Talk:Hybrid Synergy Drive

Schematics
At the end of the article schematics of the drive are given showing what connects to what. The Camry hybrid does not conform to any of these schematics. In particular it uses two gears and the R gears are connected and the output comes from the R gear. The motor goes into S on the second gear. C on the second gear is held still. See http://www.osti.gov/bridge/servlets/purl/922327-5ktfCi/922327.PDF.

I agree with other peoples comments that for many people a definition of S, C, and R would be good.

Hlovatt (talk) 04:54, 8 January 2009 (UTC)

Figures
I'm confused over the figures illustrating the HSD. None of the figures have legends. What do the different labels mean? (70.229.84.73 21:46, 10 April 2007 (UTC)), ADM

This article desperately needs a figure and a more consistent explanation.

It seems like this article should be broken up further. The performance aspects of the Hybrid Synergy Drive article center on the Prius. The Highlander (AKA Kluger) and the Lexus offer superior performance compared to the non-hybrid versions. They accelerate quicker 0-60, don't have limited top speed when the battery is low, dramatically better mid-cruise acceleration, and better MPG.

Reverse Gear
The article states: "Reverse gear: There is no reverse gear as in a conventional gearbox: the computer feeds negative voltage to MG2, applying negative torque to the wheels."

Both MG1 and MG2 are permanent magnet AC motors. They aren't fed "negative voltage" to reverse the torque. It should read "reverse phase sequence is applied to MG2" Wefoij (talk) 05:58, 16 January 2008 (UTC)

MG-T and MG-S?
Why use MG-T and MG-S here? Isn't that just being deliberately perverse, given that this article is specifically discussing Toyota's Hybrid Synergy Drive, and they use the names MG1 and MG2? --KJBracey 22:53, 12 November 2005 (UTC)

I used MG-T and MG-S in the original write-up because they're more mnemonic (for "torque" and "speed") than MG-1 and MG-2; my intent was to make the text easier to understand to the casual reader. (I own one of the darned things and I always forget which is which -- how can a casual reader expect to remember?) If you feel strongly about it, go ahead and change it -- thanks for asking first, though. zowie 23:43, 12 November 2005 (UTC)


 * I know what you mean - I can never remember which one is MG1 and which is MG2 myself. But then if Wikipedia used Toyota's terms throughout the article, it might help us remember :) --KJBracey 16:46, 13 November 2005 (UTC)

List of vehicles available with HSD
Given that this section is inherently about hybrid versions, from the heading, personally I prefer generic vehicle names, rather than the specific versions. Looks neater, and specific versions will get messier when we get vehicles with more than one hybrid variant. Also "Toyota Camry is available with HSD" is a bit less of a tautology than "Toyota Camry Hybrid is available with HSD". Does this make sense? --KJBracey 06:45, 24 January 2006 (UTC)
 * You are correct about the problems with saying "X Hybrid is available with HSD" so I am changing it to a list of vehicles with HSD and listing specific models. You may change it if you wish. I will, however, preserve the links to the conventional cars. CGameProgrammer 18:35, 11 April 2006 (UTC)

