2,520 deutschmarks – that was the premium, Porsche customers had to pay for a Carrera RS 2.7 in 1972/73 compared to the Porsche 911 S 2.4. From today’s perspective, this was money well spent, since really good Carrera RS lightweight models can cost seven figures. The 911 S 2.4, on the other hand, costs many hundreds of thousands of euros less. But why is that? Where exactly are the differences?
Porsche crowned itself overall winner of the 24 Hours of Le Mans for the first time in 1970, the second time the 917 was used. The experience gained in developing the 917 – the cost of which brought Porsche close to financial ruin – was to be used to reorganize the brand’s motorsport program. From now on, motorsport based on production vehicles was to become the brand’s core competence. A homologation model for use in Group 4 was therfore needed.
But the 911 S 2.4, Porsche’s top model at the time, would simply not have been suitable as such. The relatively narrow body of the 911 would only have allowed tires with a relatively narrow width. This was because widening racing cars was limited to 100 millimeters starting from their production counterparts. The homologation regulations also denied excessive and costly lightweight construction. At that time, racing cars were not allowed to weigh less than the production models. Thus it was written in Appendix J, art. 252 n) of the FIA’s sporting code.
There was also the matter of displacement. The 911 S would not have been allowed to exceed 2.5 liters of displacement in racing. Expansion was only ever possible up to the next full 0.5 liters. A production engine with a displacement of over 2.5 liters would consequently have allowed a racing unit with up to 3.0 liters.
Porsche took the 911 S 2.4 as the starting point for developing their Group 4 homologation model. To save weight, plenty of insulation and carpets were omitted from the interior. Instead, there were felt linings, rubber mats and thin glass windows from Belgian manufacturer Glaverbel. Where it was justifiable, thin sheet metal was used. Even the traditional Porsche crest on the trunk lid gave way to a glued-on emblem.
Luckily, the engine block of the Porsche 911 S 2.4 was equipped with enough reserves. This made it possible for Porsche to coax more power out of the six-cylinder engine at a reasonable cost. The RS received new light-alloy cylinders with 90 instead of 84 millimeters of bore and state-of-the-art Nikasil coating. Displacement increased to 2,687 cc. With the same crankshaft, connecting rods, compression ratio and timing as the 2.4-liter engine in the 911 S, the engineers achieved 20 more horspower and increased the torque by 39 Newtonmeters for the Carrera RS 2.7. That may not sound like much, but it noticeably changed the engine’s characteristics. For racing use, the engine could even be bored up to 3.0 liters.
The rest is history by now: first 911 with different tire sizes front to rear (rear 7J instead of 6J x 15), bespoke skirts, wider flared fenders and a distinctive aerodynamic aid that was quickly christened the ducktail! No other design feature has achieved comparable prominence in the car world, yet it was created solely for functional reasons. It was intended to stabilize handling and, as a by-product, added 4.5 km/h to top speed.
“To compare these classic Porsche 911s, I always recommend looking at historical test reports”, says Tobias Schwarz of RSR.at, or better known under its founder’s name Dr. Georg Konradsheim. He should know, after all Konradsheim is considered a Carrera RS luminary in the industry. Together with Dr. Thomas Gruber, Konradsheim published the comprehensive Carrera RS book, also known as the “Carrera RS Bible”. This also includes an RS register listing all 1,580 RS ever built.
“Paul Frère was testing the Porsche 911 Carrera RS at the time. Since he drove the 911 S 2.4 privately, he was able to make a direct comparison and highlight the differences,” says Schwarz. The test report is also printed in the RS book. Its depth is really impressive. In it, Frère reports driving impressions from several thousand kilometers, including a visit to a racetrack. The conclusion: Porsche’s first 911 Carrera RS is nowhere near as raw and loud as feared. On the contrary, the Belgian journalist and racing driver praised the sports seats, for example, as “surprisingly comfortable, as was evident after driving around a thousand kilometers in one go.”
The chassis design and noise level also surprised positively. He did not find the tighter suspension at all uncomfortable. As for the Carrera’s higher noise level, Frère even said that he only noticed it when he switched back to his own Porsche 911 S. Porsche did not expect more from a Carrera driver than from the driver of an early 911 S of the 2-liter era. And that was despite the fact that Frère was testing the Sport (or Lightweight) and not the more comfortable Touring version of the Carrera RS.
