Still confused about Neutral

I can only answer one of your questions. I had ICE spinning, traveling greater than 42mph, shift to N. Then I brake and speed dropped below 42mph, at that point, ICE is still spinning. But I don't know if any fuel is being used. I did that because there's a steep hill on my commute. I like to dry up and clean the rust off my brakes after rain on the downhill.

I will set up the CAN-View screen after work and try to find the answers to your other questions.

 

The simple answer that's still sort of a non-answer is that because there are no "different gears" then at least 2 of the 3 motors is always spinning when you're in motion. My guess would be that neutral is just a mode where the computer allows the ICE to spin, but not to affect your wheel speed, and that normal start and stop of the ICE would still apply.

Since you can rev the engine in Neutral (actually... can you?) and also roll around, then speed of all 3 parts is still variable.

I'd like to know the CAN-view result as well.

 

My observation is as follows..
<div class='quotetop'>QUOTE(climateguy @ Sep 1 2006, 05:22 AM) [snapback]312365[/snapback]</div>

correct.

The ICE won't start exceeding the 42 mph barrier, and the vehicle speed was increased without ICE spinning.
I shifted to D to stop testing at 75 km/h (47 mph), and the ICE started consuming 1 cc of fuel, then it went to fuel cut mode.

Correct. In N, the fuel was continuously consumed. Fuel-cut mode in D.

I never try this. But, my bet is status does not change in N, so ICE contunues to spin consuming fuel.

Please note that the CAN-View is not perfect, especially about a little mount of fuel usage.

Ken@Japan

 

Hm, My Husband, who is still a novice when it comes to the Prius, accidentally shifted to Neutral when he meant to shift to Drive after being in B, when we were coming off the Grapevine (read Very Steep Hill) on I-5 going North. The car didn't complain or do anything weird. We were probably going 75 mph. I noticed that the Screen was showing No Engine being used (weird, but we were still on a grade and the battery was FULL). I couldn't easily see the Gear Selector panel from the passenger seat. We finally noticed the problem when we were coming off the highway about 3 miles after the shift and there was No Power from any engine, gas or electric.
At that point I finally looked over and noticed we were in N and talked my husband into putting the car in D and the engines suddenly sprang to life.
As near as I can tell, No Motor seemed to be running while we were in N. Not even the ICE. But then again, it had been doing Engine Braking with No Gas Usage for a couple of miles before we had gone into N. YMMV.

Lisa

 

BTW Ken did a good job explaining this. I will add a tiny bit.

1) The car is going less than 42mph, is switched into neutral, and maintains a speed of less than 42mph (slight downhill, flat, or uphill). I would assume that in this instance the ICE does not turn over at all, as overspinning MG1 is not an issue. Correct?
You have got it!

2) The car is going less than 42mph, is switched into neutral, and accelerates to a speed greater than 42mph (steep downhill). Again, I would assume the ICE is initially not turning over while the speed is less than 42mph. I've read a couple of posts that allude to the engine still not turning over even after the speed exceeds 42mph, in which case MG1 could be overspun. Can anyone verify this?
Yes the ICE has to spin at over ~42 mph. That does not mean the injectors or spark is engaged. Remember all these "gears" are fixed to one another. I have not observed fuel usage under these conditions. Remember the CAN View gets its information 2 ways by passively observing the data on the CAN Buss and by querying the ECU's for information. The latter is slower and suffers from lag. Off hand a lot of that is the temp data from the MG1, MG2. A lot is going on.

3) The car is going greater than 42mph, is switched into neutral, and maintains a speed greater than 42mph (slight to steep downhill). It's my understanding that the ICE will continue to spin in this case. Is this correct? Is fuel being supplied to the ICE at this time, or is it just spinning? My experience with the CAN-View is no. Initial fuel consumption then to 0 flow. Ken has another system.

4) The car is going greater than 42mph, is switched into neutral, and decelarates to a speed less than 42mph (slight downhill to uphill). As in (3), is the ICE initially spinning? Fuel being supplied? Does the ICE stop spinning once the speed is less than 42mph?
Fuel being supplied on a down hill I would say no but the route I go I rarely get above 43 mph and only briefly get above 42 when I don't take my foot off the gas in time to engage the MG2 breaking function. In an down hill then to up hill the Ice does not appear to use fuel.

