202B - Turbocharged Air Systems Flashcards
What five benefits do turbocharged engines serve?
- Can operate at higher altitudes
- Increases power output without increasing weight
- Increases power without increasing size
- Compensates for varying load demands
- Reduces exhaust gas emissions
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What must be used to cool the intake airflow on a turbocharged engine?
Aftercoolers or intercoolers
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Compared to a naturally aspirated engine, a turbocharged engine has what differences incorporated into its design?
- Lower compression ratio
- Changed camshaft and valve timing
- Retarded injection timing
- Increased fuel injector and/or pump size
- Crankcase often vented to air intake, but could be vented to atmosphere
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The turbine is what side of a turbocharger?
Exhaust side.
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The compressor is what side of the turbocharger?
Intake air side
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The turbine housing on a turbocharger is made of what?
Heavy cast iron
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How fast could the turbine wheel on a turbocharger spin?
Could be well over 100000 rpm
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In a turbocharger, what diverts some exhaust gases away from the turbine wheel as a method of controlling boost?
Wastegate
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What is the turbocharger diffuser plate?
Angled vanes that increase the efficiency of the turbocharger by precisely and smoothly directing the boost air into the intake manifold.
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What are some engines equipped with to temporarily supply the turbo with oil until the engine oil pump is fully operational?
Manual or electric oil pumps
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What is the turbocharger wind back seal?
Threads on the shaft that acts as an oil seal.
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On a turbocharger, sealing between the compressor housing and centre housing is often done by using: (2)
- O-rings
- RTV
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What is the maximum restriction for the air induction system and exhaust system?
Air induction: 25 inches of water
Exhaust: 3 inches of mercury
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If the engine exhaust has a blue colour, what it the likely cause?
Burning oil
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If a cool-down period is not used with a turbocharger, the oil burns and ______ on the bearing surfaces?
Cokes
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When checking radial play of turbine and compressor wheels with feeler blades, how many measurements should be taken?
Three measurements equally spaced around the wheel, between the wheel and housing.
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When installing a turbo, what should be done before starting the engine to ensure that the turbo will not run dry of oil?
Pre-lube the turbo before connecting the oil line.
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How should a turbocharged engine be properly shut down to prolong the life of the turbo?
1) Run engine at half speed for 3-5 minutes
2) Run engine at idle for 3-5 minutes
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What should be done while transporting turbocharged equipment to prevent damage to the turbo?
Cover the end of the exhaust pipe to prevent air from spinning the turbo dry
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Is an aftercooler air-to-air or air-to-coolant?
Air-to-coolant
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Is an intercooler air-to-air or air-to-coolant?
Air-to-air
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On what types of equipment are aftercoolers generally used on?
Stationary, off-road, or slow moving equipment where there is not a lot of airflow.
What two problems could result from a leak in an air-to-air intercooler?
- Lost turbocharged pressure
- Dust could enter the engine
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How does a wastegate control turbo boost pressure?
Senses boost pressure and allows exhaust gasses to bypass the turbine wheel.
Sets the max boost pressure and prevents turbo over-speed.
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What would result from a wastegate valve stuck open?
Low power complaint
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What would result from a wastegate stuck closed?
Unregulated turbo speed which could cause damage
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A sliding nozzle vane type turbo is what type of turbo?
Variable displacement turbo
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How does a variable displacement turbocharger regulate boost pressure?
By extending or retracting the nozzle to cover and uncover the fins.
Extending the nozzle = more boost and back pressure
Retracting the nozzle = less boost and back pressure
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A pivoting nozzle vane turbo is what type of turbo?
Variable geometry turbo
What precautions should be observed when servicing turbochargers? (7)
- Pre-lube the turbo
- Cap all openings to prevent dirt entry
- Check radial and axial play
- Check turbine & compressor wheels spin freely
- Align clocking pins or marks for proper orientation
- Use the proper sealing compound
- Torque and use new lockplates/lockwire
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With ambient air temp is at 29C, the boosted air will increase in temperature to approximately:
149C
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What is a turbo diffuser?
A plate in the compressor side that uses angled vanes to increase the efficiency of the turbo by precisely and smoothly directing the boost air into the intake manifold.
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What type of transmission reduces side fumbling through the use of six hydrocoptic marzlevanes fitted to the ambifacient lunar waneshaft?
