1. Attachments are working again! Check out this thread for more details and to report any other bugs.

ICE turning on for a short time - bad or they know what they are doing?

Discussion in 'Prime Technical Discussion' started by pakitt, Mar 16, 2023.

  1. pakitt

    pakitt Senior Member

    Joined:
    Aug 10, 2009
    2,173
    1,311
    0
    Location:
    Colorado
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    This is one thing I am miffed about the Prime, but at the same time I know I can do little about it.
    Let's assume the EV Range is 27 miles (with the temperatures we currently get here in Colorado).
    And let's assume I have to drive about 25 miles.
    What I don't like is the fact that you start in EV mode, drive 23 miles, and then the battery is finished for whatever reason (e.g., driving style) and for the last 2 miles the ICE needs to be turned on.

    I always thought that turning on an ICE (in any car) for such a short period of time/distance is not good at all for the engine.
    The same thought comes to mind when you start in EV mode, you get on the highway, the SOC goes to 0% and then the ICE starts the whole warm-up cycle and the pushes the car "at cold" while driving 70mph.
    Sometimes I just don't know if should start the car in HV mode, or how soon I should put it in HV mode before entering the highway to avoid the engine be cold when it is supposed to push the car when the SOC goes to 0%.

    Has Toyota found a solution to avoid long term damage by turning on the ICE for such short periods of time cold and/or turning it on while driving at highway speeds because the SOC is down to 0%? Is the engine pre-heated in any way when the battery reaches, say, 10% or less? Does the system have any mitigation to avoid the "shock" to the ICE running for such long periods of time, or having to start while driving on the highway?

    Another situation like this is when you are in EV mode, need to accelerate a lot (or want to ;) ) and the ICE fires up from cold to push the car - that cannot be good for the ICE, can it?
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,679
    48,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Yeah, when the battery appears to run out and the ice fires, it still uses a lot of battery and software controls the ice load.
    Same thing on the highway.
    No worries, it’s a phev and all situations have been accounted for
     
    pakitt likes this.
  3. pakitt

    pakitt Senior Member

    Joined:
    Aug 10, 2009
    2,173
    1,311
    0
    Location:
    Colorado
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    Then I wonder, what about the very short fire-ups when you are almost at the end of the trip and the ICE runs for a couple of miles, for a couple of minutes. How is that good for the ICE? (even if you are not driving on the highway)
     
  4. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,679
    48,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Depends on the weather of course, but if if it consistently fires on a regular basis and doesn’t complete warm up, I would hit hv during the drive, then switch back.
    But idk if it really does any damage in
     
  5. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

    Joined:
    May 12, 2018
    6,765
    6,428
    1
    Location:
    Pennsylvania
    Vehicle:
    2018 Prius c
    Model:
    Two
    How much damage do you suppose there would be? They're on the hook for a mechanical warranty here, so there's a very, very good chance they've already got this settled.

    Toyota didn't bring these engines through a timewarp from 1950 or anything... Modern designs are much more tolerant of cold starts and short runs.
     
  6. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,679
    48,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Otoh, I wouldn’t say the same for gen 3
     
  7. dbstoo

    dbstoo Senior Member

    Joined:
    Oct 7, 2012
    1,222
    653
    0
    Location:
    Near Silicon Valley
    Vehicle:
    2024 Prius Prime
    Model:
    XLE
    What is it that makes you think that a 3 minute run is bad for the Prius? Is it complaining in any way? Are there error codes on the display?

    Maybe this will reassure you... My first Prius (2002 gen 1.5) turned on the ICE every time I started a trip, and it cycled on and off till I reached my destination. My second hybrid was a 2010 Camry, and it would back out the the driveway on battery power, then start the engine as I shifted into drive. Both cars were driven in excess of 170,000 miles with no adverse effects.

    Modern cars with modern lubricants and fuel injection are not as liable to break down as our grandparent's Ford. Just drive it and enjoy it.
     
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,679
    48,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Both those vehicles brought and kept the engine up to operating temperature
     
  9. dbstoo

    dbstoo Senior Member

    Joined:
    Oct 7, 2012
    1,222
    653
    0
    Location:
    Near Silicon Valley
    Vehicle:
    2024 Prius Prime
    Model:
    XLE
    Quite true. Now compare the two designs HV vs PHEV. My 2002 would run the engine for the first 5 minutes whether I needed it or not. If I was just making a run to the store the engine would not reach full temperature on either end of the round trip. Every day the engine had to endure the shock of a cold engine start twice. His prius prime also has to endure a cold start twice each commute day.

    I've never seen signs of moisture in the oil of my Toyota hybrids. I change the oil frequently.
     