Should the stated release dates of these cars be the model year (MY) or the actual year they were or will be released? Currently it's showing actual year of release. CGameProgrammer 15:16, 12 April 2006 (UTC)
 * "Model year" is a specifically US concept, as far as I'm aware, so I'd avoid it. Giving the year of release is unambiguous. --KJBracey 11:59, 13 April 2006 (UTC)
 * Is it really? I thought the model year is a car industry concept.  Almost no car maker change their car model on Jan 1 of each year, hence the model year seldom align with calendar year.  For example, many cars change model around October or sometimes earlier for debuts.  I wonder how non-US markets label a 2006 Prius produced in 2005 (first released sometimes in 2005) vs. a 2005 Prius that was produced just a month earlier?  On the door jam of all the cars in the US, a metal plaque has the "model year" and the "manufacturing date" etched in.  Are you telling me that Japanese cars sold to Europe don't have that info?  Kowloonese 21:44, 13 April 2006 (UTC)
 * No, we do not have a "model year". Cars can change at any point of the year. And they don't change on a yearly interval. They're marked with a manufacturing date. We never talk about the "2004 Corolla" or "2005 Focus". We might say "Mark 2" or "Mark 3". --KJBracey 09:18, 14 April 2006 (UTC)
 * When you buy a used car in Europe, how do you tell one model from another if the model name stays the same? Even if you are picking a car from a new car lot, how do you know the Sept 2005 car you want to buy is the same as the Oct 2005 and not the Aug 2005 next to it?  For example, the Accord and Camry has change body styling and internal feature or even engine design without changing the model name.  Do you name them Camry mark 2 or Camry mark 3 etc?  When do you introduce a different mark number?  Who standardize on this number?  The used car dealer or the manufacturer?  In the US, each model year change a mark number because the car maker usually changed something in the design or production process each year and it is worth noting as a model year change.  I know there are exception, e.g. 2004 and 2005 Prius are identical cars.  Car makers usually add some visible external changes to indicate a model change too.  e.g. the 2006 has many non-functional changes on the body to give out the clues.  The MY serves the same purpose as the mark you suggested.  Even if the model year is only a US concept, it is a concept that makes sense.  If you don't read the MY as the production date, there is no confusion.  If you know corporate accounting, fiscal year and calendar year seldom line up either, yet it does not stop people saying "the 2006 fiscal years starts on April 1, 2006 and ends on March 31, 2007."  The model year is even more useful when the model year don't always change on the same day like the fiscal year.  I wonder why the Europeans don't use it. Kowloonese 22:04, 14 April 2006 (UTC)
 * The "Mark" numbers are informal names concocted by the public, and often aren't fully standardised. Eg for the Ford Escort, I believe there have been disputes over whether one version was the "Mark V" or just a revised "Mark IV". The manufacturers themselves just say "New" when they're introduced, usually - eg my 2004 Prius brochure says "New Prius" on the front. In used car guides, cars are listed by year of availability (eg Prius 00–03, Prius 04–). Minor changes of spec (quite common) are often not specially noted, but used car guides will list them, by month of introduction. I think the main reason we don't use "Model Years" is simply that manufacturers do not traditionally have a yearly cycle. The concept isn't flexible enough to cope with the irregular, and often frequent changes that happen. The manufacturers do not normally introduce regular changes just to indicate a "model year" change.
 * Oh, and one other important point - in the UK, our number plates (registration plates) show the year of registration via a simple letter code. So you can instantly tell the age of the car by that. So you would normally refer to an old car as being "T-reg" (T registration) rather than 1999. So years often don't come into it anyway. --KJBracey 10:06, 16 April 2006 (UTC)
 * Unless you include the month and year of the release date. Otherwise the calender year carry insufficient information when car models are concerned.  e.g. A Oct 2005 vs. a Sept 2005 car can be two completely different models.  Saying 2005 alone is ambiguous.  Kowloonese 22:39, 13 April 2006 (UTC)
 * I like Kowloonese' points. I'll change it to model year, but precede each year with MY. CGameProgrammer 23:23, 13 April 2006 (UTC)
 * Well, what a mess. It now is pretty incomprehensible, at least to my European eyes. I'm sure I could work backwards to figure out when exactly these cars were sold, but it just looks like a deliberate attempt to obfuscate the facts. --KJBracey 09:20, 14 April 2006 (UTC)
 * I hesitated to use monthly release dates because cars are released in different countries at different times. But I have no real objections to it so I'll keep it, and just make some corrections. It's true that having 2007 models released in March 2006 is quite confusing. CGameProgrammer 17:03, 14 April 2006 (UTC)

It would be useful if a knowledgeable person could update this article to include recent Toyota vehicles using HSD, such as the 2013 Avalon. Halberstadt (talk) 23:28, 30 March 2013 (UTC)

