Automatic gearbox and regular use of neutral

BOWFER

Ditzy_Mitzy said:

I'm not totally convinced that regenerative braking can be 'turned off' either, as someone else put it.  The Nissan Leaf has selectable single pedal driving, which enhances the function, however in normal mode I believe that it does use the electric brake to slow down when the brake pedal is depressed.  There's no reason why it shouldn't.  The hydraulic brakes are there as a semi-redundant system in case of electrical failure.  

If you're referring to my posts, I didn't say regen braking can be turned off.
It can't, if you brake you regeneate and that's that.
I've only ever referred to engine braking effect, meaning off the throttle but also off the brakes..
In standard mode it's zero (or damned close to zero).
Switching to B mode brings in a certain (fixed in the Leaf) amount of engine braking, which also sends some power back to the battery.
I should add if the car is close to 100% charge the B mode is effectively disabled and you freewheel the same as you would in D.
As for the hydraulic brakes being redundant, this must only be if you drive very gently.
I know the way I drive, the brakes are working the same as any other car.
The single pedal driving, to me, is awful and I won't ever try it again.

itsmeagain

neilmcl said:

Advocado said:

itsmeagain said:

neilmcl said:

BOWFER said:

Advocado said:

basill said:

Not just DSG, Volvo 8 speed non dsg autos coast in eco mode.   Must be something to save.    Emissions if not actual fuel possibly 🙂

If Volvo of all manufacturers have their cars coast, it can't be as dangerous as people on here seem to think.

I think the 'danger' part of it is being grossly exaggerated by some on here, I'm not joining in on that.
My electric car has very little to zero braking effect in D.
I have to select B mode to get any.
I wouldn't call it dangerous at all, it's just people getting all preachy.

Not at all.

Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact.

Can you please explain why you think that a modern auto vehicle, auto selecting the highest gear and only changing down each time the revs get low (offering very low engine braking), would stop significantly earlier, than the same vehicle in Neutral. Bear in mind that modern braking systems are perfectly capable of locking the wheels and delivering near perfect cadence braking whether in gear or not?

Also bear in mind that the brakes are relatively 'cold' having not needed them to maintain speed down the hill.

Please explain the technical reason for this fact without saying that it's a well known fact.

I've already asked @neilmcl to explain his theories, but he goes uncharacteristically quiet.

Don't make things up, I've answered every single reply you've put to me up to this post. And yes, I've gone quiet now but that's because my Dad's gone into hospital so my attention is elsewhere.

I'll leave this thread now as I've got other things to deal with but you asked for second opinions, and I gave mine, I'm more than happy for you to ignore, dispute them, that's what the forum is all about after all.

Good luck with your Dad!

I thought you said (copy/paste) "Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact"

Now that's very 'preachy' because without explanation it's a leap of faith.
If "it's just a simple fact", can you "simply" explain it please? I genuinely don't understand the logic.
I'm not sure from your last post if you've changed your mind, now claiming it's 'opinion' where earlier it was fact?
Please clarify, is this a fact that you can explain or an opinion that you can't?

BOWFER

itsmeagain said:

neilmcl said:

Advocado said:

itsmeagain said:

neilmcl said:

BOWFER said:

Advocado said:

basill said:

Not just DSG, Volvo 8 speed non dsg autos coast in eco mode.   Must be something to save.    Emissions if not actual fuel possibly 🙂

If Volvo of all manufacturers have their cars coast, it can't be as dangerous as people on here seem to think.

I think the 'danger' part of it is being grossly exaggerated by some on here, I'm not joining in on that.
My electric car has very little to zero braking effect in D.
I have to select B mode to get any.
I wouldn't call it dangerous at all, it's just people getting all preachy.

Not at all.

Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact.

Can you please explain why you think that a modern auto vehicle, auto selecting the highest gear and only changing down each time the revs get low (offering very low engine braking), would stop significantly earlier, than the same vehicle in Neutral. Bear in mind that modern braking systems are perfectly capable of locking the wheels and delivering near perfect cadence braking whether in gear or not?

