Mercedes-Benz 450SEL 6.9

The Mercedes-Benz 450SEL 6.9 was a high-performance version of the S-Class luxury sedan. Built by Daimler-Benz AG (now DaimlerChrysler) and based on the long-wheelbase version of the "W116" chassis introduced in 1973, the 6.9, as it was generally referred to in the company's own literature to separate it from the regular 450SEL, was first shown to the motoring press in 1974 and produced between 1975 and 1980 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.

Although the 6.9 resembled thousands of other W116-based cars, the difference ended at the skin. 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 engine, one of the most technologically advanced in the world was a cast iron V8 with a single overhead cam operating sodium-filled valves (as are found in piston-driven aircraft) against hardened valve seats on each aluminum 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. In typical Mercedes fashion, the crankshaft, rods and pistons were forged instead of cast. In non-US trim, the 6.9 liter (6814cc or 417 in&sup3) power plant was conservatively rated at 285 horsepower (212 kW) with 405 foot-pounds (549 Nm) of torque helping to compensate for the rather tall 2.65 to 1 final drive ratio. And 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 liters of oil between the storage tank and the engine as opposed to the usual four or five liters found in V8s with a standard oil pan and oil pump. 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 that 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 more than fluid, filter and spark plug changes.

More than just an engine swap, the 6.9 was also the first Mercedes-Benz to use the hydropneumatic suspension system, unlike the 600 and 6.3 which employed air suspensions. Using a combination of fluid-filled struts and gas-filled pressure vessels in lieu of conventional shocks and springs, the system was pressurized by a hydraulic pump driven by the engine's timing chain. Not only was the system totally self-adjusting, ride height could be altered by a dash-mounted knob that raised the car an additional two inches (5 cm) 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 journalist David E. Davis, to be "tossed about like a Mini." Four-wheel disc brakes and four-wheel independent suspension were standard as were a three-speed automatic transmission unique to the 6.9 and a standard limited-slip differential (optional on other W116 cars) both for performance and traction advantage in inclement weather.

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 benefits. Daimler-Benz agreed in turn, and Yates was given a US-spec 6.9 to drive from Manhattan all the way to Atlanta where he would personally drive the car at racing speeds around the Road Atlanta grand prix race course for a full 40 laps or just over 100 miles (160 km). 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, winding up with little more than excess dust on the bodywork from the Michelin street tires on which the car was driven to Atlanta. In fact, Yates was so comfortable driving the 6.9 around the course that he ran at least one lap with the sunroof open and the radio on!

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. And 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, lacking expected luxury touches such as power-adjustable outside mirrors or front seats, although a unique power rear seat was an option. Though 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 virtually indistinguishable from its W116 stablemates save for a modest "6.9" badge on the decklid. 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.

Still, for fans of the late 6.3 or for those who simply had to have a car dubbed by Car and Driver 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 snapped up by the rich, the famous and the powerful as fast as the factory could produce them despite the rising cost of gasoline brought on by the Arab oil embargo.

Today, a 6.9 is a rare and highly collectable automobile. Because it was known to so few, and is therefore not in great demand, a 6.9 is also a reasonably priced collectable. Beautiful examples can easily be had for well under $20,000 at this 2004 time of writing. And, in the May, 2004 edition of England's Mercedes Enthusiast magazine, the 6.9 was ranked number fifteen on their all-time top twenty list of great Mercedes-Benz automobiles.

For anyone who is reasonably capable regarding auto repairs, basic maintenance and repairs are both easy and surprisingly affordable despite the car's overall complexity. Virtually all parts are available through most normal channels including any Mercedes-Benz dealer or DaimlerChrysler's "Classic Mercedes" program, not to mention that old W116 in the neighborhood wrecking yard. 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 turn up some considerably less painful alternatives.

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

• Given the original owners of the cars, 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) claimed to have discovered a unit in need of restoration in Long Beach, California that was documented as having belonged to George McGovern.

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

• 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 traveled 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.

• International M-100 Group

This links to the home page of a factory-authorized site with a wealth of information on all M-100-powered Mercedes-Benz automobiles. The Brock Yates article can be found here as well.

• The Mercedes-Benz M-100s

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

An interesting and well-researched 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.