Ok, ive been thinking about double clutching for a minute and ive realized that its not as time saving or efficiant as it could be. Heres my thougths.

You can save the time needed to for the first clutch in. If you notice when the clutch is engaged and the car is under acceleration you can pull on the gear selecter lightly yet with possitive preasure and as soon as you come off of the accelerator the gear selector will instantly slide into neutral.

Tap the accelerator to get the trani up to speed and clutch in and select the chosen gear. This is a great thing to do when your cruising ni 5th and want to get moving quickly.

It can also work approaching a corner under breaking, the gear selector would have to be pulled clean of the gear in teh time it takes you to transition your foot from accelrator to brake and throw your heal down on the accelerator.

I had gotten pretty proficiant at regular heal toeing for downshifts into corners and it took some getting used to this way. However it now comes very natural and its not hard, but too mutch trouble for my lazy sack of bones to bother putting my foot on teh clutch first, waiting for myself to take my foot off it so I can hit the gass to speed up the trani.

So what do you all think?

 

i bet the time saved is so negligible that it wouldnt matter

 

I think I am totally confused. Sorry. I had a '71 Beetle with a crapped out 3rd gear synchro that needed to be double-clutched on downshifts, so I learned it without thinking much about it. I could muster it if I needed to but in a modern car in good health...? I have also heard people talking about double-clutched upshifts which is, uh, odd. Maybe I am just a dork.

K

 

I thought a well-executed heel-toe downshift elimited the need to double-clutch a modern synchromesh gearbox.
-Adam

 

I think I'm tending to agree on the "why bother with a decent tranny?" point. I blip the throttle to match revs on downshifts on the street and track for many years out of habit and because I like it but I don't see why create that much additional work double clutching if your clutch and synchros are in good shape.

I tend to think your method might save a fraction over a double clutch but even that isn't needed if the tranny is in about any working condition. Our cars don't tend to be tranny eaters if you drive with much smoothness so rarely does one have weakness issues. Adding the extra motions I would think is just adding to some mechanical motions and opportunty to get out of sync and screw up.

Since I added a quicker shifter about a year ago, I found the that trying to move the shifter too quickly in hard acceleration (expecially the 1-2 shift at high rev) can cause missed shifts because the linkage is moving faster than the tranny wants to go so you tend to need to sometimes be a little slower with the shifter. In this case, it seems to me that the linkage may be the slow down part of the shift so really speeding up your foot and clutch work might not really be that much of a time savings in the grand scheme. So as long as you are not hurting or overtaxing then to me the simplest, consistant route would be best.

 

What time saved?? Down-shifting and braking are done at the same time.

 

no clutch in on the shift into neutral works fine under slower shifts but when you need to do in under hard braking and downshift it is far easier to do the full motions (after it is already 2nd nature and done with flawless motion)...

most ppl feel with modern synchros there's no need for double clutch. i'm one of the VERY few that advocates and practice DC on down and up shifts except in the heat of battle.

 

if I understand what your saying you are telling me that you can push your clutch in, hold it there, take your gear selecter from whatever gear its in and immediatly put it into the lower gear? I dont know what kind of manufactuer your driving or what trani it has but that sounds very unusual. Most syncromeshed transmition of this day would not alow that. Not to mention if you need to go from 5th to 3rd.

Maybe its just me. Ive had people who race regularly (autoX, HPDE and recreationaly) who say im realy good at rev matching. I guess its through doing that all the time that im just used to DCing all the time...at every stop, every corner or every joe that pulls up next to me and revs (ok I dont race those people anymore...I did though religiously). Maybe that makes my idea of DCing seem alot quicker than your trying to explain to me.

This is also not just for hondas, this applies to my 86 Corolla, as well as a 99 Z06 that had an automatic trani replaced with factory 6 speed. And that sucker was fresh, nice and crisp. Also had this annoying 1st to 4th shift that was supposed to save fuel. It was pushing 505 to the wheels and trust me, 4rth gear at even 15 mph had enough power to move that car forward with a decent pull. Anyway....even with that transmition I could not go from a higher gear into another one simply by flat shifting. I had to DC.

 

I can go from 5th to 2nd no problem with just a simple throttle blip. I've never double clutched in my life.

 

This is easily done in my 97 prelude...however, revmatching is neccessary..

I raced from a roll @50...Took my car from 4th-2nd.

Here is what was done, because im a bit foggy on what is being said.

