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Toyota Prius

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  • john1701ajohn1701a Posts: 1,897
    Back in 1999, a few of the Pre-Classic models were shipped over to the United States for evaluation. Toyota changed quite a bit as a result, a whole collection of tweaks in addition to improvement in the hybrid system itself (engine, motors, and battery-pack).

    Anywho, the public in general wasn't involved with any of that, just selected tester families and automotive experts. The intentions were to make it as acceptable as possible for "joe consumer". So things like "should the gear-selector be mechanical or by-wire" had to be considered and "how detailed should the information on the Multi-Display be" are what had to be considered. And now, it's little things like that they are re-evaluating again.

    HSD is well established. Prius broke that ground back in 1997 when sales began, and it has provided the real-word data ever since. Estima (only available in Japan) jumped in 1.5 years ago to provide real-word data about hybrid implementation for 4-wheel drive. So all the system aspects are totally covered.

    What remains now is the interface research. What do SUV owners expect from a hybrid? What do LUXURY owners expect from a hybrid? What do owners that want all the technology hidden expect from a hybrid?

    It basically is just plain old marketing stuff to deal with now.

    JOHN
  • dc8527dc8527 Posts: 12
    "nippononly wrote: "...seem to be getting about 46 mpg - 400 miles so far. What are owners averaging in regular round-town driving?"

    My first 1,200 miles in Minnesota in the past month averaged about 40MPG. The drive between my home and work is similar to EPA's test conditions with 2 exceptions, 5.5 miles, about half of EPA's distance and low temperature, mostly around mid teens above zero F. I got only 33MPG this morning. The temperature was about 20F.

    Toyota said its engineers were investigating into the low MPG concern from the cold climate. The answer would be due by mid Jan. It is about time to call them again.
  • nippononlynippononly SF Bay AreaPosts: 12,687
    I am in California, a lot warmer here, so my mpg is bound to be a bit better than Minnesota! Also, I am judging by gas put in, not the computer, which I figure may be inaccurate - it bounces from 13.2 to 99.9 on a regular basis! :-P

    What's with the gas gauge, BTW? I have stopped for gas twice (after 200 miles each time), because the gauge is down near 'E'

    Does anyone do what I have already done twice - reach for the gear shift in the dark and flick on the wipers by mistake?

    So no-one has thought of changing out their tires for bigger ones yet? The OEM in my case are Goodyear Integritys - not the greatest type either.

