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EGR blanking plate ?

Discussion in 'Gen 3 Prius Technical Discussion' started by Buderim, Aug 20, 2017.

  1. Buderim

    Buderim Junior Member

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    I am a new owner of my first Prius, a mid 2009 build Gen3 it has 86,000 miles on the clock and has full Toyota history. It is running great and I want to keep it that way as I plan to keep it for a long time.

    I do a lot of short journeys in a climate similar to Southern Florida . So i am a bit worried by some threads I have read regarding the excessive oil consumption for the early Gen3 models .

    I have bought a oil catch can that I am going to install , but I was also trying to find out if it is worth blanking off the EGR at the same time ,

    I live in Queensland Australia and we have NO emissions testing . So failing a test will not be a problem. I am just trying to find out if it will be of any benefit for the long term health of the car ?
     
    #1 Buderim, Aug 20, 2017
    Last edited: Aug 20, 2017
  2. mjoo

    mjoo Senior Member

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    PCV oil catch should help slow the buildup of EGR deposits. This is because any PCV oil burned by the engine will create oily soot that recirculates through the engine and sticks to everything.

    The EGR, albeit being a nuisance, has a few benefits to your engine:

    1. Lowers throttle losses at part throttle
    2. Lowers fuel requirements when power isn't needed.
    3. EGR cooler is a boost that helps warm the engine a little quicker when it's cold.
    4. The cooled EGR gas entering your engine actually cools the combustion chambers and this helps to prevent preignition and detonation. The EGR gas input is approximately 100 degrees C thanks to the EGR cooler. Contrast to that, the flame temperature of gasoline is 2138 degrees C. The gen 3 prius has a maximum EGR flow of 21%. So, assuming a completely clean EGR system, a 21% EGR flow rate can lower the combustion temperatures down to:

    100 x 0.21 + 2138 x 0.79 degrees C = 1710 degrees C.

    That's a whopping 428 degrees C reduction!

    Without EGR, the ECU will increase the injector pulse width until the mixture is stoichiometric. The result of this is the combustion chamber will see the full temperature of 2138 degrees C.

    5. A working EGR will keep the engine within Toyota's design specifications and can greatly reduce the incidence of: head gasket failure, the warping of the cylinder head and block, burning the exhaust valves, detonation and preignition that can blow apart engine components. It's excessive temperature differences between the combustion chamber and the water jackets that cause the warping of engine parts.

    EGR system can be a beneficial part of the engine. It just needs periodic maintenance to keep things clean. Our fuel is dirty and the PCV system is dirty
     
    #2 mjoo, Aug 23, 2017
    Last edited: Aug 23, 2017
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Are there actually two PCV circuits: the one at the crankcase, and another similar, albeit coming off the valve cover? I'm not sure, should do a little digging, in the engine bay and the Repair Manual. I'm thinking either way it's the crankcase circuit that's way more prone to suck up oil?
     
  4. mjoo

    mjoo Senior Member

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    It's actually one circuit. Crankcase vapor flows out of the crankcase through the PCV into the intake manifold (IM) because of IM vacuum. The tube connecting to the camshaft cover is allowing clean air (from the air filter) to replace the crankcase vapors. There is little to no vacuum where the clean air is sourced.

    The PCV circuit is thus: clean air from air filter -> tube -> cam cover -> crankcase -> PCV valve -> tube -> intake manifold -> engine
     
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  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Ahh, it's coming back to me, lol. The plumbing to the valve cover has air flow the other way, to compensate.
     
  6. mjoo

    mjoo Senior Member

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    For the vast majority of street driving the flow through the PCV system is

    Flow #1:
    clean air from air filter -> fresh air tube -> cam cover -> crankcase -> PCV valve -> tube -> intake manifold -> engine

    Near wide open throttle, the pressure difference between intake manifold and the clean air tube becomes small. This is where the PCV valve closes. Any blowby will flow in the opposite direction

    Flow #2
    crankcase -> cam cover -> fresh air tube -> throttle body -> intake manifold -> engine

    Most of the oil vapors flow through the PCV valve for a couple of reasons: it is much closer to the oil sump and most PCV flow is Flow #1
     
    M K, RMB and Mendel Leisk like this.