The RS was the first 911 to bring down its 0-62 mph time below 6 seconds. In the test, Frère achieved a truly fabulous time for 1973 with 5.8 seconds. However, the 911 S 2.4 was not far off with 6.6 seconds. The engine development was much more evident in the pulling power from low rev ranges. From 40 to 100 kph, the RS took a full 6.5 seconds off the S (10.6 to 17.1). At very high average speeds – the article mentions 220 kph cruising speed – the RS was also more economical. Its consumption of 17.2 liters per 100 kilometers was more than two liters below that of its more luxurious brother.
The Carrera pulls through quite powerfully even at 4000 rpm, so that you rarely need to downshift lower than 4th gear during brisk freeway journeys, whereas under the same circumstances in the 911 S 3rd gear often has to be used.Paul Frère on the differences in engine characteristics between Porsche 911 S 2.4 and Carrera RS
In addition, the 911 Carrera RS was also modestly priced at the time. Especially in view of the international competition. After all, tin-plated sheet metal for rust prevention and high quality workmanship were anything but a matter of course in sports car construction in 1973. Although the prices for comparably powerful sports cars were usually twice as high. The fact that the Carrera RS is today many times more expensive than the 911 S 2.4 is of course due to its historical significance and the rarity of only 1,580 models built. Even if the 911 S, with 5,054 units, was by no means a mass product.
Even though the Carrera RS Sport tends to be more popular (and more expensive) among collectors, the RS with Touring package is the better choice for many drivers. “In the Touring, the RS received the same equipment as its more sedate siblings 911 S”, Schwarz knows. Then, its weight was also similar to the S 2.4. You can recognize an RS Touring by the equipment code M472, which meant an extra DM 2,500 in 1973. With 1,308 units, they make up the majority of the production. Only 200 Carrera RS Sport with the M471 package were built.
Interestingly, the 911 Carrera RS Touring in particular makes a very confident driving impression. Comfort and usability are not only in no way inferior to the 911 S, the RS surpasses the S in every area. In addition to significantly more power in the mid-range, this impression also has to do with the aerodynamics and tires. As Paul Frère noted back in 1973, the wind-tunnel-developed front apron combined with the ducktail provided greatly improved driving stability. “You notice that very quickly, especially in crosswinds,” agrees Schwarz. The RS still had a certain built-in nervousness, but it was a bit more compliant on the road than the S. The one-inch wider rear wheels with 30-millimeter wider tires did the rest.
For these reasons, many 911 drivers retrofitted the distinctive ducktail. While this didn’t transform these cars into an RS, the difference was noticeable. The RS is not a completely separate model, but rather a carefully re-tweaked Porsche 911 S. At the time, Porsche was concerned that they would not be able to sell the 500 units required for homologation. But immediately after its presentation, it became clear how well such a car would be received on the market. The recipe of the 911, which can serve all segments from everyday sports car to Le Mans winner, still works today.
Heart and personal preferences play a bigger role than bare numbers or comparisons.Dr. Georg Konradsheim on comparing the Porsche 911 S and 911 Carrera RS
Of course, there’s no arguing away the fact that a Porsche 911 Carrera RS triggers even more emotions than a 911 S 2.4. But the fact that both belong to the same model family, are closely related, has a very big advantage, especially today. “These automotive treasures are usually driven very little today, certainly not at the limit. The differences between the S and RS can be felt and heard at all times, but a 911 S is still a wonderful car, of course! In addition, some people prefer the narrow, rear spoiler-less body,” Tobias Schwarz sums it up. But, as dealer Konradsheim also emphasizes, “Heart and personal preferences play a bigger role than bare figures or comparisons.”
The comprehensive Porsche 911 Carrera RS book by Dr. Georg Konradsheim and Dr. Thomas Gruber has long since achieved legendary status. It is often referred to as the “Carrera RS Bible”. The authors have compiled all the special features of the Carrera RS on 434 pages. The four-kilogram book is limited to 3,000 copies per language (de/en) and numbered. In addition to numerous previously unpublished photographs from the Porsche’s archive, it contains a complete register of all 1,580 RS ever produced.
You want to win your own copy of the Carrera RS book? Then take part in the competition! Answer the question correctly, register with the registration form, sign up to our newsletter and become part of the Elferspot family. In addition to the chance to win, as a registered Elferspot user you can also enjoy many other benefits in the future. The deadline for entries is Januar 29, 2023, 6 pm CET.
We wish all participants good luck. The winner will be informed by e-mail. If you don’t want to wait for your luck to run out, you can of course also find this great book in our >>shop.