EB Motorsport’s stunning Porsche 911 R homage
Hot on the heels of EB Motorsport’s stunning 911 R homage, the company’s Carrera RSR Turbo 2.1 replica is a Porsche passion project delivering many new historic race car components to market...
Words Dan Furr
Photography Chris Wallbank
RSR TURBO 2.1 EVEN BETTER THAN THE REAL THING
IMITATION GAME
Time with EB Motorsport’s RSR Turbo.
Cast your mind back to our hundredth issue and you’ll recall our showcase of EB Motorsport, a Yorkshire-based company specialising in the repair, restoration and tuning of air-cooled 911s. The keen-eyed among you will have noticed the RSR Turbo rear wing pictured in one of the many photographs we published. Although the complete car was hidden from view, the article’s words teased at the Carrera RSR Turbo 2.1 replica out of sight. “Our painstakingly accurate reproduction is based on R13, the car finishing second at the 1974 24 Hours of Le Mans, where it was driven by Gijs van Lennep and Herbert Müller,” revealed EB Motorsport coowner, Mark Bates.
“Our car has been engineered and manufactured to an exceptional level of detail, requiring thousands of hours of research by my dedicated team.” With these words still ringing in our ears, it made perfect sense for us to delve deep with a standalone Classic Porsche feature focusing on EB Motorsport’s extraordinary passion project.
This year marks the fiftieth anniversary of the G-series 911, meaning it has also been five decades since the 911 Turbo was unveiled. Prior to the series production 930 landing in Porsche dealer showrooms, however, the first turbocharged 911 was the Carrera RSR Turbo 2.1 race car, which also served as the first turbocharged 911 to compete at Le Mans. Only four examples of this phenomenally engineered Porsche were produced. Perhaps even more astonishing is how R13 (chassis 911- 460-9102), the final of the four RSR Turbos built, managed to survive its motorsport career and the subsequent decades without sustaining any serious damage or structural corrosion.
When it comes to performance road cars, Porsche and turbochargers proved themselves a perfect pairing, but it’s worth remembering the manufacturer’s success with turbocharging started at the race circuit. Specifically, one can chart Porsche’s experiments with snail-shaped bhp boosters to the 917, a sports prototype based on the 908 and developed to achieve top honours at Le Mans. Introduced in March 1969, the twelve-cylinder, 520bhp behemoth would go on to be revered as one of the most important race cars of all time.
In both short- and long-tail guise, the distinctively styled Porsche scored countless victories, not least the Stuttgart brand’s first overall triumph at Le Mans, a win scored in 1970 and considered Porsche’s most important motorsport success — it can be argued the Salzburgliveried, Herrmann-and-Attwood-driven racer kick-started Porsche’s incredible dominance of sports car racing. In fact, a magnesium-framed development of the 917 won at the following year’s daylong enduro at Sarthe, exactly twenty years on from the manufacturer’s first showing at the event. What is it people say about buses?!
Though the story hasn’t been widely publicised in recent years, the 917 held the lead for ninety percent of the 1969 event, one of the most exciting stagings of the 24 Hours of Le Mans to date. Sadly, thanks to transmission troubles, both works cars retired in the twenty-second hour of the race. The third 917, entered privately by John Woolfe, crashed on the opening lap, killing him in the process. This aweinspiring (if somewhat wayward) Porsche was clearly a force to be reckoned with and, as 1970 and 1971’s outings at Le Mans proved, was earning a reputation for being unbeatable, so much so motorsport’s governing bodies were twitching in their seats. Consequently, regulations were introduced favouring cars with engines possessing three litres of displacement (the smallest 917 engine was 4.5-litres), a move designed to entice manufacturers building three-litre Formula One engines to enter the world of endurance racing.
FRESH CHALLENGE
In response to the altered rulebook, Porsche focused its attention Stateside, entering the Canadian-American (Can-Am) Challenge Cup in 1972. With fewer rules than were being dished out in Europe, not to mention a lack of enforced limit on displacement, the 917’s Type 912/00 engine (named after the lowest-powered Porsche in production at the time of the 917’s introduction, a move rumoured to be a way of disguising the true nature of the beast) grew to 5.4-litres, with power output of 660bhp. This was, however, was just the start.
