[vanir]

Sry i cant agree because D-11&D-13 performance in game is not exacly historical and accuracy.
See sea level speed ~650km/h. The same is with Tempest 11lbs&13lbs at high alt unhistorical speed 790km/h instead 703 km/h which was never corrected.

Strange, I just tested the D-13 armed with 3x MG-151, full fuel and ammunition, flying clean on the Crimea map with a good long level run on MW-50 for 596km/h at 230m over water. This matches test figures for the historical D-9 clean and loaded at sea level.

In fact what I find is you have to dive to get listed historical speed figures for vanilla D-9s and late war Messerschmitts, or the Ta-152 and then they will sustain those speeds, but trying to achieve them following a climb regime at the 30min power setting is impossible, even after a cool down before using military power.

In fact the 30min climb setting (2600u/min DB motor) is modelled as the 5min normal military setting (which should be 2700-2800u/min), whilst any sustained climb regime needs to be done on the cruise setting (2300u/min) and best cruise is at the economy cruise setting (2000-2100u/min). To achieve normal military settings MW-50 must be used and has a 1min limit (historical is 5min for Daimlers and 10min for Jumo and BMW engines).
This instantly removes all the upper envelope performance capabilities during mid-range performance, in other words sustained combat performance of these types and it is a common theme among K-4, G-10, D-9, 152 and all German late war piston fighters modelled in vanilla il2. It is completely inaccurate according to documentation provided by engine or aircraft manufacturers of these types. It ridiculously disadvantages late war Luftwaffe piston engine pilots in game compared to contemporary Allied aircraft which not only do not suffer any of these mid range performance disadvantages but in some like the P-47 you can set full military power from take off until the tanks run dry with no ill effect or overheating, the exact opposite extreme in favouritism and highly questionable modelling accuracy.

For this test I made a shallow dive on minimum power to 200m to keep my speed below 500km/h, levelled and maintained the cruise setting for a while and then accelerated using military power and MW-50, then just stayed there for a few minutes topping out at around 595km/h fairly quickly but not accelerating further at the maximum power/boost setting.

One of the things I immediately noticed of course was that the military setting using MW-50 seemed to adhere to the 10 minute Focke Wulf limit for combat use before cool down rather than overheating the engine in about 1 minute for the vanilla D-9, which runs way too hot to begin with and has very poor mid-range and cruise/climb performance. So the D-13 certainly feels far and away more powerful than the D-9 modelling, it is a totally more powerful aircraft to fly because of this, yet what we are talking here is mid-range flight characteristics and not absolute speed capabilities which still remain very similar at this height.

So firstly it is not the speed capabilities which are the cause of the issue here, it is the mid-range combat performance in vanilla FMs for these types. They do not match any independent and well researched or primary source celebration, whilst making selective and highly arguable assertions about genuine wartime performance throughout the flight envelope.