The 1970 Chapparal J2
The absolutely insane 1970 Chapparal 2J Can Am racer, nicknamed 'The Vacuum Cleaner'
Something altogether new and different showed up on the Can Am circuit in 1970. Fielded by team Chapparal, the boxy-bodied J2 was probably the most 'out there' car ever seen on the track. As Can Am racers went, it was fairly conventional at the front, but the rear end was where the designer's thinking was, well, entirely outside the box...
It was powered by a thundering all aluminum 650 horsepower ZL1 Chevrolet 427... and a Rockwell JLO 247 cc 2 stroke snowmobile engine driving two cooling fans taken out of a Howitzer M-109 self propelled gun!
The fans' job was to suck air out from under the car to create downforce. While other cars used drag-inducing spoilers and wings that only created downforce at high speeds anyway, the J2 had downforce even sitting still. It had equal downforce at all speeds. And no added drag at high speed. The downforce prevented wheelspin even off the line, and absolutely glued the car to the ground in turns at any speed. The huge twin fans had a combined 9650 CFM at 6000 RPM of the JLO engine, itself snugly nestled between the big collector pipes from the headers above and at the rear of the 427 rat mill. Combined with some serious Lexan ground effects side skirting around three quarters of the car, they added about 2200 pounds of downforce... to a car that barely weighed 1800 pounds to begin with.
Supposedly, the car could be driven at 25-40 miles per hour from the output of the fans alone. That leaves one as to wonder at the true top speed the car was capable of with the 427 combined with the boost of the fans. But that wasn't really their intended duty. Their job was to stick that car as tightly as possible to the asphalt in the turns while the torque monster 427 did its thing. Oversteer and understeer were both pretty much things of the past with the active ground effects system of the J2. The car could be driven harder into the turns, harder through the turns, and harder out of the turns by being actively stuck to the ground by the extractor fans at all times. As hard as the driver romped on the go pedal coming out of the corners, the tires still wouldn't break loose with all that downforce. It didn't skid braking into the turns either. Tire wear - even at the front - would likely have been drastically reduced as well as a result.
Nothing could equal the J2 after the straightaway ended. While the awesome 1100-1600 horsepower Porsche 917 could almost surely leave it behind on a long straight, even it didn't have a chance to keep up to the J2 when things got twisty. Can Am was more about handling in turns than it was about all out straight line speed, so the Chapparal team's edge was hard to overstate. Aptly referred to as 'The Vacuum Cleaner', the car was sucked down to the ground about two inches when the auxiliary engine was brought up to speed. The racer's builders believed it could actually be driven vertically along a wall by the suction created by the fans!
This was a LOUD Can Am car. Besides the open header 427 Chevy thumper, there was also the added noise of the completely un-muffled two cycle snowmobile engine running at 6000 RPM and the huge high volume fans. All the exhaust pipes and the fans exited out of the flat rear transom of the J2. Following closely behind the combined auditory output of this incredible car - if you even could - wouldn't be very much fun at all.
Alas, even in the nearly anything goes Can Am series, the Chapparal J2 'Vacuum Cleaner' was quickly outlawed as other team's drivers complained the J2's downforce fans sucked up any oil or dust or debris that happened to be on the track and violently sprayed it out at anyone unlucky enough to be behind it. And that would be most of them.
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