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CVT slipping or ????

Discussion in 'Gen III 2010+ Prius Main Forum' started by njmurvin, Apr 7, 2010.

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  1. njmurvin

    njmurvin Member

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    I have had my Prius for a couple of weeks. I looked at some of the other "slipping" threads and didn't find one that fits. I notice sometimes after takeoff, it seems like the trans slips just a bit. Today, I think I detected that it may be the transition point where the ICE kicks in. Does anyone else feel this and could it explain my "slip" feeling?
  2. 3PriusMike

    3PriusMike Prius owner since 2000

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    It would probably be hard for the CVT to slip. It it a system of planetary gears. More likely there is some hesitation of some kind. Does this happen when the car is cold?

    3PriusMike
  3. yardman 49

    yardman 49 Active Member

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    +1

    Depending on the amount of acceleration and/or torque required, coupled with the state of charge of the traction battery, the ICE may have to spin at a higher RPM, which gives the audible cue that the engine is "racing", even though the car may not be accelerating as quickly as the "sound" would indicate. This then creates the illusion that the tranmission is slipping.

    There is no clutch of any sort on the Prius, hence the conventional concept of "slipping" would not apply.

    Best wishes,
  4. hsiaolc

    hsiaolc New Member

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    I doubt it is slipping. CVT is one big gear train with no 1st gear or 2nd gear to switch to but a infinite number of gear ratios, hence you don't feel any gear switch with CVT hence it is called Continuously Variable Transmission.

    Like you said yourself it is just ICE Kicking in.
  5. donee

    donee New Member

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    Hi njmurvin,

    "Slip"ing relates the action of a clutch in an automatic transmission. The clutch begins to slip , when it is commaned to hold. This causes the engine to rev way up, and the car to not accellerate quickly.

    Its impossible for the Prius transmission to "Slip" as there are no clutches in the transmission at all. Its a system of gears and motors that are in the same mechanical configuration all the time.

    The Prius programming is set to make for operation of the engine in the most fuel efficienct RPM for the power commanded. This can be very high, due to the internal aerodynmics of the engine.

    In fact, the ability of the Prius to run the engine at a high RPM at low speeds is part of what makes the Prius quick at those low speeds, for its engine size. A traditional automatic transmission does not have a gear ratio that allows the engine to reach high RPM at low speed, and since power is proportional to the RPM times Torque, high RPM at low speeds allows the engine to run at a higher power than traditional cars. This means the Prius can have a smaller engine, for the same low speed engine power.

    A 6 or 7 speed automatic transmissions have become available since the Prius was first designed. Such transmissions can allow the engine to have best low speed gearing to the wheels, but these are quite complicated and cost extra. High end cars have have these now, to improve fuel economy such as a Mercedes R class. The Prius transmission achieves the same if not more range of shaft speed reduction ratios as these transmissions, with a much simpler, robust design, that is much less expensive.
  6. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Prius does not have transmission -- nothing slip, shift, disengage or re-engage. The drivetrain goes from -25mph to 112mph in a single gear. Therefore, there is no need for different gear ratio.
  7. njmurvin

    njmurvin Member

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    Thanks everyone. Yes, I noticed it when cold. You have convinced me that it's the ICE coming on to add some ooomph - as I was beginning to suspect..
  8. hsiaolc

    hsiaolc New Member

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    There are gear ratio. Infinit gear ratio infact.
  9. usbseawolf2000

    usbseawolf2000 HSD PhD

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    The gears in the PSD never change. The rotation speed may change but they remain in one gear ratio.
  10. V8Cobrakid

    V8Cobrakid Green Handyman

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    when your prius starts up, it tries to take the load off the ICE (gas engine) so it can warm up properly... during this time your car will use more electricity and may run the ICE at higher speeds to get a better charge going. after it warms up, the "slippage" will be less.

    if your battery has a lower charge during this time, the slippage gets worse.. as the engine has to run at a higher rpm to charge up the battery....

    it seems like it's really just a warm up thing....
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