Also bear in mind that the brakes are relatively 'cold' having not needed them to maintain speed down the hill.

Please explain the technical reason for this fact without saying that it's a well known fact.

I've already asked @neilmcl to explain his theories, but he goes uncharacteristically quiet.

Don't make things up, I've answered every single reply you've put to me up to this post. And yes, I've gone quiet now but that's because my Dad's gone into hospital so my attention is elsewhere.

I'll leave this thread now as I've got other things to deal with but you asked for second opinions, and I gave mine, I'm more than happy for you to ignore, dispute them, that's what the forum is all about after all.

Good luck with your Dad!

I thought you said (copy/paste) "Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact"

Now that's very 'preachy' because without explanation it's a leap of faith.
If "it's just a simple fact", can you "simply" explain it please? I genuinely don't understand the logic.
I'm not sure from your last post if you've changed your mind, now claiming it's 'opinion' where earlier it was fact?
Please clarify, is this a fact that you can explain or an opinion that you can't?

I suppose, for the incredibly pedantic, that split second of engine braking when you come off the throttle and go to the brake pedal will slow the vehicle down a miniscule amount before braking takes over and the engine braking becomes irrelevant.
But...jeez...it's must be a miniscule amount as to be immeasurable.

neilmcl

itsmeagain said:

neilmcl said:

Advocado said:

itsmeagain said:

neilmcl said:

BOWFER said:

Advocado said:

basill said:

Not just DSG, Volvo 8 speed non dsg autos coast in eco mode.   Must be something to save.    Emissions if not actual fuel possibly 🙂

If Volvo of all manufacturers have their cars coast, it can't be as dangerous as people on here seem to think.

I think the 'danger' part of it is being grossly exaggerated by some on here, I'm not joining in on that.
My electric car has very little to zero braking effect in D.
I have to select B mode to get any.
I wouldn't call it dangerous at all, it's just people getting all preachy.

Not at all.

Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact.

Can you please explain why you think that a modern auto vehicle, auto selecting the highest gear and only changing down each time the revs get low (offering very low engine braking), would stop significantly earlier, than the same vehicle in Neutral. Bear in mind that modern braking systems are perfectly capable of locking the wheels and delivering near perfect cadence braking whether in gear or not?

Also bear in mind that the brakes are relatively 'cold' having not needed them to maintain speed down the hill.

Please explain the technical reason for this fact without saying that it's a well known fact.

I've already asked @neilmcl to explain his theories, but he goes uncharacteristically quiet.

Don't make things up, I've answered every single reply you've put to me up to this post. And yes, I've gone quiet now but that's because my Dad's gone into hospital so my attention is elsewhere.

I'll leave this thread now as I've got other things to deal with but you asked for second opinions, and I gave mine, I'm more than happy for you to ignore, dispute them, that's what the forum is all about after all.

Good luck with your Dad!

I thought you said (copy/paste) "Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact"

Now that's very 'preachy' because without explanation it's a leap of faith.
If "it's just a simple fact", can you "simply" explain it please? I genuinely don't understand the logic.
I'm not sure from your last post if you've changed your mind, now claiming it's 'opinion' where earlier it was fact?
Please clarify, is this a fact that you can explain or an opinion that you can't?

Thanks for the concern regarding my Dad.

Can I ask you a question, in a manual do you not agree that it takes more effort to stop car if you brake with the clutch depressed than it is if you brake whilst in gear, then use the clutch at the last minute? The point I was making that it should be obvious that emergency braking, downhill whilst in neutral will take far more effort than if the speed is already being kept in check (for want of a better phrase) by the correct gear.

Also, to address @BOWFER's point regarding EVs, don't most EVs perform a certain amount of regenerative braking anyway, even if not explicitly set. I'm genuinely asking, as I don't know.

BOWFER

neilmcl said:

Also, to address @BOWFER's point regarding EVs, don't most EVs perform a certain amount of regenerative braking anyway, even if not explicitly set. I'm genuinely asking, as I don't know.

