BMW801D-2

[jugggo]

Ok I just looked through the entire engine section and still get blown away by the amount of input that the community gives on this site and the wealth of knowledge!!

Here is a problem that I am having regarding the 801D-2 motor. Just about every power curve or graph shows the 1.42 ata rating for power but nothing seems to show data for the D-2 power. I have seen 2060PS at SL for the 1.65ata but that's it nothing at various altitudes. Some show speed and climb performances for the 1.65 and 1.58ata settings. I have one power chart that shows them but hard to make out which setting is what. One can only "assume". Does anyone know or have this mysterious power curve?

I am attaching the graph and I can assume that starting at the top is 1.65 then 1.58 then 1.30? Or 1.20? Etc any input would be greatly appreciated.

 

[tomo pauk]

The title says that engine power shown is for total engine power (= net engine power + power used for the cooling fan). Fan used max ~70 ps when supercharger was in low gear, ~50 PS in high gear. Max manifold pressure ('Ladedruck') in 1st (low) gear was 1.58, in 2nd (high) gear was 1.65, those settings avaiable from some time in second half of 1943. Above 1 km, the supercharger will give a decreasing amount of manifold pressure. Then, at ~2.7 km the 2nd S/C gear is engaged, making the mentioned manifold pressure of 1.65 ata up until ~4.5 km, above that altitude again the S/C will provide ever lower manifold pressure. All altitudes assume no ram effect is present (ie. static engine).
The graphs available from here (link, scroll down to the speed and RoC graphs' links) are bit more clear, they show net engine power (the power available for the prop), also the manifold pressure vs. altitude is easier to deduce.

 

[jugggo]

Now the link you gave shows (if I am correct) say at 2.75km(dash line to the right of Ladedruck ata) is when the 1.65ata boost automatically comes on? If that is the case (again if I am reading it correctly) that is showing @ 2.75km it is 2150PS (2121hsp)

Am I reading it correctly?

 

[tomo pauk]

You are looking at 'Ladedruck' (manifold pressure graph). The 'Motorleistung' (engine power) graph shows eg. 1900 PS at 0.4 km (Ladedruck = 1.58 ata), 1650 PS at ~5.2 km (Ladedruck = 1.65 ata). Dashed lines are for 'Sonderleistung', ie. special power setting, achieved when boost is greater than 1.42 ata in this case. At ~2.75 km, max power in overboost/Sonderleistung is ~1640 PS.
Values on that graph are for maximum ram, ie. max speed, unlike for the graph you've posted.

 

[jugggo]

So confusing lol SO if boost is greater then 1,42 then both of 1,58 and 1,65 would both be considered Sonderleistung?

So the first chart I posted is correct top line 1,65 then below is 1,58 etc?

 

[tomo pauk]

So confusing lol SO if boost is greater then 1,42 then both of 1,58 and 1,65 would both be considered Sonderleistung?

Yes.

So the first chart I posted is correct top line 1,65 then below is 1,58 etc?

Nope. The manifold pressure is 1.58 ata from sea level to ~1 km, then it drops down to maybe 1.2 ata, and then, once 2nd S/C gear is clutched in (at ~2.75 km at your graph), the manifold pressure is 1.65 ata. It retains that value up to ~4.5 km at your chart, and then again dropping down as altitude increases. Please note again that max manifold pressure when the S/C is in low gear is 1.58 ata, the 1.65 ata is maximum for high gear.
All of this is for the top 'cranked' line, for 2700 rpm.

 

[jugggo]

Also the first graph "true airspeed" is the smaller shaded area 1,58ata and the largess shaded area 1,65ata being represented as showing the gain or increase of power/speed?

 

[tomo pauk]

Increase in the true air speed - basically, the Fw 190A-5 with 'Sonderleistung' was supposed to do 680 km/h at ~5.2 km, per that graph.

 

[jugggo]

Ahh so 1,58 was takeoff power 1-3minutes and the 1,65ata was "Special Emergency" at 10 minute max. So is 1.42ata still "MIL/climb power for 30minutes and 1,15-1,20 max continuous with the 801D-2?

 

[tomo pauk]

Manifold pressure for take off ('Startleistung', a part of 'Start- und Notleistung' power setting; 'Notleistung' = emergency power setting; 3 min initially) was still 1.42 ata at 2700 rpm. Special emergency (called 'erhoehte Notleistung') was indeed cleared for 10 min, with remark of 1st December 1943:
But the oil temperature has to be regarded as a criterion and only a larger test basis can make a final decision possible.

'Steig- & Kampfleistung' was at 1.32 ata max, 2400 rpm, 30 minutes, even though the 2700 rpm line on the chart at wwiiperformance graph notes 2700 rpm and applicable boost as 'erhoehte Steigleistung'
Both 1.58 and 1.65 ata, on 2700 rpm, are 'special emergency' - more than 1.58 ata was not allowed in 1st supercharger gear.

 

[jugggo]

I think when I finally figure out this engine and all its off the wall quirks I am going to make a chart showing all the ata, PS at whole number km lol to hep other lost folks like myself in this beast of information. Again many thanks!!!

 

[tomo pauk]

(a polite nudge for that DB 605 stuff...)