Automatic gearbox and regular use of neutral

BOWFER

Mark_in_Kent said:

BTW there is a costing setting on the settings/driver convenience menu, have you tried changing that?

Interesting, never heard of this before.
Peculiar to the vans for some reason?

Jenni_D

A Passat is a van? Who knew!  

The_Fat_Controller

Engaging D from N whilst moving is never a good idea.

itsmeagain

BOWFER said:

itsmeagain said:

BOWFER said:

Advocado said:

BOWFER said:

So when using neutral, you're not coming to a stop before putting it back into D?
If you're putting it from neutral back into 'D' at any speed, the gearbox simply wasn't designed for this at all and entirely at your own risk.

Correct.  D to N to D multiple times at various speeds. 

The DSG's whole 'thing' is that it's programmed to predict what will happen next.
So if you're in third and accelerating it predicts you're going to want fourth next and already has fourth pre-selected.
When the engine is idling in neutral, it's going to think you want first or reverse next, it's not going to expect you to suddenly need second/third/fourth or whatever (depending what speed you're doing).
Like I said, not designed to do this at all and perhaps only luck it's not gone bang already.
It's like asking if my iphone is OK to be repeatedly dropped just because I've been getting away with it for years.

Having developed that simulink/matlab models for this, there is no 'guessing' what the customer is going to attempt next. There's different scheduling loops in the software ranging from 1ms to 1000ms interrupts and many of the engine control functions are synchronous.

I didn't use the word 'guess'
The next gear is pre-selected.

Sorry - correction - you claimed that an engine 'thinks' ahead (guessing). No gear is 'pre-selected' until it is actually requested, then it's actuated - most of these things are in the 10-20ms interrupt.

BOWFER

itsmeagain said:

BOWFER said:

itsmeagain said:

BOWFER said:

Advocado said:

BOWFER said:

So when using neutral, you're not coming to a stop before putting it back into D?
If you're putting it from neutral back into 'D' at any speed, the gearbox simply wasn't designed for this at all and entirely at your own risk.

Correct.  D to N to D multiple times at various speeds. 

The DSG's whole 'thing' is that it's programmed to predict what will happen next.
So if you're in third and accelerating it predicts you're going to want fourth next and already has fourth pre-selected.
When the engine is idling in neutral, it's going to think you want first or reverse next, it's not going to expect you to suddenly need second/third/fourth or whatever (depending what speed you're doing).
Like I said, not designed to do this at all and perhaps only luck it's not gone bang already.
It's like asking if my iphone is OK to be repeatedly dropped just because I've been getting away with it for years.

Having developed that simulink/matlab models for this, there is no 'guessing' what the customer is going to attempt next. There's different scheduling loops in the software ranging from 1ms to 1000ms interrupts and many of the engine control functions are synchronous.

I didn't use the word 'guess'
The next gear is pre-selected.

Sorry - correction - you claimed that an engine 'thinks' ahead (guessing). No gear is 'pre-selected' until it is actually requested, then it's actuated - most of these things are in the 10-20ms interrupt.

The next gear being pre-selected is used in lots of bumf about DSG, in fact every article I've just read uses the term.
Go correct them.

itsmeagain

BOWFER said:

itsmeagain said:

BOWFER said:

itsmeagain said:

BOWFER said:

Advocado said:

BOWFER said:

So when using neutral, you're not coming to a stop before putting it back into D?
If you're putting it from neutral back into 'D' at any speed, the gearbox simply wasn't designed for this at all and entirely at your own risk.

Correct.  D to N to D multiple times at various speeds. 

The DSG's whole 'thing' is that it's programmed to predict what will happen next.
So if you're in third and accelerating it predicts you're going to want fourth next and already has fourth pre-selected.
When the engine is idling in neutral, it's going to think you want first or reverse next, it's not going to expect you to suddenly need second/third/fourth or whatever (depending what speed you're doing).
Like I said, not designed to do this at all and perhaps only luck it's not gone bang already.
It's like asking if my iphone is OK to be repeatedly dropped just because I've been getting away with it for years.

