The History Of Porsche’s Production Racing Turbos, the 934 and 935
By Bill Oursler for 962.com
The history of Porsche's production racing turbos, the 934 and 935, actually
begins in the latter part of the 1960's when the Paris-based Federation
International de L'Automobile, the FIA changes the formula for its World
Manufacturers championship, outlawing unlimited displacement engines for
its prototype category by placing a Three-Liter cap on all such power
plants from 1968 onwards
The trouble with this equation was the fact that while it might have met the needs of the French, it didn't inspire much, much if any enthusiasm elsewhere. The decline in interest from other manufacturers, as well as fans, sponsors and promoters was dramatic, so much so that by 1973 the FIA decided to replace the custom-built Three-Liter prototypes, with dramatically altered production-based vehicles, this switch being originally scheduled to take place in 1975, but later deferred to 1976 instead.
These new prototypes were to be run under the new so-called Group 5, or "silhouette" regulations, the existing production-car division, Group 4, being retained, but with recrafted scriptures which greatly limited the number of modifications which could be made to the base automobile so that the silhouette entries would not be outshone by their lesser brethren. While a number of major manufacturers expressed an interest, for one the FIA's proposals were particularly interesting.
That company was Porsche, which in 1973 had introduced at the Frankfurt Auto Show what would become its 911-based 930 street turbo. Porsche's new president, Ernst Fuhrmann was dedicated at that time to exploiting the potential of the 911 in quest of new sales. This took two forms, a renovation of the 911's design, and a new emphasis on it as a racing contender.
To that end, Fuhrmann had transferred one of the companies's most promising competition engineers, Norbert Singer from the factory's 917 Can-Am program to work on the transformation of the 911 into a motorsport powerhouse. That was in the summer of 1972. By the next year's Daytona 24-Hour season opener, Singer's efforts, in the form of the Carrera RS/RSR were ready for public display. In fact, Singer's Carrera performed so well at Daytona that it won overall in a portent of things to come.
Indeed, the Carreras, first in the abbreviated "ducktail" form, and later with new "whaletail" rear spoilers attached, would dominate the GT scene throughout the world between 1973 and 1976, collecting no less than three straight IMSA Camel GT crowns and an equal number of FIA and German titles as well during that period. Even after the introduction of the turbos in 1976 the Carrera continued to win, especially in North America.
However, from the summer of 1973, Singer and his team would be occupied with the development of Zuffenhausen's boosted 911s. It was an effort that would start with the experimental Turbo Carrera of 1974, a car that was strictly a "proof of concept" prototype which utilized the basic 1974 Carrera shell fitted with a 2.14-liter fuel injected six cylinder turbocharged unit derived from the boosted Can-Am 917 12 project.
Because the car (in all four were made) was not a "production" model, it was forced to race as a prototype against the purpose designed Three-Liter sports racers which normally populated the category. Even though handicapped by its ungainly aerodynamics and weight, the 911-based car did extremely well for itself, winning the special three-hour Le Mans Test Weekend event, and later finishing an excellent second overall in the 24-Hour classic itself.
Although much of the cost of running the turbo Carrera had been defrayed by sponsorship from Martini, the experimental coupes were not raced again, even though the FIA had pushed back the introduction of the new Group 5 "silhouette" formula a year from 1975 to 1976. Rather, Singer and his engineers stayed at home working on the first of the new 935's, while at the same time perfecting its less potent sibling, the Group 4 934, which was intended for Porsche'' customers.
At first the 935 did not look much different from the standard, non-turbo Carrera RSR's, then dominating the GT ranks throughout the world. Only a new wing at the rear, a compromise really between the RSR's normal whale tail spoiler and the device fitted to the '74 Turbo Carrara separated it visually from its more mundane predecessor. But, that would change.