Proposal to merge with Comparison of Toyota hybrids

 * Oppose - Hybrid synergy driver article is long enough. There is a link to the comparison in the HSD article.  If people want to see the car comparison they can click on the link. Daniel.Cardenas 01:53, 21 April 2006 (UTC)
 * Comment - I proposed the merge, on the grounds that Comparison of Toyota hybrids is not encyclopedic on its own; put in the context of a broader discussion of Toyota Hybrid technology, though, the table has merit. AKADriver 15:45, 21 April 2006 (UTC)
 * Oppose - The table on its own is not encyclopedic, but it wouldn't really add much to this section either. It's comparing the vehicles as a whole, and doesn't really have much to do with HSD. Maybe a somewhat different table comparing the actual variations in the HSD (number of cells, motor power, engine power, etc) would be relevant here, but not that. --KJBracey 16:47, 21 April 2006 (UTC)
 * Good point. Daniel, what do you think?  Comparing these cars' hybrid systems that way (rather than on nebulous whole-car terms like "unique styling") would, I think, be very useful and encyclopedic. AKADriver 16:55, 21 April 2006 (UTC)
 * O.K. I'll try to find that info and put it in there. If someone knows where it is I'll add it.  Is adding this info what you are suggesting? Daniel.Cardenas 20:29, 21 April 2006 (UTC)
 * Oppose - I agree completely with KJBracey. HSD is meant to be about only the operation of the HSD; it isn't meant to be a discussion of the vehicles themselves. In fact this article may need a bit of cleanup.CGameProgrammer 17:51, 21 April 2006 (UTC)
 * Oppose - I agree with previous sentiments. Additionally, one can imagine the comparison page containing information about the relative reliability of the different models, comparison of sales figures, etc.  Even if its "Encyclopedic" status is a bit weak at the moment, it clearly, IMHO, has much potential.  The HSD is just one aspect of that comparison.  Theflyer 12:34, 17 June 2006 (UTC)
 * Oppose - This article deals with the drive itself, common to all the other cars. If there is non-HSD content in the article it should be removed to other articles. Since there have been no yes votes, I am going to remove the rename template. 205.175.225.5 20:27, 6 July 2006 (UTC)

Comparison of Escape Hybrid with CRV
Originally, someone claimed the Escape Hybrid's real-world mileage of 28-32 was "comparable to a conventional four-cylinder SUV such as the Honda CRV". This is B.S. A quick check at fueleconomy.gov shows the CR-V's real-world numbers at 20-24 for all versions (2WD, 4WD, manual, automatic) while the Escape Hybrid averages between 28-34. Probably a case of comparing real-world numbers of one car to EPA estimates of another. The Escape Hybrid is, in fact, the most fuel-efficient SUV in existence, as far as I am aware. Also it incorrectly stated Ford licensed HSD from Toyota, which isn't accurate. Ford developed their own technology but it was nearly identical to HSD so they needed a license from Toyota. CGameProgrammer 17:51, 21 April 2006 (UTC)

Toyota Corolla Hybrid
In 2008, the Corolla will also have a HSD hybrid version. .

Moved from page, there is no evidence for this. However, Toyota will eventually release a version, as stated in their model refresh plans. Just a matter of time, but it is speculation at this point and I have moved it here for that reason. --Ng.j 04:27, 19 March 2007 (UTC)

"Noticeably" less than twice the fuel efficiency of a conventional four-door sedan?
"The Toyota Prius has decent, but not sport-car-like, acceleration but has extremely high mileage for a mid sized four-door sedan: 45 mpg (US) is typical of brief city jaunts; 55 mpg is not uncommon, especially for extended drives (which allows the engine to warm up fully). This is noticeably less than twice the fuel efficiency of a similarly equipped four-door sedan with a conventional power train. Not all of the extra efficiency of the Prius is due to the HSD system [...]"

I don't quite understand the bolded sentence. It seems like it's trying to state the fact that 45city/55highway is less than two times the fuel economy of similar, but conventionally powered, vehicles. However, saying "noticeably less than twice" has more of a negative connotation to it while "slightly less than twice" seems more neutral. Isn't average gas mileage for similar, conventional sedans something like 25city/30highway? That makes a difference of five (5) mpg per category (according to the 2x factor), which doesn't seem worthy of "noticeably". Does anyone else have thoughts on this or care to do some additional research? --Godfoster 00:29, 24 May 2007 (UTC)

I agree that the way it is phrased now is not neutral. Doing a little bit more research on the EPA's fueleconomy.gov shows that the Prius, on the pre-2008 test cycle, scored 60 city, 51 highway, 55 combined. For 2008, the test cycle has changed, and the Prius scores 48 city, 45 highway, 46 combined. http://www.fueleconomy.gov/feg/2008car1tablef.jsp?salesArea=all In comparison, sedans like the conventional 4 cyl Honda Accord score 21 city, 31 hwy, 25 combined on the 2008 cycle. The conventional 4 cyl Toyota Camry scores 21 city 30 hwy, 24 combined. Smaller cars like the Corolla and the Civic score closer to the Prius at 26/35/29 and 25/36/29 respectively.

