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Refusal to 'glide' at highway speeds?

Discussion in 'Gen 2 Prius Technical Discussion' started by shtinkypuppie, Apr 1, 2009.

  1. shtinkypuppie

    shtinkypuppie Junior Member

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    Hello,

    I have noticed some strange behavior from my 2009 non-touring Prius lately. After driving about 3 miles (and making sure I'm in S4), I get on the freeway. Usually the first 'glide' (engine off, 'warp stealth', whatever it's called) or two go normally, with the engine turning off promptly (as confirmed by the 0.00 GPH on Scangauge and the MFD). Sometimes, however, I will release the pedal and then feather it just like I do for every glide, and the engine stays on. When I feather, the MFD shows power coming from the engine to the wheels and charging the battery, and my GPH reading goes from ~0.25 (idle) to ~0.43. No matter how long I let off the gas pedal before feathering or how gently I feather, the engine stays on and powers up when I feather. Usually after 2 or 3 attempts I've lost enough speed to need another pulse, and afterward she glides normally. Engine temp is not low, usually about 85C. I usually have plenty of SoC (6 bars). Nothing else (that I can tell) is out of the orginary that might cause this. It usually occurs within just a few minutes of getting on the freeway, after one or more successful glides. Is there something I or Rachel is doring to prevent a glide? If so, how might I prevent this?

    Thanks in advance for any insight.
    Eric
     
    #1 shtinkypuppie, Apr 1, 2009
  2. firepa63

    firepa63 Former Prius Owner

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    What speed are you driving? If you're above 35 or 37 mph, whenever you call for any power, the ICE will run. My advice is don't use P&G on a freeway. Use it on lightly traveled side roads.
     
    #2 firepa63, Apr 1, 2009
  3. donee

    donee New Member

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    Hi Stinky...,

    The Prius never glides at highway speed. It will go into warp stealth (yellow arrows) down hill if your less than 62 (64?) mph. In Warp Stealth, the engine is turning over, but no fuel is pumped, and the battery/motor(s) is pushing the car along, as well as turning over the engine.

    Due to the impose limit on the MG1 RPM, the second generation Prius can only enter glide below 40 mph. Above that speed for the engine to stop turning, MG1 would have to spin faster than 6000 (and some?) RPM.

    The best highway mileage is obtained using only the engine, and at the lower RPM to maintain a steady speed. This is called SHM, or super highway mode by many people. Knowing what RPM is the minimum needed in a given situation is a bit of an art. But in warm weather, level terrain without wind, 53 mph and 1280 RPM works quite well - about 70 mpg.
     
    #3 donee, Apr 1, 2009
  4. shtinkypuppie

    shtinkypuppie Junior Member

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    Firepa, Donee;

    I am aware that the ICE must spin at these speeds. However, I am wanting it to go into fuel cutoff and 'warp stealth'. Instead, the engine is continuing to burn fuel and applying power when I want it to just use electric power.
     
    #4 shtinkypuppie, Apr 2, 2009
  5. Bob64

    Bob64 Sapphire of the Blue Sky

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    another thing that may prevent a glide:

    coolant transfer from the engine to the thermos when you hit 85c. It stores excess heat this way, but prevents it from shutting down the engine while this happens. It may take a minute or two for it to switch back to stage 4.
     
    #5 Bob64, Apr 2, 2009
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  6. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

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    Hi shtinkypuppie,

    I think most of us here had the same initial thought. You can't glide above 40 MPH. We usually refer to, Glide as engine off operation below 40 MPH when the ICE actually stops spinning. Warp Stealth is what is used above 40 MPH, when no fuel is going into the engine, but the engine is still spinning.

    I think what you are refering to is warp stealth, and not being able to obtain WS. Even though you are saying the engine turning off at highway speeds it is still spinning.

    If I get this straight. You are having trouble getting into warp stealth and are using GPH on the scan guage as confirmation entering WS (Glide engine off as you say). What I do to obtain WS is back off the Go Pedal (accelerator) and apply slight pressure to make regeneration go away. Most of the time, this will give a WS condition, when it does not, and sometimes it does not, I hold that condition anyway as the instantanious MPG is very high. You are correct in that it is difficult or it is not possible to enter WS. This occurance is normal.

    Hope this helps. We here sometimes don't realize that we have developed a pretty specialized lingo and if you don't use the terms as we do, we can get confused.
     
    #6 bestmapman, Apr 2, 2009
  7. shtinkypuppie

    shtinkypuppie Junior Member

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    This makes perfect sense, actually, since the engine would usually be getting to that temp around that time, and because it's so transient. I will note the engine temp next time it occurs. Thanks very much.
     
    #7 shtinkypuppie, Apr 2, 2009
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