> Once the cross sectional area through which a stream of air passes
> is increasing at a rate greater than 5 degrees, the flow becomes
> turbulent and the Bernoulli principle ceases to apply.

had 7 degrees written down here, hmm, gata find the source...
this also applys to increasing pressure in a "ram air" induction too :-)

look at the Darrel's expanding area before the turbos
http://www.sportclass.com/2003_gallery_images/2003_51_lrg.jpg

Rob