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What to expect from the next model year Prius



  • wwestwwest Posts: 10,706
    I'm glad to see that someone understands the e-CVT even better, moreso, than I do. But wouldn't changing the e-CVT's planetary gearset ratio allow for MG1 to remain in "control" of a higher HP ICE?

    Not that such a thing is really in the realm of feasibility....
  • Dramades: By 2009, gasoline will be $5.00 per gallon if this admistration keeps threatening to bomb more countries.
    I went to the trouble of flying to Virginia from Florida to buy my Silver car with package #6 a week ago. Very glad I did. Think of how much you would save in gas costs, insurance and repairs versus waiting for the 2009 Prius.
    I say buy now while they're available. Evro in Tampa. :confuse:
  • toyolla2toyolla2 Posts: 158
    wwest I understand you're suggesting we increase the HSD ratio to avoid having the more powerful ICE overwhelm MG1 ?
    The general HSD eqn of MG1 = ICE x 3.6 - MG2 x 2.6 ------- eqn #1
    is to become, let's say, MG1 = ICE x 4.6 - MG2 x 3.6 ------- eqn #2 for the higher torque ICE.

    At the present ICE rpm and MG2 rpm are 3644rpm and 1200rpm respectively passing through 20mph while accelerating.

    If we wish to keep the ICE at 3644rpm, since lowering it would be defeatist, then substituting into Eqn #2 MG1 will have to move up from its current max of 10,000rpm to 12,442rpm.
    An almost 25% rise that we know from Hybrid Camry is possible. It will have the effect of raising MG1 electrical output from 42.2Hp to 52.5Hp. The copper loss at 100 amp would remain unchanged. There will however be an increase in the iron loss at the higher excitation frequency but this may have marginal effect since these revs are only maintained during full acceleration ramps that last a few seconds.The voltage on the system will also rise thus impacting the semiconductor specifications for the inverter.
    MG2 will be required to handle 52.5 +28 Hp or 80.5Hp instead of 67Hp and the machine loading above 51mph remains quite high because of the battery assist.

    It's a long answer. As you would expect the gear ratios must be chosen to keep the rotating components within reasonable spin rates. As a result any increases in power input would be more propitiously handled by increasing the torque capacity of all the components involved.
    One of the problems with HSD is the ring gear and the components connected to it. Rotating this assembly beyond 6000rpm raises a serious balance issue. It represents the output shaft of the whole system and this rpm at 100mph is fine for a planetary connected to a 4 cyl engine, later on however it may turn out to be too slow for the higher speed small engines in the pipeline. Secondly MG2 needs to be turning much faster at this speed. A 16,000rpm limit at 100mph would more than double the existing power density of MG2 if it was allowed its own 10:1 reducer at the wheel axle.
  • wwestwwest Posts: 10,706
    " A 16,000rpm limit at 100mph...."

    And just who would object if the Prius' top speed were limited to ~80 MPH..??

    Will the current model even do 100 mph except downhill?
  • larsblarsb Posts: 8,204
    wwest says, "Will the current model even do 100 mph except downhill?


    By Gary Richards
    Mercury News
    Article Launched: 08/21/2007 01:39:13 AM PDT

    All right Al Gore III, you're still the tops when it comes to speeding in a Prius - but not by much. Steve Wozniak is right behind you.

    And when I say speeding, man o' man, do I mean speeding.

    You probably remember when the son of the former vice president was caught going 105 mph in Southern California last month. Well, a mention of that in a recent Roadshow column led a buddy of Wozniak's to check in, claiming that the co-founder of Apple Computer was ticketed for going 105 mph on Interstate 5 earlier this year.

    Whoa. Mr. Roadshow knows a good story when it plops into his lap. If true.

    "Not true," Wozniak replied: "104 mph."

    OK, squash that image of the Prius being wimpy, as Gov. Arnold Schwarzenegger had quipped this year. First, 105 mph, and then 104!

