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HET2 > 202A - Air Induction & Exhaust > Flashcards

202A - Air Induction & Exhaust Flashcards

1
Q

What is the required air to diesel ratio?

A

20 lbs air to 1 lb diesel

202a pg. 2

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2
Q

What are five main purposes of the air induction system?

A
  • Clean the air supply
  • Silence the airflow
  • Provide sufficient airflow
  • Cool the air
  • Allow extra airflow when used with turbos

202a pg. 3

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3
Q

What are the two main design types of engine air filter systems?

A
  • Pleated paper filters
  • Oil bath

202a

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4
Q

What is used to quiet the engine intake air flow?

A

Air silencers. Either as a standalone unit or as part of other air filter components.

202a pg. 4

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5
Q

At what inlet air temperature is maximum engine performance achieved?

A

Less than 33 C (90F)

202a pg. 5

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6
Q

What happens to inlet air temperature as it’s compressed?

A

Temperature rises

202a pg. 5

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7
Q

Air density increase as temperature:

A

Decreases

202a pg. 5

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8
Q

What two factors affect the amount of air drawn into a cylinder of a naturally aspirated engine?

A
  • Amount of partial vacuum created by piston intake stroke
  • Amount of atmospheric pressure

202a pg. 6

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9
Q

When the intake air is at atmospheric pressure, the engine is said to be:

A

Naturally aspirated

202a pg. 6

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10
Q

What is the volumetric efficiency of a naturally aspirated engine?

A

75% - 85%

202a pg. 6

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11
Q

What factors limit volumetric efficiency? (7)

A
  • Engine speed (higher speed results in less time for air to enter cylinder)
  • Air humidity
  • Air temperature
  • Altitude
  • Cylinder liner & ring condition
  • Intake valve adjustments and lobe condition
  • Air filter and tubing condition
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12
Q

Is a dirty air filter more or less efficient?

A

Air filter is more efficient. (Engine is not, but the filter itself is more efficient at filtering the air to smaller particle size)

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13
Q

What volumetric efficiency percentage could a turbocharged engine achieve?

A

110%

202a pg. 7

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14
Q

What is an air filter pre-cleaner?

A

Device used to remove up to 80% of the large particles from the air before it enters the main section of the air cleaner to prolong the life of the main filter.

202a pg. 9

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15
Q

What percentage of the larger particles does an air filter pre-cleaner remove?

A

80%

202a pg. 9

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16
Q

What are some pre-cleaners designed with as a means of separating heavier particles into a dust collection bowl?

A

Designed with angled vanes

202a pg. 10

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17
Q

What do angled vanes do in an air pre-cleaner?

A

Spin the air to fling the heavier particles outward and into a dust collection bowl.

202a pg. 10

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18
Q

Are dust ejection systems on air cleaners designed to be operated manually or automatically?

A

Will automatically open when engine is running to eject particles. Can be removed manually though in cold weather to clean.

202a pg. 10

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19
Q

How should one-way air filter ejector valves be oriented?

A

Pointing downwards

202a pg. 10

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20
Q

What opens the air filter dust ejection valves?

A

Air pulsation that results from engine operation

202a pg. 10

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21
Q

How does an exhaust gas aspirator dust ejection system function?

A

A scavenging line connects the air filter dust collection bowl to the exhaust stack. A suction is created by the exhaust gasses which pulls dirt out of the air filter dust bowl and is blown out exhaust stack.

202a pg. 11

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22
Q

What is the main purpose of the air filter pre-cleaner and dust extraction system?

A

Extend the life of the main air filter— reduce the amount of large particles entering the main filter

202a pg. 12

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23
Q

How efficient are oil bath type air filters?

A

98.5%

202a pg. 12

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24
Q

What is the basic operation of an oil bath air filter?

A

Air is pulled through the oil in the bowl and then through mesh filters which further filters the air and removes any oil that may be pulled up.

98.5% efficient

202a pg. 12

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25
Q

What operating conditions negatively affect oil bath air filters? (5)

A
  • Low oil level — Less filtering
  • High oil level — Oil drawn into engine
  • Hilly terrain — fluctuating oil level
  • Low ambient temperature — Oil thickens, less oil is picked up by air resulting in less efficient cleaning
  • Low air flow speed

202a pg. 13

26
Q

In a two stage air filter design, when should the secondary (inner) filter be replaced?

A

When it is dirty, which typically only occurs when there is a hole in the primary filter.

27
Q

What is a benefit of using pleated style air filters?

A

Large surface area

202a pg. 13

28
Q

What is the efficiency level of dry air filter elements?

A

99.5%

202a pg. 14

29
Q

In a two-stage air filter system, what is the purpose of the inner filter element?

A

To protect the engine from unfiltered air in the event of a pinhole leak or crack in the primary filter element.

202a pg. 14

30
Q

What is the purpose of an air inlet restriction gauge?