Having developed that simulink/matlab models for this, there is no 'guessing' what the customer is going to attempt next. There's different scheduling loops in the software ranging from 1ms to 1000ms interrupts and many of the engine control functions are synchronous.

I didn't use the word 'guess'
The next gear is pre-selected.

Sorry - correction - you claimed that an engine 'thinks' ahead (guessing). No gear is 'pre-selected' until it is actually requested, then it's actuated - most of these things are in the 10-20ms interrupt.

The next gear being pre-selected is used in lots of bumf about DSG, in fact every article I've just read uses the term.
Go correct them.

The software and calibration pre-selects what will happen for any scenario depending on numerous variables / noise factors. That doesn't mean that it's already decided that it is going to go in 1st or reverse before D is selected (like you claimed).

There is a 'shift schedule' map calibrated. In it's simplest form, it's an x-y table of pigeon holes containing pre-selected gears to use (as a function of road speed & torque request). That map/table will NOT assign reverse or 1st at 50mph closed throttle! It will contain an appropriate gear that is 'looked-up' when D is selected.

basill

Does it have eco mode?   My skoda DSG would automatically coast in this mode on a closed throttle, reengaging drive instantly if brakes or accelerator touched.

Grumpy_chap

Maybe I missed something, but the idea seems odd.

Either you buy a manual, in which case you need to keep fiddling with your stick while driving.

Or you buy an automatic, in which case you simply slide the stick to D and then forget about it until you park.

The OP reports have an automatic and fiddling with their stick.

Advocado

neilmcl said:

Advocado said:

itsmeagain said:

Advocado said:

itsmeagain said:

It should not cause any damage to your gearbox but will wear your brakes out quicker (should you need them), and arguably dangerously delay your emergency use of accelerator (if required).

Interesting post - thanks for the info.  It's a diesel van.

I only put it into N when I know I won't need the brakes.  So I coast for a while if there's a long downward gradient and then into D again once the speed has dropped lower than I want.

Good to know it's not damaging anything.

Van - yes - aerodynamics of a bus!
That makes sense - you will get an improvement, I don't believe the size of the improvement that you claim though, don't believe you wouldn't increase speed in N on steep hills (would agree on gentle to moderate), some models (such as 2.0 DSG Superb) do this automatically for you.

So are you going to go the whole hog, switch the ign off and back on again whilst coasting?

I am a class 1 advanced and ROSPA gold driver and have never had an accident whilst practicing this - seen loads though!

No (I'd lose power steering etc?), just literally coast with the engine idling.

And therefore burning fuel.

Of course, but considerably less fuel than having to keep the engine engaged to keep momentum.

ontheroad1970

Advocado said:

neilmcl said:

Advocado said:

itsmeagain said:

Advocado said:

itsmeagain said:

It should not cause any damage to your gearbox but will wear your brakes out quicker (should you need them), and arguably dangerously delay your emergency use of accelerator (if required).

Interesting post - thanks for the info.  It's a diesel van.

I only put it into N when I know I won't need the brakes.  So I coast for a while if there's a long downward gradient and then into D again once the speed has dropped lower than I want.

Good to know it's not damaging anything.

Van - yes - aerodynamics of a bus!
That makes sense - you will get an improvement, I don't believe the size of the improvement that you claim though, don't believe you wouldn't increase speed in N on steep hills (would agree on gentle to moderate), some models (such as 2.0 DSG Superb) do this automatically for you.

So are you going to go the whole hog, switch the ign off and back on again whilst coasting?

I am a class 1 advanced and ROSPA gold driver and have never had an accident whilst practicing this - seen loads though!

No (I'd lose power steering etc?), just literally coast with the engine idling.

And therefore burning fuel.

Of course, but considerably less fuel than having to keep the engine engaged to keep momentum.

Yet idling is one of the most inefficient things you can do with an engine, no matter what your vehicle's in car computer tells you.