For the city measure, the Prius's mileage is very close to or exceeding twice the mileage of similarly sized cars. On the highway, the Prius's advantage is approximately 50%. I propose the section you mentioned be modified to reflect this research. LaughingMan11 04:20, 25 May 2007 (UTC)

Neutral Gear
The article states that '... HSD "neutral gear" is achieved by turning the engine off ...'. I don't think this is accurate, though my knowledge comes from instrumentation and discussion of the NHW11 Prius, before Toyota started calling the powertrain the "HSD". In that car, the main thing that happens when you put the mode selector in N is that the motor/generator drive electronics is (usually) disabled. This prevents torque from being applied to the wheels from either the engine or the motor generators themselves. In some circumstances, the engine will still run, mainly to prevent MG2 MG1 from spinning excessively fast. This information comes from Toyota's "New Car Features" publication, is accepted in discussion groups and I have personally verified it in an instrumented MY 2001 Prius. Can anyone state positively that there the HSD operates in a different manner?--GrahamDavies 19:46, 20 August 2007 (UTC)

With deep respect for Graham, I believe it's MG1 that has to be rpm limited.Shannock9 (talk) 08:58, 6 August 2013 (UTC)

Yes, thanks for picking this up. Correction made. GrahamDavies (talk) 11:31, 23 September 2016 (UTC)


 * I do not think neutral in the HSD relies on stationary planetary gears. For example, ICE can be run in neutral without sending traction to the wheels. This is a common condition: when ICE has been activated by low SOC before selecting neutral. It is correct that in neutral circuits to all motors are open (to prevent unintended drive to the car). All energy consumed by ICE operation is wasted (as heat) and HB will be drained by car electronics. Running ICE then delivers power only into the path of low resistance: freely spinning / open circuit motors. This gives the same effect as neutral in a conventional car (it pushes easily in either direction, and rolls freely backwards down a slight incline, even with ICE running) but without physically disengaging ICE from the drive train. Quite a neat feature of the HSD planetary gear set. It is worth being clear, as this Wikipedia page is one of the few accessible places that deals with this topic. R Ge B (talk) 02:55, 21 October 2023 (UTC)

Fair use rationale for Image:Lexus hybrid logo.GIF
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BetacommandBot 16:16, 1 October 2007 (UTC)


 * So apparently the problem was that the rationale didn't mention which article the logo was in. Thanks for fixing that, Addhoc! Issue resolved. Enigma3542002 18:44, 1 October 2007 (UTC)

Size of engine and motors?
Could we get a few words about how big the engine is (displacement) and it's horsepower rating, and the the horsepower ratings of the electric motors? physical dimensions might be interesting too. —Preceding unsigned comment added by 68.80.95.189 (talk) 00:26, 4 March 2009 (UTC)

CVT?
An image of what appears to be a Toyota Super CVT-i transmission has been included in this article. This is not a component of the HSD, not does the HSD use the variable diameter pulley mechanism that that transmission uses.

The HSD does not actually have a CVT in it at all, it's the power split device that allows the HSD to *act* like a CVT.

Suggest this image should be removed. —Preceding unsigned comment added by Grs1969 (talk • contribs) 20:08, 29 September 2009 (UTC)


 * Thanks. Although a number of HSD cars use the Super CVT-i, the image is replaced. SynergyStar (talk) 20:21, 29 September 2009 (UTC)

The article is misleading. It states the planetary gear (power spitter) acts as a CVT. Erm not really. A conventional CVT is in-line. That is, in a conventional setup the transmission is between the engine and wheels, shifting ratios to suit. It is in-line, in series: engine -> transmission -> wheels. The Prius presents to the wheels an electric motor - electric motors do not not require an interim in-line (in series) transmission as the torque delivery is far superior than an IC engine. How it presents to the wheels, what they think is an electric motor by using an IC engine and electric motor, is to split the power between them. The IC engine can deliver anything from 0 to 100% of power and the same for the electric motor - or anything along the 1-100 line, such as 60% electric motor and 40% IC engine. The Power Splitter (the so-called CVT) act in a parallel fashion - between the two motors to make them act as one motor at the output. Think of the two motors as "one" motor in one package, with the Power Splitter combining the output of the two of them. —Preceding unsigned comment added by 79.65.93.232 (talk) 21:54, 25 January 2010 (UTC) Kickbacks to Wiki? —Preceding unsigned comment added by 64.9.58.69 (talk) 23:00, 16 December 2010 (UTC)