    "I pleaded guilty, with an explanation," Wozniak said in one of several e-mails exchanged the past few days. "I said that I was really scientific, and in the last year had been in Athens, Moscow, Berlin, Frankfurt, Munich (twice), Zurich, Canada (three times), Columbia, Singapore, Japan, London, etc., and had gotten used to kilometer speeds."

    The judge smiled. But he didn't buy it. The fine was about $700.

    Wozniak was headed to Las Vegas for a business trip with his pal Dan Sokol on March 28. Little head wind, light traffic, a straight road. His Prius was sailing along so smoothly that neither realized the speed Wozniak was reaching.

    Woz and Gore Jr. both clocked over 100
  • toyolla2toyolla2 Posts: 158
    Landspeed Prius Hits 130.794 mph at Bonneville
    On 23rd December 2004 a modified Toyota Prius reached 130.794 mph on the three-mile short course at the Bonneville Salt Flats.
    An engineering group from Toyota and Toyota Motorsports worked on the Prius for more than two months to prepare the vehicle.
    The Landspeed Prius ran a stock Hybrid Synergy Drive powertrain. The transmission final drive gear ratio for the gas engine was modified from the stock 4.113:1 to 3.2, while the inverter voltage was increased to 550 from 500 volts. The engine redline was also changed for optimum performance.
    A transmission cooling system was added to the front passenger area to decrease the temperature of the inverter and electric motors. Regular ice was constantly added to the system to prevent overheating. Ambient temperature on the salt flats was nearly 100 degrees with nearly 100 degrees humidity.

    Thanks to greencarscongress for the above, although this probably showed here on Edmunds News and Views at the time, it was likely archived somewhere.

    That aside, I have read that under ideal conditions Prius will cruise at 100mph with 49Hp so it would not be too severely taxed since the 1NZ-FXE engine produces 76Hp @ 5000rpm. As most know by now this engine has an almost flat torque curve with respect to speed, so this would correlate to an engine speed somewhere north of 3330 rpm. Bottom line At 100 mph Prius could cruise all day.
    On the otherhand, I would not object to an 80mph Prius, unfortunately the tradeoff of adding something to the bottom end would not be that great since we are dealing with the HSD which is mostly a constant power system.

    I should mention that here in the great white north they just added a new law. Go more than 30mph above posted limit and they impound the car, suspend your licence and impose fines between $2000-$10,000. The ink for this new law hardly dry but they've already caught (actually "surprised" would be a more accurate verb here !) over one thousand drivers.
  • wwestwwest Posts: 10,706

    The bottom end torque could be limited just as easily as top speed, not that TC wouldn't already, but only after the "fact". Perhaps a "snow" mode..??
  • wwestwwest Posts: 10,706

    I hope, like to think, they added some downforce "effects" and wider tread tires for that high speed run.
  • That's 90 miles per Imperial gallon, somewhat better than 2004-2008. The batteries will remain Lead/Acid not Li-on as originally planned.
  • gagricegagrice San DiegoPosts: 31,109
    Could this be true? Using Lead Acid instead of NiMH batteries as in the current Prius?

    This is set to be powered by a 1.6-litre turbo engine, mated to a more efficient hybrid system. Previously, Toyota has hinted it would use lithium-ion batteries to create a vehicle capable of returning up to 100mpg.
    However, technical challenges in the development of the new cells has forced bosses to abandon this plan, and instead it will use less advanced lead acid cells.
  • kdhspyderkdhspyder Posts: 7,160
    No that's a typo.. The current and the next Gen will still have NiMH batteries. I'd expect the new Prius to achieve about 55 -60 mpg Combined under the new 2008 regulations. That's a 20% increase in Average FE.
  • pathstar1pathstar1 Posts: 1,015
    I'd say that's an indicator of the accuracy of the "news item". Yet more speculation from a bogus auto mag trying to sell copies.
  • wwestwwest Posts: 10,706
    "..1.6-litre turbo engine..."


    There is just barely enough HEAT level left in the exhaust of an atkinson engine to fire off the catalyst to operating temperature. Certainly NOT enough to "power" a turbo.

