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Hi all.
I'm guessing that most of you won't see the point of this, but I just wondered if changing the gear selector to neutral whilst travelling downhill (and not touching the brakes) is harmful to the transmission? Obviously I won't be getting any regen' but that's not the point of this 'experiment'.
 

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Why would you want to do that?!??!?!?!
In a car that can actually take advantage of going downhill and make you travel for free even further than the hill?!?!?!
 

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What is the point of the 'experiment then? Maybe we can help you avoid the risk?
 

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Risk of what?
Risk of whatever it is that the driver's manual says to avoid.

By definition, a 'risk' is not necessarily something that may become actualised.

In the case of BEVs with permanent magnet motors, I have given copious technical notes on the risks.

In the case of a car which ALSO has a fancy clutchy gearboxy thing, well, the mind can boggle. All manner of possibilities.

You might recall that in ICE vehicles, the gear oil is pumped by the engine side, and in others by the output shaft side, so in one case idling stationary means the gearbox is not lubricated and freewheeling with the engine off means it is not lubricated in the other. Thus, some cars had oil pumps on both engine and propshaft side.

Not that this applies to GTE, but you see what I mean. Adding in a shifting gearbox merely adds yet further to the potential risks, which there already are with a permanent magnet motor.
 

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Coasting is actually more efficient than using regen, in most circumstances.

It’s a free world. He wants to coast, let him coast.
In general, I will agree with your two points.

But the OP wasn't asking about "general". He had in mind a very specific scenario: going downhill.

So, let's talk about going downhill. First off, you have these things that stop you from "speeding". Meaning that when gaining speed going downhill, you still have to keep to the speed limit. Stupid presumption I know, freedom and such, but there are laws, and some people like to keep to them.

Second, assuming you are at the speed limit, you have to slow down in some way. In neutral, you can't regen in a GTE. The mechanical brakes will engage. Which is wasted energy, that can be recuperated and then reused to propel you further than the downhill.
 

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On the GTE, 'D' mode in either hybrid or e-mode behaves identically to being in 'N' with one exception. The car will recuperate enough energy to maintain your current speed when going downhill. Regular cars in 'N' will get faster and faster, requiring you to use the brakes. The GTE does not do this.

No harm should come from using the car in 'N', but you'd be losing out on freely available kinetic energy. From memory, the car has an electric oil pump for the transmission fluid, which operates regardless of the input/output shaft spinning.
 

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In general, I will agree with your two points.

But the OP wasn't asking about "general". He had in mind a very specific scenario: going downhill.

So, let's talk about going downhill. First off, you have these things that stop you from "speeding". Meaning that when gaining speed going downhill, you still have to keep to the speed limit. Stupid presumption I know, freedom and such, but there are laws, and some people like to keep to them.

Second, assuming you are at the speed limit, you have to slow down in some way. In neutral, you can't regen in a GTE. The mechanical brakes will engage. Which is wasted energy, that can be recuperated and then reused to propel you further than the downhill.
Did the OP ask about 'breaking laws whilst coasting'?
 

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I'd fail my test if I drove as instructed for my advanced driver training.

Doesn't mean it's incorrect.
What sort of things are you taught on ADT that would fail you on a driving test? Do you mean the emergency services training?

I can’t recall anything when I did mine, not emergency services the IAM
 

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Coasting in neutral would be more efficient than leaving the motor engaged, but only by the amount of power it would take the motor to turn itself without load at the required speed — almost nothing.
 

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On the GTE, 'D' mode in either hybrid or e-mode behaves identically to being in 'N' with one exception. The car will recuperate enough energy to maintain your current speed when going downhill. Regular cars in 'N' will get faster and faster, requiring you to use the brakes. The GTE does not do this.

No harm should come from using the car in 'N', but you'd be losing out on freely available kinetic energy. From memory, the car has an electric oil pump for the transmission fluid, which operates regardless of the input/output shaft spinning.
Nope. I keep explaining this, over and over.

Tell me how many motor controllers you've been involved in designing, and then we can discuss it properly from the standpoint of your 'known' knowledge.

But hey how, ignorance is bliss and it is the downfall of the educated to have knowledge, eh? Boko haram, and all that?
 

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What sort of things are you taught on ADT that would fail you on a driving test? Do you mean the emergency services training?

I can’t recall anything when I did mine, not emergency services the IAM
When I did my IAM a number of things were taught that would result in a fail of the basic L test.

For example, "use of the road"- crossing over the centre line to take the smoothest fastest route with best vision would probably result in some markers during an L test. Use of the road at a T-junction with good visibility could easily cause an instant L test failure due to the rigid rules on L test about "crossing the T".

During my IAM test I made a small mistake (down a steep hill in a higher speed limit into a 30 limit at the bottom, I passed the 30 sign at between 35 and 40mph while decelerating). After the test he said I'd passed and I queried about that mistake and he (serving traffic officer) shrugged and said "you got down to it, you're aware of it, you didn't do anything dangerous". The IAM approach seems very much more about pragmatism than the absolute letter of the law and ticking boxes (which the L test relies on, and for moderation reasons must do so).
 

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Years ago on a really hot day on the a303 I had to coast with the engine off to stop my Laguna from over heating. That's the only situation I would consider coasting. You are not is control of the car to the same extent and that is compounded by speed.

As far as economy goes I really struggle with the theory that it's more efficient due to the fuel supply being cut at zero throttle on modern engines. Add in the regen etc of a hybrid setup and it makes even less sense.

As for your question OP, if it will let you shift to N then it should be fine.

Could you explain what the reason is?
 

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Nope. I keep explaining this, over and over.

Tell me how many motor controllers you've been involved in designing, and then we can discuss it properly from the standpoint of your 'known' knowledge.
But hey how, ignorance is bliss and it is the downfall of the educated to have knowledge, eh? Boko haram, and all that?
I haven't designed anything as big as the GTE's inverter(!) but I have designed a few small 3 phase BLDC controllers in my time. (I am an EEng by profession but mostly deal with FPGAs nowadays. I find exploding MOSFETs to be tiresome and 400V DC to be a bit too tingly for my taste.)

The GTE has clutches in its gearbox, it could be checked with VCDS but I suspect at zero power in 'D' or 'B' it leaves these engaged because the motor without the engine is very little drag. (Also, it would put extra wear on the clutch packs to shift them out, plus it would introduce performance 'latency' akin to shifting a gear.) Is this bad for the motor or not? I couldn't tell you, but my car has 80k miles on the e-motor, and there's no obvious sign of bearing wear or additional noise from the motor. Most EVs have the motor permanently engaged without any declutching, so no disadvantage there compared to regular EVs.

The 'N' gear on the other hand almost certainly does disengage the clutches, and there is a way to "unofficially" test this. There is a hidden 'gear' between N and P, which if selected will allow you to rev the e-motor, but without the clutches engaged. You will hear the motor spin up, and the power meter moves, but the wheels don't go anywhere. I am not responsible for any gearbox damage, I discovered this by accident, but my car seems fine.

As for efficiency, as the 'D' mode recuperates energy when going down hill to prevent you exceeding your present speed, it is a bit like adaptive cruise control in that respect. It is true it is less efficient in the strictest sense than coasting, however, we have speed limits in this country. If I arrived at the bottom of a nearby hill doing 45 mph, I'd be snapped by the camera van that parks there every other week. Thankfully, the GTE keeps my licence clean, for once.
 
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