ru'

I'm very suprised at that (not doubting you, just suprised).

DocJock

I'm sorry, but how the **** can you double-declutch with a failed clutch cable ? That is patently impossible.

Are you confusing your DDC with heel and toeing ?

BTW it is physically impossible for DDC to be as fast as a properly executed H&T downshift due to the required pedal action whilst in neutral.

JTaylor

It's not physically impossible of course but I know of nobody who DDCs in a modern car to aid performance. H&T all the way for me. If somebody demonstrates a technique to brake and match revs simultaneously that is more effective, then I will happily adopt it.

Suprised about the anti-trail braking comments aswell. Not always appropriate but can be effective in unsettling the car when this is desired i.e. quick direction changes when you want to be shifting the weight forward to get the back swinging round.

prana

I DDC using HT into first gear, only way for me to get my shifter into first at 5000revs a minit. 2nd gear on cold early mornings also. All other gears and situations are pointless, just HT, no point in DDC.

John 37

Some interesting points.

Obviously you can't DDC without a clutch cable but the fact that I am used to matching the gear speeds to the engine means I can change gear without the clutch. (Starting off from rest is another matter but is best talked about elswhere). As a result, when my cable fails, I can still change gear.

I'm not confusing DDC with H&T. H&T is simply DDC while using the brakes.

If you change down without DDC or blipping the throttle, you have to let the clutch engage slowly or accept a jerk to the car which can de-stabilise it in a bend. This is particularly noticable if you are downchanging at high revs as the increase in engine speed is greater. If you blip the throttle, That takes time and my left foot operates the clutch in that time. Where DDC wins is that I can let the clutch up quickly without having to wait for the engine speed to match the road speed. I also find the gears select slightly quicker as their speed is matched. That isn't the case when you just blip the throttle. This is most noticable when changing into 1st on the move. H&T'ing into first before a tight handbrake junction keeps the turbo spinning and gets me into the right gear quickly and smoothly.

I will admit that there are many occasions in modern cars where the use of DDC and H&T is debatable but since I've been doing it for so long, I will continue to do so. I certainly can't see any down side (except perhaps a little more wear on the clutch cable) and there are many advantages. I still believe that matching gear speeds by DDC/H&T rather than relying on synchromesh saves wear in the gearbox.

As the OP specifically asked about track days, perhaps some of my comments are irrelevant. On a track, the brakes are being used to slow the car at the limit of adhesion. Adding additional load due to a rough gearchange can alter an already critical situation. That's why I want my down changes to be as smooth as possible under braking. The speed of the change is rarely an issue unless the braking distance is very short. The matching of engine speed is very important which is why modern race cars link throttle control to the gearchange.

prana

??

Steve Whitehorn

iTrader: (13)

I drive alot at the moment in snow and ice sometimes coupled with strong wind. ( Just got out the car, as I right this, after a 3 hour drive accross Barvaria - conditions roads snow being blown on to them and then turning to ice.) Obviously smoothness and gentle steering and throttle inputs when things are sliding a little. My point is - is that I find DDC totaly invaluable when matching engine speed to road speed in these conditions. It´s not something I do in every day driving but really helps keep the car´s weight in a static state.

Steve

P.S. whats the weather like in the UK at the mo as im back for a few days v soon.

JTaylor

http://video.google.com/videoplay?do...91&q=M3+nissan

Some good footwell footage here.

Fuzz

John37,
Heel and toeing isn't about just blipping the throttle as you down change it's more to do with getting the revs to the same speed as the gearbox, it's nothing like double declutching.
Sounds like you need a lighter flywheel or a heavier stamp on the throttle if the revs dont rise quick enough to catch the next downchange speed difference.

Andy

rmtypeR

I don't agree with John that "DDC is just H&T whilst braking".

Heel & toe in my book is (whilst braking) clutch in, select gear and then blip the throttle to raise the revs so that when you lift the clutch the revs are already at the point where they match the particular gear/speed you're travelling at.

As mentioned by Stainy earlier....

If you were to go through the full double de-clutch whilst braking on a track , you'd probably come to a complete halt before you got it over with!

ru'

<monday morning rant>

Am I the only one who finds this confusion between DDC and H&T somewhat bizzare?

Why would you call blipping the throttle with your toe whilst braking with your heel (or vice versa) 'double de-clutching'??? Surely this is obviously 'Heel and Toe-ing'?

And why would you call the process of changing gear which involves two separate clutch operations (yet doesn't involve your heel and toe doing different things) anything other than 'double declutching'?

Sorry for the blunt post, but come on, think about it ffs!

It's even been described earlier in this post, yet there still seems to be some confusion...

</monday morning rant>

ps simplification of both processes for clarity here, before someone launches into me for my descriptions...

pps "but is it understeer"?

JTaylor

No.

You can of course heel and toe whilst DDCing (and perhaps this is what John's trying to illustrate) but it's not common (at all) for modern drivers in modern cars driving at near the limits to DDC. My late Dad used to in his classic cars to affect smooth gear changes:

Clutch In > Neutral > Clutch out > Blip/revmatch > Clutch In > new gear > clutch out.

