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Old 08-16-2011, 11:14 PM   #21 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
As for the headlights, I'd say they're significant. But to me, significant = 2%
I estimate it at about 13%.

If the lights are about 6" X 9" we have 108 square inches, or 0.75 square feet. 0.75 X 1.17 Cd (for a flat plate) = 0.8775 CdA.

Clean Ford Probe = 21 square feet X 0.31 Cd = 6.51 CdA.

0.8775/6.51 = 0.135 or 13.5%.

Or, to put it another way, it's like taking the 0.31 Cd of the clean car up to 0.352.
0.8775 + 6.51 = 7.3875. 7.3875/21 = 0.352 Cd.

42 Cd points is quite a bit.

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Old 08-16-2011, 11:32 PM   #22 (permalink)
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Better than VG's would be a rear spoiler, I'd say.

VG's energize the boundary layer and redirect airflow at the expense of the vortices that consume energy.

A rear spoiler that's high/long enough to promote flow re-attachment (assuming it's detached in the first place) would be a passive fix with no downside, assuming it's sized appropriately.

Easier said than done
Ok, that makes sense. I'll see what happens with the tufts, but a spoiler should be pretty easy to make and test. Right? haha

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Better a winking car than one with both eyes wide open, if that's an option.
I am pro "wink mod"



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Wow, that's terrible. The trouble is the $113 headlight motor will never pay for itself. I'll see if I can rig them to go down.

Is there any way to figure out the Cd improvement with my mirror delete, grille blocks and belly pan?
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Old 08-17-2011, 06:35 AM   #23 (permalink)
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Is there any way to figure out the Cd improvement with my mirror delete, grille blocks and belly pan?
A measured coast down tests (distance, time, speeds) can give you the Cd - or an approximation of it.
There's a thread on calculating Cd in the aerodynamics subforum IIRC

If you had done such a test with the stock car, you could have calculated the % improvement over stock.


The true goal is not the testing, however

You sure ain't waisting time to mod that Probe !


Radiused bumpers can help reduce drag if they're carefully designed.
But air flow over curved surfaces can also increase drag - the lift force of the Coanda effect working against you.
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Old 08-17-2011, 03:27 PM   #24 (permalink)
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Since we know the stock Probe is supposed to be 0.304 Cd it should give me a rough estimate what things are doing.

I can't do any mods today because I have to work, but I looked at the headlights. The mechanism doesn't appear conducive to manual operation, BUT there is a large open space in the bumper where they hide. This leads me to believe I could easily have someone fab up a few brackets to hold the headlights (fixed in the upright position) at least three inches lower in the body and make transparent fairings afterward. Going to look into this.

Also put some electrical tape over some bumper-body gaps and around the taillights.

Thinking of getting a vinyl made "WHAT WOULD JARAY DO?" Would anyone be interested in one?
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Old 08-17-2011, 03:34 PM   #25 (permalink)
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WWJarayD? Funny!

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Ok, that makes sense. I'll see what happens with the tufts, but a spoiler should be pretty easy to make and test. Right? haha
There actually are rules of thumb for adding a rear spoiler. I don't have them at my fingertips, but they're around here somewhere.

Car and Driver added one to their project Pinto back in the day, and it helped:

$11 worth of mods plus new tires – Car and Driver improves MPG by 25%
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Old 08-17-2011, 03:38 PM   #26 (permalink)
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I've seen that before- pretty funny! My dad's got some aluminum house trim lying around for the addition so I might be able to snag some for a spoiler.

Also, found a guy with some spare FC RX7 headlight motors (same units as in my Mazdord), so if they're cheap enough I'll just do that instead of the fixed headlight mod.

Edit: buying them for $25. Should be picking them up in early Sept.

Last edited by Sven7; 08-18-2011 at 03:31 AM..
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Old 08-19-2011, 09:34 AM   #27 (permalink)
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More work yesterday.

Had some longevity issues with the passenger fairing so I bolted part of it into the bumper and made new flares. After done I realized they resemble hachiroku TRD flares. Learn from the best, right?



Wheel covers too. I made a compass and marked out 15" circles for my 14" wheels. They fit very nicely inset in the rim so they don't catch air. Zip tied to the spokes in four locations with a hole for the valve stem. Very happy with them so far.

Last, some better grille blocks. Finally blocked the middle grille and decided to make that and the top one a little more flush. Top one is with aluminum siding cut to size and bottom is still coroplast.

I've got some headlight motors lined up but can't get them for a couple weeks.

I went 40 miles before the gas gauge fell below the "full" mark. I think I'm doing pretty well? Looking to do a tuft test tomorrow.













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Old 08-19-2011, 01:53 PM   #28 (permalink)
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Just did some preliminary tuft testing by myself. The rear window flow IS attached. The flow around the A pillar IS attached. It appears the flow over the little fairing I put on the antenna mount IS attached.

What is decidedly NOT attached is the flow behind the headlights, obviously. I didn't imagine it would be so turbulent so far back, though. It's unattached over half the length of the hood, and I didn't put tufts back far enough to see where it reattaches.

More extensive test to come when I can find a camera car to film me.
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Old 08-19-2011, 02:53 PM   #29 (permalink)
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Something about the angle, lighting & mods screams "80's concept car!" in this pic. (More so if the lights were down.) That's not a bad thing.

Any plans to lower the ride height?
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Old 08-19-2011, 03:35 PM   #30 (permalink)
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1985 Probe V Concept:



Ford/Ghia concept "Via":


Moray Callum is new Ford Executive Director of Design - Car Body Design

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