Legends of the Track: Porsche Can-Am 917/10 “Turbo Panzer”

At the end of the 1971 season, with two consecutive Sportscar Championships under its belt, the Porsche 917K (in Project CARS 3) was made redundant by the new Group 5 rules that mandated engines of only under 3-litres. Porsche, in response, turned its focus west—to North America and the mythical Can-Am Series.

It was a decision that changed motorsport forever.

Porsche 917 at Sonoma in Project CARS 3

Can-Am

Can-Am was a series that was run under Group 7 rules, though calling them “rules” is a bit exaggerated—it was basically a “pass a basic safety test, have two seats, have all four wheels covered, and go race” series where anything and everything went.

Of course, if your anything and everything was under 700hp and heavier than 800KGs, you were going to get creamed by the 7L V8 Chevys in the all-dominant McLarens, and the virtuoso aerodynamic genius of Jim Hall over at Chaparral (who invented the aero wings).

Can-Am was the scene of some of the fastest, fiercest race cars the world has ever seen―and looking back almost 50 years, it’s safe to say we’ll never see anything like it again. The money running around the series―US dollar prizes―meant the cars were driven by global superstar drivers, too―Andretti, McLaren, Stewart, Surtees, you name your ’70s star, and he’d have been driving stints at Can-Am events in Canada and the US.

Can-Am in its glory years―1967-1973―was wild, loud, and super popular―an electric mix of speed, noise, and danger that transfixed the fans who flocked to classic venues such as Watkins Glen, and long-forgotten ones such as the Stardust International Raceway in Las Vegas.

Porsche 917 at Sonoma in Project CARS 3

Porsche Comes to Can-Am

Porsche had already been dabbling in Can-Am since 1970 in the guise of Jo Siffert’s semi-works 908 Spyder and the hastily created (and decapitated) Porsche 917 Spyder for the ’71 season. Both were gobbled up by McLaren’s M8F. But with the death of the 917’s native series and North America proving an attractive market for sales of production cars, Porsche decided to get serious about its Can-Am program for ’72 alongside Siffert, whose star was very much on the ascendancy after his Formula One win at the Austrian Grand Prix. But when ‘Seppi’ lost his life at a non-championship event at Brands on a cold day in October ’71, Porsche needed a Plan B and found it at a newly formed race team named Penske and their driver-cum-engineer Mark Donohue.

Aside from their reputation, Penske, like Porsche, had also been pottering about in Can-Am for a few years without much success before settling in nicely in Trans-Am (then the world’s most dominant touring car series) where the Penske-Donohue pair were winning and battling for championships with the Sunoco Camaro that you can race in Project CARS 3.

It would take a lot to get Penske to drop his priority with the Trans-Am program, but Porsche’s offer—big budget, full-factory backing, and a new tech’ engine purpose-made for Can-Am—proved too enticing to reject.

Porsche 917 at Sonoma in Project CARS 3

Penske Racing Porsche and the Turbo Panzer

The new engine was the Porsche 917’s bulletproof flat-12 upped to 5-litres—and then turbocharged—that’d been running the test-miles throughout the summer of ’71. Turbocharging back then was very much a high wire walk into the unknown. With a few notable exceptions through the years (mostly on ovals), engines were either naturally aspirated or crank-driven superchargers because the barrier to success—the massive delay between when the throttle was squeezed and when the power came in—made it impractical for road circuits.

On the other hand, the raw power from turbocharging made finding a solution to the resultant lag something Porsche were keen on solving. Not surprising since the new turbo on the re-engineered Can-Am-destined Porsche 917—now dubbed the 917/10 and weighing less than 750KGs—was pushing over 900hp, with 60mph rushing by at two seconds, 100mph in under four, and 200mph in 13.4s. Early testing by Porsche test-driver Willy Kauhsen reported wheelspin in top gear—at 200mph!

Not surprisingly, Kauhsen also found the engine undrivable: massive dollops of turbo lag through most of the rev’-range followed by mayhem when the turbos spooled in. And when, on a cold day in early February in Florida in’72, Porsche finally sent the turbo-engine to the US, Donahue’s feedback was much the same.

“I tried to drive it for a few laps and discovered that the throttle worked like an ignition switch—it was either wide-open power, or off,” Donohue would recall. “After a banzai effort I got down to about the same lap time as the non-turbo engine with about 300 more horsepower.” That was before the engine grenaded and the pieces were sent back to Germany.

