Automatic gearbox and regular use of neutral

fred990

BOWFER said:

fred990 said:

Out of idle curiosity as a manual gearbox driver, do modern autos (either dsg or tc's) change down sequentially or just block change? Can't imagine them going through each gear in turn? 

DSG changes down in turn.

Okay, think I've heard tc's claim to be 'smoother' (?), maybe they don't? 

fred990

BOWFER said:

fred990 said:

Out of idle curiosity as a manual gearbox driver, do modern autos (either dsg or tc's) change down sequentially or just block change? Can't imagine them going through each gear in turn? 

DSG changes down in turn.

Okay, think I've heard tc's claim to be 'smoother' (?), maybe they don't? 

Herzlos

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?

Do EV's recover the energy via the motor of via some kind of hub device?
I don't think that outside of the regeneration modes there will really be any engine braking, so presumably they are confident that the brakes will be sufficient?

I have to admit to not being particularly familiar with how the regenerative braking on EV's works, or how they coast given that they don't need to be kept spinning to avoid stalling.

BOWFER

Herzlos 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?

Do EV's recover the energy via the motor of via some kind of hub device?
I don't think that outside of the regeneration modes there will really be any engine braking, so presumably they are confident that the brakes will be sufficient?

I have to admit to not being particularly familiar with how the regenerative braking on EV's works, or how they coast given that they don't need to be kept spinning to avoid stalling.

The brakes are perfectly sufficient, I rarely use the regen braking setting on mine and I drive it hard.
I think all the regen tech is in the motor, I don't think there's anything fancy in the hubs.

Jenni_D

Herzlos 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?

Do EV's recover the energy via the motor of via some kind of hub device?

It's all in the physics ... if the motor becomes a generator then it converts kinetic energy into electrical energy. (The other way round when working as a motor is converting electrical energy into kinetic energy). Therefore it will appear as a "braking load" on the vehicle (the energy conversion has to have an effect, otherwise we're in the realms of perpetual motion); if the braking load is greater than the inertial force (e.g. mass of vehicle and slope of the road) then the vehicle will slow down, otherwise the speed will either remain constant or its acceleration (very steep hill) will be !!!!!!.

ontheroad1970

itsmeagain said:

ontheroad1970 said:

itsmeagain said:

ontheroad1970 said:

I don't see how locking the wheels is a desirable thing at all, what with ABS and all.

Just to clarify, no one said that it was desirable to lock-up the wheels. I was saying that "modern braking systems are perfectly capable of locking the wheels". I.e, modern brakes are more than capable of achieving maximum braking, without the additional support of engine braking to do so.

The question... why would additional 'in gear' engine braking make the car stop quicker than using a modern braking system alone? I.e, "with ABS and all"

You think it will be safer with switched off engines?  You seem to be all for them.  So all electrics disengaged, an extra step to take to react to an unpredictable incident, or a predictable incident with an inattentive driver.  Of course those that want to lessen the safety protections are always 100% safe and attentive with eyes all over their heads so they never miss a thing.  

Back in the real world, all drivers get inattentive from time to time, some more than others.  Id rather that other drivers weren't turning their ignition off, with less power being supplied to the bakes through servo systems etc.  

The reference to locking brakes being desirable was inferred by your comment try comprehending what you write.

It will not be safer with automated switched off engines (stop on the move), but it will not be less safe. I do not propose that drivers switch off/on the engine themselves during coasting.

The electrics would not be switched off during an automated coasting engine stop. As mentioned earlier, the full benefits of such systems will not be seen until beltless engines. There are already engines will electric brake pumps, PAS, AC, ISG's etc without the need for the engine to turn to power what were traditionally ancillary belted items. Whether the driver is attentive or not makes no difference to what automated system is used. Cars are becoming safer and safer with these automated systems.

As you say, you inferred something from what I wrote. Try comprehending what you read rather than being so presumptuous.

Again... what is the benefit of 'in-gear' engine braking in the case of emergency braking when the brakes alone are more than capable of locking the wheels. For clarity - this should not be misinterpreted as me claiming that it's desirable to lock up the wheels! However... it will emerge in later posts that ABS does cycle between locking/partially locking the wheels and unlocking them...

Read this paragraph again.  You are definitely inferring, intentionally or otherwise that the brakes locking the wheels is fine in line with cadence braking which is a method of keeping steering while braking:

"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?"

As I say, I would not like to see safety systems bypassed.  It might be a minute amount of difference, but it can be life changing.  Also cadence braking is a particular braking skill and should not be advocated blindly.  You don't always have the time to pump the brakes.  The brakes locking the wheels would not be a good thing on a twisty downhill road.  

