The great supercharged 1927-1932 Mercedes S/SS/SSK/SSKL were among the fastest cars, and some of the most beautiful, ever to put rubber to road. Ever. They were triumphant on road and track, magnificent to look upon, and faster than any contemporary automobile that might qualify even part-time as a street sports car.
Yet the young Ferdinand Porsche, only 48 when he became technical manager of Daimler-Benz, had arrived to engineer them almost by accident, succeeding Paul Daimler, son of the firm's co-namesake. Yet all the work was not done by Porsche. Hans Nibel-who replaced Porsche and had been a D-B employee since 1904-also deserves credit for the series.
Daimler had won acclaim for his 1908 Grand Prix Mercedes racer and 1914 4.5 liter, but his greatest accomplishment was the supercharged Mercedes engine. His first blown unit was a Daimler aircraft engine, built from 1915-18, with a Roots-type blower driven by a gear on the flywheel. Its technology led to the first supercharged auto engine in 1919, which three years later had evolved into a production four-cylinder unit of 2.6 liters, the 10/40/65 (10 taxable bhp, 40 bhp unblown, 65 bhp blown).
Similar was the 28/95 supercharged six with 120 bhp, never installed in a production model, but important in helping Mercedes return to international racing at the 1921 Targa Florio. Subsequent racers were unsuccessful, however, and Daimler resigned at the end of 1922. Porsche was then charged with developing the masterful supercharged engines Daimler left behind into race winners and extremely capable street sports cars.
Fast touring cars had always been Mercedes' stock in trade, but after the last 28/95s were built in 1924 the lineup had lacked a worthy replacement. Porsche's first steps were to shorten the chassis of the Model 24/100/140 (a 6.3-liter monster weighing 3,400 pounds) and to boost its under whelming performance.
The result was the Model K (for kurz or "short"), introduced in 1926 as a Mercedes (not a Mercedes-Benz), weighing only 3,153 pounds. Its two spark plugs per cylinder (one fired by coil and breaker ignition, the other by magneto) and a 5.0:1 compression ratio gave 110 bhp without a blower or 160 bhp with blower engaged: officially 24/110/160. The gearbox was unaltered, but final drive ratios were lowered numerically to reduce engine revs in relation to road speed, which was a little over 90 mph.
The K was an admirable touring car, but being tall and ungainly, it was certainly no sports car. Its successor was.
Keep reading to learn more about the K's successor.
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The S, SS, and SSK Mercedes Models
Directly derived from the K, the 1927 model S (Sport) had impressively low construction and looked as fast as it was. The engine was bored to 6.8 liters; the Roots blower was gear-driven and set to run at three times crankshaft speed. This boosted maximum power to 180 supercharged and made the SK a genuine 100-mph car. It also featured a new four-speed gearbox with very low numeric ratios (2.76:1 standard, 2.5:1 and 3.08:1 optional), and its light roadster body gave it a curb weight of only 2,867 pounds.
The racing impact of the S was tremendous. During its career it racked up 53 racing victories and 17 speed records, including a German national mark for passenger cars of 110.3 mph. It was expensive, of course, and thus uncommon: most estimates put the total at 149, all built in 1927-1928.
At the end of 1928, Porsche left Daimler-Benz for Steyr in Vienna, and in 1930 he set up his own engineering firm in Zuffenhausen, where he became involved in the Volkswagen project. Meanwhile, he was replaced at Daimler-Benz by his former assistant Hans Nibel, another brilliant technician. Nibel's credits included the great 200-bhp "Blitzen Benz" speed record car of 1910 and a host of fine touring cars in the early Twenties.
Porsche was still at the helm when an even more formidable sporting Mercedes went into production in late 1928: the SS (Super Sport), basically a lighter S (by about 66 pounds) with a more powerful, seven-liter engine. Its blower, providing eight psi boost, was shared with the S, but compression was raised and valves and ports were larger. Maximum supercharged horsepower now rose to 200, top speed to 115 mph, and 0-60 took less than 15 seconds. Such numbers seemed like fiction in the world of 1928, but they were valid enough.
