Daimler-Benz DB 605 - Design and Development

Design and Development

The primary differences between the 605 and 601 were greater displacement, higher revolutions, higher compression ratio and a more powerful supercharger. Through careful study the engineers determined that the cylinders could be bored out to a larger diameter without seriously affecting the strength of the existing block. The difference was minimal, increasing from the 601's 150 mm cylinder bore to the 605's 154 mm, but this increased the overall displacement from 33.9 litres to 35.7. Altered valve timing increased the inlet period and improved the scavenging to give greater volumetric efficiency at higher speeds, which improved the maximum allowable RPM from 2,600 in the 601 to 2,800 in the 605. The combination of these changes raised power output from 1,350 PS (1,332 hp) to 1,475 PS (1455 hp). The engine was otherwise similar, notably in size, which was identical to the 601. However, its weight did increase from 700 to 756 kg.

In other ways the engine was essentially identical to the 601, being a 12 cylinder, inverted-V (with the crankshaft above the cylinders) design. Both used dual Bosch magnetos firing twin spark plugs for ignition. Fuel injection was powered by a pump supplying up to 90 bar and the oil system used three pumps with a separate 35 litre oil tank. The supercharger was fairly advanced for the era in that it used a barometrically controlled hydraulic clutch (fluid coupling) which allowed the system to automatically compensate for changes in altitude.

Like the 601, the 605 was designed to run on "B4" fuel with an octane rating of 87. In 1944 a series of newer engines was introduced, allowing the engine to run on the 100 octane "C3" fuel and optionally including fittings for various optional power-boosting agent dispensing systems, such as the MW50 methanol-water injection system, and GM-1 nitrous oxide injection system. The DB 605AM, running initially on C3 and MW-50, saw power improved to 1,800 PS (1775 hp) for takeoff. In mid-1944, the requirement for C3 was dropped and B4 + MW-50 was used. The DB 605AS(M) improved the maximum rated altitude by using a larger supercharger taken from the DB 603 but was otherwise similar to the A(M). The DB 605ASB's takeoff power was also rated at 1,800 PS (1,775 hp), while maintaining the high-altitude performance of the ASM. The final version of the A-series was the DB 605ASC of 1945, which improved takeoff power to 2,000 PS (1,973 hp).

As early as 1942 Daimler had also been working on an upgraded D-series engine that could run on either C2 or C3 fuel. These engines did not see service until 1944 and were quickly followed by the 1,800 PS (1,775 hp) DB 605DB (running on B4 + MW-50 or C-3 without MW-50) and 2,000 PS (1,973 hp) DB 605DC. These engines saw widespread use in the late-war Bf 109 G-10 and Bf 109 K-4.