Mercedes-Benz 300 SL

A race car for the street

New York Mercedes distributor Max Hoffman, Daimler-Benz's official importer in the U.S., suggested to Daimler-Benz AG management in Stuttgart that a street version of the W194 sports racing car would be a commercial success, especially in America.^[2]

The racing W194 300 SL was built around a welded aluminum tube spaceframe chassis to offset its relatively underpowered carbureted straight-6 engine.^[2] Designed by Daimler-Benz's chief developing engineer, Rudolf Uhlenhaut, the metal skeleton saved weight while still providing a high level of strength. Since it enveloped the passenger compartment traditional doors were impossible, giving birth to the model's distinctive gull-wing arrangement.

Even with the upward opening doors, the 300 SL had an unusually high sill, making entry and exit from the car's cockpit problematic. A steering wheel with a tilt-away column was added to improve driver access.

The 300 SL's main body was steel, with aluminum hood, doors and trunk lid. It could also be ordered with an 80 kg (180 lb) saving all-aluminium outer skin at tremendous added cost; just 29 were made.

More than 80% of the vehicle's total production of approximately 1400 units were sold in the US, making the Gullwing the first Mercedes-Benz widely successful outside its home market and thoroughly validating Hoffman's prediction. The 300 SL is credited with changing the company's image in America from a manufacturer of solid but staid luxury automobiles to one capable of rendering high-performance sports cars.

It should be noted initial sales were sluggish due to many things. First of all the price. While initial prices were about $6,400, a new Chevrolet Bel-Air could be purchased for $1,700 in the same year. Then there were few mechanics, even at the dealers, who understood the fuel injection system enough to do repairs. One price instance was a 1955 Gullwing that was removed from the showroom to a warehouse as unsellable. It was finally sold at dealer cost, just to move it. This was at the Hollywood dealership in 1958. Another, was a used 1954 that was sold for $3,000 with a down payment of $75 in the San Francisco bay area(Alameda)by a private party in 1960. The owner was just tired of having it for sale for several years with little interest. Situations like these brought the cars price down so a whole new group of people, who for years had admired them from afar, could now afford them.

First direct injection

1956 Gullwing open

1956 Roadster

1956 dashboard

Like the W194, the 300 SL borrowed its 3.0 litre overhead cam straight-6 from the regular four-door 300 (W186 "Adenauer") luxury tourer introduced in 1951.^[2]

Featuring an innovative diagonal aluminum head that allowed for larger intake and exhaust valves, it was canted to the right at forty-five-degrees to fit under the SL's considerably lower hoodline.

In place of the W194's triple two-barrel Solex carburetors, a groundbreaking Bosch mechanical direct fuel injection was installed, boosting power almost 25% over the Gran Prix car's.^[2] Derived from the DB 601 V12 used on the Messerschmitt Bf 109E fighter of World War II, it raised output from 130 kW; 177 PS (175 hp) to 160 kW; 218 PS (215 hp), almost double that of the original Type 300 sedan's 86 kW; 117 PS (115 hp). An optional, even more powerful version, with radical camshaft developed 240 hp (243 PS; 179 kW) @ 6100 rpm and a maximum torque of 294 N⋅m (217 lb⋅ft; 30 kg⋅m) @ 4800 rpm ^{[4] [5]}, but was rough for city use. The result was a top speed of up to 260 km/h (160 mph) depending on gear ratio and drag, making the 300 SL the fastest production car of its time.^[2]

However, unlike today's electrically powered fuel injection systems, the 300 SL's mechanical fuel pump would continue to inject gasoline into the engine during the interval between shutting off the ignition and the engine's coming to a stop; this unburned gasoline washed lubricating oil from the cylinder walls, which not only left them unprotected in affected areas during start-up but would dilute the engine's entire oil supply if the car was not driven hard or long enough to reach a sufficient temperature to evaporate the gas out of the oil. To reduce this dilution by gasoline when stopping the engine, the owner's manual advised

Turn the ignition key to the left while idling. Do not on any account try to stop the engine at a higher speed.

Exacerbating the problem was the engine's large racing-oriented oil cooler and enormous 10 liters (2.2 imp gal; 2.6 U.S. gal) oil capacity, which virtually guaranteed the oil would not get hot enough. In practice, many owners would block off airflow through the oil cooler and stick rigidly to the appropriately low 1,600 km (1,000 mi) recommended oil change interval. An auxiliary fuel pump provided additional fuel for extended high speed operation or cold starts; overuse would also lead to dilution of the oil.,^[6][7]

Clutch operation was initially very heavy, remedied by an improved clutch arm helper spring which reduced pedal force. From March 1963 to the end of production later that year, a light alloy crankcase was used on a total of 209 vehicles.^[8]

Aerodynamics played an important role in the car's speed, with Mercedes-Benz engineers placing horizontal "eyebrows" over the wheel openings to reduce drag. Unlike many cars of the 1950s, steering was relatively precise and the four-wheel independent suspension allowed for a reasonably comfortable ride and markedly better overall handling. However, the rear swing axle, jointed only at the differential, not at the wheels themselves, could be treacherous at high speeds or on imperfect roads due to extreme changes in camber. The enormous fuel tank capacity also caused a considerable difference in handling depending on the quantity of fuel on board.

Mercedes-Benz Classic Center

Mercedes-Benz also operates the Mercedes-Benz Classic Center that focuses on classic Mercedes-Benz restorations and is recognized as the central authority on 300 SL parts, service, restoration and vehicle trading as they have unique access to original build sheets and factory documentation which enables them to confirm a car's authenticity – a critical factor determining a collector car's true value.^[15]