M163

Having watched Auto Union close the gap late in 1938, the racing department was unwilling to defend the European Championship on the previous year’s engine, and submitted a list of faults it wanted cured. The M163 that came back offered no fundamental innovation; it removed known design weaknesses of the M154 and changed how the V12 was blown. Two superchargers now ran in series rather than side by side, the first raising boost to about 0.83 bar and the second to 1.31 — for roughly half the power previously absorbed in driving them.

Peak output barely moved, and surviving test figures scatter between about 417 and 477 hp; the gain was that similar boost arrived 500 rpm lower down, which made the engine far more durable. It first raced at Spa on 25 June 1939, in a Belgian Grand Prix won by Hermann Lang in a car still carrying the older unit, and remembered for the crash that killed Richard Seaman while he led on lap 22. Development continued into the spring of 1940. The chassis was always a W 154; post-war writers who mistook the engine number for it invented the W 163.