Coasting in neutral

It's not a competition, it's about the facts. If you connect a process monitor, it will show the electric drive motor running in reverse whenever the gas engine is running while the car isn't moving.
Incidentally, my gas engine has started many times while the car is either in park or neutral. There's no way that can happen without the electric motor compensating by running in the opposite direction.

 

Please be clear about which motor, MG1 or MG2, you mean when you say "the electric drive motor" (which is not the established Prius term for anything). Also, which rotation direction you mean by "reverse". Besides clarifying the discussion, that could begin to clarify things for you too.

The rotation of MG2 is always the same relative to the rotation of the wheels. It physically cannot ever be different.

The rotation of MG1 can be in either direction relative to the rotation of the wheels, depending on the relative speed of the wheels and the engine. There is a nomograph where you can draw a straight line between any two of those points (MG1 RPM, MG2 RPM, engine RPM) and the third will always be on that line. It physically cannot ever be different.

So from this it's clear that MG1 is the motor you're talking about (here, at least), given that you say "while the car isn't moving" and MG2 cannot ever move when the wheels aren't turning. But if you could begin to use the established terms, it wouldn't be necessary for others to piece together which motor you're talking about. [edit: for the record, MG1 is not a likely choice to call "the electric drive motor", as it's the smaller of the two.]

An interesting report. Not the "in park" part; that's normal.

Is there anybody else reading, who has a 2024 Prime, who has seen it start the engine while in neutral? (For any reason other that the overspeed protection override documented in the manual?)

 

Some people will go to any lengths not to lose an argument.

 

Because PriusChat threads stick around and other people find them and read them, as long as it's possible for later readers who want to learn to find the correct information there, it's all good.

 

Incorrect information, such as the brushless motors coasting, instead of running in reverse to compensate for the forward motion of the ICE?

 

If I'm in the car, it's on, say pulled over, stopped, on a bit of a grade, with my foot on the brake, and now I shift into Neutral, release the brake: the car will start rolling downhill, just like any other car in Neutral. As far as I know, the only reason it won't do that when the car's off, is due to a "parking pawl", some sort of stubby rod, that lodges into a recess in some flywheel.

 

You can try this: put the car IG ON, shift to N, and pull off the 12 V battery ground. Now the car is without any power, and still in N (not having gone back to P as it does when you power off with the switch).

Raise the front of the unpowered car off the ground and rotate the wheels. MG1 inside the transmission will counterrotate. There's nothing else it can do. It is a plain consequence of how the tranny is mechanically built.

There is nothing the car's electronics have to do to make that happen. Forget "the wheel sensors cause the computers to match the rolling speed of the car to the speed of the drive train" as nothing of the sort is happening just now. You're seeing simple mechanical action.

Now, when the car is powered up and not in neutral, it does actively manipulate both MG2 and MG1 currents in order to direct power in the desired ways. There has been a lot written about how that works, both in the Toyota literature and here on PriusChat. If you were to spend reading that even a fraction of the time you spend trying to spread your own notion of how the car works, you could be learning it yourself.

 

I'd rather look it up than to monkey around with it. When I'm in neutral or drive, and I activate "charge" mode, the motor revs up, and the car goes nowhere. Explain that without the MG1 reversing.

On the attached page, note the negative rotation numbers for MG1 when it's not contributing to wheel torque:
Whats Going On As I Drive?

 

Has anyone in this thread ever said MG1 doesn't counterrotate at times? I have repeatedly, explicitly, said that it does.

The only point in contention is whether it is under electrical power when it does that. In N, in normal conditions, it is not. It is simply counterrotating because that's what mechanically must happen.

Now, if you are in neutral, and the engine is stopped, and then the engine starts (accepting for now without comment your claim that it does so), that does require, for the moment it takes to crank the engine, some electrical power to MG1. As I mentioned in post #40, the car is programmed to violate the neutral rules momentarily for certain needs, and Toyota explains those cases in their service literature (so, if you'd "rather look it up", you can).

In earlier generations, a need to charge the battery was not an allowed reason for the car to do that, and you would simply see a warning message that the battery could be discharged by staying in N too long.

If Toyota has changed that and a 2024 Prime will start the engine for charging purposes while in neutral, that's interesting news. It isn't impossible; they can have changed the car's programming any way they like. I'll wait for some confirmation from others though.

You've now couched the claim a couple different ways:

In one case, you've written "park or neutral", and in one case, "neutral or drive". There isn't any need to bring park or drive into it; everyone agrees the car will start and stop the engine for charging purposes when it is in park or in drive.

The only case it would be good for someone else to confirm is whether it will do so in neutral (which is the only part that would be a change from earlier generations). All your 2024 Prime owners' manual says on that question is "In the N, the gasoline engine operates but electricity cannot be generated." On the face of it, that still sounds as if they won't use the engine for charging in N ... but that sentence might not have been the translators' best work.

