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Hybrid Vehicles Toyota Prius What to expect from the next model year Prius
311 messages, Last post on Apr 26, 2009 at 5:43 AM
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Replying to: wwest (Oct 16, 2007 1:08 pm) 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.
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Replying to: stevedebi (Oct 17, 2007 1:02 pm) 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.
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Replying to: stevedebi (Oct 17, 2007 1:02 pm) 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.
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Replying to: stevegold (Oct 17, 2007 1:45 pm) I was speaking of supercharging, not Turbocharging. |
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Replying to: wwest (Oct 17, 2007 2:23 pm) 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.
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Replying to: stevedebi (Oct 17, 2007 4:45 pm) 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. |
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Replying to: stevegold (Oct 17, 2007 6:30 pm) Thanks for the link, interesting stuff. A couple of notes: 1. It is electrically driven, so it would impact the HSD, and the effect would be worse when the vehicle was accelerating - the traction battery would have to run the supercharger AND the electric drive motors. This would deplete the battery faster. 2. ONE PSI boost? 3. I'm not sure if adding boost to an Atkinson cycle engine would increase power. On an Otto cycle engine it works, but the Atkinson cycle is deliberately intended to work with less pressure. I don't know enough to have a definite opinion, just a question.
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Replying to: stevedebi (Mar 15, 2006 4:44 pm)  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!
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Replying to: pathstar1 (Oct 18, 2007 11:48 am) Don't look at me, I didn't suggest it; I was responding to a different post... |
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Replying to: stevedebi (Mar 15, 2006 4:44 pm) 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. |
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