Engine Balance Shaft?

Discussion in 'Gen 5 Prius Technical Discussion' started by black_jmyntrn, Jun 25, 2023.

  1. black_jmyntrn

    black_jmyntrn Senior Member

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    so see.. thats whats messing me up.. I have the Lexus M20A-FXS, when you look up UX250h... only the M20A-FXS there are two different enginie part sheets, one with the balancer and one without. But the UX250h is only Hybrid.. So why do some Hybrid's have it and others Dont, don't think it has to do with HP as seen in the difference between the Hybrid M20A and non.

    It's the T24A-FTS and a 8GR-FXS that I want in my hands or at least find one a dismantler has in stock and will let me 3D scan them... I can then use my engine bay 3D scans to see what to cut for one of them to fit! Then id finally put one of those shock swing arm steering knuckle spindles on there. With AI... I'm saving all of these scans for this 3D modeling software. I will be able to have AI-improved models made that allow me to easily have prototypes made for these crazy projects I want to do.

    Can you imagine a Prius with the 8GR and AWD with a rear motor with more power in the rear electric motor at 107hp in the Lexus 500h?

    Thing is... Toyota going encrypted on the canbus with this new stuff, means I've got to get creative... smdh!
     
  2. Hammersmith

    Hammersmith Senior Member

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    I'm having a hard time figuring out what you have, what you want, and what in the heck you are trying to do.

    Are you trying to engine swap an M20A into your 2013PiP? Or are you getting a gen5 and want to swap something different into it?



    As was guessed at earlier in the thread, Toyota probably decided whether or not to add the balancer depending on cost, space, and the purpose of the car it's going into. In a regular Prius, don't put it in to get maximum mpg. On a Lexus UX 250h, put it in because the buyer likely wants max comfort. Maybe there's a case or two where they would've normally added it, but there wasn't space for it(it makes the oil pan and crankcase stiffener a little bigger in one direction). Whatever the case, the choice to add or not add the balancer is not directly linked to the car being a hybrid or not.


    If I had complete access to the American version of the MicroCat parts software, I could probably find out some more details about where the balancer is used and where it isn't, but that access doesn't come with a US Toyota TIS subscription like it does with the European TIS.
     
  3. black_jmyntrn

    black_jmyntrn Senior Member

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    I have the UX250h M20A I am almost done having installed and working in my 2013PIP. During my quest to ensure I use what I can from the newer Gen 4 Prime to maximize the gains (i.e. Prime clutch plate which when combined with the Gen 4 Prime TCM should allow my PIP to over come the EV mode MPH limitation) and understand what's inside I stumbled upon the engine balance shaft. So far, it sounds like it's just hardware and no ecu to control it (crossing fingers). Before I turn this bad boy over, I've been trying to account for any gotchas I might run into and making sure I've accounted for anything not in or on the 2ZR and vis versa on the M20A for this to be a successful swap all while using the Prius CVT which Ive added the V cooler plate. I'm actually waiting on the modified cooler plate I made which allows for additional coolant to be held in the system for what I hope will be better cooling.

    EDIT: The messed up part is, when I finally received the motor, rear AWD subframe, rear electric motor and rear inverter... I feel like it wasn't even 4 weeks later that I realized the latest A25A-FXS isn't reversed like the previous gen Rav4 motor was and I really wanted to try that motor, but then.. now glad I didn't since the T24A-FTS is the one I reallt want now! For me its about seeing what's possible to bring life into the Gen 2 and 3 Prius. Versus installing JDM engines or others used with head gasket problems I figure might as well get some extra power.. my end goal is a 500hp PHEV Prius. with the T24A-FTS and a ~250hp rear electric motor, I can do it... and I want it done before EOY!

    here is a video you might like to see.
     
    #23 black_jmyntrn, Jul 2, 2023
    Last edited: Jul 2, 2023
  4. CR94

    CR94 Senior Member

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    In general, most associated with relatively large-displacement in-line Fours in applications where refinement is a priority.

    They increased the stroke vs. the 4th-generation engine. Any time you increase the ratio of stroke to connecting rod length, motion of the pistons deviates farther from purely sinusoidal, thereby increasing vibration at twice crankshaft frequency. Balance shafts counteract that shake----at increased cost, friction. and complication.
     
  5. Hammersmith

    Hammersmith Senior Member

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    Confirmed that the regular Prius does not have the engine balancer. I just got to look at my oil pan while it was on the lift for an oil change.
     
  6. black_jmyntrn

    black_jmyntrn Senior Member

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    whats interesting, the UX250h has no PHEV option... now i am really curious a to what makes the determination for the vehicle to have it?
     
  7. Hammersmith

    Hammersmith Senior Member

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    Well, it looks like your UX250h engine has it, so I'd call it a win unless the very slightly larger crankcase stiffener causes clearance issues anywhere.
     
  8. Trollbait

    Trollbait It's a D&D thing

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    Well, why do balance shafts exist?
    What do people expect of a luxury car?
     
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  9. Isaac Zachary

    Isaac Zachary Senior Member

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    I would guess they build a car, have someone test it, and if they come back saying "I feel a lot of vibration in the car" then they add a ballancing shaft. There are other things that also reduce the vibrations coming into the car. The motor mounts are one of them.

    Ballancing shafts are usually used on smaller engines. Large crossplane V8's and I6's don't need ballancing shafts.
     
  10. Trollbait

    Trollbait It's a D&D thing

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    And people expect a smoother experience from a luxury brand like a Lexus. Thus why such might have the balance shaft when other models don't.
     
  11. Isaac Zachary

    Isaac Zachary Senior Member

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    Yes, while it still depends.

    Like I said earlier, the newest Corvette has a secondary imballance, the same as in the 4-cylinder Lexus. Yet the Corvette doesn't have ballancing shafts.

    But yes, generally the more expensive the car the more likely it will have ballancing shafts, assuming it's a type of engine that would benefit from ballancing shafts, as ride comfort becomes more important than fuel mileage.
     
  12. Hammersmith

    Hammersmith Senior Member

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    Okay, I think this is the complete list for the 2023 model year excluding the Chinese market. Make of it what you will.

    M20A-FKS
    Yes:
    Camry(Europe)
    RAV4(all markets)
    Harrier(Japan)
    Lexus ES 200(Europe)
    Lexus NX 200(Europe)
    No:
    Corolla(Japan, Mexico)
    Corolla Sport(Japan)
    Corolla Hatch(USA)
    Corolla SED(USA)
    Corolla Cross(USA, Europe)
    Noah/Voxy(Japan)
    Lexus UX series(all markets)

    M20A-FXS
    Yes:
    Corolla Hybrid(Europe)
    Prius Prime(all markets)
    C-HR Hybrid(USA, Europe)
    Lexus UX h series(all markets)
    No:
    Prius(all markets)
    Corolla Cross(USA, Europe)
    Innova Hybrid(Europe)
     
  13. Trollbait

    Trollbait It's a D&D thing

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    From other comments, drivers of sports cars with manuals use the vibrations of that imbalance to time shifts.
     
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  14. vvillovv

    vvillovv Senior Member

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  15. Isaac Zachary

    Isaac Zachary Senior Member

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    Uh... Ya...

    That's somewhat the basic idea, but that article is talking about the crossplane V8, which is an entirely different animal.

    An inline 4 cylinder engine has perfect primary ballance. As the two outer pistons come down the two center pistons go up, and vice versa. So they cancel each other out. Perfectly ballanced right? Well no.

    As the pistons go up and down the connecting rod angles which makes them travel faster in the top of the cylinders and slower in the bottom of the cylinders. This creates an upward force at top and bottom dead center and a downward force when the crank is at a 90° angle. Since all the pistons are at TDC or BDC at the same time and are at 90° from either TDC or BDC at the same time they all cause the whole enigne to experience a force that moves up and down. Hence, why inline 4 cylinder engines benefit from a pair of balancing shafts that create a force that is opposite of the force of the imballance.

     
    #35 Isaac Zachary, Jul 4, 2023
    Last edited: Jul 5, 2023
  16. CR94

    CR94 Senior Member

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    Umm, what? ... Try 90° from TDC..
     
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  17. Isaac Zachary

    Isaac Zachary Senior Member

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    Haha! I think I've been doing too much framing. Two 45° angles make a 90° angle. I think that got stuck in my head for some reason.
     
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  18. black_jmyntrn

    black_jmyntrn Senior Member

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    no clearance issues, I've had the motor in and out more times than I can count on one hand. The only thing is my steel skid plate, the cutout for the oil service area will not work on the M20A. I didn't feel as bad cutting a new one since I had to cut the front by a few inches so it plays well with the offroad metal front bumper I have.
     
  19. thetoys

    thetoys Junior Member

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    Balance shaft adds weight. It also reduces response to throttle input (additional mass to rotate, friction…etc.). Nothing is for free. Interested in knowing how much a balance shaft takes in terms of reduced HP or MPG.
     
  20. KMO

    KMO Senior Member

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    All Dynamic Force engines use Atkinson cycle, afaik. The non-hybrid ones (K) have the same 13:1 ratio as the original Prius's 1NZ-FXE. The hybrid Dynamic Force engines (X) are just more Atkinson at 14:1.