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Discussion Starter #1
Does anyone have a torque/HP curve graph for the Prius? The Toyota site only give the electric motor torque up to 1200rpm and then the peak gas motor torque.

Any help would be appreciated.
 

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Sorry, John, but this is absolutely not was he/she was asking for : your curve represents acceleration versus time.

I've uploaded a scan of torque and power graphs in the technical section of the album
(in French, "couple" = torque, "puissance" = power, "vitesse" = speed) :

http://www.priusonline.com/album_pic.php?pic_id=14

You can also access to a big press document (French.pdf) including these graphs (p.106) in the Prius-France Yahoo group in the files section (and the same in German too) :

http://autos.groups.yahoo.com/group/PRIUS-FRANCE/files

You'll have to be a member, however.
 
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Hi All:

___The first Prius torque curve looks a little odd? With the 01-03 Prius and Camry, there is a less then
infinite slope through any acceleration/deceleration as there should be. If the 04 Prius had a change in Gs over 0 seconds as shown (at t=0) I dont believe it can? There is no such thing as an instantaneous change in Gs in 0 seconds in an automobile? Maybe the graph is exaggerated by some amount? The third derivative gives jerk and with the change as shown, I would have to say the graph isnt possible even with a top fuel dragster. At least not without tearing the fillings out of your teeth any time you were to floor the Prius at exactly 30 mph ;)

___Frenchie, do you know where to find a US speced Power (HP) and Torque (Ft.-lbs) for an 04 Prius can be located? The look of the graph wouldnt change but the numbers and nomenclature would make it easier for us in the States and much of Canada to understand.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:3ccrx2vj][email protected][/email:3ccrx2vj]
 

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Hi Wayne,
xcel said:
___The first Prius torque curve looks a little odd? With the 01-03 Prius and Camry, there is a less then
infinite slope through any acceleration/deceleration as there should be. If the 04 Prius had a change in Gs over 0 seconds as shown (at t=0) I dont believe it can? There is no such thing as an instantaneous change in Gs in 0 seconds in an automobile? Maybe the graph is exaggerated by some amount? The third derivative gives jerk and with the change as shown, I would have to say the graph isnt possible even with a top fuel dragster. At least not without tearing the fillings out of your teeth any time you were to floor the Prius at exactly 30 mph ;)

___Frenchie, do you know where to find a US speced Power (HP) and Torque (Ft.-lbs) for an 04 Prius can be located? The look of the graph wouldnt change but the numbers and nomenclature would make it easier for us in the States and much of Canada to understand.
I think nothing wrong with the graphs.
The first curve is by the Motor torque. It is well known behavior the max torque is produced at zero speed by a motor.
As you may know, unlike Insight, Prius can start and run without engine running.
The second graph is a popular engine curve, and the third is just the first one plus the second combined.

You can see the specifications of US models at...
http://www.toyota.com/vehicles/2004/prius/specs.html

The numbers are shown on the site, and it is easy to apply these on the graphs.

Regards,
Ken
 
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Hi Ken1784:

___Frenchies graphs dont appear wrong, John1701as do? There is too great a change in Gs over to small a time frame at t=0 seconds to be a real G/time graph for most any automobile. Johns graph was not a HP/torque vs. Engine RPM but a Gs vs. time.

___I am still looking for a real world HP/Torque curve instead of those that Toyota provides for the Prius just in case a little fudging is going on Almost 300 Ft.-lbs of torque across that wide a band is a bit much and I am trying to find independent verification is all?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:3escu0v1][email protected][/email:3escu0v1]
 

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Discussion Starter #7
Thanks for the info guys. It is still unclear to me that why, with the near instantaneous torque, does the Prius have such mediocre 0-60 acceleration? Is the battery discharge not powerful enough to power the electric motors beyond 1200RPM? Or is it that the rate of discharge is not long enough to keep the motors turning for the required time?

In either case it would seem to be an issue of not enough discharge. If that is the case can anyone tell me why Toyota didn't use a larger battery pack? It's quite compact and only weighs about 45kg.
 
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Hi 1967 R50/2:

___I have been searching for a real world dyno run of the 01-03 and the 04 Prius for almost a week now and I cannot find anything? I think Toyota is fudging the numbers by saying the Electrics can assist up to 295 Ft.-lbs of torque anywhere in the range of 0 1,200 RPM the instant (t=0 again) they come on line. I also think they are taking the 295 Ft.-lbs. from the electric motors shaft instead of at the wheels like everybody else does. That torque value is simply way to high not to show some truly amazing performance numbers for something as light as the Prius imho.