1.push clutch in
2.remvoe shifter from 4th to neutral.
3.rev to about 6k (w/clutch still in. this is the rpm, im assuming my motor is @50mph in 2nd gear.)
4.shift to 2nd (w/clutch still in.)
5.release clutch.
6.gas it!

The end result is a smooth transition, from very little power to right into vtec. The idea behind this is to save your synchros, they are not bullet proof.

While this isn't really neccessary during drag racing..during road race/auto x "Double Clutching" is a huge advantage because it is more time spent on the brakes...

You could think of it as multitasking...ie, you are braking and shifting all at once..

Hope that made sense to someone..

*EDIT*
just read what I quoted in DETAIL here is what I got out of it.

you are saying this??

when you Down shift...you have to
1.clutch in (we will use 4th gear as an example)
2.remove gear to neutral
3.clutch out...
4.clutch in (i assume some kind of revmatching was done between steps 3 and 4.)
5.move gear selector to 3rd..
6.clutch out..

if this is the case...which I highly doubt. you must be driving a Model T.

On the other hand maybe I am just not understanding...Maybe double clutching needs to be explained to me in detail.


[Modified by dsludefosho, 11:19 PM 2/24/2003]


[Modified by dsludefosho, 11:21 PM 2/24/2003]

 

What you just described is not double-clutching. It's simple rev-matching. DCing goes like this:

1. Clutch in, shifter to neutral
2. Clutch out, RPMs falling
3. Match revs for new gear
4. Clutch in, shifter to new gear at new RPM
5. Clutch out

Again, with a good gearbox and good synchros I don't know why this is necessary today.

-Adam

 

*ignore this, see lower post, dunno what happened.*


[Modified by dsludefosho, 1:17 AM 2/25/2003]


[Modified by dsludefosho, 1:20 AM 2/25/2003]

 

1. Clutch in, shifter to neutral
2. Clutch out, RPMs falling
3. Match revs for new gear
4. Clutch in, shifter to new gear at new RPM
5. Clutch out

Isn't that what I described @ the bottom of my post??

anywho I was always a lil foggy on the subject, thanx for clearing that up.

It still doesn't make sense why this is being done in a Z06?? I have driven a 95 vette numerous times, and dcing was not necessary at all..even in a skip shift. (ie 4-2.)

I think everything we have been describing is either rev matching, or heel toe shifting..


[Modified by dsludefosho, 1:23 AM 2/25/2003]

 

Yes, you're right, the lower half of your last post was correct. It all starts to blur after ten posts of the same thing.
-Adam

 

at no point wether HPDE or Wheel to Wheel do I want my car in neutral

too much can go wrong with this system, like to know the car is in gear at all times so if **** happens I can get on the throttle and make a desicion

 

1. Clutch in, shifter to neutral
2. Clutch out, RPMs falling
3. Match revs for new gear
4. Clutch in, shifter to new gear at new RPM
5. Clutch out

This is what I do all the time, street, HPDE, road race, whatever. If this is what you taught yourself, this will be what works. It sounds long, but it's not when it's what you've grown used to.

 

IBTL?

 

Why bother? Last I checked, none of us were racing vintage cars or driving heavy trucks. Heel-toe properly and be done with it. And why would a DC ever be needed on an upshift? You barely need a clutch at all for upshifts.

 

just because the H-T sheep all agree doesnt make it correct.
I am with GR, Civic44 and the other DCers, oh and Skip Barber too. While DC is not always necessary to rev-match, it is easier on the transmission, and can be advantageous or necessary in many situations. Example: My car will only go into first while moving with a DC. It definately doesnt have any drawbacks, so why wouldnt you want to have it available in your toolset? Even if you dont currently use it?
It sure would suck if you had the opportunity to drive a high horsepower dogbox car but couldnt drive it since you cant double clutch.

 

Eh? It's not supposed to be time saving or efficient. It's the OPPOSITE. All double clutching does is make it easier to slide the selector into a lower gear. In a car without syncros it makes it possible to select gears.

Okay...there are three shifting techniques, and everyone always seems to mix up what they each are for:
1. Rev matching
2. Heel Toe
3. Double clutching

Rev matching just matches engine speed to wheel speed so that when you let the clutch out you don't get that lurch or lag as the engine has to rev up or down under pressure from the wheels through the tranny and clutch.

Heel toe is just rev matching while braking so that you can brake as late as possible and still have time to shift so that you can power out of the turn. It also prevents the lurch or lag while turning and unbalance the car.

