The Drive-a-Toyota Act

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My Honda Civic and Ford Escape 4 cyl both run around 2000 RPM at 60MPH.
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Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

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A Ford Focus SW I rented last year in the UK went 3,000 rpm at 70mph. My Concord is 2,100 rpm at that speed.
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who wrote:

According to the Toyota article, the car would go less than a mile on battery alone at low speed. What does that tell you about where the car gets most of its fuel efficiency from? (hint: a very efficient IC engine) As I said in another post, it would be interesting for someone to rip out the batteries and control electronics and see what the economy would be with just the IC engine. It might be found that the savings due to lower weight might just about offset the gains from regenerative braking.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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Quite possibly. But you'd also lose the ability to run both power plants when accelerating, so it would hurt performance. A fair test would require putting in an engine that would give you the same performance as the current hybrid power plant.
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Joe Pfeiffer wrote:

There is some truth to that. Still, it might be interesting to see what mileage the car gets in a controlled test (with the hybrid configuration as a baseline) on the existing IC engine but with the weight and complexity of the batteries and its control paraphernalia removed. OK - and a second test with just an IC engine with the same efficiency optimizations as the current one but with more power (scaled up/larger displacement).
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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I've often wondered that, as I watch the car get 50mpg on long drives on flat freeway with apparently zero help, or very very minimal help, from the electric motors.
I bet that engine as it sits is a dog off the line, though.
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Elmo P. Shagnasty wrote:

I think the car has other things for fuel efficiency, like harder tires for less rolling resistance, better aerodynamic shape, and, I guess, no alternator, all of which save energy. Plus it has a continuously variable transmission, which is more efficient that automatic and manual transmissions. And it has aluminum hood (bonnet for those of you in the UK) and hatch instead of steel, to save weight.
Cars can also have electrically powered water pumps, power steering pumps, valves, and compressors for the air conditioners, although I don't know if any do, yet.
Plus, the Prius uses an Atkinson cycle engine than a regular (Otto) gas engine, which is more efficient.
Jeff
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"Jeff" ...

hot day and using the AC, it makes the engine run a lot to keep the battery at a relatively even charge. When 'normally' driven (meaning on roads without jams), the normal electric generation that the car does from engine waste and slowing makes AC usage close to 'free' as far as I can tell. Tomes
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Jeff wrote:

An honest question: All those things suck energy whether mechanically or electricaly powered (and the power has to ultimately come from the IC engine). For each one, is the electrical version inherently more efficient than a mechanically powered (belt or gear driven) one?
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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Bill Putney wrote:

I think the electrically powered ones of these are usually more efficient, because they can be more efficiently shot off (even if you shut off the A/C, there still is loss from friction in the pulleys) and they operate at the proper speed (the A/C compressor in my car would run a lot fast if I drive in 3rd gear on the highway instead of 5th).
Plus, I think the generating mechanism on a hybrid means less wasted energy.
Jeff

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Jeff wrote:

OK - makes sense.

Assuming you're not meaning strictly the regenerative braking, can you explain what you mean? You're saying that the mechanism it uses to convert mechanical energy into electrical energy is more efficient than the alternator (the auto mfgrs. are back to calling them generators now) in a traditional car? How is it done?
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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Bill Putney wrote:

A generator converts mechanical energy to DC current, not A/C current. Because Toyota is so concerned with efficiency with the Prius, having an efficient generator system must have been a priority. And the output doesn't have to be converted to D/C with a rectifier. There's power loss in the rectifier. (All automotive alternators have them.)
Plus, the drive to the generators is direct drive, not belt drive driven, so there is less friction loss with a generator than a belt-drive.
It is also inherently more efficient to drive these things from electricity than directly from belts, because they run at the proper speed, not a speed determined by the engine. Plus, you don't need to run the engine to run the A/C or other things, which saves on fuel (although you need to run the engine every now and then to recharge the batteries or otherwise recharge the batteries) and you can use regenerative braking to recharge the batteries.
SO there are a whole bunch of reasons why it is better to run these things off of electricity, not just one.
Jeff

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Jeff wrote:

