Double clutching is the technique where you quickly engage the clutch between shifts (in neutral). The purpose of this in downshifting (at the moment when you blip the throttle) is to spin up the clutch disk/input shaft assembly to match the flywheel/pressure plate and gearbox output shaft assemblies.

Double clutching is best used in "rev matching" when:

1) You are operating a gearbox that does not have sychros
2) You want the best possible matching with the least synchro wear possible

 

So EZ, double clutching is not completely useless as they say?

since it does help with synchro wear?

 

Absolutely not useless. It is *the* best way to downshift, period. Decreased synchro wear is an important factor of course...

 

You got that right, but these new drive by wire cars like porsche take the fun out of it, its impossible to get wrong , no matter how bad you are at rev matching it does it perfect for you everytime, atleast in the (997/987/GT) the older 996's and 986's from '01 on up were drive by wire but didnt synch the revs for you.

 

"Granny shiftin' not double clutchin' like you should."

 

And of course his statement does not apply to our discussion of downshifting

 

OK, so double clutching is not the same as heel-toe shifting. I use heel-toe all the time, but I've never double clutched. The sequence for heel-toe is (from 3rd to 2nd):

- apply brake
- depress clutch pedal
- while braking, blip gas with side of foot to rev match
- at the same time shift from 3rd to 2nd
- release clutch pedal
- release brake and accelerate out of turn

Now as I understand it, a double-clutch heel-toe shift is:
- apply brake
- depress clutch pedal
- shift into neutral
- blip gas with side of foot
- release clutch pedal
- depress clutch pedal
- shift from 3rd to 2nd
- blip gas with side of foot
- release clutch pedal
- release brake and accelerate out of turn

Of course, all of this is performed in a split second. My question is what does the extra blip of the gas do for you if you're already rev matching anyway in a heel-toe shift. What extra benefit does double-clutching give you on the downshift?

 

Close..

- apply brake
- depress clutch pedal
- shift into neutral
- release clutch pedal
- blip gas
- depress clutch pedal
- shift from 3rd to 2nd
- release clutch pedal
- release brake and accelerate out of turn

The difference is you are rev-matching while in neutral with the clutch engaged. This brings the transmission up to speed so the syncros don't have to do it.

 

haha I never understood that. why the hell would you double clutch during a drag race? hahaha

 

AH! I get it now! I'm going to have to go out and practice this for sure

 

What's the difference between double clutching and heel-and-toe since they both are used for rev-matching.

 

Well between this thread and the "Question about heel-toe" thread I thought we had this covered.

But just in case:

Heel-toe is using part of your foot on the brake pedal while simultaneously using another part of that foot to control the throttle pedal. The term originated from using the toes on the brakes while blipping the throttle with the heel.

Double-clutching is engaging the clutch during throttle blips in neutral so that the clutch disk and input shaft assemblies are brought up to a rotational speed matching the engine and output shaft assemblies. Using this technique keeps the car settled during downshifts and helps preserve the gearbox and synchros.

 

if paul walker had double clutched, the floorboard wouldn't have fallen off when pistons siezed.

 

Quick question, how was your friends dad teaching him how to double clutch but couldn't explain what he was teaching?

 

well, duhh... the dude's obviously full of ****...