Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

What to expect from the next model year Prius



  • stevedebistevedebi LAPosts: 3,719
    "And just what do you think causes all that exhaust (gas) pressure, if not the HEAT of combustion? The Atkinson Cycle allows more EXPANSION, less pressure into the exhaust manifold, of the ignited A/F mixture during the power stroke relative to normal "Otto" engines."

    Your original statement was about there being insufficient heat from an Atkinson cycle to run a turbo. I gather from your response that you meant that there was insufficient pressure to run the turbo.

    I can't quite tell if you agree with me vis-a-vis superchargers, but the point is that if you put in a smaller engine to maintain the MPG you don't gain a lot of power. Plus it adds weight and complexity to the engine.

    Note also that you can't "turn on" the power of a SC when desired; it is always on, boosting power and reducing MPG.

    Toyota isn't interested in maxing out the performance of the Prius; it is strictly designed for maximizing fuel economy.
  • stevegoldstevegold Posts: 185
    It depends. An "electric turbo" is only on when the pedal is floored. In my case, I only need the boost 5% of the time.
    A slightly smaller, more efficient engine would be fine 95% of the time and on the rare occasions when I do need the boost, it would be there. I think my normal 45-48mpg would go up to over 50mpg except for 5% of the time when the "turbo" was on.
  • wwestwwest Posts: 10,706
    In the exhaust manifold of a car HEAT IS Pressure...

    If you could make the combustion process fully efficient the exhaust gasses would exit the cyclinder at the exact same temperature at which they initially entered the cyclinder.

    The Atkinson Cycle gets more efficiency from the fuel BURN by extracting more of the HEAT and converting it to mechanical motion. Less HEAT/(pressure) at BDC equals less pressure into the exhaust manifold once the exhaust valve opens.

    The SC technique I described allows for continuously variable boost pressure from zero to the maximum allowed by the mechanical limits of the engine and thereby NO LOAD on the ICE until boost is required/called for.
  • stevedebistevedebi LAPosts: 3,719
    "It depends. An "electric turbo" is only on when the pedal is floored. In my case, I only need the boost 5% of the time. "

    I was speaking of supercharging, not Turbocharging.
  • stevedebistevedebi LAPosts: 3,719
    "In the exhaust manifold of a car HEAT IS Pressure..."

    Don't try and put that statement to an automotive engineer, or a physics professor.

    I don't understand what kind of "technique" you are describing. Superchargers use the engine power to mechanically enhance the airflow into the engine - the same principle as the turbo charger, except the turbo is driven by exhaust gas, and therefore increases as the engine RPM increases, whereas a supercharger provides constant power - but the energy to power the supercharger has to come from somewhere, and the equipment adds weight to the engine.
  • stevegoldstevegold Posts: 185

    This is the electric turbo that I thought would work well in the 2004 Prius. It runs at high speed off the 12VDC battery but only when you floor the accelerator.
  • pathstar1pathstar1 Posts: 1,015
    An Atkinson cycle engine with a supercharger is a Miller cycle engine. AKA Mazda 626. If you do a search on Atkinson cycle, the Miller cycle is also mentioned. It will not run without the supercharger. I have some experience with that, when the supercharger "ate" a hose clamp. :) I smile because it wasn't mine. I didn't get the privilege of paying $4000 to repair it. And "they" dis the Prius because "they" think the battery would be expensive to replace!

    While some may feel more HP is necessary, many of us think the Prius does just fine, thank you. Mine will out accelerate my previous vehicle on the two lane secondary highways when passing 18 wheelers (it was a 240 HP 265 lb-ft torque 2001 Nissan Pathfinder, which, BTW, burned 2.5 times as much fuel for the same service). It will not keep up from a stop, mainly due to the "delay" of 1/2 to 1 sec. at startup.

    At any rate, this discussion is of the 2009 model, which, from all accounts, will not have a supercharger or turbocharger. In fact, it now appears it will be the last year of the current version car. Most now conclude the 2010 model will be the "changeup" year. Probably will have the same engine, a double sized battery, with plug in capability, and a cruising range on battery only of around 10 km. But this is all speculation, based on comments from Toyota spokespeople and their tests with the double battery pack Prius plug in test vehicle in Japan and California. They have also given some hints as to body design changes. Just have a look at the "bean shaped" (my description, not intended as criticism) concept car shown last winter in Germany. "Many things you will see on future hybrid cars from Toyota are on this concept car." Note he said "many", not all.

