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New HSD stage?

Discussion in 'Gen 3 Prius Fuel Economy' started by anne1965, Aug 9, 2009.

  1. anne1965

    anne1965 Gotta love the game...

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    Yesterday and today I have observed something new on my Gen III. In both situations I had started the car with a cold engine and only 3 bars on the battery. In both occasions I had to make a short stop shortly after leaving.

    When I started the car back up, it took off in electric mode, but when getting some speed, the engine turned on and didn't switch off again for ~2 mins. It wasn't idle check mode, since that should be canceled when going over 60 km/h, or driving below ~50 km/h for 5 seconds. Nothing would stop it, even the battery going from 2 bars to 3. It looked more like it decided it was time to burn some gas. Very weird to be waiting at the traffic light with a running engine. That had not happened to me before in my Gen III.
     
    #1 anne1965, Aug 9, 2009
  2. jay_man2

    jay_man2 jay_man_also

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    It's happened to me before in the Prius, as well as the '08 Highlander Hybrid before it. It's funny how when you get your first hybrid that it's so strange that the engine shuts off and it's eerily quiet, then after a while you don't notice it being off, but on.
     
    #2 jay_man2, Aug 9, 2009
  3. anne1965

    anne1965 Gotta love the game...

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    This never happened to me in my Gen II during the summer. When the battery was depleted (for example in a really bad traffic jam due to some accident), it would fire up the ICE whenever you pressed the accelerator, but never keep it running after you lifted your foot. It really seems new behaviour to me.
     
    #3 anne1965, Aug 9, 2009
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I'll be looking for this but haven't seen it, yet. Temperature? Was air conditioner on? Head lights?

    What I have noticed is at speeds below 46 mph, the charge/discharge cycling seems to allow the battery SOC drop down to 2 bars and the engine cycles as needed to maintain this low level. But as I approach 46 mph, the engine cycles seem to provide enough excess charge to bring the battery SOC higher. Above 46 mph, the battery soon charges and normal engine-on efficiency returns. I had seen similar behavior with my NHW11 but not to the degree the battery SOC indicator shows.

    I have observed that shifting to "N" early will leave the ZVW30 engine running and increase the indicated MPG. This is the same behavior seen with my NHW11 when the mass flow drops from 4.5 g/sec to ~3 g/sec. For both models, an idling cold engine appears to burn less fuel when in neutral.

    Bob Wilson
     
    #4 bwilson4web, Aug 9, 2009
  5. anne1965

    anne1965 Gotta love the game...

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    Nope. Outside temp was 20 C, so no A/C. It was day, so no head lights too. It seemed to be triggered by low SOC, and then kept the ICE running for some time to bring it to a higher SOC. But I got the feeling that that SOC was higher than it usually accepts. I have noted that the Gen III depletes the battery much more in city traffic than the Gen II. So it looks like it sometimes decides to recharge the battery for a longer period.
     
    #5 anne1965, Aug 9, 2009
  6. subframe

    subframe Junior Member

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    I saw this over the weekend, but only after truly terrible traffic resulted in two bars on the battery indicator. It somewhat worried me, but once I was able to get some more charge into the battery, the engine shut off as expected and has worked normally since then.
     
    #6 subframe, Aug 11, 2009
  7. OZ132

    OZ132 Member

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    I have always resented computers doing what they think best, without regard to what I think. I the case of this car, I have had to get over it. Just surrender your will, and love Big Brother! He knows best...
     
    #7 OZ132, Aug 17, 2009
  8. qbee42

    qbee42 My other car is a boat

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    It appears that Toyota has increased the hysteresis in the Gen III charging cycle. The Gen III tends to run the ICE for a longer time when charging in stop and go traffic. The Gen II tends to short cycle the ICE, with quick on and off charging bursts.

    Tom
     
    #8 qbee42, Aug 17, 2009
  9. anne1965

    anne1965 Gotta love the game...

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    I just observed another instance of this behaviour and what I noticed was that it does not eagerly recharge the battery. When you lift your foot of the accelerator, it keeps the engine running without recharging the battery. I pulled over and noticed that only after being stopped for around 5 seconds, it turned on the generator. You could tell by the sound of the engine and the arrows in the MID.

    Then I sat there with the engine running for more than 2 minutes, well after the 3rd block in the battery indicator had appeared. Then you could hear the generator stop and about 5 seconds later, the engine stopped.

    I don't have to tell how disastrous this behaviour is for fuel economy.

    Interesting difference with the Gen II: when you stop the car, the fuel consumption indicator drops to 0 if the engine is running (In Europe it displays fuel consumption, lower is better). In the Gen II it rose to 10 l/100 km, which is more correct. Also the 1-min blocks in the consumption screen showed 0 for the 2 minutes that I stood there with a running engine. The consumption is however correctly registered in the trip average.

    The equivalent behaviour for a US Gen III would be that the fuel economy goes to 100 mpg when the car is stopped with a running engine. Can anyone confirm this or does it correctly drop to 0 mpg?
     
    #9 anne1965, Aug 18, 2009
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