___Frenchies curves seem to have been derived form a Toyota press release as well? Does anyone know where some real world HP/Torque curves are for either the 01-03 or the 04 Prius are?

___I found a paper done by Argonne (that or NREL or the Idaho government lab) that dyno tested the 01-03 Prius across a range of RPMs for emissions, SOC, and any other number of attributes except for pure HP and torque vs. RPM. The tables listed showed a maximum of just under 100 Ft.-lbs yet the 01-03 Prius torque value according to Toyota was a touch above 250 Ft.-lbs from 0 - 500 RPM?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:385a4ckq][email protected][/email:385a4ckq]
 

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I think Toyota is fudging the numbers by saying the Electrics can assist up to 295 Ft.-lbs of torque anywhere in the range of 0 1,200 RPM the instant (t=0 again) they come on line.
No. This is normal behaviour for an electric motor.
I also think they are taking the 295 Ft.-lbs. from the electric motors shaft instead of at the wheels like everybody else does.
Wrong. Torque figures are usually given at the engine (or motor) shaft, because torque at the wheels depends on the gear... except in the Prius because there's only one gear (the Prius is so to speak always in "top gear").
That torque value is simply way to high not to show some truly amazing performance numbers for something as light as the Prius imho.
Wrong again. Consider the different gear ratios, calculate the torque at the wheels and you'll see it's lower than on many cars in first gear.
Frenchies curves seem to have been derived form a Toyota press release as well? Does anyone know where some real world HP/Torque curves are for either the 01-03 or the 04 Prius are?
This document (in French, German, English at least) can be found at toyota-media.com. It's a website for professional journalists, but you can subscribe for a 48h temporary access to all the files. I've downloaded some interesting documents on my hard drive, and could send them to PriusOnline but there's no place to put them... :cry:
I found a paper done by Argonne (that or NREL or the Idaho government lab) that dyno tested the 01-03 Prius across a range of RPMs for emissions, SOC, and any other number of attributes except for pure HP and torque vs. RPM. The tables listed showed a maximum of just under 100 Ft.-lbs
I don't know which document you're referring to. I've seen some (about the old Japanese Prius) in which the engine was tested, and the peak torque was about 100 Nm, not 100 Ft-lb's (even in the USA is the metric system making some progress :wink: ).
 

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Hi all,
1967 R50/2 said:
It is still unclear to me that why, with the near instantaneous torque, does the Prius have such mediocre 0-60 acceleration?
The huge torque lasts only up to 30km/h, please refer to the right graph by frenchie.
Beyond that, the torque is not so huge, then the result came.
1967 R50/2 said:
Is the battery discharge not powerful enough to power the electric motors beyond 1200RPM? Or is it that the rate of discharge is not long enough to keep the motors turning for the required time?
The battery is powerful enough at least the first 10 seconds for 0-60.
It is programmed for efficiency, not for performance.
1967 R50/2 said:
In either case it would seem to be an issue of not enough discharge. If that is the case can anyone tell me why Toyota did use a larger battery pack? It's quite compact and only weighs about 45kg.
It look you need more performance than good mileage. Prius is a consumer product and is well balanced, I think. In other words, maybe someone is not happy it's performance.

xcel said:
I think Toyota is fudging the numbers by saying the Electrics can assist up to 295 Ft.-lbs of torque anywhere in the range of 0 1,200 RPM the instant (t=0 again) they come on line.
The specification is officially published, and Toyota can't be fudging there.
xcel said:
I also think they are taking the 295 Ft.-lbs. from the electric motors shaft instead of at the wheels like everybody else does. That torque value is simply way to high not to show some truly amazing performance numbers for something as light as the Prius imho.
You may be right, gross vs net. However the 295 Ft.-lb is still real number.
xcel said:
___Frenchies curves seem to have been derived form a Toyota press release as well? Does anyone know where some real world HP/Torque curves are for either the 01-03 or the 04 Prius are?
Motor Performance Curve for both classic and '04.
http://www.toyota.co.jp/en/tech/environ ... /high.html

If you agree that the max torque is produced at zero speed by a motor, everything will be solved.
- A DC motor example;
http://lancet.mit.edu/motors/motors4.html
- There is a known formula; F = ma. The max torque causes max acceleration(G).
- The traction control is avoiding the wheel spin at start.
http://www.toyota.co.jp/en/tech/environ ... ystem.html

Regards,
Ken
 

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Although it primarily covers the 2001-2003 Prius, the well presented information at Graham's site is also quite useful to understanding the basic concepts of the 2004 Prius. Check out:
http://home.earthlink.net/~graham1/MyTo ... Frames.htm

Poke around in the "Understanding Your Prius" section. He does a great job describing how the electric motors work and implications of the simplified gearing system of the Prius.
 
