High speed in N (and ICE @ 0 RPM)

[RolfS]

Nothing will happen, by driving the car in neutral while going down a hill no matter how fast you go. I don’t know why everyone keeps getting this wrong. I have posted this information in the past and everyone keeps getting it wrong, still. Its like an urban legend.

The computer software is designed to take care of the car to prevent it from being destroyed. It is all written up in the 2004 Prius New Car document.

What is dumb about going down the hill in neutral is that you don’t regain any energy to charge the HD battery, because it shuts off all the output transistors that would normally charge the HD battery. So the SOC of the HD battery just decreases going down the hill.

The software will take it out of neutral automatically, without you knowing, under the following conditions:

1. When breaking: it takes the car out of neutral. This is hidden from you and the car as far as you are concerned is still in neutral.

2. When the speed of the car gets too fast it tuns on the engine to prevent MG1 from over revving.

There is another reason, but I can’t remember right now.

[efusco]

Originally Posted by RolfS

The software will take it out of neutral automatically, without you knowing, under the following conditions:

1. When breaking: it takes the car out of neutral. This is hidden from you and the car as far as you are concerned is still in neutral.

2. When the speed of the car gets too fast it tuns on the engine to prevent MG1 from over revving.

There is another reason, but I can’t remember right now.

You may have posted this before, but if so it was inaccurate then and still is now.

Those of us with the ability to monitor such things know that both of your points above are completely incorrect. When in neutral the engine can not start. And braking does not take the car out of neutral, this isn't hidden from anyone, it doesn't happen.

[The Tramp]

Originally Posted by efusco

You may have posted this before, but if so it was inaccurate then and still is now.

Oh yes. And I do so confirm.

There is no way that ICE turns ON when in N and MG1 is overrevving.

And when braking, there is no rigenerative charge, it's brake pads only.

[RolfS]

Originally Posted by efusco

You may have posted this before, but if so it was inaccurate then and still is now.

Those of us with the ability to monitor such things know that both of your points above are completely incorrect. When in neutral the engine can not start. And braking does not take the car out of neutral, this isn't hidden from anyone, it doesn't happen.

I was not wrong before either. I am not making this up. Here is a direct quote from the Toyota documentation. Look it up yourself:

On Page TH-5 (3. Hybrid Tansaxle)

Clutch-Less System

A clutch-less system has been adopted to mechanically link the front wheels and MG2 via gears and a chain. To disengage the motive force in the neutral position, the shift position sensor outputs an N position signal to turn OFF all the power transistors in the inverter (which connects MG1 and MG2). As a result, the operation of MG1 and MG2 shuts down, thus rendering the motive force at the wheels to zero. In this state, even if MG1 is rotated by the engine or MG2 is rotated by the drive wheels, no generation of electricity occurs because both MG1 and MG2 are inactive. As a result, the SOC (state of charge) of the HV battery decreases as the shift position remains in the “N” position.

On Page TH-46 (3. HV ECU Control)

Shut Down Control

Generally, MG1 and MG2 are shut down when the shift position is in the “N” position. This is because MG1 and MG2 must be stopped electrically as a means of shutting down the motive force, since MG2 is mechanically joined to the front wheels. However, the shut down function is canceled under the following exceptions:

· During driving, if the brake pedal is depressed and a wheel lock up, the ABS with EBD is activated. After rotation of the wheel. Even if the shift position is in the “N” position at this time, the shut down function is canceled to allow the wheel to rotate. After the wheel rotation has been restarted, the system resumes its shut down function.

· When the vehicle is driven in the “D” or “B” position and the brake pedal is depressed, the regenerative brake operates. At this time, as the driver moves the shift position to the “N” position, the brake hydraulic pressure increases while the request torque of the regenerative brake decreases gradually so as not to create a sluggish brake feel. After this, the system effects the shut down function.

· When MG1 and MG2 operate at higher speed than the specified level, the shut down function is canceled.

[efusco]

You're misinterpreting what you're reading.

[Patrick Wong]

Originally Posted by RolfS

...The software will take it out of neutral automatically, without you knowing, under the following conditions:

1. When breaking: it takes the car out of neutral. This is hidden from you and the car as far as you are concerned is still in neutral.

2. When the speed of the car gets too fast it tuns on the engine to prevent MG1 from over revving.

Hi Rolf,

Regarding #1 above: the car is taken out of neutral only to the extent that a wheel has locked up. If no wheel is slipping, then the system will return to N. See the last sentence of the first bulleted text in your quote below.

Regarding #2 above: I ask that the contributors to this string read the last bulleted text below.

Does anyone have instrumentation that shows MG1 RPM? If yes, has that individual allowed MG1 RPM to exceed 11K to see what would happen? (I had the Ecrostech scanner for my 2001 which did show MG1 RPM, but at that time I did not have the idea to put the car in N at high speeds...)

Originally Posted by RolfS

· During driving, if the brake pedal is depressed and a wheel lock up, the ABS with EBD is activated. After rotation of the wheel. Even if the shift position is in the “N” position at this time, the shut down function is canceled to allow the wheel to rotate. After the wheel rotation has been restarted, the system resumes its shut down function.
...
· When MG1 and MG2 operate at higher speed than the specified level, the shut down function is canceled.

[efusco]

Yes Patrick, I've briefly exceeded 10k rpm (not by much) as demonstrated w/CAN-View. NOTHING happened.

[Patrick Wong]

Originally Posted by efusco

Yes Patrick, I've briefly exceeded 10k rpm (not by much) as demonstrated w/CAN-View. NOTHING happened.

Hi Evan,

OK, if the MG1 speed limit is supposed to be 6K RPM and you got MG1 above 10K RPM, then it would appear that the NCF text is not correct. This wouldn't be the first time that the text was found to be inaccurate...

[efusco]

Originally Posted by Patrick Wong

Hi Evan,

OK, if the MG1 speed limit is supposed to be 6K RPM and you got MG1 above 10K RPM, then it would appear that the NCF text is not correct. This wouldn't be the first time that the text was found to be inaccurate...

MG1 limit is 10k RPM in the Prius II...I did not exceed 10k for long or by very much, so there may be a 'fudge factor'/safety margin built in, but I don't think so.

[DaveinOlyWA]

Originally Posted by The Tramp

Oh yes. And I do so confirm.

There is no way that ICE turns ON when in N and MG1 is overrevving.

And when braking, there is no rigenerative charge, it's brake pads only.

if what u say is true, why can t the Prius be towed?

it specifically states you must flatbed it