  10. FuelMiser

    FuelMiser Senior Member

    Joined:
    Jun 29, 2008
    1,267
    860
    0
    Location:
    Monument, CO
    Vehicle:
    2016 Prius
    Model:
    Touring
    The very fact that you're thinking about these situations and posting about it means it's at least somewhat concerning to you; so, when you know you're going to exceed the EV range anyway, there's nothing wrong with switching to HV during a steady-state portion of the trip and have the ICE activate and reach operating temperature under minimum stress.
     
  11. Optiker

    Optiker Junior Member

    Joined:
    Aug 8, 2022
    4
    3
    0
    Location:
    Rochester, New York
    Vehicle:
    2017 Prius Prime
    Model:
    Premium
    You might try using "EV Auto" mode and see if that behaves differently. When I experimented with it in cold weather it ran the ICE for a couple minutes at the start of the trip even though it was using the battery to power the car. It could have been to use engine heat for the interior or to warm the engine so it would be ready to power the car, I'm not sure.

    The Prius Prime engine is designed to warm up very quickly so it may not have to run very long before being used under load. The coolant circulation pump is electric and doesn't run until the engine reaches temperature. Also there is a heat exchanger in the exhaust that uses exhaust heat to warm the engine quicker as well.
     
    dbstoo likes this.
  12. hill

    hill High Fiber Member

    Joined:
    Jun 23, 2005
    19,655
    8,062
    54
    Location:
    Montana & Nashville, TN
    Vehicle:
    2004 Prius
    Model:
    IV
    You get uncontrollable engine startups in freezing weather also. On a PHEV, if you only need a 7 or 8 minute trips & the car is in the nice warmed 58° garage ... but it's only 9°f on that short drive? Yep - just a minute or so before you arrive - the car thinks it needs to start itself primarily to warm the battery. It's a noble process that's designed to protect the battery - as batteries are like people they don't work so well when temperatures are super cold ... but with so many variables it's not a perfectly executed algorithm.
    One nice aspect of Gen 2 Chevy volts was you could put all or part of the traction pack usability on "hold". Let the ICE run gas up front - then use however much battery you saved for the end of the journey instead of the ICE starting up just ½ a block before you pull in the garage. You could do this process whether you saved 5 miles or 50 miles of EV mode.
    .
     
  13. Zed Ruhlen

    Zed Ruhlen Active Member

    Joined:
    Sep 2, 2018
    231
    124
    0
    Location:
    Hood River, OR
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    Funny enough I tried EV Auto mode a few times when I'd be going on a trip that involved stretches of highway driving. I figured it would switch to HV for the freeway but nope, just ran the battery dead and when to HV after that. So I do it the old fashioned way by manually switching to HV for the freeway portions.
     
  14. ColoradoBoo

    ColoradoBoo Senior Member

    Joined:
    Jul 19, 2019
    911
    598
    4
    Location:
    Monument, Colorado USA
    Vehicle:
    2017 Prius
    Model:
    Two
    Yep, I had a pretty big learning curve when we got our first Hybrid...all the strange electronic noises and the ICE coming on, it seemed, for no reason.
    But it's got 33 computers in there so lots going on. I would, actually, worry if my ICE didn't run very much because engines are healthiest when they are running regularly. People who park cars for long periods usually have lots of issues when they do decide to start them up.
    But, Prime or not, engine oil needs changing every 5,000 miles or 6-months. (If the car is only used for short trips and never gets an Italian Tuneup, I'd change the oil every 3,000 miles.)
     
  15. Zed Ruhlen

    Zed Ruhlen Active Member

    Joined:
    Sep 2, 2018
    231
    124
    0
    Location:
    Hood River, OR
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    The short answer is "no, they haven't"

    It's really bad for an ICE to be run for a short period of time. ANY ICE, even the Prius. It's bad because there are lots of unburned byproducts in the blow by and in the exhaust. That causes damage to the internals and to the exhaust system. It is one of the things I really dislike about my Prime. In those situations I would recommend manually putting it in HV mode so the engine warms up properly. Then later you can put it back to EV. As for the freeway situation, it's going to be the same situation. Manually engage HV ahead of time so that the minimum wear occurs in those high acceleration runs.

    Comparisons to the regular hybrids don't apply because they are never used in the same situations as the Prime. The Prime has annoying habits like turning on during downhill drives rather than just using the friction brakes. Your regular Prius fires up the engine as soon as you give it even a little accelerator and keeps the engine running till it is warmed up. The engine is operating in it's warmed state most of the time. This is often NOT true of the Prime. There isn't nearly enough data to determine the long term affect of this strategy.
     
    pakitt likes this.
  16. dbstoo

    dbstoo Senior Member

    Joined:
    Oct 7, 2012
    1,222
    653
    0
    Location:
    Near Silicon Valley
    Vehicle:
    2024 Prius Prime
    Model:
    XLE
    Where did you experience "It's really bad for an ICE to be run for a short period of time. ANY ICE, even the Prius. It's bad because there are lots of unburned byproducts in the blow by and in the exhaust." That's what cars did in the 60s. You can't use lessons from the 70s to condemn the designs of the 2020s.

