Focke-Wulf Fw 190A poor high-altitude performance

[Kurfürst]

Originally Posted by Kutscha

You should have mentioned Kurfurst that German engines used less boost. The highest boost, except for the penny pocket of 109ks using 1.98ata, was 1.80 ata. 1.80ata being a little less than 11lb.

Increasing the compression ratio increases the power output of the engine slightly at all altitudes, all other factors being constant; increasing the boost will increase the power output more rapidly, but only below the rated altitude of the engine (=capacity of the supercharger).

Therefore, as far as high altitude performance go, increasing the compression ratio yields power output advantages, while increasing boost doesn't, unless the supercharger is improved, too.

German engine development advanced parallel in many areas, by increasing displacement, permissable rpm and compression ratio and supercharging; Allied developments revolved around supercharging.

A comparison of the output of two-staged Allied inline engines like the Merlin and single staged German inlines with increased superchargers show that these were really two roads to similiar outputs at altitude, although I consider German powerplants more efficient overall in terms of the developments resulting in lesser bulk and more favourable fuel consumption.