air dam and vortec generators

[civic_matic_00]

Originally Posted by SL8Brick

Keep us posted....I'd be most interested in your results.

BTW, is your Civic a sedan? Its difficult to tell from your garage photos.

yup, the civic is a sedan, LX.

[civic_matic_00]

Originally Posted by COMP

i like the plastic spoons

LOL! I thought about just using the spoons but the wife would probably disown the civic if I do!

[SL8Brick]

Originally Posted by Hateful

I made these from wood. I think the shallow holes will provide a little extra turbulence.

Man, those things are HUGE.

[COMP]

Originally Posted by SL8Brick

Man, those things are HUGE.

i agree,,they need to be that tall ???

[Hateful]

Yes, they are bigger than what I've seen in pictures and links here; other than those air-tab things. I've only driven with all of them on today. I had two pieces of the flagging tape on the back glass and drove up to 48mph. The tape did not move any at all, until I reach 45mph. Then the drivers side tape would flutter a little,but still stayed straight ( no twisting to the right or left nor leaving the surface of the glass. It seems to pick up speed more coasting down hill. I live on a gravel road; the dust behind my car coming home did not rise above the height of my car. I've watched other cars at the same speed and the dust would go 15 to 20 feet high.
It seems to be working. If they are too big, I don't know. Look Funny? I'm sure they do,but that line has long since been crossed.

[SL8Brick]

Hateful, Here's an excerpt from the Mitsu PDF relating to VG size that's relevant here:

In connection with the size, the thickness of the boundary layer is measured based on the assumption that the optimum height of the VG would be nearly equal to the boundary layer thickness. Fig. 4 shows the velocity profile on the sedan’s roof. From this figure, the boundary layer thickness at the roof end immediately in front of the separation point is about 30 mm. Consequently, the optimum height for the VG is estimated to be up to approximately 30 mm.

Your delta fins might be creating vortices, but they're also extending beyond the boundary layer and most likely creating unwanted drag.

[Hateful]

Originally Posted by SL8Brick

Hateful, Here's an excerpt from the Mitsu PDF relating to VG size that's relevant here:



Your delta fins might be creating vortices, but they're also extending beyond the boundary layer and most likely creating unwanted drag.

I considered drag. There are grooves and indentions that I carved ( with a dremel tool) into them,tapering the back to avoid drag.

[SL8Brick]

OK, although I'd prefer a smooth surface, there's nothing wrong with the grooves. And tapering the fins into a convex shape is good. It's the overall height of each fin that we're questioning.

Maybe the angle of your photo is deceiving...exactly how tall is the trailing edge of each delta fin? Just curious.

[Hateful]

from the far end back they are 2 1/4 , 2 3/4 , 3 , 3 and the next three at 2 1/2 inches.

[SL8Brick]

Alright, I'd like to propose a possible scenario on what you've done. At their current height, your VGs are probably inducing effective vortices at lower speeds(guessing up to 45mph). But at higher speeds when the boundary layer is fully formed, they're creating vortices and a measurable amount of drag. At some point(highway speed) their height will become a disadvantage since the drag they create will nullify the drag alleviated behind the vehicle.

Its just a guess...does this make any sense?