Remember there are a number of different ways to monitor the system. Hobbit is the analog mavin and observers the elephant from a different place than I do or Ken does. We are all blind men feeling what we can of that huge beast and reporting observations. Sooner or later we will have a compleat description, then Toyota will change it all. More fun!
TIA for any help you can provide. Also, it would be great if you could include some indication of your confidence in your answers, i.e. is it just wild speculation, do you have CAN-view and from that you think you understand what's going on, you have CAN-view and it's obvious what's going on, you read it in a service manual, etc. Not that there's anything wrong with guessing...it's just nice to be able to distinguish what's known from what's believed.

 

Ok... just want to post my findings with CAN-View. I got my Prius into Stage 4 (refer to Five stages of Prius Operation) and try different conditions.

1) Accelerate with ICE, shift to N under 42mph.

ICE stayed spinning around 1000RPM. From CAN-View, it shows no fuel usage. Ken is right about CAN-View is not perfect. So there might be fuel being consumed, but it's insignificant.

2) Over 42mph, ICE spinning, shift to N and let car decelerate to under 42mph.

Again, ICE stayed spinning around 1000RPM. CAN-View shows no fuel usage.

Traffic didn't allow me to test other conditions.

My assumption is that if ICE is spinning when you shift to N, it will stay spinning. Small amount of fuel is being consumed, but not enough to register on CAN-View.

 

Good information, thanks all. I hadn't seen the "stages" thing before and that really helps in my understanding, especially why the car shudders to a stop early in drives sometimes, but stops smoothly others.

I got a good laugh from "golf cart mode", and fell off my chair at "super golf cart mode" I guess "stealth" and "warp-stealth" sound cooler, but the golf cart analogy is funnier.

 

<div class='quotetop'>QUOTE(climateguy @ Sep 1 2006, 12:32 PM) [snapback]312793[/snapback]</div>

At Stage 4, once I lift my foot off the pedal, ICE will be off. If I shift to N at that point, ICE will remain off. What I did was accelecrate with ICE, while ICE is still spinning, shift to N. So yeah, if it's on, it will stay on. And.. you are welcome

<div class='quotetop'>QUOTE(climateguy @ Sep 1 2006, 12:32 PM) [snapback]312793[/snapback]</div>

Hm... this one is tricky. My tests implies that ICE will stay on if it's on, then can we say ICE will stay off if it's off? If we are in N, ICE off, and speed up to over 42mph, I THINK ICE will remain off. I will try to test this if I get a chance.

<div class='quotetop'>QUOTE(Ichabod @ Sep 1 2006, 10:12 AM) [snapback]312703[/snapback]</div>

Hey, I agree with you! Even CAN-View will say "Stealth" when the car is in stealth mode. If it says "golf cart mode", I won't be showing off CAN-View to my friends.

Actually, when CAN-View display the word "Stealth" during stealth mode, my friend asked, "are we invisible now?!"

 

One thing is certain - in Neutral, the engine cannot start. Simply because the motors that could turn it over are isolated, that being the definition of "Neutral" for the Prius.

It may carry on idling if it was already running, but what is less certain is whether the system will allow the engine to stop. Normally the motors would be used to provide a smoother stop.

 

<div class='quotetop'>QUOTE(ScottY @ Sep 1 2006, 12:05 PM) [snapback]312804[/snapback]</div>

Saying "golf-cart mode" has never made any sense, since that is not how the hybrid system actually operates. I've always shrugged off the references like that, figuring whomever says it simply hasn't paid close enough attention to notice the difference. After all, subtle is the very nature of stealth.

But now, 6 years after having defined "stealth mode", the use of misleading terminology is becoming more than just annoying. It undermines the understanding of the more advanced designs, giving people the impression that all hybrids work the same way. So the feeling is turning into frustration.

Fortunately, the solution has been available since 1997. The Multi-Display clearly shows when electric-only operation is active, something neither an engine golf-cart nor a basic hybrid offer.

