wagon Kammback?
 

I have a wagon as seen below
https://216.77.188.54/coDataImages/p/...37PICT2510.JPG

I am thinking about a few ideas to clean up the air as it leaves the back of the car.

1. https://www.vividracing.com/catalog/w...bonwrxroof.jpg

or
2. a partial boat tail.

personally I like the idea of a wing that directs the flow in a more beneficial direction.

The roof rack has to stay since the air bags are mounted directly below it and I'm a chicken.

philip1 -

I've been wanting to do something for over a year. Here is a mock-up of what I am thinking of doing :

Attachment 1194

But, I have another test in progress right now, so I think it is a month away.

CarloSW2

philip 1,
When (if) you get a scangauge or other onboard mpg readout, leave it off while running the Autocross course. It depressed me to see that my runs (HS) consumes fuel at about three times the rate of typical daily driving.
What have you done to go into the STS class?

I've actually retired the wagon from racing it's now just a driver. a scangauge is on my wants list.

I find it hard to believe the roof racks are integral to any airbag system.
I can only assume you are talking about airbags mounted at the roof/headliner? Maybe they share a bolt with the external racks...but as long as you maintain a solid mount of the airbag...lose the racks;)

the bolts for the rack are above the airbags and I'm scared to mess with them because of that.

philip1 -

I understand your trepidation, but I am also curious. Maybe this is a question for www.saturnfans.com. I am sure that one of the online Saturn repair techs could give you a professional answer on this. I am thinking there must be a set of steps where you disconnect the battery, remove the racks in step a, b, c, d, and reconnect the battery. If you are not a member, I can ask the question for you.

Can an airbag deploy without being connected to the battery? The manuals always say that you should disconnect the battery to prevent the airbag from being deployed.

CarloSW2

I'm on saturnfans.com same name and everything. I have mentioned this there. So far no one has said go for it.

philip1 -

Ok, I was being lazy and didn't search saturnfans. If they didn't give you the go, then I wouldn't do it either.

CarloSW2

after pondering this for a few days I have decided to try on my next 2 month cycle some delta VG's just ahead of the hatch gap and we will see if they make a difference.

Does your roof rack have a center piece that extends the width of the car ?

As long as there is no ceter piece to trip the airflow, I wouldn't think the roof racks would hurt the aero all that much.
I would think the main factor that would hurt the aero in your case ( if indeed tha racks did not have the center braces ) would be the added frontal area.
Then again, you might want to fill in the gaps between those posts to reduce turbulence.

I would think that you could fill in those gaps in the roof racks and actually have them act as an aerodynamic aid, such as the roof vanes that you see on NASCAR and Bonneville racers.
As far as the spoiler idea, I wonder what effect that adding an extention mounted on the roof racks would have. It could catch the air and deflect it downwards, thereby reducing the size of your wake.
https://farm4.static.flickr.com/3124/...554845d9_o.jpg

Then again, it may not do crap for the aero and just make you look like a knuckehead.
You never know.

Actually, considering the boudary layer airflow and all, this might actually work . Not only would it deflect the airflow downwards, but it would add more velocity to the airstream since it is essentially a sort of scoop that you have added to the top of the car.
The dowside is that that it would add frontal area.

I've got a roof rack with the cross bars and that notion has crossed my mind. The cross bars are certainly unimpressive looking aerodynamically, but short of removing them completely, this seems like a compromise worth trying. I think the change in frontal area would be more than compensated for in wake reduction.

I agree, why not embrace the roofracks and use them as part of a functional and stylish solution. Something like a SPORTKAMM would do the trick....

https://img520.imageshack.us/img520/4...mmsmallcb9.jpg
;)

all great ideas and Charles WOW!! that I can take to the body man and get somewhere!

I like that.

I'll probably have something along those lines done.

I was thinking of combining both ideas like so
https://www.fuelly.com/attachments/fo...f5580ff491.jpg

That's what I had in mind too.
I like Charles Bs' idea of pinching the wake inward with the roof rack extentions.
I wonder if adding a 'wing' like I illustrated above the roof extention ( lower spoiler ) would create a higher pressure to the airflow - again pinching the wake and forcing the wake to stay attached to the teardrop shape farther from the back of the car.

It would sort of a 'biplane wing' set up.


It would be easy to test - just strap a sheet of something to the top of the roof rack.

Did you draw this ? ( Nice ! )

I'm still trying to figure out why I saw my best tank on my Escort wagon with two bikes strapped to the back...

I figure the Audi A2 gives us some good clues about how to proceed though...
https://en.wikipedia.org/wiki/Image:Audi_A2_L_Silber.jpg
Very low Cd.

I figure you can either use either a rear window air deflector type spoiler to bring air down the back, or use a surface extension to entrain flow. I've also been considering the possibility of a deflector extending back abover the windshield by 3 inches.... yes it gains CSA, but by making the forebody "fatter" at the top, it might cause the air to take a path at an angle further back, meaning that it attaches to the rear surface longer, and reduces base drag. Anyone with a wagon with a tilt up sunroof, might like to experiment as to whether overall aerodynamics seem improved with it up or closed.

On my '88 Voyager, with rather square tailgate edges, I am planning to try attaching quarter rounds cut from pool noodles around the hatch, hoping the curved surface will entrain more air behind the vehicle.

Recently saw a Chevrolet Aveo that had a negative incidence rear spoiler/deflector, that looked promising. Not sure what I'm doing for the back of the Escort when it's back together again, think it might just need a deflector to keep the air nailed down further back. May try tumble strips/turbulators around the back.

Be interesting to carve humps out of styrofoam and stick them on top see if they make a difference.

Last summer I did some very informal testing with my Passat wagon with the sunroof open and closed. It is not a flip up design as you are talking about here but has a small piece at the front that snaps up to deflect air up slightly. I thought I was crazy but I consistantly was getting slightly better mileage with the sunroof open. Perhaps your theory explains it. When the weather gets nicer I will try a more serious A-B-A test!

Phil


Roadwarrior said:

"I figure you can either use either a rear window air deflector type spoiler to bring air down the back, or use a surface extension to entrain flow. I've also been considering the possibility of a deflector extending back abover the windshield by 3 inches.... yes it gains CSA, but by making the forebody "fatter" at the top, it might cause the air to take a path at an angle further back, meaning that it attaches to the rear surface longer, and reduces base drag. Anyone with a wagon with a tilt up sunroof, might like to experiment as to whether overall aerodynamics seem improved with it up or closed. "

Patience is a virtue I don't seem to have....... So when my VG's arrived today, I went right out and installed them......So much for the two month average oh well. we'll see if it all helps then.

last week I took a trip out of town this photo is upon returning.
https://www.fuelly.com/attachments/fo...6decae3a9e.jpg

I see you used your windshield washers a lot on the trip. :)

LOL that is after not using them for the whole winter I needed them and the resivoir was almost empty. DARN BUGS!!!!