Meanwhile, beneath its still rather bland exterior, the 935, with the exception of a new four-speed transaxle, rather than the five-speed unit utilized in 1974, featured much of the '74 Turbo's mechanical philosophy, including its coilover suspension, full cockpit rollcage and separate "X-Member" stiffing frame that fitted between the inner front bodyshell sheet metal, both the cage and the frame being made from aluminum alloy. Also included in the package were the 917's ventilated, crossed-drilled disc brakes, the same as utilized by the 934.
The wheels for the 935 were a departure from what had been previously employed by Porsche, the fronts being 16 inches in diameter with a width of 12.5 inches, while the rears were 19 inches in diameter and 15 inches in width. The reason for the use on differing diameters was the fact that the 935's 2.9-liter turbo six pumped out a conservative 650 horsepower, this figure requiring all the grip, which could be found.
The low profile Dunlop tires fitted to the unique rear rims did just that, the large diameter wheels helping the tire to create a greater contact patch during cornering. In fact, there are many who feel that if the truth were told, the actual output of the 935's six was far closer to 750 HP that it was the lower figure, a fact which made the amount of grip even more critical. In large measure, the engine's grunt came from both its dual ignition system, as well as its air-to-air intercooler.
In the end, troubles with the rules makers over the latter would nearly cost Zuffenhausen the World Manufacturers crown for 1976; the squabble occurring after Singer found a loophole which permitted him to radically alter the car's profile. What his reading of the regulations disclosed was hat the FIA had unintentionally allowed designers to create any fender shape they wanted when the organization had crafted its scriptures dealing with fender flares.
Said the FIA "the shape of the fenders is free," when it really meant to say that only the shape of the flares themselves was free. Thus came into being the first of the famous "slope nose" Porsche as Singer cut away the tops of the fenders to match the angle of the hood so as to crease downforce at the front which the car badly needed. When the FIA saw what Singer had done (the headlights now being located in the bumper), it stammered and threatened, but could find no way to counteract Singer's interpretation of the rules.
Indeed, over the next several years, the Porsche man would, as John Bishop, president of the International Motor Sports Association, described it, "pervert" what the FIA had intended the silhouette formula to be. At the time, however, the FIA attacked not at the front, but at the rear, claiming that the engine cover shape, which had to remain identical to that of the 930, had been ever so slightly modified in order to accommodate the intercooler.
As a result, Singer and his engineers had to redesign the car to replace the air-to-air unit, with a far less efficient, and, in the beginning, far less reliable air-to-water alternative that took until the final to races of the year to sort out. With reliability restored and victories in those final two rounds in its pocket, Porsche achieved what it had set out to do: claim the FIA World Manufacturers crown in the opening chapter of a story which would continue until 1984, some eight years further in the future.
Interestingly, the factory had kept the 935 for itself during 1976 (although it did provide its 934 customers with "kits" that could almost, but not quite transform the group 4 entries into duplicate's of its Group 5 turbos). For 1977 that would change as Porsche sold replicas of the single turbo '76 season 935s to those of its customers who wanted them. Of course, for itself, the factory had developed something better: the twin turbo 935-77.
While the basic drive train, from the '76 factory cars, including the
four-speed gearbox and 2.9-liter engine were carried over, the water-based
cooler system was modified for better efficiency, being moved to the rear
of the engine compartment. This change could be made because the rules
dealing with the car's structure had been re-interpreted to mean that
the chassis was that part of the car between the front and rear bulkheads
of the cockpit area.
The FIA also allowed the floor pan of the passenger compartment to be raised by three inches, this latter clearance for the cumbersome exhaust systems associated with turbocharged front engined vehicles such as those from BMW and Ford. Interestingly, Singer did not take full advantage of the sanctioning body's largess with the 935-77; rather he chose to refine the factory entry's aerodynamics instead. What appeared as a result was a Porsche turbo whose wind tunnel sculpted lines bore only a passing resemblance to the street 930.