Porsche 917 at Sonoma in Project CARS 3

Through the winter of ’72, Donohue continued testing new evolutions of the turbo flown into the US, and while it was clear the power was there, drivability wasn’t being improved at all. Aggravated, Donohue hopped on a plane to Germany.

At Porsche’s test-track at Weissach, Donohue attempted to demonstrate the problem he was experiencing with throttle response, but it soon became clear there was a disconnect between what he was saying and what the Porsche engineers were hearing. With Donohue at a dead-end, “the Captain” Roger Penske himself came flying into Germany to deliver his verdict―with that engine, he told a shocked delegation from Porsche, they were going to get smoked in Can-Am.

Porsche sprang into action and delivered a new engine in a week. It felt even worse. Donohue, exasperated, asked them to dump the engine onto the dyno.

“I looked at their dyno output curves,” Donohue recalled in his autobiography ‘The Unfair Advantage’. “They had all the necessary data―torque, rpm, boost pressure, and so on―except the curves started at 5000rpm. I said, ‘Why are there no curves up to that point?’ They said, ‘The motor does not run there.’ I thought, ‘That’s what I’ve been trying to tell you for a month!’ I couldn’t believe it was that simple. I couldn’t believe they had simply calibrated the fuel injection for wide-open throttle with full boost and had totally ignored any part-throttle operation.”

With Porsche’s engine man Flegl, Donohue worked at getting a complete map of the engine across the entire rev-range with fuel-maps aligned to various boost pressures. A week later, they ran the car again, and Donohue immediately cut the lap record by over a second on his first flying lap.

That’s when Donohue sent Penske the now famed telex from Germany that read: “PLEASE INFORM CAPTAIN OF MAJOR BREAK THRU”.

Porsche 917 at Sonoma in Project CARS 3

Domination

With the engine sorted, it was time to get back to the US to tune the handling. With an extra 400hp, the old test-mule 917/10 was a bit of a beast, but who else could tame it other than Donohue?

Or so everyone thought.

As it turned out, the new beast from Zuffenhausen was not for taming. At Road Atlanta, at over 240kmh, the rear-end bodywork ripped away from Donohue’s car and, a second later, Donohue and the 917/10 went airborne. By the time the car had come to rest in a cloud of debris and dust, Donohue was sitting strapped in his racing seat with his broken legs dangling in the air where once the front of the car had been.

Donohue’s season was done: testing and racing were turned over to a hastily recruited George Follmer.

“It just doesn’t feel right,” Donohue said while watching Follmer from the sidelines. “Seeing another man driving your car, a car you know so well.”

If that was hard to watch, Donohue must have been even more disconsolate by the end of the year when the Porsche 917/10 ended five consecutive years of McLaren dominance. The Can-Am Championship that year featured nine races: the Penske-Porsche car with Follmer at the wheel won six races.

Porsche had not only wrested away Can-Am dominance from McLaren, they’d ripped a hole into the future of motorsport with their turbo.

Porsche 917 at Sonoma in Project CARS 3

The following year, the 917/10’s successor, the 917/30―developing a reputed 1,600hp―blitzkrieged everything in its wake with Donohue at the wheel. It started the season as the ‘Turbo Panzer’ and ended the season as the ‘Can-Am Killer’―Porsche’s dominance was such that McLaren walked away from Can Am and the series itself would endure just one more season before shutting the doors. 

Having eviscerated the field, Porsche left Can-Am with titles, glory, and turbo technology a generation ahead of everyone else. They also left the US with a speed record when Donohue took the 917/30 to Talladega and clocked 241mph (388kmh).

Back in Europe, Porsche extended their turbo program to their early test-mule, the Carrera RSR, which led to their first-ever 911 Turbo road-car in ’75. Buoyed by the reliability of the RSR, Porsche returned to sportscar racing in ’76 with the Porsche 936 in Group 6, and the Porsche 935 in Group 5―both available in Project CARS 3―and dominated sportscar racing for a decade. Then they stuck their turbo into the ground-effects Porsche 956/962―also available with Project CARS 3―and smoked everyone into oblivion.

With about a ton of turbo horsepower, serious lag, and weighing around 780kg, the Porsche 917/10 in Project CARS 3 is about the most challenging car you’ll ever get to race. This car will earn your respect very quickly—and it remains one of the most important race cars that ever turned a wheel.