AET 261 Unit 2 Exam With Correct Solutions
What exhaust emissions do the PCV valve and the SAI system control? - ANSWER
How does a PCV valve work? - ANSWER The PCV valve regulates flow through
crankcase under all operating conditions (speed and load)
What does the abbreviation AIR mean? - ANSWER Air Injection Reaction
The PCV system controls which exhaust emissions? - ANSWER Both HC and CO
Technician A says that if the PCV valve was defective or clogged, the engine could idle
rough. Technician B says that the engine may stall. Which technician is correct? -
ANSWER Both Technician A and B
How does a catalytic converter reduce NOx to nitrogen and oxygen? - ANSWER
Why must a catalytic converter be mounted close to the exhaust ports of the engine? -
ANSWER
How does a computer monitor catalytic converter performance? - ANSWER
What does the abbreviation PCV mean? - ANSWER positive crank case ventillation
Where is the output of the AIR pump directed when the engine is cold? - ANSWER
Exhaust manifold
Two technicians are discussing exhaust check valves used in SAI systems. Technician A
says that they are used to prevent the output from the SAI pump from entering the
intake manifold. Technician B says that the check valves are used to keep the exhaust
from entering the AIR pump. Which technician is correct? - ANSWER Technician B only
How much of the air needed by the engine flows through the PCV system when the
engine is at idle speed? - ANSWER Up to 30%
The switching valves of the AIR pump have failed several times. Technician A says that a
defective exhaust check valve could be the cause. Technician B says that a leaking
exhaust system at the muffler could be the cause. Which technician is correct? -
ANSWER Technician A only
When checking for the proper operation of the AIR system using an exhaust gas
analyzer, how much should the oxygen (O2) levels increase when the pump is allowed to
function? - ANSWER 1% to 4%
Technician A says that the PCV system should create a slight pressure in the crankcase
at idle. Technician B says that the PCV system should create a slight vacuum in the
crankcase at 2500 RPM. Which technician is correct? - ANSWER Technician B only
,Technician A says that if a PCV valve rattles, then it is OK and does not need to be
replaced. Technician B says that if a PCV valve does not rattle, it should be replaced.
Which technician is correct? - ANSWER Technician B only
What are the three most commonly used catalysts in a catalytic converter? - ANSWER
platinum, palladium, rhodium
How does a catalytic converter reduce NOx to nitrogen and oxygen? - ANSWER Uses
rhodium to separate NOx to N2 and O2 within a reducing atmosphere
Why must a catalytic converter be mounted close to the exhaust ports of the engine? -
ANSWER The desired chemical reactions only take place above a threshold (activation)
temperature; CAT must operate hot
How does a computer monitor catalytic converter performance? - ANSWER It monitors
the difference in upstream vs. downstream O2S
Name at least three tests that can be performed by a service technician to test the
catalytic converter. - ANSWER temp testback pressure testvacuumtest
A catalytic converter is being tested with an infrared pyrometer. Which is an acceptable
(good converter) result? - ANSWER The outlet should be hotter than the inlet by 10%
What two primary sensors does the PCM use to check the catalytic converter? -
ANSWER Precat and postcat oxygen sensor
A catalytic converter can be harmed by _____ - ANSWER Any of the above
Two technicians are discussing testing a catalytic converter. Technician A says that a
vacuum gauge can be used and observed to see if the vacuum drops with the engine at
2500 RPM for 60 seconds. Technician B says that a pressure gauge can be used to
check for back pressure. Which technician is correct?
