Mercedes-Benz 450SEL 6.9

Mercedes-Benz 450SEL 6.9
Overview
Manufacturer Daimler-Benz
Production 19751981
Body and chassis
Class Full-size luxury car (F)
Platform Mercedes-Benz W116
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.

Special features

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 suspensions. 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. Conversely, every unit of 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. 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.

US market 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. The North American version, introduced in 1977, was rated with 36 fewer horsepower and 45 fewer lb·ft (250 and 360, respectively), due to the differing and higher emission standards at the time. 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.[5] 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.[6]

Price and interior features

The dashboard of a Mercedes-Benz 450SEL 6.9, US version.

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 Cadillac Fleetwood Series Seventy-Five limousine each listed for about US$16,000, the 6.9 listed for around $40,000, more than the Big Three but less than most Rolls-Royces. When the car was officially 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. 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, 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.

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. 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.

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.[7] US models also had different bumper rubbers fitted to the "park bench" impact absorbing bumpers. 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. 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 USA. 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.

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." [8] 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. As is often the case with older cars that contain exotic engineering and parts unique to that one model, however, running and maintenance costs for a 6.9 can quickly overshadow a low initial purchase price.

Notable versions

Noted owners included: Sir Bernard Ashley; James Hunt;[13] John F. Kennedy, Jr.; Frank Sinatra, Vladimir Vysotsky

Specifications

Mercedes-Benz 450SEL 6.9[14]
ManufacturerDaimler-Benz AG
ClassFive-passenger, four-door luxury sedan
Body StylesFour-door sedan
Predecessor300SEL 6.3
SuccessorNone
Shares components withMercedes-Benz 600, Mercedes-Benz 300SEL 6.3, other Mercedes-Benz W116 sedans
Wheelbase:116.5 in 2960 mm
Front track59.9 in 1521 mm
Rear track59.3 in1505 mm
Overall length:210 in 5335 mm
Width:73.6 in1870 mm
Curb weight:4390 lb 1985 kg
Fuel tank capacity25.3 US gal, 20.897 gallons English95 L
Trunk (boot) capacity18.2 ft³ 0.52 m³
Battery capacity12 V, 88 A·h
Steering wheel turns2.7 lock-to-lock
Turning circle40 ft12.1 m
Head Room - Front38.6 in980 mm
Leg Room - Front41.7 in1060 mm
Hip Room - Front57.5 in1460 mm
Shoulder Room - Front55.1 in1400 mm
Head Room - Rear37.1 in942 mm
Leg Room - Rear38.1 in967 mm
Hip Room - Rear59.5 in1510 mm
Shoulder Room - Rear54.9 in1394 mm
EngineV-8, Bosch fuel injection, electronic ignition, two single overhead camshafts, five main bearings
Net power @4250 rpm
(World)
286 PS210 kW
Net torque @3000 rpm
(World)
405 lbf·ft549 Nm
Net power @4200 rpm
(Australia)
269 HP198 kW
Net torque @2800 rpm
(Australia)
376 lbf·ft510 Nm
Net power @4000 rpm
(North America)
250 hp186 kW
Net torque @2500 rpm
(North America):
360 lbf·ft488 Nm
Compression ratio
(World)
8.8:1
Compression ratio
(North America)
8.0:1
Bore/stroke4.21 × 3.74 in107 × 95 mm
Displacement417.1 in³6834 ccm
Maximum engine speed5300 rpm
Transmission:Three-speed automatic with torque converter
Rear axle ratio2.65:1
Tires and wheelsMichelin XWX 215/70VR14 steel-belted radial; 6.5Jx14 light alloy
Braking system Dual-circuit, power-assisted hydraulic, four-wheel disc brakes. Front discs ventilated.
Total swept brake area456.5 in²2945 cm²
0-60 mph (0–96 km/h)7.1 seconds
Top speed (World) 225 km/h (139.8 mph)
ProductionWorldNorth America
19754740
197614750
19771798462
19781665437
19791839576
1980129317
198140
Total73801816

References

External links

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