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Weak MG2 ? how to measure output?

Discussion in 'Gen 3 Prius Technical Discussion' started by tacopyro, Aug 10, 2021.

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  1. tacopyro

    tacopyro Member

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    @Mendel Leisk i keep forgetting to record here. i checked the rear brakes, while they do have a tiny bit of drag, i dont believe they are significant enough. i did see that it needs new brake pads bec they are half worn and dont seem to be ceramic pads. next on my list. been working on other peoples cars lately so no time to work on mine...
     
    #21 tacopyro, Sep 1, 2021
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  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah I think that’s normal with rear disk brakes; this is ours doing the spin test:

     
    #22 Mendel Leisk, Sep 1, 2021
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  3. tacopyro

    tacopyro Member

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    Mine has slightly more drag than that. but i will be changing the pads soon. Thanks for the reference!
     
    #23 tacopyro, Sep 1, 2021
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  4. tacopyro

    tacopyro Member

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    sooo.... i bought Jack's Nexpower lithium battery pack. its only been 2 days and 50 mi.
    at first it felt like the old battery pack. but as i gain more miles. it seems to be adjusting itself.
    can anyone tell me if this is just me being subjective or can the ECU actually adjust itself depending on the Battery condition?

    i definitely can go EV farther and have better sustained power uphill.
    with the old pack, i started with 43mpg in Jan 2021 and was just doing 37 by Sept. altho its mostly 2 mi trips to take kids to school and back.
    hoping to get at least 50mpg in the next tank of gas.

    the old pack was starting to have issues at block 7 with voltage diff as high as 0.25v and i'm thinking my mg2 is worn... we'll see :)
     
    #24 tacopyro, Oct 7, 2021
  5. rjparker

    rjparker Tu Humilde Sirviente

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    MG2 is unlikely to be "worn". It has no brushes or clutches or gears that disengage. If the stationary mg2 coils were to leak high voltage or use excessive current or open a winding, your dash would light up like a Christmas tree and your car would be in limp mode if it could drive at all.
     
    #25 rjparker, Oct 8, 2021
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  6. tacopyro

    tacopyro Member

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    Thanks RJ! just trying to understand better. i understand the electrical components will be up to the task. i was wondering more about the bearings that hold the motor. it is 352k mi after all. i guess the only way to find out is to put in a younger transaxle. an endeavor far down the road.
    In the meantime i will pursue other simpler things like wheel bearings, and tire pressure.
     
    #26 tacopyro, Oct 8, 2021
  7. Mdv55

    Mdv55 Active Member

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    50mpg on short trips like that seems like an unrealistic expectation.
     
    #27 Mdv55, Oct 9, 2021
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  8. mr_guy_mann

    mr_guy_mann Senior Member

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    If the bearings inside the transmission were failing, I would expect them to make noise and you would find metal bits and "sparkles" in the fluid.

    Posted via the PriusChat mobile app.
     
    #28 mr_guy_mann, Oct 13, 2021
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  9. ChapmanF

    ChapmanF Senior Member

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    Gen 1 had DTCs on the books for "small reduction of motor magnetism" (P3120-234), "large reduction of motor magnetism" (-235), "small reduction of generator magnetism" (-236), and "large reduction of generator magnetism" (-237). Toyota at least accounted in the Gen 1 manuals and firmware for the possibility of the permanent magnets losing some strength.

    But I can't say that I've ever heard of anybody seeing those codes IRL.

    Gen 3 has a couple codes on the books, P0A90 (drive motor A performance) and P0A92 (hybrid generator performance) that might have carried forward some elements of those Gen 1 codes. The PDF copy of a Gen 3 manual I'm looking in at the moment seems to be missing the detail sections for P0A90 and P0A92, so I can't say anything more about them. Maybe I'll remember to look next time I'm signed in to TIS.

    Still, I don't think I've heard of anybody getting those codes either. I would be looking for less exotic explanations for whatever performance issues are affecting this car.
     
    #29 ChapmanF, Oct 13, 2021
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  10. rjparker

    rjparker Tu Humilde Sirviente

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    I can tell you a bad wheel bearing can cost you around 2 mpg and is not immediately obvious when its cold. On my 250k mile gen3, it was quiet when cold but heated up within two miles and was clearly obvious above 35 mph.
     
    #30 rjparker, Oct 13, 2021
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  11. tacopyro

    tacopyro Member

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    Thank You. i dont have anyone else to ask so i'm glad you mentioned that. what would be a realistic expectation?
    since i have never had one new i dont know what the baseline would be...
     
    #31 tacopyro, Oct 25, 2021
  12. tacopyro

    tacopyro Member

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    yes there was some shiny sparkles when i replaced the fluid. i guess will know when i reach another 30k to replace it again.
     
    #32 tacopyro, Oct 25, 2021
  13. tacopyro

    tacopyro Member

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    sorry for the delay in response. i been on a home energy/automation related kick since i was shocked by my electric bill. learning about solar and solar batteries and reducing my consumption.
     
    #33 tacopyro, Oct 25, 2021
  14. Mdv55

    Mdv55 Active Member

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    Really temperature dependent and depends on drive cycle. My car will take anywhere from 5-10 miles to start averaging that mpg consistently. When winter hits for me I won't be able to sustain 50mpg until the car is fully warmed up and then can start operating under ideal conditions.

    If you're always doing 2 mile trips I'd be thrilled with low 40s for mpg.
     
    #34 Mdv55, Oct 25, 2021
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  15. tacopyro

    tacopyro Member

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    Thank You :) i am doing great then! :) around 43mpg. from my limited observation, the new/lithium battery helps.
    but yes the cold weather isnt helping much.
     
    #35 tacopyro, Oct 25, 2021
  16. tacopyro

    tacopyro Member

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    Thanks for the clues!
    i wonder what parameters these codes are looking at and what range it has. that would be a good place to look. i checked my copy of the pdf and it doesnt say so either... i will also look next time i fire up techstream. so far motor winding resistance test is all i see...
     
    #36 tacopyro, Oct 25, 2021
  17. Mdv55

    Mdv55 Active Member

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    Does Hybrid Assistant not let you see what kind of torque MG1 and MG2 are putting out?

    The Torque app let's me see that. Should be easy enough to compare readings between cars to see if there is actually something worth chasing.
     
    #37 Mdv55, Oct 25, 2021
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  18. tacopyro

    tacopyro Member

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    Thanks! i'll give that a shot soon.
     
    #38 tacopyro, Oct 25, 2021
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