History Changer - 1974 Porsche 911 Carrera RSR Turbo 2.1.

45 years ago, Porsche had launched the 917/20, a car built for racing in the Can-Am Challenge Cup, North America’s almost restriction-free racing series made for prototypes. The 917/20 was driven by George Follmer, and so, after this car’s dominance in the 1972 championship, the face of motorsport was inevitably changed during the remaining 70’s and 80’s decade.
The change was thanks to the fact that the 917/20 was Stuttgart’s brand first turbo’d racecar, belting out 850hp from a boxer 12 engine.

After two very succesful seasons of forced induction dominance, Porsche had realized that turbocharging was the way to go if they wanted to secure more titles under their belt. And so they did, in 1974 the mechanics at Stuttgart took two 2.8l RSRs and modified them, fitting them with 3.0l naturally aspirated engines, forcing them to race in the prototype class, against bespokes prototypes such as the likes of Matra and Ferrari, for the rest of the 1973 season.
For the 1974 season, they wanted to introduce a new, turbocharged engine, and since it had to be built under group 5 regulations, the fact that it was turbocharged meant that the engine displacement couldn’t be bigger than 2.1 litres. And for the mechanics to be able to downgrade the displacements, they used a bore/stroke ratio of 83mm/66mm of the original 911 two liter engine, so in reality, what they did was they downsized and engine using the measurements required to expand an engine.
Those modifications meant that the new 2.1l engine was able to produce 500bhp @ 7.600rpm and 405lb-ft of torque @ 5.400 rpm.

Of course, all of this had to be lubricated and kept cool, and for this to be achieved, the car was lubricated with a dry sump system, while cooling was in charge of a big intercooler that added to the ‘natural’ cooling of the engine. ‘Natural’, I say , because the engine was mounted in the classic Porsche location, in the back of the car, and this meant that the turbo was sticking out of the whole body of the car, meaning that it’d be constantly breezed by fresh air. Of course, everything has its pros and cons, and this isn’t by any means the exception. Because of the adopted forced induction, turbo lag at low RPM is always a thing, and this meant that the driver had to moderate their driving style in corners, because otherwise it could have very probably ended up in a spin.

As Pirelli’s slogan reads, “Power is nothing without control”, all of this power had to be put down to the road in a way. And so power was put down to the rear wheels via a Type 915 5 speed manual ‘box. Chassis strength was also required to be able to handle this, and to solve this, a steel monocoque was positioned beneath the fibreglass reinforced panels. Both the steel monocoque and plastic panels helped to keep weight down, but Porsche being Porsche kept on shedding weight. They achieved further weight reduction by replacing the rear torsion bars for new, lighter aluminum arms and titanium shock absorbers, removing 60 pounds (30kgs) off the total weight of the car. The rest of the suspension was composed of McPherson struts and titanium shock absorbers, together with lower wishbones up front and the aforementioned modifications made to the rear suspension. Handling was in charge of a conventional rack-and-pinion system, while stopping power was provided by drilled and slotted brakes all around. The interior was also obviously stripped down to the absolute basics, and a multilink aluminum roll cage was added together with the racing gauges. All of this brung the kerb weight down to a total of 1,808lbs (820kgs), with that allowing for a .61hp/kg power to weight ratio, and 70% of the weight positioned on the back of the car. The lightweight car and the powerful engine combinaton was good for a top speed of over 186mph (300kph).

The 2.1l Turbo made it’s debut on the 1974 1000 kilometers of Monza, where it got an impressive 5th place, although the 2.1l Turbo’s best result was securing a podium, finishing second on the 1974 24 Heures du Mans. As if those results weren’t impressive for a racecar based on production cars that was being raced against full fledged prototypes (Matra, Ferrari…), the German contender secured a third place on the Spa 1000 of the same year.

Fast forward to 2017, and it’s evident that Porsche’s turbocharged monsters eventually paved the way to modern day turbo’d cars. What remains of the 70’s turbo dominance by Porsche is on the Porsche Museum, in which one of only 4 RSR Turbos is in exhibition.

[Writer’s note: This blogpost is the finished product of starting a blogpost about Porsche’s ‘Moby D¡ck’ 935, and having to leave for a trip, coming back to go to a party, waking up to return to my home country, getting to my house only to realize a blogpost had already been written about the 935. CTzen Joel Chan told me to replace the 935 blogpost with the 2.1 Turbo RSR, and so I begun writing at 10:50pm on a Sunday. Safe to say, this was one of the blogposts I enjoyed writing the most, and I’ve also come to the realization that writing about racecars is far more difficult than writing about production cars, there are no reviews or anything to base an opinion on! Just pure and hard facts.
After everything being said, I should finish this note and put my signature on it.
-AGR]

Until then, Sir GT-R, out.