 

I'm still confused about neutral - is it an all motors off mode but still rotating?
Is there a mode where MG1 and MG2 are driving ICE is rotating but zero fuel? I think it's zone 4 see my prius>45mph thread

 

<div class='quotetop'>QUOTE(KMO @ Sep 2 2006, 04:34 PM) [snapback]312983[/snapback]</div>

Actually, only one motor, MG1, is responsible for starting/stopping the engine. MG2, being coupled to the wheels, cannot start/stop the engine.

I'm certain it will keep on idling in [N]. You can try this sometime. The car does not need to move. Put your foot firmly on the brake pedal and make sure the engine is running in [D], then shift to [N]. See it you can observe/feel the engine stop by itself in [N]. I bet you that it will continue to idle even though the engine is not needed for propulsion.

<div class='quotetop'>QUOTE(climateguy @ Sep 1 2006, 04:22 AM) [snapback]312365[/snapback]</div>

From my understanding, the magical 42mph speed is only enforced when both MG1/MG2 are controllable. If you shift to [N], both MGs are in open-circuit state so that limit does not apply anymore. It doesn't matter whether the speed is 42mph or 0mph, the engine cannot start if it is stopped and cannot stop if it is running. As for fuel consumption in idle rpm (~1000), it all depends on the torque demand to maintain it at that rpm. If you are going downhill, very little or no fuel may be required to maintain the idle rpm.

 

<div class='quotetop'>QUOTE(prius2go @ Sep 2 2006, 11:13 PM) [snapback]313037[/snapback]</div>

Yes. The ICE is consuming some fuel to idle in N at above 42 mph.

Yes. The MG1 is driving the ICE consuming about 1 kW in D at above 42 mph.

What is "zone 4"?

Ken@Japan

 

Y'all seem to have pretty much nailed it, all saying the same thing
in different ways... lemme see if I can summarize [or raise the noise
floor, depending on how you see it].
.
In Neutral, the ICE is not allowed to change *state*. Period. So
if it was spinning before shifting to N, it remains running; if it
was already shut down, it stays that way.
.
Corollary 1: if you're above 42 mph and the ICE is spinning but in
fuel cut [foot off accelerator], and you shift to N, it remains
spinning but now it has to idle and consume fuel to remain running.
.
Corollary 2: if you're below 42 mph and the ICE is shut down and you
shift to N and begin coasting down a hill to get above 42 mph, the
engine remains OFF. I've had mine up to 68 or so mph, just about
the MG1 rev limit, in N with the ICE stationary. Air resistance
kept me from going any faster on that test. But the system did NOT
intervene and try to control the MGs to start spinning the engine.
.
All the other state changes, fuel-cuts, torque transfers, etc require
the system to be in something other than N to happen.
.
Idling fuel consumption can be figured fairly easily from the fact
that the minimum injector pulse length seems to be about 2 ms, and
idle speed is about 1000 rpm. That works out to an injector duty
cycle of 1.something percent -- small, but still consuming.
.
_H*

 

<div class='quotetop'>QUOTE(ScottY @ Sep 1 2006, 06:52 AM) [snapback]312691[/snapback]</div>

ScottY, for some reason the "Five stages of Prius Operation" url doesn't work anymore or at least it isn't working for me. Can you check it out at your convenience? Thanks.

Also, this may be slightly off topic, but is everyone in agreement that shifting into neutral, regardless of the speed situation, should not be detrimental to the mechanical operation and long term functionality of the 05+ Prius? Thanks.

 

I've got a slightly augmented copy up at
http://techno-fandom.org/~hobbit/cars/five-stages.txt
but daniel gets all the credit!
.
_H*

 

I guess the confusing thing is that we are discussing the same thing. At above ~ 42 MPH the ICE must run to keep the PSD in balance. Their must be some power to do this. It is not free. MG1 does that, but I thing that in Stealth mode MG1 or MG2 does the same thing. Something has to spin the PSD to go into "stelth" mode. Something is consuming more Amps than sitting at the stop light and that is 3-4 amps over everything off. I would guess that in "glide" mode the PSD is being spun by electrical power to keep it "neutral" with the wheels. I do not think that the spin of the wheels even down hill is doing this. Their is not a lot of energy expended but their is some when we are in "guide" mode.