    2013 Civic SI, 2009 Outback Sport 5-spd (stick)

  • ...well, I did a test this morning in my Prius while driving to work. Temperature outside was about 49F. I had the "Auto A/C" off as well as fans/blower in off position. The lurching continued as usual. So, fromt this non-scientific test, I would say that the lurching is not due to having the heater or fans on etc...it must have something to do with what John had posted earlier...hot coolant pumping through the engine warming it up etc...
  • I've been doing some research on cold weather fuel mileage and here is what I found. This following article can be found at http://www.startribune.com/stories/435/3799559.html
    <Start of Article>
    When it's colder, engines use more fuel because they're running richer, meaning a lower air-fuel ratio (higher percentage of fuel to air). When engines are cold, a percentage of the vaporized fuel condenses into liquid form on the cold metal parts of the induction system, such as the intake manifold runners, intake valves, pistons and cylinder walls. The colder the engine at start-up, the higher the percentage of fuel that condenses on these parts.
    This condensed, liquid fuel cannot burn. Only fuel in gaseous form can be ignited, so on cold starts the fuel injection system must deliver a richer mixture so that enough fuel in vapor form reaches the combustion chamber, where the spark plug can ignite and burn it.
    As the engine warms up, less fuel condenses as internal parts warm up, so the fuelair mixture can be leaned out progressively. But of course, during the several-minute warmup period, the mixture will be richer than normal. And in the three-mile drive, it may well remain somewhat rich the entire time. In 0 degree weather, it probably would take more than a short warmup period and three-mile drive for the engine, coolant and oil to reach full operating temperature, and fuel-air mixtures to reach optimal levels. <End Of Article> This explains why the Prius has a thermos behind the left front headlight that can keep the coolant warm for up the three days. So why still the bad MPG? Well, if you go to http://www.swri.edu/10light/mile.htm
    they say that cold air is denser, so more fuel is burnt in the ICE, this denser air also offers more air resistance, and the denser air in the tires reduces tire pressure. So all of this explains why all cars get less MPG in cold weather. However, this still does not explain the extraordinary poor MPG performance of hybrids in cold weather. I've lived and driven where it is cold and snows and never really noticed a big hit in MPG when it is cold with a pure ICE. I always checked my mileage after fill ups so I would have noticed. So why the acute affect with hybrids? Well, if you go to http://chemistry.about.com/library/weekly/blbattery.htm
    someone with a Ph.D. in chemistry explains that if a battery is used at a low temperature then less current is produced than at a high temperature because the chemical reactions inside the battery slow down. Since power(watts) = volts multiplied by current, if you have less current, then you will have less battery power. Therefore, the gas engine will have to work harder and MPG takes a dive. This is why on the HCH there is a vent behind the back seat to allow warm cabin air to flow on top of the battery pack. However, there is no fan to blow this warm air down over the battery pack and so it stays cold. This explains why HCH drivers also report poor cold weather MPG. Perhaps someone who lives somewhere cold could perform an experiment by somehow rigging up a contraption that will keep the battery warm and then drive it on a known route to see if it makes a difference. If we can solve this problem the data can be sent to both Toyota and Honda so that they can develop their own battery temperature management systems. If successful, perhaps some kind of after market device could come out of it for existing hybrids?
  • john1701ajohn1701a Posts: 1,897
    > battery is used at a low temperature then less current
    > is produced than at a high temperature because the
    > chemical reactions inside the battery slow down.

    The sweet part of the Toyota design (not sure about Honda) is that it bumps up the voltage to 500 via an invertor. So even if you aren't able to draw as much from the pack due to the cold, you'd never notice. Power will remain the same, regardless of temperature. Overall capacity will be lower though. Fortunately, the pack is big enough to compensate for that.

    JOHN
  • > it bumps up the voltage to 500

    But what if it is so cold that it has to go above 500 volts to maintain the required power? 500 is the max. A better system would have been to keep the battery warm. Then there would be no decrease in power or capacity.
  • > it bumps up the voltage to 500 via an invertor. So even if
    > you aren't able to draw as much from the pack due to the
    > cold, you'd never notice. Power will remain the same,
    > regardless of temperature.

    The given power(watts) that a battery pack can deliver at a given temperature is fixed. Since power(watts) equals voltage multiplied by current, then if power(watts) is fixed and volts goes up, then current must go down. This is the law of conservation of energy. You cannot get something (more power) from nothing. If you could, then you could multiply your voltage with an inverter to a billion, billion volts and power the entire world! I don't think so. The Prius has an inverter because the battery pack puts out DC current and the motor is AC.
  • Did you get rid of the Matrix for the Prius?
  • nippononlynippononly SF Bay AreaPosts: 12,687
    this is a rental that is due to go back soon.

    But the Matrix may go soon, possibly to be replaced by something other than a Toyota for the first time in seven years.

    This new Prius is really neat in many ways, but I have decided it isn't really my thing - not in the market for a Camry-type vehicle. But I was curious to see all the improvements over the "classic" Prius, since I accidentally rented one.

    2013 Civic SI, 2009 Outback Sport 5-spd (stick)

  • john1701ajohn1701a Posts: 1,897
    > Law of conservation of energy

    Yup, energy isn't free. But that the system has been proven to run perfectly fine with a damaged non-functional module. The loss of wattage makes no difference to operation, only efficiency.

