I have noticed high manifold pressure and the engine is easy to overboost. What are the possible reasons?
Although each turbocharged airplane is a little different, the likely causes revolve around the pressure relief valve or the exhaust bypass valve. The relief valve aneroid bellows may be faulty or out of calibration. The exhaust bypass valve is faulty either due to blockage of oil pressure or a mechanical failure. A poppet type (ball) exhaust bypass valve will sometimes stick on its seat leaving it in the closed position. A malfunctioning rate controller can cause the same conditions if it fails to properly sense a rapid increase in compressor discharge thus leaving the valve closed.
