how effective is it??
Discussion
ok i have a question
scince i don't drive yet...i have a question about double (de)clutching
is there actualy any advantage to doing this??
does the car shift smoother or does it go faster?
and does the tranny last longer??
because i'm defainately getting a car with a manual tranny got my first car
i'm just wondering if double clutching has an advantage and if i should start leaning to drive like this now.
of course all of these questions refer to a synchronizing transmission...
thank you
scince i don't drive yet...i have a question about double (de)clutching
is there actualy any advantage to doing this??
does the car shift smoother or does it go faster?
and does the tranny last longer??
because i'm defainately getting a car with a manual tranny got my first car
i'm just wondering if double clutching has an advantage and if i should start leaning to drive like this now.
of course all of these questions refer to a synchronizing transmission...
thank you
There is little or no benefit in double-declutch gearchangeing on a modern car featuring, as they all do, a synchromesh gearbox.
If you want to drive with the greatest mechanical sympathy you need to learn to match engine revs to road speed with the accelerator before engaging the next gear. Depending on the throttle response of your car you may need to do this on upshifts as well as the more usual downshifts.
How to practice rev-matching.
Find a lovely long straight somewhere quiet. Travel along at a speed where the car is happy to be in either third (at higher revs) or fourth (at lower revs). Travel along in fourth.
Now change gear to third. If you just do this you will feel the car slow. This is called clutch-drag braking - and will destroy your clutch if you keep doing it. The aim of the exercise is to eliminate clutch drag braking. So..when you change to third, whilst the clutch is down, blip the accelerator to raise the engine revs - then let the clutch up on third.
If you get this totally right you will hear the revs change but you will not feel the change of gear.
Change back to fourth - you might need a tiny little throttle blip when you do this as when you disengage the clutch and take your foot off the accelerator revs will fall to tick over which will be too low for fourth.
Keep doing this until you can change from one gear to another with absolutely NO jerk whatsoever. Fourth to third. Third to fourth. Fourth to third. Third to fourth. etc.
OK. So now you know how much throttle blip you need from fourth to third. You can experiment with the other gears. Third to second. Fifth to fourth etc. Until you know exactly how much gas you need to smooth out the gearchange totally.
Once you can do this reliably you can then incorporate it into your driving.
e.g. Junction coming up. Brake. Lose speed until right for junction. Clutch down. Third to second, throttle blip, clutch up - now in second gear. Steer through junction. Accelerate away...
Its easier to do this rev matching if you use the IAM system and brake first, get your speed right, then change gear. If you get a car that has the right pedal setup and you have twinkle toes you can learn to brake with your right foot (with your toe) and throttle blip with your right foot (with your heel) so you can brake and change down (with a throttle blip) at the same time. This is called Heel and Toe - and you use your right foot to control two pedals at the same time. Not everyone can do it - and its not possible on all cars so try the brake first, then change gear method first.
If you want to drive with the greatest mechanical sympathy you need to learn to match engine revs to road speed with the accelerator before engaging the next gear. Depending on the throttle response of your car you may need to do this on upshifts as well as the more usual downshifts.
How to practice rev-matching.
Find a lovely long straight somewhere quiet. Travel along at a speed where the car is happy to be in either third (at higher revs) or fourth (at lower revs). Travel along in fourth.
Now change gear to third. If you just do this you will feel the car slow. This is called clutch-drag braking - and will destroy your clutch if you keep doing it. The aim of the exercise is to eliminate clutch drag braking. So..when you change to third, whilst the clutch is down, blip the accelerator to raise the engine revs - then let the clutch up on third.
If you get this totally right you will hear the revs change but you will not feel the change of gear.
Change back to fourth - you might need a tiny little throttle blip when you do this as when you disengage the clutch and take your foot off the accelerator revs will fall to tick over which will be too low for fourth.
Keep doing this until you can change from one gear to another with absolutely NO jerk whatsoever. Fourth to third. Third to fourth. Fourth to third. Third to fourth. etc.