Question options: - ANSWER Both technicians A and B
Technician A says that the catalytic converter is warranted for eight years or 80,000
miles, whichever comes first. Technician B says that after replacing the catalytic
converter, the old converter must be kept for possible inspection for 60 days. Which
technician is correct? - ANSWER Both Technicians A and B
A catalytic converter has to be at least how hot before it starts to work? - ANSWER
500°F (260°C)
A P0422 (catalytic converter efficiency failure) is set. What is a possible cause? -
ANSWER Any of the above
Which exhaust gas reading indicates a good catalytic converter? - ANSWER CO is zero
What is applied to the ceramic substrate to make the surface porous? - ANSWER
Washcoat
, Two technicians are discussing catalytic converters. Technician A says that the exhaust
mixture must fluctuate between rich and lean for best efficiency. Technician B says that
the air-fuel mixture must be leaner than 14.7:1 for best performance from a three-way
catalytic converter. Which technician is correct?
Question options: - ANSWER Technician A
what would be a wet manifold - ANSWER carborated or TDI
what happens if air velocity is to high or to low for wet manifold - ANSWER to high will
result in the fuel would not have time to vaporize if its to low the vapor just fall and just
remains wet
long vs short runner when would use each - ANSWER long runners would be used for
low rpms
race engines have very short runners
what are battery volt intake runners and how are they used - ANSWER
what is a upper and lower intake manifold - ANSWER
what is the plenum of a manifold - ANSWER acts as a reservoir for air
what is a siameze runner - ANSWER when there are two cylinders that use 1 runner
looks like one hole but goes to two seperate cylinders
do you want back pressure - ANSWER
is the exhaust manifold the header - ANSWER yes
difference between resonator and muffler - ANSWER resonator is designed to change
the sound/ muffler is designed to muffle sound
where is catalytic converter located - ANSWER near the exhaust manifold
what is the volumetric efficency of a NA vehicle - ANSWER 85 or less
when you increase boost which compression ratio do you affect static or dynamic -
ANSWER dynamic compression ratio because static is mechanically determined from
when building the engine.
what makes turbo charger work - ANSWER exhaust gas inertia
whats turbo lag - ANSWER the amount of time exhaust gas takes to spin turbine to
produce boost
how does wastegate work - ANSWER it opens up and allows exhaust gases to bypass
the turbo
what are comon things that wear out on turbo charger aplications - ANSWER bearings,
What exhaust emissions do the PCV valve and the SAI system control? - ANSWER
How does a PCV valve work? - ANSWER The PCV valve regulates flow through
crankcase under all operating conditions (speed and load)
What does the abbreviation AIR mean? - ANSWER Air Injection Reaction
The PCV system controls which exhaust emissions? - ANSWER Both HC and CO
Technician A says that if the PCV valve was defective or clogged, the engine could idle
rough. Technician B says that the engine may stall. Which technician is correct? -
ANSWER Both Technician A and B
How does a catalytic converter reduce NOx to nitrogen and oxygen? - ANSWER
Why must a catalytic converter be mounted close to the exhaust ports of the engine? -
ANSWER
How does a computer monitor catalytic converter performance? - ANSWER
What does the abbreviation PCV mean? - ANSWER positive crank case ventillation
Where is the output of the AIR pump directed when the engine is cold? - ANSWER
Exhaust manifold
Two technicians are discussing exhaust check valves used in SAI systems. Technician A
says that they are used to prevent the output from the SAI pump from entering the
intake manifold. Technician B says that the check valves are used to keep the exhaust
from entering the AIR pump. Which technician is correct? - ANSWER Technician B only
How much of the air needed by the engine flows through the PCV system when the
engine is at idle speed? - ANSWER Up to 30%
The switching valves of the AIR pump have failed several times. Technician A says that a
defective exhaust check valve could be the cause. Technician B says that a leaking
exhaust system at the muffler could be the cause. Which technician is correct? -
ANSWER Technician A only
When checking for the proper operation of the AIR system using an exhaust gas
analyzer, how much should the oxygen (O2) levels increase when the pump is allowed to
function? - ANSWER 1% to 4%
Technician A says that the PCV system should create a slight pressure in the crankcase
at idle. Technician B says that the PCV system should create a slight vacuum in the
crankcase at 2500 RPM. Which technician is correct? - ANSWER Technician B only
,Technician A says that if a PCV valve rattles, then it is OK and does not need to be
replaced. Technician B says that if a PCV valve does not rattle, it should be replaced.
