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Old 06-14-2009, 01:49 PM   #14 (permalink)
Matt Herring
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Join Date: Jun 2008
Location: North Andover, MA
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Bone's 2010 Prius - '10 Toyota Prius Black
90 day: 56.78 mpg (US)
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Originally Posted by bennelson View Post
Matt, half of what you said is over my head. I am not much of a Prius guy... but I AM learning.

An easy way to think of the Prius system is that it operates in 3 parts (the MG1, the MG2 and the ICE). All 3 work simultaneously with each other. When using ICE all 3 "parts" of the engine are spinning and working together. When MG1 spins forward, MG2 spins backwards...always on a counterbalance.

When in EV mode the rpm in the engine drops to 0 and the car runs off the battery alone until 42 mph and higher is reached and EV mode is replaced with ICE operation (MG1 and MG2 are not spinning under 42 mph in EV mode). This is where the "mystery" of the Ewert system leaves alot of questions to be answered. When in EV mode, around/near 62 mph the MG1 and MG2 reach their max load and become dangerously close to 70 mph I would expect severe negative impact on the MG1 and MG2.

Often, I will EV mode or ICE up to 41 mph, put it in neutral and coast down a hill "in EV mode"...this gives me the benefit of 0 rpm coast vs. ICE-on neutral coast (9999 mpg vs. 120 mpg on my SGII). On big downhills, I could leave it in EV mode and coast past 60 mph but I would also threaten the MG1 and MG2 by doing this. In these cases I will EV neutral coast up to about 55 mph and then either light brake or go into ICE to use engine braking to stay under 60 mph and overspin.

So, with the Ewert system at 70 mph in EV mode there has to be some "safeguard" to the system (I hope) that protects the MG1, MG2 and ICE from overspinning. Maybe it shuts the whole system down to 0 rpm and runs it off the larger battery. But, because the same Prius inverter is used to run the new 6kwh pack that ran the 1 kwh stock pack...running 110-140 amps at those speeds for the length of time they are doing it (10-15 minutes) would bring inverter temps beyond safe operation.

I've watched all the videos and read as much as I can find on it...but haven't found answers to these questions yet.
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