OK. So now you know how much throttle blip you need from fourth to third. You can experiment with the other gears. Third to second. Fifth to fourth etc. Until you know exactly how much gas you need to smooth out the gearchange totally.
Once you can do this reliably you can then incorporate it into your driving.
e.g. Junction coming up. Brake. Lose speed until right for junction. Clutch down. Third to second, throttle blip, clutch up - now in second gear. Steer through junction. Accelerate away...
Its easier to do this rev matching if you use the IAM system and brake first, get your speed right, then change gear. If you get a car that has the right pedal setup and you have twinkle toes you can learn to brake with your right foot (with your toe) and throttle blip with your right foot (with your heel) so you can brake and change down (with a throttle blip) at the same time. This is called Heel and Toe - and you use your right foot to control two pedals at the same time. Not everyone can do it - and its not possible on all cars so try the brake first, then change gear method first.
rev matching is more rewarding in certain cars. Been driving today in my daughter's Rover 25 (eeek) which is a great fun car with its 1400 k series engine and 100bhp. However it is not that much fun to blip and match revs. The weight of the car and it being front wheel drive mean that the car doesn's really struggle to get the revs up on the downchange.
Im in it coz my TVR is in for servicing. Now that benefits greatly from the blip and rev matching and is so, so satisfying. I'm a bit sad as getting the blips right and using heal and toe is one (of the) thing(s) I really like on the road!
Graham
Im in it coz my TVR is in for servicing. Now that benefits greatly from the blip and rev matching and is so, so satisfying. I'm a bit sad as getting the blips right and using heal and toe is one (of the) thing(s) I really like on the road!
Graham
Don is spot on. And it will benefit any car. I can't see why a Rover would be unpleasant to do this in. My mum had a 16v one and it was very willing to rev. I even rev-match on the way up the gears - makes for a very smooth drive.
It is all about mechanical sympathy.
And to Spidy, it is never too early to get into good habits.
It is all about mechanical sympathy.
And to Spidy, it is never too early to get into good habits.
It's engine braking - not 'clutch-drag braking': just to get the mechanics right. If you want to hear it in action... listen to the MotoGP bikes - they have slipper clutches that automatically slip the clutch plates to prevent engine braking. You'll be able to hear the strange engine note into bends: kind of a rolling Weee-errr-weeee-errrr-weeee-eeeeeer.
Heel-toe is one of the most satisfying driving techniques - only just loses out to left-foot braking. Lots of fun in a 1.1 litre 106 when you have a SLK 55 AMG driving up your jacksie who then can't keep up on roundabouts... heh heh... I don't think he was too happy given how quickly he came up behind me after every a few years of every straight.
Heel-toe is one of the most satisfying driving techniques - only just loses out to left-foot braking. Lots of fun in a 1.1 litre 106 when you have a SLK 55 AMG driving up your jacksie who then can't keep up on roundabouts... heh heh... I don't think he was too happy given how quickly he came up behind me after every a few years of every straight.
MrKipling43 said:
It's engine braking - not 'clutch-drag braking': just to get the mechanics right.
No. It's not.
Engine braking is when you lift off the throttle. In lower gears you will get a powerful engine-braking effect. This is nothing to do with the clutch - its the engine compression that does it.
Clutch-drag braking occurs when you let the clutch up in a lower gear without rev matching. Engine revs do not match road speed, have to be raised, and the first thing that soaks up the engine's resistance is the clutch. Once the clutch is fully engaged then you are braking with the engine alone.
Clutch drag eats clutches over time. Its not apallingly bad for clutches - because most gear changes under braking are done at low revs.
In either case, however, you brake only the drive wheels - which leads to uneven braking that can destabilise the car. Hence the heel and toe or IAM methods. Of course - this does only matter from a "destabilising" point of view under hard braking - as one would do on track.
From the point of view of wearing out the clutch unduly? It matters the whole time.
MrKipling43 said:
they have slipper clutches that automatically slip the clutch plates to prevent engine braking.
Indeed. And very useful on a bike with a sequential, manual gearshift.