Not a citation
But I can personally vouch for the rough behavior described at the end of the Performance section:
 * This results in a large decline in performance under certain conditions: an early-model Prius can achieve over 90 mph (140 km/h) on a 6 degree upward slope, but after about 2,000 feet (610 m) of altitude climb the battery is exhausted and the car can only achieve 55–60 mph on the same slope.

I owned two different Priuses(sp?), a 2005 and a 2006 model, which aren't even the very early models. I made a cross country move from the East Coast to Seattle in the first, and another from Seattle back to the East Coast in the second. In both cases, while crossing the Rockies, I had to climb a particularly tough slope at least once, with a car stuffed to the brim with my stuff (probably the equivalent weight of a driver plus 3-4 passengers), and in the East to West move, I had a second passenger to boot. I was going 84 MPH from South Dakota through Montana whenever I could (tires are rated for 85, and I was sticking to 9 miles over the 75 MPH speed limit to limit the damage if I got a ticket). But on a particularly long uphill slope heading west in Wyoming, I got about halfway up the mountain at that speed (using cruise control) before the battery ran out. The instant the battery drained, I dropped to about 50 MPH, and even flooring the accelerator manually I couldn't get above 54-56 MPH until I reached the top of the mountain a couple minutes later. On the way back, I had a similar experience on a long upward slope (not quite a mountain) in Montana, but luckily, the problem only kicked in about 10 seconds from where the slope leveled off and began to go down again, so it wasn't a big issue. In both cases I was traveling in May; the vent was on but not the AC, as the temperature in the mountains was in the high 50s to low 70s range.

Like I said, this isn't a proper citation, but even on a later model Prius (can't say for the very latest model), draining the battery is a possibility and has a *very* noticeable effect on performance. &mdash;ShadowRanger (talk 17:23, 5 August 2010 (UTC)

Possible citation
From memory the NHW11 motors are rated by Toyota at 33kW and the ICE at 76kW. The correct values (or values for a newer model) could easily be cited to support an added phrase such as "because the max power drops by a third".

We don't have those kind of climbs in the UK. My experience is that with both power sources operating it drives like a high spec Golf. With battery depleted it drives like an old beetle. Shannock9 (talk) 08:53, 6 August 2013 (UTC)

"The most efficient speed (RPM) for an ICE is often around 1500–2000 RPM..."
I don't believe this is accurate. This might be the best speed (not necessarily with respect to thermodynamic efficiency) for an Atkinson Cycle engine in a hybrid, but a typical ICE in a non-hybrid vehicle is more thermodynamically efficient at much higher RPMs-this is from the "Engine Efficiency" article:

"Engine efficiency peaks in most applications at around 75% of rated engine power, which is also the range of greatest engine torque (e.g. in most modern passenger automobile engines with a redline of about 6,000 RPM, maximum torque is obtained at about 4,500 RPM, and maximum engine power is obtained at about 6,000 RPM). At all other combinations of engine speed and torque, the thermal efficiency is less than this maximum.”

Perhaps the existing sentence is too vague or broad to begin with.

VTEC1981 (talk) 07:04, 16 December 2015 (UTC)

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Confusing sentence
I'm confused by this sentence:
 * When cruising at high speed, the engine turns more slowly than the wheels but develops more torque than needed. MG2 then runs as a generator to remove the excess engine torque, producing power that is fed to MG1 acting as a motor to increase the wheel speed.

Is MG1 connected to the wheels? I thought MG1 sits between engine and battery/MG2. If this sentence is correct as written, then this mode of operation is missing from the "Power flows" section in the article. AxelBoldt (talk) 18:39, 16 August 2017 (UTC)

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Sales
if someone can find sale figs outside the US as well