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46 MPH is the new threshold for STEALTH

Discussion in 'Gen 3 Prius Main Forum' started by john1701a, Jun 1, 2009.

  1. john1701a

    john1701a Prius Guru

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    I've had a ScanGaugeII for 2 years now, so when something is different you notice... but I wasn't expecting surprises like this when I connected it to my 2010.

    Briefly hitting a LOD of 70 is the highest I had ever experienced with my 2004. So, seeing it shoot past 90 then settle in the 80's sure got my attention. Now when cruising through the suburbs I'm seeing double the engine load of what I'm use to. Yet, it's quiet & efficient. What the heck did the engineers do? Something clever.

    But to my delight, that wasn't all. RPM stayed at 0 until 46 MPH. I thought I had lost my mind momentarily. But sure enough, it did it again! That explains the unusually easy cruising in stealth at 40 MPH. The threshold isn't 42 anymore. Sweet!
    .
     
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  2. bestmapman

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

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    Yea I saw that today also. Here is a pic of one I took.
     

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  3. DeanFL

    DeanFL 2010 owner - 1st Prius

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    Can someone please translate this into English? Non-Prius-tech speech for us wannabees. Sounds interesting and exciting - whatever it is.
    :confused:
     
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  4. bestmapman

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

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    Stealth is a mode of operation where the ICE (Internal Combustion Engine) is shut down. You can use EV for some propulsion, but most of us use it to glide(coast) in this mode. The Gen II stealth limit was 41 MPH. The Gen III limit is 45 MPH. This is a huge improvement.

    When you hear talk about P&G (Pulse and Glide), the glide portion is stealth mode.
     
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  5. DeanFL

    DeanFL 2010 owner - 1st Prius

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    Aha! So - if you're driving under 45 MPH and let up on the accelerator, the ICE will shut down. Does it do this immediately or delay a bit to allow for minor driving fluctuations - ie getting a bit too close to the car ahead. The delay would minimize unnecessary quick shutdown and startup. On the other hand, coasting to a stoplight = ICE down and regenerative braking charging the battery, right? And there's no drag from the engine as a "normal" car?
     
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  6. john1701a

    john1701a Prius Guru

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    Study the PSD.

    You'll see how the engine can stop moving, because the power-carriers for it don't. They'll continue to rotate even though the assembly itself stops revolving.

    It's quite clever.
    .
     
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  7. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Nice! You will get a wider speed range to P&G. I believe the Fusion hybrid has the same 47 MPH limit.
     
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  8. bestmapman

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

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    John is right, and he has some very good graphics on his site that explain the HSD operation.
     
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  9. msirach

    msirach Member

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    If you get it to drop in stealth (ICE off-0rpm) before 46, hold your foot steady (or kick it in neutral) and glide forever. I dropped into stealth tonight and glided up to 58 mph before I started a climb and had to light the ICE.
     
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  10. CAR4TWO

    CAR4TWO New Member

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    I just love free energy. I live in Southern Oregon where 6% grades for 6 to 8 miles is the norm. Right now I just put the car in neutral and coast. I have to tap the brakes to stop accelerating. My MPG shoots up to 99.9. The fun part is matching the RPM with the cars speed when you put it back in gear. I have done that so many times it feels seamless.

    Dan
     
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  11. msirach

    msirach Member

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    I was on a 7% a couple of days ago and you will LOVE the glide of the 2010. What makes it even better is the fact that it will enter a glide VERY easy. A very slight decline will get you a steady glide for a good distance.

     
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  12. Husker4theSpurs

    Husker4theSpurs Active Member

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    That IS awesome! So now I can keep the engine off up to 45 mph ... used to be driving on 35mph roads was the route to best FE, but now we'll be able to glide steathily along at higher speeds!

    Thanks for the translation!
     
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  13. royrose

    royrose Senior Member

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    I don't have a Prius yet, so I would like to know a little more about how the shifter works. After you go into drive by moving the shifter to the left and down, I assume, because it is a "joystick" design, that it returns to it's original position. To "kick it in neutral", do you then just tap it to the left?

    The Car and Driver negative review said it was hard to find neutral. Thanks.

    Roy
     
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  14. msirach

    msirach Member

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    It's very easy to hit neutral. As you mentioned, tap the shifter left and it goes into neutral.
    The Car and Driver staff must have been blind and had paralyzed arms.

     
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  15. bestmapman

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

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    You hold the shifter to the left and hold it there for a split second. It is not hard to find neutral at all.
     
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  16. Foulwx

    Foulwx New Member

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    As a newcomer, I would like to know if the glide is where the wheels rotating are recharging the battery. If you go to neutral, do you stop recharging the battery, and why would you do this?

    Thanks for the info in advance..
     
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  17. bestmapman

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

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    Glide is where you are not using any energy and not replacing any energy. Think of a skateboard. The pulse is when you push off and the glide is when you are just riding. In this condition, you are not using any energy out of the gasoline or battery and you are minimizing drag by not regenerating and energy back into the battery.

    In neutral, you are not charging or regererating.

    Hope that helps.
     
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  18. efusco

    efusco Moderator Emeritus
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    The teminology we commonly use is a bit different from what you state above.
    Coasting-When you lift you foot off the accelerator. There is some regen that takes place here and the car slows down at a gradual rate.

    Gliding-When you lift your foot off the accelerator then depress it slightly to reduce regeneration. The car is basically free wheeling here and thus will slow at a more gradual rate than when coasting.

    Neutral-basically a perfect glide where you don't have to manually input on the accelerator to assure no regen.

    In order to understand the "Why" you must remember the concept of conservation of energy/momentum. If you regen you are braking and converting kinetic energy (forward momentum of the car) to potential energy (stored in the battery). While doing that when you MUST slow down or stop is better than wasting that kinetic energy as heat with friction braking, it is not as good as maintaining that kinetic energy by free-wheel gliding/neutral gliding to make maximum use of the energy it took to get the car up to speed in the first place.
     
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  19. rainman1000

    rainman1000 New Member

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    Thanks for the explanation. As a newbie still waiting for my Prius, I finally understand how pulse and glide really works. It doesn't seem to be as hard to do as I previously thought.
     
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  20. ken1784

    ken1784 SuperMID designer

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    Thank you for the very interesting 46 mph threshold.
    Has anyone found any speedometer offset, display vs actual(or GPS)?

    Japanese 2010 Prius has 5km/h (3 mph) offset.

    Ken@Japan
     
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