I often wondered if the OEM rear spoiler is just for looks or actually helps with the aerodynamics of the xB? From what I have read in other posts it doesn't even help the rear window stay clean.

I realize the xB is very boxy and the drag coefficient (which I could not find on the net) is questionable, however if you compare it to similar shaped vehicles such as the Chevy Astro Van, the Coefficient of Drag (Cd) is 0.40 which is not too bad.

Average Drag Coefficients:
Sports Car 0.2 - 0.3
Typical Car 0.5
Station Wagon 0.6
Truck 0.8 - 1.0
Motorcyclist 1.8

I want to buy, build or design a rear spoiler that will actually help the xB's aerodynamics, keep the rear window cleaner and help the gas millage a little bit.

Any tips & advice would be appreciated.



Cd - Source:
http://www.f1-country.com/f1-enginee...odynamics.html

 

it would have to be like 12" long lol

 

The addition of any properly working rear spoiler will increase the negative pressure behind the xB. Thus, the rear window will continue to be dirty.

I bought my xB w/o any rear spoiler. I drive to the car wash and back, and the rear window remains relative clean. I add the Fabulous spoiler, and in the less than one mile drive home, the back window has a thin layer of road dirt already.

Think of a race car going thru the rain. You can see the mist that is kicked up in the rear fo the car. That's what happens when you made a car more aerodynamic. The air flows better over the car creating the suction/grip to keep it down on the pavement.

 

Well put

 

Except that I have no rear spoiler and I have to wipe down
the back of the box every friggen day!

Any flat rear end is going to have that negitive pressure!

I REALLY want a spoiler, but my options seem to be OEM
*or* Fab style. I WANT SOMETHING DIFFERENT!!!

I'd love something between Fab and OEM in size, simple
and clean lines. Anyone listening!!

 

I have the exact same problem (thus my reason for creating this post)
But... what about someting like a rear window deflector?

Example:
http://www.truckstuffusa.com/egrdustguard.html

Anything like this for another car that might fit the xB?

 

i would say find cars with similar rear ends and measure them and get it as close as possible to what the box is. than you have to figure out how to mount it.

 

The reason the back gets dirty is the air flowing UNDER the car stirs up the dust and the airflow brings it up into the dead zone in the rear. People were theorizing that the slit in the OEM spoiler would help direct air down the window which is exactly opposite. The flow of air over the top will draw air UP thru the slit, bringing up the road grime and dust. A deflector type device would probably be more effective at dirt, but now you are introducing drag.

 

Mark is correct.

While the deflector is great for increasing the flow over the rear window, you are increasing drag, however slight.

 

Hmmmm.... so the choices are increased drag (bad) and a cleaner rear window, or a dirty rear window but less drag.
I think I'll go with the less drag idea but I don't want to put a 12" whale tail on the back of the box.

Any suggestions on a good after market rear spoiler?