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ECCVT system.

Discussion in 'Gen 2 Prius Technical Discussion' started by Brooks Wilson, Jan 31, 2007.

  1. Brooks Wilson

    Brooks Wilson New Member

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    I just bought a 2007 Prius. It surges while driving at a constant speed, in or out of cruise control. I feels like depressing and depressing the accelerator on a standard car. It is very noticable and distracting. I feel certain that it is relate to the interaction of the electric motor and gas engine. The service technician told me that all Prius' do that but I've yet to find an owner who says so. Other than that, I love the car.

    Any advice would be appreciated.
    Brooks W. Wilson
     
  2. qbee42

    qbee42 My other car is a boat

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    I've never felt anything like that with ours, but perceptions can vary. Ask to drive another Prius, just to test the feel.

    Tom
     
  3. efusco

    efusco Moderator Emeritus
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    "very distracting"? What speeds does this occur at?

    This doesn't sound normal. At speeds around 41mph you may feel the ICE spin up and may sense it kick off as your speed varies slightly or accelerator pressure is applied (by you or the CC). At speeds below 41mph you may feel it kick on and off as you accelerate or decelerate b/c the ICE will start and stop as needed. Above 41mph the ICE is constantly spinning and there should be no way to feel it change.

    The only other thought I have is if you might be driving in "B" mode...the deceleration of the engine braking will be much more noticable. If you are driving in B...then stop doing it, use D only. There is very very little use for B mode.
     
  4. Brooks Wilson

    Brooks Wilson New Member

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    <div class='quotetop'>QUOTE(efusco @ Jan 31 2007, 12:13 PM) [snapback]383330[/snapback]</div>
     
  5. Brooks Wilson

    Brooks Wilson New Member

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    It occurs at any speed where I'm holding it constant. It's not the b mode. I only use that at stop signs when I have no one behind me and I want to avoid using my brakes. It's most noticable between 50 and 70 (I haven't exceeded 70 mph yet). When it is happening, I can see the battery to wheels yellow line flashing on and off. I'm scheduled for a test drive with a rep tomorrow. I've asked to drive another one but they won't accomodate me.
     
  6. efusco

    efusco Moderator Emeritus
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    <div class='quotetop'>QUOTE(BrooksWW @ Jan 31 2007, 01:01 PM) [snapback]383395[/snapback]</div>
    No way you should feel any surging at those speeds. What kind of 'rep' are you test driving with? It should be a qualified tech/mechanic, not a sales creature.

    Also, don't use B-mode, use the brakes...even when coming to a stop. If the ICE hasn't shut off yet B-forces it to stay on, you get no benefit and just risk forgetting and leaving it on.

    There are is a ton of info on the site about how and why B- is almost always a worse choice than just using the brakes, but suffice it to say that unless you must control your speed down very long steep inclines there's really no reason to use it.
     
  7. Brooks Wilson

    Brooks Wilson New Member

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    <div class='quotetop'>QUOTE(efusco @ Jan 31 2007, 02:39 PM) [snapback]383427[/snapback]</div>

    Thanks for the info and advice. It's a pain fiddling with the lever anyway. I'm testing it tomorrow with a factor technician or so they tell me. The local technician just tried to con me. I hope they can fix it because otherwise, I love the car.
     
  8. brick

    brick Active Member

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    Yeah, this doesn't sound right. The drivetrain on mine is smooth as silk unless the ICE is switching on or off. The only other time I feel any surging is when it's running at a fast idle in park. It makes me wonder if one of the other systems is screwed up, like maybe one of the hydraulic brakes applying and disengaging for no reason.
     
  9. donee

    donee New Member

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    <div class='quotetop'>QUOTE(BrooksWW @ Jan 31 2007, 07:15 PM) [snapback]383523[/snapback]</div>
    Hi Brooks,

    Are you talking about the speed surging, or the engine? If the engine is surging, that is normal. The speed stays within a mph, but the engine and HSD systems is constantly changing to control that speed. The engine will surge when allot of power is needed, and then the electric regenration will kick in when the car needs to pull energy out (like going downhill, or being dragged by a truck's aerodynamic wake) to maintain speed.

