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For What It's Worth: Interesting

Discussion in 'Gen 2 Prius Technical Discussion' started by EZW1, Mar 16, 2009.

  1. EZW1

    EZW1 Active Member

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    Four Touring
    Today I took the Pri in to Discount Tires to get the LR tire repaired: I picked up a screw in the tread and lost 8lbs over the weekend.. I didn't want to leave the keys with them and they obliged, allowing me to pull it into the service bay and back out. When I pulled in, they had me pull up and over a platform that would lift the car from under the frame rails. I had to drive the front wheels up a short incline, across the elevated rail, and back down the other side.

    I found I had to depress the pedal quite a bit to create enough torque to get the front wheels up and over the ramp. I would say I depressed about 1/8 to 1/4 way. No problem.

    What was most interesting, however, was when it was time for me to pull it out. When I started the car and got the ready light I put it in reverse. I depressed the pedal and the found I had to press harder, harder, and even harder to get the front wheels to back up the ramps and proceed to continue its rearward movement. I ended up depressing the pedal about half-way down before I was able to get enough torque to back the fron wheels up the ramp - but even more interesting: this process took 30-sec or so (I didn't want to 'goose' it up the ramp) and normally during that amount of time the ICE has already kicked in. Mine didn't! The ICE didn't kick in until I got the front wheels up the ramp on the elevated platform and I backed way off the pedal again. Almost like a safety feature/self preservation feature to prevent HSD damage with such a high demand for power.

    I found this interesting.

    Oh, and by the way, since I was such a long-time customer with Discount Tire (I've purchased tires from them for my last 5 cars over the years), they did the entire repair job on my Goodyear Infinity at their cost! The job required them to remove the wheel, remove the tire from the rim, patch it from the inside, remount the tire, fill, leak check, balance, remount back on the car, and then set all 4 tires to 40psi for me. Nice guys!
     
    #1 EZW1, Mar 16, 2009
  2. nwprius

    nwprius Member

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    The Prius uses only the Electric motor for backing up. The gas engine does not help.
     
    #2 nwprius, Mar 16, 2009
  3. donee

    donee New Member

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    Hi All,

    I had this experience too. The shop guys could not get the car backwards over the ramp. What I think is going on is that for the first minute the car is turned on its in Stage 1, and it does not load the engine with MG1 much. So, its all battery to move the car backwards. Then as Stage 1 warmup completes, the engine is enabled to provide torque to MG1, and there is enough umph to get the car backwards over the steep ramp.
     
    #3 donee, Mar 16, 2009
  4. patsparks

    patsparks An Aussie perspective

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    ICE doesn't help at all in reverse, only MG2 provides torque to the wheels in reverse.
    In future go forward a little first so you hit the ramp moving.
     
    #4 patsparks, Mar 16, 2009
  5. qbee42

    qbee42 My other car is a boat

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    To add a little more detail, all of the reverse torque comes from MG2. If MG2 is powered only from the battery, then all of the power from MG2 is used to move the Prius backward.

    It gets more interesting if the ICE kicks on. When the ICE runs during backing, it supplies electrical power to the wheels via MG1 to MG2. The ICE spins MG1, which makes electricity, which is then used by MG2 to move the car. This all makes sense, but here is where it gets tricky. Only part of the torque from the ICE is used to spin MG1. The rest of the torque tries to mechanically drive the car forward. To move backward with the ICE running, MG2 has to overcome the mechanical torque from the ICE as well as any resistance from moving the car.

    Tom
     
    #5 qbee42, Mar 17, 2009
  6. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    yep had this happen and rocking it with a bit of a run (albeit even if only a few inches) always did the trick for me and i doubt if any damage was done.

    as far as free tire repair, we have Les Schwab that offers the very same thing and YOU DO NOT HAVE TO BUY THE TIRE FROM THEM.

    in my 04, due to construction in my neighborhood, i had 2 flats repair by them at no cost.
     
    #6 DaveinOlyWA, Mar 17, 2009
  7. EZW1

    EZW1 Active Member

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    So, this indeed was an interesting experience. Had I waited until the ICE kicked in before backing, I would've had more difficulty backing the front wheels up the ramp?
     
    #7 EZW1, Mar 17, 2009
  8. Bob64

    Bob64 Sapphire of the Blue Sky

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    Well, at least then the electricity generated by MG1 would then supplement the power coming from the battery, thus giving you even more torque at the expense of higher speeds....
     
    #8 Bob64, Mar 18, 2009
  9. qbee42

    qbee42 My other car is a boat

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    Exactly. The ICE fights MG2, but also sends more power via the MG1-MG2 electrical path. The net result is more power for backing up, but at reduced efficiency. Fortunately we don't spend much time backing up.

    Tom
     
    #9 qbee42, Mar 18, 2009
  10. Politburo

    Politburo Active Member

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    I figured this was common knowledge, but I guess not everyone lives on a street with >10% grade and no driveway... Sometimes you have to floor it just to move.
     
    #10 Politburo, Mar 18, 2009
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