0-60mph ECO vs. PWR

Anyone remember why it was called a CVT ?

The reason was simple, to make it fit into a pre-existing category. A decade ago, Toyota didn't want Prius to be identified as unique & new. So, they selected "CVT" as the type. Remember, they expended a great deal of effort making Prius fit into the mainstream market.

It's easy to look back and make an educated guess... but that often isn't the same answer you'd get from a decision made without knowledge of what's to follow.
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That's is an interpretation, fact is as you confirm they call it a cvt period.

 

So "they printed it so it must be true"?
Toyota also called it "very reliable", but then we got the recalls. Just because marketing says something doesn't make it true. If you don't believe that, -someone- is going to have all your money.

 

It seems fair to say that the HSD is a CVT as it transmits motion between the ICE and the wheels in a manner that is continuously variable.

It is however more informative to call it an eCVT as it works in a completely different manner (electrically) from mechanical CVTs and has completely different components with different issues.

For people who don't care about how it works or don't care about how the differences may affect them then calling it a CVT is not likely to be a problem.

For people who are interested in these things (eg a large portion of those on Priuschat), I think that eCVT is a more useful term.

 

You should all just take the oil out of your transmission because heck you don't need it. It is just Electrons from electricty thats moving your drive train and wheels.

Again it is pointed out it is ONE FIXed magical gear. So it is not a variable.

So why do you still insist on calling it ECVT? Where is the V?

HSD or Hybrid synergy drive doesn't not really describe much about the transmission.

Hybride just means it is a mix between electrical and pertrol powered

Syndergy just means in harmony.

Why keep bring up HSD? It is not a describtion of transmission.

You used to have just two types of transmission. Manual and Auto.

Then they invented the CVT to say that it is actually just an Auto but now you don't feel the shift of gears.

Thats is it! Stop calling it ECVT. Call it CT is more accurate. As long as there are physical gears thats moving the car it is not electrical transmission it won't ever be called that.

 

But the physical gearing path alone cannot move the car. Unless MG1 seizes. After it has started the ICE.

The electric path is absolutely essential to getting any power to flow through the PSD/eCVT. Break the electric path, and the gears spin freely while transmitting zero torque, just like a freely spinning drive wheel of an open differential car when that wheel is lifted off the ground.

 

It is fairly obvious to me that you have no idea how the HSD system works, yet you continue to argue with those on here that do. It reminds me of what a senior engineer used to tell the new "wet behind the ears" engineers - "You listen with your ears not your mouth, that is why God gave you two ears and only one mouth".

 

This thread once again reminds me of one of my favorite old sayings: "Never try to teach a pig to sing. It only wastes your time and annoys the pig."

I think the voice lessons are over.

Tom

 

Finally a balanced post, although I don't think the group is as large as you think it is ;-) and calling it eCVT is just confusion the non-anoraks as they might think what is that then and why don't I have it...

I really couldn't care less what it is called, the fact is toyota calls it cvt so lets not confuse people :thumb:

 

I don't want to get involved, but i'll offer up this link

Toyota Prius - Power Split Device

Being a visual person, it helped me to understand what was going on inside my prius.

Note: the PSD is interactive on that website... it's fun to play with

 

I know exactly how it works.

However, just seeing you saying that, it shows that you are just saying whatever others are saying and you have no clue what you are talking about either. Worst none of you seem to grasp the idea of Continous. And think that this is some sort of Magic (as if this car is powered by Harry Porter). Yeah thats a lot of understanding of the car.

First of all you all said that it is not a CVT because there are no gear or infinite gear ratios because it is a fixed gear meaning one gear. Ok so I take that. Then Variable should be taken out completely.

But yet you still want to gall it ecVt? Dumb? Not sure. Because you just cotradict what you are saying yourselves.

Also Toyota already named their trasmission CVT, whether it is a fixed gearing being the heart of the HSD with planteary gear sets, it doesnt' matter.

Toyota have named the car Prius so it will be Prius. Why would you want to call it otherwise?

It gets to me how elementry it can be that one just don't see what they themselves are saying.

Its like playing guitar to a cow. They wont ever get it. And therefore you can call it ECVT in your own little world but try not to confuse others why come here for advice about CVTs and you tell them it is not.

 

Fair enough.

New topic: Who is Harry Porter?

Tom

 

Daniel ratcliff

 

Radcliff actually

 

Looking at Toyota Prius - Power Split Device

At any given vehicle speed, you can have a whole lot of ICE speeds, which mean different torque. Who knows if power and eco mode don't also change this ?

 

He was a high jumper from the United States of America.

[ame="http://en.wikipedia.org/wiki/Harry_Porter"]Harry Porter - Wikipedia, the free encyclopedia[/ame]


Another one is a children's author

http://harry-porter.webs.com/

 

Regarding the videos: interesting and finally clear up the waters on what ECO and PWR mode do when the accelerator is floored down in both modes. In both modes, if floored, the behaviour of the Prius is the same. So this means, rightly so, that all the HPs/torque are available in both modes (or, all 3 modes, except obviously, EV mode).

