Auto Union’s ultimate Grand Prix challenger was the two-stage supercharged V12 D-type. Mick Walsh braves the 485bhp Mercedes-Benz beater from Chemnitz.
There’s nothing like the routine of starting an Auto Union’s 3-litre, triple-cam V12. With bonnet removed from its brutal, slug-like form, three specialists from Crosthwaite & Gardiner perform the well-practised ritual of preparing this mid-engined 1939 titan. First all the plugs are removed from the magnificent Robert Eberan von Eberhorst-designed 60˚ V12 before the remote starter motor is plugged into the tail to crank up the oil pressure. Once the needles prick up on the black aviation instruments, the next stage is priming four-star into the twin Solex carburettors that feed the mighty two-stage superchargers. Space is tight at the back end above the de Dion axle and ZF differential, so it’s done with a brass syringe.
Once the floats are full, the final stage is ready. We’re running a light load of methanol in the rear tank behind the cockpit rather than the full race level in the side pannier tanks. The four-star is only squirted into the carbs for start-up whereupon the twin aircraft DB pumps behind the driver’s head start feeding the high-octane 50/40/10 mix of methanol, four-star and toluene bonding agent. After the peaceful, methodical routine, the fearsome high-torque V12 erupts like a deafening rifle barrage before the methanol is sucked into the heads. Then the ferocious cackle turns into a clear, blood-curdling roar. With throttle opened, the noise peaks with a painful, brutal blare. I swore not to wear earplugs under a linen helmet, determined to get the full effect of this mighty motor, but quickly understood the knowing smiles of the C&G crew.
While the oil warms, the steering-wheel lock is released and the broad, leather-covered four-spoke is removed for access. Nuvolari would clamber in with the wheel in place but bulkier, taller aces such as Hans Stuck and Hermann Müller needed more room. With narrow ribbed footwell between the beefy oval chassis tubes, and supportive but upright cord seat, the cockpit is wide but short. Considering the power on tap, the drilled, widely spaced pedals look almost dainty hinged off the bottom bar. It’s impossible to heel and toe. Compared to period rivals, the D-type is flush with gauges, dominated by the big rev counter that reads to 8000rpm plus five smaller dials and a three-step magneto switch. Surprisingly, there are two oil pressure gauges, for the crank and camshaft. “They’ll both dance around but if one is at odds with the other, something is amiss,” says engine builder Ian Harold.
The V12 could rev to 10,000rpm but drivers didn’t usually exceed 7000rpm, where power peaked at a potent 485bhp. Weighing in at 1875lb (850kg), that gave a stonking 579bhp per ton. More handy was the maximum torque of 404lb ft at 4000rpm. With roller mains for its fabulous Hirth built-up crankshaft, the V12’s character contrasted with the earlier V16, revving higher, quicker and smoother.
With wheel locked back, I’m instructed that second is ideal to start in because of the torque. Down to the right between the seat corner and petrol tank is a stubby, chunky lever sitting in a five-speed gate with a dog-leg first inside and forward. This works an unfeasibly long rod linkage to the ’box, way back behind the engine.
The clutch is surprisingly light, with good bite and feel, but at tentative speeds the gearbox feels slow and clumsy. Yet C&G’s Ian MacFarlane says this is the best Auto Union ’box: “With the C-type you have to snatch and crash the gears, but with the D-type’s dog clutches it’s cleaner and quicker.” At higher revs I discover that he’s right – the faster you go, the sharper the change.