Mercedes-Benz 450SEL 6.9

The Mercedes-Benz 450SEL 6.9 was a high-performance version of the S-Class luxury sedan. It was built on its own assembly line by Daimler-Benz AG (now DaimlerChrysler) in Stuttgart and based on the long-wheelbase version of the "W116" chassis introduced in 1973. The model was generally referred to in the company's literature as the "6.9", to separate it from the regular 450SEL. It was first shown to the motoring press at the Geneva Auto Show in 1974, and produced between 1975 and 1981 in extremely limited numbers. It was billed as the flagship of the Mercedes-Benz car line, and the successor to Mercedes-Benz's original high-performance sedan, the 300SEL 6.3. The 6.9 also has the distinction of being among the first vehicles ever with optional anti-lock brakes, first introduced by Mercedes-Benz and Bosch in 1978.

Special features

Although the 6.9 was visually and for the most part mechanically identical to other W116-based cars, the similarity ended at the body shell. Beneath the hood was the largest postwar engine yet installed in a Mercedes-Benz. It was an enlarged version of the Mercedes-Benz model M-100 engine that first saw duty in 1963 in the hand-built and ultra-expensive 600 or Grosser (Grand) Mercedes and in 1966 in the aforementioned 6.3. The 6.9 was also the first Mercedes-Benz to be fitted with the company's new hydropneumatic suspension system, unlike the 600 and 6.3 which employed air suspensions. The system was similar to one previously developed by Citroën. Using a combination of fluid-filled struts and nitrogen-filled pressure vessels or "accumulators" in lieu of conventional shock absorbers and springs, the system was pressurized by a hydraulic pump driven by the engine's timing chain. Compared to the new Mercedes-Benz system, Citroën's was belt-driven and failure of the Citroën system might mean loss of vehicle control. In the event of a hydraulic failure on the 6.9, every unit was shipped with hard rubber emergency dampers that served as temporary springs and allowed the car to be driven. The special hydraulic fluid required by the system was stored in a tank inside the engine compartment. Not only was the system totally self-adjusting, ride height could be altered by a dash-mounted push-pull knob under the speedometer that raised the car an additional two inches (50 mm) for increased ground clearance. The system gave the 4200 pound (1900 kg) car the benefits of a both a smooth ride and handling that allowed it, in the words of automotive journalistDavid E. Davis, to be "tossed about like a Mini." The car also featured a model W3B 050 three-speed automatic transmission unique to the 6.9 and a standard ZF limited slip differential both for enhanced roadholding performance on dry pavement and enhanced traction in inclement weather. Four-wheel disc brakes and four-wheel independent suspension were standard across the W116 model range.

See also: Mercedes-Benz 450SEL 6.9/Specifications.

The M-100 power plant

The engine was a cast iron V8 with a single overhead camshaft operating sodium-filled valves (as are found in piston-driven aircraft) against hardened valve seats on each aluminium alloy cylinder head. Each hand-built unit was bench-tested for 265 minutes, 40 of which were under full load. Bosch "K-Jetronic" electromechanical fuel injection was standard at a time when fuel-injected cars were uncommon. As in all Mercedes-Benz automobile engines, the crankshaft, connecting rods and pistons were forged instead of cast. In non-US trim, the 6.9 litre (6814 cm³ or 417 in³) power plant was conservatively rated at 286 horsepower (213 kW) with 405 ft·lbf (549 N·m) of torque helping to compensate for the 2.65 to 1 final drive ratio necessary for sustained high-speed cruising. The North American version, introduced in 1977, was only slightly less powerful at 250 horsepower (186 kW) and 360 ft·lbf (488 N·m) of torque due to more stringent emissions control requirements. In the interest of both engine longevity as well as creating some extra space under the hood, a "dry sump" engine lubrication system was used. Originally developed for use in race cars as a way to prevent foaming of the engine oil by the crankshaft which in turn would create a serious drop in oil pressure, the system circulated twelve litres of oil between the storage tank mounted inside the right front fender and the engine as opposed to the usual four or five litres found in V8s with a standard oil pan and oil pump. As a result, the engine itself had no dipstick for checking the oil level. Rather, the dipstick was attached to the inside of the tank's filler cap (accessible from the engine compartment) and the oil level was checked with the engine running and at operating temperature. The dry sump system also had the benefit of extending the oil change interval to 12,500 miles (20,000 km). This, along with hydraulic valve lifters which required no adjusting and special cylinder head gaskets which eliminated the need for periodic retorquing of the head bolts made the 6.9 nearly maintenance-free for its first 50,000 miles (80,500 km), requiring little basic service other than coolant, minor tune-ups, oil changes and replacement of the air, fuel, oil and power steering filters.

