[aerohead]

At breakfast I was looking at the 1981 Opel TECH-1 concept car, designed by Erhard Schnell, based on GM's T-Car platform ( Kadett ).
There's not a great deal of data available for the car but they mentioned:
* front fascia
* panoramic windshield that blended into the A-pillars, killing vortices there
* all-flush glass
* not mentioned is the Aeroback rear roofline with small notchback deck
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I believe that the '81 model Kadett was Cd 0.52, and fell to Cd 0.475 for the 1982 model year.
At Cd 0.235, the TECH-1 would only have 45% of the Kadett's drag ( at equal frontal area ).
It's fineness ratio is close to that of the Cd 0.23 Tesla Model Y, Cd 0.235 Toyota FT-Bh concept of 2012, and Cd 0.235 Renault EOLAB concept of 2014.