The most unusual Chaparral was the 2J. In addition to a powerful 700 hp engine, and a three-speed semi automatic transmission, the back of the 2J housed two 17-inch fans driven by a single 45 hp snowmobile engine. The Can Am Series had no engine size limit, so the snowmobile engine wasn't affected by an engine displacement maximum. The purpose of the fans was to 'suck' air from under the car to provide downforce. This gave the car tremendous gripping power and enabled greater maneuverability at all speeds, which cannot be achieved by simpler aerodynamic devices such as diffusers and wings. 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'. It also had ground effect Lexan-plastic skirts to keep air from leaking in, a technology that would appear in Formula One several years later.
The 2J competed in the CanAm series and often 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 SCCA (even though it was approved by the SCCA prior to the car's first race). The SCCA succumbed to pressure from other teams, McLaren in particular, who argued that the fans constituted 'movable aerodynamic devices' which were outlawed by the international sanctioning body FIA (which was 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 was not outlawed, it would likely kill the CanAm series by totally dominating it - ironically, something McLaren had been doing for years[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.
