Boosting Your
Knowledge of…
TURBOCHARGING
Randy Knuteson – Analytical / Air Safety
1905 – Patent by Dr. Alfred J. Buchi
Historical Perspective:
1905 – Sulzer Bros. designs first turbo
1910 – G.E. begins manufacturing turbos
1915 – First turbo diesel engine
1918 – Dr. Sanford
Moss altitude tests a
350 hp turbocharged
engine.
Historical Perspective:
1920 – New altitude record in a LePere
Bi-Plane – 33,113 feet!
Historical Perspective:
1921 – John Macready's flight to 40,800' in an
open cockpit Lusac 11, Lepere biplane.
Turbo-Supercharged B-36
Six 28-Cylinder Engines
Without Turbos – 90
Cylinders per Engine!
ENGINE HORSEPOWER
DEPENDS ON…
…The amount of fuel and air an engine
burns.
 …The density of the charge, not the
volume.
So…actual power is determined by
the MASS of air consumed.
PRINCIPLES OF
TURBOCHARGING
Sea-level air density = 0.0765 lb. cu. ft.
At 10,000 ft. air density = 0.0565 lb. cu. ft.
A Naturally-Aspirated Engine
100 hp @ sea-level = 73.9 hp @ 10,000 ft.
WHY TURBOCHARGE?
Power diminishes with an increase in altitude.
Gain more power and increase engine
efficiency without enlarging the powerplant.
Recapture the heat energy normally wasted
out the exhaust.
GOAL – Convert Exhaust Energy into Manifold Pressure
A TURBOCHARGER IS AN…
…“AIRPUMP”
powered by the
unused heat
energy normally
wasted out the
exhaust.
Routing of exhaust and compressor
discharge air
Filtered
ambient
air inlet
Spent
exhaust
gases
overboard
Compressor
outlet
Exhaust gas inlet
(T.I.T.) from the
combustion process
1650° F
As high as
125,000
RPMs!
AME Maintenance Seminar
TURBOCHARGING DEFINITIONS
Turbocharging
BOOSTED – HP increase (31-45”MAP)
Turbo-Normalizing
NORMALIZED – Maintains sea-level
performance (29.5” MAP) at altitude.
TURBOCHARGING
DEFINITIONS
Upper Deck Pressure

From compressor discharge to the throttle
plate.
Manifold Pressure

From the throttle plate to the cylinder
intake port.
Sludge build-up in
the “wedge” can
decrease the oil
pressure feeding
into the bearing
and shaft
AME Maintenance Seminar
30-60
PSI
Piston rings keep air and exhaust
pressures out of the center housing
TURBO COMPONENTS:
COMPRESSOR STAGE (Cold Side)
Discharge Air
Volute shape –
converts velocity
energy into
pressure energy
Bonanza Pilots Turbo Talk
Power
increase
MAP
increases
TURBO “RUN-AWAY”
COULD EXCEED MAXIMUM
ENGINE OPERATING LIMITS!
Increased
compressor
discharge
Exhaust
volume
increases
Turbo begins
to spin faster
Decrease
power
MAP
decreases
Compressor
discharge
decreases
Decreased
exhaust
flow
Turbo slows
down
4 BASIC SYSTEM COMPONENTS
Turbocharger
Controller
Wastegate
Absolute Pressure Relief Valve (PRV)
4 BASIC SYSTEM
COMPONENTS
Aneroid
Bellows
Upper Deck
Pressure
Engine Oil from
Wastegaate
Actuator
Throttle Controlled
Cam
Oil restrictor
Valve
Oil Return to
Engine
4 BASIC COMPONENTS
Wastegate (Exhaust Bypass Valve)
Butterfly
Valve
Piston
Oil Outlet to
Controller
Oil Inlet
Drain Port
4 BASIC SYSTEM
COMPONENTS
Absolute Pressure
Relief Valve (PRV)
Spring and
Bellows Assy
Valve Face
Valve Seat
Escape path for
excess Upper Deck
Air Pressure
Turbo output
pressures must
be regulated.
Without a control
system, the
turbocharged engine
would Be extremely
unstable.
TURBOCHARGERS ARE
SENSITIVE TO:
Insufficient lubrication
Foreign object damage
Extreme temperatures
INSUFFICIENT
LUBRICATION…
…RESULTS IN:


