sc1 aero mods

[arcosine]

I decided to move the spoiler back 6 inches, so I can get the key into the trunk. I'll fill the space with transparent PET sheet that I have left over from my HPV canopy..

Have you ever compared the CD of aircraft and cars? An outstanding car wound have a CD of .2, yet a run of the mill Cessna has CD of .06. The Cessna can fly at 150 mph while getting 18 mpg.

Do you see any big holes for the wheels?:

[aerohead]

Originally Posted by arcosine

I decided to move the spoiler back 6 inches, so I can get the key into the trunk. I'll fill the space with transparent PET sheet that I have left over from my HPV canopy..

Have you ever compared the CD of aircraft and cars? An outstanding car wound have a CD of .2, yet a run of the mill Cessna has CD of .06. The Cessna can fly at 150 mph while getting 18 mpg.

Do you see any big holes for the wheels?:

It's not fruitful to compare aircraft and automobiles.
Aircraft drag is governed by skin friction.
Automobile drag is governed by longitudinal pressure differentials.
Although I don't have the reference in front of me,I believe Volkswagen's ARVW of 1982 gets similar mpg at similar velocity as the Cessna.

[2000mc]

Originally Posted by Cd

My guess is that you will get better gas mileage if you leave the spoiler at its factory installed position.
It grabs a bit of the air that is detached and gives it a clean break.

i thought that too, but with the mileage hes getting i thought i'd look into it. my initial tests were a small improvement with the spoiler off, upon more extensive testing it was a total wash for me.
looking at the car from the side, it totally looks like the spoiler should help, looking in person, i think the outer 8-12" of the spoiler on either side are hurting, because there wouldn't be detached flow to fix, the sections extending past the deck lid to the sides have no chance of helping, its just out there stirring up air. i think theres probably a solid 1' wide area in the middle of the deck lid where it would be working exactly like you would want it to. this all adds up to a net gain of: me wasting gas testing with no helpful result

i was thinking setting it straight and level behind the car might work, but might actually get better results and be more adjustable with just a sheet of coroplast

[aerohead]

Originally Posted by aerohead

It's not fruitful to compare aircraft and automobiles.
Aircraft drag is governed by skin friction.
Automobile drag is governed by longitudinal pressure differentials.
Although I don't have the reference in front of me,I believe Volkswagen's ARVW of 1982 gets similar mpg at similar velocity as the Cessna.

My apology to VW.Their 1982 Aerodynamic Research Volkswagen (ARVW) got :
*17 mpg at 225 mph
*39 mpg at 155 mph

[arcosine]

With 4 people aboard? We can find a special plane that gets better than that, not just an old Cessna 172 rg. Whats the point? 45 mpg at 207 mph.

http://www.treehugger.com/aviation/h...most-cars.html

http://www.msnbc.msn.com/id/47433969...nomy-your-car/

Originally Posted by aerohead

My apology to VW.Their 1982 Aerodynamic Research Volkswagen (ARVW) got :
*17 mpg at 225 mph
*39 mpg at 155 mph

[aerohead]

Originally Posted by arcosine

With 4 people aboard? We can find a special plane that gets better than that, not just an old Cessna 172 rg. Whats the point? 45 mpg at 207 mph.

Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG (That's Better Than Most Cars!) : TreeHugger

A plane with better fuel economy than your car - Technology & science - Innovation - NBCNews.com

*We're streamlining a Saturn,yes?
*Abbott and von Doenhoff tell us not to attempt to use any flight value of any aircraft structure at any place other than under flight conditions.
*Jaray,Prandtl,and Rumpler all were aware that drag coefficients of free-flying forms doubles when in ground proximity.
*Aircraft design presumes fully attached flow.
*Aircraft drag is dominated by skin friction.
*Automobile design is challenged with respect to attached flow.
*Automobile drag is dominated by pressure drag which is a function of flow separation.
*Hucho warns us about attempting to translate the flow efficiencies of 2-dimensional free-flow structures to the 3-dimensional flow of bluff body structures in ground proximity,especially the wake,which cannot be easily modeled as with aircraft.