A

Serves as a visual warning device that approximates the amount of inlet air restriction. Monitors the induction air pressure after the air filter.

202a pg. 15

31
Q

What level of vacuum is an inlet air restriction gauge calibrated to?

A

25 inches of water

32
Q

What is meant by a constant tension or constant torque hose clamp?

A

A hose clamp that incorporates a spring or washer device to maintain clamping force as the hose expands or contracts with heat changes.

202a pg. 16

33
Q

What are inlet air shutdown devices used for?

A

To protect the engine from over-speeding from a fuel being drawn in with the inlet air.

202a pg. 18

34
Q

How do you properly test an air shutdown device?

A
  • Engine off
  • Set air shutoff
  • Try to start the engine - Should not start
  • Reset air shutoff

Do not test the air shutoff by tripping the air shutoff when the engine is running.

35
Q

What are some of the primary functions of the exhaust system?

A
  • Collect combustion gasses
  • Reduce noise
  • Expel gases to atmosphere
  • Drive a turbocharger
  • Dissipate heat
  • Act as an emission control system
  • Act as a supplementary heat source

202a pg. 19

36
Q

Why might exhaust manifolds be constructed as a multi-piece design?

A
  • Limited access
  • Multiple cylinder heads

202a pg. 24

37
Q

What type of exhaust clamp is typically used to join rigid pipe to flexible pipe?

A

Wide-band stepped clamp

202a pg. 25

38
Q

When is exhaust flex pipe typically used?

A

When there is movement between major components such as the engine and frame mounted exhaust pipe.

202a pg. 24

39
Q

What are the two basic muffler design types?

A
  • Straight-through
  • Reverse-flow

202a pg. 26

40
Q

Where are straight-through mufflers typically only allowed?

A

Off-road use

41
Q

What is the main advantage of reverse-flow mufflers?

A

Increased noise reduction

202a pg. 26

42
Q

What do some exhaust stacks use to prevent water entry?

A

Rain caps

202a pg. 27

43
Q

What is the role of a spark arrestor in an exhaust system?

A

Prevents sparks from flying out of the exhaust stack and possibly causing fires.

202a pg. 28

44
Q

What is the basic operation of an exhaust spark arrestor?

A

Exhaust gases enter the muffler and hit angled vanes which spins sparks, carbon particles, and heavy debris to the outer edges. These particles then enter slots in the outer edge where they can cool and be cleaned through a plug in the bottom of the assembly.

202a pg. 28

45
Q

What are three main functions of exhaust heat shields?

A
  • Prevent grass and brush from contacting hot exhaust surfaces
  • Protect operators and workers from injury
  • Protect cab and sleepers from exhaust stacks

202a pg. 28

46
Q

What grade of fasteners should be used to secure exhaust components?

A

Grade 8

202a pg. 29

47
Q

Why are lock washers rarely used to secure exhaust system components?

A

High exhaust heat will cause the tension in the washer to be lost

202a pg. 29

48
Q

Where are air inlet restriction gauges located?

A

Between filter outlet and turbo

49
Q

Is the air filter system prior to the turbo under vacuum or pressure?

A

Vacuum

202a pg. 33

50
Q

Is the air intake system after the turbo under vacuum or pressure?

A

Pressure

202a pg. 33

51
Q

How is an air filter inspected using a trouble light?

A

Place the light in the centre of the round filter or on one side of a flat filter element. Bright points of light shining through the filter indicate a crack or hole where dirt could pass through unfiltered.

202a pg. 35

52
Q

What air pressure should be used then cleaning air filters?

A

30 - 50 psi, 90 degrees to the pleats

202a pg. 36

53
Q

Should a water or mercury manometer be used to check the air inlet system?

A

Water manometer. If mercury is used, it could get into the intake system and combustion resulting in poisonous gasses being formed.

202a pg. 43

54
Q

How many inches of water would indicate that the inlet airflow is excessively restricted?

A

25 inches of water

202a pg. 42

55
Q

What are three major types of engine problems that could result from air induction system and/or exhaust system failures?

A
  • Lack of power
  • Black smoke (insufficient air)
  • Premature engine wear (dusting)

202a pg. 39

56
Q

Where should a water manometer be connected to measure the level of intake airflow restriction?

A

After the air filter outlet and before the turbo

202a pg. 42

57
Q

What amount vacuum would indicate an excessive exhaust system restriction?

A

3 inches of Mercury when engine under load

202a pg. 44

58
Q

If oil is drawn into the intake on an engine equipped with an oil bath air cleaner, it could cause:

A

Over-speed

59
Q

An air filter pre cleaner relies on what to separate the heavier particles?

A

Angled vanes and centrifugal action

202a pg. 10

60
Q

When does the wastegate fully open?

A

At maximum boost pressure

HET2 (29 decks)

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