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Gen 2 computer and no fuel

Discussion in 'Gen 2 Prius Technical Discussion' started by T1 Terry, Sep 10, 2022.

  1. T1 Terry

    T1 Terry Active Member

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    How does the computer know when there is no fuel left in the tank or the fuel pump is not running to go into limp home mode powered by the traction battery?

    T1 Terry
     
    #1 T1 Terry, Sep 10, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    Limp-home mode isn't very different from the HV control ECU noticing how far you've pressed the go pedal, and noticing how much power the engine's producing, and using the traction battery to make up the difference, which is a lot like normal operation. The traction battery is dinky (compared to a BEV, anyway), so if the engine output is really low, limp-home is pretty much all you can get (and home had better be within a few blocks).

    If the output from the engine is so unexpectedly low that it clearly isn't starting or running well, the ECM will report a P3190 or P3191. If that happens at a time when the fuel gauge reading is very low according to the combination meter, the ECM will set an INF code suggesting that the underlying reason might kinda sorta possibly be related to running out of fuel.
     
    #2 ChapmanF, Sep 11, 2022
  3. T1 Terry

    T1 Terry Active Member

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    With the extended range battery and "ICE Kill" button pressed, the fuel pump is shut off, so I assumed there was some signal to the computer that the fuel pump was disabled or a fuel pressure sensor indicating low or no fuel pressure so the computer goes to limp home mode .... which with the 40Ah LFP battery added to the supply for the traction battery, gave around 80km travel but only 80km/h because that is te over speed limit for MG1. The computer seems to know not to spin the engine where in normal mixed mode, it would spin the engine but cut the fuel supply ..... so something must signal the computer that there is no fuel pressure .... well that is my guess anyway.

    My reason for asking was I want to use this function to see if I can turn a third motor to spin the planetary in place of the ICE spinning, there by getting around the MG1 over speed problem ......

    This is all part of my over all plan with fitting the 55Ah LTO traction battery pack and hopefully later creating a full EV Gen 2 Prius with additional cells up under the bonnet where the ICE was to improve the range further than the 120km I'm hoping for with this LTO battery upgrade.

    T1 Terry
     
    #3 T1 Terry, Sep 11, 2022
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    What is the "ICE kill" button, and does its use result in codes being set?

    I assume that if the hybrid control ecu is in a "special mode" that prevents ICE operation, then it might be programmed not to "waste" power by spinning the ICE. It would be trading (lots of) range for higher vehicle speeds.

    The engineers probably didn't want to allow that given the low capacity of the OE battery.

    I might think that trying to spin the trans input shaft via another motor would just cause the HC ecu to have a hissy fit. It wouldn't like seeing MG1 spin unless it wants that.

    Overall, if you want a full EV, you might want to look at aftermarket inverters. Or research the plugin system on the Gen3.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Sep 11, 2022
    Last edited: Sep 11, 2022
  5. T1 Terry

    T1 Terry Active Member

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    Yes, apparently the "ICE Kill" cuts the fuel pump power supply and resets the fault codes so the ECU sees a now fuel situation and goes into the "Limp home" mode.
    Just toying with ideas at the moment, the third electric motor could be fitted with what ever counts the ICE revolutions at the moment so the computer sees the ICE is spinning, the fly by wire throttle could drive the VFD for the third motor, but to avoid spinning the third motor when not required, like through the city, and it then attempting to spin MG1 to act as a traction battery charger, I was looking at just how the ECU sensed there was no fuel pressure so I could use this to switch off the power to the third motor ....

    T1Terry
     
    #5 T1 Terry, Sep 11, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    A how-it-does-that question sometimes needs to follow a whether-it-does-that question.

    I don't think it does that. There isn't a fuel pressure sensor.
     
    #6 ChapmanF, Sep 11, 2022
  7. T1 Terry

    T1 Terry Active Member

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    Thank you, that at least rules that one out.
    I know if the "ICE Kill" is used, the car needs to come to a stop, be turned off, then on again to return to mixed mode, so maybe the extended range kit does something in the ECU via the OBD2 plug which is the interface path for the kit to comunicate with the ECU.

    T1 Terry
     
    #7 T1 Terry, Sep 11, 2022
  8. Another

    Another Senior Member

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    Doesn’t B mode turn off the fuel to the ICE for downhill runs?
     
    #8 Another, Sep 12, 2022
  9. ChapmanF

    ChapmanF Senior Member

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    Don't need to be in B mode for that; the car always avoids injecting fuel when the engine is only spinning for coasting or engine braking, both of which happen both in and out of B mode. B mode biases the HV control ECU to do more of it.

    But I think that's different from the "ICE kill" the OP is interested in.
     
    #9 ChapmanF, Sep 12, 2022
  10. T1 Terry

    T1 Terry Active Member

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    What I'm looking for is a method of stopping the ECU trying to spin the ICE so the all electric mode using MG1 and MG2 are the only propulsion devices, then at around 60km/h (35mph) it would release the ICE hold to allow the ICE to spin freely.
    This way, the all electric mode will be available for round town but on say a full throttle application it allows the ICE to help drive the wheels.
    The aim is to not have the ICE spun up to act as a generator and not to be held stationary to the point the MG1 over speed becomes a problem. Once I can achieve that, I can take the ICE out and replace it with a third electric motor that would only be used when additional drive power was needs but could also act as additional regen braking when needed.

    T1 Terry
     
    #10 T1 Terry, Sep 12, 2022
  11. mr_guy_mann

    mr_guy_mann Senior Member

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    I would think that you have to rewrite the software for the hybrid control ecu. You want it to not do things it's programmed to do some of the time, but then perform as designed at other times.

    If what you want is a full EV, wouldn't it be "easier" & less complicated to just go with a single motor and matching inverter? Trying to juggle 3 motors seems less efficient to me.

    Posted via the PriusChat mobile app.
     
    #11 mr_guy_mann, Sep 12, 2022
  12. T1 Terry

    T1 Terry Active Member

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    Where's the fun in that :lol: I don't want to go down the welded planetary set up because it reduces the available torque the combination of MG1 and MG2 can produce together.
    I really like this '06 iTech pack Prius with all its upgrades, so if I can turn it into something very different without trying to reprogram the ECU but rather trick it by sending the signals that it expects to see, then why not .....

    T1 Terry
     
    #12 T1 Terry, Sep 12, 2022
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