The SS remained in production up to 1933, but very few were constructed after the end of 1929. Total production is estimated at only 109 cars. Next step was the yet-hairier SSK, a short-wheel-base derivative of the SS built alongside it in 1928. As with the 1926 Model K, the letter denoted kurz (short). Its chassis was lighter still at 2,680 pounds. In addition a bigger blower delivering 10 psi boost, gave the SSK engine more power. With the supercharger engaged it put out 225 bhp at 3,200 rpm, good for a sizzling 120-mph top speed under test conditions with perfectly tuned factory examples.
The SSK enjoyed a brilliant competition career. Caracciola scored its first victory at the Gabelbach hillclimb in 1928, then repeated Model S wins at Frieburg and Semmering. In 1930, he won the Irish Grand Prix in an SSK against a host of open-wheel racing cars.
On track or road the SSK was truly a supercar. Britain's The Motor published a test in June 1931 and said the results (0-90 in 45 seconds, top speed 103.2) fell short of expectations. Considering the state of the art in the early 1930s, the editors must have expected a great deal, for such performance was then unequalled by any other car in the world. The number of SSKs built is estimated at 31, all from 1928 to 1931.
On the next page, learn about the light-weight SSKL.
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The 1931 SSKL Mercedes
Near the end of the run in 1931, a lightweight SSK made its appearance, not as a production item but as a special, reserved for the factory racing team. Only six of these cars, known as the SSKL, were built. The "L" stood for leight or "light," because the frame and many other components were drilled to remove excess metal. Chassis weight accordingly went down to about 2,640 pounds. At the same time, horsepower went up-way up.
The major modification was adoption of an "elephant" compressor delivering 12-psi boost, but the SSKL also had a lighter crankshaft and flywheel, special valves, high-lift camshaft, and high-compression pistons. The factory recommended using a fifty/fifty mixture of gasoline and benzol to avoid local overheating in the cylinder head. Maximum output was 300 horsepower at 3,300 rpm.
A special streamlined single-seater was built on the SSKL chassis in 1931 for Manfred von Brauchitsch to drive at Avus. It was the fastest car present, completing the race at an average speed of 121.6 mph. Its top speed was not far short of 150.
One measure of the SSKL's performance was provided in 1960 by Road & Track magazine. Geared with a 2.76:1 rear axle, the test car's top speed was 120 mph. Out of deference to its age, acceleration was calculated on the basis of power/weight ratio: 9.5 seconds for 0-60 mph, 41 seconds from 0-100. That was quite a performance for a 30-year-old veteran-and there wasn't a car of its era that could have touched it.
Keep reading for specifications on the Mercedes S, SS, SSK and SSKL.
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1927-1932 Mercedes S/SS/SSK/SSKL Specifications
The 1927-1932 Mercedes S/SS/SSK/SSKL were ultra fast, light cars. See specifications below.
Engine: ohv I-6, 431.4 cid/7,069 cc (3.94 × 5.9-in/100 × 150-mm bore × stroke), sohc, 2 updraft l-bbl M-B carburetors, 140 bhp @ 3,000 rpm; with Roots-type supercharger (8-psi boost): 200 bhp @ 3,000 rpm
Transmission: Non-synchro 4-speed manual; multi-dry-plate clutch
Chassis: Pressed-steel frame, channel-section side members, pressed or tubular cross members
Suspension, front and rear: Forged solid front axle, half-elliptic leaf springs front and rear, torque-tube rear axle, lever or friction shock absorbers
Brakes: Shaft-and-rod operated 4-wheel drum (vacuum assist opt.)
Tires: 6.50 × 20
Wheelbase (in.): 136
Overall length (in.): 185
Track, front and rear (in.): 58
Weight (lbs): approx. 2,800
0-60 mph (sec): 14-15
Top speed (mph): 115
Production: est. 109 SS; approx. 300 total S/SS/SSK/SSKL
*1928 27/140/200 SS