Porsche engineers, Hans Mezger and Valentin Schäffer, developed a sixteen-cylinder version of the engine producing 760bhp, but the host 917’s chassis had to be extended to accommodate such a massive powerplant, which negatively affected the car’s handling. A turbocharged twelve-cylinder engine was subsequently developed under the watchful eye of factory motorsport chief, Ferdinand Piëch, and head engineer, Helmuth Bott.
This wasn’t the first time Porsche had looked to turbochargers for extra ‘get up and go’. Ferdinand Porsche had, in fact, bolted turbochargers onto sixteen-cylinder diesel-fed tank engines many years beforehand. Even so, the twelve-cylinder 917 represented the first time the sports car manufacturer bearing his family name had used a turbocharger to achieve truly prodigious performance. Initial results, however, were poor. Massive, uncontrollable boost, plus the very real danger of mechanical failure causing a fire, gave cause for concern. These teething problems were solved by diverting unwanted gas through a wastegate, enabling the Penske Racing 917/10 short-tail to take Can-Am spoils with 850bhp at its disposal, breaking McLaren’s five-year dominance of the competition as it did so.
Powered by a 1,580bhp flat-twelve, the 917/30 of 1973 was a revelation. Driven by Daytona and Indianapolis stalwart, Mark Donohue, it decimated the competition. The year’s global oil crisis, resulting from the Organization of Arab Petroleum Exporting Countries (OAPEC) implementing a complete oil embargo against countries supporting Israel during the Yom Kippur War, encouraged series organisers to introduce a limit to the amount of fuel expended by participating cars. Additionally, there was real concern about excess levels of combustible gas leading to exploding fuel cells. The change pretty much outlawed the 917/30 for the 1974 season, although various privateer teams backdated their 917s with normally aspirated engines in a desperate bid to qualify for inclusion in a series McLaren had quit in favour of renewed focus on Formula One and the Indy 500.
Porsche had ably demonstrated its ability to harness and refine turbocharging technology. Indeed, the 917/30 was the most powerful sports racing car ever produced, delivering 1,369.68bhp per tonne. The 917/10, meanwhile, won the 1973 European Interserie. There was, however, uneasy talk in Zuffenhausen’s corridors — members of Porsche’s executive board were worried about the spiralling costs of the company’s motorsport programme and also the fact showroom customers were increasingly unable to make the connection between what the manufacturer was doing on the track and the products it was offering in dealerships. The FIA’s altered Group 5 racing rules mirrored Group 6 prototype regulations insofar as engines were limited to three litres of displacement, but also by requiring no minimum series production for homologation of competing cars. In light of the 917 living on borrowed time, Porsche’s then CEO, Ernst Fuhrmann, decided to reintroduce the 911 to top-tier sports car racing. The result was the Carrera RSR Turbo 2.1, a cutting-edge 911 combining all of Porsche’s engineering and turbocharging know-how in a giant-killing package. “The precursor to the 934 and 935. A road car capable of beating the most most advanced prototypes of the era,” as Mark succinctly describes it. Fuhrmann saw it as a means of assisting with the development and marketing of the 930 road car in advance of its planned launch for the 1975 model year.
The revised Group 5 rules had the effect of pitching the RSR Turbo in with prototypes, including the V12-powered Matra-Simca MS670C, but Porsche was supremely confident in its new racer, which shared much of the G-series road car’s silhouette, but carried over many parts from the outgoing 917. “A staggering amount of development work, which is why it took so long for us to build a faithful replica,” Mark gasps. In order to encourage a level playing field with normally aspirated cars on the grid, the FIA applied a multiplication factor of 1.4 to the displacement of turbocharged engines, hence the use of a 2.1-litre flat-six in a category permitting up to three litres of cubic capacity.
At first glance, the RSR Turbo looked much like the earlier Group 4 Carrera RSR, a consequence of both models wearing silver paintwork and Martini Racing livery, but tell-tale signs of the later 911’s identity were there for all to see. The RSR Turbo’s massive rear wing, for example, replaced the ‘Mary Stuart’ adornment on the back of RSR, while intake ducts housed in solid panels appeared in place of the rear side windows. Interestingly, this same design has been applied to the recently launched 718 Cayman GT4 RS.
SHAPES AND SIZES
The RSR Turbo was also noticeably wider than what came before, despite being one of the lightest 911s manufactured. Tipping scales at a mere 820kg, the car made use of fibreglass body panels, polycarbonate windows and a reprofiled rear screen angle designed to optimise airflow toward the ‘ironing board’ rear wing and intercooler, the latter linked to a flat-six making use of various components from the Porsche parts bin, including a 908-sourced oil cooler.