I'm not a biker. Do they throttle blip on the downshift? Or is this too hard given the throttle, front brake combination? And hence - the "slipper" clutch?
Don said:
MrKipling43 said:
they have slipper clutches that automatically slip the clutch plates to prevent engine braking.
Indeed. And very useful on a bike with a sequential, manual gearshift.
I'm not a biker. Do they throttle blip on the downshift? Or is this too hard given the throttle, front brake combination? And hence - the "slipper" clutch?
Bikers do blip on downshifts. With a bit of practice you can brake and operate the throttle at the same time.
At high revs, failure to match revs/road speed can easily lock up the rear wheel, even in the dry. The effect is much more pronounced than in a car. Big twins, like Ducatis, have lots of engine braking so slipper clutches were gradually introduced. They can now be found on some 600s like the new R6.
rsvmilly said:
Don said:
MrKipling43 said:
they have slipper clutches that automatically slip the clutch plates to prevent engine braking.
Indeed. And very useful on a bike with a sequential, manual gearshift.
I'm not a biker. Do they throttle blip on the downshift? Or is this too hard given the throttle, front brake combination? And hence - the "slipper" clutch?
Bikers do blip on downshifts. With a bit of practice you can brake and operate the throttle at the same time.
At high revs, failure to match revs/road speed can easily lock up the rear wheel, even in the dry. The effect is much more pronounced than in a car. Big twins, like Ducatis, have lots of engine braking so slipper clutches were gradually introduced. They can now be found on some 600s like the new R6.
Like Heel and Toe - just with the right hand! Thanks for that...an education...
Three comments about Don's long and good post:
1 Don talks about 'blipping the throttle'. This means briefly raising the revs above the level which will match the road speed, and hoping to catch the right level of revs as you let the clutch up. Another and maybe easier technique is to smoothly raise the revs just to the level required. Some people call this a 'sustained rev' or 'sustained throttle' technique. It goes well with a slow smooth gearchange.
2 Don implies that to use 'heel and toe' you always use your toe on the brakes and heel on the throttle. What part of your foot you use depends on the layout of the pedals, but generally it would be the ball of the foot on the brake and the right side or the heel on the throttle. The really important thing is to make sure you have firm and safe control of the brake pedal. If you get the throttle blip wrong it is much less serious than if your foot slips off the brake. While H & T is almost universal on the track, it is not mentioned in Roadcraft and you can drive quite swiftly as well as smoothly on the road without using it. There is an extra margin of safety if you avoid BGOL.
3. If you want to practise rev matching, I suggest that you include block changes such as 5th to 2nd, taking up the drive in 2nd say at 20 mph - with this sort of change it becomes more important to match the revs reasonably closely to road speed.
Keep it Safe, Smooth, Systematic and at a Sensible Speed.
1 Don talks about 'blipping the throttle'. This means briefly raising the revs above the level which will match the road speed, and hoping to catch the right level of revs as you let the clutch up. Another and maybe easier technique is to smoothly raise the revs just to the level required. Some people call this a 'sustained rev' or 'sustained throttle' technique. It goes well with a slow smooth gearchange.
2 Don implies that to use 'heel and toe' you always use your toe on the brakes and heel on the throttle. What part of your foot you use depends on the layout of the pedals, but generally it would be the ball of the foot on the brake and the right side or the heel on the throttle. The really important thing is to make sure you have firm and safe control of the brake pedal. If you get the throttle blip wrong it is much less serious than if your foot slips off the brake. While H & T is almost universal on the track, it is not mentioned in Roadcraft and you can drive quite swiftly as well as smoothly on the road without using it. There is an extra margin of safety if you avoid BGOL.
3. If you want to practise rev matching, I suggest that you include block changes such as 5th to 2nd, taking up the drive in 2nd say at 20 mph - with this sort of change it becomes more important to match the revs reasonably closely to road speed.
