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Gen 3 vs Gen 4 EGR Valve?

Discussion in 'Gen 3 Prius Main Forum' started by jimolson, Feb 7, 2023.

  1. jimolson

    jimolson Member

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    I'm currently arm-chair quarterbacking my brother on his valiant effort to retrofit a head blown Gen 3 with a reclaimed Gen 4 motor. This take-no-prisoners 68 year-old is doing it by himself in a pole barn in Bardstown, Kentucky in an effort to stave off retirement boredom.

    I'm an electrical engineer with ability to make circuit boards. Brother asks me to create an adapter that allows him to use the Gen 4 EGR valve in the engine swap.

    Anyone have any idea what the electrical differences are between the two valve types? This forum is full of comments that the two valves are incompatible.

    When I cleaned carbon from my Gen 3 EGR valve I noted its torque is feeble and explains why it gets clogged easily. Did Toyota raise Gen 4's drive current to the stepper motor? Or did they change the stepper motor's gear ratio?

    A small custom PC board to adapt stepper motor drive current or gear ratio would be a straightforward home brew project.

    Brother tells me that someone with mechanical skills needs to be working on a coolant line adapter.
     
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  2. Tombukt2

    Tombukt2 Senior Member

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    From what I understand about the coolant line that can be just blocked off. Apparently it goes to some kind of a little funny valve that in the Gen 3 setup won't be needed or something similar to that effect I haven't had this project in front of me yet I don't know whether I'll get to one or not and the EGR valves I've only seen the Gen 3 the four maybe just in passing. Either EGR valve you're going to want it to be working I would think you'd use the three EGR valve and cooler. I think either way it's how the valve is controlled the valve should stay seemingly pretty similar It's just an electronic controlled EGR valve.
     
  3. ChapmanF

    ChapmanF Senior Member

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    There aren't any electrical differences between them, as far as I know. They're both six-terminal stepper motors and the connector has the same pinout. There was a notion a few years back that the pinout had changed and a flurry of bogus posts about swapping two pins, but that was all misinformed.

    The added coolant passage on the valve itself just keeps the valve cool. It might be worth keeping, because a known failure mode for the valve is that the stepper motor rotor is a thermoplastic, and it has a little ski-jump shaped stop molded into it to define where 'closed' is, and if it gets warm enough for that stop to soften and get mashed, then 'closed' is in the wrong place.

    [​IMG]

    In the Gen 4 hose routing, they just make the valve the next thing in the bypass coolant circuit, after the EGR cooler and before the throttle body.

    Be aware that if you're using Gen 4 EGR components on a Gen 3, the Gen 4 exhaust manifold has the exhaust tap at a lower pressure than in the Gen 3 manifold. All the Gen 4 EGR components are physically larger because of that, to flow the right amount at the lower pressure, and will flow too much if fed from a Gen 3 manifold.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    If it’s just a hobby car, and he’s tinkering, sure. But if having a reliable, functional car is foremost, I’d just use the portion of the 4th gen engine below the head gasket, keep the third gen head, manifolds, throttle body and EGR. Get new head bolts and the Toyota gasket kit.

    there’s some relevant links in my signature. If you’re on a phone turn it landscape to see signature.
     
    #4 Mendel Leisk, Feb 7, 2023
    Last edited: Feb 7, 2023
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  5. PriusCamper

    PriusCamper Senior Member

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    There's a lot of that on PriusChat...

    Sure would be nice if we had a way to address that somehow? Thoughts @Tideland Prius ?

    For example I've done lots of Gen2 HID headlight swaps to standard Halogen because so many people are sick and tired of replacing the pathetic ballasts that fail too often and there's a dozen threads on here about how to redo the wiring and only one of those posts shows the simple straightforward correct way whereas all the other posts have a bunch of nonsense about how you need to wire in a special controller that as far as I can tell doesn't exist...

    Sure would be nice if this website could do better at accurate information, but I guess the internet doesn't really work like that? Though adding a post accuracy voting system/rating sure would be useful.
     
  6. Tombukt2

    Tombukt2 Senior Member

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    All I did for the Gen to headlights from HID on a tourer was to add H4 sockets to the wiring which I never posted here and those lights work perfectly in that car until I took it off the road without issue high beams low beams all of it didn't need a ballast It didn't need anything but they were bright and brighter on bright and then a year after I did that I saw all these posts about needing I don't even know what some kind of a resistor of ballast a relay maybe for what the Gen 2 has all that already in its system headlight relays in the light I'm putting less draw with my LEDs and halogen housings so what in the world would I need to change a relay for.