    On the other hand a fully variable speed/boost Supercharger might be an ideal way to increase the power of a 1.6L engine up to the level "required". Adding another variable frequency inverter to power a 2-3 HP AC motor to drive the SC would be a POC. Even better, driving the SC via a combination of the ICE and an AC motor via a form of the e-CVT would be even better.
  • toyolla2toyolla2 Posts: 158
    We all know that Toyota, as with other auto companies, is on this track of more power with succeeding models whether the consumer needs it or not. With the Prius the most obvious upgrade is to let the 1NZ-FXE engine run at 6000rpm which should up the power from 76Hp to something around 90Hp with only incremental increases in the electrical equipment. Of course the engine may not be quite so clean at this level but does the DOT testing actually require the engine to touch maximum output over its standard driving cycle, does anybody know ?
    I have brought this up before that the amount of time that full power is ever used is comparitively small, perhaps the standard should be that when cruising at top speed. But could you even fail a vehicle on its pollution count at 100mph since that condition is beyond posted limits permitted in any state ?
  • wwestwwest Posts: 10,706
    That's exactly the argument I often used against the K&N filter, operating at WOT and near top RPM is so rare that the clear majority of the time the throttle valve is the MAJOR restriction to airflow.
  • toyolla2toyolla2 Posts: 158
    wwest, I agree with what you say but it doesn't answer my questions re CO2 counts etc.

    However talking of engine use at max rpms, that is the reason I favor series hybrids. With control of the throttle most drivers will not rev above 4000rpm, so they have this large engine but they never use but two thirds its capacity.
    With Prius and series hybrids you relinquish that control to the ECU. In return you get, with the Prius, a performance boost not found with stepped transmissions as the engine continuously rises towards its full rpm at 51mph.
    Instead of capitalising further on this advantage, the industry appears to be looking to use more power to be sourced from batteries. Fom a recent announcement we learn Toyota is supplying two Prius to SoCal universities equipped with larger NiMH packs. I see that as a niche market with the cost of the battery raising the hybrid premium.

    Alternatively, I would like to see the Fiat 900cc two-cylinder engine style, from the Panda Aria concept that's scheduled for 2010 I believe, installed in the next design of Prius. It has 25% less weight and 20% more FE over the small four usually fitted to that Fiat vehicle. Fiat is working on a 65Hp naturally aspirated version but the turbocharged 105Hp is good to go. I can only guess that the higher CR used on the lesser engine is giving a NOX issue.

    Fewer cylinders would provide a needed cost reduction on the Prius. I would quite believe that the machining operations are similar in inline fours such that the price delta between 1.5L and 2.4L engines is quite small. It is going to need something like less cylinders to make a difference.

    They used to say about small engines 'a different hill needed a different gear'. The Prius servos with their ability to supply the exact ratio needed for the load torque at any point in time would seem ideally suited to these two-cylinder engines.
  • chadxchadx Posts: 153
    "I went to the trouble of flying to Virginia from Florida to buy my Silver car with package #6 a week ago."

    I hope you bought carbon offset credits for the flight. ha! ;)

    Just kidding, of course, but that joke works on so many levels, I couldn't resist!
  • pathstar1pathstar1 Posts: 1,015
    The double battery pack used in the test vehicles both in Japan and at the universities in the US are to simulate the new LiION pack in a plug-in system. The LiION pack is reputed to be a 12 -14 AHr pack, so two of the NiMH 6.5 AHr packs had to be used to give similar range. Nothing to do with extending the power from battery but rather extending the EV only range. We don't know if or how Toyota limited current flow from the double pack. Current flow limiting in the current Prius is why it will start the ICE if you accelerate very much. In that case, the limiting was put in to protect the battery to ensure long life.

