FW190-D9 Engine Boost

[CUJO_1970]

Why are flight tests in December 1944 showing full boost 1.8ata? What is written in this thread is that in winter/cold months the Jumo should only develop something like 1.6 ata because of mass flow regulator/higher air density in winter...but this is a flight test on December 15, 1944 with boost 1.8 ata:

 

 

They test other 213 motors at even higher than 1.8 ata....so if the Jumo 213 could only reach 1.5/1.6 or whatever ata in winter, why are these tests in winter then showing 1.8 ata and sometimes more? From what I can tell average low in December in Germany is 31.75 to high of 37.5 degrees.

 

Summer I see 76/77 as high? https://weatherspark.com/countries/DE

 

 

 

 

Edited November 1, 2022 by CUJO_1970

[ZachariasX]

Maybe they are referring to the power setting much rather than the actual pressure in the manifold.

[JtD]

This isn't a test report, it's a compilation of calculated data. The A-8 for instance is copy and paste straight out of a data collection which is labelled "calculated flight performances" from early 1944. Flight tests for some of the later models noted on that sheet hadn't even been carried out at that time, it's just projected performance.

 

Germans typically referenced power settings by maximum boost pressure obtainable, and under standard conditions for the Jumo213A at that time this was 1.8ata. But that's just a label and that's what is there.

[CUJO_1970]

On 11/1/2022 at 2:19 AM, ZachariasX said:

Maybe they are referring to the power setting much rather than the actual pressure in the manifold.

It turns out the Jumo-213 does not require 1.8 to produce full power in cold winter months. That’s what I was not understanding, until it was explained to me by someone who definitely understands the motor. 

 

My assumption was that lower ata=lower power in winter months. This is not the case with the Jumo-213. It is really a fascinating and clever system. 

[ZachariasX]

7 hours ago, CUJO_1970 said:

It turns out the Jumo-213 does not require 1.8 to produce full power in cold winter months.

This is the case with all such engines. In cold, dry air, you need less manifold pressure for the same power output than in warmer, more humid conditions. Merlins, Allisons etc. get boosted in winter and throttled in summer versus standard conditions. The mass flow regulator (e.g. in the Jumo) evens out those differences and you directly see those differences on the ata gauge. It makes the Jumo, relatively speaking, more competitive in summer and less competitive in winter.

 

This is also why I consider concluding that engine X can pull Y MAP in New Guinea would be able to also pull Y MAP during Russian winter to be a tad optimistic. Plus it means that overboosting in New Guinea doesn‘t produce the results you‘d get under calibrated conditions.

 

Especially in less overpowered aircraft (but it concerns all aircraft), this also manifests in the problematics of the density altitude.