Piper Navajo PA-31 Service Manual page 477

Wastegate and Actuator
(Exhaust By-Pass)
PIPER NAVAJO SERVICE MANUAL
8-29a. INSTALLATION OF OIL COOLER.
a. When installing fittings in the oil coolers, care should be used to prevent excessive torque being
applied to the cooler. When a rectangular fittings boss is provided, backup wrench should be used, employing
a scissor motion, so that no load is transmitted to the cooler. When the oil cooler has a round fitting boss, care
should be taken not to permit excessive torque on the fittings.
b. If a pipe thread fitting is used, it should be installed only far enough to seal with sealing compound.
c. Apply Lubon No. 404 to all male pipe thread fittings; do not allow sealant to enter the system.
d. If fitting cannot be positioned correctly using a torque of 10 to 15 foot-pounds, another fitting should
be used.
e.
After installation, inspect the cooler for distorted end cups.
f. Run-up engine. After run-up, check for oil leaks.
8-30. ENGINE TURBOCHARGER.
The turbocharger system requires little attention between turbo over-
hauls. However, it is recommended that the items outlined in the Inspection Report of Section III be checked
during required inspection intervals. Should trouble occur, refer to the Troubleshooting Table in this section
and seek out the possible cause. Do not break the clamp seal joining the turbine and compressor units.
8-30a. TURBOCHARGER
NOMENCLATURE. Many unfamiliar terms may appear on the following
pages of this manual. An understanding of these will be helpful, if not necessary, in performing maintenance
and troubleshooting. The following is a list of commonly used terms and names as applied to turbocharging
and a brief description.
TERM
MEANING
Supercharge
To increase the air pressure (density) above or higher than ambient
conditions.
Supercharger
A device that accomplishes the increase in pressure.
Turbo-supercharger
More commonly referred to as a "Turbocharger" this device is driven by a
turbine. The turbine is spun by energy extracted from the engine exhaust
gas.
Compressor
The portion of a turbocharger that takes in ambient air and compresses it
before discharging it to the engine.
Turbine
The exhaust driven end of the turbocharger unit.
The wastegate is a butterfly type valve in the exhaust by-pass which,
throughout its travel from open to closed, allows varied amounts of
exhaust gas to by-pass the turbine, controlling its speed, hence the output
of the compressor. The actuator is operated by a hydraulic piston op-
erated by engine oil and cylinder with the piston linked to an arm on the
butterfly valve shaft.
Reissued: 10/12/79
POWER PLANT
213