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Keep ICE on at low RPM?

Discussion in 'Prius c Fuel Economy' started by skayaks, May 15, 2015.

  1. skayaks

    skayaks Active Member

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    I have been experimenting with trying to get the ICE to stay on at low RPM (monitored with UltraGauge).
    Maybe the C knows best, but here are 2 cases where I'd like to avoid a switch to EV:
    1) Stuck in slow moving traffic on a slight incline so P&G is out. I can't run the ICE in "efficient" band because of the slow speed, but that's OK because I can get relatively high MPG at low rpm. I want to save the battery for what's ahead but the C wants to switch to EV NOW.

    2) No traffic, but a long gentle incline. Running ICE in the efficient band would get me up to speed too quickly - I'd prefer to climb further at very low RPM, but the C wants to switch to EV.

    Here's what I'm trying now:
    When I have the ICE running at low RPM (in the EV band) I force the RPM up and down slightly. Not because I want to, but that seems to trick the car into thinking "Oh, acceleration coming up - don't switch to EV yet." But this isn't very effective. I wish the EV button was an ICE button instead.

    Any suggestions for a better way to maintain low RPM? or an explanation of why I'm a fool to try?
     
    #1 skayaks, May 15, 2015
  2. mmmodem

    mmmodem Senior Taste Tester

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    I think these are instances where a Prius or any hybrid gets maximum fuel economy. By forcing the ICE to come on you are hurting fuel economy. The ICE is most efficient at high rpm so you want it to be off at low rpm so EV can take over.

    In other words, drive as normal.
     
    #2 mmmodem, May 15, 2015
  3. fuzzy1

    fuzzy1 Senior Member

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    Will 'B' gear keep the ICE on for you?

    While far from its intended use, which is to scrub excess energy on downhills, it might help get the function you are looking for on shallow uphills.
     
    #3 fuzzy1, May 15, 2015
  4. valde3

    valde3 Senior Member

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    I think that best you can do, at least for the second one, is to let the speed slow down while at EV and then bring the speed up by using enough throttle to keep it one ICE. Basically pulse and gliding. It will work in this situation even if you’re using battery in the “glide” part.

    On the first one I don’t think it benefits you anything to try to keep it one ICE. If you don’t really need the charge after the hill you can use the battery to lower charge before so that its charging up the battery and ICE is running.

    Normally only situation where it helps to keep Prius in the ICE or in the EV is when, without you doing it, Prius would switch fast back and forth between them.
     
    #4 valde3, May 15, 2015
  5. bisco

    bisco cookie crumbler

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    system hack?
     
    #5 bisco, May 15, 2015
  6. skayaks

    skayaks Active Member

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    Thank you for all suggestions.
    Hmmm, I don't know if that will change the ICE/EV conversion points but it's an interesting thought. I'll read more about B mode.

    Yes, but because I'm climbing a gentle hill the glides would be very short. I think (but do not know) that most folks recommend avoiding EV while climbing. (Unless you know there's a nice fat descent coming up.)

    The only "hack" that came to mind was to set the heater or AC to a level that would force the ICE and then try to use the the fan on/off switch as an ICE on/off switch. I didn't try this because it seemed too silly. And much too silly to admit to on PriusChat.
     
    #6 skayaks, May 15, 2015
    bisco likes this.
  7. valde3

    valde3 Senior Member

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    In this case hill is gentle enough and speed is low enough that it’s better to use EV than ICE. But even better would be to use pulse and glide. If you use the battery while “gliding” “glide” part isn’t going to be short. No matter how much battery you use during the “glide” it’s still more efficient than just constant throttle if constant throttle would end up you running the whole time in EV.
     
    #7 valde3, May 15, 2015
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