202B - Turbocharged Air Systems

Question 1

What five benefits do turbocharged engines serve?

Answer 1

• 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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Question 2

What must be used to cool the intake airflow on a turbocharged engine?

Answer 2

Aftercoolers or intercoolers

202b pg. 3

Question 3

Compared to a naturally aspirated engine, a turbocharged engine has what differences incorporated into its design?

Answer 3

• 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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Question 4

The turbine is what side of a turbocharger?

Answer 4

Exhaust side.

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Question 5

The compressor is what side of the turbocharger?

Answer 5

Intake air side

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Question 6

The turbine housing on a turbocharger is made of what?

Answer 6

Heavy cast iron

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Question 7

How fast could the turbine wheel on a turbocharger spin?

Answer 7

Could be well over 100000 rpm

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Question 8

In a turbocharger, what diverts some exhaust gases away from the turbine wheel as a method of controlling boost?

Answer 8

Wastegate

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Question 9

What is the turbocharger diffuser plate?

Answer 9

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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Question 10

What are some engines equipped with to temporarily supply the turbo with oil until the engine oil pump is fully operational?

Answer 10

Manual or electric oil pumps

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Question 11

What is the turbocharger wind back seal?

Answer 11

Threads on the shaft that acts as an oil seal.

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Question 12

On a turbocharger, sealing between the compressor housing and centre housing is often done by using: (2)

Answer 12

• O-rings
• RTV

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Question 13

What is the maximum restriction for the air induction system and exhaust system?

Answer 13

Air induction: 25 inches of water
Exhaust: 3 inches of mercury

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Question 14

If the engine exhaust has a blue colour, what it the likely cause?

Answer 14

Burning oil

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Question 15

If a cool-down period is not used with a turbocharger, the oil burns and ______ on the bearing surfaces?

Answer 15

Cokes

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Question 16

When checking radial play of turbine and compressor wheels with feeler blades, how many measurements should be taken?

Answer 16

Three measurements equally spaced around the wheel, between the wheel and housing.

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Question 17

When installing a turbo, what should be done before starting the engine to ensure that the turbo will not run dry of oil?

Answer 17

Pre-lube the turbo before connecting the oil line.

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Question 18

How should a turbocharged engine be properly shut down to prolong the life of the turbo?

Answer 18

1) Run engine at half speed for 3-5 minutes
2) Run engine at idle for 3-5 minutes

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Question 19

What should be done while transporting turbocharged equipment to prevent damage to the turbo?

Answer 19

Cover the end of the exhaust pipe to prevent air from spinning the turbo dry

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Question 20

Is an aftercooler air-to-air or air-to-coolant?

Answer 20

Air-to-coolant

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Question 21

Is an intercooler air-to-air or air-to-coolant?

Answer 21

Air-to-air

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Question 22

On what types of equipment are aftercoolers generally used on?

Answer 22

Stationary, off-road, or slow moving equipment where there is not a lot of airflow.

Question 23

What two problems could result from a leak in an air-to-air intercooler?

Answer 23

• Lost turbocharged pressure
• Dust could enter the engine

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Question 24

How does a wastegate control turbo boost pressure?

Answer 24

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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Question 25

What would result from a wastegate valve stuck open?

Answer 25

Low power complaint

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Question 26

What would result from a wastegate stuck closed?

Answer 26

Unregulated turbo speed which could cause damage

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Question 27

A sliding nozzle vane type turbo is what type of turbo?

Answer 27

Variable displacement turbo

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Question 28

How does a variable displacement turbocharger regulate boost pressure?

Answer 28

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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Question 29

A pivoting nozzle vane turbo is what type of turbo?

Answer 29

Variable geometry turbo

Question 30

What precautions should be observed when working with turbochargers? (7)

Answer 30

• 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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Question 31

With ambient air temp at 29C, the boosted air will increase in temperature to approximately:

Answer 31

149C

202b pg. 3

Question 32

What is a turbo diffuser?

Answer 32

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.

202b pg. 8