Semantic technical point here: Yes - a generator converts mechanical energy to electrical energy. It is only initial convention (before portable alternators became practical with the development of compact and efficient solid-state rectification means) that originally limited the word generator to d.c. generating devices (basically from common usage of the word in the context of the automobile).
Later, when the portable alternator was developed (or became practical - and almost necessary due to the increasing current demands of cars), just to distinguish the terminology, they came up with the term "alternator" (which -yes - does suggest a.c. from a pure language standpoint). However, there really is no reason the term generator - from a pure language standpoint - could not mean alternator in that it *generates* (i.e., no reason any device that generates *anything* could not be referred to as a "generator").
NOW - having said that - one point I was making is that many of the auto manufacturers have, within the last 5 or 10 years (not sure of the exact time frame - they kind of snuck it in on us), in their documentation (service manuals, etc.) gone back to the term "generator" to mean what they had previously been calling (and you and I still call out of habit) "alternators". And there's nothing wrong with that. If you look at an alternator as a black box - ignoring what's inside - it turns mechanical energy into d.c. voltage and current. So - hey call it a generator if you want to. (And as I pointed out - even if it's final output *were* a.c., from a pure language perspective, there would be no reason no to call that too a generator.)
Just wanted to get that fun point out of the way.
Now - let's go a little further (and I'm not sure how this will tie in to the discussion of hybrid cars) - what you and I know as alternators pushed the "generator" (meaning d.c. generator) aside in the automotive world because it (the alternator) was inherently more capable of high current output across a much wider useable rpm range (i.e, the traditional d.c. generator could not supply the increasing current demands that cars were requiring in sustained low speed and stop and go driving unless they were geared up to spin faster at low engine rpm to the point that they would fly apart on the upper end of the rpm scale).

And perhaps there have been some technological developments that have overcome the previous rpm range limitations of the (d.c.) generator. Perhaps the engine is running at a more constant rpm with the drive train used in the hybrid? I don't know.

You may not have said that the way you intended to, but the way you stated it, I don't buy that. There is nothing that says a (d.c.) generator inherently has to be direct driven and that an alternator has to be belt driven/cannot be direct driven. So unless I missed something there, let's scratch that part of the explanation.
In reality, I would not be surprised to find out that what they use and call a "generator" is actually more like what you and I commonly refer to as an alternator. I would also suggest that there is a bit of electronic processing done on the raw output of the waveform that comes out of this spinning device as to muddy the difference between what you and I think of as generators and alternators and their traditional differences such that we might have trouble deciding which category in traditional terms whatever is in the Prius really fits into. In addition, it would blend with the manufacturers tendency to now call alternators generators anyway.

All true - I see those points.

Got it.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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Bill Putney wrote:

I should clarify here that there is an almost-unmuddiable aspect of the alternators and generators (using the terms in the traditional pre-90's automotive sense). That is that the generator will have a commutator (to switch current in the windings as it rotates) whereas an alternator has slip rings (no commutation/switching of current) on the armature. So while there are probably some uncrossable differences, some of those still could be muddied, especially if you get jiggy with the electronics processing of the output of whichever device is used (i.e, like replacing the brushes and commutator with electronics, etc.)
We think of an alternator as having a field current that is teaked for regulation. A generator could have coils instead of permanent magnets for playing the same game. In that case, the commutation would be the only real difference - the rectification coming from the commutator (in a generator) up front of the actual power generation vs. in the diodes (alternator) after the fact. See what I mean about muddying the differences?
*BUT*, to reiterate, it still is likely that the Prius uses what we traditionally think of as an alternator but is utilizing the retro-term "generator" in line with the trend in the automotive world. (BTW - since my previous post, I actually found a reference that said that the SAE, in 1993, started officially encouraging the dropping of the "misleading term alternator" and instead using the "proper term generator".)
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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http://www.ecrostech.com/prius/original/Understanding/MotorGenerators.htm
from the start page:
http://www.ecrostech.com/prius/original/InitialContents.htm
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if you want a real education on this look up the gmc truck hybrid that has been around since 02 the engine quits when it comes to a stop and the engine restarts when u pull away and u never know it i drove one and didn't know till i had to work on it after the test drive and was looking for some wiring
Bill Putney wrote:

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Bill Putney wrote:

Well, the generator is A/C. I thought it would be D/C, but I was wrong.
http://www.hybridsynergydrive.com/en/generator.html

When the belts go around the pulley, they flex. This results in some friction inside the belt. The pulleys are not friction free, either. This added friction, compared with direct drive, results in some power loss. By getting rid of the belts and pulleys, you decrease the friction, which increases efficiency.
There is no reason why you can't have a DC generator or an A/C generator belt driven or direct drive.

When you convert A/C to DC or vice versa, there is energy loss (as heat in the diodes). This leads to lower efficiency. Apparently, Toyota got over this, because the generator is A/C, not DC.
http://www.hybridsynergydrive.com/en/generator.html

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Jeff wrote:

As I indicated, I'm not surprised. I would call itr an educatred guess rather than a lucky guess on my part.

I was just making sure you understood that point that there was nothing inherent about a d.c. generator being direct drive and an "alternator" (now called generator) being non-direct drive and therefore less efficient.

