DSG coasting in Eco mode

[fj604]

When my foot is off accelerator in Eco mode, the Maxidot will show "Coasting" and I see that RPM stays at idle (about 800) until I press either brake or accelerator pedal, so it seems that the clutch is disengaged.

 

According to Highway Code:

https://www.gov.uk/guidance/the-highway-code/general-rules-techniques-and-advice-for-all-drivers-and-riders-103-to-158

 

Rule 122

Coasting. This term describes a vehicle travelling in neutral or with the clutch pressed down. It can reduce driver control because

• engine braking is eliminated
• vehicle speed downhill will increase quickly
• increased use of the footbrake can reduce its effectiveness
• steering response will be affected, particularly on bends and corners
• it may be more difficult to select the appropriate gear when needed.

 

Question 1: does this rule somehow not apply to DSG or any other vehicle with automatic transmission?

Question 2: does this actually save fuel?

 

[Gromle]

Im quite sure it can save fuel on the right roads.

I have a route i drive often were i can Coast for kilometers. In gear the enginebraking slows me down too much. But I doubt it saves much fuel...

[Phil-E]

No it doesn't apply to an automatic vehicle as should the need arise the clutch is re-engaged quickly and automatically and with it not being a conventional clutch or one that can be in any way controlled by the driver it doesn't apply.

 

And yes it can save fuel in certain driving conditions. Obviously the benefit being that driving on flat or slight down hill sections you can travel further without loosing momentum and only a small amount of fuel is used to maintain engine idle speed.

 

Phil

Edited 26 January, 2016 by Phil-E

[FelisBengalensis]

When I used 'Eco' my fuel economy actually got worse as modern engines use complete fuel cutoff on the overrun. That and the appalling ride were enough to say that it's really a gimmick rather than something of any real use. Never used it again.

[Phil-E]

Like I say under the right conditions etc then it could see an improvement. However most of the time it's better to have engine braking when approaching a set of traffic lights or roundabout, use no fuel at all and save on having to use the brakes. And quite often when going down hill you want some engine braking.

 

The occasions where it will actually save fuel are quite limited.

 

I liked a Toyota Yaris Hybrid that I drove once. If you just had it in D you would get no engine braking and it would just coast but then there was a separate position on the gear stick labelled "B" and would behave the same as D but instead provide some engine braking (using the motor as regenerative braking) so you could just choose as you went along and anticipate if you were going to need some engine braking or not.

[philsmith]

You can easily turn the coasting on or off by either a quick blip on the throttle or the brake.

I like the smoothness and quietness when in coast mode and in my experience the mpg is better.

btw When you have the cruise control on, even if it is in eco, you do not get coasting

[GaSelle]

Like I say under the right conditions etc then it could see an improvement. However most of the time it's better to have engine braking when approaching a set of traffic lights or roundabout, use no fuel at all and save on having to use the brakes. And quite often when going down hill you want some engine braking.

 

The occasions where it will actually save fuel are quite limited.

 

I liked a Toyota Yaris Hybrid that I drove once. If you just had it in D you would get no engine braking and it would just coast but then there was a separate position on the gear stick labelled "B" and would behave the same as D but instead provide some engine braking (using the motor as regenerative braking) so you could just choose as you went along and anticipate if you were going to need some engine braking or not.

Almost true. It does brake in D, but not much. You can see, that it´s regenerating power if you lift your foot of the accelerator (Have a Yaris Hybrid myself)

[Phil-E]

Ah right... it felt like there was no braking! lol I only drove it about 30 miles and didn't have the car display up on the stereo so couldn't see what it was doing.

 

I did also drive it a few weeks later a couple of miles most of which was down hill and the engine never kicked in even sat waiting at the traffic lights.

 

Quite enjoyed it actually. Nice and quite and the challenge of keeping the needle down and the engine off was good!