See RAM Maintenance Tip Manifold Pressure and Prevent Exhaust Leak Damage. Do not forget to inspect the air filter canister and alternate air source for integrity. Since the majority of suspected turbocharging system problems are the result of an induction or exhaust leak, leakage inspection of the intake and exhaust system should be included in the maintenance of the turbocharging system. Inspect the plunger roller for freedom of movement. Inspect the control arm bushing for wear. Inspect the pressure controller for evidence of oil leakage. Lubricate the wastegate butterfly shaft at each oil change per RAM Maintenance Tip Turbocharger Wastegates. Inspect the linkage for freedom of movement and the arm spring for security. Inspect the wastegate butterfly valve for warpage and security, and inspect the butterfly shaft bushings for condition. RAM recommends that the turbochargers receive a soak of the oil seal at least on an annual inspection to eliminate any coking of the seal. Limitations on cracks can be found in the Airesearch overhaul manual. Regular inspection intervals should include inspection of the turbocharger housing for condition and security. When the controller senses excessive compressor discharge pressure, the opposite action occurs. This raises the turbine/compressor shaft speed and the compressor discharge pressure. When the controller senses insufficient compressor discharge pressure, a poppet valve in the controller moves towards the closed position raising the oil pressure in the actuator closing the bypass valve and forcing more exhaust gas through the turbocharger turbine. The wastegate is actuated by pressurized engine oil that first flows into the actuator via a restricting orifice or capillary tube, then it flows out of the actuator to the controller, then it dumps into the engine crankcase.
The exhaust gas flow is modulated by diverting excess exhaust gas through the wastegate. The discharge pressure of the turbocharger compressor is regulated by controlling the flow of exhaust gases through the turbocharger turbine. The system consists of a turbocharger, a bypass valve or wastegate, a pressure controller, and a direct acting absolute pressure relief valve. 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.
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