A lone KKK turbocharger and mechanical fuel injection helped the 2,142cc magnesium-cased boxer to realise 500bhp near 7,600rpm. As you’d expect, uprated camshafts and forged internals (including aluminium pistons and titanium connecting rods working together inside Nikasil-coated liners) were key ingredients, but less known is the fact Porsche mounted the engine’s cooling fan horizontally, a move intended to promote increased airflow around a decidedly cramped engine bay.
The late-specification 917’s locked axle joined a Type 915 gearbox and an RSR clutch, while the fuel cell was relocated from the front of the car to the cabin. The part was shaped to occupy the space occupied by rear seats in a standard 911, as well as the void where the passenger seat would normally reside. The shape and positioning of the tank was designed as a response to the car’s constantly reducing in-race weight (due to fuel usage) and a desire for it not to have a negative impact on the car’s driving characteristics. The RSR Turbo’s weight was therefore heavily biased toward the rear.
Independent suspension in all four corners comprised Bilstein coilovers and titanium springs, complemented by adjustable anti-roll bars. The RSR Turbo’s brakes were a carryover from the RSR, as were the instantly recognisable five-spoke wheels. Both sets of equipment could trace their origins to the 917. Speaking of which, at Le Mans, the RSR Turbo was able to reach more than 186mph, accelerating from rest to 62mph in little more than three seconds, the result of bucketloads of torque and the sheer thump of forced induction working its magic on the formidable flatsix. The 935 would, of course, go on to steal the limelight, but not before R13’s star turn at Le Mans in June 1974, where Müller and van Lennep covered 332 laps, pipped to the post by Henri Pescarolo and Gérard Larrousse’s Matra after starting seventh on the grid. The next-placed Porsche (a privateer RSR driven by Bernard Chenevière, Peter Zbinden and Michel Dubois) finished seventh. Considering R13 lost the use of fifth gear during the race, its podium finish is especially impressive.
As the works entry for the 1974 World Championship for Makes, R13 contested not only Le Mans, but also the year’s six-hour race at Watkins Glen, held a month later. Starting from fourth on the grid, Müller and van Lennep worked together to achieve a second-place finish, before going on to contest the Le Castellet 1,000km (seventh overall) in August and the 1,000km of Brands Hatch (a fifth-place finish from tenth on the grid) in September. This was a time when Porsche saw little value in keeping what it regarded as obsolete race cars, meaning R13 — along with a further two of the four RSR Turbos — was sold into private ownership. Thereafter, the car was driven by Danny Ongais, George Follmer and Ted Field under the Interscope banner for the 1977 24 Hours of Daytona (generating a regrettable DNF thanks to a failed piston, despite a promising start from sixth on the grid) and took part in the same year’s Mid-Ohio three-hour race, where Follmer shared driving duties with Howdy Holmes for Vasek Polak Racing.
Fast-forward to the present day, and R13 is a true survivor. Returned to Martini Racing livery, the car was offered at Gooding & Company’s 2018 Amelia Island auction with a price reflecting its status as one of the most important Porsche motorsport machines in existence. As we now know, the lower estimate of six million dollars proved too punchy, resulting in the car failing to sell. We won’t shed a tear — its subsequent transportation for work at a historic Porsche motorsport specialist in the UK gave Mark and his team the opportunity to eyeball every inch of the car in pursuit of his dream of creating an entirely faithful RSR Turbo replica. We should state, we’re not talking about looks alone — every component on the car you see in our photographs has been faithfully reproduced in exacting detail and, almost without exception, makes use of materials to match Porsche’s efforts in period.
Even with EB Motorsport’s unrivalled component tooling and manufacturing capabilities taken into consideration, this was no easy task. Remember, there were only four RSR Turbos produced, and three of the quartet were sold into private ownership, whereupon they were subjected to alterations not limited to livery — in years subsequent to Porsche releasing the cars to pastures new, changes to racing regulations encouraged updated vehicle specification. In other words, even with sympathetic restoration in recognition of today’s historic motorsport events, it is difficult to tell whether a former works race car is configured entirely as it was when new. The main thing to consider is the fact an RSR Turbo looks like a 911, but is almost entirely different beneath the skin. “The suspension pick-up points are at odds with the 911 road car,” Mark shrugs. “The half shafts are manufactured from titanium. There’s a specialist fuel pump at play. The steering column is aluminium with a titanium shaft. The floorpan is different. Lot of parts were taken from Porsche’s prototype racers — you can’t really describe any of it as standard equipment.” So great was the challenge in building a facsimile of an original RSR Turbo, Mark was told not to bother by renowned Porsche engineer and former works racing driver, Jürgen Barth. “He said there simply wasn’t enough information available in the public domain for anyone to build an RSR Turbo replica capable of securing an FIA Historic Technical Passport and therefore conforming to the organisation’s requirements for historic racing, which was always the goal of this project.”