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Hi All:

___Max torque at 0 RPM isnt even a question as that is how electrical motors work. What has me questioning Toyotas numbers is the steady maximum torque across the 0 - 1,200 RPM band. This is not normal electric motor behavior at all. What kind of motor(s) allow this? With that kind of torque, you would want the Prius drivetrain to stay at low RPMs almost continually yet the HSD doesnt seem to allow the use of all of that available torque at low RPMs as can be seen in the 0 - 30 or 0 - 60 mph figures? Flooring the Prius from a stop brings the ICE online practically instantaneously and with it, a heck of an increase in dB output which sounds like the RPMs are rising quickly? The only torque curves I have seen are from Toyota themselves and Frenchie provided curves that appear to be generated from a Toyota press release? The 4th graph in the Motor Performance graph from Toyota Japan actually states Shaft torque on its ordinate axis? I suppose the stronger MG Set could be supplying less torque to the other as RPMs rise to keep the flat output possibly which makes sense. 295 Ft.-lbs just seems like it could tear the tires off the Prius is all yet from a seat of the pants perspective, around what feels like 15 mph is the kick really felt. I have mere minutes behind the windscreen of an 04 however? Anyone find Dyno plot of the 04 Prius yet? There is a company in the SouthWest that is going to be performing the tests in early April or so but I have not seen an actual dyno test on an 01-03 or an 04 to cooberate Toyotas posted specifications is all?

___As for where I saw the ~ 100 Ft.-Lb. figure, it was ~ 100 N-m as shown on page 28 and 29 of this document entitled Performance and Emissions of the Toyota Prius. Unfortunately, it appears as if this data is the ICE motor all by its lonesome

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:2tafbb9m][email protected][/email:2tafbb9m]
 

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With that kind of torque, you would want the Prius drivetrain to stay at low RPMs almost continually yet the HSD doesnt seem to allow the use of all of that available torque at low RPMs as can be seen in the 0 - 30 or 0 - 60 mph figures?
Yes it does. As RSnyder suggested, you should have a look at Graham's enlightening web site to understand this.
Flooring the Prius from a stop brings the ICE online practically instantaneously and with it, a heck of an increase in dB output which sounds like the RPMs are rising quickly?
Don't mix engine RPM with motor(s) RPM. Practically you can't hear the electric motors spinning. Rotation speed of MG2 (the "big" electric motor) is always directly proportional to vehicle speed, since there is a fixed gear ratio (about 4.1 if I remember correctly). Don't forget also that electricity is exclusively produced by the engine on the Prius; consequently, for maximum efficiency it's better to use directly engine mechanical energy when the engine can operate in its good efficiency zone. Experienced Prius drivers know that the key to maximum fuel economy is NOT to avoid thermal engine operation, but to force its operation in the optimum zone, hence avoiding low (and very high) engine RPMs.

As for electric motors torque curves, I don't know and will try to document myself.
 

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xcel said:
What has me questioning Toyotas numbers is the steady maximum torque across the 0 - 1,200 RPM band. This is not normal electric motor behavior at all. What kind of motor(s) allow this?
"THS II uses an AC synchronous-type motor, which is a high-efficiency DC brushless motor with AC current. ", Toyota's official web site says.
I don't have any documents about the flat torque either.
But, my guessing is a kind of current limitation to the motor...
- The efficiency is low at low rpm, therefore high current produces a lot of heat.
- It is not a good idea to get more torque suplying more current under such low efficient rpm.
If anyone knows better answer, please let me know.
xcel said:
With that kind of torque, you would want the Prius drivetrain to stay at low RPMs almost continually yet the HSD doesnt seem to allow the use of all of that available torque at low RPMs as can be seen in the 0 - 30 or 0 - 60 mph figures?
The flat torque area only affects up to 20 MPH. I haven't seen any 0-20 MPH data.
xcel said:
Flooring the Prius from a stop brings the ICE online practically instantaneously and with it, a heck of an increase in dB output which sounds like the RPMs are rising quickly? The only torque curves I have seen are from Toyota themselves and Frenchie provided curves that appear to be generated from a Toyota press release? The 4th graph in the Motor Performance graph from Toyota Japan actually states Shaft torque on its ordinate axis?
http://www.toyota.co.jp/en/tech/environ ... ystem.html
"Driving Power Performance" graph shows colorful explanation. It is same as frenchie's right one. I believe you can get better understanding from this.

