370 pounds of downforce at 100 mph
There was an article about the 1979 280ZXR in the Escape Roads section of the 6/9/03 issue of Autoweek that stated the following.
"The good news was the new ZX was cleaner aerodynamically than its predecessor. Like most cars, however, the 280ZX developed lift at speed, so Datsun racer Don Devendorf and John Knepp of Electramotive shaped a whale tail spoiler to press the car into the pavement. Racing rules being what they were, though, that big wing couldn't be used unless it was homologated--accepted as a standard-issue part on production models.
Homologation for IMSA meant 1000 units, and a cooperative Nissan obliged by producing exactly that number of special models with the huge tail. Officially a $399 option package, the special model was dubbed the 280ZXR and had a large 'ZXR' on the two-tone blue and black tape stripe down each side. Matching stripes went on the hood, and the only color available was silver mist. The cars were all the same, with no options save air conditioning. Not even alloy wheels were included.
The spoiler, made of molded rubber, was unpainted. The spoiler was the real deal, generating 370 pounds of downforce at 100 mph. Racers could buy the spoiler out of the Datsun Competition Parts Catalog."
When I bought this competition whaletail years ago (still not installed on my ZX), I remember the catalog suggesting that a front air dam be used with it for street applications.
John