LAYING FOUNDATIONS
The EB Motorsport team’s skill and determination had already been put to the test during the build of the company’s celebrated 911 R homage. As we described in the aforementioned earlier issue of Classic Porsche, this ambitious project marked the fiftieth anniversary of the 911 R’s record-breaking 20,000km endurance run, where the model clocked average speed of 209km/h in Monza, Italy. “We started with a short-wheelbase 911 from 1967, the year of the 911 R’s famous sprint,” Mark confirms. “The car was a real mess when we received it in 2013. It was riddled with corrosion and almost beyond saving, but across the course of four years, our in-house team carried out a fastidious restoration.”
Loaded with hand-finished details, from bespoke braking components and 906-style inlet manifolds, to the firm’s own lightweight doors, wheel arches, bumpers and exhaust system, development of the 804kg EB Motorsport 911 R necessitated the production of many unique components, which were swiftly added to the company’s parts catalogue. In doing so, Mark and James were allowing other passionate Porschephiles to build their own interpretations of this most legendary of 911s. “It took an exceptionally long time to research, source, design and fabricate all the parts we needed to build a faithful replica,” Mark highlights. “Luckily, we had a customer who owned an original 911 R. We spent many months exchanging information about the details of various components. These conversations allowed us to create new parts matching period specification.” The RSR Turbo project, however, was on another level altogether. “I was adamant every part of the car needed to be an exact match for its corresponding original component. Every titanium fastener, for example, had to be a perfect clone of a factory part. Obviously, this meant we had to build a big knowledge base.”
Referencing period documentation and thousands of photographs, as well as having conversations with Porsche engineers and racing drivers associated with the RSR Turbo when new, yielded much of what the team required, but access to R13 was by far and away the most valuable resource at Mark’s disposal. “The car moved into a private collection, which I had a route into,” he explains. “This gave my team the opportunity to spend hundreds of hours profiling every millimetre of a genuine RSR Turbo, thereby allowing us to create accurate exterior panels for the replica. That said, it took us a year to finalise our 911’s bodywork. You have to understand, we need to manufacture the tooling required to make the parts before we can begin production. All the while, we have customer projects on the go.”
It took two years just to find a period-correct turbocharger to work with. The calipers were another crucial component for the team to get right. Based on the 917’s original cast calipers, they were reshaped for RSR Turbo usage, holding a deeper pad with more friction material. Cooling fins were oriented transversely (rather than vertically), making them a part easily recognisable, but complicated to replicate. “Casting can be unreliable and produces much in the way of wastage,” Mark explains. “This is why, to produce our version of this particular 917 caliper, we used state-of-the-art software to accommodate scanning, digitisation and design processes before the final part was made from a solid billet of aluminium in a five-axis CNC machine overseen by a skilled operator.”
To complement the billet bodies, EB Motorsport machined caliper pistons from aluminium, while the rest of the fixtures and fittings, such as the crossover pipes and bleed nipples, are machined from solid titanium. The company even makes its own handbrake mechanisms and brake pads. “Of course, making a part complying with FIA regulations is one thing, but having it look period-correct is another. In the example of the calipers, we had to give them the appearance of the original cast items to ensure they didn’t look out of place when fitted to the car.”
The rear wing presented a challenge of its own. “It’s huge,” Mark laughs. “We designed it in CAD software, but on account of its size, we needed to seek the assistance of a film set manufacturer to help bring the blueprint to life. We couldn’t remove parts from R13, which is why it was vital our reference points were spot-on.”
The car’s rear trailing arms are aluminium. Moreover, with the help of a Celette jig, the entire rear suspension ‘horseshoe’ comprises lightweight tubework. “The sheet metal fabrication on the original RSR Turbo is staggering, but we’ve replicated all of it,” Mark stresses. Parts deviating from original specification are few and far between, but include the roll cage — in the interests of driver safety, the EB Motorsport replica’s roll cage is manufactured from T45 steel tube, whereas R13 would have been equipped with a softer aluminium cage.
