When to Kick in ICE to Add Just a Few Miles Range

Discussion in 'Prime Fuel Economy & EV Range' started by mr88cet, Jul 16, 2017.

  1. mr88cet

    mr88cet Senior Member

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    It'll certainly run the warm-up cycle regardless, but I've seen cases where it doesn't seem to use the motion of the engine during the warm-up cycle to charge the battery unless you're in charge mode. It seems to completely waste it instead.


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  2. Kramah313

    Kramah313 Active Member

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    I believe it tries to run the engine in certain parameters (medium RPM, low load, like not driving the car) because when the engine first starts the emissions will be higher until it has warmed up. Thus it forces you to "waste" that power as mentioned so that the heavy load of doing useful work doesn't produce higher emissions while the car is warming up.
     
  3. mr88cet

    mr88cet Senior Member

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    It wouldn't surprise me if that is indeed their thinking. I think I personally would nevertheless prefer to put it into charge mode and use that energy, rather than waste it.
     
  4. Kramah313

    Kramah313 Active Member

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    Yeah, me too. I wonder if they think even charging would increase the emissions. Seems like it wouldn't need to pull any more energy, just redirect what's already there
     
  5. thoatvidiadem

    thoatvidiadem New Member

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    EV efficiency drops off so sharply at higher speeds (50 MPH is my rule of thumb) that it just makes sense for me to swap to HV.
     
  6. fredonly

    fredonly Junior Member

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    ICE efficiency also drops at higher speeds. Are you saying EV drops by a higher percentage than ICE?
     
  7. mr88cet

    mr88cet Senior Member

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    I at least don’t perceive that to be the case, but the ICE has a larger energy reservoir to draw from. So, if I know that I’ll need to burn some gas before I reach the next charger, I generally wait until I’m driving at moderate highway speeds.


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  8. mr88cet

    mr88cet Senior Member

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    I personally don’t buy their argument in this regard, or I buy it only to the degree that the engine is expected stay on fairly often after the warm-up period. On a traditional Prius, that might be a fair bet, up to a point, but not for the P.Prime.

    As I mentioned earlier in terms of MPG and engine efficiency in general, I certainly don’t disagree that a fully-warmed-up engine operates much more efficiently than a cold engine, but I guarantee you that a cold engine that isn’t operating at all takes a lot less fuel still!

    The same goes for emissions: I guarantee you that an engine that’s completely off emits less than a warm one running.

    So, I still think it’s better to simply operate the engine as it’s needed. If it’s needed, it will run and it will warm up, but I don’t see much value in preemptively burning gas and $$$, at high emissions, for a few minutes. Or at least not unless they can know for-sure that the warm-up is the start of an extended period of engine operation.


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  9. Kramah313

    Kramah313 Active Member

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    Yeah the idea of an engine running on a plugin for a minute or more just because I hit the gas too hard once doesn't sit too well with me either. But the car can't predict what the driving conditions are going to be and it can't make any heavy power without high emissions until it is warmed up so I think they assume the worst. It may be to make sure the car doesn't drop from SULEV to ULEV status or whatever all of those categories are...I would guess there's probably some kind of legal or financial posturing behind it. For example, it may be better in those terms for 1 minute of very low emissions vs 10 seconds of high emissions so they can say it never puts out high emissions. But I am speculating wildly at this point. Maybe someone knows for sure.
     
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  10. Pdog808

    Pdog808 Active Member

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    EV efficiency most definitely drops at a much faster rate when you get above 40+ MPH. When you are at 65 MPH on EV (which I try to avoid as much as possible), you will notice the battery charge ticking down precipitously. Of course if you are going downhill then all bets are off.

    As for the ICE efficiency dropping off at higher speeds, I averaged about 54 mpg using ICE only on a trip to San Jose recently. The trip included going up some pretty major mountain grades. Average speed was about 80 MPH with occasional runs at 90+. It's always fun to be doing 90 and noticing that you are being tailgated because you aren't going fast enough. Hey it's California...
     
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