    The test vehicles are here to evaluate the usefulness of the extended range on EV only, to see if it is really worth the extra cost, in an urban setting. They are also evaluating the use of the plug-in feature, to see how that translates to reduced emissions, again, in a US urban setting, and the Japanese ones in their urban setting. It's hard for the engineers to know exactly how such a vehicle would be used, as that is different in different cultures, so these tests are to gather data on that.
  • stevedebistevedebi LAPosts: 4,098
    "However talking of engine use at max rpms, that is the reason I favor series hybrids. With control of the throttle most drivers will not rev above 4000rpm, so they have this large engine but they never use but two thirds its capacity. "

    If it were possible to build a commercially-viable series hybrid, I think Toyota would already have done it. I hear lots of hype about series hybrids, but have yet to see an actual implementation, except for (I think) diesel train engines.

    Do you have any links to post for anyone who has ever produced such a auto comercially?
  • toyolla2toyolla2 Posts: 158
    Hi Steve, this link is about series hybrid delivery vans supplied to Purolator (Canada Post)

    Azure were working a deal in the UK with London Taxis International to supply them with a series hybrid cab. At least one was built and shipped from their plant in Vancouver, BC. Later on LTI introduced their new "Black Cab" for London's downtown. Said vehicle turned out to be a 2.2L diesel with automatic transmission. That's right, someone gave the greenlight to mixing thousands of diesel engines in one of the most populated areas in England, go figure.

    This particular action seemed hardly consistent with government policy to reduce air pollution in urban settings. A while later Azure closed their UK office.
    Azure Dynamics is a division of Ballard Power Systems. Last week Ballard announced the sale of its automotive fuel cell division.

    In the meantime it must have been somewhat embarrasing for Azure to learn that the highest mileage hybrid was in fact a Vancouver taxi in the form of a Toyota Prius, which had been running around in their own backyard.

  • toyolla2toyolla2 Posts: 158
    Always a good idea to get preliminary feedback. I hear SoCal has idyllic weather despite the occasional grass fire. This would be a perfect time of the year to start putting these vehicles into the snowbelt as well for a more robust test. Pathstar1, it would be interesting to see whether they are up for that. Anyone who leaves a vehicle overnight in temperatures of -10deg C without a battery warmer and a well insulated battery box is going to be disappointed I can tell them right now. And for that my bill will follow shortly. :)
    Regarding power limitation, you are probably aware the Prius - with software changes - could reach 60 mph using the nominal 21kw without actually overspeeding MG1 but is seven miles of this continuous type of operation going to be tolerable to the PSD ? Else it will be interesting to see how many opportunities there are to drive below 42mph for the extended range.
  • pathstar1pathstar1 Posts: 1,015
    Unfortunately, if you do try that (using battery only to accelerate to 60 MPH) you will draw too much current from the battery. This will drastically shorten the battery life, due to overtemp and just from the high current even if you could control the temp. Remember, it's only a 6.5 AHr NiMH battery. If Toyota designed one with two packs in series, so 416 V nominal instead of 208 V nominal, perhaps the current would be low enough to be safe. This is what other prototype vehicles have been doing. You can see this design need if you look at the new GM SUV (Tahoe/Yukon) hybrids. They use a 500+V battery, as they are much heavier than the Prius so need a lot more power (read current with the same voltage). So they had to raise the voltage to keep the current reasonable.

    As for low temps, I don't think -10 C would be too bad. I've not seen any problems with the "traction battery" so far, but I've also only seen -5C (this will be Pearl's first winter). Once you start using the battery it quickly warms up, and it only has to start the ICE at first.Others with more winter experience have not had problems with the "traction battery", it's been the 12V one that has failed them. We shall see.

    Now once the temp gets down below -40C (or F - they are about the same) then it gets interesting. THAT is when we start having battery problems with lead acid ones. At least the NiMH battery won't freeze at those temps.! It takes a lot of current to turn over an engine when the oil is that cold. It kind of tends to become molasses. ;) I'm referring to the oil in the HSD, as the engine oil can be 5W30 synthetic (what I'm using) and it flows pretty well, even at -40.

