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Old 03-31-2012, 11:31 AM   #1 (permalink)
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prius cvt maximum power

anyone know the limits of the prius transmission?

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Old 03-31-2012, 02:43 PM   #2 (permalink)
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Prius doesn't have a CVT
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Old 04-01-2012, 05:35 PM   #3 (permalink)
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Quote:
Originally Posted by mx73 View Post
anyone know the limits of the prius transmission?
Hi mx73,
I was hoping someone with more knowledge would respond, but nobody has made a peep. I found a nice old description of the original Toyota synergy drive and the Honda IMA here by The Eindhoven Technical University. Figure 4 shows that the Prius Internal Combustion Engine (circa 2004) could produce about 100 nm. Figure 6 shows the electrical machine characteristics. MG1 can produce up to about 80 nm. (oddly, the motor & generator curves for MG1 are symmetrical)
Formula 2.6, shows the relationship between the ring gear rpm and ICE rpm and rpm of MG1. Essentially MG1 sets the equivalent gear ratio. For example if MG1 is held at 0 rpm then the ring gear will spin at 1.46 times the ICE speed. If MG1 is made to run at twice the ICE speed then the ring gear will spin at 0.57 times the ICE. And if MG1 runs backwards at twice the ICE speed the equivalent ratio is about 2.37 (btw I used the ratio given in the Eindhoven paper 78:36. But everybody else says 78:30)
This variable ratio scheme works as long at MG1 can produce (or absorb if running as a generator) enough torque to "over power" the ICE torque. The ratio between the engine driving the sun gear and MG1 driving the planet carrier is 30:23. So MG1 only needs to produce about 76% as much torque as the ICE at any rpm.

Getting back to your question, if you wanted to attach a synergy drive to a more powerful engine, you'd need to replace MG1 too. There are very similar eCVTs on other cars too, the Highlander Hybrid has a 3.5 L V-6 that produces 336 nm The Lexus GS 450h says 360 nm. So they must have appropriately powered MG1.
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Old 04-07-2012, 01:03 AM   #4 (permalink)
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From the way I understand it, Generation 3 Hybrid synergy drive is universal for Prius, Highlander, and Lexus versions. The different applications generation of electricity may not be effected by the size of the engine in this particular application as the engine, regardless of size, is attached to a eCVT and completely computer controlled system which both generates power with and puts power into the MG1 assembly of the transaxle. But if you use a Prius transaxle in a custom application with new motor controllers...
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Old 04-07-2012, 01:24 AM   #5 (permalink)
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so what if i put 3-400hp/tq through it
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Old 04-07-2012, 09:49 AM   #6 (permalink)
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I don't think it designed to handle that much raw HP. Look at the HP rating of the three hybrids I mentioned and you might be able to get away with another 20-50hp but then again it could blow up.
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Old 04-07-2012, 12:21 PM   #7 (permalink)
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Like mort said above, I'd say the issue is the capability of MG1. Mechanically, it's just a planetary gearset, which I would assume can hold a LOT of power without busting. There's no clutches or anything like that. You could probably replace MG1 with something else (like a strong DC motor) or rewind it for more amps, but then what would you control the whole mishmash with? THAT would be the complicated part. BUT...if you succeed, it would be the coolest thing ever!
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Old 04-07-2012, 01:05 PM   #8 (permalink)
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Quote:
Originally Posted by mx73 View Post
so what if i put 3-400hp/tq through it
Hi mx,
Persanity's understanding is a bit off. Each of the different classes of hybrids that Toyota makes has a different transmission, each transmission is designed to mate with a narrow range of gasoline engines and drive a certain size car. The heart of the Synergy drive is MG1, the transmission ratio selector. It must produce enough torque to counter the ICE torque through the planetary gears. The big rear wheel drive Lexus cars have a 2 speed planetary gear changer in the transmission for a wider operating range. The LS 600H has a 350+ HP V8 and a 120 HP traction motor compared to the Prius 98 HP engine and 22 HP motor. You know the transmission in the Prius and the 600H are not interchangeable.

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Old 04-08-2012, 02:27 PM   #9 (permalink)
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so im better off trying to find a ls600 setup
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Old 04-10-2012, 04:36 AM   #10 (permalink)
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If you're planning to put it in a rear-driver, yes.

I do recall Autospeed turbocharging a Prius, but they never got anywhere close to those torque figures... maybe nearer 200 ft-lbs.

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