![]() ![]() (Power is set by throttle on a fixed prop whereas power is set by throttle and RPM control on a CSU). Because that also reduces the power, it is still consistent with all of the above. The MAP sensor measures the absolute pressure inside the intake manifold of the engine. This range will vary depending on the type of system, the age of the pipes, and other factors. The typical manifold pressure for natural gas is between 60 and 80 psi. The PCM uses this input, as well as others, to calculate the correct amount of fuel to inject into the cylinders. A manifold pressure is the pressure in the main line of a gas distribution system. On the other hand, with a fixed pitch prop if you close the throttle the MAP and RPM will both reduce. The Manifold Absolute Pressure (MAP) sensor is used by the Powertrain Control Module (PCM) for engine load input. ![]() The system consists of a turbocharger, a bypass valve or wastegate, a pressure controller, and a direct acting absolute pressure relief valve. Hence the power setting table of an aircraft with CS prop gives different combinations of MAP and RPM resulting in the same power - some with higher revs and lower MAPs than others. The function of an aircraft turbocharger system is to maintain a desired manifold pressure at a given throttle setting regardless of varying conditions of ambient air temperature and pressure. A key concept is that torque x RPM is proportional to power. ![]() The manifold pressure will in turn affect the pressure in the cylinder which is effectively your torque. When you close the throttle the MAP drops and vice versa. It could increase or decrease, depending on throttle position and load as well as RPM. More generally, the MAP does not necessarily increase with reduction in RPM. It is seen in a mag check or when exercising the prop. If you do not move the throttle and the RPM drops for some reason, yes the MAP will increase. I should apologise for my earlier poor answer due to not reading the question properly. ![]()
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