1936 Auto Union C-type 6 litre V16
1936 Auto Union C-type 6 litre V16. Used from 1934 to 1937 was an amazing and magnificent achievement. Among the most brilliant, the only 16-cylinder ever to achieve consistent success. By Dr.Eng. Ferdinand Porsche and designer Josef Kales. High power through high torque at low crank speeds.
Lower structural stresses allowed the block and crankcase to be cast in one piece in thin wall high-silicon-alloy aluminum. Inserted were forged chrome-alloy-steel cylinder liners exposed to cooling water. Detachable cylinder heads were used, studs retaining the heads were long, extending well down into the block. Cylinder banks at 45 degrees and valves disposed at 90 degrees to each other, single 18mm spark-plug was used.
A masterful arrangement of valve gear and induction, only one single central overhead camshaft was used, rotating in 9 bearings and containing 32 lobes, opened the inlet valves directly through fingers on parallel shafts, the outboard exhaust valves were opened remotely through finger followers which operated rocker arms at the exhaust valves through horizontal push-rods.
The major accessory drives were at rear of engine, taken from crank between ninth and tenth main bearings. Bevel gear drive vertical shaft from crankshaft drove the camshaft. Side bevel gears from this shaft drove the twin eight cylinder Bosch magnetos. Above them a multi-disc clutch pack drove the primary lobe of a vertical roots supercharger delivering 2.8 litres per revolution rotating more than twice engine speed with a boost of 9psi.
Blower was offset to left so its output could be ducted around the vertical shaft to the center inlet passage. With surpassing genius it was arranged for the inner surface of the heads covered by aluminum casting of cam-housing to enclose a volume that served as inlet manifold.
The bottom of crankcase was at an angle as viewed from the side, at the rear it reached all the way down to the bottom of clutch/flywheel assemble. At the rear twin gear-type oil pump rotating at 5 times engine speed, 1 was scavenge the other a pressure pump.
The exhaust manifold collected 2 cylinders at a time (4 exhaust pipes on each side). Forged chrome-nickel-steel crankshaft in tin-bronze bearings shells, similar bearings for con-rods, an external tube from big-end to gudgeon pin carried oil to pin. Pins retained by aluminum buttons. A Solex 2 float chambers twin-throat 48mm carburetor was used.
Stroke/bore ratio 1.13:1.
Compression ratio 9.2:1.
Con-rod length 168mm.
Rod/crank radius ratio 4:1.
Main journal 70mm.
Rod journal 68mm.
Inlet valve 35mm.
Exhaust valve 32mm.
Inlet pressure 1.97Atm.
Peak power 520BHP@5000rpm.
Piston speed corrected 13.1m/s.
Peak torque 854Nm@2500RPM.
Peak bmep 260psi.
...not because they are easy, but because they are hard!