I've seen two articles, neither a copy of the other, that reported: I think we've established that the NHW11 MG1 maximum rpm is 6,500 rpm and the NHW20 MG1 is 10,000 rpm. So this "6,400 rpm" has me wondering about the source. Granted, it is one of those obscure Prius facts that tends to interest a very small sliver of Prius technologists but I'm in that camp. Any ideas of the source? One reason I ask is I think I'm seeing more NHW11 data cited as the older model data versus NHW20 data. Again, this is just another Prius gear head trying to make sure his facts and data are accurate. I'm good with using the NHW11 data for compare and contrast but didn't want to short change the NHW20. Thanks, Bob Wilson
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
Thanks! We slowly getting a clue about gear ratios and MG1/MG2 rpm speeds and limits. This is good and necessary for updated nemographs. Bob Wilson
I would suggest with a 5200RPM max engine RPM, that 10,000 RPM or more was retained if the main PSD gearing was the same. Allowing the higher RPM allows the engine to reach it's torque peak at a lower speed which helps with acceleration.
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,
I think we're flipping MG1 vs. MG2. The OP's question was MG1's (primary generator/engine starter) RPM max, which is 10,000 RPM in the current Gen2 Prius. Thinking about the nomiographs I've seen for Gen2 and how Toyota has allowed specific engine RPM at specific MG2 speeds, I suspect MG1's ratio hasn't changed much for Gen3. However now it would seem that they're looking for MG2's ratio, so I'm just off base. ;-) The Max RPM you guys are coming up with would be MG2's final output speed, but the actual rotor speed is in the 13,000 RPM range before reduction. We know it's in the 13,000 RPM range before reduction based on answers given in Detroit.
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.
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...
In theory, we could reduce the diameter of the drive tire and increase the linear force available for acceleration. The indicated speeds would be rubbish, you'd have to us a 'correction' table. But it would a nice way to shave a little time off the line. Conversely, the largest possible diameter tire would make acceleration a little slower but it would reach a higher top speed (assuming drag didn't become the limiting factor.) This was the technique used to set the Prius 'land speed record' a couple of years ago. In the meanwhile, my larger diameter tire experiment continues and they are still about 5% larger than the stock tires. Any direct fuel improvement is fleeting, too small to measure, in the noise. But it also shifts the hybrid knees, 42 mph and 70 mph (NHW11) up a bit. I like being able to keep up with traffic and still be under 42 mph for hybrid mode. (GRINS) Also, I can roll closer to 70 mph and still get acceptable, +50 MPG performance. Bob Wilson
I don't want to accrue 100,000 miles in 60,000 real miles. Besides, real MPG would suffer due to higher minimum RPM @ a given true speed. Kinda like flying all over again. Calculate true ground speed vs. indicated ground speed... ick.
What? What? Driving like "Top Gear" might not be efficient? I'm shocked! <GRINS> Hummmm, tires about 60% in diameter: .6*15 = 9 inch wheels I suppose some axle extenders might work but finding 9 inch wheels and tires with the load capacity would be a challenge. Actually I found some R13 tires, which would be about 85% in diameter compare to NHW20 tires. So looking at a Prius that goes 0-60 in say ~10 seconds, that might bring the times down. I'm pretty sure only the front wheels have to be changed. Sounds like a fun time at the track this summer. Bob Wilson
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
