wise_1

i usually double clutch when i down-shift to launch from a cruise..
i've heard that some people double clutch when they are up-shifting? is this true? why double clutch when you up-shift??

thanx

droideka

From what I understand, you used to have to double de-clutch on upshifts in older cars that didn't have fully-synchronized forward gears. I can't see why you'd have to do so on modern cars, but a brilliantly executed double de-clutch downshift is a thing of beauty.

wise_1

oh... older cars w/o synchros...

well.. i guess that makes sense..

this is what i do when i down shift...

i depress the clutch to put the gear in the neutral...
then dump the clutch and floor accel while still in neutral...
then depress the clutch, down shift, and dump the cluch while flooring....

this gives a JOLT of power surge because the rpm is still high from double clutching when dumping the clutch at the lower gear..

correct??

NSANY

The extra step of putting the shifter in neutral is unneeded with fully-synchronized transmissions. Back in the day, this was used to ensure that the lay shaft was spinning at the correct RPM (as dictated by the engine RPM provided by the driver) before shifting to the next gear. With no synchros, you needed the extra step to avoid grinding the gearbox into powder.

A good summary of double clutching is here

wise_1

but if you want to launch from a cruise w/o getting a Jerk from dumping the clutch while flooring, this extra step helps...

this extra step ensures a fast pick-up while reducing the Jerking motion and maximizing the surge of power and pick-up...

wise_1

am i the only one doing this?
do you guys just down shift and floor??

Alang

iTrader: (1)

The release of the clutch between gears is unnecessary. Just rev match while the clutch is in before letting it back out again and you will get a smooth (and much faster) shift.

Double clutching is totally unnecessary in any situation with modern syncronized transmissions.

jeffw

It seems that you could potentially prolong the life of the synchros if you double-clutch, but I've heard many say it's just not worth it any more. Also, seen several flame wars get started with the double-clutch debate...

If you want to increase the lifespan of your tranny I think the best thing you could do is simply pause in neutral for half a second between shifts when you're not racing. Also, avoid power shifting.

As for avoiding the lurching on down shift, I try to rev match before letting the clutch out. But I do this after shifting. Am I doing this in the correct order? I figure if I rev-match before shifting then it would be a border-line power shift. Basically I do this:

1.) Lift gas, depress clutch at same time
2.) Shift (with or without pause in neutral depending on if I'm in a big hurry)
3.) Try to give gas to where I think the revs are for the selected gear and vehicle speed
4.) Release clutch and give slightly more gas as I release
--
Jeff

digerydingo

Why waste time double clutching when a nicely executed heel toe works just as good. Obviously you wouldn't touch the brake if you just want to drop gears for overtaking, but executing in one fluid motion, shifting, blipping and releasing the clutch, is much smoother and faster. Try double clutching through 6 gears with 2.5gs under heavy braking, not gonna happen my friend. I heel toe on all cars, old and new, syncros or no. It may take you an hour or so to get used to the nature of a new car and power band but you can usualy match engine speed very well after a short while and upshift and downshift faster then dumping the clutch in neutral.

jhchan

Double clutching is also good for when you're skipping gears on a down shift. Say you're comin in hot in 4th and want to go down to 2nd for a turn. This saves a lot of wear not to mention is smoother. Sorry guys I haven't mastered heel-toe in my lowly 2k Sentra SE.

Waiting for my Z...

frayed

Double clutching is a waste of time and effort with all modern cars having syncros.

Heel-Toe downshifting (aka, rev-matched downshifting) is important for maximum smoothness, which leads to faster laps on the track.

Paul Frere's book on Competition Driving has a great synopsis on heel toe shifting.

I heel toe on the track, and sometimes around town.

Here's a detailed analysis of double clutching:

http://integra.vtec.net/driving/dclutch.html

TheOne

i know this is a newbie question but what exactly is double clutching? when i drive stick i just downshift...please explain double clutch and double de-clutch...oh i did read the linkg but its too techincal to really understandthe idea of double clutching....

D'oh

I would really like to learn to heel-and-toe, and while I know the theory, I just can't seem to twist my foot around to reach both the brake and the gas. In my girlfriends Paseo the two pedals were close enough that I could place the ball of my foot on the brake, and roll the outside onto the gas, which worked pretty well. It the Z, the brake and gas are too far apart for me, so I need some pointers. How do you guys to it? The best I can do is get my heel on the brake and toe on the gas, but then my braking is totally jerky and everything goes to hell. Do I just need more practice, or have you found a better way to arrange your feet?

-D'oh!

Canadian350Z

Heel-toe..... mmmmmmmmm

Nothin like rippin through a corner and pulling it off correctly...

The power on exit.... you don't know what a car is supposed to feel like until you do it correctly....

Ayrton Senna wrote a book a while back too that explains it pretty good.... Bondurant explains it fairly well as well....

Cheers!

frayed

In cars with the pedals far apart, I've had to brake with the ball of my foot, leaving the heel at the base of the gas pedal. Your foot should make a 45 degree angle. Right before I let the clutch out, I stab my heel at the gas pedal. Your heel doesn't really hit the gas, but the outer side of my right foot.

Or, do as you have described, moving your whole foot over to the brake, and instead of rolling, use the ball of your foot as a pivot point on the brake pedal while nailing the gas with the heel of your foot (likely the heel won't make contact though, but the outside of your foot).

Both work but you will mess up your braking action at first. It takes a little while to do it consistently while not being jerky on the brakes.

Finally, it is much easier to do at speed, under heavy braking. In this situation, the car is not as sensitive to minor pedal pressure changes, and the pedal is generally further in its travel.