[Otto]

Originally Posted by NeilBlanchard

Yes, the 0.13 number was a model or mock up earlier in testing. They also adjusted the ride height to get the optimum drag: too low increased it (due to increased pressure underneath?) and too tall also increased it (probably because more tire was exposed?). We have gone over this, and gotten a lot of pictures, including in the wind tunnel; here's my collection of Schlörwagen "Pillbug" pictures including the Mercedes 170H chassis it was built on:











The 0.18 number is for the actual working car, with cooling set up, etc.

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Got any pics of the underside of this vehicle?

It does not appear to have wheel fairings or spats, which would help.

And, gap between vehicle and ground relates to interference drag. There is an optimum height, as noted in Hoerner's Fluid Dynamic Drag book with cites of external stores of bombs, fuel tanks, etc. in aircraft. Too close means a bit of savings from less wetted area of pylon, but more than offset by too much interference of flows around wing and bomb. Too far apart means less interference drag, but increased pylon drag. So, there is a sweet spot in gap adjustment. I think Citroen with its adjustable height also dealt with this issue.