Autobahn cruiser versus race track

Top speed was factory-rated at 140 mph (225 km/h), but some journalists testing the car saw speeds approaching 150 mph (241 km/h). Among those journalists was Brock Yates. Yates was approached by the factory to write promotional literature about the 6.9. He agreed, but under the condition that he could list the car's faults as well as its positives. Daimler-Benz agreed in turn, and Yates was given a US-spec 6.9 to drive from Manhattan to the Road Atlanta grand prix race track in Georgia. There, Yates would drive the car in as-arrived condition at racing speeds for a full 40 laps or just over 100 miles (160 km). The only change made to the car upon its arrival at Road Atlanta was the necessary adjustment of tire pressure. This was a difficult task even for a purpose-built race car, let alone a street-legal sedan designed and geared for high-speed Autobahn cruising. The 6.9 suffered no mechanical problems and averaged a very respectable 72 mph (116 km/h) throughout the test, completing it with little more than excess dust on the bodywork from the Michelin radial street tires on which the car was driven to Atlanta. Yates was so comfortable driving the 6.9 around the course that he reported having run at least one lap with the sunroof open and the radio on, but the high price of the car made him think better of such risky driving and he finished the test with the radio off and both hands on the wheel.

High price of admission

All of this technology came at a very high price. At a time when the most expensive Cadillacs, the mid-sized Seville and full-sized Fleetwood Series Sixty limousine each listed for about US$16,000, the 6.9 listed for around $40,000, more than most Rolls-Royces. When the car was officially introduced into the North American market for the 1977 model year — the only way to get a 6.9 in the US or Canada prior to then was to import one through the grey market, that is, other than through DBAG's official import arm — the price was well past $40,000 and on its way to around $53,000 by the end of production. Though the 6.9 was undeniably a luxury car, it was a rather austere one compared to the sheer opulence available in a Rolls-Royce or full-sized Cadillac. The interior was identical to that in the less expensive models except for the push-pull suspension control knob just under the speedometer, an indicator light for the suspension in the instrument cluster which warned of both low pressure and whether the height adjustment was engaged and standard wood trim finished in burled walnut veneer on the dash and console unlike the rest of the W116 lineup which was trimmed in zebrano veneer. The 6.9 lacked expected luxury touches such as power-adjustable outside mirrors or front seats, although a unique power rear seat, heated seats and even orthopedically-designed front seats were options. Buyers outside North America could also opt for headlight wipers and washers and/or headlights with a special vacuum-operated linkage whose aim could be adjusted at the dash depending on vehicle load. 1977 also saw a new standard feature. Most Mercedes-Benz automobiles that year were equipped with a sophisticated electronic climate control system developed by Chrysler Corporation for use in their top models. The system turned on the heater, air conditioner or both depending on the thermostat's setting and ambient temperature, automatically maintaining whatever temperature the driver selected.

Far more modern than the Rolls and both faster and larger inside than either the Rolls or Cadillac, especially after the latter's 1977 downsizing, the 6.9 was indistinguishable from its W116 stablemates save for a modest "6.9" badge on the decklid and wider tires. As discreet as the badge was, it could be deleted at extra cost for those who wanted to avoid attention either from drivers of other high-performance cars or from law enforcement. In the words of David E. Davis, the 6.9 was "a $50,000 exercise in going fast."

Still, for fans of the discontinued 6.3 or for those who simply had to have a car which Car and Driver proclaimed to be "the greatest Mercedes-Benz ever built," it seemed that money was no object. More than 7500 6.9s were produced during the model's production run and were immediately purchased by the rich, the famous and the powerful despite the rising cost of gasoline brought on by the Arab oil embargo.