I've already tried to explain it several times, I'm maybe failing in getting it across.
In the case of the Leaf, driving in the default 'D' mode doesn't provide any meaningful engine braking when you come off the throttle, you're effectively freewheeling and the car will speed up down steep hills.
The driver can select 'B' mode, which gives much stronger engine braking, and with practice you can drive around town using this to the extent the car will almost stop and only needs the friction brakes to come to a full stop.
I've driven Zoe's and BMW i3s regularly too and memory tells me their default settings are much the same, I don't remember either of them having strong engine braking in their default mode.
So, again, their default must be that you're practically freewheeling when you come off the throttle.

itsmeagain

BOWFER said:

itsmeagain said:

neilmcl said:

Advocado said:

itsmeagain said:

neilmcl said:

BOWFER said:

Advocado said:

basill said:

Not just DSG, Volvo 8 speed non dsg autos coast in eco mode.   Must be something to save.    Emissions if not actual fuel possibly 🙂

If Volvo of all manufacturers have their cars coast, it can't be as dangerous as people on here seem to think.

I think the 'danger' part of it is being grossly exaggerated by some on here, I'm not joining in on that.
My electric car has very little to zero braking effect in D.
I have to select B mode to get any.
I wouldn't call it dangerous at all, it's just people getting all preachy.

Not at all.

Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact.

Can you please explain why you think that a modern auto vehicle, auto selecting the highest gear and only changing down each time the revs get low (offering very low engine braking), would stop significantly earlier, than the same vehicle in Neutral. Bear in mind that modern braking systems are perfectly capable of locking the wheels and delivering near perfect cadence braking whether in gear or not?

Also bear in mind that the brakes are relatively 'cold' having not needed them to maintain speed down the hill.

Please explain the technical reason for this fact without saying that it's a well known fact.

I've already asked @neilmcl to explain his theories, but he goes uncharacteristically quiet.

Don't make things up, I've answered every single reply you've put to me up to this post. And yes, I've gone quiet now but that's because my Dad's gone into hospital so my attention is elsewhere.

I'll leave this thread now as I've got other things to deal with but you asked for second opinions, and I gave mine, I'm more than happy for you to ignore, dispute them, that's what the forum is all about after all.

Good luck with your Dad!

I thought you said (copy/paste) "Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact"

Now that's very 'preachy' because without explanation it's a leap of faith.
If "it's just a simple fact", can you "simply" explain it please? I genuinely don't understand the logic.
I'm not sure from your last post if you've changed your mind, now claiming it's 'opinion' where earlier it was fact?
Please clarify, is this a fact that you can explain or an opinion that you can't?

I suppose, for the incredibly pedantic, that split second of engine braking when you come off the throttle and go to the brake pedal will slow the vehicle down a miniscule amount before braking takes over and the engine braking becomes irrelevant.
But...jeez...it's must be a miniscule amount as to be immeasurable.

You may be interested to know that the split second that you refer to much depends on how much 'simulated mechanical damping' the calibration has got. To avoid sharp changes in torque (that causes driveability issues), known as 'off throttle shunt', when the engine rocks across it's neutral mounting axis with driveline backlash, calibrations often filter the drop in torque demand to simulate what mechanical dampers did on carbs.

On some manual petrol cars, this is particularly annoying when you change up gears and the revs haven't dropped in time to match the revs of the higher gear. The opposite of purposely blipping the throttle on down changes that Jenni mentioned earlier.

Also, the injection timing of petrols is early in the intake stroke, so there may be several cylinders that have already received their air and fuel that need to be combusted following lifting off the throttle. This unwanted torque from these cylinders can be reduced by retarding the ignition to transfer less power to the piston.

Keep_pedalling

BOWFER said:

All this fuss about engine braking, yet no-one has commented on me twice pointing out electric vehicles don't offer any as standard.
So those who think engine braking makes a difference during emergency braking are what, just burying their heads in the sand?

Even in D mode EVs use regen on breaking. Lightly hitting the breaks on my ID3 slows the car down using the motor alone, the actual breaks only kick in under heavier breaking where both are used.

