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Another Dumb Question

Discussion in 'Gen 2 Prius Main Forum' started by berryman, Aug 18, 2004.

  1. berryman

    berryman Junior Member

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    I'm new to the forum and you probably all know the answer to this - BUT - are there driving situations that cause the computer to engage both the gas and electric motors simultaneously, such that the Prius operates at its full, combined 130 + HP rating?
     
    #1 berryman, Aug 18, 2004
  2. obiwan

    obiwan New Member

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    I'm not an expert in this area, but I believe that if you push the Prius to it's maximum theoretical speed, the hybrid system is fully engaged.

    If I remember right, that happens at about 102 MPH or so.
     
    #2 obiwan, Aug 18, 2004
  3. efusco

    efusco Moderator Emeritus
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    No, those horsepowers are not additive that way.
     
    #3 efusco, Aug 18, 2004
  4. obiwan

    obiwan New Member

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    Right - I didn't mean to imply that the HP's sum totaly... but at 102 MPH you are geting as much from the system as it is able to give.. about 100 HP or so.

    Someone on here reported getting the car up to 104 MPH, but that was going downhill in the Rockies (if I remember right)
     
    #4 obiwan, Aug 18, 2004
  5. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    Couple of things:
    * Top Speed doesn't always equal horsepower. In the Prius case, it's limited by the maximum speed of MG2 (the traction motor).
    * The Prius doesn't have 130hp+ net as we can't add the electric and gas engines together. The gas engine produces 76hp by burning gasoline. The Electric motor can produce up to 67hp - however it's energy source is either the gas engine or the battery pack.

    Therefore, in our case, we can only take the HP generated by the engine (76HP or 57kW) and the theoretical HP delivered by the battery (approx 28HP or 21kW), and add them together. That makes about 104hp.

    The electric motor is rated at 67hp or 50kW. Even though the Electric motor peaks out at 67hp, 39hp (or 29kW) of that must come from the ICE via MG1 (the generator) if we know the other ~28hp comes from the batteries.

    Funny thing is the net HP rating is 110hp at prius.toyota.com, which converts to 82kW. However, the engine produces 57kW and the batteries only 21kW, where does the other 6hp/4kW come from?! Temporary 4kW of capacitor burst in the inverter?

    Inquiring minds want to know!

    As for when the Prius would make the max power, the engine would need to be able to rev to 5000 RPM, while keeping MG2 at 1200-1540RPM (where it reaches 67hp), all without overspinning MG1 (generator) beyond 10,000 RPM. Honestly, I'm not sure that's truly possible. However, I'm sure that when the ICE can reach 5000 RPM which occurs at a bit over 50mph, MG2 can still easily produce/convert 28hp + whatever MG1 is feeding it.

    Again, Wayne's palm program would be uber-useful about now.
     
    #5 HTMLSpinnr, Aug 18, 2004
  6. berryman

    berryman Junior Member

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    Based on the previous responses, is it fair to assume that the most HP the prius is likely generate when say, climbing a 5% grade, is upwards of 104HP? If so, that may explain the comments I've seen on some other posts referring to the high RPM noise that's produced when the Prius is under a continuous load navigating mountaineous terrain.
     
    #6 berryman, Aug 18, 2004
  7. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    If you were flooring it, yes.

    Once the battery drains down and you were on ICE power only (only happens rarely if you're really pushing it up say, Pikes Peak), you'd be getting 76HP or less - less because some of the energy would be diverted to recharging the battery, running the A/C (hopefully not), etc. etc.

    Though now that you mentioned climbing a grade - you'd probably be making less due to altitude, etc.
     
    #7 HTMLSpinnr, Aug 18, 2004
  8. hdrygas

    hdrygas New Member

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    I just drove my car home and went over 4 passes with good sized grades. The ICE was never overly loud nor did it seemed over reved. I always had power in reserve (had to try it out in the interest of science and public safety). Ended up at the top with 3 or more bars on the battery. Never topped the battery out was always one short on the down hill portions. I would reach the summit at the speed limit and coast in D down when I was 5 or so over I but it in B till I was 2 or 3 under then back to D till the grade was less then used a light touch on the breaks in D. I don't think I was using the friction brakes at all. Loved cruising at 65 or so at the bottom of the hills in stealth mode for a while that was a kick. All in all there was not a lot of noise at any point. Much less than my old Fiat 124 over the same pass.
     
    #8 hdrygas, Aug 18, 2004
  9. daniel

    daniel Cat Lovers Against the Bomb

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    This is just my opinion, but is backed up by Henry's report:

    The 76hp ICE is plenty powerful enough to keep the car moving at the speed limit up a normal mountain highway grade. If the SOC is high, the computer (not knowing the length of the hill) will draw down some battery charge, but once the SOC is lower, the computer will place all the work on the ICE, maintaining charge in reserve. Then when you need to accelerate up the grade (to pass that SUV) you have the full power of ICE + battery.

    If you kept accelerating hard, you'd run down the battery, but by the time that happened you'd have reached the car's maximum governed speed. You cannot accelerate forever.

    The electric portion of the hybrid system is there for load balancing and for acceleration. It's never needed to maintain speed, even up a grade.

    As for the original question, if you floor it from a standstill, it sure feels like it's putting out a goodly part of that 110 hp.
     
    #9 daniel, Aug 18, 2004
  10. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    That's good 'ol Torque you're feeling though, not HP :)

    There's a saying - HorsePower sells cars, but Torque wins races. (drag at least)

    Then again, HP is simply torque compared to time and perhaps distance.

    HP = (Torque*RPM)/5250
     
    #10 HTMLSpinnr, Aug 18, 2004
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