Mercedes-Benz 450SEL 6.9

Mercedes-Benz 450SEL 6.9
Overview
Manufacturer	Daimler-Benz
Production	1975–1981
Body and chassis
Class	Full-size luxury car (F)
Platform	Mercedes-Benz W116
Powertrain
Engine	6.834 L M100 V8
Transmission	3-speed automatic
Dimensions
Wheelbase	2,960 mm (116.5 in)
Length	5,060–5,335 mm (199.2–210.0 in)
Width	1,870 mm (73.6 in)
Height	1,430 mm (56.3 in)
Curb weight	1,985 kg (4,376 lb)
Chronology
Predecessor	Mercedes-Benz 300SEL 6.3
Successor	Mercedes-Benz 560 SEL (direct) Mercedes-Benz S 600 (ideological) Mercedes Benz S 63 AMG (spiritual)

The Mercedes-Benz 450SEL 6.9 is the high-performance top-of-the-line version of the W116 model S-Class luxury saloon. It was built by Daimler-Benz 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. It featured the largest engine of any non-American production car post WWII.^[1][2][3][4]

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 electronically controlled 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 self-leveling hydropneumatic suspension as an extra-cost option. Active Body Control is the current iteration of this innovation.

Suspension

The 6.9 was the first Mercedes-Benz to be fitted with the hydropneumatic self-levelling suspension system introduced by Citroën in 1954, unlike the 600 and 6.3 which employed air suspension.^[5]

The benefit of this arrangement is progressive springing. The more the enclosed air in the suspension is compressed, the more difficult it is to compress; thus the suspension rate changes in proportion to the load.^[5]

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 result in loss of suspension. The 6.9 was shipped with hard rubber emergency dampers that served as temporary springs and allowed the car to be driven in the event of a hydraulic failure. The special hydraulic fluid required by the system was stored in a tank inside the engine compartment. 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.

Euro-spec 450SEL 6.9

The suspension system gave the 4200 pound (1900 kg) car the benefits of 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.

M-100 power plant

The engine was a cast iron V8 with single overhead camshafts operating sodium-filled valves 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. The 6.9 l (6834 cc or 417 in³) power plant was factory-rated at 286 hp (213 kW) with 405 lb·ft (549 N·m) of torque helping to compensate for the 2.65 to 1 final drive ratio necessary for sustained high-speed cruising. A special version for Australia, based on the North American version, however without catalyst, was rated at 269 hp (198 kW) with 51 kpm (510 N·m) of torque.^[6] 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. The system circulated twelve quarts of oil between the storage tank and the engine, as opposed to the usual four or five quarts 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). The 6.9 required little basic service other than coolant, minor tune-ups, oil changes, and replacement of the air, fuel, oil and power steering filters.

Race track performance

Top speed was factory-rated at 140 mph (225 km/h). Among the journalists that tested and reviewed the car 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. Driving 40 laps 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.^[7]

US exports

US market 450SEL 6.9

Of the 7,380 units built, 1,816 were officially sold in the US.

When the car was introduced into the North American market for the 1977 model year, the price was well past $40,000 and was $52,995 by the end of production. The 6.9 was rather austere compared to the opulence in competitors like the Rolls-Royce or Cadillac. ^[5] The most expensive Cadillacs, the mid-sized Seville and full-sized Cadillac Fleetwood Series Seventy-Five limousine each listed for about US$16,000. The 6.9 listed for around $40,000, when the Rolls-Royce Silver Shadow sold for $43,200. ^{[5] [8]}

The 6.9's variable height suspension was illegal in the U.S. at the time so U.S. specification cars deleted the knob that allowed the driver to raise the car.^[9]

The North American version was rated with 36 fewer horsepower and 45 fewer lb·ft torque (250 and 360, respectively), due to differing emission standards.^[10]

US models also had extended "park bench" impact absorbing bumpers.

