Back on topic, a slight reframe of the query:
- throttle steady, maintain altitude (and therefore air pressure is same)
- change pitch to coarse, increasing load on engine, dropping prop & engine RPM
- drop in engine RPM drops RPM of supercharger impeller, decreasing amount of air/fuel forced into inlet manifold
- drop in engine RPM decreases amount of air/fuel being sucked into cylinders.
Question- is the decrease in air/fuel negative pressure at inlet to cylinders more or less than the decrease in the positive pressure of air being forced into the inlet manifold by the supercharger?
If the decrease at the cylinder end of the manifold is more, the boost gauge will read higher as the boost gauge measures increased air pressure in the inlet manifold as there is a backup of air/fuel.
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