Ditzy_Mitzy

neilmcl said:

itsmeagain said:

neilmcl said:

Advocado said:

itsmeagain said:

neilmcl said:

BOWFER said:

Advocado said:

basill said:

Not just DSG, Volvo 8 speed non dsg autos coast in eco mode.   Must be something to save.    Emissions if not actual fuel possibly 🙂

If Volvo of all manufacturers have their cars coast, it can't be as dangerous as people on here seem to think.

I think the 'danger' part of it is being grossly exaggerated by some on here, I'm not joining in on that.
My electric car has very little to zero braking effect in D.
I have to select B mode to get any.
I wouldn't call it dangerous at all, it's just people getting all preachy.

Not at all.

Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact.

Can you please explain why you think that a modern auto vehicle, auto selecting the highest gear and only changing down each time the revs get low (offering very low engine braking), would stop significantly earlier, than the same vehicle in Neutral. Bear in mind that modern braking systems are perfectly capable of locking the wheels and delivering near perfect cadence braking whether in gear or not?

Also bear in mind that the brakes are relatively 'cold' having not needed them to maintain speed down the hill.

Please explain the technical reason for this fact without saying that it's a well known fact.

I've already asked @neilmcl to explain his theories, but he goes uncharacteristically quiet.

Don't make things up, I've answered every single reply you've put to me up to this post. And yes, I've gone quiet now but that's because my Dad's gone into hospital so my attention is elsewhere.

I'll leave this thread now as I've got other things to deal with but you asked for second opinions, and I gave mine, I'm more than happy for you to ignore, dispute them, that's what the forum is all about after all.

Good luck with your Dad!

I thought you said (copy/paste) "Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact"

Now that's very 'preachy' because without explanation it's a leap of faith.
If "it's just a simple fact", can you "simply" explain it please? I genuinely don't understand the logic.
I'm not sure from your last post if you've changed your mind, now claiming it's 'opinion' where earlier it was fact?
Please clarify, is this a fact that you can explain or an opinion that you can't?

Thanks for the concern regarding my Dad.

Can I ask you a question, in a manual do you not agree that it takes more effort to stop car if you brake with the clutch depressed than it is if you brake whilst in gear, then use the clutch at the last minute? The point I was making that it should be obvious that emergency braking, downhill whilst in neutral will take far more effort than if the speed is already being kept in check (for want of a better phrase) by the correct gear.

Also, to address @BOWFER's point regarding EVs, don't most EVs perform a certain amount of regenerative braking anyway, even if not explicitly set. I'm genuinely asking, as I don't know.

The answer to the point about a manual, petrol driven car, to keep things as simple as possible, is that there might be a slight advantage to being in gear during the initial phase of an emergency stop, but it's probably too minor to make any difference in the real world.  
What I don't know, because I'm not a scientist, is how small the advantage is.  The engine braking effect comes from the engine's desire to work as an air pump.  When the throttle is closed, manifold vacuum increases (I've read up on it), which means that it's more difficult for the piston on the induction stroke to draw in air.  That causes the piston to descend more slowly, with them all doing it crankshaft speed is reduced.  
Now: with a manual gearbox, the road wheels are directly connected to the crankshaft via the gearbox and clutch.  That means applying a retarding force to the wheels will, eventually, apply a retarding force to the engine itself.  Applying the brakes, therefore, reduces engine revolutions.
The point, then, is that applying a strong retarding force to the wheels will also apply a strong retarding force to the engine.  If said force causes the engine to slow more quickly than it otherwise would with a closed throttle and no brakes applied, engine braking in other words, then presumably it won't be drawing on the manifold vacuum in the same way.  Ergo, under emergency stop conditions, I suspect there is a crossover point at which the effects of the mechanical brakes overwhelm the engine's ability to work as an additional brake.  Where is that point?  I don't know...

itsmeagain

neilmcl said:

itsmeagain said:

neilmcl said:

Advocado said:

itsmeagain said:

neilmcl said:

BOWFER said:

Advocado said:

basill said:

Not just DSG, Volvo 8 speed non dsg autos coast in eco mode.   Must be something to save.    Emissions if not actual fuel possibly 🙂

If Volvo of all manufacturers have their cars coast, it can't be as dangerous as people on here seem to think.

