HV mode Prime vs 'vanilla' Gen4

Discussion in 'Prime Technical Discussion' started by pakitt, Jul 28, 2021.

  1. pakitt

    pakitt Senior Member

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    I have driven my 2021 Prime for about six months now, and I have had the chance to drive it in EV mode (a lot), in EV Auto mode (some), and HV mode (some). I used to own a Gen4 which I had to sell at the beginning of 2019.
    I have a few questions about HV mode in both versions:
    1. if you enter HV mode with more than 0% left on the EV only portion of the battery, does HV ever use any of that charge? I say this, because I have seen a few times the SoC change by 1%-2% up or down during normal HV driving. I know that you can recharge the battery up to 80% (correct?) when in HV mode going down extremely long hills, but this was not the case. Is the remaining charge of the battery used at all in HV mode?
    2. when the hybrid batter SoC allows it, does the Gen4 allow you to accelerate using only the electric motor beyond the middle line of the Hybrid System Indicator (HSI) in HV mode? I don't remember anymore. For sure Gen3 would not allow it - you reached the middle line and the ICE would fire up immediately, regardless of SoC.
    3. my Prime seems a bit 'rough' when transitioning from ICE to electric motor in HV mode. I haven't noticed it when in EV Auto the ICE fires up when the battery SoC is at 0% or if you accelerate vigorously. I remember the Gen4 was butter smooth in the transitions. Way better than Gen3. The Prime seems to be a step back to this respect.
    4. The fuel consumption of the Prime in HV mode seems to be significantly better than Gen4. Maybe it is just an impression, but I easily beat the EPA combined of 54 mpg - and I don't live in a plain, it is, rather, quite hilly.
    Thanks for any information you could share :)
     
  2. DukeofPrime

    DukeofPrime Junior Member

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    1. I've seen HV mode consume traction battery

    2. I believe the Prime has a more powerful MG2 (or is it MG1?) so it can accelerate faster without the ICE than the Prius.

    3. The ICE is a little buzzy sometimes. Also, the throttle response seems slower when the ICE is running.

    4. It's flat where I live and I can easily get 60-70 mpg (according to the car) with suburban driving in HV mode (mostly staying under 45 mph). It's way better than I expected.
     
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  3. Salamander_King

    Salamander_King Senior Member

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    #1 Yes, but only a little (2-3% SoC) during the time the engine goes through a warm-up cycle. Otherwise, it will maintain the SoC level. Or it can even gain SoC while in HV mode if there is substantial regen.

    #4 Beating EPA number is easy on PP. I don't know if it is harder on Gen4 or not. Some people claim PP with charge left in the traction battery gets better mpg on pure HV mode. I tried comparing it under my own driving condition for my commuting. For small numbers of trials, I did not see a noticeable difference.

    I have never driven Gen4, so I can't comment on #2 and #3.
     
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  4. MTN

    MTN Active Member

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    For more details to Q #1 - if you were in EV and had 10% SoC and switched to HV, the car will maintain that SoC +/- a couple percent.
    If you go down a long hill and regen a significant amount, say 30% SoC, the car will run in EV mode until you're back to 10%. Or you can switch to EV mode, then back to HV, and your new "equilibrium" SoC would be 30%. "banking" the regen for later use

    HV mode tries to maintain whatever SoC you were at when HV mode is started.
     
  5. jerrymildred

    jerrymildred Senior Member

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    As has already been well answered, whatever the SOC when you enter HV mode, that's the SOC the car will use for its baseline. In HV, the Prime will make good use of the battery at speeds under 60 mph as it alternates between ICE on and ICE off. That will cause the SOC to vary as it goes above and below the original level.

    We have a regular Gen 4 with a NiMH battery as well as the Prime. I don't drive the regular Prius all that much, but as I recall, it will let the HSI indicator go above the middle line before the ICE comes on, but it's not as "athletic" as the Prime. (We never put it into EV mode with the button unless we're just moving it a few feet.)

    My Prime almost always has a smooth transition when the ICE comes on or shuts off. I'll notice it if I pay attention, but it's pretty slight. As for EV Auto, I can't answer since I never use it.

    My Prime gets considerably better hybrid mileage than my wife's Prius. It's flat where we live, but it does even better when we visit places with mountains. Not that I get much chance for hybrid mode. I'm over 1,100 miles so far on this tank and still have over 7/8 of a tank. (I need a road trip!!)
     
