Some time ago I made some tests in IL2 COD, and became to the conclussion that the info that the developers used was for the engine DB601A-1 bei altem lader (VDH/FTH 4 km) (old compressor).
Those tests were made with patch version 145.50.
I never tested again in the actual patch but I reckon it remains the same.
The same engine with the new compressor (Bei neuem lader) with 13 blades,
DB601A-1 bei neuem lader** (VDH/FTH 4,5 km) gave better performance in RL.
See the graphs below, red curve is my test, fits pretty accurately with the specifications for the engine with the older compressor.
OLD COMPRESSOR
NEW COMPRESSOR
