In full-on What Car? mode, I was reading about the new DSGs which have a "Gliding Function".

"Gliding function automatically disengages the clutch when foot is taken off the accelerator. Activation/Deactivation controlled via the MFD. (Only available on 1.4 TSI 122PS DSG, 2.0 TDI 140PS DSG and 2.0 TDI 170PS DSG engines)"

er, so no engine braking AT ALL, then?

Sounds hideous

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139.0001BHP on supermarket UL, glovebox open, hood down.

Very interesting feature whenever the brakes fail

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Pilouil
Citroen C3 1.4 HDI 69.0424 bhp

Hasn't the porsche cayenne had this for years?
It's filtering down to the crap cars now.

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I think the Porsche Cayenne has only had auto boxes (tiptronic or whatever they're called), no DSG.

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Pilouil
Citroen C3 1.4 HDI 69.0424 bhp

They'll be a nasty mid corner surprise in yer FWD scrabbler.

Isn't that worse for fuel consumption? I thought it was better to decelerate with drive engaged as no fuel is used as opposed to having drive disconnected where fuel is needed to keep the engine idling.

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NotoriousREV said...

Isn't that worse for fuel consumption? I thought it was better to decelerate with drive engaged as no fuel is used as opposed to having drive disconnected where fuel is needed to keep the engine idling.

Good point - typically modern cars cut the fuel injection when not accelerating, which is not possible if the clutch is not engaged (in which case injection must be maintained otherwise the engine will stall...)
This being said they may have invented a new complex software pretending to optimise depending on the situation (just to offer the opportunities of unknown bugs and malfunctions).

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Pilouil
Citroen C3 1.4 HDI 69.0424 bhp

I saw this, massive marketing ploy IMO.

99% of people will think this saves more fuel.

at motorway speeds it actually works since the drivetrain losses from engine breaking are greater than just leaving it in neutral as shown by the emissions rating.

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Mito Man said...

at motorway speeds it actually works since the drivetrain losses from engine breaking are greater than just leaving it in neutral as shown by the emissions rating.

How though? If fuel injection is cut there are no emissions - just more deceleration compared to coasting.

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Invisible Speakers

I reckon it's just purely the fact that you can coast for longer before giving it a touch of throttle to maintain speed.
In reality it wouldn't work for me though since I keep my foot on the gas to maintain a constant speed but that's how you have to drive to save fuel and that's the way they do it when they do those official co2 and fuel consumption figures.

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Yes. It's definitely a gimmick to help preserve forward momentum with the marketing spin of better mpg.

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Mitofvck, you don't half talk some bollox. You expect engine braking when you lift. At motorways speeds you should have constant throttle, no one applies throttle to 70mph then lifts off and reapplied throttle when they slow.

The Ampera doesn't have engine braking obviously, and after a day or so it becomes natural. Going back to "normal cars" seem like they're slamming the brakes on even if you so much as lift.

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I remember reading a review on it (can't remember if it was evo or autocar) and they said that it did improve fuel consumption but gave the car a really irritating fake lag as it would freely rev then kick in. Another one of these perfect in theory/ looks good on consumption reports but is balls in real life

mcmurtm said...

I remember reading a review on it (can't remember if it was evo or autocar) and they said that it did improve fuel consumption but gave the car a really irritating fake lag as it would freely rev then kick in. Another one of these perfect in theory/ looks good on consumption reports but is balls in real life

About which the manufacturer cares not a jot, as long as it reduces the 'official' co2 figures, same as stop-start.

Orange Cola said...

Mitofvck, you don't half talk some bollox. You expect engine braking when you lift. At motorways speeds you should have constant throttle, no one applies throttle to 70mph then lifts off and reapplied throttle when they slow.

You've never been in a taxi or sat in a car with many friends while they were driving or used cruise control while driving behind other cars on the motorway have you?

If you do one of the above you notice a fvck load of people do that. Accelerate for a few seconds, lift off for a few seconds, repeat.

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It really depends what the situation is. Braking down to a junction or traffic lights? Yes, keep the clutch engaged so you don't waste fuel turning the engine over. However, as MitoChild correctly points out, to lift the accelerator on the motorway it 'wastes' more energy turning the engine over at say 3000rpm for a bit, along with the associated engine braking, than to have the car idle with the clutch disengaged (thus you coast for further).

I just hope the ECU is programmed to engage the clutch again when braking, for the best-of-both-worlds situation, mpg wise.

But if I'm lifting off on the motorway it's because I want to slow down, not coast.

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Net result: consumption of pads and disks instead of fuel.

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139.0001BHP on supermarket UL, glovebox open, hood down.