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  6. pakitt

    pakitt Senior Member

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    Thanks for all the answers!
    Attached 2 screenshots of pure HV mode drives I did yesterday and today, with a half the miles on a highway (average 70+mph), the other half in suburban (average 55mph) and "city" (that is, a couple of traffic lights and stops here and there).
    Where they get the 54 combined is a mystery to me. I didn't even try.
    With the Gen4 I did reach 87MPG, and 94MPG even, on my commute back from work with no traffic lights and an average speed of 25-30MPH, but never this high at 40MPH average.

    IMG_0990.jpeg IMG_1002.jpeg
     
  7. pakitt

    pakitt Senior Member

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    PS: does anybody know how to set the temperature from F to C? I cannot seem to find a way. You can change from MPH to KMH and MPHG to L/100km, but not the temperature.
     
  8. jerrymildred

    jerrymildred Senior Member

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  9. Salamander_King

    Salamander_King Senior Member

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    Just remember the displayed mpg on all Prius is inflated. I get a feeling that PP's display is inflated more than Gen3 which was 5-10% higher than calculated. I believe the EPA number is based on the real value under testing conditions used. When I do a full tank of HV only drive (no charge for the entire tank) with PP, the calculated mpg by a full tank method which is the golden standard of mpg calculation gives the mpg very close to the EPA number.
     
    #9 Salamander_King, Aug 1, 2021
    Last edited: Aug 1, 2021
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  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Toyota gets free fake news from owners, who tire of converting the inflated mpg numbers, or were unaware, or favour the rose-tinted view.

    CleanMPG owner (I think) Wayne Gerdes test-drove a pre-production 4th gen, and noted displayed mpg was spot-on. Presumably the 7%~ “tweak” comes later in the development process. :rolleyes:
     
    #10 Mendel Leisk, Aug 1, 2021
    Last edited: Aug 1, 2021
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  11. Salamander_King

    Salamander_King Senior Member

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    So far for three brands Toyota, Nissan, and Honda all hybrid, Honda gives the most honest mpg display. Nissan's display is just as inflated as Toyota's.
     
  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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    That was my experience with 06 civic hybrid: the cars foibles aside, the mpg was accurate.

    It’s funny how Prius owners will try to rationalize the “error”, saying its gas pump variations, or whatever. The smoking gun though, is the consistency of the error.
     
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  13. pakitt

    pakitt Senior Member

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    I would think that the sensor PCB sends a Celsius value, and then the software converts it in Fahrenheit. Instead, this crap. I don't understand Toyota. It would be cheaper to have one single sensor PCB in stock, instead of 2. One of which, used only in the USA market.
    I guess the conversion of MPH and MPG to metric, are simply to assist you when you travel to Canada or Mexico.
    But why then convert MPG to L/100km? Somebody with a Prius bought in the USA is more likely to just visit for a few days than moving with its car to Canada. Because otherwise, I see no other reason to offer the change between metric and imperial for speed AND fuel consumption.

    Regarding the MFD reporting optimistic fuel consumption values, my European Gen4 was 4.63% off, calculated over 33.000km / 20k miles. This was actually better than my previous Gen3, which was 6.51% off, calculated over 101.000 km / 63k miles. German gas pumps tend to be accurate, with exceptions and considering variations in fuel volume in winter vs. summer.
    The odometer was also less accurate on the Gen3 (like 10% higher than actual speed) vs. the Gen4 (more like 5% off). So the vanilla Gen4 was/is actually more accurate than the Gen3 ever was.
    Even with this in mind, I can beat the EPA ratings hands down. :)

    My father's Hondas were/are a lot more accurate than all my Toyotas ever were/are, both for fuel consumption and odometer.

    I think Toyota uses cheap(er) and less accurate sensors and odometers. After all, only those here on Priuschat actually calculate MPG and odometer accuracy. 99% of drivers out there don't even know what the fuel consumption of their car is.
    I often heard owners tell me, "it consumes 'little'" or "I put in x$/x€ of gas per week". They could not even tell me the MPG reported by the manufacturer.
    BTW: here in the USA, Toyota is one of the few to print clearly the MPG of its vehicles on their website. Try to find the MPG of the F-150 and all its siblings (Ford or not...) Drivers here in the USA clearly don't care about the fuel consumption of their vehicles.

