Double Clutch Shifting [Merged 11-8] clutching synchronizing

[Jello_Rolls]

First of all, i have to say, DSM are the best. Ok enough kissing of ass, now to the real question. What is double clutching, and how would u go about doing this? I hear that it helps the cars go faster, and i dont know anything about it. I looked and looked, and search this topic, and have came upo with nothing, so i reach out for help.

 

[PHAST]

first off, hi, welcome, all that stuff.
okay, according to most ricers, its pushing in the clutch in the middle of a gear, shoving the pedal to the floor, and dumping the clutch. This will give you a little jump, it usually wont make up the speed lost by pushing in the clutch, and it'll also reduce the life of your clutch.
Real double clutching dates back to the day, before synchronized transmissions. You shift as you normally would, when its into the gear with the clutch out, push the clutch in again, this way you would get a couple little grinding noises instead of one really bad one.
Double clutching was also used in racing such as LeMans in the late-60's. Watch the movie 'BULLITT.' There are rumors that some of the vehicle sounds for the Mustang were recorded from a race version Ford GT40. When you hear it shift, it sounds like he's revving in between gears, this is the aforementioned double clutching from the early days on non-synchro trannys, along with rev matching (matching engine RPM in neutral to RPM engine will be at when you enter the next gear at your current speed).
That's pretty much it.

 

[RedTurboEclipse]

i never double clutch on an upshift, its pointless, but i rev match when downshifting.

 

[Tallen]

umm...why in gods name would you double clutch a car with a synchro'd tranny? all you are doing is loosing the speed of your shifts, and putting excess wear on the pressure plate. dont the terms from the fast and the furious make you think this is a smart thing to do. because it is not.

 

[MattR]

Ok, suppose youre doing 40 mph in 2nd gear at 4000 rpm. When you upshift to 3rd, say the rpm's drop to 2000. Ok so now you're cruising in 3rd at 2000 rpm at 40 mph and you want to downshift back into 2nd. You'd clutch in, neutral, clutch out, rev the engine up to 4000 rpm, cluch in, 2nd gear, clutch out. This is "double-clutching", you "pre-rev" the engine to the correct rpm's for the next gear while downshifting. This saves wear and tear on the tranny and engine, rather than making the engine jump back up to 4K by the tranny already moving at that speed.

As for "granny-shifting, not double-clutching like you should...", you wouldnt double-clutch in the 1320 because you never downshift. Double-clutching while upshifting will only make you slow down.

Hope this helps clear things up. Later

 

[rubbersidedown]

i dunno. i just don't see the point in double clutching w/ the cars we have now. If you are gonna down shift and you wanna match revs then just push the clutch and tap the gas and then shift down. it doesn't take all that much practice to get it right. and then when you're braking and going into a a turn you can just heal-toe and all that happy crap. i don't believe double clutching has any place in our current time. i know i didn't explain what double clutching is but i guess i just wanted to add my 2 cents on the whole subject. so yeah

 

[RedTurboEclipse]

yea you dont need to double clutch to rev match.. that would take forever, you just gotta have a good feel of it and it becomes instantaneous. that time when im downshifting to the lower gear, im already matching the revs with the clutch down so by the time i get it in the lower gear the revs are already matched for a smooth transition with no jerk.

 

[Turbocyde]

Originally posted by rubbersidedown
and then when you're braking and going into a a turn you can just heal-toe and all that happy crap.

Well now that sounds easy. Can you explain this happy crap to me. I have only seen it on initial D. :xnuts: this is not dirrected to you, I just saw it for the first time.... maybe I'm blind....But it's gawd dam funny and i have to use it now that i saw it

 

[abstraction]

heal-toe.... just a way to avoid losing revs/speed through turns. break with your toe, acceerate with your heel of your right foot... use the clutch with your left foot as usual. it helps you rev-match for turns that you have to downshift in.

 

[eclipseturbo7]

Ok.. Ive heard like 10 different ways of doing this from alot of people.. What is the correct way of double clutching? What is it that you exactly need to do.. Let me know please.. Thx

 

[thumper]

i believe it's a waste of time. all you do is press the clutch when you shift out, release, press the clutch in again when you shift into the gear. so you depress the clutch double for every shift. A lot of work and from what i've experienced and heard it doesn't save or help anything.

 

[cait sith]

^^ Above is wrong.

Basically it's rev matching but while in neutral to save your synchro wear (although this is debatable with tranny's made within the last 20 years...).

Double clutching Technique:

1) Remove car from gear that you are currently travelling via clutch, going into neutral.

2) Next, the goal is to match the RPM with the throttle to what your new gear will be at your current rate of speed.

Notes on this which screws everyone up:

Basically if your car does something like 3500 RPM in second, at 35 miles per hour, and you're downshifting to second, and are going 30 MPH, you'd rev the engine to 3500 RPM.

3) Engage clutch and put into desired gear. Release clutch and continue driving.

---

Advantages: There is absolutely no advantage of this for Drag racing. Leave your fast and furious quotes out of it.

