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1. Improperly adjusted wastegate valve. You may need to adjust the wastegate
on new engines to reach critical altitude. On Continental TSIO360 E,EB,F,FB,G,GB
and Continental LTSIO360 E,EB engines adjust critical altitude in accordance with Continental
Service Bulletin M84-6 Revision 1 or latest edition. This procedure involves
the following: A. Takeoff rated manifold pressure and rpm are obtained
at approximately 40 degrees throttle travel. B. Engine critical altitude
adjustment is controlled by a ground adjustable screw-type wastegate on
the exhaust bypass pipe at the turbocharger location. This adjustment is
preset and only minor changes should be required. Adjustment is as follows:
Approximately 1000 feet increase in critical altitude per one revolution
of screw clockwise; approximately 1000 feet reduction in critical altitude
per one revolution of screw counterclockwise. Unlock and lock jam nut before
adjustment.
2. Leaky exhaust system. Inspect for any white exhaust stains on the
exhaust system.
3. Malfunctioning turbocharger. Remove exhaust or air inlet connections
and check rotor assembly for possible rubbing on housing, damaged rotor
or malfunctioning bearings. Spin turbine by hand to check for free rotation.
4. Wastegate does not go to full closed position. Cap off the actuator
discharge, apply 60-65 pounds of oil pressure to inlet. When the wastegate
closes, measure the clearance between butterfly and housing. Lubricate
shaft with Mouse Milk.
5. Suck-open door on compression discharge housing not fully closed
or door gasket damaged (TIO-540 engines).
6. Faulty Absolute Controller. If engine loses power, consider leaking
poppet valve or oil leaking into induction system because of broken boot
bellows. Remove controller and check for oil in induction housing.
7. Faulty density controller. The density controller is used to regulate
wide-open throttle power (and manifold pressure). When density reaches
a level at which spring tension is overcome, the controller outlet port
opens.
8. Improperly adjusted controllers.
9. Insufficient oil pressure to close wastegate. Pressure required to
close wastegate varies with model but is generally between 15-30 psi.
10. Improper adjustment of density controller on Lycoming T/LTIO- 540
engines. Full rated power is set by adjusting the density controller per
Lycoming Service Instruction 1187G or latest edition.
11. Aerostar, failed waste-gate actuator. Failed actuator piston rings.
If the drain line is routed to the crankcase, then no oil loss is apparent.
The first symptom is loss of critical altitude. Disconnect the actuator
drain line from the crankcase, plug the hole in the case, and wire a jar
so the line drains into the jar. A short test fight will put oil into the
jar if the actuator rings are bypassing oil. On Cessna's you can usually
put a Q-tip up the drain line and see if it comes out clean or not.
12. Leak in intake system allowing hot cowling air into induction system. If
the air induction system is not getting all of its air from outside the cowling
then the engine is operating at higher intake air temperature than normal. All
air for combustion should be coming from outside the cowl. Inspect for leaks in
the transaction duct from the air box to the air scoop. Confirm filter cover to
air box fit snug. Check the air box magnets and the alternate air door
hinge.
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