. I have been doing some research on the possibility of 'moving' the low pressure area / drag area, away from the rear window. Here is a link to an aero expert who compares different body types, and the associated drag on the vehicles, if you like that kind of thing this is pretty good stuff:
I have also sent a request to one of our site sponsors, JB Speed, to see if they have some aero for the wagon. I have laid out an experiment which I shall try when the weather allows, using wool tufts and tape to see how a Gurney flap at the edge of the rear window spoiler affects the airflow over the window. It makes sense to me that if you can affect / disturb the air flow at the end of the roof line, it would create a pressure area nearer the car to keep the dust and dirt away from the window. While there may be some change in fuel consumption, I have to believe it would be minimal.

Looking at the internet of things, I see nothing specific to that application, however there are a number of Gurney flaps that are available for many models of cars, as well as a couple of generic versions. Another variation would be installation of vortex generators at the edge of the spoiler, which some manufacturers use for side window airflow.

All this leads me to the question: has anyone else done something like this? Or discovered a solution to the dirty air behind the car? There has to be a way to alter the airflow at the rear of the car and assist in keeping that back window cleaner, along with the entire rear end of the car. Thanks.

TennesseeZ4

Found a couple of examples from Europe: expensive, however this may be the answer. PIECHA RS-R Roof Edge Spoiler

https://global.cksperformance.com/pr...-roof-spoilers

murman

I don't have a practical solution, unfortunately only a non-practical one: get an S211 instead of an S213. My S211 got nowhere as filthy a backside (sorry but that sounds just awful) as my S213 does.

bishop64

This is a long time well known problem for estate/station wagon and even for some SUVs. I bet all car manufacturers must have researched for a solution. Frankly, if there is one, it should have been found already. So, it is really near impossible to solve it, at least not in an economic way. These spoilers/deflectors do not seem to work well. Some might work better than the others but at the expense of the aerodynamics. I think, one has to sacrifice the fuel efficiency at lot in order to achieve a noticeably less dirty rear. And, the sacrifice is too much for a car manufacturer to adapt it.
If you do find one, you might possibly patent it and become very rich.

DFWdude

Wagon aerodynamics? They're called "shooting BRAKE" for a reason...

e55phil

I watched this video. The guy reminds me of my college physics professor. It's the reason I majored in philosophy.

Did I miss something or is the bottom line that my back windows always going to get dirty and there's is not anything I can do about it.