    For example your on a slight downhill at 60 mph, and the car is in electric mode. The road then slopes up. In response the engine will come on and supply allot of power to the front wheels. There may also be an extra burst of electric power as the engine throttles up. The torque reaction of the front wheel drive axles will cause the car to raise up a little bit in the front. Then as you crest the hill onto a level surface the engine powers way back. The cruise control has a very fast reaction time primarily because it has motors. The motors are very quick reacting. It will vary the power requirement as fast as road loads on the car require, and it will use full throttle power from the engine and batteries if needed to maintain the set speed.

    Sudden application of full power can cause the nose of the car to move around a little, too. Is this what you are talking about?
     
  10. Brooks Wilson

    Brooks Wilson New Member

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    <div class='quotetop'>QUOTE(donee @ Jan 31 2007, 06:29 PM) [snapback]383554[/snapback]</div>

    No. It happens when I'm on a level grade at a constant speed. It feels like I'm gently pressing the accelerator up and down. The speed doesn't change enough to be reflected on the speedometer but you can feel the pressure pulling you back into your seat. When this happens the yellow dotted line on the energy monitor showing the energy flowing from the electric motor to the wheels is flashing off and on at about one second intervals.

    Thanks for responding. I'm taking it in today with a little more information. So far, all they have done is drive it and they tell me it is normal, all Prius' do it but I have reports from four prius owners who haven't experienced it. I've asked to drive another one to see if it duplicates the problem but they have avoided it with the excuse that they don't have one available (I know they do) or I wouldn't be permitted to drive it on the freeway anyway. I'm convinced that it is an agency problem more than a Toyota problem.
     
  11. KTPhil

    KTPhil Active Member

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    I have some doubts about this... I wonder if you really feel it or if it is the sound and visual changes that make you THINK you feel it. I don't mean to be dismissive to you, but consider that if it changed 1 MPH in 1 second (and you say you don't see the speedo change so its less than that), than that is about 1/22g (less than one twentieth the force of gravity), which would be a very slight change indeed, probably not detectable in the bumpy environment of a car on a road.

    Can you try cruising as a passenger, with earplugs and blindfold on (or just block the MFD and speedo displays), and see if you can still feel it?
     
  12. John in LB

    John in LB Life is good

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    <div class='quotetop'>QUOTE(KTPhil @ Feb 1 2007, 12:19 PM) [snapback]384056[/snapback]</div>

    First time I read this I thought you were saying that the driver should wear earplugs and a blindfold to see if he can sense the surging....

    WOKE me right up! and read it again... :p :eek:

    Phew.... thank G-d we don't have drivers doing that kind of testing.... can you imagine... :blink:
     
  13. KTPhil

    KTPhil Active Member

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    Well, judging by the "driving" behavior by some I wonder if there are those conducting this experiment from the driver's seat...
     
  14. daveleeprius

    daveleeprius Heh heh heh you think so?

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    I too have noticed this, normally on the highway when I'm trying to maintain speed. For some reason the car gets into a funk and does tend to surge a little. It's not smooth as silk in this case, and it is somewhat distracting. My parents 97 Camry XLE is a lot smoother in this regard.

    I tend to be a somewhat aggressive driver at times, especially on the freeway, and the thing that bothers me the most about this car is the huge lag between coasting and acceleration. When I change lanes and press down on the gas somewhat hard to get out of the way of the guy behind me, the car hesitates. I got honked at the other day because of that.

    Dave
     
  15. KTPhil

    KTPhil Active Member

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    I got in trouble with a certain now-absent poster when I suggested that there is a lag, so proceed at your peril!

    I noticed it when coasting at about 10-15mph (approaching a right-turn onramp), then mashing the pedal (to go up the ramp to the freeway). I could count 1-2 before there was significant acceleration. It is not a total lack of accel, because the electric motor tries its best and is so smooth you don't feel it much. But the lag before the gas engine really kicks in (which gives you the real oomph up the onramp) is noticable, and I've been tailgated after not accelerating fast enough up the ramp. Theories included the change in direction of one of the MGs and the time to rev and fire the gas engine--never settled before it got ugly...
     
