Does the Prius Prime ICE always start?

Discussion in 'Prime Technical Discussion' started by kevin.c, Feb 9, 2019.

  1. kevin.c

    kevin.c Junior Member

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    Surprisingly, I couldn't find a definitive answer to this online:

    If you turn on the Prime (with a full battery, in good weather, heater off), does it need to warm up the engine?
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Not for the first 20 some miles, no.
     
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  3. schja01

    schja01 One of just a few in Chicagoland

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    Typically it won’t but if it’s been a long time the ICE will start from time to time.
     
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  4. jerrymildred

    jerrymildred Senior Member

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    If it did start the engine when you turn it on, that would be contrary to the Prius' "Prime" directive, which is to minimize pollution. It won't run the engine unless the computer decides that it's necessary for various reasons or you command it to run by putting it in HV mode.
     
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  5. bisco

    bisco cookie crumbler

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    no
     
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  6. Bill Norton

    Bill Norton Senior Member

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    I thought it did if:
    (correct me if I'm wrong)
    >You pressed the Defrost Button.
    >You pressed to far on the Go Pedal or you drive above a certain speed.
    >If it is too cold out for the Heat Pump to make cabin heat.

    There may be other reasons it will start the smelly gasser.

    Some PHEV's are true EV's when in EV mode, i.e. Full power and Full heat without the fumes and engine wear and routine 10k mi. oil changes (regardless of EV/Gas miles)
     
  7. bisco

    bisco cookie crumbler

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    why would you qualify the question?
     
  8. john1701a

    john1701a Prius Guru

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    YOU ARE WRONG AND HAVE BEEN CORRECTED SEVERAL TIMES ALREADY!

    All caps and bold should make this particular post memorable. Please don't forget the following:

    - Defrost button is a MAX setting, a convenience offered for when the regular defrosting is not enough. In most cases, that regular defroster setting works just. Even here in Minnesota, I simply don't find the need to use MAX. Also, when you do use it, that doesn't mean the engine will continuously run. It will shut off once coolant is warmed.

    - 84 mph has been mentioned over and over and over again as the "certain speed" threshold for EV in Prime. You go faster, the engine will start. It's a moot point though. Where is 85 mph practical or even legal for travel? You'd use up electricity so fast at that speed anyway, way waste it. When I visit my sister-in-law, the travel in Wyoming from the motel to her home requires driving on a 80 mph highway. Turning on the engine then makes perfect sense.

    - The lowest temperature the heat-pump will operate has been mentioned so many times over the past few weeks, there's no possible way you can claim not to have seen it. 11°F is that cutoff, a level that's colder than some people ever have to deal with during their winter. Even here in Minnesota, we don't see that many days out of the year where that temperature persists. That "too cold" isn't a big deal.

    There are videos available if you'd like detail.

    This post has been bookmarked for future reference.
     
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  9. bisco

    bisco cookie crumbler

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  10. bwilson4web

    bwilson4web i3 and Prime

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    Well if you run the gas tank dry, it won’t start. Then you’ll risk other problems. Make sure you have a tool to disconnect the 12V ground.

    Bob Wilson
     
  11. Old Bear

    Old Bear Senior Member

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    In general, modern internal combustion engines don't need warm-up periods. Take a look at this article from Popular Mechanics last December: Warming Up Your Car in the Cold Just Harms the Engine

    Also, be aware that the synthetic Mobil 1 oil specified for the Prime maintains it's viscosity down to sub-zero temperatures. It is not necessary to raise its temperature to achieve effective lubrication.
     
  12. bamike

    bamike Junior Member

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    I think according to Toyota they say it's better to use electric power when doing stop and go (city driving), and to run the car in HV mode with the ICE on the highway on cruise control. That's what I do and I just let the car decide if the ICE should be on or not.

    As an aside, why is everyone on this forum obsessed with shutting down the ICE or having it never come on? Do they think it's good that the engine hasn't turned on in months and the gas is getting stale?

    The car is plenty efficient as it is, let the car use the ICE. Don't fret about it.
     
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  13. a_gray_prius

    a_gray_prius Rare Non-Old-Blowhard Priuschat Member

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    I thought that the defrost button ran both the A/C and the heat (to provide warm dry air); since the heat pump can't deliver both hot and cold simultaneously, the engine is run to provide the heating. Am I wrong here?

    Maybe a lot of us subconsciously really want full-electric cars. I'm guilty of this too (at some point it was a game to not run the engine for a few months) so I'm in the same boat here.
     
  14. kevin.c

    kevin.c Junior Member

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    Many of my trips are < 2 miles. If the ICE came on for the first few minutes every time, like it does in my regular Prius, it would be a big impact on efficiency & mostly defeat the point of buying the plug-in.
     
  15. john1701a

    john1701a Prius Guru

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    2-mile trips to the hardware store and the 1-mile trips to the grocery store are all EV for me, except in the depth of Minnesota winter. Most of the cold-season errand running is in all-electric bliss. 11ºF is the trigger temperature and most of the time we are above that.
     
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  16. john1701a

    john1701a Prius Guru

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    That is indeed how MAX defrost works. If you need maximum, go for it. I find that I don't, that just blowing hot air (from the heat-pump) onto the windshield keeps it clear. So, no need to make the engine run. The key is to not use recirculate. Pulling in fresh outside air is how moisture levels are kept low.
     
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  17. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    Actually, unlike most home heat pumps, the HVAC system on the Prime can heat and cool simultaneously, since there is both a condenser (hot) and evaporator (cold) in the cabin, in addition to the condenser in the engine compartment (and a traditional engine coolant heater core). They play all sorts of games with dampers (to block airflow over the internal condenser if heating is not wanted) and expansion valves (so the outside condenser can really be used as an evaporator in heat mode). The idea of the "front defrost" is that you are saying that that you need serious de-icing (not just wimpy defogging), so the ICE kicks in to provide heat from the engine coolant.
     
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  18. Zed Ruhlen

    Zed Ruhlen New Member

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    One other time the ICE will come on is when the battery is fully charged and you are regen braking down a hill. The car has to dump the electricity somewhere and the only place it can dump it is into the engine. I found this out by accident because I'll charge overnight and in the morning my drive is down hill for a mile or so. Simple solution is to run the HVAC system in the first 5 minutes to use enough electricity from the battery so that the regen can dump back into the battery.
     
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  19. Bill Norton

    Bill Norton Senior Member

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    Technically the engine isn't consuming electricity. It's becoming an air pump and providing deceleration forces so you don't have to use the friction brakes on a downhill with a full HV battery.

    This is not ideal for a cold engine to spin and not make heat.

    The proper solution for hill top dwellers is to not charge to 100% at night.
    Let the cold battery pack absorb the down hill regen power.
    It's made for that and it's much easier on that poor cold engine.

    The Chevy Bolt has a Hill Top Reserve function that stops a charge at 90%.
    This is for hill top dwellers, but I would use it all the time unless I had a long road trip planned.
     
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  20. jb in NE

    jb in NE Active Member

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    That's a good feature. Unfortunately, except for one small feature (the deceleration using GPS history, only on Premium and Advanced), the Prime doesn't take any advantage of the GPS to maximize economy. Doesn't look at upcoming terrain, etc. On the newer Class 8 trucks, the computers analyze the ground ahead and maximize stored energy - faster downhill and slower uphill, for example. I drove through the Colorado mountains, and I had to manage the EV energy manually. Use up the battery on the uphills and go into B mode on the downhills to recover energy without braking.
     
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