The 6.9 today

In a poll conducted by Britain's Classic & Sports Car magazine and printed in their April 1999 edition, the Mercedes-Benz 6.9 ranked fourth on their list of the "world's greatest saloons." The May 2004 edition of another British publication, Mercedes Enthusiast magazine, ranked the 6.9 number fifteen on their all-time top twenty list of great Mercedes-Benz automobiles. Even with such accolades, a 6.9 is a reasonably priced collectable automobile despite its rarity. The online NADA Used Car Guide lists a top value of US$20,000. At present, the market for cars of this type is somewhat soft, and a prime example can be had for considerably less. Given the car's exotic engineering and the traditionally high cost of some Mercedes-Benz parts, certain parts unique to the 6.9 can be extremely rare and expensive. However, careful shopping via the Internet can often reduce the costs.

Notable versions

• Director John Frankenheimer, a fan of the car, used a 6.9 in a chase scene in his 1998 motion picture thriller, Ronin.

• Since the original owners of the cars were among the world's most wealthy and famous, it should come as little surprise when one turns up with a pedigree. A slightly rough 6.9 was sold via an eBay auction with documentation linking ownership to John F. Kennedy, Jr. and prior to that, his uncle, Sargent Shriver. A contributor to the International M-100 Group bulletin board (see link below) purchased a unit in Pasadena, California that was fully documented as being purchased by Howard Keck, former CEO of Superior Oil, owner of a two-time winning Indianapolis 500 team and head of one of the world's largest philanthropic organizations, the H.R. Keck Foundation.

• With its reserves of power, the 6.9 was a natural for conversion into an armoured car. One such version that had been owned by the Shah of Iran was recently up for auction in New York City.

• There were never any plans to build a station wagon version of the W116, 6.9 or otherwise, owing both to the location of the fuel tank ahead of the rear axle and the overwhelming demand for the sedan versions. Still, a number of W116s were converted to station wagons by coach builders in Germany and England. In 1977, a German diplomat named Manfred Sittmann commissioned the Brinkmann karosserie of Bremen to build a 6.9 station wagon, or "estate car." Sittmann frequently travelled with two large dogs and a family entourage to Italy. German motorsports magazine Auto, Motor und Sport learned of the car and requested an interview with Herr Sittmann and a photo shoot as well. The magazine's feature would be titled "Die teuerste Hundehütte," or "The Most Expensive Doghouse." This one-off 6.9 currently sees regular use with its third owner, a Mercedes-Benz collector in Pennsylvania.

• A collector in Idaho recently created a website promoting the sale of his own one-off 6.9. Nicknamed "Benz-El," the car has been converted from a four-door sedan into a two-door pickup truck or ute with the use of rear sheetmetal and glass from a 1978-1987 Chevrolet El Camino.

• Dennis Adler, reporting in the March/April 2000 edition of The Star, which is the official publication of the Mercedes-Benz Club of America, related an amusing story about an impromptu race on Los Angeles' Hollywood Freeway between the first grey market 6.9 imported to the US and the unsuspecting young driver of a 1968 Pontiac GTO. The story is available at the website of the International M-100 Group (see below).12

References and external links

• International Association of M-100 Owners (http://www.m-100.info) — Links to the home page of an owner-centric advocacy group with extensive on-line historical documents, photographs, technical forums and maintenance information.
• International M-100 Group (http://www.m-100.cc) — This links to the home page of a factory-authorized site with information on all M-100-powered Mercedes-Benz automobiles. The Brock Yates article can be found here as well.
• The Mercedes-Benz M-100s (http://www.m-100.org) — A similar but non-moderated site with much of the same information as the above link.
• A Mercedes for the '70s: The W116 Series S-Class (http://www.breithaupts.com/totc198.htm) — A site mixing the history of the full-scale W116 with that of its many miniature replicas.
• Lode Star magazine, Autumn 2003 edition. Information regarding the Manfred Sittmann estate car conversion.
• Website dedicated to the custom "Benz-El" pickup truck conversion. (http://www.thinkbob.com/benzel/)

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