In Microsoft Flight Simulator Insider, Rod Machado writes:"Under normal conditions, the engine's manifold pressure can't rise above atmospheric pressure".Assume a take-off runway at sea level and ISA standard conditions.Manifold pressure in a parked DC-3 on that runway will indicate 30 inches Hg (rounded off).Now, taking off this DC-3 from that runway, applying take-off power, the MP gauge indicates 48"Hg. So it rises +18"Hg above the actual atmospheric pressure!Thanks for any explanation.Stupido.

Engines are turbo compressed ! Just have a look to the Seneca VDidierROTW

>Engines are turbo compressed ! Just have a look to the Seneca>V>>Didier>ROTWThanks Didier! For your info I found the following to add:Engines DC-3 14 cylinder, twin-row, radial, air cooled Pratt & Whitney R-1830-92. Each engine is equipped with an integral single-speed supercharger with an impeller gear ratio of 7.15 to 1.Paddy.