    Yuck, thanks for reminding me what I'm going to experience in the next few months! ;)
  • toyolla2toyolla2 Posts: 158
    "Unfortunately, if you do try that (using battery only to accelerate to 60 MPH) you will draw too much current from the battery."

    I think it's documented and confirmed by scantool that MG2's controller will current limit to a battery bus draw of 100 Amps. The two packs should share this current since the volt drop in their internal impedances may force a current equalising effect, not perfect but close enough for new packs and in the short term. I don't want to debate whether this is a good idea for reliability going forwards, perhaps not. But right now this is a test about the human interface response to an extended driving range.

    MG2 will have benefit from the upconverter that normally transforms the 201v pack voltage towards 500v as the vehicle goes from 20mph to 50mph, of which you may have forgotten. So connecting packs in series is not an issue here. As the vehicle gains speed over this range the current will have to reduce inversely of course to observe the nominal 21kw limitation on battery power specified with the Gen II Prius (NHW-20). And I suppose it goes without saying that as long as 21kw exceeds the power needed to cruise, the vehicle will continue to accelerate.

    You've not addressed my concern of MG1 approaching 10,000rpm as the vehicle nears 60mph which may setup an audible whine. This speed was promised earlier for the Li-ion pack which is why I bring it up.

    Have you seen these ?
    The following contain useful temperature / power graphs
    For CY1997-2000 NHW-10 Prius, 7.2V X 40 modules (cylindrical)

    For CY2000-2003 NHW-11 Prius, 7.2V X 38 modules (old prismatic)
    (They used to have a comparison page, but it was gone.)

    For CY2003-2005 NHW-20 Prius, 7.2V X 28 modules (new prismatic)

    For CY2005 HH/RX400h, 9.6V X 30 modules (metal prismatic)

  • toyolla2toyolla2 Posts: 158
    I'll try once more !

    For CY1997-2000 NHW-10 Prius, 7.2V X 40 modules (cylindrical)

    For CY2000-2003 NHW-11 Prius, 7.2V X 38 modules (old prismatic)
    (They used to have a comparison page, but it was gone.)

    For CY2003-2005 NHW-20 Prius, 7.2V X 28 modules (new prismatic)

    For CY2005 HH/RX400h, 9.6V X 30 modules (metal prismatic)
  • stevedebistevedebi LAPosts: 4,098
    "Hi Steve, this link is about series hybrid delivery vans supplied to Purolator (Canada Post)"

    Thanks, interesting link.

    I'm wondering if the cost is prohibitive vs. performance for the consumer market. Businesses can depreciate costs, so their equipment can be more expensive and still be economically viable.

    Also, delivery vans don't generally run long distances at high speeds; I wonder how that would work out with consumer vehicles...
  • sr1945sr1945 Posts: 38
    My thoughts on a new Prius soon......

    Need a hybrid, but the current Prius interior and dash layout are not to my liking for the money spent. Wish they had a more standard dash layout, than I would jump on it. Though some pictures are around of a possible new hybrid Prius in 09, none of which have a interior shot.

    Toyota, I hope will make the follow on Prius much better inside. Still like the exterior, but that to now needs a refresh.

    If anyone in the know, has some rumors about what the new Prius follow on interior looks like, please post a link. Thanks
  • lm2lm2 Posts: 2
    Those interested in what the 2009 Prius may look like, check the March issue of
    Motortrend. There is a drawing based on information or rumors from employees inside Toyota. The drawing shows a very sleek machine, although drawings are often exaggerated. Also mentions that the engine will be a 1.8 litre, and initially will use the current battery pack.
  • kdhspyderkdhspyder Posts: 7,160
    Yes I had heard that there was rumor of bumping the 1.5L up to the 1.8L and increasing the capability of the NiMH battery pack and motors. since the new HH has an ECON mode and an EV mode button I'd guess that the next Prius will as well. Pure speculation though.