The US cars were fitted with four fixed round exposed lamps. 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. Separate glass windshields for headlights were illegal in the US after 1967, which is why the Citroën DS did not get them on US cars when it was restyled for 1968, and the VW Beetle and Vanagon/Kombi and Jaguar E-Type lost their headlight glass windshields at the same time.^[11]

Price

The dashboard of a Mercedes-Benz 450SEL 6.9

At its launch in 1975, the 450SEL 6.9 cost DM 69,930. In the last year of production, 1979, the car was available at a price of DM 81,247. Even though this was far from inexpensive, the courage of the Mercedes-Benz strategists in launching the car onto the market paid off. A total of 7,380 units were built by 1980, with only 1,816 officially sold in the US. This volume figure looks rather small at first glance, but production figures tend to be significantly smaller in the top luxury segment where this model competes. Also, the 6.9 was not the only S-Class model, and was purchased by the rich, the famous, and the powerful despite the rising cost of gasoline brought on by the Arab oil embargo. Thus, the 7,380 total sales volume is quite respectable once the price and contemporary economic climate are taken into account.

Interior features

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. There was also a new standard feature in 1976: 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.

The interior was identical to that in the less expensive models except for the push-pull suspension control knob just under the speedometer, a low suspension pressure warning and height adjustment indicator lights in the instrument cluster, and wood trim finished in burled walnut veneer on the dash and console. The rest of the W116 lineup was trimmed in striated zebrano veneer.

Being the top-of-the-line offering in its brand and model lineup, the 6.9 was rather indistinguishable from its W116 stablemates save for a modest "6.9" badge on the decklid and wider tires.^[5] The badge could be deleted/ordered with option No. 261 i.e. omission of the displacement figure on the trunk lid at extra cost from the factory. 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.^[5]

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." ^[12]

Cultural references

• The 6.9 featured prominently in a high-speed car chase in the film Ronin and was in all probability the actual car (with an overlaid sound track from a Ferrari 275 GTB) driven in Claude Lelouche's short film C'était un rendez-vous where it is driven through Paris at high speed with a camera mounted on the front bumper.
• In David Lynch's 1996 film, Lost Highway, a Mercedes 6.9 is used as a major plot device, ultimately connecting all three main male characters of the movie. In one scene, the hood is opened to reveal an after-market modification, bringing the engine power to "1400 horsepower", according to one character. In another scene, the car is used to push a Ford Thunderbird off the road, despite the latter applying the brakes.^[13][14][15]

Specifications

Performance

Magazine test results:

• 0–30 mph (48 km/h): 2.5 s^[17]
• 0–40 mph (64 km/h): 3.9 s^[17]
• 0–50 mph (80 km/h): 5.3 s^[17]
• 0–60 mph (97 km/h): 7.1 s^[17]
• 0–70 mph (113 km/h): 9.3 s^[17]
• 0–80 mph (129 km/h): 12.0 s^[18]
• 0–90 mph (145 km/h): 15.4 s^[17][18]
• 0–100 mph (161 km/h): 19.5 s^[18]
• 0–110 mph (177 km/h): 24.9 s^[18]
• 0–120 mph (193 km/h): 33.1 s^[18]
• 0–124.3 mph (200 km/h): 33.7 s^[19]
• 0–62.1 mph (100 km/h): 7.8 s^[19]
• Standing ¹⁄₄ mile (402 m): 15.4 s @ 90 mph (145 km/h)^[18]
• Standing 1 km (0.62 miles): 28.2 s @ 115 mph (185 km/h)^[18]
• Braking 70-0 mph: 207 ft (113–0 km/h: 63 m) (0.79g)^[17]
• Fuel economy, EPA mileage cycle: 10 miles per US gallon (23.5 L/100 km; 12.0 mpg_‑imp) urban, 14 miles per US gallon (16.8 L/100 km; 16.8 mpg_‑imp) highway^[17]
• Top speed: 147 mph (237 km/h)^[19]

References

External links

• International M-100 Group — Factory-authorized site with information on all M-100-powered Mercedes-Benz automobiles, (including technical forums and maintenance information). The Brock Yates article can be found here as well
• A Mercedes for the '70s: The W116 Series S-Class — A site mixing the history of the full-scale W116 with that of its many miniature replicas.
• Classic Car driver review
• Golden Brown: Four Days in a Mercedes-Benz 450SEL 6.9 - Feature (Car and Driver)
• Curbside Classic: 1977 Mercedes 450 SEL 6.9 – Deutsches Heavy Metal – a retrospective of the 450SEL 6.9
• Petrolicious: Mercedes-Benz 450SEL 6.9 Was All About Engineering – another retrospective of the 450SEL 6.9
• Youtube clip of Ronin high-speed chase featuring a 6.9