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Old 12-24-2012, 01:30 PM   #1 (permalink)
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2000 Toyota Celica (7th Gen) - Stock Spoiler

Car: 2000 Toyota Celica (7th Gen)
Stock CD: 0.32

I was wondering if the stock spoiler that Toyota attached has a positive or negative effect on the aerodynamics. At first glance of the template, it looks like the spoiler raises the rear to the appropriate height. Upon closer examination of the spoiler, there is even a small lip built in allowing for clean separation from the rear edge (not pictured). What do you all think?

Side Profile with Aero Template:


No Spoiler Side Profile:

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Old 12-24-2012, 02:43 PM   #2 (permalink)
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Does the spoiler sit flush on the end of the hatchback, or is there a "hole" underneath it?

If there's a gap, I think it complicates things.
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Old 12-24-2012, 02:57 PM   #3 (permalink)
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Yup, there is a gaping large "hole" underneath. Would it simplify things if this hole was "filled", say with clear tape or some other clear plastic? It would turn it into a huge duckbill type spoiler.
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Old 12-24-2012, 03:23 PM   #4 (permalink)
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It's tricky to try to guess which configuration is better or worse.

But there are a few things you can try to figure this out experimentally:

1) Tuft test the rear glass. Easy to do! You're looking to see whether flow off the roof remains attached all the way to the base of the glass, or whether it separates at some point, causing reverse flow/vortices (tufts pointing the wrong direction, or lifting off the glass).

EG: This video shows the air flow pattern (attached flow) on the rear glass of a 1st gen. Honda Insight



FROM: Tuft Testing on Insight Hatch Glass (2006 Honda Insight, 1st gen.)

If you've got attached flow (all tufts streaming back) all the way to the base of your hatch glass, as the Insight does, then a big-ass spoiler isn't going to make things any better - it will more likely hurt.

2) Another approach is to do high speed A-B-A coastdown testing (if you can find a road where you can do the testing): Do a set of runs with the spoiler in place (A); Remove the spoiler & do another set of runs (B); Re-install the spoiler and do one last set. The higher the initial speed, the more likely you can tease out "small" aero changes.
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Old 12-26-2012, 12:08 PM   #5 (permalink)
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Sounds good, thanks. But if the tufts are not attached like I'm predicting, I still won't know if the spoiler is effective or not. If the tufts are attached, I know I can take the spoiler off.

Seeing how there is about 8 inches of snow on the roads around here, coast down tests will have to wait
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Old 12-27-2012, 05:26 PM   #6 (permalink)
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keep or not

Here's a couple thoughts.
*Hucho warns us that any roofline contour 'faster' than something like the 'Template' would be prone to generating longitudinal vortices of remarkable drag.
Since the Celica backlight is 'fast' compared to the 'Template' we might presume that you're in an at risk situation.
*Going back to a very thoughtful comment made by Bicycle Bob years ago;if the existing spoiler helps correct the backlight contour it may,if nothing else,break up and kill these strong vortices,rendering a wake of more homogeneous small eddies,which would create less overall drag.
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The 'gaping hole' underneath the spoiler is no doubt a concession to rear visibility,especially when backing,and also,since your in a 4-season environment,allow for snow 'runoff' rather than creating a dam,as with the 1980s Mustang GT 'birdbath' rear spoiler.
I'd be tempted to keep the thing.
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Old 12-27-2012, 06:21 PM   #7 (permalink)
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I'd be tempted to test it! But it sounds like that's not in the cards for a while.

Helpful as usual, Phil. Thanks!
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Old 12-28-2012, 12:29 PM   #8 (permalink)
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Helpful comments indeed. I am going to have to look into this Hucho guy's book now that you have peaked my interest!
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Old 12-28-2012, 01:00 PM   #9 (permalink)
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Ok, what about this?

Well since I don't have Hucho's diamond yet, what do you guys think of this? It would be a small Kammback made from fiberglass attempting to follow the template line. It retains the rear visibility.

This is a shot in the dark, but... would the air detach from the kammback and hit the spoiler to increase or decrease drag?

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Old 12-28-2012, 01:17 PM   #10 (permalink)
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I think you may be trying to fix something that we don't yet know is broken. (or "badly" broken, anyway)

I had a look at a bunch of rear view images of your car, and there's a not insignificant amount of plan taper in the greenhouse, and quite a gentle transition (very generous radius) in the C-pillar from "side" to "rear" surfaces. All of which suggests to me the risk of vortex formation on this car is probably not big.

I'm away from home, so I don't have my copy of Hucho handy, but he laid out a chart comparing various rear hatch/fastback angles and their effect on Cd that illustrated the problem of vortex formation. But my foggy memory tells me your hatch isn't in the "danger zone".

If I were you, I'd start at the start: tuft testing your rear glass. It doesn't take 10 minutes to set up (and you can even do it with 8 inches of snow on the road ).

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