Repost from Reddit; and then a question

Nor the level of vitriol.

 

because i was confused by your question in your first post, and thought it was regarding putting a prius in neutral.

 

I kinda wonder if there's anyone else reading this thread who has failed to notice that the 'quoted anecdote' was simply a story about a Prius that didn't get shifted into neutral, because the driver didn't hold the lever as required to shift into neutral.

When bisco thought that was what the anecdote was, it's because that's what the anecdote was.


Paul's questions, as seen reiterated in #3 (independently, one observes, of the reddit anecdote), are familiar from other threads where Paul has raised them. Where bisco wonders about understanding the Prius drivetrain in sufficient detail, it's those questions that require that kind of technical depth. Understanding the reddit anecdote does not. You gotta hold the lever till N shows up on the dash, that's the moral of the reddit anecdote.

It's quite possible in this thread to recognize that Paul's reiterated questions aren't related to the reddit anecdote, without otherwise taking a position on them here. A reader interested in those questions would miss less of the already existing discussion by looking in the threads where they've already been discussed:

https://priuschat.com/search/758973844/?q=neutral&t=post&o=date&g=1&c[user][0]=203815

 

Have we reached the inevitable “irreconcilable differences” phase?

 

thanks, i had totally missed your point. my bad

 

Or, that could be the point if the reddit post had been about anything that happened when a Prius was put in neutral.

Only, the reddit post was about a Prius that wasn't put in neutral. It went forward in D because it was in D and the driver didn't know how to put it in neutral. It went backward in R because it was in R and the driver didn't know how to put it in neutral.

The driver did eventually figure out how to put it in neutral, but then included no further description of what the car did. Which means the reddit post contains zero words having anything to do with anything any Prius ever did in neutral.

The questions Paul asked (and reiterated in #3) are familiar questions Paul has posed before about what happens in neutral. Those other threads are still around and the questions have been discussed there.

There just isn't anything new about those questions that can be mined from a reddit post that says nothing about anything a Prius ever did in neutral.

 

It seems Paul is using conventional wisdom and his "common sense" to reach his assumptions on how planetary gears, power electronics, programmed logic and electric motors in the transaxle work.

Weber State's Toyota sanctioned ecvt transaxle classes can provide a new perspective for someone's conventional wisdom and "common sense". It takes hours to digest and perhaps repeated viewings but the student learns the Toyota ecvt transaxle was a patented breakthrough technology in a cost effective package. With neutral achievable without a running engine or a functioning inverter.

Some of these things are not decided by consensus; they don't need a vote. Can a typical owner be expected to truly understand the details? Not likely, which leaves room for conventional wisdom and "common sense".

 

How the system works, with evidence, has been explained to you multiple times. You refuse to except it, and continue to bring the topic back up elsewhere. Here you posted a story that has nothing to do with how the system works to get back on your repeated questions.

There are no clutches, nor torque converter, in the Prius drivetrain. Free wheeling is the only possibility when in neutral. The M/Gs are perfectly fine spinning without electricity going in or out. Since M/G 2 is already spinning with the wheels when neutral coasting, there is no 'bump' when the car is put back in drive. M/G 1 spins the engine up matching revs before starting, so no 'bump' there.

 

If that wasn't the case, the design of all of the hybrids on the market, and Toyota's in particular, would make no sense, with their permanently engaged MGs. The HSD would be particularly inefficient with two MGs causing drag. Toyota's HSD PHEVs would particularly benefit from a clutch to disengage MG1 for EV operation, and the current PHEV design would be notably less efficient than single-MG EVs.

In a world where MGs couldn't freewheel they'd invent a lot more complex EV and hybrid drivetrains to avoid spinning MGs to gain efficiency, and the designs we see in this world would be laughably crude and inefficient.

In this world I can't think of a single hybrid or EV design that mechanically disengages an MG in normal operation.

 

I worry a bit that the more we end up rehashing all the past discussion of Paul's old "how does neutral work" questions here in this thread that arises only from a reddit post about how to shift to neutral, the more we've been played.

#45 above has a saved search to locate existing threads where the past discussion of Paul's technical questions can be found.

 

OK, I think I understand what Paul is trying to put together. I believe he feels that since the Prius e-transmission is always "engaged" between the motor, engine, and wheels via a planetary gear set, the only way they can do "neutral" is to spin the electric motor opposite to the engine so the net result is 0 rpm on the wheels. I think he's wondering how the motor is able to instantly match spin.

If I have interpreted that accurately above, then the answer is......

At the car wash, your wheels are already stopped. Assuming the engine isn't already off due to the slow speed (0 mph), nothing is moving so nothing needs to spin up. Voltage is removed from the electric motor and it's now free to rotate. However, if the engine is running, then the motor is already matching it's spin in reverse because you are sitting still.

Now if we change the scenario to driving on a highway and you decide this would be a grand time to drop it into neutral... the same condition exists. Your wheels, engine, motor are already spinning at the correct RPMs to match each other due to the planetary gear set. The only thing that needs to happen is torque (either gas or electric) is removed and physics (momentum) does what it always does.

The concept of the e-transmission is pretty cool and definitely interesting to research. Here's a vid from WeberAuto showing how the guts work on the prior gen.

 

You "request" to go to Neutral, the car's computers consider the request, and comply only if mechanically safe to do so. You can also attempt to shift to reverse, and IIRC it'll instead put you in neutral.

 

Oh yes! I should have clarified that the operator is free to make requests... I have no idea if the car will actually comply or not and I'm not willing to test it.

 

All the bits that were spinning in certain directions at certain speeds the instant before you selected Neutral are spinning in the same directions at the same speeds the next instant. No sudden energy input is needed to achieve that.

It's possible you haven't looked much at Paul's earlier threads wondering how Neutral works. From the link in #45 upthread you can find them.

What distinguishes this thread is that it starts with a reddit post having nothing to do with what happens in Neutral. If you don't know the way to select Neutral (move the lever left and hold), then you haven't selected Neutral, and that's what the reddit post was about.