    As a counterpoint, I love the dash on my current Prius I hope that keep that in some form or another.
  • toyolla2toyolla2 Posts: 158
    First, if we are going to speculate let's look at some numbers. To start with, I've never fully understood why the current Prius engine runs only to 5000rpm, whereas the 2.4L in the Camry Hybrid runs at the same speed as the engine in the non-Hybrid Camry which is 6000rpm. With that in mind I would expect that before upgrading engine capacity to 1.8L, from Im2's Motor Trend reference, that Toyota would be addressing this rpm issue with the original engine first. Sure I'm not expecting them to get the full 108Hp from the Echo's 1NZ-FE engine but 20% increase from the 76Hp Atkinsonised engines, that were installed starting with the 2004 Prius, would be welcome. The following is a rehash of my #104 post of three months ago. It was in answer to wwest regarding the suggestions of more horsepower via forced induction. This unfortunate 1.8L idea being also a step in this direction. Even though I don't own one yet my test drive of the Prius told me the car is powerful enough. And incidently that's from the vantage point of someone who happens to drive a Lexus. Clearly fuel economy will suffer with a 1.8L and the last time I looked the Prius is under no threat in the horsepower race.

    To continue with the simple expedient of merely increasing the engine rpm by 20% must needs the rest of the system to accomodate this. And inexpensively too I might add. The fact is you have to start with the MG2 system which will need upgrading 20% also, since at lower speeds the majority of the torque at the wheels comes from this machine - 259lbs-ft versus 59lbs-ft from the ICE. To do this the three stage reducer giving a 4.113 stepdown ratio needs to be stretched still further to 5.0. This will require MG2 to run at 7200rpm at 100mph and to do that will require the upconverter to supply a max of 650volts, up from the 500volts used previously. At the same time MG1 will need to reach 12000 rpm to generate this voltage also. All these things have been done with the Camry Hybrid by the way. The remaining gearing and motor currents will stay as before. Since voltage and rpm are 'free' only the minimal cost of the two gears being changed is the salient factor. Motor windings can remain the same since the engine torque is not being upgraded. The system continues to deal with the same torque as before but at a newer maximum rpm.

    Let's determine the max power point using ICE = 6000rpm, MG1= 12000rpm.
    Then 12000 - 3.6 x 6000 = - 2.6 x MG2,
    so MG2 = 3692rpm and since 7200rpm = 100mph.....

    The current Prius engine does not reach full power until 51.28mph, and the calculation shows this suggested new arrangement won't change things either. Of course MG2 would now be rated at 60kw with somewhat higher iron losses but these would be compensated by improved cooling. This is still the same vehicle so the rolling losses haven't changed, just the time the system can be run at full power at maximum acceleration has been reduced. It must be obvious to most that the more powerful you make the car the shorter the time you are going to have to use that power if top speed, as here, is clipped at 100mph. And this is what the designers are banking on. This also means that despite the expected performance uptick anyone who puts a towbar on this vehicle can still put the system at risk.

    In #104 replying to wwest earlier I wrote one of the problems with HSD is the ring gear and the components connected to it. Rotating this assembly beyond 6000rpm raises a serious balance issue. It represents the output shaft of the whole system and this rpm at 100mph is fine for a planetary connected to a 4 cyl engine, later on however it may turn out to be too slow for the higher speed small engines in the pipeline It will be interesting to see whether this ring gear increase is the choice Toyota will make. Everything has risk but it's not like the greater population are regularly driving or should be driving this vehicle above 85mph anyway that would repeatedly test 7200rpm speeds on this component.
    Finally I would like to see them copy the Camry design which has omitted the sprocket chain power takeoff - thereby possibly releasing a 6% gain in torque by my estimation. If you care to go to #470 on the Toyota Camry Hybrid board where USBSEAWOLF2000 has posted diagrams of the two systems you can see what I mean.

    I am fairly sure they won't go so far as to copy that second planetary used to raise the specific power of MG2 that you will also see there. For that matter I think HSD design will stagnate until the Chevy Volt appears or Honda returns with a new hybrid but not with their mechanical CVT that can't seem to reach 100k miles nor with the IMA which becomes ineffective when the HV battery is exposed to extended sub zero temperatures.
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