Absolute Pressure Relief Valve Removal; Absolute Pressure Relief Valve Installation; Exhaust Bypass Valve Adjustment - Piper PA-44-180 SEMINOLE Maintenance Manual

REMOVAL OF ABSOLUTE PRESSURE RELIEF VALVE.
1. Remove the four screws and washers which secure the relief valve to the duct.
2. Lift the relief valve assembly from the duct.
3. Remove the O-ring from the seating surface of the relief valve mounting flange on the duct.
INSTALLATION OF ABSOLUTE PRESSURE RELIEF VALVE.
1. Install a new O-ring and position the relief valve on the mounting flange of the duct.
2. Install the washers, screws and safety wire.
EXHAUST BYPASS VALVE.
The exhaust bypass valve is mounted on the crossover tube between the exhaust turbine inlet duct and the
tailpipe. This ground adjustable unit is set to a predetermined value, thus bypassing a fixed amount of exhaust
gas away from the turbocharger turbine limiting the turbocharger speed and the degree of compression of the air
leaving the compressor.
ADJUSTMENT OF EXHAUST BYPASS VALVE.
Before making any adjustments to the exhaust bypass valve, perform a complete
inspection of the power plant system.
The exhaust bypass valve is preset at the factory so as to reach critical altitude at 12,000 feet density altitude.
full throttle and 36.5 inches hg. manifold pressure. Adjustment should be accomplished only if the critical
altitude cannot be reached and the powerplant system has been thoroughly checked.
1. After removing the upper cowling to gain access to the exhaust bypass valve, remove the safety wire from
the valve.
2. Adjust the exhaust bypass valve initially so that there is 1/4 inch between the bolt head and the top of the
jam nut.
3. If critical altitude is not obtainable at the initial setting, further adjustments should be made as follows:
a. To increase critical altitude turn bolt clockwise. To decrease turn bolt counterclockwise.
b. For each flat turned of the adjusting bolt head the critical altitude will change 200 feet.
4. Upon completion of adjustments, safety wire the adjusting bolt and reinstall the cowling.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— Note —
— END —
3J14
8 1 - 2 7 - 0 0
Page 81-12
Revised: May 15, 1989