Double de-clutching going up the box
Discussion
I remember watching my uncle drive when I was kid and he would double de-clutch when changing up, I asked him why he did it, he said it made for smoother changes, sometimes I find myself doing it and I must admit it does seem smoother.
Am I fooling myself or is there some logic to it?.
Am I fooling myself or is there some logic to it?.
Yung Man said:
I remember watching my uncle drive when I was kid and he would double de-clutch when changing up, I asked him why he did it, he said it made for smoother changes, sometimes I find myself doing it and I must admit it does seem smoother.
Am I fooling myself or is there some logic to it?.
Nope, it's the same theory as ddc(ing) going down the box. Am I fooling myself or is there some logic to it?.
M
With a good modern synchromesh gearbox DDC is not needed, but I still think it can be helpful if it is done properly; and of course if your car has a crisp and sporty exhaust note it sounds nice.
I would only use it for down changes though, I've never seen the merit of doing it on up changes.
Best wishes all,
Dave.
I would only use it for down changes though, I've never seen the merit of doing it on up changes.
Best wishes all,
Dave.
The reason it makes your upchanges smoother is because double de-clutching forces you to take longer changing gear. Not much longer, but sufficient to smooth out the gearchange considerably.
It isn't necessary at all if you've a modern synchro gearbox, but consciously changing from a lower gear, into neutral with a slight (very slight) pause, and then into a higher gear is a smoother technique than just going straight from one gear to the next.
It isn't necessary at all if you've a modern synchro gearbox, but consciously changing from a lower gear, into neutral with a slight (very slight) pause, and then into a higher gear is a smoother technique than just going straight from one gear to the next.
R_U_LOCAL said:
The reason it makes your upchanges smoother is because double de-clutching forces you to take longer changing gear. Not much longer, but sufficient to smooth out the gearchange considerably.
It isn't necessary at all if you've a modern synchro gearbox, but consciously changing from a lower gear, into neutral with a slight (very slight) pause, and then into a higher gear is a smoother technique than just going straight from one gear to the next.
Even though I don't DDC on an up change, I think I do pause briefly in neutral before going to the next gear, although your observations and recollections of 4 May could dispute this.It isn't necessary at all if you've a modern synchro gearbox, but consciously changing from a lower gear, into neutral with a slight (very slight) pause, and then into a higher gear is a smoother technique than just going straight from one gear to the next.
BTW, hello Reg - things OK with you?
Best wishes all,
Dave.
Yung Man said:
I remember watching my uncle drive when I was kid and he would double de-clutch when changing up, I asked him why he did it, he said it made for smoother changes, sometimes I find myself doing it and I must admit it does seem smoother.
Am I fooling myself or is there some logic to it?.
Perhaps I should have said on the up change you don't blip the throttle.Am I fooling myself or is there some logic to it?.
Given a synchro box I think DDC is actually unhelpful.
More important to dip the clutch (way up or down) and try to match engine revs to road speed for the new gear prior to letting the clutch up.
I can DDC perfectly well. But I just don't see the point when I can get the gear changes as smooth without it.
More important to dip the clutch (way up or down) and try to match engine revs to road speed for the new gear prior to letting the clutch up.
I can DDC perfectly well. But I just don't see the point when I can get the gear changes as smooth without it.
Don said:
Given a synchro box I think DDC is actually unhelpful.
More important to dip the clutch (way up or down) and try to match engine revs to road speed for the new gear prior to letting the clutch up.
I can DDC perfectly well. But I just don't see the point when I can get the gear changes as smooth without it.
Interestingly quicker upchanges in the Caterham can well be smoother. This is assuming you are driving it using the sweet-spot revs (say 3.5-6.5). When you change up, if you let the revs drop too much toward tickover (happens quite quickly), you have to raise the revs to rev match. It's not very easy to get right (smooth). So the easier technique is a fast change (the caterham 6-spdr loves 'em) catching the revs before they have dropped.More important to dip the clutch (way up or down) and try to match engine revs to road speed for the new gear prior to letting the clutch up.
I can DDC perfectly well. But I just don't see the point when I can get the gear changes as smooth without it.
Also slow gear-changes in the Radical are a disaster, but that's prob too OT!
Bert
PS nothing to do with double-de-clutching!
Don said:
Given a synchro box I think DDC is actually unhelpful.
More important to dip the clutch (way up or down) and try to match engine revs to road speed for the new gear prior to letting the clutch up.
I can DDC perfectly well. But I just don't see the point when I can get the gear changes as smooth without it.
It does help spin the gearbox up so that no drag is placed on the wheels when selecting the gear. I can't see this being noticeable in a big heavy car with synchro, but it might be - depends on relative weight of car to inertia of gearbox. I can't see why you'd want to accelerate the gearbox on a downchange, but More important to dip the clutch (way up or down) and try to match engine revs to road speed for the new gear prior to letting the clutch up.
I can DDC perfectly well. But I just don't see the point when I can get the gear changes as smooth without it.
Rev matching helps with the clutch plate rather than gear selection interface - they are different issues in the gear-changing process.
My DDC isn't perfect like Don's but I do practice it as it can be helpful in unfamiliar cars where the weight of the flywheel and gearbox are unknown.
R_U_LOCAL said:
The reason it makes your upchanges smoother is because double de-clutching forces you to take longer changing gear. Not much longer, but sufficient to smooth out the gearchange considerably.
It isn't necessary at all if you've a modern synchro gearbox, but consciously changing from a lower gear, into neutral with a slight (very slight) pause, and then into a higher gear is a smoother technique than just going straight from one gear to the next.