 

I've done the coast in N down and on flats in both the Prime and the PiP. The two models behave differently.
It gave what I thought was more EV range in the PiP ( Gen 3 Plugin 2012-2015 ) model.
The Prime is a bit more complex, so results can surely be different in different conditions. When I've tried it in the Prime at slower speeds while trying to eck out every last kWh from the hybrid battery and miles of EV range, and knowing I'd be cutting my EV range really close to empty before I'd reach a place to charge, while coasting in N did show a benefit initially right after the coast, the prime seemed to me to give a penalty in full EV range about equal to the benefit initially observed after the coast.
Again, those are only my observations, and should have no relevance to your findings under different conditions.

edit: after experiencing my results from coasting on my daily drives, I didn't bother any longer trying to understand if there might be other conditions that could give an observable benefit in EV range from coasting in N I just never did much testing on if there is a way to game the Primes calculations in that respect. which I think might be possible given some very specific conditions, perhaps much like the ones you've experienced.

 

I give up. You're determined to win (as if it's a contest) so be it.

 

I'm determined that it be possible for other people reading the thread to learn and understand how the car works.

This discussion did raise an interesting question that it would be valuable to get others' reports on:

Will a 2024 Prime, left in neutral, start the engine if the only reason is to add charge to the traction battery? (In the absence of some other condition that requires starting the engine, such as exceeding the no-engine road speed.)

In the earlier generations I can speak for, the answer was no (and that was documented), so if the answer is yes for a 2024 Prime, that will be useful new information out of this thread.

 

It's extremely hard to convince regular Prius (non Prime) owners that Primes behavior under certain conditions isn't always the same as what's expected from the regular Prius. Don't give up on trying to discribe your observations, even with extremely logical descriptions of how a regular Prius typically works. The two are extremely different cars in very specific modes that can be hard to explain and many times, even to other Prime owners with different driving styles.

 

Just the one-way sprag clutch assembly on the Prime's flywheel gives the Prime a completely different behavior than a regular Prius.

 

Anybody around who can put one of these cars in Neutral with the engine stopped, and answer the yes/no question whether the engine starts, in Neutral, to add charge to the battery?

 

You mean a Gen5? Prime or not? I have a Gen4 Prime so unless that's what you meant, I can't.

But I guess the easiest way to try and start the engine with the transmission in Neutral is to turn on Defrost.

 

In EV mode and with 10 miles of EV range left, warm ambient temps 80 ish F.
the engine stayed off when put in N and coasting at 20 ish mph with a very slight drop in elevation 5 ft. ish, coasting for around 1/3 to 1/2 a mile. One observation that covers a very specific set of conditions. I'm not making any assumptions about what you're asking or what might happen in another Prime given similar or different conditions.

edit from memory probably 5 years ago, probably started the glide in N at 35 mph and ended at around 20 mph and the drop in elevation might have been more but definitively not less. I could look it up on a topographic map if you need the elevation drop nailed within closer specs..

 

The Prime can be driven similarly to a regular Prius in HV mode, even in an "enhanced" golf cart mode, explained in a long forgotten post here by
@daniel and archived on this page
https://techno-fandom.org/~hobbit/cars/five-stages.txt see under Definitions: - EVmode:
except it's done with HV mode in the Prime, slowly - like golf cart slow.
than add it's EV range and HV / EV switching techniques, it becomes clear that those enhancements bring with them programming changes and thresholds of almost exponential variety while testing them, when compared to the regular Prius as well as the Gen 3 Plugin. '
EV / HV mode switching was discussed mostly 7 years ago
@PiPLosAngeles lead most of those discussions.

 

The video I'm remembering, from the (Yakima?? Wenatchee??) Washington area, he had them use Neutral only for expediency in the short training drive sessions. I remember him indicating that holding the gas pedal lightly to keep the HSI bar at the neutral glide position did the same thing for these purposes, but took some time to master, thus reducing time available for working on the other points he needed to cover in those demos.

 

I'll try to clarify so assumptions aren't needed about what I'm asking:

Will a Prime, that is in neutral with the engine stopped, start the engine to add charge to the battery, while in neutral?

Earlier and non-plugin Prii will not—that's why there are threads here about people going through car washes and getting their batteries depleted. In neutral the car will not use the engine to charge the battery. It will display a message that you're doing something dumb, but it's just too bad for the battery, the state of charge will just keep going down until you switch out of neutral.

It's possible that Prime drivers rarely or never have the same experience in a car wash, just because the battery capacity is greater, but that's a different question. The question here concerns times when the battery state of charge gets low enough that the engine would normally (outside of neutral) start up to charge it. So it could be tested by first running down the battery to typical HV states of charge, then shifting to N and sitting there to watch the state of charge go down.

While sitting there in N watching the charge go down, does the engine eventually start and send the state of charge upward? Or does it just show you a warning message to shift out of N, as an older Prius would? Or does something else happen?

Or, if you select "charge" mode while sitting there in N, does the engine then start and send the state of charge upward?

If a current Prime will start the engine to add charge, while in neutral, unlike other Prii that will just show a warning that you'd better shift out of neutral, that's a behavior change that would be worthwhile to know about.