Chaparral J2
"The most unusual Chaparral is the 2J. On the chassis' sides bottom edges are articulated plastic skirts that seal against the ground (a technology that would later appear in Formula One). At the rear of the 2J are housed two 17-inch fans driven by a single 45 hp two stroke twin snowmobile engine. The purpose of the fans was to evacuate air from under the car to provide down-force. This gave the car tremendous gripping power and enabled greater maneuverability at all speeds. Since it created the same levels of low pressure under the car at all speeds, down-force did not decrease at lower speeds. With other aerodynamic devices, down-force decreases as the car slows down or achieves too much of a slip angle, both of which were not problems for the "sucker car".
The 2J competed in the Can-Am series and qualified at least 2 seconds quicker than the next fastest car, but was not a success, because it was plagued with mechanical problems. It ran for only one racing season, in 1970, after which it was outlawed by the Sports Car Club of America (SCCA). although originally approved by the SCCA, they succumbed to pressure from other teams, McLaren in particular, who argued that the fans constituted a"movable aerodynamic devices", outlawed by the international sanctioning body, the FIA, a rule first applied against the 2E's adjustable wing. There were also complaints from other drivers saying that whenever they drove behind it the fans would throw stones at their cars. McLaren argued that if the 2J were not outlawed, it would likely kill the Can-Am series by totally dominating it — ironically, something McLaren had been doing since 1967.[3] A similar suction fan was used in Formula 1 eight years later for the 1978 Swedish Grand Prix, by the Brabham BT46B, but was banned soon after. It was ruled that the fans were considered movable aerodynamic devices and thus both 2J and the BT46B were outlawed under the same rule that outlawed movable wings years earlier." - Wikipedia
