[JulianEdgar]

Originally Posted by aerohead

1) the flow separates where the truncated roof ends. You can see the streamlines continue on and the void left underneath.
2) the pressure in that void has the pressure imparted by the streamlines directly above the TBL at the point of separation.
3) since this low pressure region occurs 'over' the rear of the body below the void , it's imparting lift. Just like Taycan, Panamera, Cayman, 911,.........
4) this low pressure is also connected to the wake, lowering base pressure, increasing pressure drag, increasing overall drag.
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5) And observing those streamlines that have left the Porsche, had the roofline continued on, following the streamlined path, they'd be underneath more widely-spaced streamlines.
6) velocity would be lower there, by definition.
7) lower static pressure above the panel would be higher.
8) lift would be reduced.
9) if the body were extended to full verjungungsverhaltnis, the local streamlines would be at maximum- spacing, lowest velocity, highest pressure, lowest lift, lowest drag.

It's an interesting theory, but it's one completely different to the last one you put forward!

It's hard to keep up when the theory changes between posts.