    And sorry, I don't have numbers available for that. The only detail I've seen was for the amps in warm verses cold measurements. The amp draw was allowed to be much higher in the colder, likely due to not having to worry about cooling needs.

    > The Prius has an inverter because the battery pack puts
    > out DC current and the motor is AC.

    It also increases the voltage, since the pack itself is only 201.6 volts.

    > A better system would have been to keep the battery warm.

    Yup to that too; however, electricity comes primarily from the engine anyway. So it isn't really as bad as it could be.

    JOHN
  • quasar4quasar4 Posts: 110
    Has anyone noticed a creaking/rattle/buzzing noise at any time when driving? I usually notice it when I'm going slow and accelerating. It lasts for about 3 seconds. It's not the same sound as the motor makes when you shut off the power.

    Also curious about the daytime running headlights. The owner's manual says that they'll engage when the parking brake is disengaged --even with the headlight switch in the OFF position. Doesn't seem to work for me (I have a package 7).

    Oh, and concerning the cold weather low mileage discussion, one other factor could be oxygenated gasoline which I believe is mandated in certain areas of the country during the Winter months to reduce air pollution. The gas mileage of my old Honda would always drop after filling up with the modified fuel.

    Thanks
  • > the system has been proven to run perfectly
    > fine with a damaged non-functional module.
    > The loss of wattage makes no difference to
    > operation, only efficiency.

    This is true. Whether the loss of wattage is from a damaged module or cold battery pack, the system will compensate and still operate. The only thing is efficiency will go down which means less MPG.

    > electricity comes primarily from the engine
    > anyway. So it isn't really as bad as it could
    > be.

    Perhaps it isn't really as bad as it could be in steady speed highway driving, but the battery pack is needed to store recaptured electricity from regenerative braking. So if the battery pack efficiency goes down then so does MPG in city driving.

    I am just trying to help people understand why cold weather makes MPG go down. All in all, the Prius is still a wonderfully engineered car that overall excells in MPG. Hybrid technology is still in it's infancy and eventually all of it's quirks, problems and whatever will be worked out. Until then there will still be plenty of people lining up to buy them. Probably more than supply can meet. I even bought one! And I love it because this is cutting edge personal transportation technology long overdue and to be part it is an experience in it's own! It is also a gratifying experience to know you are doing the right thing for the environment and the future.
  • john1701ajohn1701a Posts: 1,897
    > I am just trying to help people understand why cold weather
    > makes MPG go down.

    No problem... except the most important fact hasn't been pointed out yet. The battery-pack only takes a few minutes to warm up anyway. Using it creates heat. So the cold is rapidly eliminated.

    It's like the recharging. That only takes a few minutes too. The common misconception is that it takes much longer.

    JOHN
  • "Has anyone noticed a creaking/rattle/buzzing noise at any time when driving? I usually notice it when I'm going slow and accelerating. It lasts for about 3 seconds. It's not the same sound as the motor makes when you shut off the power."

    Yes I have. I have no idea what it is but assumed it was just the normal vehicle operations taking place. I am curious though!!? I think it seems to be coming from the engine compartment near the speedometer area.
  • DRL's are not available on U S cars, only on those shipped to Canada.
  • umpireumpire Posts: 12
    I am in the market for a new vehicle, an I sat in a Prius yesterday. It looks like a good car, but I'd like your opinions of this vehicle on the questions below and any other topics you can think of.

    I appreciate your help!

      
    Do you really get 55 mpg?

    How is the ride/handling?

    Does it seat 5 comfortably (I really need this)?

    Have you experienced mechanical problems? If so, what?

    Does the build quality seem adequate?

    Do you think it will hold up over 100,000 miles?
  • wwestwwest Posts: 10,706
    The boost to 500 volts is there because of the above. The inductance, copper windings, in the electric motor are highly resistant to current flow, much more so tha a simple resistor of equal resistance. Applying a higher voltage initially, only until the current flow rises to a more desireable, design, level, improves the efficiency of the electric motor drive system dramatically.