Sounds protracted but it all happaned very quickly. Other then for reasons (arguably) of mechanical sympathy, I cannot see how this would present a performance/dynamic advantage over heel and toe. John clearly has a fair bit of experience and perhaps some of us are just missing the point.

J

prana

ru - on tight roundabouts, dropping to 1st gear then out.

Brake, clutch in, shift to second, blip, brake some more, clutch in, neutral, clutch out, blip, clutch in, shift to 1st, clutch out at 5000 revs in 1st gear. It happens...

No way I can shift into 1st without ddc at 5000 revs

edit - I am wrong, the only way I can shift to 1st without ddc is to lose traction altogether, Dont ask me why but its easy to shift to 1st when you're powersliding ... some else can explain the mechanics behind it.

JTaylor

Agreed. Even then, particularly given all the other stuff going on approaching a hairpin, it's easy to get it wrong. Out of mechnical sympathy I've never used 1st like this in the Scoob - although if/when I start hill climbing I'll probably have to to avoid lag. It's in situations like that that I miss a car were you can break traction comparativley easily.

John 37

Hi guys,
As you may have guessed, Ive been off this forum for a while. Glad to see that the thread is going well.
Now I think everyone agrees that, as Stainy put it, H&T is: clutch in, select neutral, clutch out, rev, clutch in, select gear, clutch out.
The modern equivalent simply involves a normal gearchange with a blip of the throttle: clutch in, select gear and rev, clutch out.
The vehicle dynamics are much the same, the engine speed is matched to the road speed before the clutch is engaged. It's the gearbox that sees the difference. With most modern gearboxes, the synchromesh will match the gear speeds quite quickly. There are a number of reasons that they are quicker than older boxes. The gears are smaller as materials have improved so their inertia is less. Modern oils are thinner so give less drag. Gear ratios are closer as there are more gears so the speed difference between adjacent gears is smaller. I drive a number of cars with only 3 gears. Try driving a modern car but not using 2nd and 4th and you will see what I mean.
Again, most folks seem to agree that there is a need to match the engine and road speeds before engaging the clutch to avoid upseting the balance of the car. A light flywheel helps here in two ways. It allows the engine to blip up the revs quicker and, if the revs are not quite right, it gives less of a jerk when the cluch is engaged due to it's lower inertia.
Now H&T was originally DDC while braking. That was in the days when all downchanges needed DDC as synchromesh was either non existant or very weak. Again, the modern equivalent substitutes a blip of the throttle for the intermediate pummeling of the clutch.
It's easy to see where the confusion comes from as both systems require the use of all three pedals so could be called H&T. The question is, which one is best? Personally, I use the older method. This is for a number of reasons. The first is simply that I can, I've been doing it for years, it's a habit now and it helps when I drive old cars or my clutch fails. All of those reasons are very personal. There are others though. As everyone agrees, speed matching is good when down changing. The opposite must apply, that badly managed down changes can upset the balance of the car. I find that there are occasions when I change down more than one gear at a time. A long straight into a sharp bend will typically need 4th to 2nd. Going via 3rd is pointless and introduces an extra gearchange with the attendant risk of upsetting the balance. This is especially so as that change is in the middle of the braking area and at speed. However, downchanging two gears without DDC gives the gearbox more work to do and makes the change slower or less accurate. Certainly the change into 1st is very difficult without DDC. JTaylor will find this when he goes hillclimbing. The second hairpin at Prescott NEEDS 1st, especially in an imprezza where you need to keep the turbo spinning and can use the power in the lower gear. If you look at the ratio's, 2nd to 1st is a big gap. This means that the gears have to speed up more and, as 1st is a low ratio, the gear is one of the biggest in the box. Hence the problem.
Back to the question, is it necessary? If you watch the video that JTaylor posted, the downchanges are quite slow compared to the upchanges. Is that a problem? If a car is lowing from 100mph to 30mph, it all takes some time on the brakes so there's no rush. That's when you need to take things easy and get the change smooth. 2nd to 1st is another matter. It's a difficult change and the braking time is short. That's when a smooth fast change is needed. I maintain that I can achieve this better by H&T&DDC (I tried not to use that term, honest, but you know what I mean).
The bottom line is to use what suits the track, the driver and the car. Just because this dinosaur can and does do it doesn't make it right for everyone.

Mongo

Heel and toe really Is best uesd with a pedal box or non servo *** brake set up. TBH with modern gearboxes you probably dont need to but it does sound cool.

John 37

Interesting comment about pedal boxes. Why?
I would agrre though as pedal boxes allow the F/R brake balance to be optimised. This means that the car is much more sensitive to unbalancing inputs than a normal prod car. The Impreza has a lot of front brake bias as standard so the rear is unlikely to step out compared with a more critically set system.
If you want to see this in action, ask a motorcyclist. Bikes have seperate F&R brakes so the rider can vary the balance continuously. Even though the flywheels and engines are light, a braking downchange at 10,000rpm without a throttle blip makes life very interesting.

