MG1 rpm ??

Hi Bob,

The thread title says MG1, but it looks you are looking for MG2 6,400rpm source.

Anyway, the MG1 rpm numbers are shown at following site;
TOYOTA: Company > Technology

I've never seen the MG2 6,400rpm data source on NHW20 yet.
We know the NHW20 max speed is 170km/h at Toyota UK site.
We know the 185/65R15 tire diameter is approx 620mm and the final gear ratio is 4.113 on the NHW20.
Then, the MG2 rpm at 170km/h becomes 5,983rpm.
This is my best answer.

Ken@Japan

 

Hi Ken, hi Bob,

Good math, but the tire size for european models is not the same, so let me put some european values here:

European tire size is 195/55R16, which corresponds to a tire diameter of 620.9 mm, circunference perimeter of 1950.6 mm.

This means that @170km/h the tire does 1487 rpm, which applying the final gear ratio of 4.113 gives the 6117 rpm MG2 value.

I can accept the 4% error margin in this calculations to reach the 6400 rpm MG2 limit without any problem.

By the way, the 6400 rpm speed limit on the current model's MG2 was on display in the cut-away model of the 2010 at Geneva, which I believe was also on display at Detroit. It is a Toyota fact.

Cheers!

 

Hi João,

My math is something different.
The 170km/h means 2833m/min.
Your 1950.6 mm tire will rotate 1453rpm at 2833m/min.
Then, your MG2 will rotate 5974rpm via 4.113 final gear.

Ken@Japan

 

I can see that, but I prefer mine

It's all down to how much precision you use, since the difference we're getting at is really almost negligible. You're loosing too much by rounding big units, hence the bigger error margin you have...

Here's how I got my numbers:

170 km/h = 170000 m / 60 s
that is the same to say
170000 m = distance made in 1 hour
the known perimeter for a 195/55R16 tire:
1.9506 m = tire perimeter
therefore
170000 / 1.9506 = 89236 tire rotations per hour at 170 km/h
therefore
89236 / 60 = 1487 tire rotations per minute at 170 km/h
applying the final gear ratio:
1487 * 4.113 = 6116 rpm at MG2

What this tells us is that there is room for using smaller tires. If we put a smaller diameter tire then MG2 will have to spin faster to reach the top speed.

I know that USA Prius have smaller wheels, or at least they used to have, so probably we should ask someone from the USA to make the same calculation for their smaller tire size.

It probably will hit the 6400 rpm MG2 speed limit, or at least will get realy close to it...

Cheers,

 

You got me lost here. Is it me or you have it all mixed up there?

Power = Torque x RPM

Allowing higher RPM has no effect at witch RPM the motor reaches its torque peak at all.

Having higher RPM capabilities allows the motor to reach the same power without having so much torque.

That's why you have lesser torque in the new motor, you don't have to, you have higher RPM. For the torque you now have the reduction planetary gear which increases the motor torque.

Am I seeing it wrong? Am I? Let me know if I am please.

Cheers,

 

Bob was talking about having heard about the top rpm having increased from 6400 rpm to 13500 rpm. This is the increase in rpm Toyota has said to have occur from the 2004/6 model to the 2010 at the MG2, not MG1.

The math me and Ken are doing is for the current 2004/6 model. We are playing around with ~6400 MG2 rpm, 195/55R16 tires and 170 km/h speed limit. All of these characteristics are from the current 2004/6 model.

The new 2010 has 13500 MG2 rpm, 215/45R17 tires and 180 km/h speed limit. All of those are European specs.

 

Why the confusion? I thought everyone that has studied the 2010 Prius transaxle knew that MG2 (the traction motor) operates at a spindle max. speed of 13,500 RPM and drives a speed reduction planetary gear (SRU) with a ratio of 2.636:1 to the final drive gearing. Hence the final drive speed reduction to 5121 RPM maximum, but with torque multiplication from 153 ft-lb to 403 ft-lb to the final drive output gearing.
On the speed issue relative to the 2004/2009 model Prius, you cannot just take the raw tire dimensions as quoted in determining rolling radii for the drive wheels, you have to actually measure the rolling radius of the wheel, which will vary with tire pressure. On my 2008 for instance, with stock tires at 42 PSI, the actual rolling radius at the contact pad area is 11.6", or 295 mm approximately, as opposed to the 310 mm used in your analysis. It is the effective radius that matters.

 

There's no confusion, there was a question by Bob regarding some rpm numbers, we merely tried to help answering a fellow member

You thought well. It seems you are the one confused. That was NOT the original question, just go back and read the original post.

Absolutely true! :rockon:
That's why I said the differences between my math and Ken's were negligible, and so was the difference from ~6100 to actual 6400 rpm limit on 2004/9 MG2. We were working on approximate values to check if the 6400 rpm value would fit or not. If we had reached say 10000 rpm then we would have a problem.

 

Are you a schoolteacher, by any chance?

 

Errr.... no.... why do you ask?

 

Mine is...
170000 / 1.9506 = 87152 tire rotations per hour at 170 km/h

Ken@Japan

 

Aaaahhhh!!!! Damn dyslexic-typo fingers!!!!

I did 1,90506 tire perimeter instead of 1.9506...

YOU ARE RIGHT!!!

The funny part now is to figure out how small the wheel can be so that MG2 would reach the 6400 rpm limit. I'll do that and double check... errr.... triple check... quadruple check my numbers this time...

 

Re: MG2 rpm ??

FYI,
Based on the MG2 max rpm numbers, the possible vehicle max speed will be as follows.
(assuming tire diameters are NHW20:0.620m(185/65R15) and ZVW30:0.635m(195/65R15) )

NHW20: 6400rpm / 4.113 = 1556rpm (max wheel rpm)
1556rpm*0.620m*3.1416*60min/1000 = 181.9 km/h (113.0mph)

ZVW30: 13500rpm / 2.636 / 3.267 = 1568rpm (max wheel rpm)
1568rpm*0.635m*3.1416*60min/1000 = 187.6 km/h (116.6mph)

Ken@Japan