    Assuming some method is provided to "artificially" limit the current flow, applying more voltage, even a BILLION volts, would result in a quicker generation of torque in an electric motor.
  • > Does it seat 5 comfortably (I really need this)?

    Try sitting in the back seat and see if you have enough head room. The sloping hatchback design takes a little away from this. Otherwise it has lots of room.
  • >Do you really get 55 mpg?

    I'm in the St. Louis area with aprx. 1600 miles on my vehicle. I commute 33 miles each way primarily on Interstate with some rush hour stop and go. I'm currently averaging between 46-49MPG.

    >How is the ride/handling?

    The ride is one of the smoothest of any vehicle I've personally owned. Handling has been great. Obviously this is just my opinion. I've had a close call with an inattentive lane changer and the rear tire of a vehicle I was passing, when it fell off, and the vehicle remained stable in both situations while I swerved all over creation.

    >Does it seat 5 comfortably (I really need this)?

    I'm not sure of the size of the 5 people but the backseat legroom is greater than any vehicle I've been in. I'm 6'3" / 260LBs. and the vehicle is comfortable to me. I had a backseat passenger the other day, 4 adult men, who is 6'3" or so and 300LBs. and I heard no complaints from anyone. Just "look how big that backseat area is."

    >Have you experienced mechanical problems? If so, what?

    None. I did have a minor issue that has been reported by several people where I got a check engine light after about 40 miles that stayed on for about 60 miles. This has been reportedly due to an oil protective coating on the exhaust system that "burns" off during highway driving. No noticeable change in the vehicle operation during the "check engine" phase. I believe it is said to be related to a sensor being obscured until the coating burns away.

    >Does the build quality seem adequate?

    Build quality is superior in my opinion. Toyota is one of the only vehicle makers that has consistently rated above Subaru (we've had 5) in reliability and quality. This is my first Toyota and I'm extremely impressed. The Prius specifically is built very tight and you can even get a sense of the solid construction by just closing the door.

    >Do you think it will hold up over 100,000 miles?

    Considering my Subaru vehicles held up over 100,000 and this vehicle is reportedly, and apparently, better quality I would say yes.

    Hope this info helps in your decision.
  • > The battery-pack only takes a few minutes to
    > warm up anyway. Using it creates heat. So the
    > cold is rapidly eliminated.

    Any proof that the battery pack only takes a few minutes to warm up? Does your's have a temperature sensor in it? I know that batteries create their own heat during use. But if it is severely cold, since hybrids do not use the battery pack constantly, I really wonder about this. Many people complaining about poor MPG in the cold are reporting that they are driving mainly in the city with lots of stops. Reduced battery efficiency would account for this since the battery pack is used most here to recapture energy during braking and help in acceleration. But with steady speed highway driving it's mostly energy from the gas engine so the MPG drop there is not as bad. Maybe someday we'll here what Toyota has to say about cold weather performance. Click on this link to learn more about Why Do Batteries Discharge More Quickly in Cold Weather and what they say can be done about it: http://chemistry.about.com/library/weekly/blbattery.htm
  • > applying more voltage, even a BILLION volts,
    > would result in a quicker generation of torque
    > in an electric motor.

