[Phase]

Originally Posted by aerohead

Consider that, they've had six years to shave thirty counts off a car, which is now a BEV.
The '6's 'engine is 350% more efficient than yours. Consider what that does to radiator size requirements, grille opening.
Not 'smoother' but 'smoothest' underbody. 1983 technology.
Add my 1991 front gap-fillers like they did.
Their 18-inch aero wheels are the only ones which will fetch 0.21.
'Cameras' or mirrors? They don't say.
You're free to do wheel skirts. Air curtains are a joke in comparison.
It took PORSCHE 25-years to ditch the 26-degree roofline. They won't be going back. PORSCHE's 'failure' can magically become Hyundai's 'success'?
You can clearly see the 'fail' in the smoke flow images. Any additional chance for drag reduction was lost with that lowest streamline quitting the body, long before 'touching' any part of that rear slope.
A 'small' wake is meaningless if the base pressure due to separation-induced vortices and turbulence is lower than that of a 'larger' wake.
Without adding an inch to your car you could be at Cd 0.20. We talked about this when you first started your thread.
Dr. Teddy Woll of Mercedes Group gives you full permission to insulate your entire exhaust system, and hang a perfectly smooth belly pan and diffuser underneath it.
If you have, Modifying the Aerodynamics of Your Road Car, take a look at page-141. The separation edge addition to the 2015 Buick Excelle GT's taillight lens was good for a 0.3% drag reduction. I suspect that this is about what you might expect from a 'separation trap.' You'd never 'see' it, even if it was there.

the best things i could do that i havent done without adding an inch just seems to be the snoother under body and a proper rear diffuser