Bearing damage that causes an increase in
the orbital motion of the turbine shaft.
Turbine and compressor wheels begin to
contact their respective housings.
CONTAMINATED
LUBRICATION RESULTS IN:
Damage to bearing(s)
Collateral damage to turbine and
compressor housings
Full floating bearings require 30 PSI
minimum at inlet (3 GPM)
 Engine Oil should be changed every 25-35
hours in a turbocharged engine.
Lubricating Oil
Recommendations:
Lycoming SI 1014M – “All turbocharged
engines must be broken-in and operated
with ashless dispersant oil only.”
TCM M87-12 Rev 1 – Straight Mineral Oil
(MIL-L-6082) may be used – not to exceed
25 hours or 6 months of operation.
VERIFY TURBO CONDITION
Does the shaft spin freely?
VERIFY TURBO CONDITION
Wheels should not contact housing.
VERIFY TURBO CONDITION
Use a light source to
carefully examine the
condition of the leading
edges of the Turbine
Wheel blades.
Check inducer
blades for
damage
FOREIGN OBJECT DAMAGE
Bolts, valves, and rocks will break
pieces from the blades or “machine”
them down.
Abrasive matter (sand, dirt) will wear
away the underside of the blades.
Soft material (shop rags) will bend the
compressor blades backwards.
Avoiding Turbo Oil Leaks
Drain ports must point
down. (not more than
35 degrees from vertical
centerline)
Drain line should slope
entire length (no “sink
traps”).
Check hoses for internal
de-lamination.
No sludge at outlet
From “coking” of
bearing housing.
Restriction or faulty
check valve(s)
Overspeed/Overshoot/Overboost
Overspeed

Operating an engine above it’s rated speed
or RPM.
Overshoot

Automatic controls can’t respond quickly
enough to the inertia of the turbocharger
speed as it increases when the throttle is
rapidly advanced.
Overspeed/Overshoot/Overboost
Overshoot

Lycoming says:
“If overshoot does not exceed 2 inches and 3
seconds duration, it may be disregarded.”
Overspeed/Overshoot/Overboost
Overspeed
Overshoot
Overboost

Occurs when the manifold pressure
exceeds the limits at which the engine was
tested and FAA certified.
OVERBOOST – CAUSED BY:
Rapid throttle movement
Exhaust By-Pass Valve fails to open.
Sticking Wastegate
Air in the oil feed to the controller
PRV (pop-off valve) fails to open at
predetermined crack point.
“UNACCEPTABLE OVERBOOST”
TCM SB67-12

“OVERSHOOT”
 3-6
/ “OVERBOOST”
INCHES – Check System,
Adjust or Replace Malfunctioning
Components.
“UNACCEPTABLE OVERBOOST”
LYCOMING MSB-369J



“Not exceeding 5 inches Hg. or 10
seconds” – Normal 50 hour inspection
required.
“Not exceeding 10 inches Hg.” – Complete
engine disassembly and inspection.
“Over 10 inches Hg.” – Complete engine
Overhaul and crankshaft replacement.
“ACCEPTABLE OVERBOOST”
LYCOMING MSB-369J

“Momentary” - not exceeding 3 inches Hg.
for 5 seconds
Log Book entry required.
• Maximum manifold pressure reached.
• Duration of overboost
• Cylinder head temperature
• Ambient air temperature
• Pressure altitude
“ACCEPTABLE OVERBOOST”
LYCOMING MSB-369J


Visual inspection of compressor and
turbine wheels
Manually check for excessive movement of
turbine shaft in the journal bearings.
CHECKING BEARING CLEARANCES
Radial Bearing
Check
0.003-0.007
0.004-0.009
Axial End Play
Bearing Check
Maintenance of Turbo System
Preflight – Visual Inspection


Check for security of turbo mountings and
connections.
Inspect for evidence of oil leakage, air
leakage, or exhaust leakage.
Maintenance of Turbo System
50 and 100 hour inspections:




Inspect the hoses and tubing of the air
intake system.
Check for leakage due to cracks, damaged
gaskets, loose clamps or connections.
Restrictions due to kinks, collapsed hoses,
or dented tubing.
Inspect for exhaust leakage.
Maintenance of Turbo System
50 and 100 hour inspections:
Inspect the torque on
all V-band clamps
Maintenance of Turbo System
50 and 100 hour inspections:




Check oil feed and return lines.
Unusual noises or vibration.
Observe the engine exhaust.
FOD damage to wheels or evidence of
contact with housings.
Turbo Cool Downs
Allow for a two to four minute cooldown period.
CHT – drop 50 degrees from last power
reduction
EGTs – 500 degree drop from Cruise
Temps.
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