A few Prius comments, having puzzled out what ours is doing, at least most of the time...
turn on the a/c [...] Woohoo mpg plunged immediately to the low 30s
The MPG display is deceiving. It shows infinity (99) when running on electric power, although the energy being used did come from gas. And, when the gas engine is running while driving at relatively low speeds, the indicated MPG is usually low, as a significant amount of energy is going into the battery. So you get these huge swings from 99 to 30-40 that have nothing to do with what the overall milage is going to be.
Prius is basically an Echo with a $8,000 surcharge
For the 2001-2003 model, this was more or less true, although Echos generally weren't as well equipped. (My father-in-law has one of the old Priuses) For 2004, all is changed. The Prius has gone way upscale in size, style, trim quality, and standard features. Option up a Corolla to the feature level of a Prius, and the list price isn't really that much less. And the Prius is an all-around nicer, and somewhat more spacious car.
An electric-assist hybrid needs a horrendous, complicated transmission to split the load between the two power sources
This was one of the biggest surprises to me, once I figured out how the thing actually works. The Prius transmission is, mechanically, one the simplest ever, in any kind of car, in the entire history of cars. No clutches, no bands, no gears engaging or disengaging, no fluid torque converter, only a single gear. A Ford Model T transmission was complicated in comparison.
The transmission is a single planetary gear set. The gas engine is connected to the planetary gear carrier. The wheels are connected to the ring gear. A motor/generator is connected to the sun gear. A second motor/generator is hooked to the wheels (to the output shaft that drives them, anyhow) to let the car run on electric power, and for regenerative braking. That's it. All the transmission power-split voodoo is pure software. None of it is mechanical.
A motor/generator pair that could transfer the entire required driving power would almost certainly be bigger, heavier and more expensive than the Prius scheme of lesser motor/generators plus planetary gear set. I see no advantages to going that way. And you still would need equally clever software to work out when to run the engine (of whatever type) and how engine power (how much is optimum for best efficiency?) should be balanced between battery charging and wheel driving.
Priuses sold in Japan have a button to encourage the car to run in pure electric mode. It lets you make short city-driving trips without starting the engine. I don't know why they don't have it here - I wish they did. Add a plug-in battery charger you'd really have something interesting. A Prius will cruise along quite happily at 40 MPH on electric power only.
There are only a few cases where the Prius behaves a little differently or oddly
The brakes feel slightly different from conventional all-mechanical brakes, esp. with light braking. Not bad, really, just a little different. The previous generation Prius brakes were worse - the effects of the regenerative braking kicking in were much more noticeable.
If the engine is running while the car is stopped (can happen when the engine is cold, or if the battery is low), when the engine does shut off, the car will shudder a little. Toyota could eliminate this if they were willing to sacrifice the last drops of energy that they suck from the engine while it is spinning down. But they don't; drawing power from the generator on the sun gear also causes torque on the transmission output, and the car does shudder slightly when it goes away abruptly.
When creeping slowly up a very steep grade (15%+), you can feel a pulsing, which I think is probably the motor poles going by at low speed. Let off the brake without touching the gas on a similar grade, and the car will roll backwards slowly with a similar pulsing.
That's about it. In my opinion, Toyota has pretty much worked the kinks out of the design. The biggest remaining question is how long do the batteries really last.
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Date: 2004-11-02 07:16 am (UTC)A few Prius comments, having puzzled out what ours is doing, at least most of the time...
turn on the a/c [...] Woohoo mpg plunged immediately to the low 30s
The MPG display is deceiving. It shows infinity (99) when running on electric power, although the energy being used did come from gas. And, when the gas engine is running while driving at relatively low speeds, the indicated MPG is usually low, as a significant amount of energy is going into the battery. So you get these huge swings from 99 to 30-40 that have nothing to do with what the overall milage is going to be.
Prius is basically an Echo with a $8,000 surcharge
For the 2001-2003 model, this was more or less true, although Echos generally weren't as well equipped. (My father-in-law has one of the old Priuses) For 2004, all is changed. The Prius has gone way upscale in size, style, trim quality, and standard features. Option up a Corolla to the feature level of a Prius, and the list price isn't really that much less. And the Prius is an all-around nicer, and somewhat more spacious car.
An electric-assist hybrid needs a horrendous, complicated transmission to split the load between the two power sources
This was one of the biggest surprises to me, once I figured out how the thing actually works. The Prius transmission is, mechanically, one the simplest ever, in any kind of car, in the entire history of cars. No clutches, no bands, no gears engaging or disengaging, no fluid torque converter, only a single gear. A Ford Model T transmission was complicated in comparison.
The transmission is a single planetary gear set. The gas engine is connected to the planetary gear carrier. The wheels are connected to the ring gear. A motor/generator is connected to the sun gear. A second motor/generator is hooked to the wheels (to the output shaft that drives them, anyhow) to let the car run on electric power, and for regenerative braking. That's it. All the transmission power-split voodoo is pure software. None of it is mechanical.
A motor/generator pair that could transfer the entire required driving power would almost certainly be bigger, heavier and more expensive than the Prius scheme of lesser motor/generators plus planetary gear set. I see no advantages to going that way. And you still would need equally clever software to work out when to run the engine (of whatever type) and how engine power (how much is optimum for best efficiency?) should be balanced between battery charging and wheel driving.
Priuses sold in Japan have a button to encourage the car to run in pure electric mode. It lets you make short city-driving trips without starting the engine. I don't know why they don't have it here - I wish they did. Add a plug-in battery charger you'd really have something interesting. A Prius will cruise along quite happily at 40 MPH on electric power only.
There are only a few cases where the Prius behaves a little differently or oddly
That's about it. In my opinion, Toyota has pretty much worked the kinks out of the design. The biggest remaining question is how long do the batteries really last.