    If your assertion were true, I would never have reached 170,000 miles without engine problems or repairs on my 2002 Prius nor 175,000 miles in my 2010 Camry. My 2017 Prius Prime is traveling 2,000 highway miles a month with lifetime average mileage of 60.2 MPG. The trip meter says it's spending about 50% of it's time using the ICE on a 1000 mile road trip and 50% running under battery power that was generated while the ICE was the prime mover.
     
  17. Zed Ruhlen

    Zed Ruhlen Active Member

    Joined:
    Sep 2, 2018
    231
    124
    0
    Location:
    Hood River, OR
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    In any cold start situation you get unburdened fuel. Yes it was worse in the era before electronics but the physics haven’t changed and it’s still bad today. I’m not condemning modern designs, they are far better than they used to be.

    Your older Prius and Camry aren’t the same as the Prime and can’t be compared. The fact that you’re driving 2000 miles a month means you must be running the ICE in your Prime regularly.

    That’s not what I’m saying at all. What I’m saying is only running the ICE for a couple of minutes a day is bad for the car. It doesn’t come to temperature, it doesn’t burn off by products, and it doesn’t evaporate the water in the exhaust system.

    regardless of what it says if you go in a road trip there’s no way it runs 50% on battery. It runs mostly on ICE and rarely on battery doing highway driving. At least after the first 25 miles.
     
    pakitt and bisco like this.
  18. dbstoo

    dbstoo Senior Member

    Joined:
    Oct 7, 2012
    1,222
    653
    0
    Location:
    Near Silicon Valley
    Vehicle:
    2024 Prius Prime
    Model:
    XLE
    The next time that you drive your prime in "hv" mode, switch the display to watch where the energy is coming from and going to. Even while driving down the busy freeway at 65 MPH the car swaps back and forth between the ICE and HV battery as the power source for the wheels. Unlike many HEVs, the power split CVT allows the speed of the ICE to be independent of the speed of the wheels. This enables the technique where the RPM of the ICE is chosen for minimum emissions while still providing the power that's needed. Sometimes that means that the ICE creates more power than is needed to move the car. The excess energy is stored in the HV battery. When the battery is sufficiently charged, the car switches off the ICE and uses power from the battery to drive the wheels. It does all this in the background and most people never notice it. It's not uncommon to drive for several miles at a time on battery alone while in "hybrid" mode.

    This technique lengthens the life of the the battery pack. It also allows "waste energy" to be used after the ICE is shut down.

    If someone needs it, I can make a video of the the screen showing how it switches back and forth..
     
  19. Zed Ruhlen

    Zed Ruhlen Active Member

    Joined:
    Sep 2, 2018
    231
    124
    0
    Location:
    Hood River, OR
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    Yes, I’ve seen my displays but unless you’re going downhill it certainly doesn’t do EV for several miles. Most of the time excess power generation (which is actually a part of the design, it HAS to generate power while the engine is running in a 70/30 split) goes directly to the driving electric motor. There’s lots of YouTube videos on how this works.
     
  20. dbstoo

    dbstoo Senior Member

    Joined:
    Oct 7, 2012
    1,222
    653
    0
    Location:
    Near Silicon Valley
    Vehicle:
    2024 Prius Prime
    Model:
    XLE
    Traveling for several miles using only battery power has been done on level ground routinely. My previous 2002 Prius drove on battery power alone for almost 4 miles once I got off the freeway. As long as I was able to keep the speed below 43 MPH the car would continue in stealth mode until I reached a major intersection that was configured to discourage commuters who wanted to use it as a bypass for the interstates.

    My understanding of the 2002 model was that it could run faster than 43 MPH on battery as long as the power demands were minimal and if you wasted some of that power to spin the dead ICE to prevent exceeding the max RPMs of the planetary gearing.

    Somewhere I have pictures of the energy usage display showing 100MPG for each of the 5 minute segments. That indicated that the battery was providing the sole driving power for (almost) 30 minutes straight as I drove down I-80 towards Sacramento. Unfortunately there was one long 6% upgrade near the end of that 30 minutes that required more power than the Prius would allow from the battery.

    But that was the older car design with different batteries and different power profiles. My Prius Prime also flips back and forth from ICE power to battery power. It is much more noticeable when descending a tall mountain on a well maintained interstate.

    I get 20% more range in my Prime than I did from the same amount of energy in my Gen 1 Prius.