Posted by Mr. G on January 31, 2009, 2:37 am
T. Johnson (email@example.com) says...
All the components are connected to the wheels via the planetary gearbox
(what is essentially a differential) The speed of any 1 component is
directly in proportion to the other components.
I think much of the disagreement is due to which is being called MG1 vs
MG2. I may have had it reversed from what some descriptions use, but
the relationship between the components is still the same.
Here is a flash gadget that demonstrates this. The references to
MG1/MG2 are reversed from my earlier description, but the concept
illustrated is the same:
This makes it very clear why you cannot exceed 42 MPH without spinning
the ICE, or else spinning the main EM above redline.
Posted by Was Istoben on January 31, 2009, 3:37 am
Back to something close to the original question, then, are the modified
plug-in 2G Prius limited to 41 mph in the all-electric mode? Apparently so.
If that is the case, then achieving 100 mpg with a 40-mile round trip
commute would be difficult if the commute is largely rural with speed limits
of 55 mph & up. Certainly there would be an improvement under such
I wonder if one of the improvements to the 3G eliminates or at least raises
this number closer to 60 mph. We'll know soon enough. In reading through
the sparse 3G material at the Toyota site I got the impression it was
configured for some future enhancement.
Posted by Tomes on January 31, 2009, 2:44 pm
"Mr. G" ...
Thanks for this link, it is enlightening. One thing that I can see clearly
from this is that I can set it so that at 110 MPH the MG2 is at 6500 RPM and
the ICE is at 0 RPM [zero]. This tells me that at over 42 MPH the ICE _can_
indeed be not spinning. Might there be some manner of connect/disconnect
between the ICE and the planets? Or how else is this explained?
Posted by Mr. G on January 31, 2009, 3:34 pm
The simulator will let you set it for 110 MPH with the ICE not running,
but that doesn't mean it can happen in reality (though the simulator
DOES try to indicate you're exceeding the limits). At 110 MPG and the
ICE at 0, MG1 would need to spin backwards at 16,900 RPM, which is more
that 2.5x the 6500 redline.
Try this: Set the ICE RPM to zero, and slide MG2 up until you hit 42
MPH. Everything is fine. BUT, if you try to make MG2 go any faster to
increase the vehicle speed, 3 things happen to indicate you're exceeding
- The MG1 tach turns red, to show you're exceeding the +/-6500 RPM
- The line showing the connection among the ICE/MG1/MG2 turns red
because you've gone beyond the parameters of what the flash can properly
display (it can't show any motor past its redline)
- The line actually starts to bend, which becomes more obvious the
further you push MG2. This line must be straight, which illustrates the
direct mechanical connection via the planetary gears, just as in a RWD
So to your last question, there is NO disconnect anywhere in this
system; no clutch, torque converter, etc. When one turns, either one or
both of the other components must also turn, and at an RPM in direct
proportion to the sum of the other two.
Posted by Tomes on February 2, 2009, 3:58 am
"Mr. G" ...
Thanks for the explanation. I will consider all this and play with it a bit