I think the 'danger' part of it is being grossly exaggerated by some on here, I'm not joining in on that.
My electric car has very little to zero braking effect in D.
I have to select B mode to get any.
I wouldn't call it dangerous at all, it's just people getting all preachy.

Not at all.

Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact.

Can you please explain why you think that a modern auto vehicle, auto selecting the highest gear and only changing down each time the revs get low (offering very low engine braking), would stop significantly earlier, than the same vehicle in Neutral. Bear in mind that modern braking systems are perfectly capable of locking the wheels and delivering near perfect cadence braking whether in gear or not?

Also bear in mind that the brakes are relatively 'cold' having not needed them to maintain speed down the hill.

Please explain the technical reason for this fact without saying that it's a well known fact.

I've already asked @neilmcl to explain his theories, but he goes uncharacteristically quiet.

Don't make things up, I've answered every single reply you've put to me up to this post. And yes, I've gone quiet now but that's because my Dad's gone into hospital so my attention is elsewhere.

I'll leave this thread now as I've got other things to deal with but you asked for second opinions, and I gave mine, I'm more than happy for you to ignore, dispute them, that's what the forum is all about after all.

Good luck with your Dad!

I thought you said (copy/paste) "Just think for a minute, your coasting downhill in a near 3 tonne vehicle do you really think your stopping distance is going to be the same as a vehicle that's in gear. It certainly won't be and every cm you can save in an emergency stop is critical. Nothing preachy about, it's just a simple fact"

Now that's very 'preachy' because without explanation it's a leap of faith.
If "it's just a simple fact", can you "simply" explain it please? I genuinely don't understand the logic.
I'm not sure from your last post if you've changed your mind, now claiming it's 'opinion' where earlier it was fact?
Please clarify, is this a fact that you can explain or an opinion that you can't?

Thanks for the concern regarding my Dad.

Can I ask you a question, in a manual do you not agree that it takes more effort to stop car if you brake with the clutch depressed than it is if you brake whilst in gear, then use the clutch at the last minute? The point I was making that it should be obvious that emergency braking, downhill whilst in neutral will take far more effort than if the speed is already being kept in check (for want of a better phrase) by the correct gear.

Also, to address @BOWFER's point regarding EVs, don't most EVs perform a certain amount of regenerative braking anyway, even if not explicitly set. I'm genuinely asking, as I don't know.

I would agree that engine braking produces a negative torque at the wheels, thus reducing the amount of direct wheel braking required to get the same level of overall braking. However, your comment was explicitly about an emergency stop, where you could stamp on the brakes with more braking capability than you know what to do with, so the ABS does it for you whether you had engine braking or not.

Many years ago, brakes were not so good, not assisted etc. It was very difficult on some cars to produce anywhere near the braking that you get on modern cars, so the additional engine braking would have supplemented the inadequate brakes.

On your EV question, different models have different selectable modes. I expect that you can have anything between lifting off the throttle and it 'sailing' on until you press the brakes to lifting off and it immediately applying the brakes or simulated braking via regen. Maybe other modes I've not thought of. This is not my area of expertise - sorry!

BOWFER

Keep_pedalling said:

BOWFER said:

All this fuss about engine braking, yet no-one has commented on me twice pointing out electric vehicles don't offer any as standard.
So those who think engine braking makes a difference during emergency braking are what, just burying their heads in the sand?

Even in D mode EVs use regen on breaking. Lightly hitting the breaks on my ID3 slows the car down using the motor alone, the actual breaks only kick in under heavier breaking where both are used.

Yes, but it's 'engine braking effect' that's being discussed here.
If you lift off the throttle in your ID3 going down a hill, will the car effectively freewheel or slow down?
In the Leaf's standard D mode, the car will more or less freewheel and even speed up if the hill is steep enough.
I'd have to select B to get any slowing down (engine braking) effect
Note this is only coming off the throttle, not applying the brake pedal.
I will select B in winter if going down a snowy hill to help me 'hold back' without touching the brake pedal.