[arcosine]

No, I am modding the sc1, Aerohead, you are theorizing about it. I still want to put some kind of tail on it, improve the flow through the engine radiator and move the front bottom lip up to round off the air dam. Remove the trailer hitch. What tail would theoretically better, maintaining the rear glass slope through the trunk, and having tail fins for the lights and fenders or starting the tail at the trunk edge? the rear glass slope is 17 degrees. Of course cutting the square fenders an bumper off and tapering the whole rear end would be best, but I am not ready to do this.







I am thinking of some engine mods, cam timing, which I will elaborate on in a different post.

http://ecomodder.com/forum/showthrea...ing-22959.html

[aerohead]

Originally Posted by arcosine

No, I am modding the sc1, Aerohead, you are theorizing about it. I still want to put some kind of tail on it, improve the flow through the engine radiator and move the front bottom lip up to round off the air dam. Remove the trailer hitch. What tail would theoretically better, maintaining the rear glass slope through the trunk, and having tail fins for the lights and fenders or starting the tail at the trunk edge? the rear glass slope is 17 degrees. Of course cutting the square fenders an bumper off and tapering the whole rear end would be best, but I am not ready to do this.







I am thinking of some engine mods, cam timing, which I will elaborate on in a different post.

http://ecomodder.com/forum/showthrea...ing-22959.html

Tony,I'd like you to do a search for:
*photo albums
*then click on Phil Knox aerodynamic photos album
*go down to 'other vehicles 1',p.1,line-2,1st image(this is a rear view of the boat tail on my CRX.
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*then go to 'other vehicles 2',p.1,line-3,3rd image.(this is a side elevation of the boat tail).
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If you were to project out from the Saturn's roof along the 'Template',extending the C-pillars into aerodynamic buttresses,while extending the trunklid elevation back,and curving the sides in gently,you'd 'box in' an attached vortex which would occupy this void.
The active flow would bounce off this vortex and would be forced to follow a path as if you had a perfect K-form roofline.
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My CRX as shown,has Cd 0.235,is 7 mph faster,and gets low 60s mpg on a calm day at the old double-nickel speed limit.It drops to 52 mpg at 70 mph.This is with only 12-inches of boat tail.
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Your Saturn is 'cleaner' than my CRX ever hoped to be,so she's gonna do even better.It's just a matter of length.I'd stick to the 'Template.' The curvature you use in elevation you can match in plan view.You'll just have to locate the point on the body sides where she's at her max. width.You'll have to do the best with what you have based upon what Saturn got started.
If you can live with a little length there's no reason why you can't go below Cd 0.20.
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NOTE: The buttresses will create a blind spot as with Insight and Prius and you'll just have to pay more attention to your mirrors.A price we pay for working with production cars.

[arcosine]

I sold my 91 CRX HF because it was a California model, 3.25 final drive, and also when I went to bleed the brakes, the fitting broke due to rust. The Saturn is a bigger car, more frontal area. I'll take a peek at the photos.

I cut 6.5 inches off the rear wing, riveted it back together and need to make some brackets to mount it behind the deck.


Looks good... 1991 was a long time ago, I worked for l Douglas Aircraft Company (Mc Donnell Douglas). I had a 1977 honda accord with a 1981 1355cc civic cvcc engine milled to 10.25:1 compression ratio, advanced ignition timing, jetted lean and a taller fifth gear. I got 50 mpg consistently without hypermilling. It would have done better with some aeromods! It finally burnt a piston.

Lets see... If I assume that your CRX top speed was 100 mph and had a 7 mph increase with the tail, then the reduction in drag would be 1-(100/107)^3 =22%, pretty good.

[arcosine]

I am posting kilt pics of the wheels turned right to maxim stop, as requested by Cd. The tires are 10% bigger diameter than stock, 175/70R14 to 205/70R15.

By the way I just go my best mileage at 48.75 mpg.

Left side trailing edge full right:



Left side leading edge full right:



Right side trailing edge full right:



Right side leading edge full right: