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"B" mode...what for?

Discussion in 'Gen 5 Prius Technical Discussion' started by peternumber2, Feb 14, 2024.

  1. vvillovv

    vvillovv Senior Member

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    Beside not being able to set DRCC while in B. This one is more about DRCC being able to slow the car very quickly. (not as fast as friction braking can) . By holding the cruise stalk down for 5 second the Gen4 will slow very quickly. And will slow from what ever speed your DRCC is set at, until the Prime reaches the speed approaching the minimum speed cruise can be set ( in the Gen4 it appears to be 28mph where it appears to quietly shut off ).
    A word of caution. Don't ever try that at hwy speeds if there is anything following behind.
     
    #121 vvillovv, Feb 21, 2024
    Last edited: Feb 21, 2024
  2. Trollbait

    Trollbait It's a D&D thing

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    If it is like my old Camry ICE, the D1-6 and S1-6 are the same thing. Use of the paddle shifters in D temporarily puts the car in S. The car will switch back to D when stopped, and maybe under other conditions. If the Rav4 Prime goes back to D when applying the accelerator, then it wouldn't get the acceleration difference with being in S.
    So how are the Camry and Rav4 hybrids generating extra acceleration force with the lower 'gears'? They are equipped with variations of the eCVT in the Prius.
     
  3. ChapmanF

    ChapmanF Senior Member

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    The answer is almost certainly in the New Car Features Manual for those models. It could have something to do with what the actual "variations" are on the Prius CVT, or it could also be nothing fancier than the kind of "extra acceleration force" the gen 3 "PWR mode" makes you feel you've got.
     
  4. vvillovv

    vvillovv Senior Member

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    Pro Kelly does a dive into the P710 from the 2019-2022 RAV4 Hybrid and mentions the P810 in the RAV4 Prime.
    youtu.be/O61WihMRdjM

    older techniques like heuristic, warp stealth and pulse and glide behave a lot differently when there is more EV because of the way the programmings been adjusted. Try pulse and glide in a Prime. It can be done, but will it get the driver better results? warp stealth shows up for a second, but that's about it, it's not easy to even see it, much less hold it.
     
  5. Trollbait

    Trollbait It's a D&D thing

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    My CVT has psuedo gears. Any reason why the HSD eCVT can't?
     
  6. ChapmanF

    ChapmanF Senior Member

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    "pseudo gears" are always possible, just like the gen 3 Prius ECO/PWR modes. add a few lines of code to make the ratio adjustment feel steppy or different.

    It's also possible the "variations" on the Prius CVT could include additional real physical capabilities. If so, the New Car Features manual would detail those.
     
  7. peternumber2

    peternumber2 Junior Member

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    Pseudo gears are nonsense...they can only decrease efficiency, imho.
     
  8. Trollbait

    Trollbait It's a D&D thing

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    I thought those modes only changed the accelerator mapping. Not change how the engine and hybrid system
    react to a given throttle position.
    I use them to increase engine braking, which is exactly what the pseudo gear, B, is for on the Prius.
     
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  9. ChapmanF

    ChapmanF Senior Member

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    Changing the accelerator mapping is precisely changing how the engine and hybrid system react to a given [go-pedal] position. It changes nothing about what the car is capable of, but changes how it feels when you press the pedal.

    The pseudo gear, B, on a Prius, has two effects, one easily noticeable to the driver, and the other a slight change to the way the ECU blends two different slowing techniques.

    The easily-noticeable effect is another accelerator-pedal remapping. The normal fully-released pedal position represents a slight amount of decel, and B remaps that to represent a slightly greater amount of decel. That's what makes it feel as if it has shifted to a lower "gear". Both regen and engine-twirling can still be used, in some combination, to achieve the decel, same as in D mode.

    The other effect of B is to slightly change the blend of those two techniques to favor a bit more engine twirling a bit earlier than would be normal in D. That's to allow B to be used to treat the battery gently on long descents. (The details of this change may differ in a Prime.)
     
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  10. Trollbait

    Trollbait It's a D&D thing

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    Some term confusion here. I'm using throttle term to refer to the throttle on the engine, not the pedal. From Sonic forums, I think of the pedal as a torque demand switch.

    For illustration, depressing the pedal in normal mode 50% opens the 'throttle' 50%, or tells the ECU you want 50% of torque output.. In eco mode, you have to depress the pedal more to get that level of throttle, and depress it less in power more for it. No matter how much the pedal has to be pressed, the point at which it tells the car to open the throttle 50% results in the same response from the system.
     
  11. ChapmanF

    ChapmanF Senior Member

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    I saw the potential for confusion, which is why I pinned it down to go-pedal in square brackets to indicate the change.

    I didn't go the other way, because the assumptions you've made about the engine throttle are too far away from how the car works. Can't assume that pressing the go pedal X amount means opening the engine throttle Y amount and eco/normal/pwr just change the X⬌Y relationship. The go pedal does not have anywhere near that much to do with the engine throttle.

    When we look at the familiar eco/normal/pwr graph, the X axis is the go-pedal input, but the Y axis is not engine throttle; it is an overall "motive force" request to the car.

    [​IMG]

    The HV control ECU looks at that total "motive force" request, and it decides (based on a lot of things) how much of that force to get from the battery, and how much to get from the engine. Those decisions can be different from one time to another, even with the pedal pressed the same amount. The decisions can change while you're holding the pedal down the same amount.

    Only after calculating how much of the power request will have to come from the engine, and what the engine's best RPM is for producing that much power, does the HV control ECU send a message to the ECM saying "please take engine to such-and-such RPM for such-and-such horsepower", and the ECM decides what throttle opening to use to make that happen. Meanwhile, the HV control ECU also arranges for the transmission to match that engine RPM to the road speed. The HV control ECU is the conductor of the whole show.
     
  12. Trollbait

    Trollbait It's a D&D thing

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    I was using throttle as a stand in for 'torque demand from the driver' which I guess I wasn't clear about. Depressing the accelerator in the Sonic didn't directly open the throttle plate. Instead, the ECU decided how much the open the throttle and how much turbo boost to allow for the given moment to provide the torque or motive force the driver called for.

    Which is separate from what the Outback is doing with the psuedo gears on the CVT. Downshifting on deceleration increases the engine rpms. From the little the testing I did, it will allow higher rpms while accelerating on a lower 'gear'.

    So are the the psuedo gears on Toyota hybrids with the sequential shifter dictating changes to the available engine output, or just applying a modifier to the pedal position to get the increased acceleration ration force? KISS and the further thought as me going with the latter.
     
  13. Kenneth111

    Kenneth111 New Member

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    Regenerative braking in "B2 mode" enhances energy recapture when descending hills, while pressing the brake primarily slows down the vehicle. B2 mode increases regenerative braking intensity, effectively capturing more energy to recharge the hybrid battery during deceleration.
     
  14. fuzzy1

    fuzzy1 Senior Member

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    That very certainly wasn't how my North-American-market 2010 and 2012 Prii worked. But they also didn't have a "B2" mode, just "B". I won't speak to your 2010 Euro-market models.

    Descending hills, my Prii filled the traction battery faster with "D" mode and judicious use of the foot brake for regeneration, or Cruise Control mode with no foot braking, than with "B" mode. But once the battery filled, it was just friction braking with no regeneration for the next several thousand vertical feet of descent, making the brakes very hot. "B" mode spins up the engine as an energy wasting mechanism, delaying battery fill-up and greatly reducing brake heating.

    The OP of this thread has a Prime, not a regular Prius. I now have a RAV4 Prime. These Primes have additional regeneration modes when in pure EV mode, modes lacking from the hybrid-only versions such as your 2010.
     
    #134 fuzzy1, Mar 3, 2024
    Last edited: Mar 3, 2024
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