“It would be very difficult to complete a project of this magnitude without the ability to design, tool and fabricate parts in-house,” Mark concedes, referencing engine items not limited to the RSR Turbo’s cylinder heads, valve guides and camshafts, all of which were perfectly replicated for this build. Even the car’s paintwork is period-perfect, a result of Mark sampling colour from an unrestored RSR body panel and mixing the exact same shade of silver, which was applied by way of the two-stage base-and-lacquer process adopted by the works team in the early 1970s. This dedication to accuracy extends to the shifter mechanism, the specialist gear set, the ‘flat’ engine fan (“a big project in its own right”), driveshafts, dash dials, all of it. “I began to wonder if Jürgen Barth was right,” Mark smiles. “The amount of time and energy we have invested in this project is huge. Much of it has been dedicated to research. Barth was correct insofar as there is very little information available relating to the RSR Turbo’s original specification. Worse still, much of the data we came across is incorrect. Fortunately, we were involved in the restoration of a 936, which helped us reverse-engineer parts used in RSR Turbo production, thereby allowing us to observe correct designs and tolerances. Even so, this was no easy build.”
The door handles might look metal, but they’re plastic, just as they were on R13 and its siblings. “We had to scan and reproduce the original parts, including the push button mechanism,” Mark reveals. “The light lenses are standard, but the bowls are custom. The steering rack isn’t anything unusual, but it mounts to the monocoque. You can’t just go to a Porsche Centre and buy the required parts. They have to be made from scratch.” This is a good point well made — owners of historic racing Porsches, as well as enthusiasts building replicas, have long struggled to find parts for repair or appointment, but EB Motorsport projects, such as this, introduce brand-new componentry to market. Not that this amazing replica is a moneymaking tool for the business. “We might cover the costs of some of our tooling production, but we built this car to go racing in 2024, the occasion of the RSR Turbo’s fiftieth anniversary,” Mark confirms. “I’m really looking forward to getting behind the wheel.”
You can, too. Yes, really! There aren’t enough pages in a single issue of Classic Porsche to fully document the extent of work invested in this spectacular Porsche project, but a limited number of EB Motorsport RSR Turbo recreations are available to order and will be delivered ready to race, meaning Mark and his team are happy to chat to interested parties wanting to acquire an RSR Turbo to call their own. And in case you need further convincing of the attention to detail lavished on the 911 you see on these pages, consider the fact Gijs van Lennep, the man who drove multiple RSR Turbos in 1974, including R13 at Le Mans, thought he was looking at the real deal when he examined our star car at a show last year. EB Motorsport, we salute you.
Top right Horizontally mounted fan was a big project in its own right Right A film set manufacturer was enlisted to help with creation of the rear wing Below No fuel tank up front leaves enough space for storing your race suit.
A LIMITED NUMBER OF RSR TURBO RECREATIONS ARE AVAILABLE TO ORDER AND WILL BE DELIVERED READY TO RACE
Above RSR Turbo’s release into the wild coincided with launch of the 911 Turbo road car, allowing Porsche customers to make a direct connection between what they were seeing in showrooms and what Porsche was campaigning on the world’s race circuits.
Above and below The fourth of the quartet of original RSR Turbos built (R13, the example finishing second at the 1974 24 Hours of Le Mans) was used as a point of reference for EB Motorsport’s ambitious Porsche project.
HAND-FINISHED DETAILS, FROM BESPOKE BRAKING COMPONENTS AND 906-STYLE INLET MANIFOLDS, TO THE FIRM’S OWN DOORS
Above Thousands of hours of research and development have been invested in bringing the car to fruition, work resulting in bringing a selection of previously unavailable historic 911 race car components to market.
Above Fuel cell was moved from the ‘frunk’ to the cabin, taking up the space usually afforded to the rear pews and front passenger seat. Below Additional intakes can be seen in place of rear side windows, a design inherited by the 718 Cayman GT4 RS.
THE RSR TURBO WAS NOTICEABLY WIDER THAN WHAT CAME BEFORE, DESPITE BEING ONE OF THE LIGHTEST 911s MANUFACTURED
Above RSR Turbo rear windscreen angle was altered to help channel air to the massive rear wing and to the intercooler below it. Facing page Martini body graphics are a perfect replication of original decals, a level of accuracy not even original RSR Turbos are necessarily sporting.