Keep it Safe, Smooth, Systematic and at a Sensible Speed.
waremark said:
3. If you want to practise rev matching, I suggest that you include block changes such as 5th to 2nd, taking up the drive in 2nd say at 20 mph - with this sort of change it becomes more important to match the revs reasonably closely to road speed.
Careful if doing this, mind. Lose all your speed on the brakes first then make the gearchange.
There's a corner at Bedford Autodrome where you are braking from 100mph or so down to 30(ish). The gearchange required is 4th to 2nd in my car. So I brake hard, Heel and Toe, but still block-change 4th directly to 2nd. The danger with this is that if you change too soon the revs in 2nd will be too high and you will bugger your engine (expensive) and that if you don't rev-match nicely the engine and clutch drag braking effect will be very powerful. At this point the rears will lock and its "Hedge. Here I come!"-time. Super nasty.
On road, of course, I change from fifth to second or first very often and with no danger as I don't do it whilst braking (I am an IAM Observer) and the revs are quite low anyway by the time I am taking up 1st or 2nd gear.
Waremark - thanks for your comments!
Hi Don.
At that corner at Bedford, I was changing down sequentially in order to use engine braking to assist the brakes - so 4th to 3rd at about 90, and 3rd to 2nd at about 50, using H & T to match revs to road speed.
Like you, I am an IAM Observer, and generally avoid BGOL on the road - but I do invariably try to match engine revs to road speed on every gear change.
Interesting how everyone thinks the IAM has a flat cap image, yet here we meet like-minded enthusiasts who admit to membership!
At that corner at Bedford, I was changing down sequentially in order to use engine braking to assist the brakes - so 4th to 3rd at about 90, and 3rd to 2nd at about 50, using H & T to match revs to road speed.
Like you, I am an IAM Observer, and generally avoid BGOL on the road - but I do invariably try to match engine revs to road speed on every gear change.
Interesting how everyone thinks the IAM has a flat cap image, yet here we meet like-minded enthusiasts who admit to membership!
i have aaother question to add onto this throttle blip thing
now i get the concept and everything...but can i press on the clutch, take the lever back, and THEN do the throttle blip, then let up on the clutch...or do i need to blip before i take the lever backforward, or does it matter at all?
now i get the concept and everything...but can i press on the clutch, take the lever back, and THEN do the throttle blip, then let up on the clutch...or do i need to blip before i take the lever backforward, or does it matter at all?
spidydude said:
i have aaother question to add onto this throttle blip thing
now i get the concept and everything...but can i press on the clutch, take the lever back, and THEN do the throttle blip, then let up on the clutch...or do i need to blip before i take the lever backforward, or does it matter at all?
now i get the concept and everything...but can i press on the clutch, take the lever back, and THEN do the throttle blip, then let up on the clutch...or do i need to blip before i take the lever backforward, or does it matter at all?
Clutch down, into neutral, rev, into gear, clutch up.
(DD clutch = clutch down, into neutral, clutch up, rev, clutch down, into gear, clutch up)
Make sure that it's enough revs that in the time it takes for you to get into gear & clutch up they haven't all dropped off, they should be falling to meet revs at current road speed in new gear, not falling to those revs before clutch is up.
Edited by vonhosen on Tuesday 21st November 22:29
Getting the revs right while playing footsie with the pedals while everything else is going on around you is not an easy skill to learn, and you have to be clear in your mind which mistakes you're going to make and what you're going to do if you mess up.
If you're trying to match revs on a downshift it's almost always safer to give it slightly too many revs (so the clutch pulls the revs down slightly when you engage it), rather than too few revs (so the clutch pulls the revs up when you engage it). Since you won't get the revs perfect every time, feed the clutch in smoothly and gradually to minimise the effect of any mismatch. If things go badly wrong, you may find you can't complete the gear change and control the braking accurately. The safe option is to abandon the gear change, ignore the throttle, keep the clutch down and stay on the brakes until you are at a comfortable speed for the corner. The feel of the pedals changes a lot depending how hard you are braking, and if you're driving hard enough to get any benefit from this technique then you will probably be braking relatively hard. That means you need to be braking hard while you practice it. Avoid putting yourself in situations where you *need* to brake hard during heal-and-toe, unless/until you can pull heel-and-toe gear changes perfectly without thinking about it time after time.