Once again Singer had done his homework, for in profile, the 935-77's roof was far flatter than that of other 911-based cars. By flattening the roofline, Singer and his people had improved the airflow to, and thus the efficiency of the rear wing. Moreover, it was all legal because the "new roof" was actually an "add-on" aerodynamic device, which fitted over the original sheetmetal underneath. Once again the wording of the FIA's scriptures was critical for it allowed any such device as long as it could not be detected when viewed from the front of the vehicle, which Singer's second roof was most certainly not.
Two years later the Kremer brothers would use the same loophole to create the own 935 K3 design, whose roof line was, if anything, more radical than that of the 935-77.Once more, using the 935-77, the factory cleaned house, winning its second consecutive Manufacturers crown, although this time it did so with the assistance of its customers, whose less potent 1976 935 factory replicas (officially designated 935/77A's) generally ran behind the factory's Martini-sponsored entries.
In fact, the customers, other than their record in the FIA World Championship, were doing quite well for themselves, particularly in the Group 4 category, were despite its less than excellent handling qualities, the 934 was nearly unbeatable no matter where it raced. And, therein can be found the salvation of the of the Sports Car Club of America's Trans-Am.
By 1976, the venerable series was destined for extinction as John Bishop's IMSA organization and its popular Camel GT series had taken over as the top road racing championship in North America. However, Bishop, who had a love-hate relationship with Porsche, was wary of the new Porsche turbos, fearing that even the less potent 934 would dominate his universe, as had so many other Zuffenhausen products before it.
After first giving his approval for the 934 to run in the 1976 Camel GT, Bishop at the last minute changed his mind, a barred it from IMSA, leaving Porsche and its North American racing boss, Josef Hoppen with a number of brand new cars and no place to race them. There ever resourceful Hoppen, however, quickly convinced the SCCA to reformat its Trans-Am to include the 934s, whose presence not only saved the series, but garnered George Follmer his second Trans-Am crown behind the wheel of a Vasek Polak owned 934.
Porsche would win the Trans-Am twice more before the regulations were revised to exclude the turbos at the end of the 1979 season, Canadian Ludwig Heimrath taking the honors with his much modified 934 in 1977, and John Paul, Sr. doing the same with his single turbo 935 in '79, Meanwhile, Bishop realizing he had made a mistake permitted the 934 to race in his series, starting in August, 1976. Unfortunately, the narrow-tired car proved uncompetitve, leading Porsche and Hoppen to lobby for more latitude in 1977.
What emerged from those efforts was what is had come to be known as the 934/935, a uniquely North American creation which added the 935's tail, rear fenders and tires to the basic 934 body and drive-train. The result was highly competitive, Porsche narrowly losing the Camel GT to Al Holbert's domestic, tubeframed Chevrolet Monza by the tightest of margins. Ironically,
Porsche might have done better if Peter Gregg had run the championship, but "Peck's Bad Boy" had run afoul of the stipulation between Hoppen and Bishop which said that the 934's had to race as they were delivered in their hybrid configuration. Gregg, who had added a full 935 suspension to his example, took his team to the Trans-Am were he was fully welcomed by all except Heimrath who got the Jacksonville driver disqualified from the combined Mosport FIA Six-Hour/Trans Am round, and thus came away with the SCCA title.
The 934 would soon fade into relative obscurity as Bishop's series sponsor successfully pressured him to allow the 935 to compete in the IMSA title chase in 1978, the SCCA likewise allowing the Group 5 car to run in the Trans-Am. Although visually similar to their 1977 counterparts, the 1978 customer 935s sported a twin turbo 3.2-liter engine with slightly revised rear fenders, still carrying their water-based intercoolers.
By this time, there was little effective opposition for the 935, the car winning essentially whenever it appeared, including the FIA World Makes Tour, as well as the German National championship and the Camel GT. Indeed, about the only major series the Porsche didn't capture was he Trans Am which went to the Corvette camp/ In Europe the top operation was that of George Loos, while in the United States, it was Gregg, along with his sometimes partner, Hurley Haywood who prevailed with his immaculate Brumos 935.
