EGR Systems
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Transcript of EGR Systems
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Exhaust Gas
Recirculation
(EGR)
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What the heck does this thing do?
Allows burned exhaust gases to enter the
engine intake manifold.
Reduces NOx emissions
When exhaust gases are added to the air
fuel mixture, they decrease peek
combustion temperatures...----For this reason,an exhaust gas recirculation
system lowers amounts of NOx in exhaust.
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Whats in an EGR system?
A vacuum operated
EGR valve.
-AND-
A vacuum line from
the carburetor
Hmmm...
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Heres what they look like...
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The EGR valve consists of...
A vacuum diaphragm
A spring
A plunger
An exhaust gas valve
A diaphragm housing
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Whats the valve designed to do?
Control the
exhaust flow
into the intake
manifold...
SEE THE PHOTO!!!
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Basic EGR system operation...
At idle, the throttle plate in the carburetor or
fuel injection throttle body is closed. This blocks
off engine vacuum so it cant act on the EGR valve.
The EGR spring holds the valve shut and exhaust
gases do NOT enter the intake manifold.
*****If the EGR valve were open at idle, it
could upset the air-fuel mixture and the engine
could stall!!!*****
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More about EGR system
operation...When the throttle plate is swung open to
increase speed, engine vacuum is applied to the
EGR hose. Vacuum pulls the EGR diaphragm up.
In turn, the diaphragm pulls the valve open.
Engine exhaust can then enter the intake
manifold and combustion chambers. At higherengine speeds, there is enough air flowing into the
engine that the air-fuel mixture is not upset by the
open EGR valve.
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Are all EGR systems
the same?
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NO!
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Some different types
of EGR systems...
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Back-pressure EGR valve
Uses both engine
vacuum and exhaust
back pressure tocontrol valve action.
This provides more
accurate control of
EGR valve opening.
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Engine coolant temperature
switch Prevents exhaust gas recirculation when the
engine is cold. (A cold engine doesnt have
extremely high combustion temperatures,thus, it doesnt produce very much NOx.)
Blocks the vacuum to the EGR valve below
100 degrees Fahrenheit (37.8 degrees C.) toimprove the drivability and performance of
the cold engine.
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Wide open throttle valve (WOT)
Sometimes connected into the vacuum line
to the EGR valve.
Opens under full acceleration to provide
venturi vacuum to the EGR valve.
At wide open throttle, intake manifold
vacuum is very low, but venturi vacuum ishigher.
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Heres two more pictures of EGR
valve designs...
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EGRjets
The small EGR jets
meter a small amount
of exhaust gases intothe air fuel mixture.
The jets are small
enough that they do
not upset the idle air-fuel mixture.
N k
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Now you know
about EGRsystems!!!
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Brought to you by...
Hawaiian Brian Dean