Fluff Test!
 

I'm borrowing a 1997 Corolla from my parents while the Nut Wagon is being repaired and/or ignored. About 1-2 inches of snow on the car. I cleared off the hood and windshield and let the air do the rest. An earlier tuft test showed good flow across the top of the spoiler. Other than being an excellent trunk handle, is the spoiler good or bad?

http://img.photobucket.com/albums/09...flufftest1.jpg
http://img.photobucket.com/albums/09...flufftest2.jpg
http://img.photobucket.com/albums/09...flufftest3.jpg
http://img.photobucket.com/albums/09...flufftest4.jpg
http://img.photobucket.com/albums/09...flufftest5.jpg

Other snow-free views:
http://img.photobucket.com/albums/09...es/97rolla.jpg
http://img.photobucket.com/albums/09...7rollacrop.jpg
http://img.photobucket.com/albums/09...7rollarear.jpg

It raises the back end closer to the template....sorry, Thee Template ©®™....So it prolly helps a little bit, prolly doesn't hurt.

That's some supercar styling right there :D

Very cool! What was the average speed during the fluff test?

good or bad
 

If the flow off the roof doesn't reattach at the trunklid you have negative pressure above the rear creating rear lift
http://i1271.photobucket.com/albums/...ead2/12-19.jpg
Adding around 35mm of rear spoiler gets reattachment and some lift reduction
http://i1271.photobucket.com/albums/...ad2/12-195.jpg
Going over 100 mm you get more down-force,but greater overall drag,defeating the purpose of the spoiler
http://i1271.photobucket.com/albums/...ad2/12-194.jpg
*The spoiler 'sees' some of the more energetic air and captures it's momentum
*An early Firebird spoiler goes all the way to the 'Template'
http://i1271.photobucket.com/albums/...d2/06-2829.jpg
The Audi TT goes near it,but not quite to it.
http://i1271.photobucket.com/albums/...d2/06-2827.jpg
*Without a wind tunnel it's hard to know what actually happened with these cars.
*I'd recommend staying with the spoiler if for no other reason,to reduce rear lift,and chance of hydroplaning back there.

I'm not sure what the average speed was, but the peak speed was about 50 MPH. This was 2-3 miles of driving.

My '95 Prizm (Corolla) 4 dr had a similar flow pattern. So the spoiler needs to be 1 3/8 in. higher at the back than the front.

The hole at the centre tells that there is a vacuum there, doesn't it ?

I would think about a roof top spoiler to help with that.

It looks like the upper corners of the rear window have vortices, that are getting sucked down to the outsides. Those are the main drag issues, I think?

Find other examples in the snerodynamics thread.

It looks like you were traveling in a crosswind. The dimple in the center is interesting, was it not there when you started?