For the most part, the Porsche factory was content to let its customers carry its flag. Still, Singer had one new surprise to spring on the world, which would eventually have a profound effect on the 935 era. When last seen, Singer had been busy with the 935-77. In the late spring of that year, while Porsche was preparing for Le Mans, company head Ernst Fuhrmann decided the factory needed to compete against Ford and BMW in the 1.5-liter German National Championship division to counter the exposure those manufacturers were getting there.
What Singer's engineers produced in response was the "Baby" 935, which from the outside appeared little more than a revised 935-77 without a front oil cooler and much more narrow tires, Underneath, though, Singer took the opportunity to utilize the largess of the revised Group 5 rules by using from and rear tubular subframes in place the original inner body sheetmetal. "Baby would race only twice in the hands of Jacky Ickx, losing the first time out, but winning in its second appearance.
It was little more than a diversion for Zuffenhausen. Yet, the technology found in "Baby" would reappear in 1978 when Singer unleashed the 935-78, better known as "Moby Dick" for its unique elongated tail section. In actuality, there was very little about Moby Dick that wasn't unique. For one thing, Singer based the car on a right-hand drive 911 the first time that had been done, for another he lowered the bodyshell around the floor plan by the permitted three inches. However, the really important new feature was the fact that Singer tied together the front and rear subframes with the central rollcage structure to form a full tubeframe chassis.
In fact, about the only remaining stock 811 bodyparts were the roof, the windshield and cowl area, as well as the rear quarter windows and door jams. After that it was all pure race car. Even the doors themselves were modified, being covered in new outside shells that bonded them together with the front and rear fenders. (Although, the FIA later forced Porsche to rework this feature so that when Moby Dick finally appeared, only the front half of the doors remained covered.)
Once more the fiberglass nose was changed, becoming elongated like the tail, while the outer roof covering was simplified from that of the previous year's factory entry. Mechanically, the 935-78 remained unchanged except in one important area: the engine compartment. There a new 3.2-liter water cooled head powerplant was to be founds, this in response to the number of piston failures suffered the previous year both by Porsche with its winning 936 sports racing prototype as well as its Renault Alpine rivals. The hope being that the lower cylinder head temperatures were cure the problem.
Of all the enduring features found in Moby Dick, its legacy is probably best expressed in this engine, which in modified form powered the revised 936 spyders which first appeared at Le Mans in 1978, and which would go onto to make the 956/962 prototypes so successful with the addition of an motoronic ignition system. Indeed, it was this same unit which was envisaged for Porsche's first aborted assault on Indianapolis in 1980.
Ironically, despite all the effort that went into it, the 935-78 achieved little, other than winning its inaugural event, the Six-Hour Silverstone Makes round in May. While it did finish at Le Mans, it did so out of the top five, coming home eighth overall after being slowed by a suspected oil leak, As for its other two appearances, the Norisring German Championship round, and the FIA Vallelunga Six Hours, it dropped out in both.
Even so, Moby Dick's place in history is secured as progenitor for a host of similar Porsche 935's, two of which JR 001 and JR 002 were duplicates built by Reinhold Joest with Porsche support, the former being eventually purchased by Dr. Gianpiero Moretti, and the latter by John Fitzpatrick. Moretti's example which had been run briefly by Joest in German, where it won at Hockenheim, had a long career in IMSA, posting a number of top five successes,
As for Fitzpatrick's JR002, its life was much shorter, although it won its class at Le Mans in 1982. Unfortunately, it was destroyed in an accident in the Riverside Camel GT affair the following April, Rolf Stommelen being killed in the mishap after the engine cover and rear wing ripped off at high speed. Uniquely, Fitzpatrick's car had the original full length door coverings, while Moretti's had no coverings at all. Both chassis were powered by the IMSA "standard" 3.2-liter all air-cooled boxer six.
