Scion xA aero mods

[alohaspirit]

i like the new grill block

it has a definite curve to it

almost looks like

[NeilBlanchard]

Hi,

I've put some small "tabs" on the back, that hopefully act like a Kamm back:




The results so far are that these help somewhat, but are not Earth shattering. I hope to extend them down below the lights (and maybe use acrylic over the lights) and across the bottom, too.

[whokilledthejams]

Nice! I thought about doing something similar with the xB, but I'm low on Coroplast at the moment.

[NeilBlanchard]

Thanks! I need to get some more, too. I'd like to do some more smoothing on the underside -- though for part of it, I need to get aluminum.

BTW, I have a small addition and change to the rear under pan, to make it shallower and prevent air from getting in above it. I'll take some pictures next time I have it up on the ramps. (I bought a pair, along with two wood beaded seat covers at my local auto parts store!)

In starting to read the Hucho book, I'm wondering if removing the plastic rocker panel thingies on my car would be a small help? I would imagine that the air is coming out from under the car, and a smoother radius might be a bit better?

[NeilBlanchard]

Hi,

Question: has anybody heard of or tried making an insert for a side window that has a NACA intake on it? If you roll down the window and then hold the insert in place adn then roll the window back up to hold it in place, theis would get ventilation air into the car -- hopefully with less drag (and noise) than just opening the window?

[NeilBlanchard]

Hi,

I'm going to head out soon and do some Cd coast down tests! I'll be recording video on my Fuji point and shoot, so the data gathering will be fairly painless -- I've got it attached to a mini tripod, which I will then tape to my steering wheel, so that it videos the ScanGauge II. I've set it to kilometers...

Questions: I've downloaded the spreadsheet from the Instructables page

How do I get reasonably accurate air density? (I'll check the elevation of my test site in Google Earth!)

How do I get the best guesstimate for tire rolling resistance?

[NeilBlanchard]

Hi again,

Originally Posted by NeilBlanchard

Hello,

I've determined that the approximate frontal area of the Scion xA is ~18.01 square feet. [See adjusted number below] I inserted this photo into DataCAD 12, scaled it based on the measuring tape just below the bumper, and I then carefully traced the outline of the car with a polyline, and the hatched it with a 1'-0" square grid.

Now, there is some distortion due to the camera being at a point (this is not a true "elevation" view). To minimize this, I used the zoom lens on it's longest focal length, and tried to position the height of the lens to ~1/2 the height of the car. The height scales to ~4'-2 1/2" whereas the specification is 60.2" (~5'-0 1/4"), and the width scales to 5'-1 7/8" vs 66.7" in the spec. so the actual area is like a little greater. In fact, the width is ~19% low and the height is ~7.75% too low, so that averages to 13.375%, so:

18.01 + 13.375% = 20.42 sq ft

[Edit: I will take another photo with a longer lens to try to reduce the error, and post the results later.]

I'm going to use a program called DXO Optics Pro to get perspective and distortion correction for the lens on my Nikon DX-40X, so I should be able to get a pretty accurate frontal area!

[NeilBlanchard]

Hi,

I did the coast down tests today, but the spreadsheet is just shootin' in the dark without a valid rolling resistance. If I use 0.011 (at the lower end of a "normal" tire on a smooth road), then I get a Cd of 0.267, which would be pretty sweet -- but I'm guessing at the RR...

I still need to measure the area from a corrected photo -- I used the number from the CdA list: ~22 sq ft for now.

[aerohead]

Originally Posted by NeilBlanchard

Hi,

Question: has anybody heard of or tried making an insert for a side window that has a NACA intake on it? If you roll down the window and then hold the insert in place adn then roll the window back up to hold it in place, theis would get ventilation air into the car -- hopefully with less drag (and noise) than just opening the window?

Neil,Charles Farmer,one of the local nut-cases who runs a streamliner at Bonneville, sells a plex or Lexan clear NACA duct which rivets to clear sheet,as you'll see on NASCAR.They may be available through a race catalog.If you can't find 'em,let me know and I'll hook you up.Tuft-test your side glass and look for vorticity.You'll want to stay way from those areas,as they'll be low pressure.If you incorporate horizontal louvers,you can keep the UV off your skin,wear short sleeves and reduce solar gain into the cabin.It's a great project idea and something I've wanted to do for years.

[NeilBlanchard]

Hi Phil,

The additional thing that this could accomplish is to get the side windows (close to) flush. I'll try some tuft tests when I can -- I'm guessing the rear windows would be better than the front, if the air flow has reattached after the (probable) separation just behind the A pillars?

The fronts might be helped by some flush "rain guards", I'll bet -- this will draw air out of the car, and mybe with less noise than when you just crack the windows?