Mongo

Thats one of the reasons. Also pedal boxes dont have servos, so brake travel is firm but travel is minimal... Last thing you want to do is go for the accelerator with the heel and over brake trying to get your heel accross and theres also the hight difference in the pedals. Much easier when they're both at the same hight..

Make sence, good comment about the balance bar. Might have a look at some M/C master cylinders/balance assemblys for the rall car.. Or at least the design

JTaylor

Interesting post John. Still not entirely convinced by this though:

Perhaps I'm misguided, but I always thought the gear change part of heal and toe was clutch in, change down, clutch out - why the superfluos clutch in and out business?

John 37

DDC is Clutch down, engage neutral, clutch up, blip, clutch down, engage lower gear, clutch up.
The purpose is to use the engine to speed up the gears so that they engage easily.
Traditional H&T does the same while using the brakes.
Blipping the throttle without lifting the clutch only speeds up the engine. Better than nothing and possibly quicker but the lower gear cannot be engaged as quickly or smoothly.
If you get the speeds matched perfectly, you can manage clutchless changes. This allows left foot braking easily. I've seen film of this but never found the need personally. I also suspect that the driver was in a pure comp car using a very different type of gearbox to ours. Certainly, motorcycle gearboxes respond well to clutchless changes. My Honda is a good example of that. I've seen bikes that have automated gear change where a pneumatic ram moves the change pedal at the same time as the electronics cut the engine for a split second on the up change. I do mean split second. Gearchanges faster than you can see without closing the throttle. Just press a button and you're in the next gear.

Mongo

I can do this but on the road it really is quite pointless. Unless your running out of braking room and/or need to left foot brake for cornering stability.. It's really fiddly to do and requires a fair bit of practice and knowledge of your car, engine and gearbox. But satisfying if you dont bugger it up!

Another on to try is left foot braking and swapping braking feet over and heel and toeing down the gears.. Still a bit pointless but good if you get bored easily like me

Brit_in_Japan

Nice little vid from Tsukuba circuit. Interesting bonus footage at the end, I think it's from the Gunma cycle course, they sometimes use it for sprints. Just been there the once, had a blast

pic

theicewall

You dont have to rotate your heel over, the technique is kind of a misnomer because you are really just rocking your foot.

Stand up and look at your computer screen...

Now, while balancing your weight on your left foot I want you to stand on the outside (lateral 5th metatarsal) of your right foot as if you were twisting your foot in a game of basketball.

Sit back down now...

When you are on the brakes in your car, make sure that you place the fat pad at the ball of your big toe just to the right of the midline of the brake pedal with your heel ever so slightly angled but not really. Now with the car in neutral and your left foot on the dead pedal to prevent any gearbox grinding mishaps rock the outside of the right foot over just like that basketball injury ankle twist. Next thing to do is aim for an rpm, like 2k sounds good from idle because for normal driving you will only need to shoot up 2k rpms to hit the next gear in a downshift and once you get that go for the big vigorous rock up to 3k for your more heavy braking applications. You will use this one when you are in 3rd and you have the wheels just about on the verge of lockup because even though the gear gap is usually around 2k rpm while you are moving through neutral you have just decelerated another 5-8mph or so.

Hope this helped someone.

willy

My experiences with heel and toeing have been on track(Elvington).
I was lapping pretty well on my own, and after lunch, had an instructor sit in with me for 5 laps or so.
His advice was to heel and toe as I approached a hairpin, coming down to first gear.
Ie matching engine speed just before the clutch was let out on 1st gear.
He said it would help smooth things out and make the car more stable etc.
Well I got the hang of it and it seemed much better, less stress on the car too.
Hope this helps?

*****

ZEN Performance

Double declutching isn't the same as heeling and toeing. You can heel and toe without double declutching and vice versa.

With a dog box it is beneficial to double declutch on up shifts if you are not trying to change as fast as possible, you don't blip the throttle though.

On track I find heeling and toeing can help on certain bends if you get it right, even with a synchro box as it helps to prevent unsettling the car as you reengage the clutch. However, Mr Prost famously wrote in his book about advanced drving techniques, that many times he didn't even change down the box while braking, and just block changed near the end of the braking zone.

theicewall

"if you heel and toe properly you also are double clutching", gary sheehan

order -> clutch, shift to neutral, heel-toe rev match, clutch, select gear, trail brake, full throttle --> celebrate!

rmtypeR

"I refer the right honourable member to the answer I gave some moments ago...."

I agree with Zen Performance

GarySheehan

I don't recall ever saying that. I double clutch on my downshifts, but it's not necessary for heel-toe. I do it because it's easier on the equipment and there is plenty of time to get it done in the braking zones in big heavy sedans.

Gary
Sheehan Motor Racing
www.teamSMR.com

GarySheehan

That's not true. There is PLENTY of time to double-clutch down through the gears on a track.

Here is an example from my 2002 USTCC WRX racecar...

http://www.teamsmr.com/movies/Footbox%20Small.wmv

Gary
Sheehan Motor Racing
www.teamSMR.com

rmtypeR

Now that's fast! I had to play it is slow motion to check that you were actually doing it right!

Maybe I should re-phrase my previous comments... if I were to do that on track I'd come to a complete halt.... etc