  16. brick

    brick Active Member

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    I guess the only answer to the lag thing is "don't do that." Maybe not the ideal answer, but smooth transitions are the best practice in any vehicle. It could be that I'm not bothered by this since I came from a manual transmission, and whatever HSD is doing in a "power NOW" scenario can't take any longer than double-clutching to rev-match a couple gears down in the rare instance that it was necessary. (Alas, that was fun.)

    The only thing I've noticed is that the Prius seems to go into a different mode immediately after a burst of hard acceleration. I needed to step on it today and for several minutes after it refused to shut the engine down, as if it was trying to be ready for my next aggressive move. No warp stealth, no glide for at least four miles. There could be something going on in the ECU that tries to complement the driving style, rewarding conservative driving with an efficient profile and aggressive driving with a more responsive profile.

    With respect to the original topic, Hobbit finally finished a writeup describing his observations of HSD behavior at steady-state. He, too, mentioned something about particular conditions where MG1 kept transitioning back and forth. I wonder we could use that data to reproduce the behavior that started this thread? Here's the page if anyone is up for some fairly technical reading:

    http://techno-fandom.org/~hobbit/cars/heat...results-03.html
     
  17. galaxee

    galaxee mostly benevolent

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    how long ago did you buy it? go back and insist they let you drive another car or they buy yours back.
     
  18. slvr_phoenix

    slvr_phoenix Tinker Gnome

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    My two cents on my experiences in my plain-Jane '06:

    * I have never noticed a surge while maintaining a speed on level ground.

    * I have noticed a surge while cruise control is on and I'm going up a hill. (Which is a 'duh' because obviously you need more power to maintain the same speed. But I just thought I'd throw that in.)

    * I have never had a delay in acceleration while already in motion. (Changing lanes, passing idiots, etc. is always safe and easy.) I've many a time gone even from deceleration to a rapid acceleration without a flinch. (The joys of congested interstate driving.)

    * I have had many a stutter in acceleration from a complete stop, as if the computer can't decide if I really mean it that I want to floor it and juggles through a couple of profiles over a second or two until it finally gets it right.

    So when push comes to shove, know what your car can do, know what it can't do, and don't drive like an arse if you know your car can't (or even may just occasionally hesitate to) do what you want it to. Drive safe. Know your car. Drive within its abilities.

    For example, I never peel out from a stop sign to nearly cut off oncoming traffic because I know my Prius will occasionally stutter through the first two seconds of acceleration from a stop and I'd really love to not be rear-ended just because I'm feeling impatient and my car decides to act goofy.
     
  19. KTPhil

    KTPhil Active Member

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    My hesitation lag is repeatable, and happens when approaching a tight turn and ensuing steep on-ramp at low speed (maybe 20 mph). The conditions to create the lag are:
    - coasting at a low enough speed and state of charge that the ICE shuts down for a few seconds (so the ICE is at rest).
    - stomping the pedal after making the turn when on the steep ramp.

    I think the cause is that it spends a second or so in pure electric mode until the ICE is started and spun up to an rpm that allows it to contribute a significant amount of power. While the electric motor has high torque from zero speed, once underway it contributes less and less as speeds are increased. The ICE produces more and more power as rpms increase (up to redline).

    I think this lag situation is happening because this road condition is asking for high power at a speed that is too high for the motor, and too low/soon for the stopped ICE.

    Mid-speed electric-only acceleration is not neck-snapping! Remember, for those with an EV switch, asking for too much power kicks you out of EV mode, and this is why.

    I have been able to eliminate the lag by selecting B-range when coasting as I approach the ramp. This means the ICE is already spinning when I floor it, so it doesn't have to be restarted and then spun up before producing power.

    In those conditions (being tailgated while coasting but soon needing a burst of acceleration), I use B until I am accelerating. As suggested above, I take this just as part of the performance personality of the car and it has become habit.
     
  20. harshfie

    harshfie Junior Member

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    <div class='quotetop'>QUOTE(efusco @ Jan 31 2007, 12:13 PM) [snapback]383330[/snapback]</div>

    "B" is wonderful if you live on a mountain like I do. I slip it into "B" on the way down and it holds very near 25 mph until I get to the bottom. You are right about "B" for flat roads, though...