Avoided warm-up cycle after overnight park

Discussion in 'Gen 4 Prius Technical Discussion' started by GreenJuice, May 19, 2017.

  1. GreenJuice

    GreenJuice Active Member

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    Had my first experience yesterday of my Gen 4 not triggering the warm-up cycle on starting in the morning after parking overnight. This has never happened to me before on the Gen 3 or Gen 2. It's good because I have a 200 yard run before a long downhill commute to work in the morning; which means if I can time the traffic light approaches well I could potentially make my entire commute on electric only.

    I monitor using ScanGauge II and had always assumed the warm-up cycle trigger was based on engine temperature on starting (at least it seemed to be so on the Gen 3 and Gen 2). I wonder if on the Gen 4 there is another trigger related to the time passed after stopping.

    I was home late the night before and it was about 8 hours since I parked up. Coolant water temperature (cWT) on ScanGauge showed 23C (73F). Same values for the inverter coolant water temperature (ICT) and Boosting Converter temperature - upper (BUT) on starting. Battery State of Charge (SOC) was 48% (3 bars on display). I made it about 2 miles before getting caught at some traffic lights and had to accelerate away, triggering the ICE and the warm-up cycle.

    Another interesting comparison I have observed is that the first ICE shutdown after warm-up cycle takes place as low as 36C (97F) with some variability, which is noticeably less than on the Gen 3 and Gen 2 (which were both fixed and reliably happened at 40C / 104F). If you manage to keep avoiding ICE-on with slow accelerations the car seems to allow temperatures to fall away almost to external temperatures, which was not possible on the Gen 3 or 2. If you trigger ICE-on again, the shutdowns take place at successively higher temperatures.

    All my driving is in Eco Mode and with eco settings on all choices.

    I'd be interested to hear if anyone knows about the Gen 4 warm up cycles and how it is programmed differently from the Gen 3 and Gen 2.
     
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  2. kithmo

    kithmo Couch Potato

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    Ambient air temperature is the trigger. I haven't worked out the exact figure but it's somewhere around mid teens deg C where above that the warm up cycle doesn't trigger until the HV battery level falls below 2 bars or you push the accelerator pedal too hard.
     
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  3. alanclarkeau

    alanclarkeau Senior Member

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    I've a similar "first thing in the morning" start. IF I've got at least ½ battery charge, when I park the night before, I ensure the Climate Control is OFF. And, first thing when I POWER up, I press her EV Button.

    No, not every time - probably 95%. But, she has a mind of her own, and 5% of the time, she'll start the ICE straight off, or give "EV UNAVAILABLE". She reckons she doesn't need to give a reason.
     
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  4. Mendel Leisk

    Mendel Leisk Sand Pounder

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    This seems to me to be the number one reason the fourth gen's are yielding such high mpg numbers. Hopefully not overtaxing the battery.
     
  5. Trollbait

    Trollbait It's a D&D thing

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    Calling for EV mode on first start up in previous generations would delay the ICE turning on also. If there was enough charge, the battery wasn't too cold or hot, etc.
     
  6. Mendel Leisk

    Mendel Leisk Sand Pounder

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    With the 4th gen I believe the car will sometime start and can be driven without the engine starting up, without the EV button being pushed.
     
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  7. bisco

    bisco cookie crumbler

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    i never got more than 15 or 20 seconds on a warm day with full battery before the ice fired in my gen 2's.
     
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  8. Harters

    Harters Active Member

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    I have that in the mornings, as long as climate is off I can get out of the garage, drive up the close, and about 300 yards down the road before the ICE cuts in. I usually have about 50% charge in the morning and this is driving in normal mode.
     
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  9. kithmo

    kithmo Couch Potato

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    Yes it does, I assumed that's what the OP was referring to.
     
