No i read this will be a common feature on all new autos. It maybe wasnt BMW now i think about it. It might have been the new range rover. Doesnt really matter which car it is, the point was that the car will effectively be coasting.

I think it probably does matter what car it is - I assume there is a difference for a 4x4 (depending at what point the drivetrain is disengaged) and this must be how they are able to do it.

Mr_Awol

Why do you think a car needs to be under acceleration or braking for stability reasons?

I am keen to hear your thoughts on this matter. Note the subject of vehicle stability and handling is a magnitude more complex than stalling an engine.

Simple scenario, please explain the difference in stability between these two:

1. Coasting down a hill in neutral and idle.

2. Driving down a hill in gear and maintaining a load on the engine that balances drag in such a way that speed is the same as coasting.

Not under acceleration - in gear.

Have you ever turned a corner in neutral? As in, above walking pace?

I think it probably does matter what car it is - I assume there is a difference for a 4x4 (depending at what point the drivetrain is disengaged) and this must be how they are able to do it.

Im now thinking it may have been Audi?? I will see if i can find the article.

Dont think it would matter if it was 4x4 or 2wd as coasting is coasting i.e no drive to any wheels.

The point being that the reason the car manufacturer has opted for the new auto box to do this "coasting" was to improve MPG and if coasting was so dangerous i doubt they would be allowed to for fear of being sued.

Im not sure if i would like my auto to fully disengage drive on the overun as surely you would feel it re-engage again when you applied throttle pressure. This may get annoying as would there not be a very slight delay? Modern autos are very clever though so i doubt BMW, Audi or range rover would fit a botch up job of an auto.

If i find out which manufacturer it was ill post it up.

Im now thinking it may have been Audi?? I will see if i can find the article.

Dont think it would matter if it was 4x4 or 2wd as coasting is coasting i.e no drive to any wheels.

The point being that the reason the car manufacturer has opted for the new auto box to do this "coasting" was to improve MPG and if coasting was so dangerous i doubt they would be allowed to for fear of being sued.

Im not sure if i would like my auto to fully disengage drive on the overun as surely you would feel it re-engage again when you applied throttle pressure. This may get annoying as would there not be a very slight delay? Modern autos are very clever though so i doubt BMW, Audi or range rover would fit a botch up job of an auto.

If i find out which manufacturer it was ill post it up.

Did a quick google and its the new BMW auto that disengages drive on engine overun. You get this on the new 3 series i think. I did find an article but it was massively long and very technical. Someone better at googling may be able to find and post something more specific.

I think it probably does matter what car it is - I assume there is a difference for a 4x4 (depending at what point the drivetrain is disengaged) and this must be how they are able to do it.

To uphold your (albeit weak) argument about coasting, it doesn't matter what car it is. You've said it's wrong, dangerous and not economical anyway.

Why would there be a difference for a 4x4? If the drivetrain is disengaged it's coasting.

I think the big issue with coasting is over reliance on the breaks. If your pads effectiveness suddenly falls off a cliff, your ability to stop the car in an emergency (at any time) is limited.

But the real discussion is: do you have full control over your vehicle while in motion. If not, get off the F*****g road.

Edited 22 November, 201213 yr by cs.rogers

But the real discussion is: do you have full control over your vehicle while in motion. If not, get off the F*****g road.

Define "full control" :|

Mr_Awol

Yes I have coasted around corners faster than walking speed. Many times in all sorts of vehicles. 2 wheeled and four. 2wd and 4wd. Including automatic vehicles which unlock the torque converter, drop back to idle and almost freewheel on over-run.

But again you haven't answered the question.

What is the difference stability wise between being in neutral and being in gear while not applying acceleration or braking?

To add to RainboFire's question.

If you think 4wd makes a difference, would this be a full-time 4wd system, a haldex clutch system or a viscous 4wd system? Please explain in detail using your knowledge of how these systems behave differently under drive, coast and engine braking.

If overheating the brakes is a concern. I can tell you that people routinely do that here while coasting downhill in gear. Mainly people from flat countries who don't know about changing down when driving down mountain passes. An automatic in drive offers no engine braking when you are driving at 50km/h on the brakes. Brakes get so hot they stop working.

I've even driven past a vehicle (I was going uphill) which was driving down one of those hills with smoke pouring out of it's brakes.

Most surprising is, these people still seem to get to where they are going. I'm sure they need a change of underwear though.

Did a quick google and its the new BMW auto that disengages drive on engine overun. You get this on the new 3 series i think. I did find an article but it was massively long and very technical. Someone better at googling may be able to find and post something more specific.

My limited googling skills suggest its just the hybrid, which makes sense per above.

But again you haven't answered the question.

I honestly don't think he can answer any of the questions that he's been asked, short of the use of Google. His "don't feed the trolls" comment is the norm for someone who can't deal with what's in front of him, so has to resort to a poor attempt at insults. Pretty much puts his opinion in the same arena as Jimmy Saville's opinion on child care.

There'll be some frantic back-peddling next.....

http://www.bmwusanews.com/newsrelease.do;jsessionid=C84A2CCD8E453927607F0AB611569C02?&id=820&mid=

"When the driver applies more throttle, the internal combustion engine is engaged automatically, then disengaged on overrun."

There's no mention of shutting down the fuel flow to the engine during this disengaged period. So either the engine is in idle or, er, er, some other "fuel saving" mode?

This is in a discussion about a hybrid. If the engine is disengaged, how much braking effect do you think an electric motor produces?

Remember this system which actively disengages the engine on overrun, is made by BMW. Not exactly a small name in the motoring world. ;)

I honestly don't think he can answer any of the questions that he's been asked, short of the use of Google. His "don't feed the trolls" comment is the norm for someone who can't deal with what's in front of him, so has to resort to a poor attempt at insults. Pretty much puts his opinion in the same arena as Jimmy Saville's opinion on child care.

There'll be some frantic back-peddling next.....

http://www.bmwusanews.com/newsrelease.do;jsessionid=C84A2CCD8E453927607F0AB611569C02?&id=820&mid=

"When the driver applies more throttle, the internal combustion engine is engaged automatically, then disengaged on overrun."

There's no mention of shutting down the fuel flow to the engine during this disengaged period. So either the engine is in idle or, er, er, some other "fuel saving" mode?

This is in a discussion about a hybrid. If the engine is disengaged, how much braking effect do you think an electric motor produces?

Remember this system which actively disengages the engine on overrun, is made by BMW. Not exactly a small name in the motoring world. ;)

Another mature post - almost as entertaining as your 'run away' nonsense earlier.

As for insults - I simply told you that whilst you were trolling I wasn't going to engage with you.

Another mature post - almost as entertaining as your 'run away' nonsense earlier.

As for insults - I simply told you that whilst you were trolling I wasn't going to engage with you.

Another epic fail to answer any of the questions put to you.

You won't engage, with either myself or Kiwibacon, because you can't actually backup your flimsy statements. We're expected to take what you write as gospel. When questioned, you shrivel up and ignore what you can't cope with.

My limited googling skills suggest its just the hybrid, which makes sense per above.

Its not the hybrid. Article i read was about 320d.