Ditzy_Mitzy

Herzlos 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?

Do EV's recover the energy via the motor of via some kind of hub device?
I don't think that outside of the regeneration modes there will really be any engine braking, so presumably they are confident that the brakes will be sufficient?

I have to admit to not being particularly familiar with how the regenerative braking on EV's works, or how they coast given that they don't need to be kept spinning to avoid stalling.

It's nothing fancy.  The car's control system reverses the function of the traction motor, which is connected to the wheels and spins at the same speed, so it acts as an alternator.  Doing so creates electrical resistance, which is felt as mechanical resistance to the motor rotor turning.  That causes it to act as a brake; the car slows down and generates electricity at the same time.  
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.  

itsmeagain

Jenni_D said:

Herzlos 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?

Do EV's recover the energy via the motor of via some kind of hub device?

It's all in the physics ... if the motor becomes a generator then it converts kinetic energy into electrical energy. (The other way round when working as a motor is converting electrical energy into kinetic energy). Therefore it will appear as a "braking load" on the vehicle (the energy conversion has to have an effect, otherwise we're in the realms of perpetual motion); if the braking load is greater than the inertial force (e.g. mass of vehicle and slope of the road) then the vehicle will slow down, otherwise the speed will either remain constant or its acceleration (very steep hill) will be !!!!!!.

Thanks Jenni. I'm wondering when someone will mention a great perpetual motion idea or the windmill on the roof!

To add to the Jenni comments, when the car's in use, there's really only any point of charging the EV battery when you need to brake. Pressing the brake pedal can provide 'charging/generator braking' rather than direct wheel braking, but could you tell the difference? Any other EV charging condition is not for free, extremely inefficient, and a meaningless challenge to produce motor torque whilst charging at the same time.

itsmeagain

ontheroad1970 said:

itsmeagain said:

ontheroad1970 said:

itsmeagain said:

ontheroad1970 said:

I don't see how locking the wheels is a desirable thing at all, what with ABS and all.

Just to clarify, no one said that it was desirable to lock-up the wheels. I was saying that "modern braking systems are perfectly capable of locking the wheels". I.e, modern brakes are more than capable of achieving maximum braking, without the additional support of engine braking to do so.

The question... why would additional 'in gear' engine braking make the car stop quicker than using a modern braking system alone? I.e, "with ABS and all"

You think it will be safer with switched off engines?  You seem to be all for them.  So all electrics disengaged, an extra step to take to react to an unpredictable incident, or a predictable incident with an inattentive driver.  Of course those that want to lessen the safety protections are always 100% safe and attentive with eyes all over their heads so they never miss a thing.  

Back in the real world, all drivers get inattentive from time to time, some more than others.  Id rather that other drivers weren't turning their ignition off, with less power being supplied to the bakes through servo systems etc.  

The reference to locking brakes being desirable was inferred by your comment try comprehending what you write.

It will not be safer with automated switched off engines (stop on the move), but it will not be less safe. I do not propose that drivers switch off/on the engine themselves during coasting.

The electrics would not be switched off during an automated coasting engine stop. As mentioned earlier, the full benefits of such systems will not be seen until beltless engines. There are already engines will electric brake pumps, PAS, AC, ISG's etc without the need for the engine to turn to power what were traditionally ancillary belted items. Whether the driver is attentive or not makes no difference to what automated system is used. Cars are becoming safer and safer with these automated systems.

As you say, you inferred something from what I wrote. Try comprehending what you read rather than being so presumptuous.

Again... what is the benefit of 'in-gear' engine braking in the case of emergency braking when the brakes alone are more than capable of locking the wheels. For clarity - this should not be misinterpreted as me claiming that it's desirable to lock up the wheels! However... it will emerge in later posts that ABS does cycle between locking/partially locking the wheels and unlocking them...

Read this paragraph again.  You are definitely inferring, intentionally or otherwise that the brakes locking the wheels is fine in line with cadence braking which is a method of keeping steering while braking:

"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?"

As I say, I would not like to see safety systems bypassed.  It might be a minute amount of difference, but it can be life changing.  Also cadence braking is a particular braking skill and should not be advocated blindly.  You don't always have the time to pump the brakes.  The brakes locking the wheels would not be a good thing on a twisty downhill road.  

We are getting into semantics here but I think you mean that I was 'implying'.
You simply assumed something that I never wrote, put 2 & 2 together and made 5.

If you still think that I implied something - sorry for misleading you!

However.... as mentioned in a previous post, you will see later that ABS wheel locking/partial locking and releasing maybe a good thing in helping braking anyway.

neilmcl

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.