Still I am not fully convinced that ECO mode and PWR mode are the same in terms of engine management and battery charge/discharge/current to motors strategy for accelerator positions other than "full throttle". Is there any way to prove that for a requested power output, the HSD delivers always the same amount of current to MG1 and so much current is drawn from MG2 at the same rpm of the ICE? is the overall energy balance managed the same in the 3 modes?



Regarding the CVT: when somebody interested in the Prius asks me about how it works, first I need to clarify that is not manual gearshift and that no, it is not an automatic gearshift (important difference here in Europe where most cars are manual); then I have to say, no, it is not a CVT and no, it does not behave like one. Then I have to clarify that there is no clutch or hydraulic coupling (like on automatic gearshift). After the shock of the listener has subdued, then comes the difficult part to explain how the PSD works.

If I am without paper, then I am out of luck. If I have paper I can explain a bit better, though I always get strange looks like as if I am describing sorcery of some sorts.
Then, the only way to give the poor listener something to mentally hold himself to (since he/she is used with 20-40 years of traditional car technology), I try to make parallels with a CVT and a clutch.

Though not likely not correct, I clarify first that the wheels are mechanically directly coupled and driven by the MG1 (though the torque does not necessarily come from it). Then I say that the ICE is not directly mechanically coupled to the wheels in any way, except via the MG1 and/or MG2. I say that the MG2 is like the alternator and that it behaves a bit like a "buffer" or "clutch" with no dispersion of energy.

Any extra torque from the engine, since it can run freely at whatever rpm is necessary and where it is most efficient, regardless of the wheel spin speed, gets buffered/absorbed by the MG2 and the current generated gets either used immediately from MG1 or saved in the HV battery for later use.

The fact that it seems to behave like a CVT, comes from the fact that there are no gears, that the ratio from the wheels to MG1 is fixed and that it sounds like a CVT, though it does not have the sluggish response usually you get from it.

For example, when driving slowly and the ICE is warming up, there is no real correlation between engine noise and the speed, as long as the battery has enough energy. The ICE can run at the necessary rpms to warm up most efficiently while the MG1 drives the wheels, depending on speed and battery charge, and the MG2 converts the ICE spins into battery charge and/or feeds the MG1.

When you floor the Prius, it seems like a CVT simply because any energy the MG1 cannot transfer from the ICE/battery gets converted from MG2 to current that goes into the battery (depending on charge). The ICE revs up and the car speed does not increase accordingly and makes the whole thing look/sound like a CVT. The ICE goes up in RPM (although not immediately at full rpms) and the car "doesn't move" as compared to the "roar" of the engine - though I have driven the CVT Honda Jazz/Fit of my father, and the Prius, does move without the engine needing to "whine"...
Compared to a traditional car, the Prius does not necessarily need to have the ICE roar, to move and the speed/acceleration is not always directly correlated to ICE noise, like e.g. in a manual transmission car.

Then I have to explain what is the HV battery, and that the 12V battery is not at all used to drive the car, but only to turn its electronics on. But not to drive MG2 or MG1 or anything else required to move the car like in a traditional car....

Depending who I am talking to, this whole excercise can take from some minutes to a good half hour...

Though the above might not be 100% correct (never talked to a Toyota HSD engineer...), it still does get some part of HSD idea through ("Really no clutch and gears!?!?!" - "Really").

 

Another analogy I use, for someone who already understands well what a differential do (such as anybody who got stuck in snow/ice in a Canadian winter ):

1. Take your regular front drive car, remove one of the front wheels and put some weight in the trunk, in the opposite side, such that the car stays level on its remaining three wheels.
   
2. Then, put the car in fifth gear, let the clutch engage and see what happens. The car will stay still, as all power/movement will go to the missing wheel.
   
3. Then, ask them to put an electric brake (aka a generator: MG1) where the missing wheel was. The more counter torque you exert on the missing wheel, the more power will go to the wheel on the ground.
   
4. If you leave the car in fifth gear and try to exert too much counter torque on the missing wheel, the engine will stall before the car starts to move. To solve this, take the electricity generated from the missing wheel electric brake (MG1), and give it to a second motor (MG2), attached to the remaining wheel touching ground. You can then avoid the ICE stalling and can always leave the clutch engaged and the transmission in fifth gear.
   
5. Finally, move MG1 and MG2 in their correct place with the "differential" (aka the PSD), put the missing wheel back on with a second differential between the two front wheels and the PSD, and you have a HSD.
   
   You can then explain all the added benefits (an energy buffer: the battery, the fact that the engine can now spin at a speed independent of the wheels speed, that you can even keep the engine stopped while moving the car, etc.).

 

Finally, someone who gets it.:rockon:

Another way of looking at it is to look at the function of the transmission and not be too concerned about how it works. Makes sense because CVT is a function, not a certain type of hardware.

For a given ICE rpm, there can be a wide, continuous range of output transmission output rpm. The gear ratio is input rpm/output rpm.

You can also hold the output constant while varying the input rpm and calculate gear ratios that way.

Guess what, it's Continuously Variable and it's a Transmission.
:cheer2:

The control system is wildly different than other types of CVT, the gear set does not change ratios, it just splits the torque but the end result is that the gear ratio between the ICE and the transmission output is continuously variable.