Inspired by the Moby Dick's design was the Kremer brothers K4 935, this being a follow-up to their K3, which in itself was inspired by the factory 935-77. Like that car, the K3 gestured a second, flatter fiberglass roof, as well a fenders with deep wing fences to better control the airflow over them. While these aids were important, the heart of the K3 was its use of an air-to-air intercooler like that found in the first factory 935. While in terms of absolute power there wasn't much difference in terms of the intercoolers used, the air-to-air example was far more efficient at keeping temperatures down and thus power up over the long haul. To say that the K3 was most likely the most successful of the 935 variants would be an understatement, the car winning the FIA and IMSA championships, as well as numerous other individual events. Still, its most triumphant moment came when in the hands of Klaus Ludwig and the Whittington brothers, Don and Bill it won Le Mans outright in 1979.
Somewhat less successful by comparison, was the later K4, although Fitzpatrick and Frenchman Bob Wollek employed it to garner a number of victories and at least one national championship. Likewise successful, but not as much so as the K3 was the Joest built 935J, a car whose design was based on that of the 935-77 factory machine. Among other things, this version claimed the German season title, as well as wins at Daytona and Sebring. Indeed, it was one of these cars which score the last 935 major win at the 1984 Sebring 12-Hour.
Meanwhile Moby Dick inspired several Americans to copy it in varying degrees, the most notable of which was built by the Andial company in Southern California in 182 for Howard Meister, who later sold it to Floridian Preston Henn. Under Henn's care with Wollek, Claude Bollot-Lena and A.J. Foyt driving, it won the 21 Hours of Daytona in 1863, placing second in the race a year later. It also won a sprint at Daytona in July '83, again with Foyt aboard.
One other North American shop heavily into creating its own 935's was Dave Klym's Fabcar operation then located in the Atlanta, Georgia area. In 1982 Klym constructed a full tubeframe 935 for John Paul, Jr., who used it to help him garner the '82 IMSA Camel GT drivers honors. While the car scored on a single victory in his hands, that coming at Brainerd, Minn., its advanced technology remains impressive to this day. Also designed and built by Klym was Bob Akin's 035-84, generally conceded to be the last of the breed to see action on the track.
This car was a replacement for the ill handling monocoque 935 Akin had constructed for his team in 1987, and which was permanently put of its misery following an accident at Daytona in the fall of that year, happily without injury to driver Derek Bell. Again a tubeframe vehicle, the 935 was perhaps the best looking, and one of the best performing 935's to be created., Still, while it nearly won its debut event at Daytona in the fall of 1983, and while it had a number of top ten finishes the following season, it was too late to make much of a statistical impression, being replaced as Akin's primary vehicle in the spring of 1984.
Before ending the 935 story, there are two other cars which need to be mentioned these were built at the factor in 1980 and featured 935-77 style bodywork, one going to Bruce Leven's Bayside Disposateam, and the other to Peter Gregg. Leven's car, delivered early in the year had the distinction of winning Sebring with Leven, Hurley Haywood and Al Holbert driving. It was destroyed by fire that summer at Sears Point when Haywood spun off into the dry grass which lit off before any firefights could arrive on the scene.
The Gregg car was not completed until the fall and was practiced at Daytona by him who withdrew it after he discovered it didn't like the way it handled. After Gregg committed suicide a month later, his estate sold the car to Leven who had indifferent luck with it.
In all, the 935's career lasted from 1976 until 1984, although some were
raced long after that. In later years, during the 1990's Singer and his
engineers revisited the 935 equation, using it to create the 911 GT2 and
911 GT1 turbos, which, like their famous predecessors, carved out a stunning
record for themselves in the sport. Today, the 935 brigade lives on in
historic racing garnering attention from whole set of enthusiasts who
will kept it and its legend alive for decades to come..
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