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Davis0079
Oct-20-2013, 08:42
noticing that the 109e-4s intake pressure drops quite a bit at high alt (6000m)...I understand that high alt=low pressure, but isnt the 109's bad ass auto adjusting supercharger suppose to be able to keep up with this change...at full throttle, 6000m, 2500rpm, I have close to 1.0ata.....the performance seems to be there, bout 400km in level flight...I'm just curious as to why the manifiold pressure seems low...


...not a expert on the subject....maybe at that altitude thats the best the supercharger can do...or am I missing something???



edit...at sea level the air pressure is 14.7....at 10,000ft its 10.1...and 20,000 its 6.75....looking at the math, is the 109 supercharger only making 10 pounds of boost....I know ppl with Regal Grand Nationals w/ upgraded turbos that make 27 lbs boost at sea lvl on an engine that would run at -14 lbs if naturally aspirated....I thought the 601 supercharger was a little better then the numbers I'm reading..

..maybe I'm forgetting that this engine was made in the late 1930s...

Kwiatek
Oct-20-2013, 08:50
Becasue DB601A could keep 1.3 Ata only till 4.5 km (FTH) then ATA drop rapidly.

FTH for MErlin III was higher ab. 18 500 ft ( ab. 5.5 km ) thats why Merlin III had more power at higher alts then DB601A.

And your 400 kph is probably IAS ( from speed guage) - TAS is much higher at these alts.