I had to canvas my bomber pilots to get a definitive answer from a pro regarding turbos. here's one response:
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Turbocharger boost was necessary to get a fully loaded B17 into the air. Using 100 octane gas we could boost manifold pressure to 54 inches of mercury, which is approximately double normal sea level atmospheric pressure . Control was automatic, preset by electronic setting prior to takeoff. I believe 54 inches of mercury was rated as "War Emergency Power" Models before G or H had unreliable hydraulic controls.
Best that an 81 year-old, broken down old pilot can remember.
Hope it helps
Bob
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I didn't know there was an "H" model.
Thanks,
Gerd