Ken
 

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A quick summary that might help (but see Graham's site for the best explanations).

Under full acceleration (pedal to the metal), there are two torque sources to the drive train. 1) A powerful motor/generator (called MG2), which is permanently attached to the final drive assembly (no transmission, just a few reduction gears). 2) A gasoline engine (ICE) which is connected via the power split device (a combination of a very simple planetary gear arrangement and a second not so powerful motor/generator called MG1).
From the point of view of MG2, the Prius has a one speed "manual" transmission which is always in "high" gear. From the point of view of the ICE, the Prius presents a load, and only a vague connection to the wheels (like a slipping clutch but without wasting any energy). As frenchie mentioned, you hear the ICE, not MG2. But unlike traditional cars, the ICE speed and loudness is not closely related to the wheel speed, it's primarily a function of power requested.

The input to MG2 is precisely controlled by computers based on its shaft position, speed and desired torque. It may help to think of it as a stepper motor, it's not an AC motor except by coincidence. There is no fixed frequency AC source being supplied to it as would be the case for an AC motor connected to a wall plug. Within milliseconds of flooring the accelerator pedal, the computers will send full current from the battery through the motor at a phase angle 90 deg ahead of the permanent magnet rotor. This gives the maximum torque of the motor. As the motor starts turning, it starts acting like a generator which tends to counter the current provided by the computer from the battery. Up to around 1200 rpm, the computers can compensate by increasing the phase angle slightly to maintain max torque. Eventually, the "back EMF" has an effect and torque drops off with motor RPM.

The computer also starts the ICE if needed and brings up its RPM and power output by opening the throttle. This takes a second or two. A small fraction of its power output goes directly to the power train, but the bulk goes to electric power generated by MG1. This electric power is also fed to MG2 to supplement the power from the battery. As wheel speed increases, the ICE is allowed to run at higher RPM and the power split increases its proportion directly to the wheels while reducing the proportion to MG1. Thus the Prius slowly transitions from almost all power to the wheels coming from MG2 at close to 0 MPH to an even balance at highway speeds (60 MPH in the 01-03 Prius), to mostly from the ICE at very high speeds.

But most driving is not done at full accelerator pedal and the computers change modes quite frequently throughout the drive to minimize emissions, maximize efficient use of the fuel, and maintain optimal battery charge for the longest lifetime.
 

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Hello Robert,
Very helpful explanation, thank you.

Some comments from me...
RSnyder said:
A small fraction of its power output goes directly to the power train, but the bulk goes to electric power generated by MG1.
Using Graham's number, 72% of ICE torque goes to the power train and 28% torque goes to MG1.
RSnyder said:
As wheel speed increases, the ICE is allowed to run at higher RPM and the power split increases its proportion directly to the wheels while reducing the proportion to MG1.
According to Graham's site, the proportion is unchanged, it's always 72%vs28%.

Ken
 

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Keep in mind that power and torque are different (though related) concepts. You're right that the torque split is always the same and favors the direct to drive train path. Power, however, is torque times angular velocity (RPM). Since at low speeds the drive train is moving very slowly, and since MG1 is usually running much faster, the bulk of the engine's power output goes to MG1.

Although it's unusual for the engine to be providing power while the Prius is stopped, when it does, all power goes to MG1 (since 72% of the torque x zero RPM is still zero power to the drive train).

Normally, MG2 gets the Prius moving long before the engine load is increased. That's because rapid changes in engine load cause large bursts of pollution and the Prius does not want to do that.

Under full acceleration, MG1 spins at it's highest permitted rate (10,000 RPM in the 2004, 8,000 RPM in the 2001-03), whereas even at 100 MPH, the drive train is only going 6,000 RPM in the 01-03, I think faster in the 04. So you can see that even with the fixed 72% - 28% torque split favoring the drive train, the power split greatly favors MG1 until you're moving pretty fast. Under light loads, MG1 typically spins much slower, usually backwards, contributing power to the drive train rather than removing it from the engine. (But that's a story Graham loves to tell, so you really should go to his site for the gory details).
 

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Robert,
Thank you for the clarification, torque vs power.
RSnyder said:
Under full acceleration, MG1 spins at it's highest permitted rate (10,000 RPM in the 2004, 8,000 RPM in the 2001-03), whereas even at 100 MPH, the drive train is only going 6,000 RPM in the 01-03, I think faster in the 04.
Just a quick note...
MG1 limit is 6,500 RPM in the 2001-03.
It is stated at Graham's site and...
http://www.toyota.co.jp/en/tech/environ ... /high.html

Regards,
Ken
 
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