Which technician is correct? - ANSWER Technician B only
What are the three most commonly used catalysts in a catalytic converter? - ANSWER
platinum, palladium, rhodium
How does a catalytic converter reduce NOx to nitrogen and oxygen? - ANSWER Uses
rhodium to separate NOx to N2 and O2 within a reducing atmosphere
Why must a catalytic converter be mounted close to the exhaust ports of the engine? -
ANSWER The desired chemical reactions only take place above a threshold (activation)
temperature; CAT must operate hot
How does a computer monitor catalytic converter performance? - ANSWER It monitors
the difference in upstream vs. downstream O2S
Name at least three tests that can be performed by a service technician to test the
catalytic converter. - ANSWER temp testback pressure testvacuumtest
A catalytic converter is being tested with an infrared pyrometer. Which is an acceptable
(good converter) result? - ANSWER The outlet should be hotter than the inlet by 10%
What two primary sensors does the PCM use to check the catalytic converter? -
ANSWER Precat and postcat oxygen sensor
A catalytic converter can be harmed by _____ - ANSWER Any of the above
Two technicians are discussing testing a catalytic converter. Technician A says that a
vacuum gauge can be used and observed to see if the vacuum drops with the engine at
2500 RPM for 60 seconds. Technician B says that a pressure gauge can be used to
check for back pressure. Which technician is correct?
Question options: - ANSWER Both technicians A and B
Technician A says that the catalytic converter is warranted for eight years or 80,000
miles, whichever comes first. Technician B says that after replacing the catalytic
converter, the old converter must be kept for possible inspection for 60 days. Which
technician is correct? - ANSWER Both Technicians A and B
A catalytic converter has to be at least how hot before it starts to work? - ANSWER
500°F (260°C)
A P0422 (catalytic converter efficiency failure) is set. What is a possible cause? -
ANSWER Any of the above
Which exhaust gas reading indicates a good catalytic converter? - ANSWER CO is zero
What is applied to the ceramic substrate to make the surface porous? - ANSWER
Washcoat
, Two technicians are discussing catalytic converters. Technician A says that the exhaust
mixture must fluctuate between rich and lean for best efficiency. Technician B says that
the air-fuel mixture must be leaner than 14.7:1 for best performance from a three-way
catalytic converter. Which technician is correct?
Question options: - ANSWER Technician A
what would be a wet manifold - ANSWER carborated or TDI
what happens if air velocity is to high or to low for wet manifold - ANSWER to high will
result in the fuel would not have time to vaporize if its to low the vapor just fall and just
remains wet
long vs short runner when would use each - ANSWER long runners would be used for
low rpms
race engines have very short runners
what are battery volt intake runners and how are they used - ANSWER
what is a upper and lower intake manifold - ANSWER
what is the plenum of a manifold - ANSWER acts as a reservoir for air
what is a siameze runner - ANSWER when there are two cylinders that use 1 runner
looks like one hole but goes to two seperate cylinders
do you want back pressure - ANSWER
is the exhaust manifold the header - ANSWER yes
difference between resonator and muffler - ANSWER resonator is designed to change
the sound/ muffler is designed to muffle sound
where is catalytic converter located - ANSWER near the exhaust manifold
what is the volumetric efficency of a NA vehicle - ANSWER 85 or less
when you increase boost which compression ratio do you affect static or dynamic -
ANSWER dynamic compression ratio because static is mechanically determined from
when building the engine.
what makes turbo charger work - ANSWER exhaust gas inertia
whats turbo lag - ANSWER the amount of time exhaust gas takes to spin turbine to
produce boost
how does wastegate work - ANSWER it opens up and allows exhaust gases to bypass
the turbo
what are comon things that wear out on turbo charger aplications - ANSWER bearings,
