Neutral "N" operation - gas pedal command negated?

[pakitt]

There has been a huge debate about what one can do on a Prius in the very unlikely event that the accelerator pedal gets stuck or receives a wrong command from the computer (a lot more hereToyota's runaway car worries may not stop...).
So I tested what happens when "N" mode is selected.
First of all, the fastest way to insert N mode, is to press the P button or set reverse "R" mode. If you shift the lever too quickly in N and don't keep it there for a few seconds, it will *not* shift into N.
And I think there is a good reason not to shift immediately in N at speed when selecting it with the lever: when in N, not only the engine "idles" or whatever it does to simulate neutral, but the accelerator does not work anymore - try it - nothing happens, no revving, nothing. So if you are, say, overtaking or in an emergency when you need acceleration and accidentally N is selected immediately, something could happen due to complete loss of power to the wheels. This should not happen.

BTW: N is simulated, you read right: there is no clutch or hydraulic transmission/clutch in a Prius - the wheels are permanently connected to the drivetrain via the electric motor and the planetary gear system, called also Power Split Device (PSD). Which means, unless someone knows otherwise, if the computer has decided that you cannot switch into N, you're out of luck. The same goes with the on/off switch. If the computer decides that after 3 secs of pressing the switch when at speed, you are not turning off the engine, you are *not* turning it off. There is no mechanical way to turn the car off.....

I have also noticed that the brake pedal does not negate the accelerator pedal signal: the accelerator does get disconnected instead as mentioned when you are in N. Why?!?!? what is the reason to accelerate and brake at the same time on this car?

Try pressing the brake and accelerator pedal with standing - the engine at the beginning is quiet, then the ICE kicks in and the only thing it can do is re-charge the battery....but as soon as you leave the brakes the car move (abruptly) forward. Try it somewhere safe with nobody around!!! The same happens when driving at speed - if you press the accelerator full throttle while braking, the accelerator command will not be negated.
There is a *but*, though - because the engine is not *directly* connected to the wheels, rather it exchanges torque with the generator and the motor, when both gas and brake pedal are pressed, the motor will be forced to slow down, so the only way for the engine to give torque to "something" is via the generator to create electricity to charge the batteries - this is the only thing that I can imagine myself as close as to the buffering effect of the clutch in a normal car.

I never understood one thing though - when the battery is completely charged, what happens if the ICE is forced to continue to run (stuck accelerator pedal, going downhill, etc?) - is the generator disconnected? what happens at the connection? what voltage will be built up and how does the rotational energy of the generator get dissipated?
Also - why does the Prius need to crawl when in D since there is no clutch or hydraulic connection to the PSD? why does the car simply stand still in D if no gas is given? why does it have to behave like a '70s automatic gearshift car????

[spiderman]

Originally Posted by pakitt

I have also noticed that the brake pedal does not negate the accelerator pedal signal: the accelerator does get disconnected instead as mentioned when you are in N. Why?!?!? what is the reason to accelerate and brake at the same time on this car?

As to why for this point, I use the brakes and the accelerator at the same time to clean the rotors of water after I wash the car to keep the rotors from rusting.

[pakitt]

Originally Posted by spiderman

As to why for this point, I use the brakes and the accelerator at the same time to clean the rotors of water after I wash the car to keep the rotors from rusting.

Sorry, for "rotors" which part of the car you mean? I don't understand.
Do you mean the brake blades? (not the pads)
What does "rotors" indicate mechanically speaking for a car, in the US?

[hobbit]

Go to my linkfarm and search for "edocket", and chase that link.
It explains the rationale for "creep". You can cancel it with
judicious use of "N"; I do that all the time when just arriving
at a standstill at stops.
.
_H*

[rachaelseven]

Originally Posted by pakitt

Sorry, for "rotors" which part of the car you mean? I don't understand.
Do you mean the brake blades? (not the pads)
What does "rotors" indicate mechanically speaking for a car, in the US?

In the US, the 'rotor' is the flat metal plate in the braking system that is grabbed by the pads when the brakes are applied.

[spiderman]

Originally Posted by pakitt

Sorry, for "rotors" which part of the car you mean? I don't understand.
Do you mean the brake blades? (not the pads)
What does "rotors" indicate mechanically speaking for a car, in the US?

Yes, the rotors are the metal between the brake pads... here is something I googled up real quick to explain. Sorry I didn't notice you are from Deutschland.

[pakitt]

Originally Posted by hobbit

Go to my linkfarm and search for "edocket", and chase that link.
It explains the rationale for "creep". You can cancel it with
judicious use of "N"; I do that all the time when just arriving
at a standstill at stops.
.
_H*

Found it - thanks - I read it a bit, essentially the "creeping" is to remind the driver in which gear it is.
Then 4 comments:
- the standard continuous beep in the Prius 2010 when in reverse is completely useless from the law point of view - since creeping is already showing the driver the direction of movement
- the creep is a simulation to abide to US regulation to show the direction of the selected gear and avoid false direction by inadvertedly selecting the wrong gear
- who knows what the regulation is in EU??? and especially in Germany, where I live...
- since I have driven all my life a manual (very seldom and very briefly automatically - essentially when visiting the US), the use of the clutch was the equivalent of letting the car creep when releasing the brake pedal on an automatic - the only major difference being that in manual you can have the car at a standstill with a gear inserted by completely depressing the clutch pedal when the engine is idling: and this is likely what unsettles me still - I am not used of having the car creep when standing on a flat surface with the engine OFF! and needing to press the brake pedal all the time when at a traffic light

I would use N as you mention, but there are 2 points:
1) it defeats, at least for me, the benefits of automatic
2) Toyota strongly advises not to use N regularly as the batteries can be drained - and this is because to simulate N, the generator needs to rotate in the opposite way of the ICE to nil its torque...or? something like that....

My father owns a Honda Jazz with CVT, and I was never bother with the creep and the continuous braking - and I think the reason being that you hear an engine running all the time that reminds you that something can happen if you release the brake, even without using the gas - Toyota had to comply to this regulation and even if everything is silent and no engine is moving, it has to simulate the creeping nevertheless....

[pakitt]

Originally Posted by spiderman

Yes, the rotors are the metal between the brake pads... here is something I googled up real quick to explain. Sorry I didn't notice you are from Deutschland.

Thanks - I though so - for me "rotors" are simply the inside rotating part of an electrical engine, with the external part being still called "stator" (I think that is the name in english).

Well in my old car, I would pull the hand brake a bit, drive slowly (20-30km/h) for a while to prevent the rusting - normal braking usually did a good job for the front brakes but no the rear ones.

In the Prius the issue is that the pedal brake, as far as I know controls only the rear brakes, and therefore for the front brakes, used *way* less than in a normal car (since there is the regenerative braking action of the electrical motor), the brake+gas pedal would achieve the same purpose. Still I don't think this is a good reason to keep this - especially at high speeds...

[dogfriend]

Carolyn gives demonstrations on the three different methods to override a "unintended acceleration" event:

Luscious Garage | Blog | Floor mat anxiety? LG TV investigates…

[fuzzy1]

Originally Posted by pakitt

Thanks - I though so - for me "rotors" are simply the inside rotating part of an electrical engine, with the external part being still called "stator" (I think that is the name in english). ...

Those are the correct English words for electric motor parts. But 'rotor' is also for parts of many machines other than electric motors.