1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Does the Prius actually have a Neutral?

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by demiller9, Mar 15, 2010.

  1. demiller9

    demiller9 Junior Member

    Joined:
    Mar 15, 2010
    8
    0
    0
    Location:
    Dallas
    Vehicle:
    2010 Prius
    Model:
    V
    Forgive me if this is a stupid question, my Prius is on order. I've read about how the Hybrid Synergy drive works, and the PSD, and don't understand the suggestion to put the Prius into Neutral to stop SUA (Sudden Unintended Acceleration).

    My understanding is that the Prius transmission has no clutch, and there is just one always engaged gear (a planetary set). So how can you put that into Neutral? I understand on the Prius Neutral is just a command to the ECU to run MG1 in a contrary manner to prevent the ICE from making the car move. Is there actually a Neutral?
     
    #1 demiller9, Mar 15, 2010
  2. wwest40

    wwest40 Member

    Joined:
    Mar 14, 2010
    518
    13
    0
    Location:
    Pacific NW
    Vehicle:
    2003 Prius
    Model:
    I
    The HSD system goes into neutral by "programming" the motor/generators to rotate COUNTER to the ICE, if the ICE is running. The HSD drive system, ICE, MG1, MG2, is NEVER mechanically "uncoupled" from the drive wheels.
     
    #2 wwest40, Mar 15, 2010
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    12,470
    6,862
    2
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    The ICE is not directly pushing the wheels, resistance from MG1 forces Engine power to the wheels. (In heretical mode, MG1 is pushing through the engine) If MG1 and MG2 are not producing or consuming power, the ICE has nothing to push against, so it turns freely.

    I use this visual aid when text is not enough

    A simulation of Prius's Planetary Gear

    You can push up the red lever alone and the wheels never turn.

    There is no Neutral in the sense of the Engine rotation not rotating the PSD, only in the sense of not rotating the wheels.
     
    #3 JimboPalmer, Mar 15, 2010
  4. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,073
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    In the simplest case, if you remove all power from the motor-generators (MG1 & MG2), all the engine (ICE) can do is spin MG1 as a freewheel. Shut off the electricity to the MGs, and everything stops.

    Tom
     
    #4 qbee42, Mar 15, 2010
(You must log in or sign up to post here.)