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Mercedes-Benz 450SEL 6.9

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European-spec 450SEL 6.9. North American versions featured four sealed-beam headlights and larger bumpers.
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European-spec 450SEL 6.9. North American versions featured four sealed-beam headlights and larger bumpers.

The Mercedes-Benz 450SEL 6.9 is 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, Germany and based on the long-wheelbase version of the W116 chassis introduced in 1972. The model was generally referred to in the company's literature as the "6.9", to separate it from the regular 450SEL.

The 6.9 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 produced with optional anti-lock brakes, first introduced by Mercedes-Benz and Bosch in 1978. The 6.9's successor - the top of range 560 SEL - continued the 6.9's remarkable self-leveling hydropneumatic suspension as an extra-cost option.

Contents

Special features

The 6.9 was visually and for the most part mechanically identical to other W116-based cars, but 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 6.3.

The 6.9 was also the first Mercedes-Benz to be fitted with the company's new hydropneumatic self-levelling suspension system, unlike the 600 and 6.3 which employed air suspensions. The new system was similar to one developed by Citroën in 1955. 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, exactly like a conventional power steering pump; failure of the Citroën system thus might mean loss of suspension. 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. NHTSA decreed this feature illegal in the US market.

The suspension 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." 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 L (6814 cc or 417 in³) power plant was conservatively rated at 286 hp (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 hp (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 L of oil between the storage tank mounted inside the right front fender and the engine as opposed to the usual four or five L 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 track 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. Standard model's wood trim was 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. The compressor was an American import as well, supplied by the Harrison division of General Motors and was originally designed for use with GM vehicles equipped with an inline six-cylinder engine.

Far more modern than the contemporary Cadillac, which still had a live rear axle, and both faster and larger inside than the either the Rolls-Royce or Cadillac, 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/ordered with option 261 omission of the displacement figure on the trunk lid 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. At its launch in 1975, the 450 SEL 6.9 cost DM 69,930. In the last year of production, 1979, the car was available at a price of DM 81,247. Not exactly peanuts, but the courage of the Mercedes-Benz strategists in launching the car onto the market paid off. A total of 7,380 units were built until 1980, and most of these were exported to the USA. This volume figure looks rather small at first glance, but one mustn’t forget the car’s belonging to the top luxury segment where production figures are seen in a different light. And the 6.9 was, after all, not the only S-Class model - and 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 collectible 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.

Famous Owners

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:

Notable versions

References and external links


[[Template:Classic Mercedes-Benz-Azubis vehicles|<- Previous]] Mercedes-Benz road car timeline, 1980s-present [ edit]
Type Class 1980s 1990s 2000s
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9

Supermini A W168 W169

Compact C W201 (190) W202 W203 W204

Mid-size E W123 W124 W210 W211 W212
CLS W219

Full-size S W126 W140 W220 W221
Maybach W240

Roadster SLK R170 R171
SL R107 R129 R230

Coupé CLK W208 W209
CL W126 W140 W215 C216

Supercar SLR C199

SUV G W460/W461 W463

Crossover SUV GLK GLK
M W163 W164
GL X164
MPVs B W245
R W251
Vaneo Vaneo
Sprinter Sprinter

 

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