Yes - due to the forward bias voltage drop (on the order of .7 to 1.5 volts depending on instantaneous current level) - inefficiency (waste heat) there would equal that voltage drop times the current.
Regarding Toyota's having gotten around that as you speculate, very likely there are no passive diodes for the rectification. As the article you linked said, it apparently is a synchronous electronic control. Very likely, the switching components (under electronic control rather than the passive action of current reversal as in a diode) are what are called power MOSFETs. These are a special kind of "transistor" that do not have a non-linear voltage drop when turned on (conducting). When turned on, they look like a resistor. The beefier you make them, the lower the resistance that they have when turned on. SO - make them stout enough, and you can get that (resistive) voltage drop *way* below the typical .7 to 1.5 volts of a silicone diode. *THAT'S* how you pick up efficiency there for a.c. to d.c. rectification.
Also, the control leg of a MOSFET (called the "gate") takes almost no current to keep it in the turned-on state (unlike a transistor that requires continuous current on the base to stay on). There is a second order efficiency gain afforded by use of MOSFETS. (For accuracy, I will say here that the gates do have some drive current requirements when switching from one state to the other, but essentially zero current is required once the switching has occurred. So at lower frequencies of these generators, those switching losses are pretty small.)
Let me take this opportunity to correct what appears to be a misconception on your part about "d.c. generators" and their efficiency compared to alternators (with diode rectification): There is a good deal of inefficiency in the commutation (constant switching going on at the brushes) in a traditional d.c. generator. I don't have the numbers, but I would not expect a d.c. generator to have any more efficiency than an a.c. alternator with its rectifiers (I don't have the numbers on me, so I could be wrong about that - but keep reading...).
Here's a basic piece of info. to keep in mind: A rotating generator (stator or permanent magnet and moving coil) - in the simplest form possible *IS* an a.c. device. The simplest is with slip rings (or, as in the link you posted, with a stator coil and permanent magnets on the armature - which requires *no* brushes, no slip rings, no commutator - but that *IS* an a.c. device).
*SO* - and this is very important for you to understand: To get d.c. power out of *ANY* rotating generator *SOMETHING* has to be added to turn it into d.c. (i.e., to rectify it). The traditional d.c. generator does that by its commutation to switch the current in the armature coil *while* the power is being generated. The a.c. alternator with diode rectification does the job *after* the a.c. power is generated without commutation (slip ring instead). Both have their inherent inefficiencies.
So you can't just ding the a.c. alternator for inefficiency for its rectifier losses without being fair and recognizing the commutation losses in the d.c. generator.
Here's something to think about: What does it do to a d.c. generator's efficiency when the brushes are passing over the gap between one commutator segment and the next? There is a part of that transition period in which the brushes are shorting those two segments together. What about tolerance variation in the widths of those gaps between segments and their relative angular locations around the circle of commutation?
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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Not necessarily--but the fact that the engine isn't directly driving the AC compressor means that the engine can shut off, or run at its peak efficiency as needed to charge the battery. This saves bunches of gas and keeps a huge amount of pollutants out of the air. The battery can then dole out whatever energy it needs to whatever system demands it at any given moment.
Shoot, every car could learn from Toyota's systems.
The beauty of Toyota's HSD (Hybrid Synergy Drive) is, in typical Japanese fashion, at many levels. The software controlling the battery to dole out energy means the engine can be responsible for, and tuned for, one task: keep the battery charged. The engine doesn't have to run as much at incredibly inefficient levels, such as when idling for the sole purpose of running the AC or the radio or other electrical systems.
With those electric motors there to help with low end grunt and getting the car moving, the engine can be tuned more specifically for running at certain efficient speeds.
True, the engine does mechanically drive things quite a bit of the time, and always over 42mph. But it does so with varying involvement, with the software determining how much engine output goes to the wheels and how much goes back to the battery. That's the purpose of the Power Split Device (PSD) and the two motor/generators: to decouple the engine and allow varying amounts of engine power to go to various duties.
Decoupling the engine from the wheels like the PSD does is freaking genius. Toyota got two motor/generators and power delivery out of a very small and lightweight device, which is incredibly less complex than a modern automatic transmission.
Also, they programmed the brakes to be by wire. That's right, the brake pedal tells the computer what you want to do. Down to 7mph, the generators do the braking. The result: brakes last forever. Yes, the software has panic stops programmed for, and the car has a brake pressure accumulator (one of the many little noises you hear) that is always at the ready to slam the mechanical brakes for a panic stop.
http://www.cleangreencar.co.nz/page/prius-technical-info
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On Fri, 06 Jul 2007 19:06:21 -0400, "Elmo P. Shagnasty"

I always thought electric motors would make AWD very simple.
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