If you're trying to match revs on a downshift it's almost always safer to give it slightly too many revs (so the clutch pulls the revs down slightly when you engage it), rather than too few revs (so the clutch pulls the revs up when you engage it). Since you won't get the revs perfect every time, feed the clutch in smoothly and gradually to minimise the effect of any mismatch. If things go badly wrong, you may find you can't complete the gear change and control the braking accurately. The safe option is to abandon the gear change, ignore the throttle, keep the clutch down and stay on the brakes until you are at a comfortable speed for the corner. The feel of the pedals changes a lot depending how hard you are braking, and if you're driving hard enough to get any benefit from this technique then you will probably be braking relatively hard. That means you need to be braking hard while you practice it. Avoid putting yourself in situations where you *need* to brake hard during heal-and-toe, unless/until you can pull heel-and-toe gear changes perfectly without thinking about it time after time.
if you are heel n toeing, then the characteristics of the brakes and the physical layout of the pedals make a huge difference to how easy it is.
My Tiv has the perfect setup for it...the throttle pedal is organ-pedal-stylee which I find easiest, the brake pedal doesnt have too much travel and it is not over-braked so you can use the brake pedal as a firm platform.
My (er) Galaxy has the worst setup for it...there's a big gap from brake to throttle, the brake pedal has quite a lot of travel and it is ridiculously over-braked so you end up with a massive spike in braking as you try and blip and hold the brake pedal with a consistent amount of braking.
Graham
My Tiv has the perfect setup for it...the throttle pedal is organ-pedal-stylee which I find easiest, the brake pedal doesnt have too much travel and it is not over-braked so you can use the brake pedal as a firm platform.
My (er) Galaxy has the worst setup for it...there's a big gap from brake to throttle, the brake pedal has quite a lot of travel and it is ridiculously over-braked so you end up with a massive spike in braking as you try and blip and hold the brake pedal with a consistent amount of braking.
Graham
vonhosen said:
Clutch down, into neutral, rev, into gear, clutch up.
(DD clutch = clutch down, into neutral, clutch up, rev, clutch down, into gear, clutch up)
Make sure that it's enough revs that in the time it takes for you to get into gear & clutch up they haven't all dropped off, they should be falling to meet revs at current road speed in new gear, not falling to those revs before clutch is up.
One learning technique I have tried out on people learning to blip is to mentally think of timing the blip as they push the gearlever through the gate for the lower gear. Otherwise it tends to be discrete actions and the blip ends up being too early and bigger than it needs to be as the clutch is catching the tail end of the blip IYSWIM!
Graham
MrKipling43 said:
One thing I've found is that in order to get a heel-toe downshift smooth, you have to be quite aggresive with the clutch - if you're too slow the revs drop too far and it messes the whole thing up. It's quite an odd technique in that respect.
do you mean that you run out of time to get the clutch up before the revs drop so you have to bring it up super quick? If so then you can delay the blip to compensate (as I described above) rather than being super quick on the clutch. This is where the whole H&T thing is good for the track to get very quick changes.
This might be or (depending on your pov) is where the technique for Advanced Driving for the road differs from the track. If you are seperating braking and gear changing then you can raise the revs in a different and more accurate way. If you have finished braking, you have the whole of the "concentration" of your right foot available to gently raise the revs as you gently bring the clutch up. You do not need a blip per se. You also have more time as the whole thing should be more leasurely on the road.
Using H&T on track you are using most of the "concentration" of your right foot to brake to maximum without locking up and only have a little to spare to bang in a blip. Which is fine as a rough blip does the trick. Inaccuracy of timing is not a problem as you are doing the whole change very quickly.
Hope my "concentration" concept encapsulates a sensible meaning!
Double hope I am not appearing to be a H&T geek! I'm the life and soul of parties when I get going!!
Graham
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