double (de)clutching.... what exactly is this?

[GreenV8S]

PE4rocks said:

I would disagree.

All the benefits you mention are the result of rev matching, not DDC. Unless you have a particular reason not to use the synchros, for example you have a gearbox without working synchros, I see no good reason to spend the extra time and attention that DDC requires compared to an ordinary gear change.

[Yung Man]

PE4rocks said:

TripleS said:

In general DDC always was less necessary on upchanges than on downchanges, and of course the need for the latter is now largely confined to very old classic or vintage vehicles.

Best wishes all,
Dave.

I would disagree. Using a DDC on, for instance, an approach to a hazard, say a roundabout, allows the engine revs to stay higher and more in the power band. It would be , therefor, more responsive when accelerating through the hazard.( I am talking an empty(ish) road and making progress scenario here.)



I am an old fart,

I'm with you on this one but the people on here profess to know better than us, what do old farts know?.

http://www.telegraph.co.uk/motoring/main.jhtml?xml...

http://www.bmwworld.com/models/config/m3_smg.htm



"The new SMG II gearbox has these features and benefits:"
"When downshifting, the engine will automatically double-declutch.

http://germancarscene.com/2006/07/27/porsche-devel...

http://www.acceleratebristol.com/carReviewsMain.as...


If you read these articles you will see that BMW PORSCHE and AUDI are producing gearboxs for the future that will double de-clutch for you.

These companies must be run by old farts like us, If a single de-clutch (rev match) is better than a double de-clutch no doubt they will soon realise their mistake, don't hold you breath thou.

[GreenV8S]

Yung Man said:

If a single de-clutch (rev match) is better than a double de-clutch no doubt they will soon realise their mistake, don't hold you breath thou.

If a double declutch gear change can be done accurately and consistently as quickly and easily as a single declutch change with no extra time or effort from the driver, then you have eliminated the disadvantages and stand to benefit from the advantages. I'm not familiar with the work you referred to but I suspect you'll find that these are automated gearboxes with all the timing and rev matching taken care of by an electronic control module. That's a very different kettle of fish to suggesting that drivers should pump the pedal twice during a manual gear change for no particular benefit.

[Yung Man]

GreenV8S said:

Yung Man said:

If a single de-clutch (rev match) is better than a double de-clutch no doubt they will soon realise their mistake, don't hold you breath thou.

If a double declutch gear change can be done accurately and consistently as quickly and easily as a single declutch change with no extra time or effort from the driver, then you have eliminated the disadvantages and stand to benefit from the advantages. I'm not familiar with the work you referred to but I suspect you'll find that these are automated gearboxes with all the timing and rev matching taken care of by an electronic control module. That's a very different kettle of fish to suggesting that drivers should pump the pedal twice during a manual gear change for no particular benefit.

Who's metaphorically stamping his feet now?, perhaps if you were as good as me at doing it you would find DDC alot easier.

[GreenV8S]

Yung Man said:

Who's metaphorically stamping his feet now?,

Not me.

Yung Man said:

perhaps if you were as good as me at doing it you would find DDC alot easier.

Presumably you think you are better at DDC than I am, and it may even be that you are. That doesn't mean that it is sensible to use this technique either for you or for other people. Of course it's entirely up to you to decide whether you do it, but if you're trying to argue that it is sensible to do this as a matter of course then I disagree.

In situations where DDC isn't actually required (i.e. where you have a normal synchro gearbox in good working order) a DDC gear change increases the time and effort required to change gear, and this is typically at a time that the driver is relatively busy and would normally seek to minimise the time that their hand, feet and mind are engaged with the gear change. DDC has disadvantages as well as advantages, and you should only apply it where appropriate. In the vast majority of cases it's simply not appropriate.

[Yung Man]

GreenV8S said:

Yung Man said:

Who's metaphorically stamping his feet now?,

Not me.

Yung Man said:

perhaps if you were as good as me at doing it you would find DDC alot easier.

Presumably you think you are better at DDC than I am, and it may even be that you are.

Sorry you misunderstand me, I was trying to be I meant "If you were as good at metaphorically stamping your feet as me".(good practice for DDC)
I would never be so presumptuous as to think I was better than anyone at DDC.

[PE4rocks]

GreenV8S said:

PE4rocks said:

I would disagree.

All the benefits you mention are the result of rev matching, not DDC. Unless you have a particular reason not to use the synchros, for example you have a gearbox without working synchros, I see no good reason to spend the extra time and attention that DDC requires compared to an ordinary gear change.

How does one revmatch without declutching? To be perfectly clear I SDC as opposed to DDC precisely because of the synchros but the benefits allow faster and smoother approach and acceleration from a hazard/obstacle.

To maximise engine braking effect, then use of the synchro, without revmatching is the way forward. If, however one uses this, particularly in the wet/ice/snow in a rear wheel drive car then the wheels can lose traction. Try it.

[PE4rocks]

Yung Man said:

These companies must be run by old farts like us, If a single de-clutch (rev match) is better than a double de-clutch no doubt they will soon realise their mistake, don't hold you breath thou.

Fair cop mate. I was young once, I invented this new thing, round it was...

[GreenV8S]

PE4rocks said:

How does one revmatch without declutching? To be perfectly clear I SDC as opposed to DDC precisely because of the synchros but the benefits allow faster and smoother approach and acceleration from a hazard/obstacle.

To maximise engine braking effect, then use of the synchro, without revmatching is the way forward. If, however one uses this, particularly in the wet/ice/snow in a rear wheel drive car then the wheels can lose traction. Try it.

The thread is about double declutching (and you mentioned the term in your post too). The benefits you referred to all come from the rev matching, not from DDC. You can match revs without double declutching; just do an ordinary ('single declutch') gear change and match revs using the throttle before engaging the clutch.

The only reason I can see for DDC is to solve the problem of getting the gearbox internals to the correct speed before selecting the next gear. Synchros solve this problem for you, so you can ignore it if you have an ordinary modern gearbox in good working order.

[GreenV8S]

Yung Man said:

Sorry you misunderstand me, I was trying to be I meant "If you were as good at metaphorically stamping your feet as me".(good practice for DDC)
I would never be so presumptuous as to think I was better than anyone at DDC.

That wooshed straight overhead, very good!

[BertBert]

Yung Man said:

http://www.bmwworld.com/models/config/m3_smg.htm



"The new SMG II gearbox has these features and benefits:"
"When downshifting, the engine will automatically double-declutch.

Mmm, didn't read the rest of the links, but I wouldn't consider that a "definitive source". It's not even by the manufacturer! I thought that cutting edge in clever gearboxes was two clutches and certainly not DDC!

It made me smile!

Bert