    Yes, you are right. But we were talking specifically about cold weather performance. I really don't think Toyota designed the car to ONLY provide a quicker generation of torque in cold weather. Why not do it when it's warm weather too? The inverter bumps the voltage up to 500 volts from lower battery voltage because it was designed as a 500 volt system for the reasons you mentioned and not just during or for cold weather.
  • geogirlgeogirl Posts: 24
    Umpire,
    I got my new Prius on Dec. 24 so I have limited experience driving the car, but I LOVE this car! The ride is smooth and comfortable. On my first tank of gas I averaged 44 mpg (temperature was in the 20's and for a few days only in the single digits). I'm on the second tank now and weather has warmed to 40's up to 60(daytime)with mornings in the 30's and my mileage so far for the last 250 miles is at 50 mpg. As far as room, very roomy in the back seat - my husband 6'2" fits easily. However, if you are over 6' you should try this for yourself as some have reported head room problems. Also if you need to fit 5 adults routinely, you need to be looking at larger cars! This car is the typical mid-size car where it can seat 4 comfortably, but anyone other than a child in the middle rear seat - good luck! As far as mechanical problems - none; build quality - very solid; and I bought mine with the idea that I would have it for more than 100,000 miles. Considering that the battery is warranted for that long, I think Toyota thinks so too. Just want to add - this car is fun to drive. I have no regrets. Good luck with your decision.
  • Does the 2004 really have the warning? Recently I had a screw in a front tire and the pressure got down to 11 pounds and nothing happened.
  • hans000hans000 Posts: 19
    Don't seem to have that. I didn't see it mentioned in manual. (That's not much though: the horn is not mentioned. The worst part of this car, IMHO, is the manual.)
  • hans000hans000 Posts: 19
    No kidding. I can trigger the lurching by just raising cabin temperature even after it's reached previous set point (75F). It comes and goes together with the blower speeding up/down.

    During cold (50F, N. CA) start and the car stopped, it feels like ICE is still running but the display shows not. I am curious what's causing that vibration, ICE or AC compressor?

    I doubt it's the coolant pump. On conventional car(should be the same on Prius) the pump is similar to a blower: it doesn't vibrate. The vibration/lurching is the signature of piston/cylinder thing.

    ===============
    texassalsa04 wrote:
    ...well, I did a test this morning in my Prius while driving to work. Temperature outside was about 49F. I had the "Auto A/C" off as well as fans/blower in off position. The lurching continued as usual. So, fromt this non-scientific test, I would say that the lurching is not due to having the heater or fans on etc...it must have something to do with what John had posted earlier...hot coolant pumping through the engine warming it up etc...
  • dc8527dc8527 Posts: 12
    Thanks hybriddriver for the extensive analysis on low MPG in the cold! We need to face an issue, dig into it and try to come up with solutions. I called Toyota today. It has not published any solution.

    There are 8 bars in the battery gauge. When it drops 2 or more the color changes from green to blue. It is blue most of the time on my 04 Prius. How about yours and others' from warm and cold climates?

    I believe the computer instructs the gas engine and the electric motor to charge the batteries more often when they are in blue, hence more gas consumption in this regard.

    Does anyone know how the battery gauge work? Measuring the voltage drop is the easiest, but may not be the best estimate of how many charges are left in the pack. Measuring the internal resistance of the pack may be another way, yet it still is not a direct measure of the charges left.
  • oldfoxoldfox Posts: 29
    Maybe somone who knows more than I about the Atkins cycle engine can answer my question.

    Why does a 2cy engine only get 7 mpg? I see this all the time on my screen - not just 7 mpg but 13 -23-10 etc. Seems to me a 2cy should get much better even from a dead stop and even not using the battery (Yes, I know the battery starts the car but hope you understand the question)
  • umpireumpire Posts: 12
    geogirl and talleyid,

    Thanks for the responses. They have me ready to order one today!

    One other question I need answered. I tend to drive faster than the speed limit.

    How does the Prius perform at speeds of 75 and higher?
  • Are my batteries in the blue most of the time? Well, guess what, I have the other hybrid. The Honda Civic. So unfortunately, I cann't answer that question. I live in Northern California where it is usually warm so I don't even have severe cold data. But I am glad that you appreciated the info I posted.
    :)
    Half of a solution to a problem is to first identify exactly what is wrong. In this case the problem is cold battery pack in severe cold weather greatly diminishing city MPG. It is now up to Toyota to implement a fix or if that is not possible, redesign it for future models.
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