Amen...It isn't necessary at all if you've a modern synchro gearbox, but consciously changing from a lower gear, into neutral with a slight (very slight) pause, and then into a higher gear is a smoother technique than just going straight from one gear to the next.
BOF
7db said:
My DDC isn't perfect like Don's
That isn't quite what I meant and you know it... 
I suppose the more precise English might have been "I can DDC well enough".
Still haven't found a car that I can make smoother changes in using the technique than simply doing my best to rev match. But there you go...if I found one with a really crunchy geabox I might give it a go...Mark Hales advocates DDC combined with H&T on the way down but have you seen what he usually races in? Nick Mason's classic collection...etc etc
BTW: Clearly Mr Hales is the superior driver. No bones about that - just that I don't drive cars that need DDC in either direction.
Yung Man said:
Yung Man said:
I remember watching my uncle drive when I was kid and he would double de-clutch when changing up, I asked him why he did it, he said it made for smoother changes, sometimes I find myself doing it and I must admit it does seem smoother.
Am I fooling myself or is there some logic to it?.
Perhaps I should have said on the up change you don't blip the throttle.Am I fooling myself or is there some logic to it?.
I think it's more important to upshift at the speed most appropriate for the car, i.e. time the shift from declutch to clutch so that the engine speed matches road speed when completed. Cars with light flywheels will feel happier with a faster shift...
Late to this (apologies if it's done to death) but I've always considered it to have several key advantages:
- it's pleasing
- it allows you to better match the speed of gearbox internals (ie. lay shaft)
- it reinforces a discipline that will reduce clutch wear, bearing in mind that the clutch is almost always the weak link in the drivetrain of any powerful car.
Some, thinking of circuit driving, will say it's an unnecessary waste of time but, unless you've run out of other ways to go quicker, I can't see it...
http://www.youtube.com/watch?v=RUbO3-jdGsk
As an aside, I (with some help from my friends) managed to wear out the gearbox on this car (crown wheel and pinion specifically) but the clutch showed no signs of wear or scorching.
WilliBetz
- it's pleasing
- it allows you to better match the speed of gearbox internals (ie. lay shaft)
- it reinforces a discipline that will reduce clutch wear, bearing in mind that the clutch is almost always the weak link in the drivetrain of any powerful car.
Some, thinking of circuit driving, will say it's an unnecessary waste of time but, unless you've run out of other ways to go quicker, I can't see it...
http://www.youtube.com/watch?v=RUbO3-jdGsk
As an aside, I (with some help from my friends) managed to wear out the gearbox on this car (crown wheel and pinion specifically) but the clutch showed no signs of wear or scorching.
WilliBetz
WilliBetz said:
Some, thinking of circuit driving, will say it's an unnecessary waste of time but,
I still don't understand the reason for DDC while changing UP. Friction within the gearbox is working in your favour, and unless there's something wrong with the box I don't see why the synchros would have any trouble matching speed for you. Even non-synchro boxes can change up cleanly without DDC in most cases. If you're ever going to have trouble beating the synchro it's going to be when changing down, because here friction is working against you.
It seems to me that using DDC just for the heck of it may be satisfying because of the extra skill and concentration required, but that doesn't mean it's sensible or going to make you any faster or increase the life expectancy of the transmission.
GreenV8S said:
WilliBetz said:
Some, thinking of circuit driving, will say it's an unnecessary waste of time but,
I still don't understand the reason for DDC while changing UP. Friction within the gearbox is working in your favour, and unless there's something wrong with the box I don't see why the synchros would have any trouble matching speed for you. Even non-synchro boxes can change up cleanly without DDC in most cases. If you're ever going to have trouble beating the synchro it's going to be when changing down, because here friction is working against you.
It seems to me that using DDC just for the heck of it may be satisfying because of the extra skill and concentration required, but that doesn't mean it's sensible or going to make you any faster or increase the life expectancy of the transmission.
DDC (sustained throttle) as a technique works well across a broad range of cars. As I am occasionally invited to drive different cars, sometimes unfamiliar ones and sometimes quickly, I like the technique because it doesn't depend on me guessing the effect of inertia or flywheel to effect a smooth change. The alternative wouldn't be so satisfying, as sympathetic or meaningfully quicker.
Edited by WilliBetz on Saturday 30th June 15:38
WilliBetz said:
I think the satisfaction of a decent DDC shift is simply that it's sympathetic and crisp. Once habitual, it requires no concentration.
DDC (sustained throttle) as a technique works well across a broad range of cars. As I am occasionally invited to drive different cars, sometimes unfamiliar ones and sometimes quickly, I like the technique because it doesn't depend on me guessing the effect of inertia or flywheel to effect a smooth change. The alternative wouldn't be so satisfying, as sympathetic or meaningfully quicker.
Mastering any difficult skill is satisfying, but I still don't understand what tangible benefit there is from using DDC when changing up. It just increases the workload on the driver and makes the gear change longer for no good reason that I can see. DDC (sustained throttle) as a technique works well across a broad range of cars. As I am occasionally invited to drive different cars, sometimes unfamiliar ones and sometimes quickly, I like the technique because it doesn't depend on me guessing the effect of inertia or flywheel to effect a smooth change. The alternative wouldn't be so satisfying, as sympathetic or meaningfully quicker.
If you had a car with a gearbox that was very slow to match revs and an engine that could change revs quicker than the gearbox then I could see a case for it - I understand many vintage cars and trucks were like this and required DDC on almost every gear change. But that's not something you're going to find on any modern car.
If there's ever going to be a case for DDC it would be on down shifts, and even then only when you were beating the synchros. For example I find it helps on mine when the 'box is hot and I'm trying to cover a big rev change.
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