Watching it happen, it was hard to appreciate the magnitude of the achievement. The big blue roadster hardly made any noise, and it was being driven with such poise, such command, that its motion around the track didn’t really rivet the eye either.
Yet, as Mark Donohue cruised his turbocharged Porsche Panzer around the final lap of his last Can-Am race at Riverside in 1973, he was climbing a summit of personal fulfillment. The legendary driver-engineer himself said that taming this immensely powerful, initially very difficult machine was “a monument to my career.”
Thirty years later, Donohue’s triumph seems even more remote. We don’t see feats like his anymore, at least not in racing’s top ranks. In today’s more complex, more restrictive environment, any one individual has far less control over the shape and performance of a vehicle.
Yet Donohue was of an era that fostered drivers who founded their own marques—ambitious and inventive men like Bruce McLaren (McLaren), Jim Hall (Chaparral) and Dan Gurney (Eagle). While Mark didn’t create or name the Can-Am Porsche—nor did he work alone, by any means—the sleek supercar certainly bore his identity.
Donohue wasn’t part of Porsche’s Can-Am effort at its beginning. In fact, he was a competitor—for one race. In 1969, both parties joined the Canadian-American Challenge Cup series at its fifth round, Mid-Ohio. Donohue and his Roger Penske racing team immediately saw their customer-model Lola wasn’t going to be competitive against the McLaren factory’s all-conquering “Bruce and Denny Show,” and left to concentrate on venues where they could be successful, such as Trans-Am and Indianapolis.
Jo Siffert and Porsche persevered with the Can-Am. The Swiss driver was heading a quasi-factory program that used a topless version of Stuttgart’s new 917 Le Mans coupe. As a Can-Am car, the 12-cylinder, 4.5-liter 917PA (for “Porsche+Audi”) Spyder was underpowered and overweight, but it was very reliable. Despite his late start, Siffert wound up the 11-race 1969 series 4th on points. Two years later, with an updated, 5.4-liter 917/10, he repeated that performance—despite tragically losing his life in an F1 crash just before the end of that 1971 Can-Am season.
By that point, Donohue and Penske were working behind the scenes with Porsche toward an all-out, factory-backed assault on the Can-Am for 1972 and beyond. Gaining more power was the primary concern. The Can-Am McLarens of the day had 8.3-liter Chevys making about 750 horsepower and 650 ft-lbs of torque. The best the 5.4-liter Porsche could muster fell short by almost 100 hp and 200 lb-ft.
Porsche did try the traditional Can-Am trick of adding displacement, testing an enormous opposed 16-cylinder, 7.2-liter engine. At some 880 claimed hp, it probably would have done the job. But the engineers were more intrigued by the challenge of turbocharging their familiar 12.
It really was a challenge. At that stage in history, we had seen a few turbocharged engines in road racing, but none had worked very well. They put out big power, but it was not controllable power. The problem was “throttle lag,” sluggish response to gas pedal input.
Porsche also had this problem at first. Twin-turbo 917 motors were making stupendous numbers on the dyno, upwards of 1,000 peak hp. But there was no bottom end. Shortly before the opening race of ’72, Roger Penske shocked his client by suggesting they’d better not go. Another shock was last-minute, hands-on intervention by an exasperated Donohue—traditionalist Europeans were not used to a mere driver playing a lead role in engineering.