    Several posts ago, someone said a gearbox will raise the HP output. Sorry, a gearbox will change the torque and the RPM, but the HP stays the same (actually it drops a bit, due to losses in the gearbox). Energy MUST be conserved!
  • stevedebistevedebi LAPosts: 3,719
    "An Atkinson cycle engine with a supercharger is a Miller cycle engine. AKA Mazda 626. If you do a search on Atkinson cycle, the Miller cycle is also mentioned."

    Don't look at me, I didn't suggest it; I was responding to a different post...
  • wwestwwest Posts: 10,706
    The Prius implementation of the Atkinson Cycle is more logical/virtual than real, but...

    The Prius is using delayed intake valve closing so that a portion of the A/F mixture is forced back out into the intake manifold (and into the "opposite" cylinder currently on an intake stroke) during the compression stroke. The result is effectively, logically, the same as with an actual Atkinson Cycle engine, a "lengthening" of the power stroke in comparison to the intake stroke.

    But in order to keep some of the "power" normally lost to the Atkinson Cycle the Prius' mechanical compression ratio is raised to 13:1 leaving an effective ratio still at 10:1.

    Basically that means using an SC would raise the "effective" CR above 10:1 which the engine may not be able to stand up to in the long term, even in short bursts of 30 seconds.

    Additionally I would be willing to bet that the e-charger's 1 PSI boost is only at low to mid engine RPM and actually goes negative, starving the engine, as it reaches the RPM in what would normally be PEAK HP.

    A toy, at best.
  • toyolla2toyolla2 Posts: 158
    Although Julian Edgar of Autospeed did find improvement with a turbocharger, his was an anaemic pre-Gen 1 model that was shipped from the Japanese market to Australia and not available in North America. The Gen I and Gen II that arrived on our shores in comparison are fully able to drive their MG1s to their full rating of 100 Amps. Increasing the power of their engines with some sort of forced induction scheme will not improve their performance. Here's why.
    First it should be noted that the magnetic field of MG1, which indirectly controls engine torque, is produced by neodymium magnets which are not adjustable. The effect of this field is that MG1 requires a torque value of 22lbs-ft from the sun gear when generating 100 amps of current. Since this generated current is electronically regulated not to exceed 100 Amps this simultaneously places a useable torque limitation on the engine. In other words it doesn't matter how much more torque capability you endow this engine with, it just cannot be allowed to push MG1 into generating more than 100 Amps or it will overload that machine. The intractable situation is that the more powerful you can make the engine, the more severe the throttling back by the Prius control system will be.

    Next regarding the gearbox ratio change, I'm assuming we're referring to the 4.113 transaxle ratio, which offers some possibilities. The Prius system develops its maximum contant power output of 104Hp from 51mph to 100mph so the gear ratio is ineffectual in this area as someone pointed out. On the other hand the point at which the constant power is reached can be lowered by using a higher ratio and that would have the effect of reducing the 0 to 50mph acceleration timing and improving hill climbing ability.

    Changing 4.113 to 5.00 will lower the entrance to the max constant power point to just 40mph. The result being the that the previously 68.6Hp being developed by the engine at this speed will be upped to the 76Hp maximum. A 10.8 % increase ? No, not quite, because the battery is supplying 28Hp so the actual System increase is only (104-68.6-28)/(68.6+28) X 100 = 7.7% . This is a surprising result since most of us would expect a 20% improvement in torque going from basically 4:1 to 5:1 in the final ratio. So at 40 mph only a 7.7% improvement is realized. The problem here is that you're fighting two constant power systems. MG2 constant power from 20mph to 50mph and then the engine itself from 51mph speeds and up.
    The 20% improvement should be present in the 0 to 20mph range, not that you would much notice, but then it becomes minimal in the all important 20 to 50mph range.

    I am going to leave this discussion by simply noting that it appears that in these connected constant power systems you cannot just improve one component i.e. the engine by itself. You will need to upgrade the MG1s and MG2s as well. The transaxle ratio (4.113) or the HSD planetary ratio (2.6) are merely the glue that holds the system together. I am sure that alteration to the HSD ratio to accommodate greater engine torque will lead to further circular reasoning that will oblige upgrades on the other electrical equipment to be necessary as well.

    As a side issue, the genius of the HSD becomes particularly apparent here. As MG2 fades above 51mph (the volts/herz issue) makeup power comes automatically from the direct mechanical link at 6.6Hp per 10mph. At 100mph 66Hp comes directly from the engine, while the now less capable MG2 will only be required to handle 38Hp (10Hp+28Hp). This would correlate well with electric motor theory were MG2 an induction motor, but with a brushless motor it's difficult to predict exactly how much power MG2 could deliver beyond the mandatory 10Hp as top speed is approached. Any takers ?
  • 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.
Sign In or Register to comment.