Double clutching gets all the gears inside the tranny spinning the right speed so they can be selected. It's an old technique from when cars didn't have synros. This is a relatively uninportant technique to learn now as syncros are supposed to get the gear you're trying to select to move at the right speed so that the teeth on the selector will match up. If you want to do it now you can, whether to save wear on your syncros during downshifts, or because your second gear syncro is going out (like mine) and it's just a bitch to push the selector into gear.

Well, yes, you can just pop your car out of gear at any time, but it will wear pretty heavily on the throwout bearing.

Your little timesaving idea will damage your transmission. There is no clutchless gear selection that will not wear on the transmission somehow.

Yes, there are some people that learn their engines and gearing really well and shift without releasing the clutch at all, and if you're really good you can minimize the extra wear, but it will wear faster than proper use of the clutch.

 

urbanlegend21

At some point during a gear change your going to be in neutral. No one in a race environment wants to leave there selector in neutral. Thats not what were talkin abot here. Also if you have your timming down you can brake into a corner heal toe and DC into lower gears, (if you like to DC in high gears and hold lower RPM while breaking down speed...) you can be in mid corner and be able to DC into an evenlower gear if youve managed to make the mistake of selecting the wrong one initially and still be on the ball with acceleration thats more than satisfactory.

Civic44 thanks for the nod...theres no way I would have been able to have the fun with that Z06 that I did if I didnt have some skills. It would have been flat shift on every gear and slowing with only brakes.

MoJo...help me understand

While yes DCing was born from crappier gear boxes you have to admit that modern syncros arent up to the challange that most of us can give to a gear box. I keep my skills pretty fresh by testing myself almost daily. I make sure I can do certain things...I have a 3rd to 4th upshift that you cant even hear a transition on. ALl you hear is the motor switches revs. I love that sound. But even upshifts as quick as I try and make them is more abuse than my syncros could take and they started wearing. I would have my Down shifting take place just as quick if I could. So my hand moves pretty quick. I dont even bother to move my arm. I just throw the selector around by moving my wrist.

Sorry, got off on a tangent there. Thanks cause you were the only one to give feedback that actually had to do with my origional post and you answered my question. Another question is moder or even new gearboxes being built as they are you think they can handle quick shifts with the stock syncros as they are? I had a chance to drive a brand new MR2 (worked at a dealer, thing had 3.2 miles on it before me and a demo Camry SE. The MR2 I didnt have the heart to take past a certain RPM cause it wasnt broken in, the Camry though I ran hard. Neither of the tranis though could take the speed at which I wanted to down shift at. Or upshift either...that 3rd to 4th shift of mine needs a somewhat worn syncro.

 

Am I the only one that shifts into a lower gear BEFORE blipping the throttle? I always did it like that, normal street driving or racing...

1. Clutch in
2. Downshift
3. Blip throttle
4. Clutch out

I find this more accurate and quick with less chance of screw-up. Since the end result is the same, ie: a smooth downshift under threshold braking i guess it doesnt matter what the sequence is. I mastered the technique quite well and have been complimented on more than one occasion by instructors...

Also, I find it easier (and more fun ) not to skip gears on downshifts. So that when approaching a 2nd gear corner in 4th, i'll pull off two quick heel-and-toe downshifts... Brake...4th-3rd-blip...3rd-2nd-blip...EndBrake...

 

Well, when new they should be. When worn, like mine, it's faster to double clutch into second than it is to wait for the syncro to get the speeds matched.

I never DC on upshifts. Upshifts are easy.

Hmmm...that could be bad. Are you forcing the selector for speed? If so, that's what would be damaging. It's more important to be smooth than it is to hurry and be jerky. What you should do is put the right up to the gear, and give it a little pressure, and let it just slide in on it's own. I've actually found this to be faster than when I try to slam it around.

Quick shifts? Yes. Hard slammed shoved shifts? No. And there isn't a speed advantage for hard shifting. You can move your hand fast, just don't use a lot of force.

Meh? Mastered the technique? Dude, you're talking about plain old vanilla rev matching.

You lose time though.

 

I wasnt implying that I invented the technique or anything. I just noticed all the people posting that they blip before downshifting. I blip after downshifting, well it happens so fast, that i would say it's almost simultaneous with the lever going into lower gear, but definetely past neutral...Small detail...

 

Thing is, I think they're talking about double clutching, not just rev matching.

But, that's how I do it too. I think it'd be wierd to do it without the next gear engaged. I wouldn't want anything between revving and letting the clutch out, because if getting the shifter in takes a little longer than usual, your revs aren't going to be matched properly. Get everything you need to done, and then rev and clutch.