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EGR Systems

Apr 02, 2018

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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

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