Air Flow Seperation Question... (where to mount roof VG's on Nissan Cube)

[AeroModder]

He's using delta shaped VGs, not airtabs.


I used the Vortekz brand VGs for some time, and found they do a better job of reducing lift than drag. They alter the pressure of the air above the rear, which reduces lift, but the forceful moving of that air creates drag. If anything, on a three box sedan, you can reduce drag by a few points, and almost eliminate rear end lift. Mitsubishi did an in-house study of VGs on the Lancer Evo: http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

I'm not sure what effect they would have on a rolling shoebox, though.

[ChopsQube]

Originally Posted by ChazInMT

Chops....You're under the common misconception that there is something you can do about the "Vacuum" behind your cube shaped mode of transport. Well, All vehicles have to deal with this, and it has to do with the overall cross section your car presents. The difference between an aero shape, and one which isn't, has to do largely with how this air is managed after it makes it past the "Fattest" part of the car. More aero shapes tend to come together gradually after this fat part thus allowing the air to make a gradual transition to what it was doing before you violated it by ramming through it at high speed.

So bottom line, your Cube creation does very little to ease this transition. Any thing the air tabs may do to "Break the Vacuum" will be more than off set by the drag created in producing the effect.

Air tabs may have some effect on Very specific automobile shapes, these shapes would be ones which the flow separation occurs due to the rear slope of the vehicle being just a bit too much for the flow to remain attached. These vehicles are not common, and your Cube is clearly far outside this group.

You have a wicked cool car though which is maximized for interior space for the size that it is. Enjoy it just the same.

I forgot about this thread for a little while!

I've been doing research on "Cube" sites for suspension lowering and such. Also seeing if I can get my hands on some genuine Japanese parts for it like the side mirrors for instance. They are small and sleek on the Japan/UK versions which is tons better than the elephant ears on the US versions.

Anyway, I wouldn't say that I was misconceived about the VG's and what they can or can't do for the Cube. I know there's no way I can eliminate the drag at the back, but if they help in the slightest bit if at all, I'm fine with that.

I can however reduce the drag. In doing so I plan on lowering the Cube 2 inches (the kit drops the front 2", the rear 1.75"), extend the air dam an inch or two which will incorporate spats/deflectors for the front wheels, put spats in the back for the rear wheels, and do some sort of grill block.

The thing is, I already had the VG's and I couldn't see the point of wasting money on returning them, so I just said the heck with it and installed them today. The way the ridges line up on the roof, I had no choice but to only use 8 of the 10 supplied VG's. You'll see what I'm talking about when you see the pics below. I also plan on purchasing one of those "Shark Fin Antenna's" to replace the stock one, and I'll most likely be getting rid of the Sirius/XM Radio altogether as they have a very small music selection that is constantly repeated and sounds like crap. Half the time, it has the sound quality of an AM tuner! I just stream Soma.FM off my iPhone via Bluetooth on my stereo.

I'll take better pics with my SLR later today.

[ChopsQube]

Here's some better pics...

[MetroMPG]

Well, at least they look neat! (And props on the photography - you're good!)

But...

How are your fabrication skills? You'd be further ahead making a sloping/tapered roof line extension (which people will mistakenly call a "spoiler") to mount on the upper part of the tailgate.

Lowering will also probably help, as will the air dam.

[ChopsQube]

Originally Posted by MetroMPG

Well, at least they look neat! (And props on the photography - you're good!)

But...

How are your fabrication skills? You'd be further ahead making a sloping/tapered roof line extension (which people will mistakenly call a "spoiler") to mount on the upper part of the tailgate.

Lowering will also probably help, as will the air dam.

Why thank you!

I've never done any "real" fabrication, so I'm sure I'm horrible at it, and if I were to do something like that, it would have to be made out of ABS or fiberglass or something that looks like it came with the car or was offered as an option.

I admire and respect what a lot of you guys are doing with your vehicles, but I draw the line at using rolls of duct tape, cardboard and coroplast (sp?) all over my car. If I ever get around to doing a partial or full belly pan, it'll be done with sheets of aluminum so it looks good and lasts. I'll also eventually get the Krom edition rear bumper cover as it has two fake vents in it that I would like to open up and cover with a black ABS mesh with the idea of trying to vent the trapped air inside the bumper cover, reducing drag. You know, stuff like that so they don't look out of place or draw attention to themselves. Things that look like they came from the factory that way.

[hendan]

Yeah. Useful as well as beautiful. That is my philosophy.

[miket]

i wouldn't worry so much that you'd make a cube an ugly car...

[ChopsQube]

Originally Posted by hendan

Yeah. Useful as well as beautiful. That is my philosophy.

Same here.

Originally Posted by miket

i wouldn't worry so much that you'd make a cube an ugly car...

Umm... Ah, never mind. It's not worth the aggravation. You should resort back to more reading and less typing.

[fjasper]

FWIW, I put a couple of VGs on the roof of my Audi 80 sedan, and they did a nice job keeping the air attached to the back window. The water drops sitting there were bugging me, but with the VGs, the airflow would clear them off. They were about a foot ahead of the roof/window junction to give the vortex some room to form and attach to the surface. I did at least find duct tape that matched the color of my car, though (white).

I also noticed that the overall airflow across the rear window and rear quarter panels seemed to converge more toward the centerline of the car. unfortunately I drive too erratically to notice whether the economy was better.

I eventually took them off because they were on with duct tape and I didn't want it to get too crusty. And I was tired of explaining them to people. My wife dubbed my car "Sharkey" when she saw them, and I'm afraid the name is going to stick.

[MetroMPG]

fjasper: I also tested AirTab type VG's on the roof of an 06 Corolla sedan. Documented improved flow over the rear window & deck lid, but no MPG gain was detectable in testing at 55 mph.

http://ecomodder.com/forum/showthrea...olla-2390.html