What'd happen if you press the P while you drive?

One possible problem with shifting to N while driving is that the ICE will still be running but with no load. If it's suffering from the uncontrolled acceleration at that time, it could rev up to dangerous levels.

If it happens to me, I think I'll be trying the "hold the power (on/off) button for three seconds" while stepping on both the regular and parking brakes.

 

ICE speed is controlled by the ECU. If the control system is so messed up that the ICE is out of control, it's not likely that the Power switch is going to help. I would try it as plan B, but I wouldn't be hopeful.

Besides, all control issues aside, if it comes down saving my engine or saving my life, I think I'll let the engine take the dive.

Tom

 

After reading all the material in this thread about stopping your "runaway prius" I have decided maybe the P button should stand for "Panic" as well as park.LOL

 

To anybody who was not sure about hitting the P button to stop the car....

I went to an abandoned airfield (I'm a weenie like that) and drove my prius full throttle and hit P at about 80mph. The car immediatley went into neutral.

There was none of this......

 

Cool, that makes sense!!! no wonder it's called "Power" button (means more Power).

 

Wait a minute....Pardon my lack of engineering knowledge....I was to understand the Traction Motor is A/C...hence the need for an Inverter.....so how would moving in reverse cause voltage spike?

 

I have wondered about this myself.

1. Why is the Park condition not selectable on the shift lever?

2. Why Park given a separate botton larger than the Power button?

3. You don't even have to use the park button when turning off the car,
you can just use the Power button.

It would seem that the Park button has been given a special
prominence. Which for such a mundane purpose makes little sense.

However, as a Park/PANIC button, it makes a lot of sense.

 

The traction motor, MG2, is a hybrid synchronous A/C motor. The hybrid part means that it runs as both a permanent magnet motor *and* as an induction motor at higher levels.

All motors are really AC. The field driving a motor must have a time varying component for the motor to rotate. This time varying component comes from time varying electricity, or AC. To run a motor from DC, you have to turn the DC into some form of AC. DC motors do this internally, sometimes through mechanical commutators, sometimes through electronics (brushless motors).

With big DC motors, the commutating electronics are moved to a separate box. This box is called the inverter. The inverter changes DC electricity into properly formed AC to drive the motor as required.

As for electrical spikes, all motors will also work as generators. Spinning MG2 creates voltages that are back coupled to the inverter. If these voltage spikes are too large or fast they could possibly damage the electronics in the inverter.

Tom

 

A poorly written manual is no excuse for not understanding how the vehicle operates. For the driver's own safety, one should read and understand the manual fully - and if not seek additional resources (like Prius chat).

Any way, you'll find the same warnings on any car. Shifting into R or P while vehicle is in motion may severely damage the gears. Shifting into N ("coasting") can be illegal in certain states due simply to the fact that you cannot accelerate in an emergency (even though this is often the most efficient manner of traveling down a hill).

Nevertheless, the manual did not say to never shift to N while driving - it merely warns one of the danger of an accident. When the engine is racing inappropriately, one should realize simply by virtue of how the transmission works that N would be advantageous.

 

I guess if your Prius was still under warranty, you might want to try it just to see what happens. Also read this little blurb..for more light on the situation. Why so little mention of Neutral in ?Unintended Acceleration?? - Car News - Road and Track

 

I use the park button when I want to sit in the car & listen to the radio, or keep the climate control working, so it is not a useless button.
Of course, if there is some sort of communication failure between the processors, acceleration could occur, and the park, or even power buttons may not work as expected. Anybody willing to short the can bus while driving?