202A - Air Induction & Exhaust Flashcards
What is the required air to diesel ratio?
20 lbs air to 1 lb diesel
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What are five main purposes of the air induction system?
- Clean the air supply
- Silence the airflow
- Provide sufficient airflow
- Cool the air
- Allow extra airflow when used with turbos
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What are the two main design types of engine air filter systems?
- Pleated paper filters
- Oil bath
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What is used to quiet the engine intake air flow?
Air silencers. Either as a standalone unit or as part of other air filter components.
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At what inlet air temperature is maximum engine performance achieved?
Less than 33 C (90F)
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What happens to inlet air temperature as it’s compressed?
Temperature rises
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Air density increase as temperature:
Decreases
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What two factors affect the amount of air drawn into a cylinder of a naturally aspirated engine?
- Amount of partial vacuum created by piston intake stroke
- Amount of atmospheric pressure
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When the intake air is at atmospheric pressure, the engine is said to be:
Naturally aspirated
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What is the volumetric efficiency of a naturally aspirated engine?
75% - 85%
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What factors limit volumetric efficiency? (7)
- 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
Is a dirty air filter more or less efficient?
Air filter is more efficient. (Engine is not, but the filter itself is more efficient at filtering the air to smaller particle size)
What volumetric efficiency percentage could a turbocharged engine achieve?
110%
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What is an air filter pre-cleaner?
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.
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What percentage of the larger particles does an air filter pre-cleaner remove?
80%
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What are some pre-cleaners designed with as a means of separating heavier particles into a dust collection bowl?
Designed with angled vanes
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What do angled vanes do in an air pre-cleaner?
Spin the air to fling the heavier particles outward and into a dust collection bowl.
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Are dust ejection systems on air cleaners designed to be operated manually or automatically?
Will automatically open when engine is running to eject particles. Can be removed manually though in cold weather to clean.
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How should one-way air filter ejector valves be oriented?
Pointing downwards
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What opens the air filter dust ejection valves?
Air pulsation that results from engine operation
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How does an exhaust gas aspirator dust ejection system function?
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.
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What is the main purpose of the air filter pre-cleaner and dust extraction system?
Extend the life of the main air filter— reduce the amount of large particles entering the main filter
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How efficient are oil bath type air filters?
98.5%
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What is the basic operation of an oil bath air filter?
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
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