Where it DOES come into play is road racing, to keep the car from becoming squirly, or to keep the transition smooth than a sharp jump in RPMs, but you can do it while just holding the clutch in via Rev matching as noted above, although it's difficult to brake at the same time...

 

[steve]

Originally posted by cait sith
you can do it while just holding the clutch in via Rev matching as noted above, although it's difficult to brake at the same time...

The technique for that is called heel and toe.

Steve

 

[eclipseturbo7]

Ok i get that, but where does the "double clutching" come in? i understand the rev matching..

 

[steve]

Rev Matching is step 2 in cait sith description.
Double Clutching is steps 1 and 3.

Steve

 

[eyebrowski]

there is A LOT of mis information in this thread

double clutch- using the clutch while rev matching to desired gear you are downshifting into
heel toe- double clutching while using the brake (cornering)
speed shift- 100% throttle during a shift using the clutch
powershift- no clutch, rev matching to shift gears.

double clutching serves two purposes:
1) makes for a smoother ride
2) keeps all rotating mass spinning, this will free up more horsepower which would be needed to get stuff rotating again

speed shifting will burn your clutch up fast but you can cut some time off your ETs (i've heard in the .1 range)

powershifting takes a lot of practice to do fast and is devastating to your tranny. but if you are strictly a drag racer your going to be swapping trannies a lot anyway...i do it all the time in the old VW for the hell of it.


if anyone would like detailed explanation on how to perform any of these shifts let me know.

 

[mdre21]

double clutching can be used on upshifts as well. It however is not necessary with trannys that have syncros. Older truckers used to use double clutching a lot, it can really help you get into gear, especially without syncros. Rev matching is very relevant when down shifting, even with trannys with syncros, it will save your tranny's life, your brake's life, and make downshifts much smoother.

 

[eyebrowski]

yes you can double clutch to upshift. but talking in a performance oriented way there is no point to double clutch on an upshift, it will take much longer than a tradtitonal 'granny shift' *cough*

 

[Kicka$$93laser]

All Right guys, I really didnt know where exactly to post this question at, so i figured here would be fine.
I have a little bit of an idea on what 'Double Clutching' is , but i dont think im doing it right. If anyone has
any step by step easy to understand explanations on how to 'double clutch, please share.....

 

[Rallsport]

This is not the only resource for information, most any search engine will provide results. Here are a couple for "ya"

http://www.driversedge.com/dblcltch.htm
http://www.triumphspitfire.com/Healtoe.html

 

[Defiant]

You're late, this usually comes up by Monday.

Here we go: you're heading down the road at 60. Your exit ramp looms. Instead of using the brakes to start slowing, you decide to use compression.
1.Press in the clutch
2.shift from 5th to neutral
3.Let out the clutch
4.goose the throttle just enough to bring the RPM up to where they'll be in 4th
5.before the energy has depleted from the flywheel, press in the clutch and slide into 4th.
6.let off the clutch.

When done properly, it's almost spooky how the gears engage. 5th to 4th is pretty much pointless, the gear spread isn't enough to matter much. You'll know you're good at it when you no longer get a crunch in going from 3rd to 2nd. 2nd to 1st shouldn't really be done, a DSM will pull from a stop in 2nd well enough.

To add in heel-and-toe, you do all this while on the brakes. Some actually do use their heel and toe, I've always had to roll my foot to the side to blip the throttle.

Now get the sandbags for the flood of "that's not what you do" "you don't need to with synchros" and "but XX said..."

No, in a perfect world the synchros would be strong enough to bring the mass of the gear clusters up to speed with one another without double-clutching. I've never found that gearbox, despite such things as Porsche's development of braking blocks and double-rings over the original Borg-Warner invention of simple tapered-bronze cones. Part of the trouble with the DSM box is how small it has to be to fit under the nose of the car- there just isn't enough meat in there to make the synchros strong enough to work for a long time. Motorcycle gearboxes won't let you double-clutch, because they're sequential: you don't go from 2 to N to 3, you go straight from 1 to 2 to 3 to 2 to 1. They don't have synchros, they have dog clutches instead of engagement rings. With them you just rev-match (also known as "double-kicking") to keep from breaking traction.

 

[Defiant]

And about that first link: yeh, leave it to an M5 "driver" to shift from 4th to 2nd. Well, I guess it takes that kind of mentality to pay that much for a car in the first place.

 

[Kicka$$93laser]

Thank you sooo much Defiant, your explanation was actually understandable to me!

 

[AWDadvantage]

If you really want to learn how to drive and shift for little money, buy Going Faster. It's a book by the Skip Barber Racing School and it has TONS of information. Not all of it applies to normal cars, but the techniques are valid nontheless.

Of course, real-life experience at a track day is for more valuable, but therefore also more costly.

 

[eyebrowski]

this thread has become way to confusing, i think people are mixing up shifting techniques. double clutching is not needed on any car with synchros, including our cars, we just do it for a smoother ride, more instant power, and to save the life of the tranny.

wancsta- what you have described is not double clutching. here is some reading material to help straighten this out.


http://www.driversedge.com/dblcltch.htm
http://www.g-speed.com/pbh/double-clutch.html

heel toe:
http://www.triumphspitfire.com/Healtoe.html