    One thing is sure, MFD accuracy or not. The Prime has one of the best fuel consumptions on the USA market, beaten only by Tesla for electricity consumption (and not by that much.)
     
  14. jerrymildred

    jerrymildred Senior Member

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    Actually, they are thermistors that change electrical resistance according to the temperature. Thermistors are accurate, but they need to be properly located. When you see 107F on your car's dash, that IS the temperature at the sensor. (And not far off from what you'd feel if you got out of the car at a traffic light.) Locating the sensor two feet above screaming hot asphalt that's re-radiating heat is not a good place. So, they are pretty accurate when it's cool, but when the road surface gets hot, the sensors don't tell you the temperature over in the shade under a tree; they tell you the temperature where they are which is practically on a frying pan. If anyone comes up with a way for the car to know how much to compensate for that radiated heat, they will become very rich.

    I understand that some cars have better locations for the sensors, but the best location would be under a shade tree somewhere and about six feet above the ground as opposed to two feet above the pavement.
     
  15. pakitt

    pakitt Senior Member

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    A friend of mine used to work for a software company in Munich writing firmware for BMW. She was telling me that sensors are not that accurate (yes, even the ones used by expensive BMW) and writing an algorithm that compensates for known inaccuracies of sensors, and, as you mention, temperatures off because they are above burning asphalt, is very difficult. This was more than 10 years ago, I guess they have found a way...

    In my old Gen3, Gen4, and now even in the Prime, the temperature when turning on the car is way off, and only after driving a while and wind at ambient temperature has managed to cool it to the "right" temperature, then I know that is the right temperature. 6ft in shade, that is where it is supposed to be - hard to do on a car, I agree ;)
    On page 218 of the Prime's user manual it reads:
     
  16. PiPLosAngeles

    PiPLosAngeles Senior Member

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    They have to find somewhere to spend all the money they saved taking away the illuminated lock and window buttons on the driver's door. It wouldn't feel quite like Toyota if they didn't cost cut driver conveniences while ignoring cost-cutting opportunities that would add convenience.

    Both of my Prime's outside temperature displays have been nearly always the same reading as my Davis weather station, sometimes being off by a degree.

    You can get sensors that are very accurate and inexpensive. For example, the Sensirion SHT30 is accurate to ±0.2°C and can be purchased retail for as little as $1.90 each.
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
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    1. HV mode is almost like "EV Save" or "Battery Save" in other manufacturers' PHEVs. It will fluctuate a bit but mostly keep the SOC near the same % as when you switched to HV mode. I believe if you do charge more (e.g. go down a long, steep mountain) and top up the battery, the car will use the battery charge to return back to the SOC when you first switched to HV mode. In this case, if you want to save the additional charge, you switch to EV then back to HV at the bottom of the mountain to set the new threshold SOC. With PiP owners, this is called "stacking" where you use HV mode to go up and EV mode to go down (or HV but switch to EV then back to HV to store the new charge). By doing this, you can save the stored charge for later on in city driving.
    2. Yes. In Gen 4 and Prime, I've seen the engine stay off even past the mid line on the HSI - 75% is as far as I've seen it in my Prime (usually when the battery is right at the EV/HV switchover SOC or slightly above). You're right, Gen 3 will kick in the engine once you exceed the "Eco Hybrid" area, or the first half of the HSI.
    3. I have not noticed this. My engine start/stop is smooth. If it's the first fireup in months, then it sounds coarse but doesn't feel rough. Granted, my engine miles/km run time is very low as I almost exclusively use EV mode in the past 42,000km of its life.
    4. It is significantly better. 2.8-3.4L/100km is easy within city limits in HV mode. (70mpg+). Even on the highway, the Prime beats the Gen 4 in HV mode (without remaining charge) - and we have both a 2016 Touring (with the 17" wheels) and a 2018 Prime (15" wheels).
     
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  18. Mysteryos

    Mysteryos Junior Member

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    A note on point 2, for the gen 3 prius. My experience with the gen 3 prius is that the system will keep the car in EV, even after first half of the HSI, when the SOC is full. In these conditions, it seems to favor draining the SOC fast, by maximizing the use of the traction battery. I've even seen it go up to 85 km/hr in pure EV (and my pure astonishment as well).
     
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