The Chaparral 2J, known as the 'fan car', or 'sucker car', was the first of only a few race cars to feature fan-assisted aerodynamics. It was powered by a powerful aluminum-block 8.1 litre Chevy V8, which was mounted to a custom 3-speed automatic. The automatic transmission was unique enough in itself: It was basically a 3-speed manual transmission with a torque convertor in place of a clutch. Each gear was selected in a similar manner to a manual transmission. However, by eliminating the clutch, the driver could use his left foot exclusively for braking, aiding concentration. Only three gears were available, but their ratios were similar to 3rd, 4th, and 5th gears on a conventional 5-speed transmission. This meant the car took some time to reach a decent speed, as it pulled off from a standing start in the equivalent of 3rd gear.
The car was basically a giant vacuum-cleaner on wheels; a movable skirt beneath the car sealed in the vacuum created by two large fans mounted at the rear. The whole system worked something like a hover-craft, only in reverse! The area encompassed by the skirts started just behind the front wheels and completely enclosed the rear wheels. It covered approximately 2/3rds of the area of the underside. The skirt consisted of seperate sections made of a durable synthetic material called Lexan, similar to plexiglass. Each section articuled indpendently to the aluminum monocoque chassis, and was held down onto the road surface by springs. This was to ensure the best seal between the chassis and the road surface, even over undulating race tracks.
The two 17-inch diameter fans were powered by a single 45hp, 274cc, 2-cylinder JLO Rockwell snowmobile engine, which ran at constant speed. This means the downforce created by the vacuum was near-constant at all speeds, unlike conventional aerodynamics which created exponentially more downforce as speeds increased. This method was preferred to the alternative of powering the fans from the engine, as the downforce would have varied slightly with the revs, which, considering the car only had 3 speeds, might have varied quite a bit. The snowmobile engine was mounted above the transmission and protuded slightly above the rear bodywork.
The vacuum-traction system was extremely effective at forcing the car onto the road, resulting in increased acceleration, braking, and cornering speeds. As a side benefit, the large amount of volume contained within the underside of the car and the sides of the skirt acted as a vacuum 'reservoir', allowing the driver a little time to respond if the fans suddenly cut-out. This was a lot safer than the previous generation chaparral, which would have lost traction instantly if the rear-wing failed, which unfortunately was most likely to occur at high cornering speeds.
The chassis (apparently) consisted of square-membered alumninum tube framework with aluminum panels. Once the cooling air had flowed through the forward mounted radiator, it was expelled over the top of the car. This was done to ensure adequate airflow and prevent interference with the vacuum traction system.
The classis burble sounds emitted by the chevy V8 as it was run through the gears, in combination with the rasping snowmobile engine and the constant-pitch whine of the vacuum fans, made the car sound quite extraordinary. The car would visibly 'squat' as the fans powered up for the first time, and the vacuum system generated so much downforce at low speeds that wheel-spin from a standing start was virtually eliminated, even with over 700hp on tap! With enclosed rear wheels and two fans protuding out the back, the 2J looked and sounded like something out of science fiction, and its performance around the racetrack was equally unreal.
A quote from Jim Hall (Chaparrals main driver): "The 2J's major advantage is that it will corner faster on low-speed corners, the ones that are 30 to 90 mph in normal Can-am cars. these corners predominate on Can-Am tracks. It means you can leave the corner faster, with more speed, and carry that speed down the straight." The vacuum-traction system allowed the chapparal to generate up to 0.5 g more lateral acceleration during cornering; at all speeds. Hall: "At first, the 2J was a real shocker! Side forces (in cornering) are really impressive. Holding your head upright becomes extremely difficult. On a normal Can-Am car you have to bend your head over about half-way to balance the cornering force. In the 2J the cornering forces want to bend your head right over. We're going to have to get used to it. I've banged my elbows and knees on things I never used to touch. Another change in the 2J performance over past models is the quickness and directness in steering. You get a direct change in direction when you turn the wheel. The downforce increases the contact load between the tires and the road without increasing the mass of the car. Steering effort is high and any little change causes a significant side force.", "I simply can't believe the braking capability of this car.", "It feels like it will decelerate about twice as fast as any Group 7 car I've driven."
Text by: Michael J. Bloxham.