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  10. Tideland Prius

    Tideland Prius Moderator of the North
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    Yeah. For those who are unfamiliar, here are the stages of warm-up operation for the Gen 2 and Gen 3

    Gen 2
    The Five Stages of Prius Hybrid Operation | PriusChat

    Gen 3
    Gen3 warming up stages | PriusChat

    I believe the stronger electric motors in the Gen 4 allow the engine to remain in S0 for longer because the motor is powerful enough to power the car at low speed and doesn't require the engine to assist like it does in the Gen 2 and Gen 3.
     
  11. alanclarkeau

    alanclarkeau Senior Member

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    Thanks - that explains a lot - and I suspect Gen 4 is based on it.
    Mine will go to 37km/hr cold in EV mode (about 50 when hot), and one time I tried it out on a mix of level/slight-downhill (no traffic either), went for about 2½km then when the battery hit 3 bars engaged the ICE.
     
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  12. dstahre

    dstahre Member

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    My understanding is that the consideration is catalytic converter temperature. Don't know why you didn't get into the warmup though
     
  13. soldierguy

    soldierguy Active Member

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    I thought it was a combination of vehicle speed and engine temp (coolant and/or oil temperature, or maybe catalytic converter temp) that triggered the warmup cycle.

    Very consistently, if I have not driven the car in quite a while (all day or overnight), the engine comes on like clockwork the first time I pass 20 mph. At work in the summertime, outside temps often hit over 100 degrees Fahrenheit, yet if the car has been parked all day, engine warmup starts like clockwork as I pass 20 mph. It does this even though when leaving work at the end of the day, the first mile is downhill.
     
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  14. alanclarkeau

    alanclarkeau Senior Member

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    Yes, that's about right - 38km/hr on a cold engine will kick it to life. But if the heater (Climate Control when the requested temp is MORE than the ambient) is on, it'll come on immediately, as the heater needs the ICE to be running to warm you up.
     
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  15. RCO

    RCO Senior Member

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    I think the engine comes on at high temp low speed simply to bring the cat. up to its optimum working temperature.
     
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  16. Rgtanna

    Rgtanna New Member

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    I'm currently driving a Toyota CH-R Hybrid in Japan. Back home in Australia I drive a Lexus CT200h so I am familiar with the warm up cycle.

    I was surprised when driving the CH-R, the warm up cycle did not run after parking overnight. There must therefore be more similarity between the Gen 4 Prius and CH-R than the Gen 3.

    On a side note, the transition between engine and battery is significantly smoother than the CT200h.
     
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  17. alanclarkeau

    alanclarkeau Senior Member

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    Gen 4's transition is like that - unless you realllllly try, you won't notice it at all, and even then, only rarely.
     
  18. kithmo

    kithmo Couch Potato

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    Can't say I've ever noticed any transition between ICE and EV on any Prius. I've had the Gen 3, the Prius+ (or v wagon in US) and now have the Gen 4, all ran on Shell fuel. Maybe I'm too thick skinned to notice :rolleyes:
     
  19. qettyz

    qettyz Active Member

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    Interesting as my 2014 Auris/Corolla should be totally like GEN3 hybrid system on Gen3 prius.
    But i have had two successfully EV only getaways after work when car has been on hot parking lot(well not so hot, but something like 30C).
    Car has been sitting about 8 hours.

    Havent monitored it via Hybrid Assistant but i try do that next time when i keep car in sunshine and think that maybe it does not fire ICE and check temps from OBD2.
     
  20. alanclarkeau

    alanclarkeau Senior Member

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    If it's a cooler day - and Samantha thinks I want the heater on, she'll kick the ICE on almost immediately I press start. I've got about 1-2 seconds to turn Climate Control OFF and hit the EV button after startup - or her ICE will be on.

    In reality - if I have Climate Control off after the ICE starts (i.e. - the heater OFF as I don't really like heaters unless it's actually cold) - I don't think it makes an appreciable difference to l/100km whether her ICE starts when I first hit START, or whether I run her in EV mode till the battery is low before her ICE starts.

    The ICE WILL start at some time - and if the battery is low, there are no opportunities to play games like Pulse-n-glide etc.
     
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