Neutral

<div class='quotetop'>QUOTE(NTB @ Jul 11 2007, 07:28 PM) [snapback]477272[/snapback]</div>

I don't know all the technical specifics, but my gut feeling is to advise you against it. In general, this is not a good idea on any car with automatic transmission. Unless the transmission has a rear oil pump, it is starved of lubrication while coasting in Neutral.

I am not sure if that is the case with Prius, but since they warn not to tow it with all four wheels on the ground, it seem logical to realize that coasting in neural is pretty much the same thing.

The car is designed to get the best economy for the typical driver while coasting in Drive.

You should avoid using B (engine braking) on dowhill too, because that defeats regenerative braking. Use B only for extremely steep downhill where friction brakes come into play to the point you think they could onerheat. I haven't found any hill yet where I had to worry about that.

 

Nope.

You need to glide.

Take your foot off of the gas and wait for the MFD to show green arrows. Then lightly touch the gas until it disengages the regen. You'll either see the arrows disappear, or be replaced with orange. Either way, your display will go 99.9 mpg. That's what you want.

No need to play with the stick. Drive will do you just fine.

 

The thing is it's not always easy to do that, especially when your car is warming up. Sometimes it may take a while to get into that "glide" mode so by the time you do you already need to accelerate.

 

<div class='quotetop'>QUOTE(Alexstarfire @ Jul 12 2007, 12:04 AM) [snapback]477349[/snapback]</div>

Then you let the car warm up.

And you accelerate when you need to.

You learn to drive the car in "Drive".

 

<div class='quotetop'>QUOTE(NTB @ Jul 11 2007, 09:28 PM) [snapback]477272[/snapback]</div>

First off, "N" does not risk the vehicle except in one case, coasting down a grade starting with the ICE off and rolling faster than 42 mph. In this unique situation, the ICE would normally be started and run but in "N", the ICE won't run and MG1 will wind up spinning faster and faster. Toyota reports the NHW20, 2004-current, has a maximum MG1 rpm of 10,000 rpm. The NHW11 is reported to have a 6,500 rpm MG1 limit but we already know it can go to 8,500 rpm in "P" with the accelerator maxed.

If you are already above 42 mph, "N" is vehicle safe at any speed. If you stay below 42 mph, "N" is vehicle safe. It is only starting below 42 mph with the ICE off and rolling down a hill and exceeding 42 mph that you'll be violating existing control laws.

The transaxle oil pump is operated by the ICE.

Bob Wilson

 

Just to play devil's advocate a little here, I've had my own NHW20
in "warp neutral" fairly often -- into the mid fifties, even, and
as a test I once had it up to about 68 on a big downhill with the
engine stone cold stopped and MG1 howlin' away at 10 grand or over.
Air resistance kept me from going any faster, as probably did the
windage around MG1 and MG2 themselves down there in the transaxle.
But mild episodes of warp-neutral to carry one through little dips
and valleys without spinning the extra metal of the engine is pretty
harmless.
.
_H*

 

<div class='quotetop'>QUOTE(hobbit @ Jul 12 2007, 12:05 AM) [snapback]477381[/snapback]</div>

How can you make this claim that it is harmless? Have you done a comparison at high mileage between two Prii, one run with multiple instances of warp neutral, and another high mileage control car that has not been abused that way? What if latent damage from the warp neutral doesn't take it's tole until 160,000 miles? Why risk it? What is the point?

If what you say is true, than why does Toyota recommend not towing the car on all four wheels? What is the difference? Oh, you should be able to tow in warp neutral, as long as it is only done ocasionally! Mostly up to 42, but sometimes it is OK to tow it at 50, and you can even go 68 if you must.

 

<div class='quotetop'>QUOTE(hobbit @ Jul 12 2007, 02:05 AM) [snapback]477381[/snapback]</div>

Yes I have some short distances, say 1/2 mile which I know I will have to stop or slow right down and it seems ashame to add that extra drag for just 10-20secs, I limit it to about 50mph for short periods.

 

<div class='quotetop'>QUOTE(hobbit @ Jul 12 2007, 02:05 AM) [snapback]477381[/snapback]</div>

Yes I have some short distances, say 1/2 mile which I know I will have to stop or slow right down and it seems ashame to add that extra drag for just 10-20secs, I limit it to about 50mph for short periods.

 

Trust me, if it was really a problem, Toyota would have chosen one
of those very rare instances when they actually override the definition
of Neutral and manage the motors -- in this case to exert torque and
get the engine started.
.
_H*

 

What hasn't been done, yet, is testing to destruction. We don't know if the mechanical limit of MG1 nor the electrical risks of a rapidly spinning MG1. Just be aware of the control law and make an informed decision.

I kinda wish the Dept. of Energy testers had used their test rig to find out how fast MG1 can spin before the parts or smoke escapes.

Bob Wilson

 

While it's not particularly relevant to the technical discussion, it's worth pointing out that, in many states, driving in neutral is illegal.

 

Right, the whole "neutral illegal" hairball has been hashed to death
in numerous other threads and you ought to know my take on it by now.
.
_H*

 

<div class='quotetop'>QUOTE(hobbit @ Jul 12 2007, 06:50 PM) [snapback]477804[/snapback]</div>

Well, I don't want to open a can of worms or anything, but is your take that you don't think it's illegal or that you have some opinion about whether or not it should be illegal? If the latter, then I'm sure there are reasonable points on either side of the argument (and don't have a great desire to start that argument). If the former, than I can probably find some documentation that suggests that it is illegal (at least in some states), if you care.

 

How long in neutral (NHW20) with the air conditioning on will the HV battery last before something happening?

What happens?

(With the battery unable to supply the voltage needed and the M/Gs isolated, what keeps the voltage up? or does it not stay up?)

 

<div class='quotetop'>QUOTE(NTB @ Jul 12 2007, 04:40 PM) [snapback]477736[/snapback]</div>

The normal definition of a 'glide' is electrical energy neutral but the energy consumption display has a range of current values when showing no energy flow. It is close but without instrumentation, a challenge. However, "N" is entirely free of MG1/MG2 current flow. When I do P&G benchmarks, I use "N" to ensure a ballistics glide and reproducible results.

There is a mechanical connection from the ICE shaft to the transaxle oil pump. If the ICE rotates, the pump is moving oil.

We know "N" prevents HV current flowing into or out of MG1 and MG2. The 12 VDC circuits continue to work including drawing power from the HV battery to sustain the systems. Any "protection" beyond that would be speculation or derived from the absence of current.

Bob Wilson