Automatic gearbox and regular use of neutral

fred990

shinytop said:

itsmeagain said:

Here's an easy to understand 'pre-selected' shift schedule map for a 4 speed auto.
Later control functions would more likely be a function of torque request, sometimes using modelled characteristic lines etc. They may also have offset/compensation maps for other noise factors to 'skew' the shift points for things like altitude, various temperatures etc, and In the case of VW, if it detects that it's performing an emissions test - just kidding (not)!
Note that with no throttle, a high gear is auto selected if you were to select N to D at any appreciable speed.
From 50-140Kph, if you open the throttle, the gear shifts down for a lower gear, increases engine speed and therefore more power.

It's good to see somebody who seems to have some real knowledge rather than the usual 'expert' opinions seen here. 

BINGO in one! Exactly my thought on reading his first post and yet along comes someone who think they knew better.....not!

[Deleted User]

Far rather the code for braking is left as it is. Cars may be more capable but someone busy texting still need thinking time. When they look up that is and see the problem. I mean, they hardly have time to book face the crash they are about to be in.

itsmeagain

fred990 said:

shinytop said:

itsmeagain said:

Here's an easy to understand 'pre-selected' shift schedule map for a 4 speed auto.
Later control functions would more likely be a function of torque request, sometimes using modelled characteristic lines etc. They may also have offset/compensation maps for other noise factors to 'skew' the shift points for things like altitude, various temperatures etc, and In the case of VW, if it detects that it's performing an emissions test - just kidding (not)!
Note that with no throttle, a high gear is auto selected if you were to select N to D at any appreciable speed.
From 50-140Kph, if you open the throttle, the gear shifts down for a lower gear, increases engine speed and therefore more power.

It's good to see somebody who seems to have some real knowledge rather than the usual 'expert' opinions seen here. 

BINGO in one! Exactly my thought on reading his first post and yet along comes someone who think they knew better.....not!

Thanks....
It's not often that my specialist subject of the last 35 years comes up. It's made me realise that you can't always trust what people say in these forums. Anyone can write whatever they want on here with no expertise whatsoever. If I wasn't one of the world's technical specialists on this subject - I may even believe some of this rubbish myself.

Advocado

@itsmeagain - as you clearly know what you're talking about, could you just confirm - will I damage my van if I regularly move from D to N and back to D whilst driving at speed?

Thanks.

fred990

itsmeagain said:

fred990 said:

shinytop said:

itsmeagain said:

Here's an easy to understand 'pre-selected' shift schedule map for a 4 speed auto.
Later control functions would more likely be a function of torque request, sometimes using modelled characteristic lines etc. They may also have offset/compensation maps for other noise factors to 'skew' the shift points for things like altitude, various temperatures etc, and In the case of VW, if it detects that it's performing an emissions test - just kidding (not)!
Note that with no throttle, a high gear is auto selected if you were to select N to D at any appreciable speed.
From 50-140Kph, if you open the throttle, the gear shifts down for a lower gear, increases engine speed and therefore more power.

It's good to see somebody who seems to have some real knowledge rather than the usual 'expert' opinions seen here. 

BINGO in one! Exactly my thought on reading his first post and yet along comes someone who think they knew better.....not!

Thanks....
It's not often that my specialist subject of the last 35 years comes up. It's made me realise that you can't always trust what people say in these forums. Anyone can write whatever they want on here with no expertise whatsoever. If I wasn't one of the world's technical specialists on this subject - I may even believe some of this rubbish myself.

It was instantly obvious to me. The trouble with the prolific posters is becoming a self appointed expert who couch their opinions as facts! They always seem to make statements. Nobody knows that much! 

itsmeagain

Advocado said:

@itsmeagain - as you clearly know what you're talking about, could you just confirm - will I damage my van if I regularly move from D to N and back to D whilst driving at speed?

Thanks.

On the latest gearboxes that I have worked on, the answer in 'no damage', but I simply don't know about yours. Do you know exactly what box it is, and I can ask my transmission development colleagues? My expertise is on IC engine control strategies that talk to the trans ECU over network interfaces. I'm not an expert on the mechanical side of the trans. If you ask anyone other than the expert, they will automatically tell you not to do it.

I did what you do on many of my premium management cars, but I never had one for more than 10,000 miles!

born_again

Advocado said:

@itsmeagain - as you clearly know what you're talking about, could you just confirm - will I damage my van if I regularly move from D to N and back to D whilst driving at speed?

Thanks.

Transmission spinning fast V engine ticking over... Massive difference in speed. What do you think this is going to do to a auto gearbox. Especially if it's a DCT.

Jenni_D

Does the OP "blip" the throttle when switching back to D? (Same as you'd do in a manual if dropping down gears to e.g. make an overtake - you'd blip the throttle to align the revs to the trans speed).

lemondrops69

Jenni_D said:

Does the OP "blip" the throttle when switching back to D? (Same as you'd do in a manual if dropping down gears to e.g. make an overtake - you'd blip the throttle to align the revs to the trans speed).

How would you even know what the correct rpm would be to align the engine to the trans, you've no clue what the trans rpm is? Just 'blipping' it might increase it too much or not enough?

If the auto box is a planetary with a torque convertor and you coast in N you'll almost definitely wear the clutch packs out quicker

neilmcl

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.