Posted by Peter Granzeau on May 7, 2009, 10:15 pm
wrote:
>On Mon, 04 May 2009 23:46:58 -0800, "David T. Johnson"
>>Tom Cole wrote:
>>> On Mon, 04 May 2009 17:11:19 -0700, "David T. Johnson"
>>>
>>> The only time the MG2 is solely in control is when reversing, although,
>>> even then I have experienced the ICE starting when extreme reversing
>>> power is needed (e.g. to get a stopped front wheel over an obstruction
>>> such as the kerb).
>>
>>No, the ICE is completely unable to supply power to the wheels when
>>reversing because the ICE, like all gasoline engines and unlike MG2,
>>only rotates in one direction...and there is no 'reverse' gearbox on a
>>Prius. The ICE is only charging the battery if it is running while
>>you are reversing so in reverse, the Prius is electric drive only.
>I agree that it seems illogical that the ICE should be needed when
>reversing under full power, yet the ICE *does* start under these
>conditions on my 05 Prius and also on my wife's 03 Prius, even when they
>are in EV mode. We reverse into our garages and if the approach is
>misjudged such that the front wheels are stopped at the kerb, applying
>full accelerator to get over the steep bump will cause the car to come
>out of EV mode and the ICE to start.
>I have also experienced this when reversing up steep driveways in EV
>mode.
What I have read says that the Prius reverses on electric power alone
(and, with no transmission other than the power split device, that seems
logical). The engine may turn on for many unconnected reasons, such as
recharging the traction battery, maintaining engine temperature, and the
like, but there is no reverse _gear_.
Posted by Was Istoben on May 7, 2009, 10:33 pm
> wrote:
>>On Mon, 04 May 2009 23:46:58 -0800, "David T. Johnson"
>>
>>>Tom Cole wrote:
>>>> On Mon, 04 May 2009 17:11:19 -0700, "David T. Johnson"
>>>>
>>>> The only time the MG2 is solely in control is when reversing, although,
>>>> even then I have experienced the ICE starting when extreme reversing
>>>> power is needed (e.g. to get a stopped front wheel over an obstruction
>>>> such as the kerb).
>>>
>>>No, the ICE is completely unable to supply power to the wheels when
>>>reversing because the ICE, like all gasoline engines and unlike MG2,
>>>only rotates in one direction...and there is no 'reverse' gearbox on a
>>>Prius. The ICE is only charging the battery if it is running while
>>>you are reversing so in reverse, the Prius is electric drive only.
>>
>>I agree that it seems illogical that the ICE should be needed when
>>reversing under full power, yet the ICE *does* start under these
>>conditions on my 05 Prius and also on my wife's 03 Prius, even when they
>>are in EV mode. We reverse into our garages and if the approach is
>>misjudged such that the front wheels are stopped at the kerb, applying
>>full accelerator to get over the steep bump will cause the car to come
>>out of EV mode and the ICE to start.
>>
>>I have also experienced this when reversing up steep driveways in EV
>>mode.
> What I have read says that the Prius reverses on electric power alone
> (and, with no transmission other than the power split device, that seems
> logical). The engine may turn on for many unconnected reasons, such as
> recharging the traction battery, maintaining engine temperature, and the
> like, but there is no reverse _gear_.
Is there a forward gear?
Posted by David T. Johnson on May 7, 2009, 10:35 pm
Tom Cole wrote:
>
> I agree that it seems illogical that the ICE should be needed when
> reversing under full power, yet the ICE *does* start under these
> conditions on my 05 Prius and also on my wife's 03 Prius, even when they
> are in EV mode. We reverse into our garages and if the approach is
> misjudged such that the front wheels are stopped at the kerb, applying
> full accelerator to get over the steep bump will cause the car to come
> out of EV mode and the ICE to start.
>
> I have also experienced this when reversing up steep driveways in EV
> mode.
The MG2 electric motor is the only device that powers the wheels when
reversing. If the ICE starts, it is doing so to charge the battery but
it cannot directly supply to the wheels in reverse but it CAN do that in
the forward direction, as long as MG2 is also turning. If your
reversing requires more power than is available in the battery, the ICE
will start to charge the battery which then supplies battery current to
MG2 to maintain the reversing. The ICE can't directly power the wheels
in reverse because the ICE (like every ICE) only rotates in one
direction. It would take a 'reverse' gear box to translate the ICE
'forward' rotational direction into the reverse direction...and such a
gearbox does not exist on the Prius...which also does not have a
'transmission' to power the vehicle forward with different 'gears' since
the MG2 can supply the necessary torque for slower speeds without the
need for gears.
--
Posted with OS/2 Warp 4.52
and Sea Monkey 1.5a
Posted by Was Istoben on May 7, 2009, 10:40 pm
The ICE can't directly power the wheels
> in reverse because the ICE (like every ICE) only rotates in one direction.
The Prius ICE only rotates in one direction however this behavior is not
universal. Some internal combustion engines will run in whatever direction
they are started. A good example of this is found in model airplane
engines.
Posted by Mike Rosenberg on May 7, 2009, 10:44 pm
> The Prius ICE only rotates in one direction however this behavior is not
> universal. Some internal combustion engines will run in whatever direction
> they are started. A good example of this is found in model airplane
> engines.
I believe that, in general, two-stroke ICEs can in either direction
while four-stroke ICEs can run in only one.
--
My Blog, Mike's Musings <http://blog.macconsult.com>
Mac and geek T-shirts & gifts <http://designsbymike.net/shop/mac.cgi>
Prius shirts/bumper stickers <http://designsbymike.net/shop/prius.cgi>
>>Tom Cole wrote:
>>> On Mon, 04 May 2009 17:11:19 -0700, "David T. Johnson"
>>>
>>> The only time the MG2 is solely in control is when reversing, although,
>>> even then I have experienced the ICE starting when extreme reversing
>>> power is needed (e.g. to get a stopped front wheel over an obstruction
>>> such as the kerb).
>>
>>No, the ICE is completely unable to supply power to the wheels when
>>reversing because the ICE, like all gasoline engines and unlike MG2,
>>only rotates in one direction...and there is no 'reverse' gearbox on a
>>Prius. The ICE is only charging the battery if it is running while
>>you are reversing so in reverse, the Prius is electric drive only.
>I agree that it seems illogical that the ICE should be needed when
>reversing under full power, yet the ICE *does* start under these
>conditions on my 05 Prius and also on my wife's 03 Prius, even when they
>are in EV mode. We reverse into our garages and if the approach is
>misjudged such that the front wheels are stopped at the kerb, applying
>full accelerator to get over the steep bump will cause the car to come
>out of EV mode and the ICE to start.
>I have also experienced this when reversing up steep driveways in EV
>mode.