Posted by Michael Pardee on February 2, 2009, 12:46 pm
> From the simulation, it looks like the MG1 generator will overspeed above
> its 6500 rpm max if the vehicle speed is above 42 mph and the red engine
> crankshaft doesn't start turning so perhaps that is the 'speed limit' that
> requires the gas engine to start up above 42 mph. As Mr. G pointed out,
> the MG1 could be used to turn the gas engine crankshaft but more likely is
> that Jungle Motors is electric-only below 42 mph but not above that
> speed.
> --
> Posted with OS/2 Warp 4.52
> and Sea Monkey 1.5a
FWIW, a few regulars in the Yahoo! Prius_Technical_Stuff forum have reported
seeing (on a Scanguage) the ICE not turning at speeds somewhat above 42 mph
and MG1 above the putative redline, even in a stock Classic Prius. There has
been speculation the redline may be for the inverter when MG1 is being used
for a motor rather than for a generator.
The 6500 rpm limit was for the Classic (NHW11), while in the NHW20 the limit
is supposed to be 10,000 rpm. Says JerryW: "MG1 would not be exceeding its
rev range until well over 70mph. I don't think we know why the ICE still
starts up at 42mph now. I don't, anyway.."
Mike
Posted by Peter Granzeau on February 2, 2009, 9:24 pm
wrote:
>>
>> From the simulation, it looks like the MG1 generator will overspeed above
>> its 6500 rpm max if the vehicle speed is above 42 mph and the red engine
>> crankshaft doesn't start turning so perhaps that is the 'speed limit' that
>> requires the gas engine to start up above 42 mph. As Mr. G pointed out,
>> the MG1 could be used to turn the gas engine crankshaft but more likely is
>> that Jungle Motors is electric-only below 42 mph but not above that
>> speed.
>> --
>> Posted with OS/2 Warp 4.52
>> and Sea Monkey 1.5a
>>
>FWIW, a few regulars in the Yahoo! Prius_Technical_Stuff forum have reported
>seeing (on a Scanguage) the ICE not turning at speeds somewhat above 42 mph
>and MG1 above the putative redline, even in a stock Classic Prius. There has
>been speculation the redline may be for the inverter when MG1 is being used
>for a motor rather than for a generator.
>The 6500 rpm limit was for the Classic (NHW11), while in the NHW20 the limit
>is supposed to be 10,000 rpm. Says JerryW: "MG1 would not be exceeding its
>rev range until well over 70mph. I don't think we know why the ICE still
>starts up at 42mph now. I don't, anyway.."
It seems that individual Prius act differently. Mine almost always runs
the ICE any time the battery status indicator shows blue bars, and will
only cruise on battery if the indicator is showing green. I have
managed about 40 mph on battery only when the load was light (gentle
downhill slope); straight and level (or as near as it gets--I live in
tidewater country, and there are still often gentle grades on streets
and highways.)
Posted by Mr. G on February 3, 2009, 4:30 am
(pgranzeau@cox.net) says...
> It seems that individual Prius act differently. Mine almost always runs
> the ICE any time the battery status indicator shows blue bars, and will
> only cruise on battery if the indicator is showing green. I have
> managed about 40 mph on battery only when the load was light (gentle
> downhill slope); straight and level (or as near as it gets--I live in
> tidewater country, and there are still often gentle grades on streets
> and highways.)
The ECU in the Prius will 'learn' your individual driving habits and
modify its parameters accordingly. I don't know enough about exactly
how it does that to explain the situation you described, though possibly
based on your driving habits there are often situations where the
battery will discharge rapidly, so it attempts to top it off whenever
possible. In my '07 I have no problem driving for long stretches with
the ICE off. My MFD battery display is often showing blue, though
rarely goes below half the bars showing.
Posted by Tomes on February 3, 2009, 10:40 pm
> (pgranzeau@cox.net) says...
>> It seems that individual Prius act differently. Mine almost always runs
>> the ICE any time the battery status indicator shows blue bars, and will
>> only cruise on battery if the indicator is showing green. I have
>> managed about 40 mph on battery only when the load was light (gentle
>> downhill slope); straight and level (or as near as it gets--I live in
>> tidewater country, and there are still often gentle grades on streets
>> and highways.)
> The ECU in the Prius will 'learn' your individual driving habits and
> modify its parameters accordingly. I don't know enough about exactly
> how it does that to explain the situation you described, though possibly
> based on your driving habits there are often situations where the
> battery will discharge rapidly, so it attempts to top it off whenever
> possible. In my '07 I have no problem driving for long stretches with
> the ICE off. My MFD battery display is often showing blue, though
> rarely goes below half the bars showing.
Mine too. Which is why I really wish that it would use the electrics moreso
than it does now.
Tomes
Posted by Mr. G on January 29, 2009, 10:47 pm
T. Johnson (djohnson@isomedia.com) says...
> Your understanding is wrong. The gasoline motor on the current Prius
> starts if the speed is above 42 mph but the electric motor also
> continues to operate. There is no physical limitation...it's just an
> optimization programmed into the system by Toyota based on the current
> battery and motor capacity. Similarly, the gasoline motor never runs
> below 1,000 rpm not because of any physical limitation (the motor would
> run just fine at 500 rpm) but because it's an optimization. The whole
> point of the system is to maximum efficiency.
The ICE and electric motors are not just multiple inputs to the drive
system; the way it is designed, the speed of one directly affects the
speed of another.
The planetary gear system is basically the same thing as the
differential on a rear-wheel drive car. In that scenario, the input to
the differential is the drive shaft, the the two outputs are the right
and left drive wheels. Turning the driveshaft causes both wheels to
move forward, but if one wheel is slowed down, the other will speed up,
so that their combined RPM is equal for any given input RPM.
In the synergy drive, the driveshaft is now the output shaft, one wheel
is replaced by MG2, and the other side has the ICE & MG1. With this
arrangement, the speed of the output shaft is the COMBINED speed of the
ICE/MG1 + MG2.
To make things simple for illustration, assume the planetary gears have
a 1:1 ratio. (the numbers are purely fictitious, and are only to
illustrate the concept.) To get a 100 RPM output speed, the ICE/MG1 and
MG2 must both be running at 100 RPM. If the ICE/MG1 is increased to 200
RPM, then MG2 must be at 50 RPM. If MG2 is at 200 RPM, then the ICE/MG1
would reduce to 50 RPM. In actual use, the ICE/MG1 is spun at its most
efficient speed, and MG2 spins at whatever speed is required to give the
desired output speed. This includes spinning backwards if the required
output speed is slow, but the ICE/MG1 wants to run at a high RPM, such
as going slowly up a steep hill.
When the ICE/MG1 is not moving, then MG2 must spin much faster to
compensate, since it's providing all the RPM.
> its 6500 rpm max if the vehicle speed is above 42 mph and the red engine
> crankshaft doesn't start turning so perhaps that is the 'speed limit' that
> requires the gas engine to start up above 42 mph. As Mr. G pointed out,
> the MG1 could be used to turn the gas engine crankshaft but more likely is
> that Jungle Motors is electric-only below 42 mph but not above that
> speed.
> --
> Posted with OS/2 Warp 4.52
> and Sea Monkey 1.5a