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MFD shows incorrect engine status

Discussion in 'Gen 2 Prius Technical Discussion' started by carz89, Jul 22, 2008.

  1. carz89

    carz89 I study nuclear science...

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    Occasionally (I would say about 10-15%) of the time, the MFD in my Prius shows the wrong engine status. For example, sometimes during the latter stages of engine warmup, when I can definitely hear and feel that the engine is on, the Energy Monitor screen will show the engine is off, with no energy flow to/from the engine. At the same exact time, the instantaneous MPG on both the Consumption and the Energy Monitor screens will show a number less than 99. This isn't a "split second" thing either, as it will last for a minute or more.

    Does my Prius have a split personality? The left side of the MFD brain is correctly calculating the MPG as less than 99 (proving that the engine is running). At the same time, the right side of the MFD brain thinks that the engine is off.

    I'm thinking that this is a bug in the software (common to all Prii), or that there is a minor defect in my Prius' MFD system.

    Anyone else experience inconsistencies with the MFD engine status?
     
    #1 carz89, Jul 22, 2008
  2. efusco

    efusco Moderator Emeritus
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    The cartoon on the Energy screen is not an accurate representation and what you're observing is normal...the threshold for showing the ICE operating or energy flow are not 100% accurate and, as you've observed, the ICE maybe running at a low idle but no arrows will show on the screen.

    If you really want to know what's going on you should invest in a ScanGuage (see Priuschat Shop)
     
    #2 efusco, Jul 22, 2008
  3. echase

    echase New Member

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    While this is a totally normal, I'm not sure it is actually inaccurate. The engine is running, sure, but do we know that energy is flowing from it during that state? The screen alleges to show energy flow not ICE state. You could also add a tachometer, or do one of Hobbit's many mods.
     
    #3 echase, Jul 22, 2008
  4. qbee42

    qbee42 My other car is a boat

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    The MFD does not show engine status; it shows power flow. The engine can run without power flowing to the battery or wheels.

    Tom
     
    #4 qbee42, Jul 22, 2008
  5. carz89

    carz89 I study nuclear science...

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    If that's true, then it seems like a waste. I've seen the engine running, with no indication of energy flow, and the battery only at 5 or 6 bars. If the computer decides that the engine should run to warm itself up, then why not turn the MG and charge up the battery too? Given the same amount of throttle, the engine would heat up just as fast if it also charged the battery.

    What bothers me is that I can't figure out a reason for the apparent inconsistency. I pay close attention to my MFD, probably glancing at it for a split second a few times a minute. Like I said, I've witnessed my described situation only about 10-15% of the time. Usually, the MFD shows what I expect. During engine warmup and the battery less than full-charge, I'll see energy flow from the engine to the battery if the car is still, or energy flow to the wheels for propulsion.
     
    #5 carz89, Jul 22, 2008
  6. richard schumacher

    richard schumacher shortbus driver

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    In this case the engine is probably running to finish heating itself or the catalytic converter to optimal operating temperature. The battery is evidently already at its optimal state of charge at that time, so further charging would reduce its lifetime by some trifle. If the engine is running anyway one might as well drive the car at that time, to get some useful work out of it.
     
    #6 richard schumacher, Jul 22, 2008
  7. hc167

    hc167 Member

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    I obviously do not designed the prius. but base on my observation. I think when engine is on while there is no energy flow. that usually mean that the computer of prius detect that the engine is not hot enough and need to run the engine to make sure it reach the normal operating temperature. This piece of energy is waste. So this will happen more often in winner then in summer. of course this also mean that you are burning gas. and therefore, mpg will slowly reduce.
     
    #7 hc167, Jul 22, 2008
  8. Rest

    Rest Active Member

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    Here is something that may be an error. When I drive in that sweet spot, no arrows, and watch my SG2 the battery SOC goes down some. This tells me battery power is being used but it shouldn't be when there are no arrows showing.
     
    #8 Rest, Jul 22, 2008
  9. Leo

    Leo Leo

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    Yes, I've seen many times where I am stopped for a red light, the engine is not running, the car is not moving, but I see an energy flow (arrow) running from the battery to the wheels. This usually happens when the car had been warming up the catalytic converter before ICE shutdown. I know the engine is not running because I experience the "shudder" when the ICE sheds its momentum and stops.
    I suspect that it's actually showing energy running to something else from the traction battery, but I have no idea what is really happening.
    Initially I thought the car was heating up the catalytic converter electrically, but I now know this doesn't happen (but I think it might be a good idea...)
     
    #9 Leo, Jul 22, 2008
  10. Sheepdog

    Sheepdog C'Mere Sheepie!

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    I have learned that when you are in stealth with no arrows you still are using a little battery energy. How much exactly I dont know but it is some.
     
    #10 Sheepdog, Jul 22, 2008
  11. JimboK

    JimboK One owner, low mileage

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    Not an error, just the way it's designed. It's not a precision device.

    However, you are correct that there is current flow out of the battery during a sub-41 MPH no-arrows condition -- a "glide" as most of us regulars in these parts call it. There appears to be a more-or-less linear relationship between current flow (up to 8 amps) and vehicle speed when using go-pedal feathering. On the other hand, using neutral to glide uses considerably less current and maintains SOC longer, though at the price of slightly increased drag. See this for more.
     
    #11 JimboK, Jul 22, 2008
  12. hc167

    hc167 Member

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    yes, when the car is not moving and you step on the brake. there is an arrow from the battery to the motor. that is normal. because it is powering the motor. why is that, because you did not step on the brake hard enough. do two tests, when you see this happen next time, either hit the "park" button or hit the brake harder. that will deactivate the power from battery to the motor. it is just like regular car when you stop at "D", the engine try to move the car but your brake try to stop the car. prius try to simulate this by activate and deactivate the motor at the position of the brake that you step on.
     
    #12 hc167, Jul 22, 2008
  13. richard schumacher

    richard schumacher shortbus driver

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    The cartoon only shows energy flows within the drive system. Energy flow out of the battery to the A/C, lights, accessories, etc. is not shown.
     
    #13 richard schumacher, Jul 24, 2008
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