Model Profile: 1938 Mercedes Benz W154

June 15, 2023

IN the glorious noises department, the 1938 Mercedes-Benz W154 grand prix car has few equals except for some postwar Ferraris and Maseratis. But where the Italian cars shrilled, this one shrieked like an animal in agony when the twin superchargers cut in. By pre-war standards the car was not considered hard to drive, even though it would spin its wheels in top gear at 200 miles an hour if the accelerator was floored. It was a beast of a very different nature from the rear-engined Auto Union of the time, which might have been the original dog with the waggledy tail.

The grand prix formula for 1938 was for three-litre blown engines or 4.5-litre unblown, with a minimum weight limit of 850 kilograms (1874 lb). The previous formula had a 750 kg weight factor. The idea now was slow the cars down by making them less powerful and heavier. Mercedes offset the lost capacity by producing a twin-supercharged three-litre 60-degree V12 engine with maximum piston area.

It had two overhead camshafts to each bank, operating four valves in each cylinder. Crankshaft and conrods ran in roller bearings and no fewer than nine oil pumps lubricated this beautiful piece of engineering.

The twin superchargers put the boost pressure up to 12.25 kg (27 lb), which was more than double that of the 1937 W125. Output was 483 bhp at 8000 rpm.

The tall back wheels were driven through an open propellor shaft and a five-speed transaxle with a limited slip differential. The new car's debut was something of a disaster, though. The 1938 Pau Grand Prix was the first race under the new formula. Rene Dreyfus, in an unblown 4.5-litre Delahaye, ran the distance non-stop to win in what was a much slower car. Rudi Caracciola and Hermann Lang had to bring in their Mercedes for fuel and could not

catch the Frenchman afterwards. The one thing all the drivers disliked about the W154 was its enormous fuel consumption, which meant it had to have vast tankage. With tanks back and front of the cockpit, the chances of escaping from a crash-and-burn were indeed slight.

But after Pau Caracciola, Lang, Manfred von Brauchitsch and Seaman won almost as they pleased in 1938. The opposition Auto Unions were not the threat they had been after their best driver, Berndt Rosemeyer died in a speed record bid.

But the great Italian, Tazio Nuvolari, soon got the measure of the tricky, rear-engined car and beat the Mercedes in the last two outings of the season, at Monza and Donington.

In spite of this Mercedes won six out of the 10 major races and Caracciola the European championship for the third time in a row. The W154 at Sandown is from the Mercedes Collection of historic cars in Stuttgart. And just by the way it runs on an alcohol-based fuel that is so corrosive the system has to be drained after every run lest the innards are eaten away.